洱海北部入湖河流水质特征及其对北部湖区的影响

基于2016—2018年罗时江、弥苴河、永安江及洱海北部湖区监测数据分析，探讨洱海北部入湖河流污染变化特征及对北部湖区的影响。结果表明:1）"北三江"监测断面总磷、COD、氨氮浓度整体稳定在GB 3838—2002《地表水环境质量标准》Ⅱ—Ⅲ类标准限值内，年内污染物浓度变化表现出典型的农业面源污染特征，且受流域内产业模式等的综合影响；2）研究期间，河流首要污染物为TN，旱季次要污染物为COD，雨季为TP。雨季入湖负荷高于旱季，弥苴河污染负荷大于罗时江、永安江。"北三江"入湖TN和TP污染负荷分别占洱海允许负荷的50.1%和59.7%；3）入湖河流的磷元素输入是洱海北部湖区磷污染的重要来源。北部湖区污染物浓度对氮、磷入湖污染负荷相关性次月强于当月，响应存在延迟。筛选环境友好型种植模式，控制"北三江"氮磷入湖负荷，有利于保护洱海水环境。

WATER CHARACTERISTICS OF INFLOW RIVERS IN NORTHERN ERHAI LAKE AND THEIR IMPACT ON THE NORTHERN LAKE AREA

Based on the analysis of the monitoring data of Luoshijiang River, Mijuhe River, and Yong’anjiang River, and the northern lake area of Erhai Lake from 2016 to 2018, this paper explored the pollution characteristics of the rivers entering the northern Erhai Lake and its impact on the northern lake area. The results showed that: 1) TN, TP, COD, and ammonia nitrogen in the monitoring section of North Three Rivers fluctuated between wate quality ranks Ⅱ and Ⅲ. The change in pollutant content during the year showed typical agricultural non-point source pollution characteristics, and was affected by the industrial type in the river basin. 2) During the study period, the primary pollutant in the river was TN, the secondary pollutant was COD in the dry season, and TP in the rainy season. The load into the lake in the rainy season was higher than that in the dry season, and the pollution load on Mijuhe River was greater than that of Luoshijiang River and Yong’anjiang River. The pollution load on North Three Rivers into the lake accounted for 50.1% TN and 59.7% TP of the allowable load in Erhai Lake respectively; 3) The input of phosphorus from rivers entering the lake was an important source of phosphorus in the northern Erhai Lake. The correlation between pollutant concentrations in the northern lake area and the pollution load of nitrogen and phosphorus into the lake was stronger than that in the next month, so the response was delayed. Selecting eco-friendly planting models and controlling the load of nitrogen and phosphorus into the lake from the North Three Rivers was beneficial to protect the water environment.