基于SWAT模型的流域河道硝酸盐δ^(15)N和δ^(18)O模拟  

Simulation of Nitrate Isotopic(δ^(15)N and δ^(18)O) by Coupling the Hydrology and Transport Processes Described by the SWAT Model

作　　者：王康[1] 冉宁[1] 林忠兵[1] 周祖昊[2] 

机构地区：[1]武汉大学水资源与水电工程科学国家重点实验室,武汉430072 [2]中国水利水电科学研究院水资源研究所,北京100038

出　　处：《环境科学》2018年第1期68-76,共9页Environmental Science

基　　金：国家自然科学基金项目(51379152;91647109;51679257);国家重点研发计划项目(2016YFC0402405)

摘　　要：为提升流域地表水硝酸盐溯源方法的可靠性,于2013~2015年在釜溪河流域,对流域水文和水质过程进行了连续监测,同步测定了流域内主要污染源和干支流河道硝酸盐δ^(15)N和δ^(18)O.基于SWAT(soil and water assessment tool)模型模拟了陆面水文和河道水文过程中的氨氮(NH_4^+)和硝酸盐(NO_3^-)迁移转化过程,在此基础上,耦合河道中硝酸盐^(15)N和^(18)O掺混、转化和分馏机制,发展了流域河道硝酸盐δ^(15)N和δ^(18)O模拟方法.结果表明,河道中硝酸盐δ^(15)N和δ^(18)O主要受流域内污染源以及不同水文期径流条件变化的影响,不同污染源同位素掺混过程对于同位素丰度变化的贡献率为82.74%,氮素转化过程中同位素分馏的贡献率为16.26%,SWAT模拟NH_4^+和NO_3^-浓度偏差对δ^(15)N和δ^(18)O模拟误差的影响为10.44%.由于降雨中硝酸盐δ^(18)O的变化范围显著地超过δ^(15)N的变化范围,以及河道硝酸盐18O来源复杂性,δ^(18)O模拟误差平均较δ^(15)N偏大18.72%.所提出的方法模拟河道硝酸盐的δ^(15)N和δ^(18)O结果的系统误差和偏差小于10%和15%.所提出的流域河道硝酸盐δ^(15)N和δ^(18)O模拟方法具有明确的物理意义,为河道氮素正向溯源提供了方法支撑.To improve the reliability of methods to trace surface water pollutants in river basins,hydrological and water quality processes in the Fuxi River Basin were continuously monitored from 2013 to 2015,and the main pollution sources in the watershed and δ^（15）N as well as δ^（18）O in the rivers were measured simultaneously.The Soil and Water Assessment Tool（SWAT） model was used to simulate the NH_4~＋ and NO_3^- migration processes in the hydrological processes of the land surface and rivers.On this basis,the processes of mixing,transformation,and fractionation of δ^（15）N and δ^（18）O in NO_3^- were coupled,and the simulation methods of δ^（15）N and δ^（18）O in the rivers were developed.The results showed that δ^（15）N and δ^（18）O in the rivers were mainly affected by the pollution sources in the river basin and the variation in runoff conditions during different hydrological periods.The contribution of the mixing process of different isotopes to the isotope abundance was 82.74%.The contribution of isotope fractionation in the process of nitrogen conversion was 16.26%.The influence of NH_4~＋ and NO_3^- concentration deviation from the SWAT simulation on the simulation errors of δ^（15）N andδ^（18）O was 10.44%.The δ^（18）O simulation errors were 18.72% larger than those of δ^（15）N because of the higher variation range of δ^（18）O in rainfall and the complexity of δ^（18）O.The systematic errors and deviations of the simulated δ^（15）N and δ^（18）O results using the proposed method were less than 10% and 15%,respectively.The simulation method of δ^（15）N and δ^（18）O in the river basin has a clear physical meaning,which provides a useful approach for tracing nitrogen sources in rivers.

关 键 词：流域 硝酸盐 SWAT模型 同位素 过程模拟 

分 类 号：X52[环境科学与工程—环境工程]