Common source of ore minerals of the metal(loid)s.†
1. Introduction
The average concentrations of metal or metalloid referred as metal(loid) hereafter, except those of radioisotopes or daughter nuclides and inert gases, have remained virtually unchanged in the earth’s crust despite the ups and downs in the overall distribution [1]. The total element content in the earth’s crust is dominated by O, Si, Al, Fe, Ca, Na, K, Mg, P, and Ti representing ≥99%, while the other elements in the periodic table comprised the remaining 1% and are termed as “trace elements” [2]. The abundances of naturally occurring metal(loid)s in the earth’s crust, also known as
Ore minerals | Associated metalloids |
---|---|
Argentite (Ag2S), PbS | Ag, Au, Cu, Sb, Zn, Pb, Se, Te |
Arsenopyrite (FeAsS), AsS | As, Au, Ag, Sb, Hg, U, Bi, Mo, Sn, Cu |
Barite (BaSO4) | Ba, Pb, Zn |
Sphalerite (ZnS) | Cd, Zn, Pb, Cu |
Cobaltite ((Co, Fe) AsS) | Co, Fe, As, Sb, Cu, Ni, Ag, U |
Chromite (Fe, Cr2O4) | Cr, Ni, Co |
Bornite (Cu5FeS4), chalcocite (Cu2S), chalcopyrite (CuFeS2) | Cu, Zn, Pb, Cd, As, Se, Sb, Ni, Pt, Mo, Au, Te |
Cinnabar (HgS) | Hg, Sb, Se, Te, Ag, Zn, Pb, Mn |
Pyrolusite (MnO2) | Mn, Co, Ni, Zn, Pb |
Molybdenite (MoS2) | Mo, Cu, Re, W, Sn |
Galena (PbS) | Pb, Ag, Zn, Cu, Cd, Sb, Tl, Se, Te |
Stibnite (Sb2S3) | Sb, Ag, Au, Hg, As |
Cassiterite (SnO2) | Sn, Nb, Ta, W, Rb |
Uraninite (UO2) | U, V, As, Mo, Se, Pb, Cu, Co, |
Vanadinite (Pb5(VO4)3Cl) | V, U, Pb |
Wolframite ((Fe, Mn) WO4) | W, Mo, Sn, Nb |
Sphalerite (ZnS), smithsonite (ZnCO3) | Zn, Cd, Cu, Pb, As, Se, Sb, Ag, In |
The changes in both distribution and abundances of metal(loid)s in the ecosphere have become catastrophically high in recent decades presumably attributable to a wide range of anthropogenic inputs [2]. The anthropogenic emission of the toxic metal(loid)s into the atmosphere is estimated to be the one-to-three order of magnitude higher than the natural fluxes [7]. Soil, an ecosphere compartment, is the primary sink for metal(loid)s released into the environment by anthropogenic activities, which often persist for an indefinite period as most metal(loid)s resist the microbial or chemical degradation [8, 9]. Metal(loid)s are usually adsorbed by the organic, inorganic, or colloidal constituents of soil, e.g., humus, hydrous oxides, and hydroxides of Al, Fe, or Mn and Al, phyllosilicates, and some sparingly soluble calcium salts [10]. However, the anthropogenic contaminants such as ash, mine waste, demolition rubble, and so forth can serve as the parent material of a nonnatural soil type, namely, Anthrosols [2], which should have different metal accumulation characteristics than the natural pedogenic soils. The anthropogenic metal(loid)s in soils might have increased mobility than those from pedogenic or genic origins [11]. The metal(loid) contamination of soil is colorless, odorless, and barely noticeable as the environmental impact is not expeditious. The ecological damage due to the metal(loid)s triggered when the corresponding bioavailability is above the threshold or there is a change of environmental conditions [12, 13]. Moreover, the impact of contamination is enhanced when multiple metal(loid)s are involved rather than a single species [14]. The magnitude of metal(loid)s concentration in soils depends on the type of exposure and may be varied on different sites. The physicochemical characteristics and the distribution of metal(loid)s diversified based on the interaction with the soils and local transport mechanisms [15, 16]. The adverse effects on soils due to the accumulation of metal(loid)s are summarized in Table 2.
