基于GIS的农田土壤重金属空间分布研究

以浙江省慈溪市快速城镇化的小城镇为研究区,研究其农田土壤中重金属的含量与分布状况.采用ArcGIS中的地统计分析模块研究土壤中重金属分布的空间变异性,最后应用Kriging方法进行空间插值作图.结果表明,研究区土壤中的重金属含量均已超出当地的背景值,含量变异系数较大的重金属是Hg和Cu,中等变异的是Zn,其他几种重金属变异系数相对较小.空间分布上,Cu、Cd、As的空间相关性较强,Zn、Ni、Hg居中,而Cr和Pb较弱.插值结果显示,土壤中Cu、Zn和Pb的高含量区主要位于东南部,Cd、Hg和Ni的含量由南向北逐渐减少,As和Cr的分布为西部高而中部较低,不同的分布特征是人类活动与土壤母质双重影响的结果.

On the spatial distribution of heavy metal in the cropland based on GIS

The given study has been performed in a soon-to-be urbanized region in Cixi county, Zhejiang, which includes four small towns in hoping to investigate the content and the spatial distribution of heavy metals in the crop fields around the above towns. Our study has been done based on the geo-statistic approach by using ArcGIS with a distribution map drawn by means of Kriging method. The results of our investigation have shown that the actual content of all the heavy metals in the soil is over their original background level, with the variance index of Hg and Cu being the highest, that is, 97% for the former and 70% for the latter. At the same time, the variance index of Zn, 48%, lies in the middle, while the smallest variance indexes come with As, Cd, Cr, Pb, Ni, for their values are changing from 15% to 23%. The results of spatial distribution analyses show that the ratio of nugget to sill of Cu, Zn, Cd, Ni, Pb, Cr, As, Hg was 13.33%, 70.60%, 11.30%, 63.81%, 89.77%, 78.82%, 24.92%, 71.26% respectively, with their range of 6.7 km, 5.9 km, 5.6 km, 7.8 km, 3.3 km, 2.7 km, 4.4 km and 6.8 km respectively. This suggests that Cu, Cd and As have the strongest spatial correlation, with Zn, Ni, Hg keeping the moderate spatial correlation, and Cr and Pb, the feeble spatial correlation. And, finally, the spatial interpolation map reveals that the eight elements mentioned above have the different spatial distribution characteristics. The high remainder of Cu, Zn, Pb content has been found in the south-east of the region, though the content of Cd and Hg decreases gradually from the south to the north, with As and Cr being higher in the west but lower in the middle. In addition, various distributions have been found influenced by the double factors: human activity for their well-beings and the soil itself, which suggests that we should learn to use land properly and wisely in a well-planned way for the benefit of the local people in the future.