环洱海主要入湖河流水质特征及入湖污染负荷估算

Water quality characteristics and pollution load estimation of main rivers around Erhai Lake

为了揭示洱海主要入湖河流的污染特征,2014年1月至2016年12月期间,以总氮(TN)、总磷(TP)、氨氮(NH_(3)-N)、化学需氧量(COD_(cr))为污染物指标,对27条主要入湖河流进行水质、水量监测以及沿程追踪调查。同时结合同期降水数据和湖区水质监测资料分析,阐述了洱海主要入湖河流水量水质特征,估算了入湖污染负荷,并评估了入湖污染负荷对湖区水质的影响。研究结果表明:①2014~2016年27条主要河流入湖总水量在2.87亿~4.74亿m^(3),汛期入湖水量分别占全年入湖水量的79.17%,74.90%和61.96%,入湖水量与流域降水量呈正相关关系;②在时间尺度上,污染物浓度年内整体呈现先升高后降低的波动趋势,雨季水质总体较好,污染物浓度空间上的差异不如时间尺度上的明显,污染物浓度与流域降雨量呈显著负相关;③洱海入湖污染负荷年内呈先降后升再降的趋势,入湖负荷主要受水量控制,污染负荷贡献率顺序为北岸>西岸>东-南岸,入湖河流总氮输入量与湖区总氮浓度、总磷输入量与湖区总磷浓度均呈极显著正相关,是洱海氮磷的重要来源。

In order to reveal the pollution characteristics of the main rivers into Erhai Lake,the water quality and quantity of 27 main rivers into Erhai Lake were monitored and investigated from January 2014 to December 2016 with total nitrogen(TN),total phosphorus(TP),ammonia nitrogen(NH_(3)-N)and chemical oxygen demand(COD_(Cr))as pollutant indices.This paper expounded the water quality characteristics of the main rivers into Erhai Lake,estimated the pollution load into the lake,and evaluated the impact of the pollution load into the lake on the water quality of the lake area.The results showed that:①The total amount of water entering the lake from 27 major rivers from 2014 to 2016 was 287~474 million m^(3),and the amount of water entering the lake during the flood season accounted for 79.17%,74.90%and 61.96%of the annual water entering the lake respectively in three years.There was a positive correlation between the amount of water entering the lake and the precipitation in the basin.②On the time scale,the pollutant concentration showed a fluctuating trend that first increased and then decreased in a year.The water quality in the rainy season was generally better,and the spatial difference in pollutant concentration was not as obvious as on the time scale.Pollutant concentration was significantly negatively correlated with rainfall.③The pollution load into the lake first dropped,then rose and then dropped in a year.The load into the lake was mainly controlled by the amount of water.The order of the pollution load contribution rate was north bank>west bank>east-south bank.Correlations between the total nitrogen load of into-lake rivers and the total nitrogen concentration in the Erhai Lake,and the correlation of phosphorus load of into-lake rivers and the total phosphorus concentration both showed a very significant positive correlation.The load of nitrogen and phosphorus input by rivers into the lake was an important source of nitrogen and phosphorus in Erhai Lake.