Agricultural effect | Reduction of soil fertility Reduction of nitrogen fixation Increased erosion factor Increasing soil loss Increase nutrient deficiency Reduction of crop yields Imbalance in the soil biota (flora, fauna, microorganism) Decrease of soil biodiversity |
Industrial effect | Transfer of dangerous chemicals Ecological imbalance Release of pollutant gases Increased salinity |
Urban effect | Clogging of the drains Soil deposits Flooding areas Health problems Contamination of drinking water sources Problems of waste management |
The environmental and geochemical changes of soils as a result of the intrusion of metal(loid)s not only affect the safety of living beings but also hamper the sustainable development due to the impact on the economic or political considerations [17]. Moreover, natural attenuation is often ineffective to eliminate the excess metal(loid)s from the soil, while the remediation process requires high cost and long duration in most instances [13]. Hence, it is necessary to estimate the variation in metal(loid) abundances of soils, which are susceptible to anthropogenic exposure, continuously or even periodically to avoid foreseeable mandatory soil cleanup requirements. The protocols for the assessment of metal(loid) contamination of soils will be discussed in the current chapter, preceded with a brief overview of the sources and toxicity impacts of metal(loid)s in soils.
2. Potentially toxic metal(loid)s
Metal(loid)s, which are ubiquitous in natural soil, and described to have influence on the physiological functions of living beings, e.g., plants, and other organisms, can be classified as nutritionally essential, nonessential with a possible beneficial effect, or nonessential with no beneficial effects [18] as listed in Table 3. The nonessential elements are potentially toxic even at deficient concentrations, while the essential ones can exert harmful impacts at elevated levels [19]. Metal(loid)s, those evoke health concerns, when accumulated in soils, exert chronic toxic effects on humans and other living beings usually via food-chain transfer. However, acute metal(loid) poisoning, even though rare, might also occur through ingestion, inhalation, or dermal contact. The toxicokinetics and toxicodynamics of metal(loid)s depend on several factors, e.g., route of exposure, dose, chemical speciation, solubility, and biotransformation, including the age, gender, and nutritional status of the exposed individuals [20]. Moreover, co-exposure to metal(loid)s mixtures may produce additive, antagonistic, or synergistic toxic effects, which could be more severe at both relatively high-dose and low-dose levels [21, 22].
Nutritionally essential metal(loid)s | Metal(loid)s with possible beneficial effects | Metal(loid)s with no known beneficial effects |
---|---|---|
Cobalt | Boron | Aluminum |
Chromium(III) | Nickel | Antimony |
Copper | Silicon | Arsenic |
Iron | Vanadium | Barium |
Manganese | Beryllium | |
Molybdenum | Cadmium | |
Selenium | Lead | |
Zinc | Mercury | |
Silver | ||
Strontium | ||
Thallium |
An analysis of published data indicates that As, Cd, Cr, Pb, and Hg are systemic toxicants among the metal(loid)s [20], which are known to induce adverse health effects in humans ranging from dermatological, gastrointestinal, neurologic, hematologic, immunologic, metabolic, nephrotic, developmental, and behavioral disorders to cancers [23, 24, 25]. The As, Cd, Cr, Pb, or Hg might also interfere metabolically with the nutritionally essential metal(loid)s, such as Fe, Ca, Cu, and Zn [26, 27]. The ecotoxicological considerations expanded the list of hazardous elements including a total of 11 metal(loid)s (As, Ba, Cd, Cr, Cu, Hg, Ni, Sb, Se, Tl, and V) [28]. The US-EPA priority pollutant list [29], however, included Ag, Be, Pb, and Zn in the list of toxic metal(loid)s and excluded Ba and V.
3. Assessment of soil contamination by metal(loid)s
A soil system is “contaminated” if any or more than a few of the toxic metal(loid) are present where it should not be or above the designated “background” concentrations [30, 31]. However, the definition of the term “background” is yet to be defined universally [6], and a selective list of definitions used to define the “background” conditions are listed in Table 4. A critical evaluation of “background” definitions [32] revealed that a precise global background value for an individual metal(loid) could not be proposed because there have been ups and downs in the overall natural distribution metal(loid)s in the ecosphere. Hence, it should be limited to specific geographic locations or regions and should be considered as a range instead of an absolute value to deal with the unavoidable environmental heterogenicity [32, 33, 34]. The regional “background” values of metal(loid)s represent either off-site or on-site reference locations. The off-site “background” values, as derived from real sample measurements [35, 36], often do not have sufficient metadata to validate the data accuracy [37] and also do not include the impact of transboundary atmospheric transport of metal(loid)s [38, 39]. The on-site “background” values usually represent buried fossil topsoils [40], dated peat bog samples [41], or deep soil layer from the same soil profile [42, 43]. However, the buried topsoils might subsequently be depleted by pedogenetic processes [44], and the properties of deep soil layers, e.g., organic matter content, bulk density, and so forth, are different from those of top soils [39, 45].
