西南地质高背景区土壤镉释放动力学及辣椒安全阈值研究OA北大核心CSTPCD

This study aims to investigate the kinetics of cadmium(Cd)release from agricultural soils in a typical area with a high geological background in southwest China,and propose soil Cd thresholds for safe pepper production.The parameters of soil Cd release kinetics were obtained using diffusive gradients in thin-films technique(DGT)and the DGT-induced fluxes in soils and sediments model(DIFS).Pot and field experiments were conducted to derive the relationships between total and available Cd in soils and Cd in pepper.The soil-plant relationships were then used to derive the threshold value of soil Cd to protect safe pepper production.The results showed that in the study area,the release of Cd from the soil solid phase to the liquid phase was moderate to high(with R-values ranging from 0.42 to 0.98),and the low-pH condition was favorable for the continuous release of Cd long-term.Compared with traditional chemical extraction methods,the effective Cd concentration measured by DGT was the best predictor of Cd in pepper(R2=0.86),and total soil Cd,0.43 mol·L-1 HNO3 extractable Cd,and the first-step-extractable Cd of the BCR sequential extraction method,in combination with soil pH,yielded good multivariate linear regression models to predict Cd in pepper(R2>0.80 in all cases).The 0.43 mol·L-1 HNO3 extraction method had the advantage of being quick and easy,and combined with soil pH could serve as a reliable index to predict available Cd in carbonate-rock high-geological-background farmland in the study area.Validation with field data shows that the existing soil screening value for Cd is conservative for the study area,and that the total and HNO3-extraction-based Cd thresholds derived in this study can better protect the safe production of local pepper.