Study On The Toxicity Effects And Ecological Toxicity Thresholds Of Antimony To Soil-dwelling Folsomia Candida In Different Soils

The increasingly serious problem of antimony pollution in soil and potential adverse effects have attracted a high degree of concern.China has the most abundant antimony mineral resources in the world and face the severe soil antimony pollution situation,so strengthening the risk control of antimony in soil is of especial importance.The proper soil environmental quality standard of antimony is the core issue to evaluate the pollution of soil antimony.At present,the standard of antimony in the draft for comment of agricultural land environmental quality standard is controversial on account of several existing defects,such as failing to consider the specific soil differences fully and adopting the general standard nationally,etc.,so the soil antimony quality standards need to be revised urgently.In order to ensure the scientific accuracy of this work,it is necessary to intensify the study of regional soil antimony toxicity thresholds based on ecological toxicity effects.In view of hardly any toxicity data are available for terrestrial invertebrates,we explored the acute and chronic toxicity of two forms of antimony to soil-dwelling Folsomia candida in ten typical soils by using mortality and reproduction as evaluation endpoints.At the same time,the relationships between the main soil physicochemical properties and the antimony toxicity thresholds were determined and the prediction model of antimony toxicity was established further by carrying out multiple regression analysis.The effect of aging on the the speciation(oxidative state and water soluble fraction)and toxicity thresholds of antimony were also discussed preliminarily.The results indicated that:(1)The discrepancy of the antimony toxicity in different soils were significant.For Sb(III),the range of variation of LC50(median lethal concentration)of acute survival was 357-4537 mg/kg,the range of variation of LC50 of chronic survival was 124-2326 mg/kg,the range of variation of EC50(concentration causing 50%toxic effect)of chronic reproduction was 73-2035 mg/kg.For Sb(V),the range of variation of EC50 was 693-11968 mg/kg.Compared with the toxic thresholds,we found that the toxicities of the two forms of antimony in different soils both followed the order of Kunming<Jiamusi<Qiyang<Lingshan<Mianyang<Taiyuan<Zhengzhou<Chaoyang<Tongliao.The main soil physical and chemical properties affected the bioavailability of antimony by influencing the adsorption of antimony on the soil,which consequently resulted in the significant toxicity differences in different soils.There were significant positive correlations between soil antimony toxicity threshold to Folsomia candida and soil organic matter content,amorphous iron,amorphous alumina as well as clay content,while the toxicity thresholds tended to decrease along the elevated soil pH.The antimony toxicity prediction models based on the above soil physical and chemical properties can better explain the differences of antimony toxicity between tested soils.(2)The toxicity between Sb(III)and Sb(V)in each soil were significantly different,the toxicity of Sb(III)was more stronger than that of Sb(V).Other than the soil from Tongliao,Sb(V)could not cause the death of Folsomia candida directly even at the highest concentration both in the acute and chronic toxicity,just impact on its reproduction,whereas Sb(III)not only posed toxicity to the survival but also the reproduction of Folsomia candida.Specificly,the toxicity differences of two forms of antimony in different soils ranged from 5.9 to 20.1 fold.Therefore,when assessing the toxic effects of antimony,both the total amount and the forms should be taken into consideration.(3)Aging of exogenous Sb(III)played a crucial role in influencing its bioavailability and toxicity to Folsomia candida in soil.During the aging,the water soluble antimony in soil decreased significantly,simultaneously the high toxic Sb(III)was transformed into low toxic Sb(V)gradually and Sb(V)was predominant in soil.Consistent with the changes of water soluble antimony and oxidation process,the toxicity thresholds of antimony to Folsomia candida increased obviously,which signified the toxicity of antimony reduced greatly as aging time prolonged.Therefore,in order to avoid overestimating the ecological risk of antimony having multiple oxidative state,it is especially important to consider the effect of aging.The aging process of exogenous Sb(?)in soil varied with soil types,which was affected by some soil factors like iron,manganese,aluminum oxides content,organic matter and pH.In view of the oxidative state and water soluble fraction and toxicity of antimony at 60 days of aging tended to be stable,it is suggested that the reference value of the aging time of soil antimony should be about 60 days.This study can provide the basis for establishing the prediction model of antimony toxicity as well as formulating the quality standard value of antimony in soil.