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Investigation and evaluation of soil heavy metals in a wheat-maize cropping system in upland China
Received:May 30, 2021  
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KeyWord:agricultural soil;heavy metal;pollution index;double cropping system;pollution source
Author NameAffiliationE-mail
LI Peng College of Resources and Environmental Sciences, Nanjing Agricultural University/ Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing 210095, China
Institute of Environment, Resource, Soil and Fertilizer, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China 
 
ZHANG Huijuan College of Resources and Environmental Sciences, Nanjing Agricultural University/ Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing 210095, China  
XU Li College of Resources and Environmental Sciences, Nanjing Agricultural University/ Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing 210095, China  
LI Huixin College of Resources and Environmental Sciences, Nanjing Agricultural University/ Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing 210095, China  
HU Feng College of Resources and Environmental Sciences, Nanjing Agricultural University/ Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing 210095, China  
JIAO Jiaguo College of Resources and Environmental Sciences, Nanjing Agricultural University/ Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing 210095, China jiaguojiao@njau.edu.cn 
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Abstract:
      The purpose of this study was to conduct a targeted investigation and systematic evaluation of soil heavy metal pollution in 150 fields in a regional scale wheat-maize cropping system in upland China. Soil pollution by eight heavy metal elements(Ni, Cr, Cu, Cd, Zn, Pb, Hg and As)was evaluated using the single factor pollution index(Pi), Nemerow comprehensive pollution index(PN), enrichment factor (EF), and ecological risk assessment(RI). The results showed that the overall soil pollution status of the wheat-maize cropping system is clean based on PN and RI. The As(29.04±9.21 mg·kg-1), Cd(0.15±0.14 mg·kg-1), and Pb(17.84±18.10 mg·kg-1)contents were higher than the national soil background values. The soils were not classified as polluted by the heavy metals, except for As, which had a slightly polluted status. Among different regions, the soil heavy metal content in the Yunnan area was higher than that in other areas, which posed a low potential ecological risk and was close to the medium ecological risk warning. The correlation, principal component analysis, and cluster analysis results showed that the soil heavy metals mainly originated from the soil parent materials and human activities. Ni, Cr, Cu, Cd, and Zn were more affected by soil parent materials, whereas Pb, Hg, and As were more affected by human activities. Pb and Hg originated from the application of mineral fertilizers, whereas As originated from the use of organic fertilizers and chemical fertilizers and the human activities of coal combustion and atmospheric deposition. In summary, the concentration and pollution risk characteristics of the eight heavy metals in the study area varied. The heavy metals in farmland soil originated from the soil-forming parent rock and further accumulated owing to human activities.