桂江流域地下水污染途径及防控措施研究

对桂江流域开展岩溶地下水污染调查发现:流域内地下水污染源分为"三氮"污染源、重金属污染源、有机污染源三类;"三氮"污染源主要包括工业、养殖和生活三类污水、生活垃圾渗滤液、农业施用氮肥等;重金属污染主要来自工矿企业;有机污染来自工业、养殖业。污染途径主要有孤峰平原的分散入渗式、孤峰平原的脚洞灌入式、峰丛洼地的消水洞灌入式、溶丘谷地的入渗式和峰丛峰林谷地的天窗灌入式等五类。并对88组地下水样品测试结果进行多指标地下水污染综合评价,结果表明36.5%的水点为"三氮"污染,多以分散入渗进入地下水,其污染形态呈面状分布;15.3%的水点为重金属污染,主要通过峰丛洼地消水洞灌入式补给和溶丘谷地入渗补给两种途径,呈点状分布于污染场地附近;3.49%的水点为有机污染,主要为分散入渗补给途径,污染呈短线状或点状分布。

The pollutant infiltration pathways and measures to control groundwater pollution in the Guijiang River drainage system

The investigation of karstic groundwater pollution in areas of Guijiang River has recently been completed; and our research findings show that the pollution sources can basically be categorized into nitrogenous, heavy metal and organic compounds. Among them the nitrogenous (nitrite, nitrate and ammonia) pollutants were mainly derived from industrial activity, livestock farming, domestic sewage and waste and the use of nitrogenous fertilizers, while heavy metal pollutions are attributed to industrial and mining activities and organic compounds to the impact of industries and livestock farming. In this case, the patterns of pollutants that migrate downward to reach the karst groundwater include diffuse and concentrated infiltrations, of which the former usually happens at isolated peak karst plains , rocky hill karst valleys. Concentrated infiltrations largely take place at the sink points in isolated-peak karst plain,the ponors in peak-cluster depressions and karst windows in peak-cluster and hoodookarst valleys. Systematic tests and analyses were performed to evaluate the rate of groundwater pollution. Results show that nitrogenous pollutions occur in 36.5% of the water samples which are broadly distributed over the karst autogenic recharge area in a diffuse infiltration manner. In the meantime, heavy metals in 15.3% water samples are above the directives of water quality regulations; and these point pollution sources enter groundwater via concentrated infiltration largely happens at the localities as sink points and ponors in peak-cluster poljes and via diffuse infiltration in the karst valleys. As heavy metals are easily absorbed by sediments, karst groundwater around the pollution sources has been more likely contaminated. Organic compounds were detected in 3.49% of the water samples, which are distributed at the downstream of the alluvial plain; and the pollutants that infiltrate into groundwater demonstrate a feature of short linear or point pollution because of the low hydraulic gradients of the groundwater.