沈阳张士灌区彰驿站镇土壤与水稻植株镉污染分析

Cadmium pollution in soil and rice plants in Zhangyizhan Town of Zhangshi irrigation area of Shenyang

采集张士灌区下游彰驿站镇水田土壤及水稻植株样品,测定土壤和水稻植株各部位中总镉浓度及土壤中不同形态镉浓度,采用单因子污染指数法分析了水田土壤及糙米的镉污染现状,并根据镉在水稻中的迁移系数、富集系数、土壤中不同形态镉对植株的贡献率及镉形态与土壤理化性质的关系探讨了影响植株镉吸收因素。结果表明:采样区土壤镉含量在0.47~2.49 mg·kg-1,均已超过国家土壤环境质量二级标准(GB 15618—1995),且超过当地背景值1.47~12.11倍;土壤中镉形态特征分布为残渣态>弱酸提取态>可还原态>可氧化态;水稻植株各器官镉含量分布趋势为根>茎>叶>糙米;有41.6%的糙米样品超过国家相应的食用标准,目前多以轻度污染为主;水稻对镉的富集能力、镉在水稻植株中的迁移能力及土壤中镉的形态分布是影响水稻吸收土壤中镉的重要因素,其中土壤中弱酸提取态和可还原态对水稻植株镉的吸收贡献率最大,且二者与土壤pH和CEC之间的相关性达到显著性水平。

Samples of paddy soil and rice plants were collected in the Zhangyizhan Town, which was located in downstream area of Zhangshi, Shenyang, China. Total Cd and different fractionations of Cd in soil and rice plants were determined. The pollution status of soil and brown rice was analyzed by single factor pollution index method. The factors that affected Cd uptake of plants were investigated according to the analysis of Cd migration coefficient and Cd enrichment factor in plants, contribution rate of different Cd fractionations to plants, and the relationship between Cd fractionations and soil physicochemical properties. Results showed that Cd concentrations in soil ranged from 0.47 mg·kg-1 to 2.49 mg·kg-1, which exceeded the second class soil standard in China’s Soil Environment Quality Standard （GB 15618-1995）. Compared to the soil background value, the concentrations of Cd were 1.47-12.11 times more than the local background value in Shenyang. The proportions of different Cd species in studied soils were： Residual fraction〉weakacid soluble fraction 〉reducible fraction 〉oxidizable fraction. The amount of Cd accumulated in different parts of rice followed the order of root〉stem〉leaf〉grain. In addition, the Cd concentration of 41.6% brown rice samples exceeded the pollution limit for food and classified as slight pollution. The accumulation of Cd in rice, the migration ability of Cd in rice plants and the distribution of Cd in soil were important factors affecting the uptake of Cd in rice. The largest contribution to the uptake of plants came from weakacid soluble fraction and reducible fraction. There were significant negative correlations between weakacid soluble and reducible fractions and soil characters such as pH and CEC.