Area fraction of large grains as a function of ECAP pass number.
\r\n\t
",isbn:"978-1-80356-357-2",printIsbn:"978-1-80356-356-5",pdfIsbn:"978-1-80356-358-9",doi:null,price:0,priceEur:0,priceUsd:0,slug:null,numberOfPages:0,isOpenForSubmission:!1,isSalesforceBook:!1,isNomenclature:!1,hash:"3aba1eb3600a8c9ff880c628f70b3298",bookSignature:"Ph.D. Delfín Ortega-Sánchez",publishedDate:null,coverURL:"https://cdn.intechopen.com/books/images_new/11481.jpg",keywords:"Integrated Curriculum, Transdisciplinarity, Integrated Active Learning, Educational Programs, Contemporary Social Problems, Critical Thinking, Creative Thinking, Social Thinking, Agenda 2030, Sustainable Development Goals, Educational Paradigm, Social Reality",numberOfDownloads:null,numberOfWosCitations:0,numberOfCrossrefCitations:null,numberOfDimensionsCitations:null,numberOfTotalCitations:null,isAvailableForWebshopOrdering:!0,dateEndFirstStepPublish:"February 18th 2022",dateEndSecondStepPublish:"March 18th 2022",dateEndThirdStepPublish:"May 17th 2022",dateEndFourthStepPublish:"August 5th 2022",dateEndFifthStepPublish:"October 4th 2022",dateConfirmationOfParticipation:null,remainingDaysToSecondStep:"2 months",secondStepPassed:!0,areRegistrationsClosed:!0,currentStepOfPublishingProcess:4,editedByType:null,kuFlag:!1,biosketch:"Internationally recognized researcher in the field of historical and social science education. Author of more than 100 publications, awarded three Doctorate degrees and the National End of Degree Award, granted by the Ministry of Education to the best academic records of Bachelor's degrees in Spain. Dr. Ortega-Sánchez has been Vice-Rector for Social Responsibility, Culture, and Sports at the University of Burgos since 2021.",coeditorOneBiosketch:null,coeditorTwoBiosketch:null,coeditorThreeBiosketch:null,coeditorFourBiosketch:null,coeditorFiveBiosketch:null,editors:[{id:"302925",title:"Ph.D.",name:"Delfín",middleName:null,surname:"Ortega-Sánchez",slug:"delfin-ortega-sanchez",fullName:"Delfín Ortega-Sánchez",profilePictureURL:"https://mts.intechopen.com/storage/users/302925/images/system/302925.jpg",biography:"I hold a PhD in Didactics of Social Sciences from the Autonomous University of Barcelona, a PhD in Educational Sciences from the University of Burgos, and a PhD in History from the University of Extremadura. My research interests focus on the construction of identities in the History and Geography teaching, gender mainstreaming in initial education and training for teachers, the didactic treatment of relevant social problems and controversial issues in the teaching of the social and human sciences, and the application of educational technology in the specific field of social sciences. I am currently a Social Sciences teacher and researcher at University of Burgos (Spain).",institutionString:"University of Burgos",position:null,outsideEditionCount:0,totalCites:0,totalAuthoredChapters:"1",totalChapterViews:"0",totalEditedBooks:"0",institution:{name:"University of Burgos",institutionURL:null,country:{name:"Spain"}}}],coeditorOne:null,coeditorTwo:null,coeditorThree:null,coeditorFour:null,coeditorFive:null,topics:[{id:"23",title:"Social Sciences",slug:"social-sciences"}],chapters:null,productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"},personalPublishingAssistant:{id:"429339",firstName:"Jelena",lastName:"Vrdoljak",middleName:null,title:"Ms.",imageUrl:"https://mts.intechopen.com/storage/users/429339/images/20012_n.jpg",email:"jelena.v@intechopen.com",biography:"As an Author Service Manager, my responsibilities include monitoring and facilitating all publishing activities for authors and editors. From chapter submission and review to approval and revision, copyediting and design, until final publication, I work closely with authors and editors to ensure a simple and easy publishing process. I maintain constant and effective communication with authors, editors and reviewers, which allows for a level of personal support that enables contributors to fully commit and concentrate on the chapters they are writing, editing, or reviewing. I assist authors in the preparation of their full chapter submissions and track important deadlines and ensure they are met. I help to coordinate internal processes such as linguistic review, and monitor the technical aspects of the process. As an ASM I am also involved in the acquisition of editors. Whether that be identifying an exceptional author and proposing an editorship collaboration, or contacting researchers who would like the opportunity to work with IntechOpen, I establish and help manage author and editor acquisition and contact."}},relatedBooks:[{type:"book",id:"6926",title:"Biological Anthropology",subtitle:"Applications and Case Studies",isOpenForSubmission:!1,hash:"5bbb192dffd37a257febf4acfde73bb8",slug:"biological-anthropology-applications-and-case-studies",bookSignature:"Alessio Vovlas",coverURL:"https://cdn.intechopen.com/books/images_new/6926.jpg",editedByType:"Edited by",editors:[{id:"313084",title:"Ph.D.",name:"Alessio",surname:"Vovlas",slug:"alessio-vovlas",fullName:"Alessio Vovlas"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"6942",title:"Global Social Work",subtitle:"Cutting Edge Issues and Critical Reflections",isOpenForSubmission:!1,hash:"222c8a66edfc7a4a6537af7565bcb3de",slug:"global-social-work-cutting-edge-issues-and-critical-reflections",bookSignature:"Bala Raju Nikku",coverURL:"https://cdn.intechopen.com/books/images_new/6942.jpg",editedByType:"Edited by",editors:[{id:"263576",title:"Dr.",name:"Bala",surname:"Nikku",slug:"bala-nikku",fullName:"Bala Nikku"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"1591",title:"Infrared Spectroscopy",subtitle:"Materials Science, Engineering and Technology",isOpenForSubmission:!1,hash:"99b4b7b71a8caeb693ed762b40b017f4",slug:"infrared-spectroscopy-materials-science-engineering-and-technology",bookSignature:"Theophile Theophanides",coverURL:"https://cdn.intechopen.com/books/images_new/1591.jpg",editedByType:"Edited by",editors:[{id:"37194",title:"Dr.",name:"Theophile",surname:"Theophanides",slug:"theophile-theophanides",fullName:"Theophile Theophanides"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"3161",title:"Frontiers in Guided Wave Optics and Optoelectronics",subtitle:null,isOpenForSubmission:!1,hash:"deb44e9c99f82bbce1083abea743146c",slug:"frontiers-in-guided-wave-optics-and-optoelectronics",bookSignature:"Bishnu Pal",coverURL:"https://cdn.intechopen.com/books/images_new/3161.jpg",editedByType:"Edited by",editors:[{id:"4782",title:"Prof.",name:"Bishnu",surname:"Pal",slug:"bishnu-pal",fullName:"Bishnu Pal"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"3092",title:"Anopheles mosquitoes",subtitle:"New insights into malaria vectors",isOpenForSubmission:!1,hash:"c9e622485316d5e296288bf24d2b0d64",slug:"anopheles-mosquitoes-new-insights-into-malaria-vectors",bookSignature:"Sylvie Manguin",coverURL:"https://cdn.intechopen.com/books/images_new/3092.jpg",editedByType:"Edited by",editors:[{id:"50017",title:"Prof.",name:"Sylvie",surname:"Manguin",slug:"sylvie-manguin",fullName:"Sylvie Manguin"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"371",title:"Abiotic Stress in Plants",subtitle:"Mechanisms and Adaptations",isOpenForSubmission:!1,hash:"588466f487e307619849d72389178a74",slug:"abiotic-stress-in-plants-mechanisms-and-adaptations",bookSignature:"Arun Shanker and B. Venkateswarlu",coverURL:"https://cdn.intechopen.com/books/images_new/371.jpg",editedByType:"Edited by",editors:[{id:"58592",title:"Dr.",name:"Arun",surname:"Shanker",slug:"arun-shanker",fullName:"Arun Shanker"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"72",title:"Ionic Liquids",subtitle:"Theory, Properties, New Approaches",isOpenForSubmission:!1,hash:"d94ffa3cfa10505e3b1d676d46fcd3f5",slug:"ionic-liquids-theory-properties-new-approaches",bookSignature:"Alexander Kokorin",coverURL:"https://cdn.intechopen.com/books/images_new/72.jpg",editedByType:"Edited by",editors:[{id:"19816",title:"Prof.",name:"Alexander",surname:"Kokorin",slug:"alexander-kokorin",fullName:"Alexander Kokorin"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"314",title:"Regenerative Medicine and Tissue Engineering",subtitle:"Cells and Biomaterials",isOpenForSubmission:!1,hash:"bb67e80e480c86bb8315458012d65686",slug:"regenerative-medicine-and-tissue-engineering-cells-and-biomaterials",bookSignature:"Daniel Eberli",coverURL:"https://cdn.intechopen.com/books/images_new/314.jpg",editedByType:"Edited by",editors:[{id:"6495",title:"Dr.",name:"Daniel",surname:"Eberli",slug:"daniel-eberli",fullName:"Daniel Eberli"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"57",title:"Physics and Applications of Graphene",subtitle:"Experiments",isOpenForSubmission:!1,hash:"0e6622a71cf4f02f45bfdd5691e1189a",slug:"physics-and-applications-of-graphene-experiments",bookSignature:"Sergey Mikhailov",coverURL:"https://cdn.intechopen.com/books/images_new/57.jpg",editedByType:"Edited by",editors:[{id:"16042",title:"Dr.",name:"Sergey",surname:"Mikhailov",slug:"sergey-mikhailov",fullName:"Sergey Mikhailov"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}},{type:"book",id:"1373",title:"Ionic Liquids",subtitle:"Applications and Perspectives",isOpenForSubmission:!1,hash:"5e9ae5ae9167cde4b344e499a792c41c",slug:"ionic-liquids-applications-and-perspectives",bookSignature:"Alexander Kokorin",coverURL:"https://cdn.intechopen.com/books/images_new/1373.jpg",editedByType:"Edited by",editors:[{id:"19816",title:"Prof.",name:"Alexander",surname:"Kokorin",slug:"alexander-kokorin",fullName:"Alexander Kokorin"}],productType:{id:"1",chapterContentType:"chapter",authoredCaption:"Edited by"}}]},chapter:{item:{type:"chapter",id:"49519",title:"Microstructure Evolution in Ultrafine-grained Magnesium Alloy AZ31 Processed by Severe Plastic Deformation",doi:"10.5772/61611",slug:"microstructure-evolution-in-ultrafine-grained-magnesium-alloy-az31-processed-by-severe-plastic-defor",body:'Due to its low density, magnesium alloys are very attractive materials for structural components in automotive, aerospace and other transport industries with the potential to replace steel or aluminium alloys in various applications [1]. Nevertheless, the use of magnesium alloys in more complex applications is limited because of the problems associated with poor corrosion and creep resistance and above all the low ductility. The limited ductility is a consequence of the hexagonal structure providing the lack of independent slip systems and the large difference in the values of the critical resolved shear stress in different slip systems. Moreover, the strong deformation textures and stress anisotropy in magnesium alloys reduces significantly the variety of possible industrial applications.
The mechanical and other essential properties determining the application of magnesium alloys may be improved by refining the grain size to the submicrocrystalline or even nanocrystalline level. In the last three decades, a variety of new techniques have been proposed for the production of the ultra-fine grain (UFG) structures in materials. The common feature of all these techniques is the imposition of large straining and consequent introduction of very high density of lattice defects in the material resulting in exceptional grain refinement. Since these procedures introduce severe plastic deformation (SPD) to bulk solids, it became convenient to describe all of them as SPD processing. Several processes of SPD are now available but only two of them receiving the most attention at present time, in particular, equal channel angular pressing (ECAP) and high-pressure torsion (HPT) [2–5].
The practical applications of the UFG materials are limited due to low microstructure stability at elevated temperatures that complicates the processing of final products. Thermal stability depends on many variables, such as stacking fault energy of the material, processing, or properties of grain boundaries [6]. Microstructure stability can be improved by various alloying elements or composite reinforcements.
In order to understand the microscopic mechanisms of grain fragmentation during SPD processing, detailed characterization of the microstructure is needed. The objective of this review paper is to employ a wide variety of standard and enhanced microscopic techniques to characterize the microstructure evolution of the UFG magnesium alloy AZ31 by employing several microscopic techniques, in particular, light microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), and a new sophisticated microscopic method—automated crystallographic orientation mapping in a TEM (ACOM-TEM).
