汾河下游流域水体硝酸盐污染过程同位素示踪

Isotopic tracing for nitrate pollution process of water body in the lower reaches of Fenhe River

应用多同位素示踪、IsoSource计算等方法,甄别汾河下游流域硝酸盐污染来源,揭示各来源贡献率.结果表明,汾河下游流域地表水、地下水中含氮物质的主要存在形式为NO_3^--N,含量变化范围为4.21~16.29mg/L,且硝酸盐污染分布具有较大的空间差异,77.8%的样品中NO_3^--N含量超过国家饮用水标准,其次为NH_4^+-N,含量变化范围为0.31~9.47mg/L.所有地表水样品中均有NO_2^--N检出,郭庄村地下水中有NO_2^--N检出,说明受到了上游李雅庄煤矿开采活动的影响.δ15N-NO_3^-含量变化范围为+2.28‰^+13.88‰,δ^(18)O-NO_3^-含量变化范围为-0.28‰^+10.14‰.硝酸盐主要来源与沿岸土地利用类型有关,硝化作用是硝酸盐的主要形成方式,在广胜寺、龙子祠地下水封闭环境和庙前村水流缓慢河段有反硝化作用发生.粪便和污水是临汾段和河津段主要硝酸盐来源,其贡献率分别为69%和62%.襄汾段主要硝酸盐来源为农业化肥,约占总硝酸盐污染源的57%.土壤有机氮是地下水的主要硝酸盐来源,约占总硝酸盐来源的48%.

The objectives of this study were to reveal the sources of nitrate and the contribution of each source, based on isotopic tracing and IsoSource. The results showed that NO3～--N is the main nitrogen species in the sudied area, which ranges in 4.21～16.29mg/L, the spatial distribution of nitrate pollution are different greatly, 77.8% of the samples have exceeded the drinking water standard of China. The NH4～＋-N ranges from 0.31～9.47mg/L. The NO2～--N have been found in all surface water samples and the groundwater sample of Guozhuang, which indicates that the coal mining activity of Liyazhuang has already affect the water quality of groundwater. δ～（15）N-NO3～-ranges in ＋2.28‰～＋13.88‰, δ～（18）O-NO3～-ranges in-0.28‰～＋10.14‰, respectively. Nitrate is mainly produced by nitrification. Denitrification has been found in the river reaches of Guangshengshi, longzici and Miaoqian. Manure and sewage are the main sources of nitrate in the river reach of Linfen and Hejin, the contribution rate are 69% and 62%, respectively. Chemical fertilizer is the main sources of nitrate in the river reach of Xiangfen due to the agricultural activities, the contribution rate is 57%. Soil organic nitrogen is the main sources of nitrate in the groundwater, the contribution rate is 48%.