重庆西部红层浅层地下水中“三氮”污染现状及影响因素分析

Pollution situation and influence factors of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen in shallow groundwater of red-bed region in western Chongqing City

红层浅层地下水是重庆西部农村居民的重要饮用水水源。在重庆西部的工业用地、农田、居民区和林地共布设52个地下水监测点,对浅层地下水中"三氮"的污染现状、分布特征、影响因素进行了探讨。结果表明,"三氮"在地下水中的空间分布差异性大,氨氮、亚硝酸盐氮和硝酸盐氮超标率分别达27.5%、20.0%、2.5%。地下水埋深和用地类型是影响地下水中"三氮"空间分布差异性的主要因素。硝酸盐氮/氨氮(质量比)随地下水埋深增加而增大,地下水埋深越深,硝酸盐氮所占比例越大;地下水埋深越浅或包气带缺失,则氨氮所占比例越大。硝酸盐氮主要来源于工业污染;氨氮与亚硝酸盐氮主要来源于农田氮肥施用。与历史监测资料相比,"三氮"在地下水中浓度呈上升的趋势,其中硝酸盐氮最显著。

Shallow groundwater of red-bed region is the main drinking water source in the rural area of western Chongqing City. To investigate the pollution situation of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in shallow groundwater of red-bed region in western Chongqing City, 52 groundwater samples were collected in industrial land, agricultural land, residential land and forestry land. The pollution situation, spatial distribution and influence fac- tors of ammonia nitrogen,nitrite nitrogen and nitrate nitrogen were analyzed. The results showed that 27.5 % samples were polluted by ammonia nitrogen, 20.0% samples were polluted by nitrite nitrogen, and 2.5 % samples were polluted by nitrate nitrogen. Groundwater depth and land types were main influence factors associated with distribution of am- monia nitrogen, nitrite nitrogen and nitrate nitrogen in groundwater. The ratio of nitrate nitrogen to ammonia nitrogen increased with groundwater depth,indicating that nitrate nitrogen was the dominant nitrogen form in deep areas, ni- trate nitrogen mainly originated from industial pollution,while ammonia nitrogen and nitrite nitrogen mainly origina- ted from nitrogen fertilizer. The concentration of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in groundwa- ter had been significantly raised compared with ten years ago, especially nitrate nitrogen.