浙江中部典型黑色岩系分布区土壤-作物富硒特征与重金属风险评价

富硒土地是生产富硒农产品的宝贵资源,黑色岩系形成的土壤通常富含硒和重金属元素。为了指导这类富硒土地资源的安全开发利用,选择浙江中部典型黑色岩系分布区,通过调查土壤-作物中硒和重金属的浓度及生物有效性,评价农产品富硒率,识别作物重金属超标风险。结果显示:研究区富硒土壤占38%,足硒土壤占62%,水稻和莲子富硒率分别为85.71%和100%;受黑色岩系风化成土影响,研究区土壤镉含量介于污染筛选值和风险管控值之间的样品比例为26%,且Cd活动态和潜在活动态所占比例分别为57%和40%,水稻籽实中Cd超标率为31%,莲子Cd含量均不超标。基于土壤重金属总量和形态的风险评价表明,富硒土壤开发利用的风险区主要位于西皮山岗和腰塘边一带,建议禁止种植农产品,其他黑色岩系发育的富硒丘陵地区,虽然土壤镉含量较高,但因土壤Cd的生物有效性和水稻中Cd的超标率较低,应加以保护和合理开发利用。

Selenium-rich Characteristics and Risk Assessment of Heavy Metals in Soil and Crop in A Typical Black Shale Area of the Central Part of Zhejiang Province,China

Selenium(Se)-rich soil is a valuable resource for the production of Se-rich agricultural products.Soil derived from black shales weathering is usually of high concentration of Se and heavy metals.To guide the similar safe use of Se-rich soil,a black shales area in the central part of Zhejiang Province was selected to identify possible risks of heavy metals in crop exceeding standards,through the investigation on the concentration and bioavailability of heavy metals and Se in soil and crop.The results showed that the Se-rich and Se-sufficient soil in the study area accounted for 38%and 62%coverage;the Se-rich rice and lotus seeds were 85.71%and 100%,respectively.26%of soil samples is of cadmium(Cd)content over the soil pollution screening value and less the soil risk control value.The proportions of Cd active and potential active states were of 57%and 40%,respectively.Up to 31%of rice samples exceeds national cadmium limit.The risk assessment based on the total concentration of heavy metals and sequential extraction shows that the Cd risk areas for the development and utilization of Se-rich soil are mainly located in Xipishangang and Yaotangbian area,and the cultivation of agricultural products should be prohibited.Other Se-rich hilly areas overlying black shales should be protected and rationally developed and utilized as low risk of Cd in crops and low bioavailability of heavy metals in soil,although cadmium concentration in soil is high.