Remediation of Soil Impacted by Heavy Metal Using Farm Yard Manure, Vermicompost, Biochar and Poultry Manure

Abstract

Soil contamination by organic and inorganic compounds is a universal concern nowadays. One such contamination is heavy metal exposure to the soil from different sources. The discharge of effluents from various factories in Punjab like tanning industries, leather industries, and electroplating industries generate a large volume of industrial effluents. These industrial units discharge their effluents directly or through the sewer into a water tributary (Buddha Nallah) and this water is being used for irrigating the crops. The heavy metals enter into the food chain thus contaminating all resources i.e. air, soil, food, and water. Preventive and remedial measures should be taken to reduce the effects of heavy metals from soil and plants. Organic soil amendments like FYM, Vermicomposting, Biochar, and poultry manure have been used to deactivate heavy metals by changing their forms from highly bioavailable forms to the much less bioavailable forms associated with organic matter (OM), metal oxides, or carbonates. These amendments have significant immobilizing effects on heavy metals because of the presence of humic acids which bind with a wide variety of metal(loid)s including Cd, Cr, Cu, and Pb.

1. Introduction

Heavy metals are found naturally in the Earth’s crust. Any metals and metalloids with an atomic density greater than 4 g cm³ [1] and toxic at low concentrations are considered heavy metals. They cannot be destroyed or degraded. Mercury (Hg), thallium (Tl), lead (Pb), chromium (Cr), arsenic (As) and cadmium (Cd) are some examples of heavy metals. Heavy metals like (e.g., Copper, selenium, and zinc) are required to keep the metabolism of human body. At higher concentrations, they can cause poisoning. They enter into human bodies through drinking water, food and breathing. Industrial, consumer waste, and acid rain breaks the soil particles and releases heavy metals into water bodies like streams, reservoirs, rivers, and groundwater resulting in heavy metal contamination of water supplies. Heavy metals have several potentially harmful side effects. They can find their way into the environment in various ways and are dangerous due to their accumulation for bioaccumulation.

While comparing the chemical’s concentration in the atmosphere, bioaccumulation refers to a rise in the attention of a chemical in a biological organism over time. As molecules are taken up and broken down (metabolized) or discharged and accumulates in living things. As a result, toxicity symptoms may occur due to contaminated potable water, high atmospheric air concentrations near pollution sources, or ingestion through the foods etc.

There are two distinct categories of heavy metals and can be classified into: (i) elements that are necessary for plant growth are B, Cu, Fe, Mo, Ni, and Zn although poisonous to plants and animals if their concentrations reach definite approach. The difference between recommended and harmful levels for many of these elements is minimal; (ii) elements are unnecessary for animals or plants, such as As, Cd, Hg, and Pb. M, land application of treated wastewater (TWW), fertilizers, sewage sludge and manufacturing practices are sources of heavy metals in soils [2].

Heavy metal pollution in the soil is now a global environmental problem that has captivated public interest, owing to growing concerns about protecting agricultural products. Natural processes originating from parent sources and anthropogenic practices bring these components into the soil agro-ecosystem. Because of the potential for accumulation across the food chain, heavy metal exposure presents a significant risk to the public health and well-being of animals and humans. To solve the issue, physical, chemical, and biological remediation approaches have been used.

2. Origin of heavy metal contamination

Heavy metals are found generally in soil due to bioturbation, degradation and weathering of parent materials in small concentrations are considered as trace (less than 1000 mg kg⁻¹) but very occasionally toxic [3, 4]. As a consequence of man’s destruction and amplification of essence’s slowly developing geochemical cycle, soils often accumulate heavy metals above-established background values which are sufficient to pose a risk to human health, livestock, crops, and other media [5].

Heavy metals eventually set off pollutants in the environment when:

1. The rates of production of these metals through artificial cycles become faster as compared to natural processes.

2. They are transported from mines to numerous places in the field where there is a greater risk of direct exposure.

3. Compared to those from the receiving area, concentrations of metals indisposed of goods are comparatively high.

4. The chemical form of metal in the receiving environment system makes it much more bioavailable [5].

The significant sources contributing to heavy metal accumulation in our ecosystems are:

2.1 Fertilizers

Plants needs both macronutrients and micronutrients to develop and complete their life cycle. Heavy metals (like Co, Cu, Fe, Mn, Mo, Ni, and Zn) required for plant growth and development [6] are insufficient in certain soils and can be applied as a foliar spray or soil application in fields. In intensive farming systems, substantial amount of fertilizers is used frequently to provide plants with adequate nutrients for plant growth development. However, few heavy metals such as Cd and Pb are present as impurities in the compounds used to supply essential elements, and regular application of fertilizer can remarkably boost their concentration into the soil [7]. Lead and cadmium are known to have little or no physiological activity. Phosphorus containing fertilizers unintentionally introduce Cd and some other certainly harmful elements [such as iron (F), mercury (Hg), and (Pb)] to the soil [8].

