某流域农田土壤-水稻系统重金属空间变异特征及生态健康风险评价

Spatial variability and ecological health risk assessment of heavy metals in farmland soil-rice system in a watershed of China

为探讨某流域农田土壤-水稻重金属污染状况、空间变异特征及生态健康风险,2017年9—11月期间陆续在该流域采集水稻籽粒样品以及对应水稻田土壤样品各938个,测定其Cd、Hg、As、Pb和Cr 5种重金属含量,并基于ArcGIS和SPSS对土壤和水稻籽粒中不同的重金属生态健康风险进行评价。结果表明:从研究区土壤和水稻籽粒的重金属空间变异与分布规律来看,Cd、Hg、As和Pb为中等空间自相关性,Cr空间相关性则较弱;水稻籽粒中5种重金属的空间相关性均较弱。流域耕层土壤5种重金属中除Cr外,其余含量均较高,并且在南部中心区域呈现一个明显的大斑块污染区,向四周平缓扩散;水稻籽粒中Cd和As风险较高,主要在流域沿岸地区。从研究区土壤-水稻重金属污染风险分布情况来看,不同区域的重金属风险存在明显差异。耕层土壤重金属风险指数跨度较大,处于轻微风险;水稻籽粒风险指数跨度较小,不同区域的水稻籽粒重金属风险差异不明显,有11个点位属于中等风险级别,其余属于轻微风险级别。

To explore the heavy metal pollution in farmland soil-rice system,spatial variability and ecological health risks in a certain watershed were performed.From September to November 2017,938 rice grain samples and the corresponding paddy soil samples were collected in a certain watershed,and these five heavy metal contents:Cd,Hg,As,Pb,and Cr were determined.Based on ArcGIS and SPSS,the ecological health risk of different heavy metals in the soil and rice was evaluated.Watershed was the research area,thus,the distribution,spatial variation,and ecological health risk of heavy metals in the soil-rice system in the research area were analyzed,and the following results and conclusions were drawn:From the perspective of spatial variability and distribution of heavy metals in the soil and rice grains in the study area,Cd,Hg,As,and Pb were moderately spatially autocorrelated,while Cr was weakly spatially correlated;the spatial correlation of the five heavy metals in the rice grain was weak.Except for Cr,the contents of the five heavy metals in the cultivated soil of the watershed were all high,and there was an obvious large patch of pollution in the southern and central areas,which spreads gently around.The risk of Cd and As in rice grains was high,mainly in the coastal area of a certain river basin.From the distribution heavy metal pollution risks of the soil-rice in the study area,there were significant differences in heavy metal risks among the different regions.The soil heavy metal risk index in the arable layer had a large span and was at a slight risk.The rice grain risk index had a small span,and there was no obvious difference in the heavy metal risk of rice grain in the different regions.Eleven points belonged to the medium risk level,while the rest belonged to the slight risk level.