基于局部Moran’s I和GIS的珠江三角洲肝癌高发区蔬菜土壤中Ni、Cr的空间热点分析

Application of Local Moran's I and GIS to Identify Hotspots of Ni,Cr of Vegetable Soils in High-Incidence Area of Liver Cancer from the Pearl River Delta,South China

局部Moran's I是一种鉴定土壤重金属空间热点、区分空间集聚和空间离散的有用工具.本研究在珠江三角洲肝癌高发区系统采集了208个蔬菜地表层土样,分析每个样品的Ni和Cr含量,并在此基础上分析研究区蔬菜土壤中Ni、Cr的空间热点.结果表明,Ni、Cr的平均含量为33.2mg/kg、80.8mg/kg,比其相应的广东省土壤背景值分别高出130%、60%.总体上,土壤中的Ni有一定程度的积累,Cr的积累现象并不明显.本研究分别选取3000、6000、9000m作为距离尺度计算Ni、Cr的局部Moran'sI,基于6000m作为距离尺度的局部Moran's I鉴定了土壤Ni、Cr的空间热点;Ni、Cr的"个别热点"分布在研究区的北部,主要受人为因素的影响,"区域化热点"分布在研究区的南部,主要受成土母质控制.研究区原发性肝癌死亡率最高的区域与Ni、Cr的"区域化热点"重叠,两者区域上分布的一致性有可能为排查其环境致病因子提供一种思路.

The index of local Moran＇s I is a useful tool for identifying hotspots of soil Ni and Cr,and for classifying them into spatial clusters and spatial outliers.To identify hotspots of vegetable soils Ni and Cr in high-incidence area of liver cancer,Shunde area of Foshan City,Pearl River Delta Economic Zone,208 topsoil samples were collected from vegetable fields to measure the contents of nickel（Ni） and chromium（Cr）.The results showed that the mean concentrations of two heavy metals Ni,Cr were 33.21 mg /kg,80.84 mg /kg,respectively,Which were 130%,60% higher than their soil background values of Guangdong Province,respectively.Generally,Ni is partly accumulated in soil but the accumulation of Cr is not obvious at all.The local Moran＇s I of Ni and Cr was calculated using 3 000,6 000,9 000 m as distance bands,respectively.The hotspots of Ni and Cr elements in soils were identified by local Moran＇s I which computed based on 6 000 m;＂individual hotspots＂are in the north which were affected by anthropogenic factors;＂regional hotspots＂are in the south which were controlled by parent materials.Moreover,the distributions of＂regional hotspots＂of Ni,Cr are the same as that of the highest mortality rate of liver cancer,this consistence could come up with a research direction that could reveal environmental etiologic factors of liver cancer.