三峡库区梁滩河流域水化学与硝酸盐污染

运用水化学和水质分析技术,测定了三峡库区梁滩河流域地表水体和地下水体中的水化学组成和硝酸盐氮含量,揭示了梁滩河流域地表水和地下水水体的水化学组成和硝酸盐污染的空间分布规律、来源及循环过程。结果表明:梁滩河流域地表水的硝酸盐污染表现为沿着地表径流从上游到下游呈现出加重的趋势,这种污染趋势与养殖业、生活和工农业废污水的沿程直接排放有着直接关系;而地下水硝酸盐污染呈现出流域上游和下游较轻、而中游东侧支流区域较重的空间分布特征,这种空间分布特征与地表水体中氨氮和有机氮的含量、地表水与地下水之间的补给排泄关系、厚层土壤包气带的存在以及土地利用状况等因素有着密切的关系。

Water chemistry and nitrate pollution in the Liangtan River basin in the Three Gorges Reservoir Area

By using the water chemistry and water quality analysis technology, the water chemistry components and nitrate nitrogen concentrations of surface water bodies and groundwater bodies in the Liangtan River basin in the Three Gorges Reservoir Area were measured to reveal the spatial distribution rules, sources and circulation processes of the water chemistry components and nitrate pollution in the water bodies in the study basin. The results show that: a tendency of becoming severe for the nitrate pollution in the surface water bodies exists in the Liangtan River basin from the headstream to the downstream along the surface water flow paths, and this tendency presents the direct relationship with the direct discharge of waste and polluted water from the breed aquatics, housing and farming industry along the surface water flow paths. A spatial distribution of nitrate nitrogen pollution of groundwater displays a lighter pollution level for the headstream and downstream reaches area in the basin, while a heavier pollution level for the eastern branch in the middle reaches area. There is a close relationship between the spatial distribution of nitrate nitrogen pollution and the factors such as the ammonia nitrogen and organic nitrogen concentrations of the surface water bodies, the recharge and discharge interrelationship between the surface water and groundwater bodies, the existence of thick unsaturated zone and land use condition. The analysis shows that application of livestock manure and widespread use of nitrogen fertilizers are potential sources of nitrate contamination. Generally, the ground water bodies in the agricultural watersheds are polluted by long-term trend of nitrate contamination, which coincides with higher mineralized water due to agricultural-related land use practices. In a basin where severe human activities are dominant, the evolvement tendency of the ground water nitrate may disobey the rule that ground water nitrate concentrations decrease substantially along the groundwater flow paths. As for the Liangtan River basin, along the groundwater flow paths, there is a sharp increase in the groundwater nitrate concentrations from the headwater area to the area between the upper and middle reaches of the river, while a sharp decrease appears in the area between the upper-middle reaches and the middle-lower reaches of the river.