The commercial magnesium alloy AZ31 (3 wt. % of Al, 0.8 wt. % of Zn, and 0.2 wt. % of Mn) was used in this investigation. Two most popular techniques of severe plastic deformation were employed for material processing and microstructure refinement, namely equal-channel angular pressing preceded by hot extrusion (EX-ECAP) and high-pressure torsion (HPT).
Equal-channel angular pressing (ECAP) is one of the most developed and also commercially used SPD procedures. ECAP was invented by Segal et al. in the 1970s and 1980s in the former Soviet Union [7]. Since its invention, ECAP has become well-known and widely used technique. Nowadays, ECAP is a commonly used SPD method applicable in many branches of industries. The main advantage of the ECAP technique is the same cross-sectional dimensions of the specimens before and after pressing. This fact allows repetitive pressing and the accumulation of strain in the specimen. Furthermore, the ECAP is a quite simple process commonly used worldwide.
The ECAP die consists of two channels with the same cross-section. Generally, the ECAP die is characterized by two angles:
The scheme of pressing of the rectangular sample with the square cross-section through the ECAP die a) with
The specimen pressed through the ECAP die is deformed by a simple shear in the intersection point of the channels. The imposed strain in each ECAP pass is dependent primarily upon the angle
High-pressure torsion (HPT) is another well-known SPD technique. In this method, the mechanical properties of a material are improved by a high pressure and concurrent torsional straining [9]. HPT was also for the first time applied to metals in the former Soviet Union in the 1980s [10]. The experimental setup of HPT is schematically illustrated in Figure 2.
The typical size of the disk-shaped sample varies from 10 to 20 mm in diameter and about 1 mm in thickness. A disk sample is placed between two anvils where it is subjected to a compressive pressure of several GPa. Simultaneously, one of the anvils rotates and the torsional strain is imposed to the sample.
Schematic of the HPT device showing the set-up, compression stage (stage I), and compression-torsion stage (stage II) [
The total strain imposed by HPT in the sample can be calculated by different approaches. The first widely used approach (Hencky/Eichinger) can be expressed by the logarithmic relation [12]:
where
where
However, the real strain generated in the workpiece during HPT may be different depending mainly on the die geometry and other factors. No unambiguous conclusion was adopted whether the Hencky or von Mises strain describes better the total strain imposed by HPT. Finite element method (FEM) may be employed to analyze the plastic deformation distribution in specimens processed by HPT. Several authors [14, 15] have used the FEM technique to determine the stress distribution and other parameters, e.g., the influence of the coefficient of friction, torque, etc. Recently, Lee et al. [13] employed a combined analysis of FEM and the model of dislocation cell evolution to describe the local deformation in specimen processed by HPT. The results of this study are shown in Figure 3.
FEM simulation of effective strain imposed by HPT. a) The effective strain distribution of the as compressed specimen (N=0), the specimens after 1/2 (N=1/2) and 1 turn (N=1). b) The effective strain distribution throughout the thickness of the specimens N=0, N=1/2, and N=1 in the top and mid-plane showing the comparison of the FEM simulations [
Prior to ECAP, the material was extruded at 350°C with an extrusion ratio of 22. ECAP pressing was performed at 180°C following route Bc, i.e., rotating the sample 90° between the individual passes, with the velocity of 50 mm/min. The angle
Prior to HPT, the material was homogenized at 390°C for 12 hours. After homogenization the disk specimens of the diameter of 19 mm and the thickness of 1-2 mm were cut from the billet. These specimens were processed by quasi-constrained HPT at room temperature for
The specimen surface for light microscopy observation needs to be plain, without impurities or scratches. Polypropylene was used for mounting the specimens for better manipulation. Mounted specimens were prepared by three consequent procedures: mechanical grinding, polishing, and etching. In the first step, the specimens were mechanically grinded on watered abrasive papers. Then the specimens were polished on a polishing disc with polishing suspension of grade 3 and 1 μm. Using this procedure, flat specimens with minimum surface scratches were obtained. Finally, the polished samples were etched by a diluted solution of picric acid. The time period of etching has to be optimized to attain the best possible visibility and no artefacts on the surface [16].
Electron backscatter diffraction (EBSD) is a microstructural crystallographic technique for determining crystallographic orientation. Texture, grain size and distribution, the misorientation and shape of individual grains, the types of grain boundaries, and many other microstructural features may be obtained from EBSD results.
The principle of the EBSD method is that the accelerated high-energy electrons interact with the atomic lattice of the crystalline material and form the so-called Kikuchi lines on the screen. The measurement is done automatically with a defined step. The formation of Kikuchi lines is caused by inelastic electron scattering. The inelastically scattered electron wavelength is slightly higher than the wavelength of elastically scattered electrons and the inelastic scattered electron intensity decreases with increasing scattering angle. In certain crystal orientations, some planes satisfy the Bragg condition (with diffraction angle
The SEM FEI Quanta 200 FX equipped with EDAX EBSD camera and OIM software was utilized for EBSD observations. A field emission gun (FEG) of a Schottky type was used as a source of electrons in the microscope. Beam voltage in the range from 500 V to 30 kV is applicable. The acceleration voltage employed was 10 kV.
The samples for EBSD investigation were first mechanically grinded on watered abrasive papers of grade 800, 1200, 2400, and 4000, respectively. Then the specimens were mechanically polished with diamond suspensions for water-sensitive materials of grade 3, 1, and ¼ μm, respectively. The final ion-polishing using a Gatan PIPS device was used to remove the surface layer influenced by polishing.
Transmission electron microscopy (TEM) is a technique that studies the local microstructure of the material using a beam of high-energy electrons. The specimens for TEM have to be very thin (≈ 100 nm depending on the acceleration voltage). An image is formed from the interaction of the electrons transmitted through the specimen and focused on a fluorescent screen or CCD camera.
The sample (thin foil) preparation consists of two steps: mechanical thinning and polishing. The type of polishing depends on the physical and chemical properties of the material.
The specimens of AZ31 alloy were first cut from the billet plane X (perpendicular to the extrusion direction) into slices of the thickness of approximately 1 mm. The slices were mechanically grinded from both sides to the thickness of 100 μm. The 3 mm diameter disks were cut out of the thin slices and dimpled from one side to the thickness of approximately 30 μm using the Gatan dimple grinder. This dimpling technique reduces electrolytic or ion polishing times and ensures that the ultra-thin area is done in the central part of the foil.
Ion polishing is used for materials that cannot be polished electrolytically. It is the case of many Mg alloys including AZ31. Ion polishing is a method of removing very fine quantities of the material. It uses an inert gas (argon) to generate a plasma stream that is emitted to the thinned area of the sample and removes the individual layers of the material. Acceleration energies vary usually from 2 to 4 keV. Ion beam always enters the sample. The penetration depth depends on the angle between the direction of the ion beam and the sample surface. The optimum conditions found for AZ31 were the following: acceleration voltage of 4 kV, angle of incidence of 4°, and room temperature. In the final stage the acceleration, voltage was reduced to 2 kV and the angle of incidence to 2°. The specimen preparation for TEM is finished when a small hole is formed in the foil and the surrounding area is thin enough to allow high-energy electrons to pass through the specimen. The schematic of the Precision Ion-Polishing System (PIPS) used for ion polishing is displayed in Figure 4 [17].
The microstructure observations were made with the TEM JEOL 2000FX at Charles University in Prague. The applied accelerated voltage was 200 kV.
Schematic illustration of Precision Ion-Polishing System (PIPS).
Automated crystallographic orientation mapping in a TEM (ACOM-TEM) is an effective technique for mapping phase and crystal orientation and an alternative to the well-known EBSD attachment SEM based on the Kikuchi lines. ACOM-TEM was first introduced by Schwarzer et al. [18]. This method of microstructural characterization represents a powerful tool especially for UFG or nano-grained materials where the limited resolution of SEM disallows EBSD scans. Its basic principle is similar to EBDS mapping—a selected area is scanned with defined step size and the electron diffraction patterns are collected using an external CCD camera. Off-line, every diffraction pattern is compared to the pre-calculated template and the best match is selected. The main difference with respect to EBSD is that point diffraction patterns are analyzed instead of Kikuchi lines, which significantly increases the precision of orientation determination. This type of ACOM-TEM device was developed in Grenoble by E. Rauch et al. [19, 20].
The experimental measurements were carried out using a TEM Philips CM200 equipped with a LaB6 gun at 200 kV at Université Libre de Bruxelles in Belgium. For the data treatment, TSL OIM Analysis 5 was used.
The limited resolution of light microscopy allows to perform only overview images with no structure details. Typical examples of microstructure evolution of extruded specimen and the specimens processed by different number of ECAP passes (N) are shown in Figure 5. The extruded sample microstructure shown in Figure 5a consists of two types of grains—several large grains surrounded by many small grains. The microstructure developed only slightly after the first and the second ECAP pass, the bimodal structure is still observed (see Figure 5b). The microstructure changes begin to be significant in light microscopy after 4 ECAP passes. One can see in Figure 5c that the large grains become smaller. However, the bimodal structure is not observed after 8 and 12 ECAP passes. The homogeneous microstructure of sample after 12 ECAP passes is shown in Figure 5d.
The microstructure of the extruded and ECAPed AZ31 alloy.
Figure 6 shows the microstructure and texture of the extruded AZ31 alloy. The EBSD inverse pole figure map is in the extrusion direction (ED). The microstructure of the initial extruded bar (0P) consists of large grains of 50–100 ≈m mixed with relatively fine grains of 2–5 μm. Most grains have their crystallographic c-axis perpendicular to the extrusion direction (ED), i.e., <10.0> axes parallel to the ED, which is typically found after extrusion of Mg alloys [21].
(a) EBSD orientation map and (b) recalculated pole figures of the extruded bar (0P), measured at the cross-section transverse to the extrusion direction (contour level = 1, 2,...10).
Figure 7 presents the microstructure and texture of the sample after 1 ECAP pass (1P). EBSD measurements were carried out at the mid-part of the cross-section of the billet. Sample coordinate system, i.e., X–Y–Z directions, which is used for representing the texture are illustrated in Figure 7d.
As shown in Figure 7a, the bimodal distribution of grain sizes is still observed in the 1P sample. A new texture component that corresponds to the basal poles rotated about 40° from the initial orientation towards the pressing direction is visible in the 1P sample, Figure 7b. The mentioned orientation change, however, is observed mainly in large grains (grain size> 10 μm). Figure 7c presents the (0001) pole figure of grains smaller than 3 μm in the 1P sample. The intensity of the tilted basal poles is rather weak compared to the pole figure constructed using all grains. Moreover, the small grains (< 3 μm) with the tilted basal pole are found mainly in neighboring areas around large grains.
These results regarding distinct textures depending on the grain sizes indicate that the shear strain by the first ECAP pass is mainly accommodated within the large grains in accordance with the Hall–Petch relation. The discontinuity of material flow caused by the inhomogeneous deformation seems to be compensated by the occurrence of the dynamic recrystallization in the vicinity of grain boundaries of large grains, such that the sample could be deformed without failure.
(a) EBSD orientation map of the sample after 1 ECAP pass, (b) (0001) pole figure calculated using all grains, (c) (0001) pole figure of grains smaller than 3 μm, and (d) the scheme of the geometry of specimens for EBSD measurements (contour level = 1, 2,... 10).
Microstructural features of the sample after 2 ECAP passes (not shown here) are very similar to those after 1 ECAP pass, i.e., the bimodal distribution of grain sizes and the orientation change in large grains remain almost unchanged.
The amount of large grains decreases significantly after 4 ECAP passes (4P), and their size becomes smaller when compared to the initial and the 1P samples (see Figure 8). As shown in Figure 8a with dashed circles, the fine grains usually surround large grains. Unlike the 1P sample, the fine grains (<3 μm) have mainly the orientation of the rotated basal poles in the 4P sample (Figure 8c). It is clear that the texture heterogeneity depending on the grain size disappears after 4 ECAP passes, compared pole figures evaluated from the whole area of the EBSD measurement to that from fine grains, Figure 8b and c, respectively.
(a) EBSD orientation map of the sample after 4 ECAP passes, (b)(0001) pole figure of all grains, and (c) grains smaller than 3 μm (contour level = 1, 2,... 10).
