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| Profile distribution of heavy metals in soil from long-term continuous cropping cotton field in Manas River Basin |
| Received:May 24, 2017 |
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| KeyWord:long-term continuous cropping;cotton field;soil;heavy metals;profile distribution |
| Author Name | Affiliation | | WANG Hai-jiang | Department of Resources and Environmental Sciences, College of Agronomy, Shihezi University, Shihezi 832000, China | | DONG Tian-yu | Department of Resources and Environmental Sciences, College of Agronomy, Shihezi University, Shihezi 832000, China | | ZHU Yong-qi | Department of Resources and Environmental Sciences, College of Agronomy, Shihezi University, Shihezi 832000, China | | SONG Jiang-hui | Department of Resources and Environmental Sciences, College of Agronomy, Shihezi University, Shihezi 832000, China | | SHI Xiao-yan | Department of Resources and Environmental Sciences, College of Agronomy, Shihezi University, Shihezi 832000, China | | ZHAO Xin-yue | No.1 Secondary School, Shihezi City, Shihezi 832000, China |
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| Abstract: |
| The content of heavy metals in soil is one of the best indicators for rational fertilization and environmental protection. The long-term continuous cropping of cotton is a common planting pattern in the Manas River Basin, Xinjiang Province, and it may increase the content of heavy metals in the soil. To gain a better understanding of heavy metal accumulation caused by this common planting pattern, soil samples were collected from wasteland and from continuous cropping cotton fields that had been cultivated for varying periods(5, 10, 20, or 30 years). Soils samples were taken for each cultivation period(20 cm square by 1 m vertical depth). We then determined the content, the vertical distribution characteristics, and the source of the heavy metals(As, Cd, Cr, Ni, Cu, and Pb) in the soil samples. The results showed that the contents of heavy metals in the cotton fields and wasteland did not exceed the secondary standard of national soil quality. All the average contents of the heavy metals in the cotton fields were apparently higher than both the background values for the Manas River Basin and the wasteland values, with the exception of Pb content. The variable coefficient values for the cotton fields were higher than those for the wasteland, Cd was the maximum of the heavy metal elements, with a variable coefficient value of up to 0.46. The contents of the surface layer were only slightly higher than those of the under layer, and more heavy metals accumulated in the surface layer with increasing years of cultivation. Compared with the contents in every layer of wasteland, heavy metals accumulated in the cotton soil to varying degrees in the different soil layers, and the increased ranges were:36.68%~102.81%(Cr); 43.31%~74.33%(Cu); 21.85%~64.95%(Ni); 2.12%~18.94%(Pb), and 23.03%~45.68%(As); Cd increased to the greatest extent, reaching 167.50%~269.19%. Correlation analysis revealed a highly significant correlation between the contents of P and As, Cd, Cr, Cu, and Ni, with correlation coefficients of 0.622, 0.689, 0.611, 0.513, and 0.560, respectively. In the cotton fields, the cumulative contribution rate of As, Cd, Cr, Cu, Ni, Pb, and P in the factor loading matrix was 85.46%, and the corresponding loadings in the first principal component were -0.875, -0.952, -0.868, -0.907, -0.964, -0.635, and -0.864, respectively. Our research indicates that extensive and long-term application of chemical phosphorus fertilizer is the main cause of heavy metal accumulation in the cotton fields of Xinjiang Province. |
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