Contamination and potential health risk of heavy metals in vineyard soil in Turpan Basin

Background  The environmental quality of agricultural land soils is closely related to the quality and safety of agricultural products. With the regional agricultural intensification, a series of soil environmental safety problems, such as soil degradation and dysfunction, are caused by toxic heavy metal elements entering into the soil ecosystem.

Objective  This study aims to understand the pollution levels and distribution patterns of heavy metals in vineyard soil in a main grape production area in China, and evaluate their potential human health risks.

Methods  A total of 101 soil samples from vineyard in Turpan Basin were collected for analyzing the concentrations of arsenic (As), cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), and mercury (Hg). The detected concentrations were compared with the Soil environment quality-Risk control standard for soil contamination of agriculture land (GB 15618-2018). The contamination levels and potential health risks of the six heavy metals in vineyard soil were analyzed based on the Nemerow pollution index (NPI) and the US Environmental Protection Agency Health Risk Assessment Model.

Results  The average concentrations of As, Cd, Cr, Ni, Pb, and Hg in vineyard soil in Turpan Basin were 9.57, 0.19, 59.0, 21.60, 13.41, and 0.045 mg·kg^-1, respectively, and all were lower than the national limits (GB 15618-2018), but the average concentrations of As, Cd, Cr, and Hg exceeded the background values of irrigation soil in Xinjiang. The average values of single contamination factor (P_i) for each heavy metal element from high to low were Cd (1.54) > Cr (1.49) > Hg (1.16) > As (1.05) > Pb (0.99) > Ni (0.82). Among them, the vineyard soil was mildly polluted by Cd, Cr, Hg, and As (1 < P_i ≤ 2), and slightly polluted by Ni and Pb (0.7 < P_i ≤ 1, warning line). The average value of NPI for the vineyard soil was 1.53 and suggested the soil was mildly polluted (1 < NPI ≤ 2). Both the non-carcinogenichazard index (HI) < 1 and carcinogenictotal carcinogenic risk (TCR) < 1×10^-6 health risks of selected six heavy metal elements in vineyard soil showed a negligible risk level. The hazard quotients (HQ) and carcinogenic risks (CR) of selected heavy metal elements via hand-mouth ingestion were the highest among various exposure pathways. Both the non-carcinogenic and carcinogenic health risks of selected heavy metals for children were higher than those for adults.

Conclusion  The potential health risks caused by exposure through three pathways such as hand-mouth ingestion, inhalation, and skin contact to selected six heavy metal elements in vineyard soil in the study area are in safety scales.