Distribution characteristics of heavy metals in soil and water and health risk assessment of Zoige Wetland
Zoige Wetland is a typical high-altitude wetland ecosystem and an important component of the ecological barrier in the Qinghai-Tibetan Plateau.In July 2022,soil samples(degraded wetland and undamaged wetland)and surface water samples were collected for analysis of four heavy metals.The concentration distribution characteristics of chromium,arsenic,cadmium,and palladium in samples before and after wetland damage were described,and human health risk assessments were conduc-ted.The result showed that the concentrations of Cr,As,Cd,and Pd in undamaged and damaged wetlands were(mg·kg-1):6.23-26.19,2.06-45.00,0.01-0.63,and 1.32-10.87,respectively.According to the Soil Environmental Quality-Agri-cultural Land Soil Pollution Risk Control Standard,the compliance rates for chromium,palladium,cadmium,and arsenic are 100％,88％,94.4％,and 80％,respectively.Overall,these research results indicated that the distribution characteristics of chromium,arsenic,cadmium,and palladium concentrations in soil varied before and after wetland damage,and most of them met relevant standards.However,attention still needs to be paid to the risk control level of palladium elements.In surface water,cad-mium was not detected,while the concentrations of Cr,As,and Pd were(µg·L-1):0.04-1.14,0.15-23.77,and 0.01-0.94,respectively,all meeting the national surface water quality standard level I.Referring to the standards of the Environmental Protection Agency(USEPA)and the International Council on Radiation Protection(ICRP),the total non-carcinogenic risk in-dex(HI)of soil in Zoige Wetland was less than 1;the total carcinogenic risk(TCR)ranged from 2.53 × 10-6 to 1.20 × 10-4,all within the acceptable carcinogenic health risk level of 10-6 to 10-4.In surface water,the total health risk index(R)was from 1.97 × 10-6 to 2.01 × 10-4;the maximum permissible risk level for human consumption was 5.0 × 10-5.Among them,the proportion of samples exceeding the health risk level was 21.4％.This study found that the distribution of heavy metals in soil and water in Zoige Wetland had certain characteristics,with arsenic being the main factor leading to health risks.This study pro-vided certain data support for pollution prevention and control and environmental quality improvement in the Zoige area.
Zoige Wetlandheavy metal pollutionhuman health risk assessment
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