浙西石灰岩地区土壤和稻米镉含量研究

为理解石灰岩地区农田土壤重金属积累特点及污染风险，以浙西石灰岩地区为例，随机选择了153块重金属污染农田，点对点采集了土壤和水稻样品，分析了土壤和糙米中镉的含量及土壤性状，探讨了石灰岩地区污染农田土壤与稻米镉积累特点及其与土壤性状的关系。结果表明，土壤全镉随粘粒含量的增加而增加，随土壤pH的下降而下降；土壤有效镉占全镉的比例与土壤pH呈负相关，糙米中镉含量与土壤有效镉、水溶性镉呈显著正相关；糙米中镉含量与土壤pH、有机质含量及粘粒含量均呈现显著负相关，土壤pH是影响石灰岩地区农田糙米镉积累最为重要的因素。《土壤环境质量－农用地土壤污染风险管控标准（试行）》（GB 15618—2018）的污染风险筛选值并不适用于石灰岩地区高pH的土壤。当6.5 < pH ≤ 7.5时，土壤重金属镉含量与农产品中重金属镉超标结果并不一致，其风险筛选值（0.60 mg kg?1）偏低，实际的风险筛选值可能在0.80 mg kg?1以上。土壤水溶性镉较土壤全镉和有效镉能更好地评估石灰岩地区农作物重金属镉的污染风险。

Cadmium Cumulation Characteristics in the Contaminated Farmland Soils and Rice in the Limestone Hilly Areas of Western Zhejiang Province

In order to understand the accumulation characteristics and pollution risk of heavy metals in farmland soils in the limestone area of western Zhejiang province, 153 heavy metal contaminated farmlands were randomly selected, and both soil and rice samples were collected in the way of point-to-point. The cadmium contents of the soil and brown rice samples, and soil properties were analyzed. Moverover, the relationships between cadmium accumulation in the soils and brown rice, and soil properties were discussed. The results showed that total soil cadmium was increased with the increase of clay content, while decreased with the decrease of soil pH. The proportion of available Cd to total Cd was negatively correlated with soil pH. There was no significant negative correlation between cadmium content in brown rice and cadmium accumulation in soil, but it was significantly positively correlated with soil available cadmium and water-soluble cadmium. The cadmium content in the brown rice was significantly negatively correlated with soil pH, organic matter content and clay content. Meanwhile, soil pH value was the most important factor affecting Cd accumulation of brown rice in the limestone areas. The soil pollution risk screening value in Soil Environmental Quality – Risk Control Standard for Soil Contamination of Agricultural Land (Trial Version) (GB 15618—2018) was not applicable to the soils with high pH value in the limestone areas. When 6.5 < pH ≤ 7.5, the results of heavy metal content in soil over standard was not consistent with those in agricultural products. The risk screening value of 0.60 mg kg?1 could be lower, but the actual might be more than 0.80 mg kg?1. The water soluble cadmium in soil could be better to assess the risk of heavy metal pollution of crops in the limestone areas than soil total cadmium and available cadmium.