湖南攸县稻米镉（Cd）富集特征及原因解析

攸县大米富镉(Cd)问题受到社会的广泛关注.通过实地调查和采样分析,应用路径分析模型(PA),多元回归分析和K-means聚类方法分析Cd在土壤-稻米系统中的富集特征,潜在风险和主要影响因子.结果显示攸县稻米Cd平均含量为0.47 mg·kg~(-1),约为国家粮食安全质量标准的2.5倍.稻米Cd富集因子(PUF)服从自然对数分布,变化范围较大.回归分析和PA分析显示土壤pH、土壤Mn和土壤Zn含量为影响PUF变化的主要环境因子,其中土壤Mn对PUF的影响主要体现在对稻米Cd的直接作用,土壤pH和土壤Zn对PUF的影响主要是通过影响土壤Cd含量而间接影响稻米Cd含量.K-means聚类分析显示土壤pH=5.6和土壤Mn含量=333 mg·kg-1可作为研究区对生产严重超标Cd米的土壤进行治理的初步调控阈值.

Enrichment characteristics of cadmium in rice and its influence factor in the Youxian prefecture, Hunan Province

The high level Cd concentration in rice in the Youxian Prefecture has been recognized as a health hazard. Based on the path analysis (PA) model, multi-statistical method and K-means cluster method, this study investigated the enrichment characteristics of Cd in the soil-rice system, potential ecological risk and major influence factor. Results showed that significant enrichment of Cd in soil-rice system was found throughout the Youxian prefecture. The concentration of Cd in rice was 0.47 mg·kg^-1, 2.5 fold higher than the national limits. The plant uptake factor (PUF) followed well with the natural lognormal distribution. The regression and PA analysis showed that soil pH, soil Mn and soil Zn were three main factors contributing to the variability of PUF. Soil Mn was the major factor influencing rice Cd uptake. The good correlation between PUF and soil pH and soil Zn are connected to the influences of these two variables on soil Cd concentration. K-means cluster analysis showed that soil pH=5.6 and soil Mn=333 mg·kg^-1 could be taken as the initial regulation standard for Cd pollution control in the study area.