南水北调中线水源区总氮污染系统治理对策研究

Countermeasures for total nitrogen pollution control in water source area of Middle Route Project of South to North Water Diversion

总氮污染易导致水体富营养化甚至诱发水华,为全面了解南水北调中线水源区总氮污染现状,有效掌握污染来源并制定系统治理对策,对水源区7个水库断面、16条入库支流和62个典型库湾进行了现场监测与资料收集工作。结果发现:丹江口水库历年总氮浓度在0.99~1.50 mg/L之间,均值为1.25 mg/L,并呈现逐年升高态势;硝态氮是水源区总氮的主要组成部分,平均占比70%左右;汉江及其支流总氮年入库负荷为2.706×104t,为水源区总氮负荷的主要来源;面源污染是水源区总氮升高的主要驱动力,对总氮输出负荷的贡献率在60%以上;耕地和居民地是面源污染总氮的关键源区。丹江口水源区总氮控制的关键是农业面源污染控制,应加强流域总氮浓度演变趋势及影响因素解析工作,建立源头-传输途径-汇水末端全链条控制对策体系。

The nitrogen pollution easily causes eutrophication and even algal bloom. In order to comprehensively understand the current situation of total nitrogen pollution in the water source area of the Middle Route Project of the South to North Water Diversion and effectively grasp the sources of pollution and formulate systematic countermeasures,the field monitoring and data collections of 7 reservoir sections,16 reservoir tributaries and 62 typical reservoir bays in Danjiangkou Reservoir area were carried out. The results showed that the total nitrogen concentration range of the Danjiangkou Reservoir was 0. 99 ~ 1. 50 mg/L with an increasing trend and the mean value was 1. 25 mg/L. The nitrate nitrogen was a main contribution to the total nitrogen with an average ratio of about 70%,and the annual load of total nitrogen entering into the reservoir from the Hanjiang River and its tributaries was 27. 06 × 103 tons,which was the main source of the total nitrogen. Non-point source pollution was the main driving force for the increasing of total nitrogen,accounting for more than 60% of the total nitrogen. Cultivated land and residential land were the key source areas of total nitrogen of non-point source pollution. The key countermeasure of total nitrogen control in the water source area is to control agricultural non-point source pollution. The study on evolution trend and influencing factors of total nitrogen should be strengthened,and the systematic countermeasures covering pollutant source,migration route and terminal should be established.