The microstructure and the texture of the sample after 12 ECAP passes (12P) are presented in Figure 9. The 12P sample shows the homogeneous distribution of fine, almost equiaxed grains, i.e., no large grains are visible. Figure 9a shows grain agglomerates with different colors distributed along a diagonal line. This indicates the heterogeneity in texture depending on the locations. This texture inhomogeneity can be understood as a result of non-uniform deformation along the ECAP billet after multiple passes [22]. Though the heterogeneous texture is visible, the fraction of the grains relating to the inhomogeneity is small such that the main texture component is found at the rotated basal pole, Figure 9b.
(a) EBSD orientation map and (b) (0001) pole figure of the sample after 12 ECAP passes (contour level = 1, 2,... 15).
Figure 10 displays size distributions of fine grains (< 10 μm) after different numbers of ECAP passes. The variation in the area fraction of large grains (>10 μm) is shown in Table 1. Grains smaller than 3 μm present in the extruded sample (0P) become finer (μ 1 lm) after the first ECAP pass. In subsequent ECAP passes no significant change in the size distribution in the range of the relatively fine grains is observed, while the area fraction of grains larger than 10 ≈m decreases gradually with ECAP passes, see Table 1.
Grain size distributions within the range up to 10 μm and the area fraction of the grains larger than 10 µm as a function of the ECAP pass number.
\n\t\t\t\t | \n\t\t\t0 | \n\t\t\t1 | \n\t\t\t2 | \n\t\t\t4 | \n\t\t\t8 | \n\t\t
\n\t\t\t\t | \n\t\t\t17.9% | \n\t\t\t18.1% | \n\t\t\t7.9% | \n\t\t\t2.8% | \n\t\t\tNone | \n\t\t
Area fraction of large grains as a function of ECAP pass number.
The variation in the fraction of low-angle boundaries (misorientation angle < 15°, LAGB) and high-angle boundaries (misorientation angle > 15°, HAGB) as a function of the ECAP pass number is shown in Figure 11. The LAGB fraction increases after 1 ECAP pass to μ 50%, and is significantly reduced (≈20%) after two ECAP passes and remains almost unchanged as the number of passes increases above 2. This stabilization of the HAGB formed by 2 ECAP passes indicates that the dislocations generated by ECAP did not reach the level necessary for the formation of dislocation in the cell-structure and further development of HAGB. Since the ECAP in this study was carried out at moderate temperature, the dislocation annihilation process by dynamic recovery occurred fast enough such that the grains could not be further refined after 2 ECAP passes.
Variation of fraction of the HAGB and LAGB as functions of the ECAP pass number.
Additional detailed observations using TEM broadened the EBSD research. The samples for TEM observations were cut perpendicular to the pressing direction from the EX-ECAPed billet and prepared by mechanical grinding, dimpling, and ion polishing. The microstructure of extruded samples is bimodal—consists of large grains of 50–100 μm mixed with relatively fine grains of 2–5 μm. Figure 12 shows the area with smaller grains of the average size of few μm. Typical twins are clearly seen in several grains. The (0001) basal texture of individual grains in extruded magnesium alloy observed in EBSD measurements was confirmed by electron diffraction analysis. The contrast of individual grains on this micrograph with typical low-angle grain boundaries confirmed the analysis of diffraction patterns. The area of larger grains had a typical heavily deformed structure with high density of tangled dislocations (not shown here).
Transmission electron micrograph of extruded AZ31 alloy.
Figure 13 presents the microstructure of the specimen after 1 EX-ECAP pass. The bimodal character of the microstructure did not change after the first ECAP pass; the average grain size is only slightly smaller in comparison with the extruded material, see Figure 13a. However, one significant difference between these two micrographs is observed, namely the character of grain boundaries. One can see many high-angle grain boundaries with typical thickness fringe band contrast confirming their almost equilibrium state in this micrograph. On the other hand, several grain boundaries remained in a non-equilibrium state with diffuse fuzzy contrast and many dislocations lying in a grain boundary plane were also observed. Several areas with high density of tangled dislocations with no or only exceptional signs of substructure formation were found in this specimen, see Figure 13b.
Transmission electron micrographs of AZ31 alloy after extrusion and 1 pass of ECAP, (a) equilibrium and HAGB region and (b) nonequilibrium GB region.
Subsequent TEM observation confirmed that the microstructure of EX-ECAPed samples changed only partly with increasing number of ECAP passes—fine grains were refined only slightly while the large grain zones were refined significantly. Typical microstructure of the sample processed by 2 EX-ECAP passes is shown in Figure 14.
Transmission electron micrograph of AZ31 alloy after extrusion and 2 passes of ECAP.
Only fine grains of the average grain size in the submicrometer range were observed in the micrographs of the specimens after 8 and 12 ECAP passes. Figure 15a presents the typical microstructure of the sample after 8 passes. One can see that the grains in this micrograph are equiaxed, and the grain size is approximately 800 nm. This material has significantly lower density of dislocations and equilibrium grains boundaries. A few newly recrystallized very small grains with no dislocations and sharp equilibrium boundaries were also found in the microstructure after 8 and 12 passes of ECAP as seen in Figure 15b. TEM observations confirm the process of microstructure evolution and its fragmentation as observed by EBSD. In particular, large grains were continuously refined during subsequent ECAP pressing while the fine grains remained almost unchanged.
Transmission electron micrograph of the AZ31 alloy (a) after 8 passes of EX-ECAP and (b) newly recrystallized small grains after 12 passes of EX-ECAP.
Microscopic techniques, in particular EBSD, can also contribute to the characterization of thermal stability of the UFG structure. The maintenance of the fine-grained structure is of particular importance for many physical properties, e.g., the superplasticity, etc. [23, 24].
Series of specimens for thermal stability investigation were prepared by isochronal annealing at the temperatures 150–500°C for 1 h followed by water-quench. The samples after extrusion and 4 passes of ECAP were chosen as suitable materials because of their UFG and homogeneous microstructure with relatively high dislocation density (see also Figure 8a).
The microstructure and grain size distribution of the specimen in the initial non-annealed condition after extrusion and 4 passes of ECAP are shown in Figure 16a and 16b, respectively. The microstructure is homogeneous comprising of very fine grains with an average size of 0.9 µm. The microstructure and grain sizes of the samples after 1 h of isochronal annealing at 150°C and 170°C (not shown here) are very similar to the non-annealed specimen.
Microstructure of the AZ31 sample after extrusion and 4 passes of ECAP, (a) inverse pole figure map and (b) grain size distribution.
Inhomogeneous grain growth is observed at higher annealing temperatures as displayed at Figure 17. Some grains start to grow at temperatures of 190°C (Figure 17a) and 210°C (not shown here). The fraction of coarse grains increases with increasing annealing temperature. At the temperature of 250°C, some areas with original fine grains are still observed, see Figure 17b. However, the small grains are continuously disappearing at higher annealing temperatures and nearly no small grains are observed after annealing at 400°C, see Figure 17e. Please note that magnification of Figure 17d and 17e is two times smaller than the magnification of the previous inverse pole figure maps; simultaneously, four times bigger area of the sample (100 × 100 µm) is depicted in Figure 17d and 17e. Microstructure of the specimens annealed at 450°C and 500°C was observed by light microscope and is displayed in Figure 18.
Microstructure of the AZ31 EX-ECAP specimen after 1 h of isochronal annealing at (a) 190°C, (b) 250°C, (c) 300°C, (d) 350°C, and (e) 400°C (EBSD inverse pole figure maps).
Microstructure of the AZ31 EX-ECAP specimen after 1 h of isochronal annealing at (a) 450°C and (b) 500 °C (light microscope images).
Grain size distribution and average grain size of the samples studied by EBSD were calculated from data measured in the area 100 × 100 μm for all annealing temperatures to achieve better statistics. Statistical values from the samples studied by light microscopy were calculated from two or more images in order to get more than 1000 grains for each sample. Grains intersecting the edge of EBSD maps and light microscopy images were not included in the analysis. The dependence of average grain size (number average) on annealing temperature is plotted in Figure 19. In samples annealed at 250°C and 300°C, the average values were calculated from the bimodal grain size distribution. The values of the average grain sizes are summarized in Table 2.
Dependence of the average grain size (number average, excluding twins) of the EX-ECAP AZ31 alloy on annealing temperature after 1 h of isochronal annealing process.
\n\t\t\t\t \n\t\t\t\t | \n\t\t\t- | \n\t\t\t170 | \n\t\t\t190 | \n\t\t\t210 | \n\t\t\t250 | \n\t\t\t300 | \n\t\t\t350 | \n\t\t\t400 | \n\t\t\t450 | \n\t\t\t500 | \n\t\t
\n\t\t\t\t \n\t\t\t\t | \n\t\t\t0.94 | \n\t\t\t0.99 | \n\t\t\t1.05 | \n\t\t\t1.48 | \n\t\t\t1.83 | \n\t\t\t2.06 | \n\t\t\t3.04 | \n\t\t\t3.79 | \n\t\t\t10.09 | \n\t\t\t24.53 | \n\t\t
The average grain sizes at different annealing temperatures.
Annealing twins observed after annealing at 250–400°C (see Figures 17b and 17e) were excluded from grain size calculations to achieve true grain size values (twin boundaries were ignored in grain size calculations, i.e., the twin is considered to be a part of the grain). All these twins were determined as the tensile twins with misorientation angle of 86° [25]. Twin fractions, fraction of twinned grains and the area fraction of twinned grains in samples after annealing at
\n\t\t\t\t | \n\t\t\t250°C | \n\t\t\t300°C | \n\t\t\t350°C | \n\t\t\t400°C | \n\t\t
\n\t\t\t\t | \n\t\t\t0.13 | \n\t\t\t0.12 | \n\t\t\t0.16 | \n\t\t\t0.14 | \n\t\t
\n\t\t\t\t | \n\t\t\t0.26 | \n\t\t\t0.26 | \n\t\t\t0.37 | \n\t\t\t0.40 | \n\t\t
\n\t\t\t\t | \n\t\t\t0.55 | \n\t\t\t0.52 | \n\t\t\t0.60 | \n\t\t\t0.71 | \n\t\t
Twinning in isochronally annealed EX-ECAP AZ31 alloy.
The microstructure of the materials after SPD cannot be often observed by light microscopy because of their very small grain sizes. EBSD is usually a much better and suitable method in this case. However, even EBSD has some limitation in resolution or some “more local” method could be required for microstructure observations. This often occurs in specimens processed by high pressure torsion. This method proved to be more effective in grain refinement than the ECAP due to mainly much larger strains imposed on the HPT disk during processing and also lower temperatures of processing as compared to ECAP [2, 9]. TEM is a well-known technique that usually solves the problem. ACOM-TEM is a very sophisticated method, alternative to EBSD, which enables to study extremely fine-grained materials. We used this technique for microstructure observations of the most deformed parts of HPT specimens. Due to the inhomogeneous character of strain imposed to the material by HPT, disks processed by HPT could be divided into three parts: center, middle, and periphery (see Figure 20).
Schematic illustration of three different parts of the disks processed by HPT.
Due to relatively low imposed strain after one HPT rotation, EBSD is sufficient to be employed for microstructure observation. Figures 21a and 21b show deformed microstructures of the central and middle parts of the specimen after 1 turn studied by EBSD. The areas investigated by EBSD could be relatively big—in our case it was the area 100 × 100 μm. The step size of these measurements was 100 nm. Figure 21a displays a heavily deformed microstructure of the central part of the specimen with a lot of multiple twinning. The microstructure of the middle part of the sample after 1 HPT rotation, shown in Figure 21b, consists of several large elongated grains with no twins and a lot of new grains of the average size of few microns.
The same middle part of this specimen was studied using ACOM-TEM and the typical results are displayed in Figure 22a. Measurements were done with step size 20 nm, which is five times smaller than the step size of the EBSD measurements. ACOM-TEM measurements confirmed heterogeneous microstructures with large elongated grains and a lot of small grains. The microstructure of the peripheral part (see Figure 22b) is homogeneous with very small grains only (≈ 100–300 nm).
EBSD IPF image of microstructure of the AZ31 sample after 1 turn of HPT, (a) central part and (b) middle part.
ACOM-TEM image of the microstructure of the AZ31 sample after 1 turn of HPT, (a) middle part and (b) periphery.
