地下水污染羽对傍河水源地的影响

The influence of the groundwater pollution on a riverside source field

以西北某城市傍河水源地及其上游原油储备库为研究区,利用地下水数值模拟软件GMS建立了地下水流和溶质运移耦合模型。根据不同的水源地地下水开采方案,应用危害最大化原则,预测未来10年内原油储备库地下水中有机污染羽对水源地的影响。结果表明,虽然原油储备库距离水源地较近,但由于原油储备库所在区域仅有薄层含水层,而水源地处于其下游的断陷盆地内,形成了特殊的水文地质结构。这使得原油储备库地下水向下游的补给十分有限。水源地地下水补给主要来自北面的黄河,即使水源地加大开采也只能对石油污染羽产生很小的拉动作用。在这种情况下,10年之内原油储备库污染羽不会污染水源地地下水。从长远考虑,为增加水源地的供水安全,应恢复黄河南河道,在增加水源地补给的同时,也在水源地与污染场地之间形成天然的水力屏障,可以从根本上防止有机污染羽对水源地的威胁。

Ten years＇ pollution risk of a petrochemical contaminated site on its downstream groundwater source in a provincial capital city of northwest China was predicted on the basis of groundwater flow and solute coupling model and by using GMS software. Several realistic groundwater pumping scenarios were used, but the natural degradation of petroleum hydrocarbon was not considered. Thus all the predicted risks were exaggerated to some extent. According to the modeling results, the petrochemical hydrocarbon pollution plume can not be transported across the border of the groundwater source. This is due to the special hydrogeological struc- ture of the study area. Only thin layers of Quaternary aquifer are distributed in the petrochemically contaminated site, while the groundwater source is in the rifted-basin downstream area. Under this condition, the recharge of groundwater from the petrochemi- cally contaminated site to the groundwater source is very limited, and the main recharge to the groundwater source is from the Yellow River. The drag of the contamination plume by groundwater pumping in the groundwater field is very weak. Taking long-term interest into consideration, the authors hold that an old Yellow R.iver channel called ＇south channel＇ should be restored to stop the intrusion of the pollution plume, because water in this channel flows between the petrochemically contaminated site and the groundwater source, and hence the channel can create a hydraulic barrier blocking the intrusion of the pollution plume and at the same time enhance the recharge to the groundwater field.