乌鲁木齐市沿城市化梯度带土壤重金属环境容量评估

Heavy Metals in Soils of an Urbanization Gradient Zone in Urumqi City:Evaluation of Environmental Capacity

文章为阐明新疆乌鲁木齐市沿城市化梯度带土壤重金属环境容量,从代表性城-郊-乡-荒地梯度带采集88个表层土壤样品,分析各梯度带土壤中Cd、Hg、As、Pb、Cu、Ni和Zn等重金属元素含量。基于GIS和综合环境指数(PI),分析沿城市化梯度带土壤重金属环境容量特征及其空间分布规律。结果表明:研究区沿城-郊-乡-荒地梯度带表层土壤中各重金属含量有一定差异,各梯度带土壤中Hg明显富集。沿城市化梯度带土壤中重金属PI平均值从大到小依次为乡村、郊区、荒地、城区,各梯度带均表现为中容量区。土壤中各重金属单项环境容量指数空间分布规律不同,PI低值区主要分布于城区梯度带,表明城市化对土壤环境容量产生明显影响。各重金属在各年限内动态年容量和静态年容量从大到小依次为Zn、Ni、Pb、Cu、As、Hg、Cd。各梯度带土壤重金属动态年容量均呈现20 a>40 a>60 a>80 a>100 a的趋势。各梯度带土壤中各重金属元素在不同年限内平均动态年容量均大于静态年容量,土壤环境容量趋势好转。

The objective of this paper is to elucidate the environmental capacity of heavy metal in soils of an urbanization gradient zone of Urumqi City,a total of 88 surface soil samples were thereby collected from the typical gradient zone including urban,suburban,rural and wasteland areas,and heavy metal contents of Cd,Hg,As,Pb,Cu,Ni,and Zn in soils were measured,and the characteristics and spatial distribution pattern of the environmental capacity of soils was analyzed based on the GIS and the method of comprehensive environmental index(PI).As a result,the investigation showed that heavy metal contents in topsoil of the urbanization gradient zone along the areas of urban,suburban,rural and wasteland differed in a certain degree,and Hg had been evidently enriched in soils of all the areas of the gradient zone;the mean PIs of heavy metals in soils of the urbanization gradient zone were arranged in order of decreasing magnitude:rural>suburban>wasteland>urban,the relevant environmental capacity of all the areas being mediocre.As to the spatial pattern,individual environmental capacity index of each single heavy metal in soils of those areas was different,and low PI mainly distributed in the urban area,which indicated a significant impact of urbanization on soil environmental capacity.The dynamic annual capacity and static annual capacity of each heavy metal were in order of decreasing magnitude:Zn>Ni>Pb>Cu>As>Hg>Cd.In addition,the dynamic annual capacity of heavy metals in soils of each arear of the gradient zone showed a trend 20 a>40 a>60 a>80 a>100 a.The average dynamic annual capacity of every kind of heavy metal in soil of each gradient zone area was greater than the static annual capacity in fixed number of years,and as a whole,the environmental capacity of soils tended better.