不同磷肥浓度下土壤-水稻系统重金属的时空累积特征

针对磷肥是水稻田重金属污染的主要来源,采用田间试验与室内分析相结合的研究方法,在吉林省九台市饮马河老稻田区,开展5种磷肥浓度处理对土壤-水稻系统重金属Cd和Pb的时空累积、分布特征研究。结果显示,磷肥中Cd和Pb含量高于土壤背景值,但没有超出国家土壤环境质量（二级）限定范围。磷肥施入土壤后,部分滞留在土壤里,少量向地上部分迁移,水稻根部累积重金属含量较高。随水稻生育期的变化,成熟期重金属在根、叶和籽实累积量最大,茎的重金属累积量在孕穗期达到最大。重金属Cd在水稻各器官的迁移能力为根〉籽粒〉叶〉茎,Pb的迁移能力为根〉叶〉籽粒〉茎,Cd在水稻地上部分的迁移能力要明显强于Pb。磷肥施用量和重金属含量的关系可用线性回归方程来模拟,相关性检验显示重金属累积量与磷肥施用浓度均达到显著相关（P〈0.01）（除根中Cd含量与磷肥浓度达到0.05显著水平）,说明水稻栽培生产中过量使用磷肥,能产生重金属对土壤和稻米的污染,进而导致重金属对人畜健康的潜在威胁。

Spatio-temporal Characteristics of Heavy Metal Accumulation in Soil-rice Cropping System Under Different Phosphate Fertilizer Concentrations

To further understand the phosphate fertilizer as a major pollution source of heavy metals in paddy field,we used the field test and the indoor analysis technique to study spatio-temporal accumulation,distribution characteristics of Cd and Pb elements in soil-rice system. The study site was located in old-paddy field,Rinma River,Jiutai in Jilin Province,and the phosphate fertilizer in our experiments was separated into five treatment concentrations. Our results showed the contents of Cd and Pb elements in the phosphate fertilizer were higher than that in soil,but not more than the limited values of national secondary standards of soil environment quality. After heavy metals in soil and phosphate fertilizer were absorbed by rice plant,a majority of these metals were still detained in the underground part,only a little were carried to aboveground part of rice. Of all the parts of rice plants,heavy metals accumulation concentrations in rice roots were the highest. The concentration of heavy metals in root,leaf and paddy reached the highest level in autumn as the rice gets mature. The trans-conductive sequences of Cd and Pb elements in different part of rice were：rootpaddyleafstem and rootleafpaddystem,and the sequence of two heavy metals in aboveground parts of rice was：Cd Pb. The relationship between the treatment concentrations of phosphate fertilizer and content of heavy metals in soil and rice plant was analyzed by using linear regression. Statistical test showed that the treatment concentrations of phosphate fertilizer were significantly correlated with content of heavy metals（P〈0.05）. Our study indicated that applying excessively phosphate fertilizer might lead to heavy metals pollution in soil-rice system,even potential menace to people and livestock.