The methods used for soil contamination assessment include both statistical and geochemical methods, which are critically evaluated by several researchers, e.g., Desaules [39], Morrow et al. [48], D’Amore et al. [49], Weissmannová and Pavlovský [50], Cai et al. [51], Mizutani et al. [52], and so forth.
4. Conclusion
Metals in soil induce long-term risks to the ecosystems. Dynamics of metals in ecosphere can be assessed precisely using the information on the interactions of metals with environmental compartments. Evaluation of total metal content in soil and comparison with the “background” concentrations are the basic idea to deduce the anthropogenic inputs. However, there are differences in opinion regarding the test methods, definitions of “background,” or approaches in data interpretation for the assessment of soil contamination. Hence, it might require more time to unify the understanding of soil contamination with metals.
References
- 1.
Kabata-Pendias A. Trace Elements in Soils and Plants. 4th ed. Boca Raton, FL: CRC Press; 2010 - 2.
Alloway BJ. Sources of heavy metals and metalloids in soils. In: Alloway BJ, editor. Heavy Metals in Soils: Trace Metals and Metalloids in Soils and their Bioavailability. Dordrecht: Springer Netherlands; 2013. pp. 11-50 - 3.
Hans Wedepohl K. The composition of the continental crust. Geochimica et Cosmochimica Acta. 1995; 59 :1217-1232 - 4.
Tan L, Chi-lung Y. Abundance of chemical elements in the earth’s crust and its major tectonic units. International Geology Review. 1970; 12 :778-786 - 5.
Taylor SR, McLennan SM. The geochemical evolution of the continental crust. Reviews of Geophysics. 1995; 33 :241-265 - 6.
Wu J, Teng Y, Lu S, Wang Y, Jiao X. Evaluation of soil contamination indices in a mining area of Jiangxi, China. PLoS One. 2014; 9 :e112917 - 7.
Sposito G, Page AL. Cycling of metal ions in the soil environment. In: Sigel H, Sigel A, editors. Metal Ions in Biological Systems. Circulation of Metals in the Environment. Vol. 18. New York: Marcel Dekker; 1984. pp. 287-332 - 8.
Adriano DC. Trace Elements in Terrestrial Environments: Biogeochemistry, Bioavailability, and Risks of Metals. New York: Springer; 2001 - 9.
Kirpichtchikova TA, Manceau A, Spadini L, Panfili F, Marcus MA, Jacquet T. Speciation and solubility of heavy metals in contaminated soil using X-ray microfluorescence, EXAFS spectroscopy, chemical extraction, and thermodynamic modeling. Geochimica et Cosmochimica Acta. 2006; 70 :2163-2190 - 10.
Young SD. Chemistry of heavy metals and metalloids in soils. In: Alloway BJ, editor. Heavy Metals in Soils: Trace Metals and Metalloids in Soils and their Bioavailability. Dordrecht: Springer Netherlands; 2013. pp. 51-95 - 11.
Chlopecka A, Bacon JR, Wilson MJ, Kay J. Forms of cadmium, lead, and zinc in contaminated soils from southwest Poland. Journal of Environmental Quality. 1996; 25 :69-79 - 12.
Su C, Jiang L, Zhang W. A review on heavy metal contamination in the soil worldwide: Situation, impact and remediation techniques. Environmental Skeptics and Critics. 2014; 3 :24-38 - 13.
Wood JM. Biological cycles for toxic elements in the environment. Science. 1974; 183 :1049-1052 - 14.
Yongsheng Q. Study on the influences of combined pollution of heavy metals Cu and Pb on soil respiration. Journal of Anhui Agricultural Sciences. 2008; 36 :1117-1128 - 15.