2.2 Pesticides

In historical agriculture and horticulture, several prevalent insecticides had a considerable amount of metal concentrations. For example, around 10 percent of the chemicals licensed are used as fungicides and insecticides in the United Kingdom in recent years were based on compounds containing Manganese (Mn), Copper (Cu), Zinc (Zn), Hg, and Pb. Fungicidal sprays containing Cu, for instance, Bordeaux mixture (copper sulfate) and copper oxychloride [7], are examples of such pesticides. For many years, lead arsenate was employed in fruit orchards to control parasitic insects. Compounds that contain arsenic have also been widely used to prevent livestock ticks and bananas in New Zealand and Australian countries, where wood timber has been conserved with Cu, Cr, and Arsenic (CCA) formulations. Many abandoned sites now surpass the background concentrations of the soil of these elements. Such pollution may lead to problems, significantly when areas are restored for agricultural or non-agricultural activities. The usage of such materials was more confined, restricted to specific sites or crops than fertilizers [9].

2.3 Manures and biosolids

Inadvertently, the manures application (e.g., animal manures or municipal sewage loam) onto the soil results in the build-up of heavy metals like chromium (Cr), arsenic (As), Cu, mercury (Hg), cadmium (Cd), lead, nickel (Ni), selenium (Se) and molybdenum (Mo) [10]. Some animal wastes like poultry, cattle, or pig dung produced in farming are often used as solids and slurries on crops and pastures [11]. While most manures are regarded as helpful fertilizers, Zn or Cu are given in diets as growth enhancers and added as supplements could have the capacity to bring about metal pollution of the soil, livestock and poultry industries [11, 12]. Manures produced by animals consuming those diets have significant concentrations of Zn, As, and Cu, leading to the substantial accumulation of heavy metals in the soil if it is frequently applied to restricted sections of land.

Biosolids are predominantly waste materials having organic origin created by wastewater treatment procedures that can also be reused to benefit the environment [13]. Biosolids materials are applied to the soil in many countries to reuse the biosolids produced by urban populations [14]. More than 30% of the wastewater is used as a fertilizer in the farming sector in the European Community [15]. Approximately 2.8 MT of dry sewage sludge utilized or get rid of per annum in the United States is anticipated to be land applied, and biosolids are utilized in agriculture throughout the country.

The possibility of composting biosolids with other organic substances like sawdust, stroke, or garden waste is also of considerable curiosity. Biosolids’ potential to contaminate the soils with heavy metals has prompted widespread review about their usage in agricultural sector [16]. The most frequent heavy metals in these are Zn, Cd, Cu, Ni, Cr, and Pb, and the metal content depend on the nature, intensity, and techniques used to treat biosolids [17]. These metals applied to soils as part of biosolids treatments can seep into the soil profile and pollute groundwater in certain conditions [18]. For example, increased amounts of Zn, Ni, and Cd in drainage leachates have been found in recent investigations on certain New Zealand soil amended with biosolids [19, 20].

2.4 Wastewater

Municipal and polluted wastewater is being applied to agricultural land for over four 100 years, a prevalent exercise in many sections of the world [21]. Such liquid waste is being used to irrigate 20 million hectares of agricultural land around the world. As per studies, wastewater irrigation-based agriculture is responsible for 50% of the vegetable supply to metropolitan parts in many African and Asian cities. Farmers are unconcerned about environmental impact or consequences and only focus on enhancing their production and profitability. Irrigation with such water leads to accumulation of heavy metal in the soil even though metals in industrial wastewaters are typically low.

2.5 Mining of metal, milling processes and industrial wastes

Across many countries have been vouchsafed by the mining and milling of metals and the fabrication, the legacy of vast disseminating pollutants of metal contamination in soil. At the time of mining, the residues of ores are straightaway released into natural depressed geologic formation and swamps, resulting in upraised contents [22]. Voluminous mining and smelting of Zn and Pb, thus polluting the soil, risk ecological and human health risks. Furthermore, various recovery methods applied at these sites can be long and exorbitant, and soil productivity may not be restored. Comprehend pathways comprise the absorption of plant material being grown in or direct absorption of polluted soil [10].

