Nitrogen pollution characteristics and source analysis using the stable isotope tracing method in Ashi River, northeast China
2015
Ma, Guangwen | Wang, Yeyao | Buusiyang, | Hu, Yu | Liu, Yuping | He, Lihuan | Wang, Taiming | Meng, Fansheng
This study examined nitrogen (N) pollution characteristics based on water quality monitoring of the Ashi River and analyzed N sources by stable isotope tracer (SIT) techniques during a hydrological year in 2011. Twenty-two evenly distributed sites were sampled in the mainstream and tributaries of Ashi River during the temperate, wet, and dry seasons. The results showed that the concentrations of ammoniacal nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃⁻-N), and total nitrogen (TN) were lower in the upstream section of Ashi River, while the concentrations were higher in most other sections of Ashi River. Different forms of N had significant seasonal variations. The range of δ¹⁵N-NO₃⁻values indicated different N pollution sources. The upstream headwater area of Ashi River was mainly polluted by atmospheric N deposition and soil organic N. In the midstream and downstream areas of Ashi River, some sampling sites were affected by water released from cropland and rural domestic sewage, while other sites were polluted due to wastewater from livestock and poultry production. In addition, pollution in the downstream section of Ashi River was mainly caused by industrial wastewater. The city zone located in the basin had a greater impact on the variations of NH₄⁺-N concentrations, and less impact on NO₃⁻-N. N pollution characteristics of NH₄⁺-N, NO₃⁻-N, and TN, as well as NO₃⁻-N analysis to identify sources, reflected the profound impact of non-point source pollution during the temperate and wet seasons and point source pollution during the dry season in Ashi River.
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