Dermont G, Bergeron M, Mercier G, Richer-Laflèche M. Metal-contaminated soils: Remediation practices and treatment technologies. Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management. 2008; 12 :188-209 - 16.
Dermont G, Bergeron M, Mercier G, Richer-Lafleche M. Soil washing for metal removal: A review of physical/chemical technologies and field applications. Journal of Hazardous Materials. 2008; 152 :1-31 - 17.
Alekseenko V, Alekseenko A. The abundances of chemical elements in urban soils. Journal of Geochemical Exploration. 2014; 147 :245-249 - 18.
Goyer R, Golub M, Choudhury H, Hughes M, Kenyon E, Stifelman M. Issue paper on the human health effects of metals. Risk Assessment Forum. Washington, DC: U.S. Environmental Protection Agency; 2004 - 19.
Alloway BJ. Heavy Metals in Soils: Trace Metals and Metalloids in Soils and their Bioavailability. Dordrecht: Springer Netherlands; 2013 - 20.
Tchounwou PB, Yedjou CG, Patlolla AK, Sutton DJ. Heavy metal toxicity and the Environment. In: Luch A, editor. Molecular, Clinical and Environmental Toxicology: Volume 3: Environmental Toxicology. Basel: Springer Basel; 2012. pp. 133-164 - 21.
Wang G, Fowler BA. Roles of biomarkers in evaluating interactions among mixtures of lead, cadmium and arsenic. Toxicology and Applied Pharmacology. 2008; 233 :92-99 - 22.
Nordberg GF, Jin T, Hong F, Zhang A, Buchet JP, Bernard A. Biomarkers of cadmium and arsenic interactions. Toxicology and Applied Pharmacology. 2005; 206 :191-197 - 23.
IARC. Report on the ‘Meeting of the International Agency for Research on Cancer (IARC) working group on beryllium, cadmium, mercury and exposures in the glass manufacturing industry’ Scandinavian Journal of Work, Environment and Health. 1993; 19 :360-363 - 24.
Begum ZA, Rahman IMM, Hasegawa H. Soil Remediation with Green Chelants. Scholars’ Press. Germany: Saarbrücken; 2015 - 25.
NTP (National Toxicology Program). “Report on carcinogens”. North Carolina: U.S. Department of Health and Human Services Research Triangle Park; 2016 - 26.
Alonso ML, Montaña FP, Miranda M, Castillo C, Hernández J, Benedito JL. Interactions between toxic (As, Cd, Hg and Pb) and nutritional essential (Ca, Co, Cr, Cu, Fe, Mn, Mo, Ni, Se, Zn) elements in the tissues of cattle from NW Spain. Biometals. 2004; 17 :389-397 - 27.
Abdulla M, Chmielnicka J. New aspects on the distribution and metabolism of essential trace elements after dietary exposure to toxic metals. Biological Trace Element Research. 1989; 23 :25-53 - 28.
Vodyanitskii YN. Contamination of soils with heavy metals and metalloids and its ecological hazard (analytic review). Eurasian Soil Science. 2013; 46 :793-801 - 29.
US EPA. The Clean Water Act (Priority Pollutants: Appendix A to 40 CFR Part 423). Washington, D.C.: United States Environmental Protection Agency; 2012 - 30.
US EPA. Terms of Environment: Glossary, Abbreviations, and Acronyms. Washington, D.C.: United States Environmental Protection Agency; 1997 - 31.
Chapman PM. Adaptive monitoring based on ecosystem services. Science of the Total Environment. 2012; 415 :56-60 - 32.
Reimann C, Filzmoser P, Garrett RG. Background and threshold: Critical comparison of methods of determination. Science of the Total Environment. 2005; 346 :1-16 - 33.
Edelman T, de Bruin M. Background values of 32 elements in Dutch topsoils, determined with non-destructive neutron activation analysis. In: Assink JW, Van Den Brink WJ, editors. Contaminated Soil. Dordrecht: Springer Netherlands; 1986. pp. 89-99 - 34.
Anderson RH, Kravitz MJ. Evaluation of geochemical associations as a screening tool for identifying anthropogenic trace metal contamination. Environmental Monitoring and Assessment. 2010; 167 :631-641 - 35.
