稻田土壤性质与稻米镉含量的定量关系

水稻是高累积镉（Cd）的农作物，其吸收累积Cd的量受多种因素影响.为明确田间条件下，土壤中Cd含量和土壤性质与稻米Cd含量的定量关系，在水稻收获时通过对60个不同田块的土壤和稻谷进行点对点采样，分析土壤Cd含量、土壤pH值、土壤有机质（SOM）、土壤阳离子交换量（CEC）和稻米中Cd含量，并通过线性相关与多元回归分析，研究Cd污染稻田土壤性质与稻米Cd含量的定量关系.结果表明：所采稻田土壤Cd含量范围为0.15~2.54 mg·kg^-1，其对应的稻米Cd含量范围为0.02~2.00 mg·kg^-1；简单线性相关分析表明，土壤全Cd含量与水稻籽粒Cd含量达到了极显著相关水平（P<0.01），相关性系数r=0.392（n=60）；土壤pH、有机质（SOM）和阳离子交换量（CEC）对稻米Cd含量也有一定的影响，但未达到显著水平；土壤pH与稻米Cd含量的关系呈现为：当pH小于6.5时，稻米Cd含量随着pH的升高而增加，当pH大于6.5时，稻米Cd含量随着pH的升高而降低.将土壤全Cd含量、土壤pH、有机质（SOM）、阳离子交换量（CEC）与稻米中Cd含量进行多元回归分析，得到5个稻米中Cd含量预测方程，其相关系数r均达到极显著水平（P<0.01），其中包括全部变量在内的预测方程的相关性系数最高，可以较好地预测此地水稻籽粒中Cd含量.

Quantitative Relationship Between Paddy Soil Properties and Cadmium Content in Rice Grains

Rice is a crop with the potential for high accumulation of Cd, which can be affected by many factors. Sixty pairs of soil and rice samples from different plots were collected and analyzed, in order to understand the quantitative relationships between the Cd content in soil and the properties of soil and the Cd content in rice grains under field conditions, by simple and multiple regression analyses. The results showed that the Cd contents in soil and rice grains ranged from 0.15-2.54 mg·kg^-1 and 0.02-2.00 mg·kg^-1, respectively. According to the result of simple regression analysis, there were significantly positive correlations (P<0.01) between the Cd contents in soil and rice grains (r=0.392); the pH, SOM, and CEC in soil also had certain effects on Cd accumulation in rice grains, which were not significant, however. When the soil pH was<6.5, the Cd content in rice grains increased with increasing soil pH, but decreased with increasing soil pH when the soil pH was>6.5. The Cd content, pH, SOM, and CEC in the soil and the Cd content in rice grains were analyzed by multiple regression analysis, and five equations, which all reached extremely significant levels (P<0.01), were obtained. The equation that included the four variables (Cd content, pH, SOM, and CEC in soil) had the most r, and it could predict the Cd content in rice grains better, given the conditions of the present study.