桂西南土壤镉地质异常区水稻种植安全性评估

Safety Assessment of Rice Planting in Soil Cadmium Geological Anomaly Areas in Southwest Guangxi

为评估镉地质异常区水稻种植的安全性,在广西西南地区采集自然土壤41件,稻田土壤479件,相应水稻样品432组,测定其Cd、Cu、Ni和Zn含量以及土壤基本理化性质.运用单因子污染指数法(Pi)对样品污染程度进行评价,运用相关性分析探究影响稻米中重金属含量的主要因子.结果表明:①稻田土壤pH为6.8;有机质含量为39.00 g·kg^-1;基于《土壤环境质量标准农用地土壤污染风险管控标准》(GB 15618-2018)的风险筛选值,土壤中Cd、Cu、Ni和Zn超标率分别为60.75%、2.09%、0.83%和1.88%;②稻米Cd和Ni超标率分别为9.03%和4.39%,考虑秸秆作为饲料和有机肥原料,其Cd相应超标率分别为6.94%和1.16%.③相关性分析表明,土壤pH、有机质、重金属总量和有效态含量均是影响稻米中重金属含量的主要因子.研究区稻米Cd、Ni均存在一定超标现象,可通过种植低积累水稻品种等措施降低稻米中重金属含量.

To evaluate the safety of rice planting in cadmium geological anomaly areas,41 natural soil,479 paddy soil,and 432 rice samples were collected in southwestern Guangxi.The contents of Cd,Cu,Ni,and Zn and soil physical and chemical properties were measured.The single factor pollution index method(Pi)was used to evaluate the degree of contamination of the sample,and correlation analysis were used to explore the main factors affecting the heavy metal content in rice.The results showed that①soil pH of the paddy field was 6.8;the organic matter content was 39.00 g·kg^-1;the risk screening value was based on the soil environmental quality standards for soil pollution risk control and control of agricultural land(GB 15618-2018),the exceeding standard rates of Cd,Cu,Ni,and Zn in soil were 60.75%,2.09%,0.83%,and 1.88%.②The over-standard rates of Cd and Ni in rice were 9.03%and 4.39%,respectively.Considering straw as raw material for feed and organic fertilizer,the corresponding over-standard rates of Cd were 6.94%and 1.16%.③Correlation analysis showed that soil pH,organic matter,total heavy metal,and available content were the main factors affecting the content of heavy metals in rice.Cd and Ni in the study area all exhibited certain over-standard phenomena,and the low-accumulation rice varieties could be planted to reduce heavy metal content in rice.