中文摘要：

文章为确定漓江桂林市区段三氮含量的变化趋势及其影响因素，分丰水期和枯水期在漓江干流及其支流上选择7个断面分别进行了取样，通过现场水化学指标和室内化验，对研究区三氮含量的时空分布特征和影响因素进行了探讨。分析结果表明：研究区漓江干流上C（NH3～N）和C（NO-3—N）的最高值分别为0．2483mg／L和2．2517mg／L，满足地表水环境质量Ⅱ类水标准，但漓江在经过研究区后三氮含量呈升高趋势；三氮含量的季节分布特征为NH3-N和NOa～N含量枯水期明显高于丰水期，而NO-2-N含量枯水期略低于丰水期，丰枯季节水温的变化会影响总无机氮（TIN）中各种形态氮含量的比例，使得C（NH3-N）／C（TIN）由丰水期的4．83％提高到枯水期的6．69％；流经农村生活区和农业地区的桃花江和小东江等支流是区内NH3-N的主要污染源，降雨后NH3-N的含量会明显升高。因此，加强区内漓江支流的综合治理、开展降雨条件下饮用水水源地取水口NH3-N含量的实时监测非常必要。

英文摘要：

The Lijiang River, an internationally famous karst scenic area, is the main source for massive water supply to Guilin City. It is reported that ammonia is one of three major nitrogenous contaminants, according to the monitoring data derived from 962 water stream sections in ten first catchments across China. To determine the temporal and spatial distribution characteristics of ammonia-nitrite-nitrate and associated influential factors, 7 sections on the Lijiang River and its tributaries are selected. The samples of surface water were collected during the wet and dry seasons, respectively. The analytical results of field chemical/physical parameters and laboratory experiments show that the highest concentrations of NH3- N and NO3- --N are 0. 248 3 mg/L and 2. 251 7 mg/L, respectively, which fall in the range of grade U water recommended by the national environmental surface water quality standards. The concentration of NO3 --N is also below the limit requirement of surface water sources for collective drinking water supply. However, the results also show that the ammonia-nitrite-nitrate concentrations in the Lijiang River have increased by various degrees and the water has a tendency of deterioration after the river flows through the Guilin City. The temporal distribution characteristics of ammonia-nitrite-nitrate is that the concentrations of NH3 --N and NO 3--N are higher during dry seasons and the concentration of NO2- -N becomes higher during wet seasons, The ratio of C（NH3 --N）/ C（TIN） is 4.83% in wet seasons; and the figure rises to 6.69% in dry seasons because of temperature change. The increasing of ammonia nitrite and nitrate nitrogen is attributed to the additional pollutants contributed from the tributaries of the river such as Xiaodongjiang river and Taohuajiang river, which are flowing through the rural domestic and agricultural area where is lack of sanitation facilities. In addition, the concentration of NH3--N has a raising trend and the concentration of NO2 --N and NO2- --N is almost stead