三峡库区上游沱江流域总磷浓度时空变化特性及影响因素分析

Characterization of the spatio-temporal variations of total phosphorus concentrations and influencing factors analysis in Tuojiang River Basin,an upstream tributary of the Three Gorges Reservoir

沱江是三峡水库上游重要的入库河流和主要的总磷(TP)来源,研究沱江流域TP时空变化特性及其成因对三峡水库TP入库污染物允许通过量达标和流域TP污染治理具有重要意义。利用2011—2018年沱江流域干支流20个国控和省控监测断面的水质数据和断面汇流区污染源数据,采用Pearson相关性分析法、单因素分析法和层次聚类分析法,综合分析了沱江流域TP浓度时空分布特性及其影响因素。结果表明:2011—2018年,沱江流域TP污染已从上游绵远河、石亭江、鸭子河和中游釜溪河扩展到全流域,沱江干流上游主要受TP污染严重的支流汇入影响,TP浓度沿干流持续升高,在三皇庙断面出现浓度峰值〔(0.251±0.213)mg/L〕,中游和下游TP浓度表现出沿程波动的趋势,分别在银山镇〔(0.194±0.048)mg/L〕和大磨子断面〔(0.232±0.057)mg/L〕出现极值;沱江流域TP浓度总体表现为枯水期>丰水期,枯水期与丰水期TP浓度差异性显著(P<0.05);面源污染对沱江流域中下游内江、自贡和泸州段TP浓度的影响较大,点源污染主要影响上游干流成都市与资阳市区段以及内江市、自贡市境内支流的TP浓度。

The Tuojiang River is an important inflow river and the primary sources of total phosphorus(TP)in the upper reaches of the Three Gorges Reservoir.The study on the spatio-temporal variation characteristics and causes of TP concentrations in Tuojiang River Basin is important for the up-to-standard control of allowable throughput of TP in the Three Gorges Reservoir and the control of TP pollution in the basin.Based on the water quality data of 20 national and provincial monitoring sections of the trunk and tributaries in Tuojiang River Basin and pollution source data in the confluence area,the spatio-temporal distribution characteristics and influencing factors of TP concentrations in Tuojiang River Basin were comprehensively analyzed,using statistical methods,including correlation analysis,single factor analysis,and hierarchical cluster analysis.The results showed that from 2011 to 2018,the pollution of TP in Tuojiang River Basin had spread from the upper reaches of Mianyuan River,Shiting River,Duck River and the middle reach of Fuxi River to the entire basin.TP in the upper mainstream of Tuojiang River was primarily affected by the inflow of tributaries with serious TP pollution.TP concentrations increased continuously along the mainstream of Tuojiang River and reached the maximum in Sanhuangmiao section with(0.251±0.213)mg/L.TP concentrations floated in the middle and downstream reaches with concentration peaks occurred at sections of Yinshanzhen((0.194±0.048)mg/L)and Damozi((0.232±0.057)mg/L).TP concentrations in the flood seasons were higher than those in the dry seasons.The differences of TP concentrations between the flood and the dry seasons were significant with P<0.05.Non-point sources pollution contributed more on TP in Neijiang,Zigong,and Luzhou sections in the middle and lower reaches of Tuojiang River Basin.Point sources discharges mainly affected TP concentrations in Chengdu and Ziyang sections of the upstream trunk stream and tributaries in Neijiang and Zigong.