广西西江流域土壤Zn积累和分布特征及生态风险

Accumulation,Distribution and Ecological Risk of Zn in Soils in the Xijiang River Valley of Guangxi

为了解广西西江流域土壤Zn积累和分布特征,评估其生态风险,采集有色金属矿区土壤、农田(水田和旱地)土壤和自然土壤样品共2 534个,结合各样点类型和各地区状况进行大规模调查分析。结果表明:西江流域土壤Zn背景值为67.3 mg·kg-1,显著高于广西土壤Zn背景值;矿区、旱地和水田土壤Zn含量均值分别为2 134、148.5和71.6 mg·kg-1。以基线值为标准,矿区、旱地和水田土壤Zn含量超标率分别为77.3%、7.56%和3.59%,矿区土壤表现出明显的Zn积累趋势;流域内土壤Zn空间分布具有中等程度空间自相关性,为结构性因素和随机性因素共同作用;从空间分布状况可知,流域内高Zn污染区主要集中于河池市南丹县的南部局部区域,轻-中污染区出现在都安县和环江县小区域,轻污染区出现在大化县、罗城县、都安县、柳城县、武宣县、金秀县和忻城县等一带小区域,其余区域处于比较清洁的状态。总的来说,河池市的南丹县、环江县、都安县等个别矿业密集的地区或矿厂、冶炼厂遗址、尾砂库等周边矿区土壤及小部分农田土壤存在高污染风险,其余区域风险较低或无风险。对于高含量Zn污染区域,建议加强监管,开展环境生态风险和人群健康风险评估,必要时采取措施以控制风险。

To characterize accumulation and distribution of Zn in the soils of the Xijiang River Valley of Guangxi and to assess its ecological risk, 2 534 samples were collected of the soils in nonferrous metal mining areas, farmlands （ paddy and upland fields） and natural land in the region, during a large scale survey carried out in the light of types of sampling sites and physical conditions of the region for analysis. Results show that the soil of the valley was 67. 3 mg ＊kg 1 in back-ground value of Zn significantly higher than the soil of Guangxi Province as a whole. The mean concentration of soil Zn in the mining areas, upland and paddy fields was 2 134, 148. 5 and 71. 6 mg ＊kg 1 , respectively with the baseline as bench-mark, about 77. 3%, 7. 56% and 3. 59% of the soils in the mining areas, upland and paddy fields was above the nor^n, respectively. The soils in the mining areas displayed an apparent trend of Zn accumulation, and spatial distribution of soil Zn in the valley exhibited a moderate leveled autocorrelation affected jointly by structural factors and stochastic factors. The spatial distribution of soil Zn in the valley shows that the soils high in Zn pollution were concentrated mainly in the south-ern part of Nandan County of Hechi City, the soils light-moderate in Zn pollution, in Du^an County and Huanjiang Coun-ty, the soils light in Zn pollution, in Dahua County, Luocheng County, Du^an County, Liucheng County, Wuxuan Coun-ty, Jinxiu County and Xincheng County and the soils relatively free of Zn pollution in the rest of the valley. Generally speaking the soils in Nandan, Huanjiang and Du＇an of Hechi and other areas concentrated with mining, smeltery and tail-ing dumping were very high in Zn pollution risk, while the soils in the other areas relatively lower in or free of Zn pollution. It is, therefore, recommended to strengthen supervision and to assess environmental and ecological risks and human health risk of soil Zn in those highly Zn contaminated areas, and take actions to control the risks when necessary.