Abstract:
The environmental safety of the producing area of agricultural products has been widely concerned and the risk status of heavy metals in the soil of the producing area of agricultural products has realistic and long-term significance. Yellow soil under different planting patterns in Kaiyang county of Guizhou province was taken as sample for the studies of its heavy metal content characteristics and pollution levels. The results showed that under different planting patterns, single-cropping soil was acidic before planting and after harvest, while in continuous cropping and intercropping periods it was neutra. The contents of heavy metals including Cd, Cr, Cu, Zn and Pb in soil were basically the same, all of which were higher before planting than after harvest. The variation degrees of pH and heavy metal such as Cd, Cr, Cu and Zn in soil were not high, while the variation degree of Pb was high before continuous planting and after intercropping. Correlation analysis shows that Cd has high homology with Cu, Pb, and the same for Cu with Zn and Pb. Comprehensive pollution index(
Pzong) scores from high to low: crop monoculture (before planting) > intercropping (after harvest) > continuous cropping (before planting) > crop monoculture (after harvest) > intercropping (before planting) > continuous cropping (after harvest), which were 14.20, 13.67, 13.62, 11.38, 9.89 and 8.04, and all the above were higher than 3.0, belonging to heavy pollution levels. Pollution of soil is quite serious, the pollution degree of the monoculture and continuous cropping after harvest was declined with different degree compared with those before planting, and the pollution degree of intercropping is on the rise. Among the selected pollution evaluation factors, the contribution of metal Cd is very high, which is the main influencing factor of soil pollution, followed by metal Cr.