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| Evaluation of heavy metal pollution in farmland soil of the Kaijiang watershed based on GIS |
| Received:February 20, 2019 |
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| KeyWord:heavy metal;farmland;spatial distribution;pollution evaluation;probability kriging |
| Author Name | Affiliation | E-mail | | HOU Qin-yan | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China
Sichuan Provincial Key Laboratory of Soil Environmental Protection, Chengdu 611130, China | | | ZHANG Shi-rong | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China
Sichuan Provincial Key Laboratory of Soil Environmental Protection, Chengdu 611130, China | rsz01@163.com | | MA Xiao-jie | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China | | | PAN Xiao-mei | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China | | | WANG Gui-yin | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China
Sichuan Provincial Key Laboratory of Soil Environmental Protection, Chengdu 611130, China | | | ZHONG Qin-mei | College of Environmental Sciences, Sichuan Agricultural University, Chengdu 611130, China | |
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| Abstract: |
| Evaluation of heavy metal pollution is important for planning of regional-soil heavy metal contamination control and implementation of remediation projects. In this study, we employed a single-factor pollution index method(Pi)to assess the pollution of farmland topsoil(0~20 cm)of the Kaijiang watershed in the hilly area of the Sichuan basin by heavy metals. The inverse distance weighted method (IDW), radial basis function method(RBF), ordinary kriging method(OK), disjunctive kriging method(DK), and probability kriging method(PK)were applied to analyze the spatial distribution of heavy metals in the soil. The average contents of soil cadmium(Cd), mercury (Hg), arsenic(As), and lead(Pb)were 0.35, 0.10, 7.77 mg·kg-1, and 22.54 mg·kg-1, respectively. With respect to the spatial distribution, soil Cd, As and Pb showed a decreasing trend from two high-value centers, and the soil Hg content was higher in the west and lower in the east. Statistical evaluation of single-factor Pi of all sampling points demonstrated that the over-standard rates(Pi ≥ 1)of soil Cd, As, Hg and Pb were 7.5%, 0.5%, 0, and 0, respectively. The area ratios of spatial interpolation based on the IDW, RBF, OK, and DK methods indicated that the soil Pb, Hg and As had no over-standard area, whereas the percentages of the soil Cd over-standard area(Pi ≥ 1)were in the range of 0.14%~1.06%. According to the risk assessment of probability kriging, soil Hg(Pi >0.3)and Pb(Pi >0.2)had no area with high-risk probability. When the threshold value of Pi was set to 1.0, 1.05% of the research area had high probabilities(0.8~1.0)of being polluted by As, and 0.16% of the soil in the survey zones carried a risk of Cd pollution(P=1.0). Therefore, some farmlands in the watershed were mainly polluted by Cd. |
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