农田退水期阿什河氮污染特征及来源解析

利用水质监测技术和稳定同位素示踪技术,对春季农田退水期阿什河河水中ρ(NH₄+-N)、ρ(NO₃--N)和ρ(TN)特征进行研究并对氮污染来源进行解析. 结果表明,ρ(NH₄+-N)、ρ(NO₃--N)和ρ(TN)除在阿什河上游源头区水体中较低外,其余大部分区域均较高. 上游源头区采样点 δ 15N值为3.68‰～6.09‰,主要受大气沉降氮和土壤有机氮的污染；中下游区域中一部分采样点δ15N值为5.32‰～7.72‰,主要受农田退水和农村生活污水影响,另一部分采样点δ15N值为8.45‰～11.86‰,主要受畜禽养殖污水影响较大；下游采样点δ15N值较低(3.25‰～4.15‰),主要受工业来源废水污染. 农田,特别是河流两岸的稻田退水对阿什河水质影响较大；城区对阿什河TN和NH₄+-N影响较大,对NO₃--N影响较小. 

Nitrogen Pollution and Source Analysis in the Ashi River during the Period of Water Release from Cropland

The distribution characteristics of ammonia nitrogen(NH4+-N),nitrate(NO3-—N),total nitrogen(TN) and tracing pollution sources of nitrate in the Ashi River during the period of water release from cropland in the spring were investigated using water quality monitoring techniques and the nitrogen isotope tracer technique.The results showed that the concentrations of NH4+-N,NO3-—N and TN in the upper region of the Ashi River were the lowest,while they were very high in most of the other parts.The percentage of δ15N was 3.68‰-6.09‰ in the upper region of the Ashi River,which was mainly polluted by atmospheric nitrogen deposition and soil organic nitrogen.δ15N values of some samples from the middle and downstream portions of the Ashi River were 5.32‰-7.72‰,which was caused by water released from cropland and rural sewage.δ15N values from other sites of this region ranged from 8.45‰ to 11.86‰,which was due to the impact of livestock wastewater.In the lower reach of the Ashi River,δ15N values of 3.25‰-4.15‰ were mainly caused by industrial wastewater pollution.Riverside croplands,especially the rice fields on both sides of the Ashi River,had a great impact on the river water quality.The city zone located in the basin greatly impacted the variations of concentrations of NH4+-N and TN,but its effect on NO3-—N was minor.