Baligar, Virupax C

He, Zhenli

Shentu, Jiali

Stoffella, Peter J

Yang, Xiaoe

Zhang, Tiequan

Scholarship at UWindsor

Journal of Environmental Indicators, 9:17-18, 2015 Copyright © International Society of Environmental Indicators  Open Access: www.environmentalindicators.net   17 !Heavy Metal Contamination of Soils: Sources, Indicators, and Assessment  HE, Z.,1 SHENTU, J.,2 YANG, X.,3 BALIGAR, V.C.,3 ZHANG, T.4 & STOFFELLA, P.J.1   1 University of Florida, Institute of Food and Agricultural Sciences, Indian River Research and Education Center, Fort Pierce, Florida, USA  2 College of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou, China  3 Ministry of Education Key Laboratory of Environment Remediation and Ecosystem Health, College of Environmental and Resources Science, Zhejiang University at Zijingang, Hangzhou, China 4 USDA-ARS-Beltsville Agricultural Research Center, Beltsville, MD, USA  5 Science and Technology Branch, Agriculture and Agri-Food Canada, Ottawa, Canada   Heavy metals are elements with metallic properties and an atomic mass of > 20. The most common contaminants of heavy metal are Cd, Cr, Hg, Pb, Cu, Zn, and As. Heavy metal contamination to soil and the environment has been accelerated in modern society due to industrialization, rapidly expanded world population, and intensified agriculture. Accumulation of heavy metals often results in soil/water degradation and ecosystem malfunction. Moreover, heavy metals enter food chains from polluted soil, water and air, and consequently cause food contamination, thus posing a threat to human and animal health.  Globally, more than 10 million sites of soil pollution have been reported, with >50% of the sites contaminated with heavy metals and/or metalloids (such as arsenic) (Table 1). Heavy metal pollution has a combined worldwide economic impact estimated to be in excess of US $10 billion per year.   Table 1. Soil pollution in the world (EEC, 2007; ADEC, 2010; EPMC, 2014; USEPA, 2014).  Country Number of pollution sites % of heavy metal(loid)s pollution Global >10000000 >50 USA >100000 >70 European Union >80000 37 Australia >50000 >60 China 1.0 million km2 >80  Sources of heavy metal pollution include natural processes and anthropogenic activities. Soils may inherit heavy metals from parent materials such as those derived from metal-enriched rocks including serpentine and black shale (He et al. 2005). Anthropogenic sources of heavy metal pollution include mining, smelting, fossil fuel combustion, waste disposal, corrosion, and agricultural practices. For instance, irrigation with industrial waste water has resulted in heavy metal pollution to a large area of arable land and simultaneously led to contamination of millions of tons of grain each year in China.  Many biogeochemical properties/parameters have been proposed and applied to indicate soil contamination with heavy metals. They include, but are not limited to: chemical indicators (total/recoverable content, available/extractable amount, and fractionation); biochemical indicators (enzyme activity, FDA hydrolysis); microbial indicators (microbial biomass, microbial quotient, specific respiration, microbial metabolic quotient and microbial community structure); soil animal indicators (earthworm-quantity and variety); and plant indicators (biomass yield, uptake of metals and metal accumulation in edible parts). However, the most commonly used indicator for soil heavy metal pollution is still total/recoverable content, though extractable amount is often more closely related to plant uptake or availability.  Heavy metal pollution is a global challenge that requires joint efforts of governments, scientists, and communities. Governmental regulations are essential in both source control and pollution remediation. Regulatory standards for heavy metal levels have been established for agricultural soils (Table 2), but wide Journal of Environmental Indicators, 9:17-18, 2015 Copyright © International Society of Environmental Indicators  Open Access: www.environmentalindicators.net   18 !discrepancy exists among different countries regarding the critical value of each contaminant.   Table 2. Regulatory standards of heavy metals in agricultural soil (mg/kg) (US EPA, 2002; EEA, 2007; TMS, 2007; CME, 2009; EPAA, 2012; NZME, 2012; EPMC, 2015); pH and land use dependent; NZ=New Zealand.  Country As Cd Cr Cu Hg Ni Pb Zn Australia 20 3 50 100 1 60 300 200 Canada 20 3 250 150 0.8 100 200 500 China 20-40 0.3-0.6 150-300 50-200 0.3-1.0 40-60 80 200-300 Germany 50 5 500 200 5 200 1000 600 Tanzania 1 1 100 200 2 100 200 150 Netherlands 76 13 180 190 36 100 530 720 NZ 17 3 290 >104 200 N/A 160 N/A UK 43 1.8 N/A N/A 26 230 N/A N/A USA 0.11 0.48 11 270 1 72 200 1100  Assessment of soil pollution with heavy metals involves sampling of representative soils in a problem area, analysis of metals and related parameters (such as pH), and comparison of soil contamination/pollution quantification against regulatory standards. The most commonly used methods of calculation include Hakanson potential ecological risk index (RI), geoaccumulation index (GI), enrichment factor (EF), Nemero comprehensive index (NCI), and pollution index (PI). Further research is needed to improve regulatory standards and assessment methods.    REFERENCES   Environment Protection Authority of Australia. 2012. Classification and management of contaminated soil for disposal.  Information Bulletin 105. Hobart, TAS 7001 Australia.  Canadian Ministry of the Environment (CME). 2009. Soil, Ground Water and Sediment Standards for Use under Part XV.1 of the Environmental Protection Act.  Environmental Protection Ministry of China (EPMC). 2014. National survey report of soil contamination status of China.  Environmental Protection Ministry of China, Beijing, China.  Environmental Protection Ministry of China (EPMC). 2015. Standards of soil environmental quality of agricultural land. Huangbanhang 69: Office of Environmental Protection Ministry of China, Beijing, China.  European Environmental Agency (EEA), 2007. Progress in management of contaminated sites (CSI 015/LSI 003), http://www.eea.europa.eu/data-and-maps/indicators  New Zealand Ministry for the Environment (NZME). 2012. Users’ Guide: National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health. Wellington: Ministry for the Environment. www.esdat.net.   Tanzania Minister of State (TMS). 2007 The environmental management (soil quality standards) regulations, Vice President’s Office – Environment  United States Environmental Protection Agency (US EPA).  2002. Supplemental guidance for developing soil screening levels for superfund sites. Office of Solid Waste and Emergency Response, Washington, D.C.   http://www.epa.gov/superfund/health/conmedia/soil/index.htm United States Environmental Protection Agency (US EPA), 2014. Cleaning up the Nation's Hazardous Wastes Sites.   http://www.epa.gov/superfund/  

Heavy Metal Contamination of Soils: Sources, Indicators and Assessment

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Heavy Metal Contamination of Soils: Sources, Indicators and Assessment

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