Based on the cultivating mode in central Gansu province, a semiarid area of northwestern China, concentrations of copper (Cu), lead (Pb), chromium (Cr), mercury (Hg), and arsenic (As) were measured in agricultural soils collected from Sifangwu, Gangou, Shajiawan, Qiangwan and Daba villages. The principalcomponent analysis (PCA) was used to assess the sources of these metals and As and the results showed that there were indeed serious pollution from Hg, As, Cu and Pb in agricultural soil in Qiangwan (sewage irrigation) and Daba (river irrigation) villages. Particularly in sewage irrigated soils, the Hg, As, Cu and Pb concentrations were respectively 64, 18, 3 and 2 times higher than their background values in Chinese grey calcareous soil. However, except Hg and Pb, the selected metals concentrations were lower than the background values in grey calcareous soil in the rainfed agricultural soils. The result of applying the varimax rotation with Kaiser Normalization showed that the irrigated factor, agricultural factor and anthropogenic factor have all contributed to the accumulated changes of metals and As in the sample sites. The main factor for the accumulation of Cu, Pb, Cr, Hg and As was lithological in rainfed agricultural areas. There was a striking dissimilarity in the origins of these metals in agricultural soil between the irrigated agriculture and arid agriculture.%根据地处半干旱地区的甘肃中部的农业耕作方式,在四方吴村、甘沟村、沙家湾村、强湾村和大坝村,调查分析了农业土壤中Hg,Cu,Pb,Cr,As的质量分数,并利用主成分分析方法分析了这些金属和As的来源.结果发现污水灌溉的强湾和黄河灌溉的大坝村,农业土壤存在严重的Hg,As,Cu,Pb污染,尤其是污水灌溉的土壤中,Hg,As,Cu,Pb的质量分数分别是中国灰钙土壤背景值的64,18,3,2倍.但雨养农业土壤中除了Hg,Pb外,其他几种元素的质量分数均低于中国灰钙土壤中的背景值.采用Kaiser方差最大正交旋转的主成分分析结果显示灌溉因素、农业因素和人为因素共同导致了样品点土壤重金属元素和As质量分数的变化,而雨养农业土壤中Hg,Cu,Pb,As富集的主要因素是成土母质.雨养和灌溉农业土壤中的重金属来源显著不同.
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