Abstract:

To accurately assess the levels of heavy metal pollution, health risks and pollution sources in the surface soil of orchards in Qingyang City, the research team collected 16 surface soil samples at 0-40 cm soil layer from orchards in Qingyang City. The concentrations of chromium (Cr), cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), arsenic (As) and mercury (Hg) were determined. Based on the single factor pollution index, the Nemerow comprehensive pollution index, geo-accumulation index, potential ecological risk index and health risk appraisal model were used to evaluate the degree of heavy metal pollution and health risks. In addition, principal component analysis was applied to analyze the sources of heavy metal pollution. The results indicated that the soil of orchards in Qingyang City was severely polluted by cadmium (Cd), reaching a moderate pollution level. The geo-accumulation index for mercury (Hg) was greater than 5, indicating extreme pollution, while the geo-accumulation indices for other heavy metals were all below 0, indicating no pollution. The potential ecological risk index (RI) for the seven elements ranged from 1694.28 to 5158.06, indicating extreme pollution. The total non-carcinogenic risks for young adults (aged from 18 to 40) and middle-aged adults (aged from 41 to 60) were 0.12 and 0.09, respectively, indicating no non-carcinogenic risk to local orchard farmers from soil heavy metals. However, the total carcinogenic risks for young adults and middle-aged adults were 9.21×10^-5 and 7.45×10^-4, respectively, exceeding the acceptable level (1×10^-6), indicating a carcinogenic risk from soil heavy metals to local orchard farmers. Source analysis suggested that the main sources of soil heavy metal pollution may be a combination of traffic and plastic mulch, pesticides, fertilizers, and atmospheric deposition.

Key words: Qingyang City, soil of orchards, heavy metals, pollution appraisal, health risk, source analysis