Geochemical characteristics and ecological risk assessment of cadmium in selenium-rich soil of Chengde City in Hebei Province

Selenium is an essential bioelement for human being. It is a safe and effective way to increase the level of human selenium by selenium-enriched agricultural products. Selenium-enriched land resources are the main selenium source for selenium-enriched agricultural products. However, the multi-purpose geochemical surveys carried out nationwide in recent years have found that Cadmium, a heavy metal element, is usually relatively high in selenium-enriched soils. Therefore, the study on the geochemical characteristics and ecological risk status of Cadmium in selenium-enriched lands has an important guiding significance for the development of selenium-enriched soils. In this paper, the geochemical characteristics and ecological risks of Cadmium in the surface soil of selenium-rich soil area of Chengde city in Hebei province were evaluated, aimed at providing scientific basis for the development and utilization of selenium-rich land. The spatial distribution characteristics and environmental grades of Cadmium in topsoil were studied. The water-soluble, ion exchangeable, carbonates bound, humic acid bound, Fe-Mn oxides bound, tightly organic mater bound, residual of Cadmium were extracted step by step. At the same time, the contents of Cadmium in apple and corn were analyzed to understand their bioavailability. The results show that Cadmium is enriched in the surface soil in the selenium-rich soil area of Chengde city, and significantly enriched in the new accumulation soil, neutral coarse bone soil and paddy fields. In the study area, four piece of Cadmium lightly contaminated soils are delineated in the high value areas of Cadmium in the surface soil. The order of the average content of Cadmium in surface soil is water soluble < ion exchange < tightly organic mater bound < humic acid bound < Fe-Mn oxides bound < carbonates bound < residual fraction. The carbonates bound component is high and has potential environmental hazard. Cadmium in apple and corn is low. The ecological risk of Cadmium in surface soil in the selenium-rich soil area of Chengde city is low. The development and utilization of selenium-rich land in Chengde city is not affected by Cadmium in surface soil, temporarily.