广西西江流域土壤铜含量状况调查与风险评估

为系统了解广西西江流域农田土壤铜含量状况和空间分布特性,并评估其生态风险,2014—2016年间分别采集旱地土壤1 381个、水田土壤729个、矿区土壤129个和自然土壤293个,测试其铜含量。通过统计分析,探讨不同利用方式土壤对铜积累的影响,基于地统计分析了解其空间分布状况,并进行风险评估。研究结果表明,土壤样品中铜浓度的均值为27.60 mg/kg,旱地、水田、矿区和自然土壤4种类型的铜含量范围分别为0.3~317.91、3~495.81、7.5~2 287.66和0.68~284.27 mg/kg,均值分别为27.75、25.19、79.38和21.21 mg/kg,矿区土壤铜含量显著高于其他土壤。与土壤铜含量基线值相比,矿区土壤、旱地土壤和水田土壤的超标率分别为33.25%、3.76%和0.68%。西江流域铜表现为中等空间自相关,结构变异性强。西江流域有61%的土壤处于清洁水平;36%的土壤属于轻-中度污染,主要分布在南丹县、都安县、武宣县和桂平县,与砷矿和铅锌矿较为集中有关。总体来看,西江流域土壤铜虽然有一定积累,但污染较小,较为安全,南丹县、都安县、武宣县和桂平县等局部区域需防范其风险。

Copper Concentration in Soil of Xijiang River Basin of Guangxi and Risk Assessment

In order to understand copper concentration and distribution in soil of Xijiang River Basin of Guangxi and evaluate the ecological risk, this paper collected 1 381 dryland soil samples, 729 paddy soil samples, 129 mining soil samples and 293 background soil samples during 2012-2015, and measured the content of copper in soils. According to statistical analysis, the influence of copper accumulation in different types of soil was explored, the spatial distribution of copper content was interpolated through geostatistical analysis and the risk was assessed. The results showed that the geometric mean of copper concentrations was 27.60 mg/kg. The copper concentrations in dryland, paddy, mining and background soil ranged from 0.3 to 317.91, 3 to 495.81, 7.5 to 2 287.66 and 0.68 to 284.27 mg/kg, and the geometric means were 27.75, 25.19, 79.38 and 21.21 mg/kg, respectively. The copper concentration in mining soil was significantly higher than in other soils. Compared to baseline value, the corresponding exceeding rate of mining, dryland and paddy soil were 33.25%, 3.76% and 0.68%, respectively. The spatial pattern of copper content in Xijiang River Basin showed medium autocorrelation with strong structural variability. Clean soil occupied 61% in Xijiang River Basin, while 36% of soil belongs to light pollution soil which mainly distributed in Nandan, Du’an, Wuxuan and Guiping counties where lead-zinc ores are concentrated. Generally speaking, copper content in soil of Xijiang River Basin had some accumulation but the pollution was not serious and it was assessed to be safe. Besides, the risk should be prevented in the areas of Nandan, Du’an, Wuxuan and Guiping counties.