蔬菜镉(Cd)富集因子变化特征及其影响因素

本研究以湖南省攸县为例,测定重金属镉(Cd)在585个灌溉水样品和625对土壤蔬菜样品中的含量水平,结合农业与气象调查数据,应用典型相关分析及路径分析模型研究各环境因子对于Cd在土壤-蔬菜系统累积水平的影响.结果表明研究区灌溉水、土壤、蔬菜中Cd含量差异较大.蔬菜Cd富集因子(PUF)服从自然对数分布,有10%的概率大于1.土壤pH和土壤有机质对PUF有着显著的直接效应,土壤阳离子交换量,灌溉水pH,降雨量和氮肥施肥量通过与pH及土壤有机质的相关关系间接影响PUF变化.研究区土壤pH和土壤有机质含量较低,对于Cd在土壤-蔬菜系统中的累积风险应给予一定关注.

Variation Characteristics of Vegetables Cadmium Uptake Factors and Its Relations to Environmental Factors

The consumption of vegetables is a probable cause of Cd exposure in several world areas including China.In this study,we selected the prefecture of Youxian,southern China,as a case to analyze the influences of various environmental factors on Cd accumulation in vegetables based on a large scale agricultural and climatologically survey and collection of 585 irrigation water and 625 paired soil-vegetables samples.The results showed the concentration of Cd differed greatly in the irrigation water,soil and vegetables.The average daily dose for the adult populations consumed vegetables cropping in affected areas was slightly above the tolerable daily intake level,suggesting a potential health risk.The vegetables Cd uptake factor followed the natural lognormal distribution,and had a 10 percentile probability of higher than 1.The PUF values exhibited comparable results and appeared to define a reasonable and consistent Cd risk assessment.Many environmental variables (soil pH,soil organic matter,cation-exchange capacity,rainfall,water pH,and nitrogenous fertilizer usage) exhibited significant correlations with the concentrations of Cd in the soil-vegetable system.The canonical corresponding analysis and path model analysis found that soil pH and soil organic matter (SOM) had major direct effects on PUF.The close correlations between rainfall,water pH,nitrogen fertilizer usage and PUF were mainly resuled from the direct effect of soil pH and SOM.The high field-moisture capacity in the study area generated a rapid acidification causing the migration of Cd to weaker bounding sites thus promoting the vegetables uptake.The excessive application of nitrogen fertilizers led to a substantial loss of SOM and worsening of soil acidification ultimately causing increasing Cd accumulation in vegetables.Considering that the soil pH and SOM in the study area were maintained at a low level,the accumulation risk of Cd in soil-vegetable system needs to be addressed.The influence of environmental factors on vegetables accumulating Cd needs to be fully considered for better and safer vegetables production.