The sample, after 5 turns of HPT, was investigated using ACOM-TEM in the middle and the peripheral part of the disk. The microstructure of the middle part (see Figure 23a) is comparable with the middle part of the sample after 1 HPT rotation; it consists of large elongated deformed grains and a lot of small grains surrounding the bigger grains. The microstructure of the peripheral part of the disk after 5 HPT turns, shown in Figure 23b, is composed mainly of very small grains. However, few remaining grains with the size of several microns could be still observed in the peripheral part. The ACOM-TEM is a very local method where the relatively small part of a thin foil could be investigated. Thus, the statistics of measurements of heterogeneous microstructure is not sufficient. Preparation and investigation of more TEM foils is needed to improve the statistics (despite each image consisting of observations at four different zones of a foil).
ACOM-TEM image of the microstructure of the AZ31 sample after 5 turns of HPT, (a) middle part and (b) periphery.
Figures 24a and 24b display the microstructure of the middle and peripheral part of the disk after 15 HPT rotations, respectively. The microstructure of both parts is more homogeneous than the microstructure of the same parts of the disk after 5 HPT turns.
ACOM-TEM image of the microstructure of the AZ31 sample after 15 turns of HPT, (a) middle part and (b) periphery.
Grain size distributions of extremely fine grained microstructure of the peripheral parts of the disks after 1 and 15 HPT rotations (see Figure 25) show that about 60%, and nearly 70%, of grains, respectively, have a diameter of 100–200 nm that proves clearly the efficiency of grain refinement by HPT.
Grain size distribution of the peripheral part of the disk after (a) 1 and (b) 15 rotations of HPT.
Microstructure evolution in ultra-fine grained magnesium alloy AZ31 prepared by severe plastic deformation was investigated by several experimental techniques. The following conclusions may be drawn from this investigation:
Due to limited resolution light microscopy may be employed to investigate the initial stages of grain fragmentation, i.e., the specimens processed by low number of ECAP passes or low number of HPT turns and especially in zones around the disk centers;
EBSD proved to be a very powerful technique for the investigation of various stages of grain refinement. It allows to characterize not only the grain fragmentation, but also to determine other microstructural features as the grain size distribution and the grain boundary character distribution (the fraction of LAGBS vs. HAGBs), as well as the texture evolution with strain imposed to the material by ECAP and/or HPT;
TEM allows to characterize the details of the microstructure, namely the dislocation arrangements, grain boundary character (equilibrium vs. nonequilibrium grain boundaries), twins, twin and other special boundaries, etc.;
The special technique of ACOM-TEM may be used to characterize the terminal stages of grain refinement (saturation) with grain sizes approaching to nanometer range (grain size < 100 nm), which is typical for peripheral zones of specimens processed by multiple turns of HPT;
Complex microstructure characterization by different techniques of electron microscopy allows to understand the microscopic mechanisms of grain refinement, grain fragmentation, structure stability, as well as other important properties of ultra-fine grained materials processed by severe plastic deformation.
This work was financially supported by the Czech Science Foundation under the project GB14-36566G.
The global annual production of shrimp is nearly 4 million tons generating almost half of this weight in waste. This waste in turn, is composed of chitin, which forms microfibrillar arrangements embedded in a protein matrix with CaCO3. A green alternative for the use of this waste is to use it as an organic fertilizer in form of pellets or as a hydrolyzed material. The search for new organic fertilizers is important due to the limited availability of manure and compost in coast lines resulting promising the use of shrimp waste as an alternative organic fertilizer for crops. Currently, there is no information regarding the organic cultivation of legumes fertilized with shrimp-based waste.
A rapid and efficient shrimp waste hydrolysis could be accomplished by microwaves, which are non-ionizing electromagnetic radiation having wavelengths from 1 mm to 1 m corresponding to frequencies from 300 GHz to 300 MHz, respectively. This radiation could provide the energy required to break the chemical bonds found in organic molecules such as C-C bonds (347 kJ/mol), and hydrogen bonds such those found in the lignocellulosic biomass of rice straw (3.9–10.1 kJ/mol) rendering a 5-fold increase in the yield of sugars [1].
Leguminous crops have been used for several centuries as a source of food for humans and animals [2]. These plants are originated from the Americas but they are now cultivated all over the world due to their high nutritional and culinary values. In fact, they contain high amounts of protein, vitamins (i.e., thiamine, pyridoxine, and folic acid), dietary fiber, complex carbohydrates (i.e., starch), and nutrients such as iron, potassium, phosphorous, selenium, molybdenum and calcium. They are highly desirable in the human diet since are low in sodium and calories [3]. Further, legumes are so important for human nutrition that ∼12 million tons of
The growth and development of legumes would require appropriate quantities of nutrients for their optimal development; otherwise, physiological deficiency symptoms could occur [4]. Nowadays, the current trend is the use of organic fertilizers for optimal vegetable development. However, the heterogeneity of the physical and chemical characteristics of the different organic fertilizers may give rise to different crop yields. Interestingly, legumes are known to be nitrogen fixers as they take nitrogen from the air by demand and release it into the soil, fulfilling their own nitrogen needs. This implies the need for an organic fertilizer which provides low levels of nitrogen accordingly [5]. For this reason, the intense use of chemical fertilizers for plant development is not advisable since it causes depletion of beneficial soil microbiota and potential pollution of soil and water [6].
Nowadays, organic fertilizers derived from worm castings, peat, manure, and poultry guano have been used to obtain an efficient organic crop production of several plant species [7]. They increase the organic matter and microorganism activity, improve porosity, water retention, and ion exchange capabilities of the soil. They also prevent root burning or destruction of soil microflora since they contain amino acids, organic matter and a variety of micronutrients that replenish the nutrient level of the soil and feeding important soil microorganisms [8]. For instance, the application of vermicompost in soil decreases root rot of beans and produces vigorous plants [9].
The main objective of the current study was to compare the physical characteristics of several shrimp-based fertilizers and their microwave-assisted hydrolyzates on the development of leguminous plants treated with these fertilizers under greenhouse conditions following an organic production. Fertility and substrate management in organic greenhouse production is important in short-term, low fertility requiring crops. Developing organic fertilizers that slowly release nutrients could improve the crop management of legumes produced organically in container production systems.
Dry shrimp exoskeletons were obtained from the pacific coast of Tumaco (Colombia), milled on a cutting mill (Model 3, Willey Arthur Thomas Co., Philadelphia, USA), and passed through a # 100 mesh sieve. This material was labeled as F0. In a separate experimental set, pellets were produced using microcrystalline cellulose (MCC) as a pelletization aid. Thus, pellets made of pure MCC were made by wetting ∼20 g of MCC with 20 mL of distilled water and passed through a #16 mesh sieve (1190 μm size) with a force ≤11.2 N/cm2 measured with a load cell (LCGD-10 K, Omega Engineering, Inc., Stamford, CT). The extruded thus obtained was put in the spheronizer chamber (Model 1LA70-4YA60, Siemens), which was operated at the spheronization rate of 15 Hz and spheronization time of 120 s producing beads, which were then oven-dried at 40°C for 24 h. These pellets were then labeled as FPC. In another experimental set, a 50:50 mixture of raw waste and MCC was wetted with 42.5 mL of water and submitted to spheronization under the same conditions as explained for the raw MCC. These pellets were labeled as FPE. On the other hand, a hydrolyzed shrimp waste was obtained using a focused microwave apparatus (Samsung, Model MW 630 WA). A 10% power was applied to ensure reproducibility. Approximately, 20 g of sample was dispersed in 200 mL of a 5% NaOH solution and submitted to a refluxing action keeping the temperature between 50 and 60°C. Radiation was continued for the selected exposure times of 0.85 h so a hydrolysis degree of 42% was obtained. The hydrolyzed product was then cooled down, neutralized with 1 N HCl, filtered and dried at 60°C for 24 h. Further, pellets of this material were made under the same conditions employed for FPE and labeled as FHPE.
The physicochemical and functional properties of these pellets were compared to those of the untreated soil substrate (SS), untreated cotton substrate (CS) and two commercial fertilizers named as CF1 and CF2. SS was obtained from a local farm and contained a mixture of virgin soil (fine loam) and rice husk at a 3:2 ratio. CF1 and CF2 (N-P-K of 13.2-1-0) corresponded to an organic and extruded synthetic fertilizer, respectively.
The greenhouse study was conducted in a non-temperature controlled agricultural research station near Medellin (lat. 6.12° N, long. −75.54° E, altitude 2550 m) having a 4 × 4 m (width × length) greenhouse surrounded by a 10-mm light diffusive template glass. The growing condition in the greenhouse was a mean temperature of 23°C day/15°C night and from 65 to 85% RH as recorded during the growth season. No supplementary light or heating was applied in the greenhouse station.
The soil used in the study was a mixture of fine loam (taken from 0 to 30 cm of a virgin soil) and rice husk at a 3:2 ratio. The soil was put in 2 kg PVC pots (15 cm diameter). Healthy and mature legume seeds were obtained from a retail center of Medellin. Subsequently, one seed was sown in each pot randomly and irrigated uniformly with tap water. A plastic saucer was placed under each pot to prevent water loss by leaching. The plants were irrigated using one dripper per plant (at a discharging rate of 10 mL/h) and the total daily irrigation during the growing season ranged from 240 to 350 mL/plant. The irrigation volume ensured that soil was maintained wet in the growing medium.
After germination, only vigorous seedlings were selected for growth in each pot. Five replications of each treatment were arranged in a completely randomized design. The germinated seeds were then treated with ∼4 g of the fertilizers in three amendments and these treatments were started on 1-week-old legume seedlings that emerged from direct seeding [12 d after direct seeding (DADS)]. Four and eight weeks after direct seeding, a second and third treatment was applied, whereas in the control treatments, no fertilizer was added (water only). The composition and physical properties of the fertilizers are listed in Table 1. Legume plants were trained to a single vertical pole around the main stem and fixed to a wooden stick having 1.5 m high from the ground to support the plant. There was no need to apply pesticides to control insects since plants were healthy and developed normally.
Sample | MC (%) | Sugars (mg/g) | pH | ε (%) | Prot (%) | Ash (%) | CHO (%) | ξ (mV) | BD (g/cm3) | Soil con (μS/cm) | Soil pH | IE (meq/g) | Con (μS/cm) | Water sorption parameters (Young-Nelson model) | ||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
A (10−4) | B | E | ΔH (kJ/mol) | r2 | ||||||||||||||
F0 | *11.0 ± 0.3 | *29.5 ± 0.1 | *8.3 ± 0.2 | *81.8 ± 0.0 | *3.20 ± 0.16 | *3.6 ± 0.37 | 90.3 ± 0.31 | −15 ± 0.5 | *0.32 ± 0.01 | 20.9 ± 3.4 | 6.7 ± 0.2 | 0.81 ± 0.14 | *210 ± 4.4 | 1.63 | 0.20 | 16.41 | −6.94 | 0.9668 |
FPC | 2.5 ± 1.1 | 0.0 ± 0.0 | *5.0 ± 0.1 | *48 ± 0.0 | 0.0 ± 0.0 | 0.05 ± 0.01 | *98 ± 1 | −16.4 ± 0.5 | 0.89 ± 0.0 | 20.6 ± 2.6 | 7.1 ± 0.2 | 0.26 ± 0.03 | 53.8 ± 2.1 | 13.3 | 0.14 | 6.50 | −4.64 | 0.9593 |
FPE | 3.5 ± 1.2 | *10.5 ± 0.1 | *8.5 ± 0.1 | 62 ± 0.0 | *1.2 ± 0.12 | 1.7 ± 0.3 | *94 ± 1 | −11.9 ± 1.6* | 0.57 ± 0.02 | *27.6 ± 2.5 | 7.0 ± 0.2 | 0.33 ± 0.03 | *280.7 ± 1.6 | 99 | 0.11 | 5.36 | −2.70 | 0.9800 |
FHPE | 4.2 ± 1.3 | 0.002 ± 0.000 | *8.5 ± 0.2 | 66 ± 0.0 | 0.0 ± 0.0 | 1.5 ± 0.4 | 90 ± 0.9 | −9.4 ± 0.5* | 0.51 ± 0.02 | 18.4 ± 2.7 | 7.1 ± 0.2 | 0.34 ± 0.01 | *142.3 ± 0.6 | 4.9 | 0.02 | 0.90 | 0.27 | 0.9826 |
SS | *44 ± 1.3 | 0.002 ± 0.000 | 7.2 ± 0.4 | *83.3 ± 0.0 | *9.41 ± 0.43 | *45.4 ± 1.3 | *0.6 ± 0.1 | −22.1 ± 0.3 | *0.20 ± 0.02 | 16.4 ± 8.4 | 6.9 ± 0.1 | 0.67 ± 0.1 | 40.1 ± 3.1 | 3.11 | 0.61 | 46.09 | −9.50 | 0.9582 |
CS | *8.5 ± 0.6 | 0.0 ± 0.0 | 7.1 ± 0.2 | *89.8 ± 2.1 | 0.0 ± 0.0 | 0.05 ± 0.01 | *98 ± 1 | −21 ± 2.6 | *0.15 ± 0.03 | *35.3 ± 3.2 | 7.2 ± 0.1 | *2.21 ± 0.51 | *79.8 ± 2.2 | 0.423 | 0.34 | 24.13 | −7.89 | 0.9888 |
CF1 | *8.3 ± 0.5 | 0.002 ± 0.000 | 6.7 ± 0.2 | 58.3 ± 3 | 0.0 ± 0.0 | *42.8 ± 0.40 | *20.2 ± 1.2 | −17.8 ± 4.6 | *0.58 ± 0.02 | 10 ± 5.4 | 6.9 ± 0.2 | 0.41 ± 0.12 | *459 ± 2.8 | −0.81 | 0.28 | 10.69 | −5.87 | 0.9941 |
CF2 | 5.8 ± 0.3 | 0.001 ± 0.000 | 6.7 ± 0.2 | *70.3 ± 2.1 | 0.0 ± 0.0 | *5.3 ± 0.3 | *10 ± 2 | −22.9 ± 5.2 | *0.51 ± 0.02 | 12.5 ± 2.5 | 6.8 ± 0.2 | *9.49 ± 3.1 | *704 ± 3.7 | −19 | 0.63 | 4.64 | −3.81 | 0.9902 |
0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.05 | 0.00 | 0.00 | NA | NA | NA | NA | NA |
Physical properties of shrimp-based fertilizers, substrates and commercial fertilizers.