More materials are produced by diverse industries like petrochemicals, textile, tanning by fortuitous oil spills, petroleum-based products being used, pesticides, and pharmaceutical provisions significantly fluctuating in the constitution. Though some are inclined of on land, some have suitable for forestry or agriculture. Moreover, numerous are certainly precarious due to their concentration of weighty metals (Zn, Pb, and Cr) or poisonous biological compounds that are rarely, if by any chance, used on land. Rest are highly deprived of nutrients or possess no soil improving properties [11].

2.6 Airborne sources/origins

Metals can be found in the air due to stack or duct emissions of air, gas, or vapor streams, as well as fugitive emissions including dust from warehouses or garbage dumps. Metals emitted from the air are usually discharged as particles in the gas stream. Following high-temperature processing, several metals, such as Pb, Cd, and As, can also volatilize. Natural air currents can also disperse stack emissions over a large area until they are removed from the gas stream by dry and wet precipitation processes.

Agricultural lands near smelting sites have been discovered to have very high levels of Cd, Pb, and Zn. Airborne emissions of Pb from the combustion of fuel including tetraethyl lead are yet another major cause of soil pollution; this contributes significantly to the Pb concentration in urban areas. Tires, lubricating fluids are two sources of Cd and Zn that can be introduced into soils near highways [23].

3. Organic soil amendments

Organic soil amendments have been widely used to binding heavy metals by changing their forms from initially highly bioavailable forms to the much less bioavailable fractions associated with organic matter (OM), metal oxides, or carbonates [24]. These amendments have significant binding effects on heavy metals because it contains humic acids which bind with a wide variety of metal(loid)s including Cd, Cr, Cu, and Pb [25]. The commonly used soil amendments which are organic in nature are composts of different origins, manures, sawdust, sewage sludge, and wood ash [26]. The two major advantages of these amendments as compared to other soil amendments are relative of lower cost and they commonly facilitate the re juvination of contaminated soils. However, the residual effect of organic amendments on metal solubility should also be considered. Metal extraction depends upon the original OM content, the soil type, and the rate of OM transformation over time [27]. This is the important consideration that addition of a single organic amendment results in the production of many different organic substances. This is because, during the break down of organic matter, various organic acids are released which may alter metal availability [28]. Increased decomposition of OM decreased the surface area and CEC, this is due to an increase in dissolved organic carbon which results in the release of metals [29, 30]. Thus the nature and stability of OM amendments are also important for determining the long-term partitioning of metals between the solution and the solid phase. Various organic manures are used for remediation purposes like FYM, vermicompost, biochar and Poultry manure. In this chapter, the effect of organic manures on the remediation of heavy metal contaminated soils will be discussed one by one. Let us discuss them one by one:

3.1 Farm yard manure

Various organic amendments were used to remediate heavy metal contaminated soils like farm yard manure and composted organic amendments, The effect of organic manures to be applied depends upon the nature, mobility, and the bioavailability of metal, its microbial decomposition, and its further effects on soil chemical and physical proprieties [31]. Using amendments in contaminated soils, metal Immobilization is a remediation measure that decreases mobility and phytoavailability of metals in the soils and their plant uptake [32]. It is being used by farmers as source of nutrition to field crops. Low availability of this manure is a major problem on its use as a source of nutrients. FYM controls the production of crop and maintain properties of soil and it can be used to decrease heavy metal stress in plants. The FYM, pig and cow manure decreased available Ni content in soil due to the formation of strong metal complexes with OM [33]. In sandy loam soil, application of FYM significantly reduced Cd and Pb content in the shoots and roots of Amaranth [34]. Due to increased soil pH, complexation of metal with OM and co-precipitation with P content, the metal concentration in tissues of plants for metals (Cu, Zn, and Pb) will be decreased in Chenopodium album L. compared to plants grown in compost treated soil or a control soil. A pot experiment was conducted for remediation of Cr in Maize- Indian mustard rotation in two soils (contaminated and uncontaminated soil), the uncontaminated soil was artificially contaminated with Cr levels up 320 mg kg⁻¹ soil and two amendments (FYM and lime) were used for remediation purpose and found that FYM was the best amendment for reducing the toxicity of chromium [35]. In calcareous contaminated soils, the uptake of Zn, Pb, and Cu in Greek Cress will be decreased by 16, 54, and 21%, respectively by application of green waste compost [36]. In wheat, the toxicity of Cd will be reduced by more than 50% by compost application thus decreasing Cd uptake in wheat tissue and hence regulates wheat growth which is primarily attributed to an increase in surface charges [37] and adsorption of metal onto metal-binding compounds such as phosphates and carbonates [38]. Compost contaminated soils may increase the mobility of metals like As [39]. Due to dissolved organic carbon competing with As for sorption sites and a significant soluble P component, a large increase in leachable As from soil amended with compost was observed due to which, As from organic and inorganic binding sites are displaced [40]. On the other hand, biosolid compost has also a positive effect to remediate an arsenic spiked contaminated soil. In the mining and agriculture sector, manures and composted organic amendments have also been used as soil conditioners [41] and the physical properties and nutrient status of mine soils are significantly improved [42]. By aerating, heavy metals are also removed. Aeration helps microorganisms to decompose the pollution by making nutrients available to the plants. Plowing up to lower layers also exposes some pollutants to the sunlight and this can help as well.

