关键词: agricultural soils, heavy metals, pollution characteristics, ecological risk, pollution index,  , hazard index,  , water town area, Dongguan City

Abstract:

To investigate the heavy metal pollution status and ecological and exposure risks in agricultural soils of the water town area in Dongguan City, vegetable bases and agricultural land of large traffic arteries both sides within the water town area were selected as study sites. A total of 32 soil and vegetable samples each were collected from vegetable bases and agricultural land of large traffic arteries both sides for analysis. Firstly, the pollution characteristics of eight heavy metals, including Cd, Hg, As, Pb, Cr, Cu, Zn, and Ni, were evaluated using the single-factor pollution index (IP) and the Nemerow comprehensive pollution index (PN). And then, ecological risk assessment and agricultural product quality and safety assessment were conducted, and the causes of heavy metal pollution were finally investigated. The results showed that the mean values of the mass fractions of the remaining seven heavy metals in vegetable bases soils were lower than the city’s soil background values, except for Ni; The mean values of the mass fractions of the remaining six heavy metals in agricultural land of large traffic arteries both sides were lower than the  mean values in the water town area, except for Pb and Ni; And the mean values of the mass fractions of the remaining heavy metals, except for Pb, Zn, and Ni, were lower than the city’s soil background values. Based on the single-factor pollution index, heavy metal accumulation is observed in the soil of vegetable bases and agricultural land of large traffic arteries both sides. Within the vegetable bases, 6.67% of the sampling sites exhibit Cd mass fraction surpassing the risk screening values for agricultural soil. In agricultural land of large traffic arteries both sides, 17.64%, 23.53%, and 5.88% of the sampling sites display Cd, Pb, and Cu mass fraction exceeding the risk screening values for agricultural soil, all remaining below the regulatory thresholds for pollution risk. Evaluation of the Nemerow comprehensive pollution index showed that agricultural land of large traffic arteries both sides were slightly polluted to varying degrees, with 40.00% and 64.70% in the mildly polluted category, respectively. The ecological risk evaluation showed that the potential ecological hazard index (Ie) of Hg reached the medium ecological risk level in 6.67% of the study sites in the vegetable bases, and the ecological risk hazard index (Ir) was at the medium ecological risk level in 6.67% of the study sites. For agricultural land of large traffic arteries both sides, 11.76% of the study sites had Cd Ie at medium ecological risk level, 17.64% of the study sites had Hg Ie at medium ecological risk level, and 5.58% of the study sites had Ir at medium ecological risk level. The evaluation of the quality and safety of agricultural products showed that there were Cd exceedances in the soil of vegetable bases and in agricultural products in agricultural land of large traffic arteries both sides. The reason for the excess of heavy metals in vegetable bases is related to the application of chemical fertilizers and pesticides and agricultural land of large traffic arteries both sides have heavy metal pollution from transportation sources and pollution inputs from agricultural sources.

Key words: 农业土壤')">

农业土壤, 重金属, 污染特征, 生态风险, 污染指数, 危害指数, 水乡地区,
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