MC, moisture content; Prot, proteins; CHO, carbohydrates; Con, conductivity; BD, bulk density; ε, porosity; ξ, zeta potential; FPC, cellulose pellets; FPE, exoskeleton pellets; FHPE, hydrolyzed exoskeleton pellets; SS, soil substrate; CS, cotton substrate; IE, ionic exchange; F0, raw waste; CF1 and CF2 correspond to the commercial fertilizers; A and B correspond to the fraction of adsorbed and absorbed water in the particle, respectively; E, equilibrium constant between the mono layer and liquid water; ΔH, heat of sorption. NA, not applicable; mean values with an asterisk within the column are significantly different according to the Tukey’s test at
Plant height was evaluated on a monthly basis during the crop cycle. Harvesting started at 90 DADS and finished at 110 DADS. Legume plants were harvested twice a week when the pots reached maturity. Yield parameters that were measured for crop performance included pod length, pod mass, seed mass and pod number. The soil samples for chemical and microbiological analyses were collected from the surface layer (0–10 cm).
The pH of the 1% w/v fertilizer dispersion was measured with a handheld combo electrical conductivity (EC) and pH meter (EC600, Extech Instruments, Melrose, MA, USA). The moisture content of the materials was obtained by gravimetric methods, using a moisture balance analyzer (MB200, Ohaus, Parsippany, NJ, USA) equipped with a halogen lamp at 120°C. The sensitivity of the measurements was 0.01%. The total ash content was determined following the methodology described in the AOAC [10]. Briefly, samples were heated on a muffle oven (N31R, Mueller and Krempel, Nabertherm, Germany) at 546°C for 7 h. The amount of the cooled residue was taken as the total ash content. The content of sugars was determined by the phenol-sulfuric acid colorimetric method [11].
The elemental analysis was conducted by Energy Dispersive X-ray analysis (EDX) (JEOL 6490LV, Peabody, MA). About 0.2 g of the samples were spread evenly over an aluminum stub and sputter-coated on a vacuum chamber (Desk IV, Denton Vacuum, Moorestown, NJ USA) with a 30% gold coating for 5 min and operated at 15 kV. X-ray diffraction patterns were taken using an X-ray generator with CuKα radiation and the linear surface sample scanning was conducted for 300 s, 10 mm depth of field and 50 μm diffusion. A Malvern Nano-ZS90 Zetasizer equipped with a Zetasizer Software (vs 7.11, Malvern Instruments Ltd., UK) was employed to determine the particle charge at 25°C using the principle of Laser Doppler Velocimetry (LDV). The zeta potential (PZ) measurements were performed by adding 700 μL of the sample in a polystyrene cell. Samples were analyzed between 12 and 16 cycles with a voltage of 4 mV. The ionic exchange test was carried out by weighing from 0.5 to 1 g of sample and 10 mL of 6 N HCl was added and allowed to stand for 24 h followed by centrifugation for 20 min at 1550 rpm. Subsequently, it was submitted to washing with 1% saline solution twice and titrated with 0.8 N NaOH solution. All measurements were expressed on a dry weight basis.
Water sorption studies were conducted employing the static gravimetry method on chambers having several saturated salts rendering different relative humidities. Thus, K2CO3, NaBr, NaCl, KCl, KNO3 and H20 rendered constant relative humidities of 43, 58, 68, 75, 94 and 100%, respectively. The isotherms were built at 25°C and samples were allowed to reach equilibrium for 2 weeks when the difference between two consecutive measurements was not larger than 0.1%. Data were fitted to several sorption models, and only the one that presented the best fit was discussed in this study. The ability of the fertilizers for water sorption was studied by applying the Young and Nelson model which is expressed as:
where
These tests were conducted on samples without any previous treatment according to the National Technical Standard 4092 of microbiology. Briefly, 1 g of sample was dispersed in 10 mL of peptone water, making the pertinent dilution factors from 1×10−1 to 1×10−10. Subsequently, 1 mL of the solution was poured onto a 20 mL culture plate (Merck). Samples were then incubated at 37°C between 24 and 48 h. The results were reported as colony forming units per gram of fertilizer (CFU/g).
The principal component analysis (PCA) was the type of multivariate analysis used to identify and compare the relationships and patterns among the physicochemical and functional properties of the fertilizers. The software Minitab® (v. 16 Minitab, Inc., State College, PA) was used for data processing. The relationship between the different crop characteristics was assessed by the Pearson’s correlation coefficient at a significance level of
Microwave radiation accelerated the degradation of alkaline shrimp waste forming a product having a hydrolysis degree of 42%. Thus, hydroxyl radicals of the alkaline media along with microwave radiation contributed to molecular weight reduction of waste compounds such as carbohydrates and proteins and avoided the need for a time-consuming composting of the raw waste and thus, decreased the initial microbial population avoiding further release of putrescine and other nitrous volatile compounds. Shrimp waste possesses the striated type muscle arranged into muscle fibers that are bound together by a connective tissue where the prevalent amino acid is lysine. These muscle proteins are associated to chitin and minerals such as calcium phosphate. The protein and chitin availability are important since they will eventually turn into accessible nitrogen for legumes. The magnitude of the peptide and glycosidic bonds cleavage during microwave hydrolysis rendered an organic fertilizer having a moderate hydrolysis degree.
During the wet massing process MCC was essential as spheronization aid. Previous studies (data not shown) determined the need of at least 50% MCC as optimal in order to obtain a spherical pellet having good mechanical properties (FPE and FHPE). Thus, MCC fibers alone or combined with waste coalesced and formed larger particles which were then shaped once they passed through the screen orifices. These, in turn, were molded in the spheronizer which cut-off and rounded-off the sharply and roughly surfaces. The rotating plate operating at the 15 Hz rate and residence time of 120 s produced a denser and smoother pellet surface due to the combined action of the centrifugal force created by plate rotation, the vertical force formed by collision, and the gravitational force allowing for the formation of a toroidal or twisted rope motion having an spiral pattern. As a result, this high frequency and short residence time generated more frictional and rotational forces where the initial small, oblong and irregular particles experienced growth, folding and edge rounding which was subsequently shaped into dumb bells. These dumb bells were then twisted, broken, rounded and transformed into spherical or semispherical beads.
On the contrary, raw waste
The nutritional content of the shrimp-based fertilizers (SBF) is listed in Table 1. The hydrolyzed product retained much of the initial nutrients contained in the raw shrimp exoskeletons. The alkaline microwave hydrolysis disrupted the inter and intra-molecular hydrogen bond pattern of complex carbohydrates and proteins initially present in the material, disturbing the regularity of the 3D packing and stereochemistry between chains, especially of the most accessible amorphous regions. As a result, the alkaline hydrolysis of the non-crystalline fraction removed monomer blocks of repeated units, especially those located at the crystallite surface and hence, NaOH accessed the β-1,4N-acetyl and peptidic linkages, simultaneously. The net result was a reduction in the crystallinity of the shrimp fertilizer. In fact, the application of high intensity waves caused chemical and mechanical degradation in the waste particles, resulting in changes in the native shrimp protein and carbohydrate structure into a molten globule state.
The pH and moisture content of these fertilizers ranged from 5.0 to 8.5 and from 2.5 to 11%, respectively. Once the fertilizers were incorporated into the soil maintained a slightly neutral ambient (∼6.7–7.2) and the electrical conductivity ranged from ∼12 to 28 μS/cm. A neutral pH ensured a good availability of the nutrients to the leguminous plants. The high moisture content eased the transformation of macromolecular N into NH4+ and NO3− by bacteria action resulting in its mineralization and easy uptake by plants as reported previously [13]. The slightly alkaline pH of F0 is attributed to the presence of peptides, and elements such as Ca2+ and Mg2+. Further, these divalent ions can then be adsorbed onto the surface of tiny clay particles of the soil which had a net negative charge. The magnesium level in the shrimp-based fertilizers (SBF) was lower than that of calcium so its effect on the soil structure was negligible. The negative surface charge of soil particles is believed to improve P availability in form of phosphates as present in shrimp waste. These phosphates along with the P2O5 of CF2 could be responsible for the large
The zeta potential indicates the average charge in the particles and gives a measurement of the ion activity of the fertilizers. All materials exhibited a net negative charge and CF2 had the largest ion exchange capability and electrical conductivity altogether. Conversely, FHPE exhibited the smallest value of electrical conductivity. Interestingly, CS showed a large ionic exchange capability, but a moderate electric conductivity due to the residual ionized functional groups present in this type of cellulose.
Table 2 lists the elemental composition of each type of SBF, substrates and commercial fertilizers. Alkaline microwave hydrolysis had a marked effect on the nutritional content of the shrimp waste. This had a large content of essentially C, N, Ca and P. On the other hand, Fe, Si, Al, Mg and Cl were present as the main microelements. The content of Mg, was larger in the F0 than SS, CS and pellets, whereas the K content was low in all cases except for CF1. The C/N ratio was slower than 10 for F0, FPE, FHPE, CF2, and FPC whereas CF1 (10.5) and SS (33.1) showed the largest C/N ratio due to their low content of N. Further, the SS and CF1 were poor in organic nitrogen, but rich in carbon, silicon and aluminum. On the other hand, CS had a poor content of most elements except for carbon and oxygen. The SS, FPC and CS presented low levels of essential elements such as N, P, and Ca as compared to F0, FPE and FHPE. Interestingly, CF1 and SS showed traces of other microelements such as K, Ti, and essentially CF1 was the only fertilizer which contained traces of Mn. On the other hand, CF2 contained N from urea and P from P2O5 at a 13:1 ratio.
