Heavy metal pollution in farmland nowadays poses a great challenge in China because of the industrialization and urbanization.It is well known that cadmium (Cd) is one of the most priority control elements due to its strong biological toxicity and carcinogenicity.The main concern of Cd in agro-ecosystem is the health risk.Cd in soil is absorbed by plant and then enters the human body via the food chain.At present,the biological effectiveness of Cd is not a big issue for the environmental risk assessment of soil contamination,which leads to high uncertainty of actual exposure assessment.In recent years,an increasing number of researchers realize that biological effectiveness should be considered in the risk assessment of soil heavy metals.This paper summarizes the influencing factors (including soil,plant,pollutants and environment) and mechanism of the bioavailability of Cd in farmland.In addition,the health exposure assessment methods are discussed by oral intake and the bioavailability prediction model of heavy metals in soil.Finally,the deficiency of the risk assessment of soil heavy metals in China is analyzed,and the trend and direction of exposure assessment of Cd in soil are preliminarily predicted,which provides a reference to health risk assessment in farmland and safety baseline studies.%随着工业化和城市化进程的发展,我国在农田土壤污染领域面临较大挑战,其中镉(Cd)为最优先控制元素之一.农田土壤Cd污染风险类型为健康风险,其主要暴露途径为经土壤-植物系统,并经膳食进入人体.在当前的土壤Cd风险评估中,一般不考虑生物有效性问题,这使得风险评价中实际暴露评估的不确定性普遍偏高.所以,近年来欧洲国家有许多研究者提出将生物有效性因素放在土壤污染物风险评价框架内.基于此,本文立足于农田系统,并从土壤、植物、污染物及环境因素等4个方面详细综述了农田土壤Cd生物有效性的影响因素及其作用机理.其次,分别综述了近年来土壤Cd生物有效性预测模型和土壤Cd膳食暴露评估模型研究进展.最后,分析了我国土壤重金属风险评价中存在的不足,并对农田土壤Cd暴露评估发展态势和研究方向进行了初步预测,以期为农田土壤Cd健康风险评估及安全基准研究提供一定参考.
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