基于多源环境变量和随机森林的农用地土壤重金属源解析——以襄阳市襄州区为例

为了研究襄阳市农用地土壤重金属空间分布特征和来源,选择襄州区为研究区,采集了326个样点的表层土壤（0~5 cm）,测定其中镉（Cd）、汞（Hg）、砷（As）、铅（Pb）和铬（Cr）5种重金属元素质量分数（单位为mg·kg^-1）,并进行反距离权重插值（IDW）分析得到土壤重金属空间分布,同时综合应用多元统计分析与随机森林回归模型探究土壤重金属的来源,研究表明综合应用多种技术是研究土壤重金属来源较为科学和准确的方法.结果表明：①襄州区整体环境质量较为安全,Hg、Cd和Cr的平均值质量分数低于湖北省土壤背景值;As的平均值质量分数略高于背景值;Pb的平均值超过了背景值,最大值为47.1 mg·kg^-1,是背景值的1.76倍,表明Pb已经出现了富集现象.②本研究中交通运输是Pb、As和Cr的共同人为源,农家肥是Cd、Pb和Cr的共同人为源.③在自然源中：土壤母质是影响Cd和Pb积累的重要因子,黏土矿物是影响Hg、Pb、As和Cr积累的重要因子,植被覆盖率是影响Hg、Pb和Cr积累的重要因子.

Source analysis of heavy metals in farmland based on environmental variables and random forest approach: District of Xiangzhou District in Xiangyang City

To study the heavy metal spatial distribution and sources in Xiangyang City, this study has collected 326 samples from surface soils in Xiangzhou District, and determined the contents of 5 heavy metals including Cd, Hg, As, Pb and Cr. The investigation applied IDW (Inverse Distance Weight) method to study the spatial distribution of heavy metals in soil, multivariate analysis and stochastic forest regression models were applied to find the sources. It is proved that combination of multi-technologies provides an effective way to delineate multiple heavy metal pollution sources. In general, the study area is at a safe level. The average concentrations of Hg, Cd and Cr in soils are lower, but As is slightly higher, and Pb is higher than the background concentrations in Hubei. The maximum concentration of Pb reaches 47.1 mg·kg^-1 in soil, which is 1.76 times higher than the background ones of Hubei, and accumulation of Pb appears in the study area. The results show that Pb, As and Cr in soil are from traffic, Cd, Pb and Cr are from organic fertilizer. Cd and Pb accumulation are affected by soil parent materials. Hg, Pb, As and Cr are affected by clay mineral. Hg, Pb and Cr are affected by vegetation cover.