Element | F0 | FPC | FPE | FHPE | SS | CS | CF1 | CF2 | |
---|---|---|---|---|---|---|---|---|---|
C | 43 ± 3.3 | 33.1 ± 5 | 43 | 38.1 | 33.1 ± 1.1 | *53.5 ± 4.5 | 41.0 ± 10.3 | 39.0 ± 3.63 | 0.00 |
O | 33.3 ± 2.1 | *42.5 ± 3 | 33.3 | 37.9 | *42.5 ± 0.4 | *46. ± 5.2 | 39 ± 6 | 37.0 ± 2.4 | 0.00 |
N | *15.9 ± 5.4 | 0 ± 0 | *15.9 | *7.95 | 0 ± 0 | 0 ± 0 | 0 ± 0 | *15.9 ± 4.9 | 0.00 |
Ca | *5.8 ± 2.7 | 0 ± 0 | *5.4 | *2.8 | 0.2 ± 0.1 | 0 ± 0 | 0.9 ± 0.2 | 0.14 ± 0.14 | 0.00 |
P | *1.5 ± 1.4 | 0 ± 0 | 1.5 | 0.8 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 1.2 ± 1.2 | 0.00 |
Si | 0.2 ± 0.1 | *18.2 ± 1 | 0 ± 0 | 0 | *18.1 ± 1.6 | 0 ± 0 | *11.4 ± 3.2 | 0.9 ± 0.4 | 0.00 |
Fe | 1.5 ± 1.0 | 0 ± 0 | 0 ± 0 | 0.59 | 1.2 ± 0.8 | 0.0 ± 0.0 | 1.8 ± 1.8 | 5.4 ± 5.4 | 0.08 |
Al | 0.1 ± 0.1 | *4.1 ± 0.5 | 0 ± 0 | *2.1 | *4.1 ± 0.7 | 0.5 ± 0.5 | *2.7 ± 0.5 | 0.0 ± 0.0 | 0.00 |
Mg | 0.4 ± 0.1 | 0.21 ± 0.1 | 0.35 | 0.28 | 0.2 ± 0.1 | 0 ± 0 | *0.6 ± 0.4 | 0.4 ± 0.3 | 0.05 |
Cl | *0.2 ± 0.1 | 0 ± 0 | *0.23 | 0.12 | 0 ± 0 | 0 ± 0 | *0.3 ± 0.1 | 0.03 ± 0.03 | 0.00 |
Na | 0.2 ± 0.1 | 0.05 ± 0 | 0 ± 0 | 0.1 | 0.1 ± 0.1 | 0.0 ± 0.0 | *0.8 ± 0.2 | *0.47 ± 0.13 | 0.00 |
K | 0 ± 0 | 0.13 ± 0 | 0 ± 0 | 0.1 | 0 ± 0 | 0 ± 0 | *1.1 ± 0.2 | 0 ± 0 | 0.00 |
Ti | 0 ± 0 | 0 ± 0 | 0 ± 0 | 0 | 0.5 ± 0.5 | 0. ± 0.0 | *0.4 ± 0.4 | 0 ± 0 | 0.06 |
Mn | 0 ± 0 | 0 ± 0 | 0 ± 0 | *0.1 | 0 ± 0 | 0 ± 0 | 0.03 ± 0.03 | 0 ± 0 | 0.00 |
C/N | 2.7 | 33.1 | 2.7 | 4.8 | 33.1 | 53.5 | 41 | 2.5 | NA |
Elemental analysis of the shrimp-based fertilizers, substrates and commercial organic fertilizers (
F0, raw waste; FPC, cellulose pellets; FPE, exoskeleton pellets; FHPE, hydrolyzed exoskeleton pellets; SS, soil substrate; CS, cotton substrate CF1 and CF2 correspond to the commercial fertilizers; mean values with an asterisk within the column are significantly different according to the Tukey’s test at
The water vapor sorption isotherm of a material describes the relationship between the relative vapor pressure or water activity, (aw) and water content over a range of aw values obtained at a given temperature [14]. The fitting water sorption parameters obtained from the Young-Nelson model revealed a good fitting to this model having an r2 larger than 0.9582 as compared to other models not shown in this study.
Figure 1a shows that during the first sorption stage (aw < 0.45), the isotherms exhibited a convex shape as the water molecules rapidly sorb onto the available sorption sites until a monolayer is formed. The shape of the isotherms during this first stage did not differ substantially among the different SBF, but was larger for SS and CF2. Thereafter, there was a gradual increase in water content with aw up to ∼0.80 where an abrupt increase of water content was observed possibly due to capillary condensation phenomena. Interestingly, most fertilizers showed a steady increase in monolayer and multilayer formation up to aw of 0.45, afterwards the water molecules although still in vapor form, begin to diffuse within the particle core except for SS, FPE and FPC in which this process started at a very low aw (Figure 1b). Therefore, in these materials isotherms proved that water did not form a continuous monolayer because the multilayer and particle water absorption occurred simultaneously. This phenomenon has been attributed to the tendency of water molecules to cluster around exchangeable cations found in different soils [14]. As a result, water molecules bind as succeeding layers of water molecules rather to empty sites on the surface of the particle. Thus, the formation of a second layer probably started at lower concentration than those corresponding to the monolayer formation. Clustering was expected to occur in most cases since the amount of water molecules on the particle was higher than the quantity that can be bound within the particle. Further, SS and CF2
Water sorption isotherms fitted to the Young-Nelson model. (a) Fitted isotherms, (b) deconvoluted sorption behavior for the monolayer and multilayers, and (c) deconvoluted sorption behavior for the intrinsic absorbed water (
CF2 at all aw showed the lowest tendency for clustering, but the largest sorption within the particle core. The deconvoluted curves showed that the monolayer formation presented a type III Langmuir isotherm, whereas the curves for the multilayer sorption showed a type II isotherm. Interestingly, CF2 also showed the largest cation exchange capability and ionic conductivity. This agrees with previous studies that reported a relationship between the high water sorption and the ion exchange capability of the soil [15].
The raw soil substrate (SS) showed the largest E parameter and hence, presented the largest heat of endothermic sorption (ΔH). Further, SS and CF2 showed the largest intrinsic absorbed water (B parameter), whereas CS showed the largest adsorption ability forming multilayers. CF2 and SS showed the largest hygroscopicity, especially at a water activity larger than 0.4. Further, these two samples had the largest ability to absorb water intrinsically, whereas SS and CS
The ionic exchange capability of the SBF decreased upon hydrolysis as compared to F0 due to leakage of some ions such as calcium and phosphates. Further, the incorporation of these fertilizers into the soil did not have a marked effect on the physicochemical properties of the topsoil due to a dilution effect. Thus, the electrical conductivity of the soil was low (10–28 μS/cm) as compared to the pure fertilizers, but outside the range recommended for other horticultural plants (0.76–4.0 mS cm−1) [16]. Further, the negative charge of the SBF is due to the residual amine groups of chitin and amino acids. The ash content of the SS (45.4%) and CF1 (42.8%) were larger than most fertilizers (<5.3%) mainly due to their high silicate and carbonate content. The content of carbohydrates of FPE and FHPE (90–94%) was lower than that of CS and FPC; whereas the content of proteins was relatively low and tended to disappear upon hydrolysis as happened for sugars. Moreover, densification (0.51–0.89 g/cm3) and porosity (48–66%) increased upon pelletization, whereas CS and SS as expected showed the lowest bulk density, but the largest total porosity.
It was estimated that complex carbohydrates present in SBF such as chitin could act as a cementing agents bonding soil particles together improving soil structure and stability. Further, it is reported that calcium ions could act as a cementing agents, bonding soil particles into aggregates resulting in the formation of strong, water-stable aggregates [17]. However, the net postharvest bulk density of the soil did not vary significantly upon treatment with fertilizers probably due to the low applied rate, and density remained in the range generally considered suitable for the normal growth of crops. This low bulk density made root growth and penetration easier and improved the size and system of voids in the soil matrix enabling aeration and water movement. Moreover, the particle size of the powdered fertilizers ranged from 50 to 150 μm and that of the soil and pellets were about 300 and 2 mm, respectively being able to decompose slowly matching the particle size of the soil.
Figure 2 depicts legume growth as a function of time. The largest and fastest growing period of both legumes occurred within the first 2 months of the crop cycle. Both plants followed a sigmoid or S-shaped curve during the growing season corresponding to the period of rapid nutrient uptake. Further, both legumes showed the best growing phase upon fertilization with CF2. Conversely, a slow growth profile for both plants was observed once fertilized with FPE and FHPE. This phenomenon is explained by the reduction of essential nutrients different from C and O.
Growth profiles given by shrimp-based fertilizers, substrates and commercial fertilizers: (A)
On the other hand, the pod length, pod mass, and seed mass of
Sample | ||||||||
---|---|---|---|---|---|---|---|---|
Pod length (cm) | Pod mass (g) | Seed mass (g) | Pod number | Pod length (cm) | Pod mass (g) | Seed mass (g) | Pod number | |
F0 | *10 ± 1.2 | *4.56 ± 2.0 | 1.83 ± 0.3* | 2 ± 0.3 | 5.5 ± 1.1 | 1.23 ± 0.8 | *0.7 ± 0.1 | *3 ± 1 |
FPC | 7 ± 0 | 0.77 | 0.1 ± 0.0 | 1 ± 0.0 | *0 ± 0 | 0 ± 0 | *0 ± 0 | *0 ± 0 |
FPE | 4.1 ± 1.3 | 0.46 ± 0.1 | 0.22 ± 0.1 | *4 ± 0.5 | 5 ± 0 | 0.6 ± 0 | *0.28 ± 0 | 1 ± 0 |
FHPE | 5 ± 1.6 | 0.82 ± 0.2 | 0.41 ± 0.1 | 1.5 ± 0.5 | 4.4 ± 0.5 | 0.4 ± 0.1 | 0.3 ± 0.1 | *3 ± 0 |
SS | 4.9 ± 1.3 | 0.62 ± 0.2 | 0.35 ± 0.1 | 1 ± 0.0 | *6.5 ± 1.2 | *3.9 ± 0.9 | *1.43 ± 0.1 | 1 ± 0 |
CS | 4.3 ± 1.3 | 0.26 ± 0.1 | 0.1 ± 0.0 | 2 ± 0.1 | 5 ± 0.5 | 1.1 ± 0.5 | 0.43 ± 0.1 | 2 ± 0.1 |
CF1 | *7.7 ± 1.1 | 2.13 ± 0.8 | *0.73 ± 0.1 | *3 ± 1.0 | 6.0 ± 0.8 | 0.74 ± 0.1 | 0.46 ± 0.1 | 2 ± 1 |
CF2 | *10.1 ± 0.1 | *4.7 ± 0.1 | *1.2 ± 0.1 | 1.1 ± 0.2 | 5.5 ± 0.6 | 1.5 ± 0.6 | 0.6 ± 0.2 | 2 ± 0.5 |
0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
Effect of shrimp-based fertilizers, substrates and commercial fertilizers on plant development for Phaseolus vulgaris and Pisum sativum.
FPC, cellulose pellets; FPE, exoskeletons pellets; FHPE, hydrolyzed exoskeleton pellets; SS, soil substrate; CS, cotton substrate; CF, commercial fertilizers; mean values with an asterisk within the column are significantly different according to the Tukey’s test at
The SBF were applied at a rate of 4 g/kg soil in three monthly amendments. SBF having 8–20% N had a variable effect on legume growth characteristics depending on the composition. As a result, they showed distinctive quantitative and qualitative traits of grain yield of legumes, especially for
The soil amended with the fertilizers had pH values between 6.7 and 7.1, which are considered optimum for the rapid development of most ubiquitous microorganisms. At this pH range N loss due to ammonia volatilization is prevented since this phenomenon only occurs at acid pH (<6.0) [18]. Soil porosity was ∼83% and moisture at saturation was >40% and these levels were not affected by fertilization. The lower water content of SBF was attributed to the presence of insoluble carbohydrates, proteins and of calcium ions. The high moisture content in the soil near to field capacity was responsible for the high diversity of viable microbial during the legume developing phase. These in turn, promoted mineralization and increased available N. The high population of aerobic bacteria found during the whole crop cycle eased nitrogen fixation from the fertilizers and the atmosphere. Interestingly,
It is accepted that during the decomposition of an organic fertilizer the microbial population requires an optimal diet with a C:N ratio of ∼15:1 to meet their needs for nutrients. Since the F0, FPE, FHPE and CF2 had a C:N ratio of less than 15:1 they had more N than the microflora require for their own growth in the initial crop cycle and are likely to provide significant plant available N leading to an increased mineral
The fertilizers once incorporated into the soil showed a variable microbial population which decreased over time, possibly due to depletion of soil nutrients that share with plants in a symbiotic way. In fact, the bacteria population was larger in soils containing
Time (month) | F0 | FPC | FPE | FHPE | SS | CS | CF1 | CF2 | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
PV | PS | PV | PS | PV | PS | PV | PS | PV | PS | PV | PS | PV | PS | PV | PS | |
1 | 100 | 40 | 88 | 38 | 72 | 40 | 90 | 20 | 102 | 36 | 1 | 0.2 | 580 | 370 | 12 | 32 |
2 | 103 | 26 | 0.36 | 8.25 | 98 | 6 | 126 | 100 | 130 | 102 | 3 | 0.1 | 785 | 64 | 17 | 33 |
3 | 56 | 4.9 | 0.3 | 8.9 | 68 | 4.9 | 52 | 48 | 33 | 30 | 2 | 0.1 | 54 | 23 | 19 | 28 |
1 | 0.1 | 2 | 2 | 3 | 14 | 2 | 20 | 36 | 10 | 23 | 0.25 | 0.5 | 7.8 | 6 | 18 | 48 |
2 | 1 | 6 | 0.1 | 1.7 | 1.1 | 1 | 1.2 | 1.4 | 14.5 | 15 | 1 | 0.5 | 2.5 | 4 | 27 | 37 |
3 | 10 | 12 | 0.6 | 0.1 | 0.2 | 5 | 1.6 | 0.81 | 23.6 | 28 | 1 | 0.5 | 1 | 3 | 18 | 47 |
1 | 10,000 | 200 | 440 | 127 | 51 | 200 | 45 | 6 | 102 | 16 | 40 | 4 | 744 | 617 | 7 | 7 |
2 | 1030 | 43 | 36 | 49 | 891 | 60 | 1050 | 714 | 90 | 68 | 30 | 2 | 3140 | 160 | 6 | 9 |
3 | 56 | 4 | 5 | 890 | 3400 | 10 | 325 | 593 | 14 | 11 | 20 | 2 | 540 | 77 | 11 | 6 |
Total aerobic bacteria and fungi of the soil fertilized with the shrimp-based fertilizers and commercial fertilizers.
