[Spatio-temporal Distribution and Source Apportionment of Nitrogen in Rivers of Tieling]

This study analyzed the spatio-temporal distribution and sources of nitrogen (N) in 22 rivers in Tieling City during 2013-07-2014-07. The results showed that the concentrations of TN, NO₃^--N, and NH₄⁺-N were 1.26-18.85, 0.53-11.8, and 0.3-15.7 mg·L^-1, with an annual mean value of (5.8±1.9), (2.8±1.74), and (2.0±1.1) mg·L^-1, respectively. Overall, NO₃^--N was the main form of N with a percentage of 48%. The concentration of N in the wet season was significantly higher than that in the normal and dry seasons. According to the standards for surface water quality, water quality in eight rivers was worse than grade Ⅲ. Tiaozi River and Xiaoqing River were seriously polluted by ammonia N with a grade Ⅴ water quality through the sampling period, while Xiliao River, Xiaohezi River, and Liao River met the water quality standards. During the sampling period, δ¹⁵ N and δ¹⁸ O in nitrate in river waters were -3.0‰-23.9‰ and -11.7‰-57‰, respectively. Based on the data on the isotopes of N and O, N in the rivers in Tieling City mainly originated from human and animal excreta, industrial effluents, and domestic sewage. Sources of riverine N varied with seasons. For example, N in Tiaozi River and Nianpan River was mainly from fertilizer use and soil nitrogen in the wet season while it was from the industrial effluents and domestic sewage in the dry season.