河口区无机氮超标原因分析及管理对策研究——以黄茅海为例

Causes analysis of over-standardization of inorganic nitrogen in estuary area and management countermeasure--A case study of Huangmao Sea

入海河口区无机氮超标是我国主要入海河口普遍存在的问题,严重影响近海海域水环境质量。以黄茅海为研究对象,调查2017—2021年2条入海河流河口断面氨氮、硝酸盐氮、亚硝酸盐氮、总氮,黄茅海海域氨氮、硝酸盐氮、亚硝酸盐氮以及2021年黄茅海海域2个水质净化厂入海排污口中氨氮和总氮的监测信息,分析了氮浓度特征,发现河口断面、河口海域及入海排污口中氮指标均以硝酸盐氮为主。利用MIKE模型模拟了入海河流河口断面氮对河口海域背景浓度的影响,发现在入海河流氨氮浓度符合地表水Ⅱ类标准的条件下,河口海域无机氮也会受入海河流硝酸盐氮的影响,处于相对较高的背景浓度值。研究发现,河口区无机氮超标与陆海水环境氮指标不衔接及评价标准不合理密切相关,为了提升河口海域水质,应加强陆海统筹管理。

Over-standardization of inorganic nitrogen in estuary area is a common problem of major estuaries in China,which seriously affects the quality of water environment in coastal waters.Taking Huangmao Sea as a case study,based on the data of ammonia nitrogen,nitrate nitrogen,nitrite nitrogen and total nitrogen in the estuary sections of two rivers into the sea,the ammonia nitrogen,nitrate nitrogen and nitrite nitrogen in the Huangmao Sea from^(2)017 to 2021,and the ammonia nitrogen and total nitrogen in the marine outfalls of two water purification plants in the Huangmao Sea in 2021,the distribution characteristics of nitrogen concentration were analyzed.Results showed that nitrogen in the estuary sections,estuary seawater and marine outfalls was mainly nitrate nitrogen.Mike model was constructed to simulate the influence of nitrogen in estuary sections on the background concentration in estuary seawater.Results showed that under the condition that the ammonia nitrogen concentration in estuary sections met the class II standard of surface water,the inorganic nitrogen concentration was relatively high in estuary seawater,which was affected by the nitrate nitrogen in estuary sections.It is found that over-standardization of inorganic nitrogen in estuary area is closely related to the disjoint of nitrogen index setting of land-sea water environment,and the unreasonable evaluation criteria in estuary area.In order to improve the quality of estuary seawater,the land-sea overall management should be strengthened.