FPC, cellulose pellets; FPE, exoskeleton pellets; FHPE, hydrolyzed exoeskeleton pellets; SS, soil substrate; CS: cotton substrate; CF, commercial fertilizers; PV, Phaseolus vulgaris; PS, Pisum sativum.
The multivariate analysis rendered interesting facts about this study. The first three components explained 73.3% of data variability (Figure 3). In the PCA plot four great clusters are observed apart from the center. The first one depicts the influence of Mg and Na on crop quality of
Principal component plot for key properties of fertilizers.
The raw waste rendered an optimal crop quality, especially for
The authors are grateful to Colciencias for providing the financial resources for the execution of this study through the Grant No. 111571551545 and contract no. 036-2016. Authors thank CODI for their sustainability strategy 2018–2019 of University of Antioquia.
The authors declare no conflict of interest.
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Pal is Professor of Physics at Mahindra École\nCentrale Hyderabad India since July 1st 2014 after retirement\nas Professor of Physics from IIT Delhi; Ph.D.’1975 from IIT\nDelhi; Fellow of OSA and SPIE; Senior Member IEEE;\nHonorary Foreign Member Royal Norwegian Society for\nScience and Arts; Member OSA Board of Directors (2009-\n11); Distinguished Lecturer IEEE Photonics Society (2005-\n07).",institutionString:null,institution:{name:"Indian Institute of Technology Delhi",country:{name:"India"}}},{id:"69653",title:"Dr.",name:"Chusak",middleName:null,surname:"Limsakul",slug:"chusak-limsakul",fullName:"Chusak Limsakul",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"Prince of Songkla University",country:{name:"Thailand"}}},{id:"23804",title:"Dr.",name:"Hamzah",middleName:null,surname:"Arof",slug:"hamzah-arof",fullName:"Hamzah Arof",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/23804/images/5492_n.jpg",biography:"Hamzah Arof received his BSc from Michigan State University, and PhD from the University of Wales. Both degrees were in electrical engineering. His current research interests include signal processing and photonics. Currently he is affiliated with the Department of Electrical Engineering, University of Malaya, Malaysia.",institutionString:null,institution:{name:"University of Malaya",country:{name:"Malaysia"}}},{id:"41989",title:"Prof.",name:"He",middleName:null,surname:"Tian",slug:"he-tian",fullName:"He Tian",position:null,profilePictureURL:"//cdnintech.com/web/frontend/www/assets/author.svg",biography:null,institutionString:null,institution:{name:"East China University of Science and Technology",country:{name:"China"}}},{id:"33351",title:null,name:"Hendra",middleName:null,surname:"Hermawan",slug:"hendra-hermawan",fullName:"Hendra Hermawan",position:null,profilePictureURL:"https://mts.intechopen.com/storage/users/33351/images/168_n.jpg",biography:null,institutionString:null,institution:{name:"Institut Teknologi Bandung",country:{name:"Indonesia"}}},{id:"11981",title:"Prof.",name:"Hiroshi",middleName:null,surname:"Ishiguro",slug:"hiroshi-ishiguro",fullName:"Hiroshi Ishiguro",position:null,profilePictureURL:"https://s3.us-east-1.amazonaws.com/intech-files/0030O00002bRglaQAC/Profile_Picture_1626411846553",biography:"Hiroshi Ishiguro is an award-winning roboticist and innovator. 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Tourism",slug:"muslim-travel-behavior-in-halal-tourism",totalDownloads:3641,totalCrossrefCites:13,totalDimensionsCites:19,abstract:"Destination marketers need to understand Muslim travel behaviour in order to satisfy his/her needs especially in Halal tourism industry. This chapter discussed the importance of getting the terminologies right in the field of Muslim-friendly or Halal tourism. Muslim tourist needs are identified when travelling abroad: Muslim-friendly hotels, Halal food, Muslim-friendly phone application, Muslim-friendly airport, Halal holiday, Halal tourism websites, Halal healthcare facilities and services, Halal cruise and Halal swimming suit. Implications related to Halal tourism are also discussed.",book:{id:"6102",slug:"mobilities-tourism-and-travel-behavior-contexts-and-boundaries",title:"Mobilities, Tourism and Travel Behavior",fullTitle:"Mobilities, Tourism and Travel Behavior - Contexts and Boundaries"},signatures:"Mohamed Battour",authors:[{id:"206480",title:"Prof.",name:"Mohamed",middleName:null,surname:"Battour",slug:"mohamed-battour",fullName:"Mohamed Battour"}]},{id:"58056",doi:"10.5772/intechopen.71459",title:"Cruise Tourism and Sustainability in the Mediterranean. 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Venice special legislation on tourist cruises and the debate on cruise ships in the Venetian lagoon are examined to highlight critical factors and remedies. Much remains to be done to balance the rapidly growing demand for cruising against its negative environmental impacts on this fragile city. The case of Venice shows how cruise tourism is a complex issue in relation to the sustainability paradigm. Indeed, the controversies stem from the different points of view of the various actors involved in the market—tourists, cruise companies, local administrations, suppliers, local companies and environmental and heritage protection associations just to mention a few—which identify benefits and costs of cruise industry in different ways and timespan.",book:{id:"6102",slug:"mobilities-tourism-and-travel-behavior-contexts-and-boundaries",title:"Mobilities, Tourism and Travel Behavior",fullTitle:"Mobilities, Tourism and Travel Behavior - Contexts and Boundaries"},signatures:"Vincenzo Asero and Stefania Skonieczny",authors:[{id:"207224",title:"Dr.",name:"Vincenzo",middleName:null,surname:"Asero",slug:"vincenzo-asero",fullName:"Vincenzo Asero"},{id:"208063",title:"Dr.",name:"Stefania",middleName:null,surname:"Skonieczny",slug:"stefania-skonieczny",fullName:"Stefania Skonieczny"}]},{id:"73861",doi:"10.5772/intechopen.94411",title:"The Azores Archipelago as a Region with Vast Potential for the Development of Adventure and Slow Tourism",slug:"the-azores-archipelago-as-a-region-with-vast-potential-for-the-development-of-adventure-and-slow-tou",totalDownloads:486,totalCrossrefCites:8,totalDimensionsCites:9,abstract:"WTO (World Tourism Organization) recognizes that adventure tourism is a journey that includes at least two of three elements: (a) physical activity, (b) natural environment; and (c) cultural immersion. With this in mind, the Autonomous Region of Azores, classified as one of the OR (Outermost Regions) by the European Union (EU), meets several of those elements. Therefore, the Archipelago shows several potential for the development of this typology of tourism. However, this insular region faces many challenges. Some of those obstacles are also great opportunities for regional development towards new sustainable models. For example, there is the islands’ geographical location, which enables exceptional territorial development opportunities and growth opportunities. Contextually, the Archipelago’s nine islands afford great variety to the destination, and the tranquil rural landscape fits the perfect framework for unparalleled, charming, and relaxing experiences. Moreover, the Archipelago’s specific characteristics, as its volcanic nature, make the destination a perfect place to be explored. These are just some examples of the region’s potential to develop this typology of tourism, based on nature, and consequently, a vehicle to achieve the so-desired regional sustainability.",book:{id:"10617",slug:"peripheral-territories-tourism-and-regional-development",title:"Peripheral Territories, Tourism, and Regional Development",fullTitle:"Peripheral Territories, Tourism, and Regional Development"},signatures:"Pedro Pimentel, André Oliveira, Gualter Couto, João Crispim Ponte and Rui Castanho",authors:[{id:"290571",title:"Dr.",name:"Rui Alexandre",middleName:null,surname:"Castanho",slug:"rui-alexandre-castanho",fullName:"Rui Alexandre Castanho"},{id:"325801",title:"Prof.",name:"Gualter",middleName:"Manuel Medeiros Do",surname:"Couto",slug:"gualter-couto",fullName:"Gualter Couto"},{id:"332268",title:"Prof.",name:"Pedro",middleName:null,surname:"Pimentel",slug:"pedro-pimentel",fullName:"Pedro Pimentel"},{id:"332271",title:"MSc.",name:"André",middleName:null,surname:"Oliveira",slug:"andre-oliveira",fullName:"André Oliveira"},{id:"332272",title:"MSc.",name:"João Crispim",middleName:null,surname:"Ponte",slug:"joao-crispim-ponte",fullName:"João Crispim Ponte"}]},{id:"75521",doi:"10.5772/intechopen.96651",title:"Introductory Chapter: Rural Tourism as a Catalyst for Sustainable Regional Development of Peripheral Territories",slug:"introductory-chapter-rural-tourism-as-a-catalyst-for-sustainable-regional-development-of-peripheral-",totalDownloads:203,totalCrossrefCites:5,totalDimensionsCites:6,abstract:null,book:{id:"10617",slug:"peripheral-territories-tourism-and-regional-development",title:"Peripheral Territories, Tourism, and Regional Development",fullTitle:"Peripheral Territories, Tourism, and Regional Development"},signatures:"Rui Alexandre Castanho, Gualter Couto and Rossana Santos",authors:[{id:"290571",title:"Dr.",name:"Rui Alexandre",middleName:null,surname:"Castanho",slug:"rui-alexandre-castanho",fullName:"Rui Alexandre Castanho"},{id:"325801",title:"Prof.",name:"Gualter",middleName:"Manuel Medeiros Do",surname:"Couto",slug:"gualter-couto",fullName:"Gualter Couto"},{id:"325802",title:"Ph.D.",name:"Rossana",middleName:null,surname:"Santos",slug:"rossana-santos",fullName:"Rossana Santos"}]},{id:"56858",doi:"10.5772/intechopen.70494",title:"A Comprehensive Review of the Quality Approach in Tourism",slug:"a-comprehensive-review-of-the-quality-approach-in-tourism",totalDownloads:2073,totalCrossrefCites:3,totalDimensionsCites:6,abstract:"This study summarizes the evolution of the quality approach in tourism. Environmental issues are also addressed, as there are strong interdependencies between these two areas. Especially in tourism, the quality-environment integration is essential. The study reveals the diversity of quality and environmental models currently used worldwide, including general models for quality assessment and management, applied in all areas, and also the tourism-specific models. The objectives of this synthesis are to achieve a systematization of the information on the quality and environment approach in tourism, and to highlight the main axes of changes. The conclusions formulated illustrate the future directions to improve the quality approach in tourism, concerning both the quality models and their implementation. The results of this comprehensive review are useful to the tourism coordination structures at national and regional level, and also to academics and researchers, to better understanding the trends in quality approach and optimizing their quality-related actions. The workpaper is based on the reports of World Tourism Organization and other tourism professional structures, as well as studies and researches published in specialized journals related to quality and environment approach in tourism.",book:{id:"6102",slug:"mobilities-tourism-and-travel-behavior-contexts-and-boundaries",title:"Mobilities, Tourism and Travel Behavior",fullTitle:"Mobilities, Tourism and Travel Behavior - Contexts and Boundaries"},signatures:"Diana Foris, Maria Popescu and Tiberiu Foris",authors:[{id:"206947",title:"Dr.",name:"Diana",middleName:null,surname:"Foris",slug:"diana-foris",fullName:"Diana Foris"},{id:"207967",title:"Prof.",name:"Maria",middleName:null,surname:"Popescu",slug:"maria-popescu",fullName:"Maria Popescu"},{id:"207968",title:"Prof.",name:"Tiberiu",middleName:null,surname:"Foris",slug:"tiberiu-foris",fullName:"Tiberiu Foris"}]}],mostDownloadedChaptersLast30Days:[{id:"58056",title:"Cruise Tourism and Sustainability in the Mediterranean. 