Evaluation and source analysis of heavy metal pollution in the soil around typical metal smelting and mining enterprises in Hunan Province

In order to understand the current situation of heavy metal pollution in soil around typical metal smelting and mining industry in Hunan Province, 30 enterprises in the metal smelting and mining industry were selected as the research objects in this study, single factor pollution index, Nemeiro pollution index, potential ecological risk index and “Agricultural Land Soil Pollution Risk Control Standards” (GB15618-2018) were used to comprehensively evaluate the polution status of the soil cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), chromium (Cr), copper (Cu), nickel (Ni), zinc (Zn), and the main components method and the correlation method are also used to explore the sources of heavy metal pollution. The results showed that: The average values of Cd, Hg, As, Cu, Pb, Cr, Zn, and Ni in the samples in the contaminated area were 3.22, 0.985, 65.63, 67.43, 165.53, 94.07, 328, 43.9 mg·kg−1, it is 2.01, 3.66, 1.89, 1.98, 1.98, 1.14, 1.58, 1.39 times of the mean value of the corresponding heavy metal elements in the control point samples; The single factor pollution index (Pi) of heavy metals is Cd>As>Pb>Zn>Cu>Ni>Cr>Hg in dry land, Cd>Hg>Pb>As>Zn>Ni>Cu>Cr in paddy fields, Cd>Zn>As>Pb>Cu>Cr>Ni>Hg in wild grassland, and the order of the heavy metal Pi in woodland is the same as that of dry land. Results of Nemeiro Comprehensive Pollution Index show that the proportion of heavy metal pollution in paddy field, dry land, wasteland and woodland is 44.4%, 48.1%, 52.4%, and 31.6% respectively. The comprehensive evaluation results of the potential ecological risk index showed that the risk levels of dryland, paddy field, wasteland and forestland were 83.3%, 74%, 71.4% and 47.4% in intensity or above. The results of the risk control standard evaluation of agricultural land found that among the 93 soil samples in the contaminated areas, the proportion of samples in the priority protection category, safe use category and strict control category was 10.8%, 50.5% and 38.7% respectively. The results of source analysis showed that Cd, As, Pb, Zn, Cu in the contaminated soil may be influenced by agricultural activities, industrial activities and transportation, Cr may come from the control of the parent material of the soil, and Hg and Ni may be affected by industrial activities. The results show that the pollution control of heavy metals in the soil around the typical metal smelting and mining industry in Hunan Province should focus on strengthening the control and treatment of pollution sources of Cd, Hg, As, Pb and Zn.