Abstract:

In order to comprehensively evaluate the status of heavy metal pollution in farmland soil around abandoned mining area, in this study, heavy metals Cu, Zn, Pb, Cr, As and Ni in farmland around a historically abandoned lead-zinc mining area in Xiaocu Village, Hongxing Street, Jingning She Autonomous County were selected as the research objects. A total of 12 farmland soil sampling sites were set up, and 24 soil samples of 0-20 cm and >20-40 cm were collected. The pollution level of heavy metals was evaluated by single factor pollution index method and Nemerow comprehensive pollution index method, and the pollution source was analyzed by correlation analysis and principal component analysis. The average contents of Cu, Zn, Pb, Cr, As, Ni and Cd in 0-20 cm (>20-40 cm) soil were 25.83 (24.17), 277.00 (317.67), 124.96 (147.71), 10.75 (20.08) and 3.68 (10.64), 5.67 (7.00), 1.07 (0.98) mg·kg^-1; The contents of Zn, Pb and Cd were higher than the background values of Zhejiang Province, while the contents of Cu, Cr, As and Ni were lower than the background values. Based on the screening value of “Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard” (GB 15618-2018), the single factor pollution index showed that Cu, Cr, As and Ni were currently in a clean and pollution-free state, Zn and Pb were in a light pollution level to a light pollution level, and Cd was in a lighted pollution level to a heavy pollution level. The results of Nemerow comprehensive pollution index showed that the average composite index of heavy metal pollution in this area was 2.21, which belonged to the medium pollution level. Principal component analysis showed that there were two main sources of 7 heavy metals in farmland soil in this area. Factor 1 included Cu, Zn, Pb and Cd, which was mainly influenced by human factors. Factor 2 included Cr, As and Ni, which was mainly affected by the parent material. At present, the main pollution factors of farmland in the study area are Zn, Pb and Cd, among which Cd content is the highest, which is mainly related to human factors. Therefore, special attention should be paid to Cd pollution in the future agricultural production process.

Key words: agricultural land, heavy metals, pollution evaluation, source analysis