兰州市农村饮用水中硝态氮分布特征及评价

水体硝态氮污染是水污染研究的焦点之一。通过对兰州市7个县区农村98个生活饮用水水样的测定分析,结合国家相关标准（GB5749—2006）,对兰州市农村生活饮用水硝态氮含量进行评价,并通过回归分析推断了不同水源类型水体硝酸根与电导率的相关性。结果显示：①兰州农村生活饮用水水体硝态氮平均含量为（5.42±6.63）mg·L-1,合格率为86.73%;②皋兰县、西固区和安宁区农村生活饮用水硝态氮含量无超标现象,榆中县、七里河区、永登县、红古区农村生活饮用水硝态氮含量较高,有不同程度超标现象,合格率分别为77.27%、77.78%、80.00%和83.33%;③不同水源类型水体硝态氮含量存在显著差异：自来水、河水和水库水合格率均为100%;窖水、深井水（〉30m）和泉水硝态氮含量较高,合格率分别为92.00%、91.66%和55.56%;浅井水（〈30m）硝态氮平均含量最高,为（22.27±10.54）mg·L-1,合格率仅为25.00%;④除水库水和浅井水,其他类型水体硝酸根与电导率呈显著或极显著的正相关性;⑤浅井水中水体硝态氮含量与pH呈显著负相关;⑥浅井水和泉水水体硝态氮含量与农田氮投入量存在显著正相关性。

Investigation on Nitrate Nitrogen Distribution Characteristics of Drinking Water in Lanzhou Rural Area,China

The pollutant of nitrate-N（NO-3-N） plays an important role in water pollution nowadays.Analyzing the data of NO-3-N contents of rural drinking water from 98 plots around Lanzhou,we evaluated the water quality in comparison with the National Standard（GB 5749—2006）,and investigated the correlation between NO-3 content and the EC.The results showed：①The mean NO-3-N content of drinking water was（5.42±6.63）mg·L-1 and the Rate of Qualification（RQ） was 86.73% in Lanzhou rural area.②The NO-3-N contents were not beyond the limit of the National Standard in Gaolan County,Xigu and Anning District;whereas overproof samples were observed in Yuzhong County,Qilihe,Yongdeng and Honggu District,in which the RQ was 77.27%,77.78%,80.00% and 83.33% respectively.③Significant differences of NO-3-N contents were detected on different types of water.The RQ was 100% in tap water,river water,and pool water,whereas the RQ was 92.00%,91.66%,and 55.56% in cellar water,deep well（more than 30 m） water,and spring water,respectively.The highest content of NO-3-N was detected in shallow well,which was（22.27±10.54） mg·L-1,and the RQ was 25.00%.④There was significantly positive correlation between EC value and NO-3-N content except for the pool and shallow well waters.⑤The significantly negative correlation was detected between pH value and NO-3-N content in shallow well water.⑥The nitrogen input in farmlands was significantly positively correlated with NO-3-N content in shallow well and spring waters.