中文摘要：

为判断华南地区典型城市地下水硝酸盐污染源，采集珠海市香洲城区及周边地区地下水样，并测定NO3^-、NH4^＋、NO2^-、PO4^3-、δ^15N—NO3^-以及EC、pH值等。结果显示：在城市区地下水大多数样品中，NO3^-是主要的无机氮形态。近40％的水样超过世界卫生组织饮用水标准（NO^3- -N≤10mg／1），部分井水有NO2^-检出，整体污染较为严重。地下水硝酸盐δ^15N落在6．879％0～26．144‰范围内，而生活污水及化粪池泄漏是地下水NO3^- -N主要污染源。反硝化作用可能是导致雨季地下水δ^15N值升高的重要因素。另外，稀释、混合等作用可能是导致地下水NO2^-浓度季节变化复杂的原因。

英文摘要：

In order to assess the distribution, source of nitrate in groundwater system in South China, groundwater samples were collected during two different seasons and analyzed for NO3^- ,NH4^＋ ,NO2^- ,PO4^3- ,δ^15N-NO3^- and EC, pH etc. The results show that nitrate is the dominant species of nitrogen in most samples. There are about is more than 40 percent of total samples whose nitrate concentration more than 10 mg/l（WHO drinking standard）. The values of δ^15 N-NO3^- ranged from 6. 879‰ to 26. 144‰. Nitrate in groundwater most originate from septic tanks and sewage water. Moreover, complexity of nitrate concentration in different season, higher values of δ^15N in wet season suggest that denitrification probably occur in groundwater system as well as effects of dilution and mixing.