De Temmerman LO, Hoenig M, Scokart PO. Determination of “normal” levels and upper limit values of trace elements in soils. Zeitschrift für Pflanzenernährung und Bodenkunde. 1984; 147 :687-694 - 36.
Ikem A, Campbell M, Nyirakabibi I, Garth J. Baseline concentrations of trace elements in residential soils from Southeastern Missouri. Environmental Monitoring and Assessment. 2008; 140 :69-81 - 37.
Desaules A. The role of metadata and strategies to detect and control temporal data bias in environmental monitoring of soil contamination. Environmental Monitoring and Assessment. 2012; 184 :7023-7039 - 38.
Bindler R, Brännvall M-L, Renberg I, Emteryd O, Grip H. Natural lead concentrations in pristine boreal forest soils and past pollution trends: A reference for critical load models. Environmental Science & Technology. 1999; 33 :3362-3367 - 39.
Desaules A. Critical evaluation of soil contamination assessment methods for trace metals. Science of the Total Environment. 2012; 426 :120-131 - 40.
Elberling B, Breuning-madsen H, Hinge H, Asmund G. Heavy metals in 3300-year-old agricultural soils used to assess present soil contamination. European Journal of Soil Science. 2010; 61 :74-83 - 41.
Shotyk W, Blaser P, Grünig A, Cheburkin AK. A new approach for quantifying cumulative, anthropogenic, atmospheric lead deposition using peat cores from bogs: Pb in eight Swiss peat bog profiles. Science of the Total Environment. 2000; 249 :281-295 - 42.
Blaser P, Zimmermann S, Luster J, Shotyk W. Critical examination of trace element enrichments and depletions in soils: As, Cr, Cu, Ni, Pb, and Zn in Swiss forest soils. Science of the Total Environment. 2000; 249 :257-280 - 43.
Bourennane H, Douay F, Sterckeman T, Villanneau E, Ciesielski H, King D, et al. Mapping of anthropogenic trace elements inputs in agricultural topsoil from Northern France using enrichment factors. Geoderma. 2010; 157 :165-174 - 44.
ISO. ISO 19258: 2005 (Soil quality—Guidance on the determination of background values). Geneva: International Organization for Standardization; 2005 - 45.
Reimann C, de Caritat P. Distinguishing between natural and anthropogenic sources for elements in the environment: Regional geochemical surveys versus enrichment factors. Science of the Total Environment. 2005; 337 :91-107 - 46.
Salminen R, Gregorauskien V. Considerations regarding the definition of a geochemical baseline of elements in the surficial materials in areas differing in basic geology. Applied Geochemistry. 2000; 15 :647-653 - 47.
Reimann C, Filzmoser P. Normal and lognormal data distribution in geochemistry: Death of a myth. Consequences for the statistical treatment of geochemical and environmental data. Environmental Geology. 2000; 39 :1001-1014 - 48.
Morrow DA, Gintautas PA, Weiss AD, Piwoni MD, Bricks RM. Metals Speciation in Soils: A Review of Methodologies (Technical Report IRRP-96-5). Washington, DC: U.S. Army Corps of Engineers; 1996 - 49.
D’Amore JJ, Al-Abed SR, Scheckel KG, Ryan JA. Methods for speciation of metals in soils. Journal of Environmental Quality. 2005; 34 :1707-1745 - 50.
Weissmannová HD, Pavlovský J. Indices of soil contamination by heavy metals—Methodology of calculation for pollution assessment (minireview). Environmental Monitoring and Assessment. 2017; 189 :616 - 51.
Cai C, Xiong B, Zhang Y, Li X, Nunes LM. Critical comparison of soil pollution indices for assessing contamination with toxic metals. Water, Air, and Soil Pollution. 2015; 226 :352 - 52.
Mizutani S, Ikegami M, Sakanakura H, Kanjo Y. Test methods for the evaluation of heavy metals in contaminated soil. In: Hasegawa H, Rahman IMM, Rahman MA, editors. Environmental Remediation Technologies for Metal-Contaminated Soils. Tokyo: Springer Japan; 2016. pp. 67-97 - 53.
Hawkes HE, Webb JS. Geochemistry in Mineral Exploration. New York: Haper & Row; 1962 - 54.
ISO. ISO 11074: 2015 (Soil quality—Vocabulary). Geneva: International Organization for Standardization; 2015