| 长江朱沱断面磷浓度与通量变化及来源解析 |
| 摘要点击 814 全文点击 195 投稿时间：2023-02-24 修订日期：2023-04-12 |
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| 中文关键词 长江 梯级水库 磷 通量 形态 源解析 |
| 英文关键词 the Yangtze River cascade reservoirs phosphorus flux form source apportionment |
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| 中文摘要 |
| 磷（P）是长江流域备受关注的污染物.金沙江下游向家坝水库和溪洛渡水库分别于2012年和2013年蓄水成库,极大改变了库区及长江宜宾至江津段（金沙江、岷江和长江“三江口”与三峡水库之间）水沙条件和磷的赋存及输移规律.朱沱断面是宜宾至江津段代表断面,既可以反映金沙江梯级水库及岷沱江水环境变化等所产生的综合效应,又是三峡水库的入库断面.研究了2002~2019年长江朱沱断面径流量、悬浮泥沙（SS）浓度与输沙量、磷浓度与通量[分总磷（TP）、溶解态磷（DP）、颗粒态磷（PP）]年际变化及水期特征,基于河流基流分割原理对磷的来源进行了解析.结果表明,18年来朱沱TP和PP浓度与通量丰水期高于平、枯水期；PP与SS正相关性的规律未变.从2002~2019年,TP、PP和DP浓度与通量总体上呈先升高后下降趋势,且向家坝水库运行是SS、输沙量和TP、PP浓度与通量下降的重要时间节点.相对于2002~2012年,2014~2019年SS与输沙量分别下降了94%和77%,TP与PP浓度分别下降了46%和70%,TP与PP通量分别下降了58%和74%,下降主要发生于丰水期,其次是平水期.两座水库形成后,水沙关系和磷赋存形态都发生了巨大变化,DP占比显著升高,PP占比显著下降,枯水期和平水期的磷已由颗粒态为主转变为以溶解态为主.水沙条件改变是磷浓度、通量及形态发生显著变化的主要驱动力.向家坝水库运行前,汇水次级流域中,金沙江对朱沱TP总负荷和面源负荷的贡献率最大,运行后变为岷江贡献率最大.2017~2019朱沱断面总磷负荷平均为3.575万t·a-1（扣除天然背景值后）,其中面源和点源贡献率分别为68%和32%；朱沱TP总负荷中岷江贡献率占49%,面源负荷中岷江贡献率占43%,点源负荷中岷江贡献率占62%.长江三峡水库上游磷污染治理的重点区域是岷沱江流域. |
| 英文摘要 |
| Phosphorus (P) is a pollutant of great concern in the Yangtze River Basin. The Xiangjiaba Reservoir and Xiluodu Reservoir on the lower reach of the Jinsha River began to operate in 2012 and 2013, respectively, which greatly changed the concentrations of suspended sediment and characteristics of P form and transport in the reservoirs and the downstream reach from Yibin to Jiangjin of the Yangtze River. The Zhutuo section is representative in the water quality of the Yibin-Jiangjin reach, which can not only reflect the comprehensive effects of the formation of the two reservoirs and changes in the aquatic environment in the Min-Tuo Rivers but also reflect the quality of water flowing into the Three Gorges Reservoir. The runoff, concentrations and fluxes of suspended sediments (SS), and P concentrations and fluxes at Zhutuo section were studied during 2002-2019, and the source of P was apportioned based on the principle of river base flow. The results showed that in the past 18 years, the concentrations and fluxes of total phosphorus (TP) and particulate phosphorus (PP) at Zhutuo section in the wet season were higher than those in the level and dry seasons; the rule of positive correlation between PP and SS concentrations remained unchanged. From 2002 to 2019, the concentrations and fluxes of TP, PP, and dissolved P (DP) generally increased first and then decreased, and the operation of the Xiangjiaba Reservoir was a time node for the trend turning. Compared with that in the period from 2002-2012, the SS concentration and flux decreased by 94% and 77%, TP and PP concentrations decreased by 46% and 70%, and TP and PP fluxes decreased by 58% and 74%, respectively, during 2014-2019. The decline mainly occurred in the wet season, followed by that in the level season. After the formation of the two reservoirs, the relationship between water and sediment and the form of P greatly changed, and the proportion of DP in TP increased significantly, whereas the proportion of PP was the opposite. The TP pool in overlying water in the dry and level seasons shifted from mainly particulate to mainly dissolved. The change in water and sediment conditions was the main driving force for the significant change in P concentration, flux, and form. Before the operation of the Xiangjiaba Reservoir, the Jinsha River was the maximum contributor to the whole and diffuse source part of the TP load at Zhutuo section among the contributing catchment sub-basins; however, the Minjiang River became the largest contributor after the operation. The average TP load at Zhutuo section from 2017-2019 was 3.575×104 t·a-1 (after deducting the natural background value), of which the contribution of diffuse sources and point sources accounted for 68% and 32%, respectively. The Minjiang River represented 49%, 43%, and 62% of the total TP load, diffuse source TP load, and point source TP load at Zhutuo section, respectively. Considering the load contribution and pollution intensity, the key area for P pollution control in the area upstream of the Three Gorges Reservoir was the Min-Tuo River Basin. |
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