成都平原部分地区农田土壤和稻米中镉含量及形态分布

Concentration and chemical speciation of cadmium in soil and rice of Chengdu plain, Sichuan

目的研究成都平原部分地区农田土壤和稻米中镉含量及土壤中镉的形态分布特征。方法于2014年8月,采集成都平原某区共计11件土壤和稻米样品,检测土壤pH、镉形态和稻米镉含量。结果该地区农田土壤p H在4.97~6.15之间,土壤中镉含量范围为0.19~0.44 mg/kg,平均值为0.29 mg/kg,污染指数（P镉）为0.63~1.47,有4件超标;稻米中镉含量范围为0.12~0.86 mg/kg,平均值为0.53 mg/kg,有10件超标,稻米镉富集系数为0.55~4.53。土壤中镉以弱酸提取态和可还原态为主,占总量近80%,形态的分布顺序为：弱酸提取态〉可还原态〉残渣态〉可氧化态。稻米镉含量与土壤中可氧化态镉含量呈负相关（P〈0.05）,而土壤中镉含量与弱酸提取态镉含量呈正相关（P〈0.01）。结论该地区土壤存在轻度的镉污染,稻米镉含量超标较严重。

Objective To understand the concentration of cadmium（Cd） in soil and rice and its chemical speciation characteristics in soil of the Chengdu plain, Sichuan province. Methods A total of 11 soil and rice samples were collected from the Chengdu plain in August 2014, the parameters of soil pH,chemical speciation of cadmium in soil and cadmium concentration in rice was analyzed. Results The soil pH values of the investigated area varied from 4.97 to 6.15, the concentration of cadmium in soil varied from 0.19 mg/kg to 0.44 mg/kg with the average value of 0.29 mg/kg, the pollution index of（PCd） within the range of 0.63 to 1.47, and four samples were over standard; The concentration of cadmium in rice varied from 0.12 mg/kg to 0.86 mg/kg with the average value of 0.53 mg/kg, ten samples were over standard. The cadmium enrichment factor of rice within the range of 0.55 to 4.53. The chemical speciation of cadmium in soil mainly existed in acid extractable and reducible, and the order was as follows： acid extractable〉reducible〉residual〉oxidizable. Correlation analysis showed negative correlation（P〈0.05） between the concentration of cadmium in rice and the concentration of oxidizable cadmium in soil, and significant positive correlation（P〈0.01） between the cadmium concentration and the acid extractable cadmium in soil was determined. Conclusion A mild cadmium contamination of the soil as well as the high over-standard rate of cadmium in the rice in the investigated area has been found.