Heavy metal concentrations and correlations in rain-fed farm soils of Sifangwu Village, Central Gansu Province, China

Concentrations of copper (Cu), lead (Pb), cadmium (Cd), chromium (Cr), mercury (Hg), arsenic (As), organic carbon (abbreviated to OC) content and pH were measured in rain-fed farm soils collected in Sifangwu Village which is located central Gansu Province, Northwest China. Concentrations of Cu, Pb, Cd, Hg and As are higher than the background values in grey calcareous soil. Cd concentration exceeds the Threshold of Secondary Environmental Quality Standard for Soil in China by 261 percent. By bivariate analysis, it was found that OC does not correlate with heavy metal in the village. This is due to the semiarid conditions and agricultural activities. Principal component analysis (PCA) was used to assess the soil data, applying varimax rotation with Kaiser Normalization. The result shows that the data set is defined for three latent components. 1) PC1, which consists of Cu and Cr, and what is characterized as a component subject to strong lithological influence. 2) PC2, dominantly loaded by OC, Pb and Cd, is linked to agricultural influence, i.e. fertilization and cultivation. 3) PC3, the heavy metals Hg and As, in this component are from aerial deposition, thus this PC is named the atmospheric factor. Because PC1 explains 45.026 per cent of total variance, the source of the heavy metal in topsoil in the study area is assumed to be mainly derived from the lithology. Copyright (c) 2006 John Wiley & Sons, Ltd.