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研究报告

Temporal-spatial distribution and source of nitrogen in main stream of Dongjiang River

摘要：为了防治东江氮污染并进行针对性水体治理,于2013年7月(丰水期)和2014年1月(枯水期)全面调查了东江干流水体氮的时空变化特征,并利用附生藻的稳定性氮同位素示踪技术对东江水体氮进行了溯源研究.结果表明,TN、NO₃^--N、NH₄⁺-N在丰水期的平均浓度分别为2.70、1.63、0.21 mg·L^-1,高于枯水期(TN,2.04 mg·L^-1; NO₃^--N,1.49 mg·L^-1; NH₄⁺-N,0.31 mg·L^-1);东江水体氮含量较高,且主要以NO₃^--N形态存在.各形态氮浓度自上游至下游的变化趋势表现为,TN和NO₃^--N先递减再升高,NH₄⁺-N则逐渐递增.稳定性氮同位素示踪表明,面源输入的人畜粪便、养殖废水及农业化肥等是上游区域氮的主要来源,贡献率约占91%;而在下游区域,城市污水的贡献率逐渐增大,并成为氮的主要来源,贡献率达到54%.

Abstract：During the period of flood season (July 2013) and dry season (January 2014), the temporal-spatial variation and sources of nitrogen in Dongjiang River was studied using nitrogen isotope values of epiphytic algae, aimed to provide proper methods to solve nitrogen pollution and protect Dongjiang River ecosystem. The results showed that nitrogen was dominated by NO₃^--N. The average concentrations of TN (2.70 mg·L^-1), NO₃^--N (1.63 mg·L^-1) and NH₄⁺-N (0.21 mg·L^-1) in wet season were significantly higher than those of dry season (TN, 2.04 mg·L^-1; NO₃^--N, 1.49 mg·L^-1; NH₄⁺-N, 0.31 mg·L^-1). As for distribution trend, the concentrations of TN and NO₃^--N gradually decreased from upstream and then increased in downstream. In contrast, the concentration of NH₄⁺-N increased gradually toward downstream. The results of stable nitrogen isotope tracer indicated that non-point source played a key role in nitrogen pollution (about 91%) in upstream, which derived mainly from human and animal feces, breeding wastewater and fertilizer. In contrast, urban sewage increased gradually and finally become the main source of nitrogen in downstream, accounting for about 54%.