北京市近郊区土壤砷累积特征

Accumulation Characteristics of Arsenic in Suburban Soils of Beijing

城市近郊区土地利用类型多元化,同时也承载着巨大环境压力,研究近郊区土壤污染特征对城市规划及发展有着重要意义.通过3 km×3 km网格布点,系统采样调查了北京市近郊区5～6环路之间167个样点的0～20 cm表层土壤样品中砷的含量,分析了城市近郊区土壤砷的累积特征.结果表明,北京市近郊区土壤砷含量为2.89～11.38 mg.kg-1,平均值为7.11mg.kg-1.平均值在90年代末的背景值调查数据的范围之内,但是各个分位数级别的值均小于80年代初的北京市土壤背景值调查数据.因子分析结果发现北京市近郊区土壤砷与来源于成土母质的Co、Mn和Ni元素一组.克里格插值得到的北京市近郊区土壤砷含量空间分布图表明,西北与东部及东南部分土壤砷含量较东北和西南部高,砷含量最高25%的土壤样点与点源污染有关,而砷含量最低25%的样点大多远离污染源.不同土地利用类型土壤砷的比较结果表明人类活动在一定程度上影响土壤中砷的累积,生活区与农田土壤砷含量相似且显著大于绿地和荒地.污染源对生活区和绿地与荒地土壤中砷的累积有显著影响,工厂区附近的土壤砷含量显著比远离工厂区和交通区的土壤高.因此,北京市近郊区土壤砷在整体空间分布上主要与成土母质有关,然而人类活动在一定程度上也显著增加了土壤砷的累积.

Various land uses and enormous environmental pressures are characteristics of suburbs.Full understanding of suburban soil pollution is necessary for urban planning and development.In this study,167 surface soil samples（0-20 cm） located in suburbs of Beijing between the fifth and sixth ring road were collected based on the 3 km×3 km grids.The purpose of our investigation is to reveal the accumulating characteristics of As in Beijing suburbs.Results showed that arsenic contents in suburban soils of Beijing ranged from 2.89 mg·kg-1 to 11.38 mg·kg-1,with mean of 7.11 mg·kg-1.The means were in the range of the background values reported in late 1990s,but the values of each quantile were lower than the soil background values reported in early 1980s.Factor analysis suggested that As in Beijing suburban soil shared the same group as those elements coming from parent materials such as Co,Mn and Ni.The spatial distribution map using Kriging interpolation showed that As contents in northwestern,eastern and southeastern parts were higher than those in northeastern and southwestern parts.Those plots with contents of the highest 25% were all located near the pollution sources,while most of those with the lowest 25% contents located far from the pollution sources.Comparison of As contents in different land uses showed that human activities had influence on the accumulation of As in soils.Inhabitation areas and agricultural fields had higher As contents than the green lands and vacant lands.Pollution sources significantly affected the accumulation of As in soils of inhabitation areas,green lands and vacant lands.Arsenic contents in soils near factories were significantly higher than those far from factories and traffic corridors.To sum up,the spatial distributions of As contents in soils in Beijing suburban area were generally determined by the distributions of parent materials,while human activities increased the accumulation of As in soils to some degree.