3.2 Vermicompost

Vermicompost (VC), the organic input, is produced from various organic wastes. It is a rich source of antibiotics, enzymes, immobilized microflora and various growth hormones like gibberellins which synchronize the growth of plants and microbes. It has the ability to improves the quality of growing plants and also increases growth resulting in improved metal toxicity. Vermicompost is a rich source of nutrients, increases the soil fertility. In contaminated soil, application of vermicompost improves soil physical and chemical characterstics of soils. Heavy metal contaminated soils are also bioremediated with vermicompost and spent mushroom compost. Bioremediation is done through vermiremediation. Vermiremediation is an applied science to get rid of heavy metals from soil. Lumbricus rubellus species were used to separate leachate-contaminated soil which contains various heavy metals [43]. It takes 90 days for its completion and the greatest reduction in the concentration of all heavy metals was approximately 50%. The vermicompost of urban waste also helps to reduce the risk of environmental contamination due to lower metal concentrations available in it [44]. The metal concentrations in earthworm’s internal body were significantly and negatively correlated to heavy metal concentrations in the vermicompost. The higher bioaccumulation factor indicates higher metal accumulation in earthworm’s tissue by which food chain is affected. The accumulation of metals in worm’s tissue, not only remediate the metals from the urban wastes but also improves the quality of vermicompost by reducing the metal concentration. The ability of earthworms to mitigate the toxicity of heavy metals and to increase the nutrient content of organic wastes might be useful in sustainable land restoration practices. Heavy metals can bind with ligands of the tissues and thus lead to their bioaccumulation. The positive correlation was observed between metal concentrations in the earthworms and those in the soils with, which may be due to differences in bioaccumulation factors for different metals. Earthworms have the ability to inhabit and survive in contaminated sites with metals and have the ability to accumulate heavy metals in the cells of yellow tissue. Earthworm populations may develop a mechanism by which they can tolerate or resist the effect of metal-induced stress. Such tolerance is acquired by earthworms either through a variation in their genetic structure or reversible changes in an earthworm’s physiology. Heavy metal pollution negatively affects the life history of earthworms such as growth, reproduction, and survival. The treatment of high phosphorus significantly reduced lead, zinc, and cadmium bioavailability to the earthworm which was due to the formation of metal-phosphate complex in the soils. The vermicompost reduced the ecological risk to soil-inhabiting invertebrates exposed to heavy metal contaminated soils. Earthworms act as an indicator for heavy metal toxicity that is present in the materials and are bio converted, indicating potential environmental hazard [45]. The capacity of earthworms to uptake and redistribute heavy metals in their body leads to a balance between uptake and excretion which helps them to survive in metal contaminated soil and also reported an increase in heavy metal content in the vermicompost of paper mill sludge. The increase was appreciably more for Fe and Cu. The weight and volume reduction due to the breakdown of organic matter during vermicomposting might have been the reason for the increase in heavy metal concentrations in vermicompost. The earthworm L. terrestris had the capacity to accumulate significant levels of zinc, and thus earthworm ingestion may result in zinc transfer to higher trophic levels [46]. Earthworms can also tolerate many heavy metals and pesticides in their body tissues and helps in remediation.