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Venice special legislation on tourist cruises and the debate on cruise ships in the Venetian lagoon are examined to highlight critical factors and remedies. Much remains to be done to balance the rapidly growing demand for cruising against its negative environmental impacts on this fragile city. The case of Venice shows how cruise tourism is a complex issue in relation to the sustainability paradigm. Indeed, the controversies stem from the different points of view of the various actors involved in the market—tourists, cruise companies, local administrations, suppliers, local companies and environmental and heritage protection associations just to mention a few—which identify benefits and costs of cruise industry in different ways and timespan.",book:{id:"6102",slug:"mobilities-tourism-and-travel-behavior-contexts-and-boundaries",title:"Mobilities, Tourism and Travel Behavior",fullTitle:"Mobilities, Tourism and Travel Behavior - Contexts and Boundaries"},signatures:"Vincenzo Asero and Stefania Skonieczny",authors:[{id:"207224",title:"Dr.",name:"Vincenzo",middleName:null,surname:"Asero",slug:"vincenzo-asero",fullName:"Vincenzo Asero"},{id:"208063",title:"Dr.",name:"Stefania",middleName:null,surname:"Skonieczny",slug:"stefania-skonieczny",fullName:"Stefania Skonieczny"}]},{id:"56858",title:"A Comprehensive Review of the Quality Approach in Tourism",slug:"a-comprehensive-review-of-the-quality-approach-in-tourism",totalDownloads:2073,totalCrossrefCites:3,totalDimensionsCites:6,abstract:"This study summarizes the evolution of the quality approach in tourism. Environmental issues are also addressed, as there are strong interdependencies between these two areas. Especially in tourism, the quality-environment integration is essential. The study reveals the diversity of quality and environmental models currently used worldwide, including general models for quality assessment and management, applied in all areas, and also the tourism-specific models. The objectives of this synthesis are to achieve a systematization of the information on the quality and environment approach in tourism, and to highlight the main axes of changes. The conclusions formulated illustrate the future directions to improve the quality approach in tourism, concerning both the quality models and their implementation. The results of this comprehensive review are useful to the tourism coordination structures at national and regional level, and also to academics and researchers, to better understanding the trends in quality approach and optimizing their quality-related actions. The workpaper is based on the reports of World Tourism Organization and other tourism professional structures, as well as studies and researches published in specialized journals related to quality and environment approach in tourism.",book:{id:"6102",slug:"mobilities-tourism-and-travel-behavior-contexts-and-boundaries",title:"Mobilities, Tourism and Travel Behavior",fullTitle:"Mobilities, Tourism and Travel Behavior - Contexts and Boundaries"},signatures:"Diana Foris, Maria Popescu and Tiberiu Foris",authors:[{id:"206947",title:"Dr.",name:"Diana",middleName:null,surname:"Foris",slug:"diana-foris",fullName:"Diana Foris"},{id:"207967",title:"Prof.",name:"Maria",middleName:null,surname:"Popescu",slug:"maria-popescu",fullName:"Maria Popescu"},{id:"207968",title:"Prof.",name:"Tiberiu",middleName:null,surname:"Foris",slug:"tiberiu-foris",fullName:"Tiberiu Foris"}]},{id:"56647",title:"Muslim Travel Behavior in Halal Tourism",slug:"muslim-travel-behavior-in-halal-tourism",totalDownloads:3641,totalCrossrefCites:13,totalDimensionsCites:19,abstract:"Destination marketers need to understand Muslim travel behaviour in order to satisfy his/her needs especially in Halal tourism industry. This chapter discussed the importance of getting the terminologies right in the field of Muslim-friendly or Halal tourism. Muslim tourist needs are identified when travelling abroad: Muslim-friendly hotels, Halal food, Muslim-friendly phone application, Muslim-friendly airport, Halal holiday, Halal tourism websites, Halal healthcare facilities and services, Halal cruise and Halal swimming suit. Implications related to Halal tourism are also discussed.",book:{id:"6102",slug:"mobilities-tourism-and-travel-behavior-contexts-and-boundaries",title:"Mobilities, Tourism and Travel Behavior",fullTitle:"Mobilities, Tourism and Travel Behavior - Contexts and Boundaries"},signatures:"Mohamed Battour",authors:[{id:"206480",title:"Prof.",name:"Mohamed",middleName:null,surname:"Battour",slug:"mohamed-battour",fullName:"Mohamed Battour"}]},{id:"56679",title:"Determinants of Satisfaction with the Tourist Destination",slug:"determinants-of-satisfaction-with-the-tourist-destination",totalDownloads:2082,totalCrossrefCites:4,totalDimensionsCites:5,abstract:"Achieving tourist satisfaction is one of the most important factors in terms of stewardship by the different actors in tourist destinations. Even though there is extensive literature that analyses tourist satisfaction, there is no final consensus regarding which variables influence its creation. This study proposes a model in which satisfaction is a consequence of the functional, hedonic and symbolic benefits. The hedonic benefit is considered a multidimensional construct. At the same time, we suggest that this triad of benefits is a consequence of cognitive perception and affective evaluation. For this study, a non-probability sample of 750 tourists was used, based on quotas distributed proportionally among the main Chilean tourist destinations. Once the psychometric properties of the scales used in the study were verified, a structural equation model was estimated and it was found that satisfaction is a consequence of the functional and hedonic, but not the symbolic benefit. It is confirmed as well that the functional, hedonic and symbolic benefits are a consequence of cognitive perception and affective evaluation.",book:{id:"6102",slug:"mobilities-tourism-and-travel-behavior-contexts-and-boundaries",title:"Mobilities, Tourism and Travel Behavior",fullTitle:"Mobilities, Tourism and Travel Behavior - Contexts and Boundaries"},signatures:"Enrique Marinao",authors:[{id:"207589",title:"Dr.",name:"Enrique",middleName:null,surname:"Marinao",slug:"enrique-marinao",fullName:"Enrique Marinao"}]},{id:"58085",title:"Energy-Efficient Architecture and Sustainable Urban Tourism: Context, Challenges and Solution",slug:"energy-efficient-architecture-and-sustainable-urban-tourism-context-challenges-and-solution",totalDownloads:1363,totalCrossrefCites:0,totalDimensionsCites:0,abstract:"Urban tourism, as well as tourism in general, offers great economic opportunities, while at the same time, it increases the destination’s vulnerability to overcrowding and uncontrolled growth. Tourism can and should support sustainable urban development. Sustainable urban tourism and energy efficient architecture are interdependent. Increased stakeholder participation, regional cooperation, sustainable urban mobility, supporting environmental and social innovation, preventing negative social issues, resource efficiency and environmentally acceptable waste management, followed by sustainable hospitality industry architecture, are key drivers for sustainable urban tourism success. Energy-efficient architecture in sustainable urban tourism requires application of energy-efficient concepts, elements and systems. Although considerable effort has been put into raising awareness about the necessity of sustainable urban tourism development, numerous examples of “greenwashing” effect have been detected.",book:{id:"6102",slug:"mobilities-tourism-and-travel-behavior-contexts-and-boundaries",title:"Mobilities, Tourism and Travel Behavior",fullTitle:"Mobilities, Tourism and Travel Behavior - Contexts and Boundaries"},signatures:"Ksenija (Née Jovović) Štahan",authors:[{id:"207037",title:"Dr.",name:"Ksenija",middleName:null,surname:"Stahan",slug:"ksenija-stahan",fullName:"Ksenija Stahan"}]}],onlineFirstChaptersFilter:{topicId:"269",limit:6,offset:0},onlineFirstChaptersCollection:[],onlineFirstChaptersTotal:0},preDownload:{success:null,errors:{}},subscriptionForm:{success:null,errors:{}},aboutIntechopen:{},privacyPolicy:{},peerReviewing:{},howOpenAccessPublishingWithIntechopenWorks:{},sponsorshipBooks:{sponsorshipBooks:[],offset:0,limit:8,total:null},allSeries:{pteSeriesList:[],lsSeriesList:[],hsSeriesList:[],sshSeriesList:[],testimonialsList:[]},series:{item:{id:"25",title:"Environmental Sciences",doi:"10.5772/intechopen.100362",issn:"2754-6713",scope:"\r\n\tScientists have long researched to understand the environment and man’s place in it. The search for this knowledge grows in importance as rapid increases in population and economic development intensify humans’ stresses on ecosystems. Fortunately, rapid increases in multiple scientific areas are advancing our understanding of environmental sciences. Breakthroughs in computing, molecular biology, ecology, and sustainability science are enhancing our ability to utilize environmental sciences to address real-world problems.
\r\n\tThe four topics of this book series - Pollution; Environmental Resilience and Management; Ecosystems and Biodiversity; and Water Science - will address important areas of advancement in the environmental sciences. They will represent an excellent initial grouping of published works on these critical topics.
\r\n\tScientists have long researched to understand the environment and man’s place in it. The search for this knowledge grows in importance as rapid increases in population and economic development intensify humans’ stresses on ecosystems. Fortunately, rapid increases in multiple scientific areas are advancing our understanding of environmental sciences. Breakthroughs in computing, molecular biology, ecology, and sustainability science are enhancing our ability to utilize environmental sciences to address real-world problems.
\r\n\tThe four topics of this book series - Pollution; Environmental Resilience and Management; Ecosystems and Biodiversity; and Water Science - will address important areas of advancement in the environmental sciences. They will represent an excellent initial grouping of published works on these critical topics.
\r\n\tPollution is caused by a wide variety of human activities and occurs in diverse forms, for example biological, chemical, et cetera. In recent years, significant efforts have been made to ensure that the environment is clean, that rigorous rules are implemented, and old laws are updated to reduce the risks towards humans and ecosystems. However, rapid industrialization and the need for more cultivable sources or habitable lands, for an increasing population, as well as fewer alternatives for waste disposal, make the pollution control tasks more challenging. Therefore, this topic will focus on assessing and managing environmental pollution. It will cover various subjects, including risk assessment due to the pollution of ecosystems, transport and fate of pollutants, restoration or remediation of polluted matrices, and efforts towards sustainable solutions to minimize environmental pollution.
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",annualVolume:11967,isOpenForSubmission:!0,coverUrl:"https://cdn.intechopen.com/series_topics/covers/39.jpg",editor:{id:"137040",title:"Prof.",name:"Jose",middleName:null,surname:"Navarro-Pedreño",fullName:"Jose Navarro-Pedreño",profilePictureURL:"https://s3.us-east-1.amazonaws.com/intech-files/0030O00002bRAXrQAO/Profile_Picture_2022-03-09T15:50:19.jpg",institutionString:"Miguel Hernández University of Elche, Spain",institution:null},editorTwo:null,editorThree:null,editorialBoard:[{id:"177015",title:"Prof.",name:"Elke Jurandy",middleName:null,surname:"Bran Nogueira Cardoso",fullName:"Elke Jurandy Bran Nogueira Cardoso",profilePictureURL:"https://s3.us-east-1.amazonaws.com/intech-files/0030O00002bRGxzQAG/Profile_Picture_2022-03-25T08:32:33.jpg",institutionString:"Universidade de São Paulo, Brazil",institution:null},{id:"211260",title:"Dr.",name:"Sandra",middleName:null,surname:"Ricart",fullName:"Sandra Ricart",profilePictureURL:"https://mts.intechopen.com/storage/users/211260/images/system/211260.jpeg",institutionString:null,institution:{name:"University of Alicante",institutionURL:null,country:{name:"Spain"}}}]},{id:"40",title:"Ecosystems and Biodiversity",keywords:"Ecosystems, Biodiversity, Fauna, Taxonomy, Invasive species, Destruction of habitats, Overexploitation of natural resources, Pollution, Global warming, Conservation of natural spaces, Bioremediation",scope:"