基于空间结构特征的土壤Cu、Pb来源解析—以北京市东南郊污灌区为例

【目的】 本研究旨在通过分析污染物空间结构特征解析典型污灌区土壤重金属污染成因。 【方法】 本文以北京市东南郊污灌区为例，在整个区域均匀布点，按1 km × 1 km密度采样，共采集土壤样品376个。每个样点为10 m × 10 m正方形，在四个顶点和中心点取0—20 cm表层土壤，均匀混合后用四分法从中选取1 kg土壤，作为代表该点的混合样品。Cu和Pb重金属含量采用原子吸收火焰法进行测定，利用Variowin2.0和ArcGIS10.2软件分析重金属空间结构及分布特征，解析其污染成因。 【结果】 研究区域土壤Cu和Pb空间结构均为套合结构，其块金值与基台值的比值在25%～75%之间。Cu和Pb的空间分布与河流走向密切相关，在西北–东南方向空间相关性较强，其高值区主要分布在研究区域中北部的凉水河流域、西部的永定河流域以及通州的东北部。 【结论】 污水灌溉和成土母质是研究区域土壤重金属的主要来源。由污水灌溉等小尺度因素主导的土壤Cu和Pb元素空间自相关距离分别为11.35 km和9.49 km；由成土母质等大尺度因素主导的空间自相关距离分别为26.65 km和31.70 km。通过分析不同尺度因素对区域土壤重金属含量空间分布的影响，可揭示土壤重金属污染成因，这种思路可为其他区域开展土壤重金属污染成因研究提供借鉴。

Source tracing of soil Cu and Pb based on spatial structure characteristics—A case study in the sewage irrigated area in the southeast suburb of Beijing

【Objectives】 Regional pollution sources of soil heavy metals can be analyzed by their spatial structure characteristics. In this paper, spatial structure characteristics of pollutants Cu and Pb were studied in order to analyze causes of heavy metals in a sewage irrigation area in southeast suburb of Beijing. 【Methods】 In this paper, southeast suburb of Beijing was selected as the study area. Firstly, points were uniformly set up in the whole area with 1 km × 1 km sampling density. Based on uniformed distribution points, sampling was carried out in the sewage irrigation area with the same sampling density (1 km × 1 km) and 376 soil samples were collected finally. At each sampling site, 5 sub-samples were taken from the 4 vertexes and the center of a square block (10 m × 10 m) and mixed thoroughly to select 1 kg soil as the representative sample of the site. Total soil Cu and Pb contents were determined using a flame atomic absorption spectrometer, their spatial structures were analyzed and distribution characteristics were described using Variowin 2.0 and ArcGIS 10.2 software in order to study their contamination causes. 【Results】 The spatial structures of both Cu and Pb in the studied area were nested structures, and nugget/sill ratios were between 25% and 75%. The spatial distribution of Cu and Pb was closely related to the river flows, and their spatial correlation was strong in northwest–southeast direction. The high values of heavy metals were mainly distributed in the Liangshui River basin (located in the north central of the study area), Yongding River basin (located in the west of the study area) and northeast of Tongzhou District. 【Conclusions】 The main sources of heavy metals were sewage irrigation and soil parent material. The spatial auto correlation distances of Cu and Pb dominated by small-scale factor such as sewage irrigation were 11.35 km and 9.49 km, respectively. However, the spatial auto correlation distances dominated by large-scale factor such as soil parent material were 26.65 km and 31.70 km, respectively. Through the analysis of different scale factors which have effects on spatial distribution of regional soil heavy metal contents, the sources of soil heavy metal pollution could be revealed. This idea can be provided as reference to study the sources of soil heavy metal pollution in other regions.