YANG Han-wen1,2, LIU Xiu-ming2,3, LIU Fang1, WANG Shijie2,3, HU Jingxian2
（1. College of Resource and Environmental Engineering, Guizhou University, Guiyang 550025, China;
2. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
3. Puding Karst Ecosystem Observation and Research Station, Chinese Academy of Sciences, Guizhou Puding 562100, China）
Abstract：The soil cadmium (Cd) in karst area of Southwest China has a characteristic of “high geochemical background and low pollution risk”. Whether the area, that exceeds the risk control value of “Standard of soil environmental quality for soil pollution risk control of agricultural land”, still has a low risk is an urgent question to answer. In this research, a high soil Cd rice-planting area located in the karst peak cluster valley of Luodian county was selected to reveal the modes of occurrences of Cd in soils, enrichment of Cd in different parts of rice plant, and the translocations of Cd between soil and rice. The results showed that, the average content of Cd in soil was 8.59 mg/kg, which is mainly in the reducible state (59%) and followed by the weak acid extraction state (22%); the average content of Cd in brown rice was 0.32 mg/kg, with an exceeding rate over the standard of 93%, whereas the enrichment coefficient was only 0.04; the average content of Cd in rice root was 4.54 mg/kg and the enrichment coefficient was only 0.52. Both the enrichment coefficients of Cd in brown rice and root are much lower than that in the main rice production areas in China where was polluted by industrial activities, indicating the relatively low risk of soil Cd pollution in karst area. Under the conditions of rich calcium, slightly alkaline, and reducting environment, multiple intertwined desorption-adsorption and dissolution- precipitation processes restrict the bioavailability of Cd in karst calcareous paddy soil, which is the main reason for the low enrichment of Cd in brown rice and root. Further studies to enhance the understanding of the biogeochemistry of Cd in karst area and to develop the soil Cd pollution abatement techniques and means are also proposed.
Key words: karst；high geochemical background of cadmium；rice; enrichment coefficient; translocation factor
EARTH AND ENVIRONMENT Vol.49, No.1, Tot No.339, 2021, Page 18-24