3.3 Biochar

The biochar is highly aromatic, where the functional groups associated with it, which give the biochar a net negative charge, resulting in increased CEC in soil with increased adsorption capacity for both organic and inorganic compounds, and greater nutrient retention. Biochar has a porous body, charged surface, and many different surface functional groups and contains significant amounts of humic and fulvic-like substances [47]. It has also been used to remediate heavy metals from soils and water. Different kinds of biochar derived from plant residues and animal manures are used to reduce the mobility and availability of metal in contaminated soil and water. Mostly biochars are alkaline in nature and released the available form of P, K, and Ca. In general, application of biochar reduced the concentrations of zinc and cadmium by 45 and 300 fold [48]. It is due to sorption mechanism which is used for the withholding of metals by biochars. The Cu leaching was correlated with higher DOC contents [49]. Biochar, when applied to the soil, improves quality and productivity of soil because the oxides, hydroxides, and carbonates present in biochar can act as liming agents [50]. Biochar can reduce soil bulk density and thereby increases water infiltration, soil aeration, root penetration, and increase soil aggregate stability. Biochar spiked soil has soil pH > 7 which is found suitable for the rise of fungal hyphae. Adding higher amounts of biochar to soil increased the environment for microbes, with promoted growth via increased porosity [51]. Therefore, it is critical to consider both soil and biochar properties when it is used for the remediation of salt-affected soils and the source of the feedstock used to produce the biochar which is used as an organic amendment [52]. Generally, biochar application could be recommended as an appropriate amendment for in-situ remediation and immobilization of the heavy metals especially for lead and cadmium in contaminated soils [53].

3.4 Poultry manure

Poultry manure is also used to remediate heavy metals from soil. A study was conducted to study the effectiveness of the adding poultry manure on the bioavailability of trace metals from the contaminated soil after treatment with wastewater [54]. It was applied @ 10 and 20 t ha⁻¹ and found that the addition of manure increased fenugreek biomass and decreased trace metal uptake depending on the combination of composted manures used. Trace metal concentrations in the fenugreek shoots were in the order of Pb > Ni > Zn > Cu > Cd. Soils amended with Poultry litter reduced trace metal concentrations more than composted manure which is true for the plant uptake. It was concluded that following the combined application of composted manure with residues of plant can be effectively used for remediating trace metal concentration in soils and crops. Chicken-manure biochar is used as a soil amendment to immobilize and detoxify heavy metals like cadmium and lead.

Certain plant species are also used to remediate heavy metals. They can accumulate a high amount of heavy metals in upper parts of plants. Indian mustard plant is used for phytoremediation [55]. So, Biocar can also remediate heavy metal toxic soils.

4. Effect of organic manures on soil health

The addition of organic manures to polluted soils has some beneficial effects on soil properties. The most important factor is soil pH that affect solubility of metal, plant nutrient uptake, plant biomass, microbial activity, and many other characteristics [56]. The increase in soil pH, due to manure addition is due to specific adsorption of organic anions on surfaces of hydrous Fe and Al and the simultaneous liberation of hydroxyl ions [57]. Depending upon the compost sources, pH may either increase or decrease. These amendments improved soil physical characteristics such as particle size distribution, cracking pattern, and porosity. Organic amendments are rich source of nutrients like N, P, and other secondary elements like Ca, Mg, and Fe which are required for plant growth and improves the soil fertility status. The essential nutrients in these amendments are in inorganic forms which are released slowly and subjected to leaching loss compared to inorganic fertilizers [58]. The build-up of soil organic matter through the addition of organic manures increased soluble organic carbon, microbial biomass carbon [59], population and species diversity of microorganisms like bacteria [60], soil respiration [61], and the activity of various soil enzymes [62]. The application of organic amendments to soils results in significant improvements in overall soil quality.

5. Conclusion

Heavy metals are detrimental to health issues even at very low concentrations due to their long-term persistence, hence they must be removed from environments to maintain the balance of the ecosystem and human health. As a bioremediation approach, removing heavy metals from the soils by using organic amendments was discussed. Organic amendments are very effective in mitigating the effects of heavy metals from the soil. Hence, the chapter concluded that the application of organic manures like FYM, Vermicomposting, biochar, poultry manure reduced the heavy metal toxicity. Large quantities of organic amendments are used as a source of nutrients and also as a conditioner to improve the soil physical properties and fertility of soils. These organic amendments can be used as a sink for reducing the bioavailability of heavy metals in contaminated soils through their effect on the adsorption, complexation, reduction, and volatilization of metals.