Ecological Threshold For Antimony In Soils Based On Different Bioassay Endpoints

21 Chinese typical farmland soils were collected in this study and added exogenous pollutants.Meanwhile,the toxicity of antimony（Sb）in different types of soils was referred to the standard methods recommended by ISO and OECD.The ecological toxicity threshold of Sb was obtained based on different test endpoint of barley and earthworm.In addition,Shanghai cabbage was selected as testing vegetable species to derive the safety threshold,using the species sensitivity distribution（SSD）method.The toxicity effects of Sb on root elongation of barley were studied.The range of EC10 and EC20 of root elongation were 201-2506 mg/kg and 323-2973 mg/kg,respectively.It was indicated that sand content was an important factor to Sb safety threshold by stepwise multiple regression analysis of soil properties.At the mean time,the aging process was noted to reduce the bioavailability of Sb.Sb bioavailability accounted for only 2.08-11.94% of the total soil Sb content.Sb bioavailability was positively correlated with soil p H,sand content and total phosphate,and negatively correlated with soil clay content,amorphous and crystalline iron,manganese and aluminium oxides.The toxicity effects of Sb to earthworm were studied.LC50 ranged from 666.03 to 2829.05 mg/kg.It was found that soil p H,organic matter,clay content,iron oxides were significantly correlated with LC50 by correlation analysis of soil main properties.Stepwise regression analysis concluded that 63.1% variation could be explained by the regression model.In vivo earthworm analysis also shown that the adsorbed amount of earthworm was mainly consistent with the Sb toxicity of LC50 in different soil types.Chronic toxicity threshold（EC50）ranged from 103.47-973.26 mg/kg.EC50 was positively correlated with clay content,and negatively correlated with soil p H and the content of calcium carbonate,shown by correlation analysis between EC50 and soil properties.Stepwise regression analysis concluded that 66.8% variation could be explained by the regression model.Cabbage was used as model crops planted on 21 soil samples with Sb contamination.The pot experiments were meant to deduct the Sb safety threshold of cabbage by using SSD method.The pot experiment data had shown that the sensitivity of different Sb contaminated soil varied far from each other.The HC₅ values of 95% soil protection based on Shanghai cabbage were 7.05 and 100.66 mg/kg,namely safety threshold values,calculated by backstepping the national food safety standards.The results of this study enriched the database of ecological toxicity threshold of Sb and provide the basis for setting the environmental standard of Sb.