[Health Risk Assessment of Heavy Metals in Soil and Wheat Grain in the Typical Sewage Irrigated Area of Shandong Province].

Abstract

Sewage irrigation is a common alternative to make up for the shortage of agricultural irrigation in intensive agricultural areas. Abundant organic matter and nutrients in sewage can improve soil fertility and crop yield, but hazardous materials, such as heavy metals, will damage the soil environmental quality and threaten human health. To better understand the characteristics of heavy metal enrichment and potential health risk in a sewage irrigated soil-wheat system, a total of sixty-three pairs of topsoil and wheat grain samples were collected from the sewage irrigated area of Longkou City in Shandong Province. The contents of Cr, Cu, Ni, Pb, Zn, As, Cd, and Hg were determined to analyze heavy metal contamination and calculate bio-accumulation factor (BAF), estimated daily absorption (EDA), as well as hazard quotient (HQ). The results showed that the average contents of the eight heavy metals were 61.647, 30.439, 29.769, 36.538, 63.716, 8.058, 0.328, and 0.028 mg·kg-1, respectively, which all exceeded the background values of corresponding heavy metals in the eastern Shandong Province. Especially, the average content of Cd was higher than the current standard value of soil environmental quality of agricultural land soil pollution risk control, indicating the apparent soil contamination. However, the correlations between the heavy metal contents in soil and wheat grains were not significant, suggesting that it is difficult to conclude the enrichment degree of heavy metals in wheat grains merely by the heavy metal contents in soil. The results of BAF showed that the high enrichment capacity of wheat grain was primarily obtained with Zn, Hg, Cd, and Cu. According to the national food safety limit standard, the over-limit ratios of Ni (100%) and Pb (96.8%) in wheat grains were the most serious. As a result, under the current consumption of local wheat flour, the EDAs of Ni and Pb were high, accounting for 28.278% and 1.955% of the acceptable daily intakes (ADI) for adults and 131.980% and 9.124% of the ADIs for children. The results of the health risk assessment exhibited that As and Pb were the main sources causing health risks, accounting for approximately 80% of the total risk. Although the sums of the HQ of the eight heavy metals for adults and children were below 10, the total HQ of children was 1.245 times higher than that of adults. The food safety of children should receive more attention. When considering spatial characteristics, the health risk in the southern study area was higher than that in the northern part of the study area. The prevention and control of heavy metal contamination in the southern area should be strengthened in the future.