| 摘要: |
| 总磷是长江流域备受关注的污染物。来自长江上游的物质输送对长江中下游、对入海口水域水生态都具有重要影响。研究了1998-2019时期长江上游和中下游之间的衔接断面暨三峡水库出水断面的磷通量及形态变化。整个研究时段分为3个阶段:1998-2002(阶段Ⅰ,三峡水库运行之前),2003-2013(阶段Ⅱ,作为过渡时期)及2014-2019(阶段Ⅲ,三峡水库实现175 m正常蓄水位且金沙江下游段向家坝和溪洛渡水库运行后),以阶段Ⅰ、Ⅲ为重点时段进行对比分析。研究表明,2014-2019年总磷年通量平均为5.67万t/a,比1998-2002年减少了38.0%;溶解态磷年通量为4.02万t/a,增加了60.0%;颗粒态磷年通量为1.67万t/a,减少了74.9%。磷的主导形态由颗粒态变为溶解态,溶解态磷通量占比由27.5%上升为70.9%;相应地,颗粒态磷通量占比由72.5%下降为29.1%。总磷、溶解态磷和颗粒态磷通量均表现为丰水期>平水期>枯水期。近20年来,水沙关系发生了巨大变化,含沙量(SS)与水量(Q)正相关性大幅下降,其拟合方程的斜率由1.44下降为0.10,R2由0.83下降为0.57。溶解态磷月通量在总磷月通量中的占比(λDF)随输沙量或泥沙含量(SS)的增加而减小的规律基本未变,2014-2019年λDF与SS的经验模型为λDF=1.2883-0.3688×lgSS(mg/L)。三大水库的拦沙作用和流域水土保持作用导致的水沙条件变化是磷通量及形态变化的主要原因。三峡水库出水生物可利用磷浓度升高及光能吸收增强对初级生产力的促进作用及藻类密度的影响等生态效应值得关注。 |
| 关键词: 三峡水库 磷通量 磷形态 时空变化 |
| DOI：10.18307/2023.0201 |
| 分类号: |
| 基金项目:中国长江三峡集团有限公司项目(0711596)资助。 |
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| Flux and form of phosphorus in overlying water at the effluent section of the Three Gorges Reservoir from 1998 to 2019 |
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Lou Baofeng1, Ouyang Xuejiao1, Yang Xia2
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1.Monitoring and Scientific Research Center of Yangtze River Ecology and Environment Administration, Ministry of Ecology and Environment, Wuhan 430010, P.R.China;2.China Three Gorges Corporation, Yichang 443000, P. R. China
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| Abstract: |
| Phosphorus (P) is a pollutant of great concern in the Yangtze River basin, which has an important impact on the water ecology of the Yangtze River basin. The P flux and form at the Three Gorges Reservoir (TGR) outlet section during 1998-2019 were studied, and the whole period was divided into three stages: 1998-2002 (stage Ⅰ, pre-TGR period), 2003-2013 (stage Ⅱ, as interim period), and 2014-2019 (stage Ⅲ, after TGR achieved 175 m normal water level and completion of Xiangjiaba Reservoir and Xiluodu Reservoir), and Ⅰ and Ⅲ as key periods in comparison. The results show that the average annual total phosphorus (TP) flux in stage Ⅲ was 5.67×104 t/a, 38.0% less than that in stage Ⅰ. Wherein, dissolved phosphorus (DP) flux and particulate phosphorus (PP) flux were 4.02×104 t/a and 1.67×104 t/a in stage Ⅲ, with an increase of 60.0% and a decrease of 74.9% comparing to stage Ⅰ, respectively. The main form of P has changed from particulate to dissolved. In 1998-2002, the DP flux accounted for 27.5% in TP flux, but rose to 70.9% in 2014-2019. Accordingly, the percentage of PP flux decreased from 72.5% to 29.1%. Seasonality of TP, DP and PP flux are shown as wet season>even season>dry season. In the past two decades, the relationship between runoff (Q) and suspended sediment (SS) has changed greatly, and the positive correlation between them has decreased significantly, the slope of correlation equation decreased from 1.44 to 0.10, and R2 from 0.83 to 0.57. The rule that the percentage of monthly DP flux decreases with increasing SS remains unchanged, and the empirical model was established as λDF=1.2883-0.3688×lgSS (mg/L) based on data during 2014-2019. The changes of P flux and form characteristics were mainly attributed to sediment trapping of three reservoirs and soil and water conservation in the basin. Attention should be paid to the ecological effects resulted from the increase of bioavailable P concentration and the enhancement of light energy absorption. |
| Key words: Three Gorges Reservoir phosphorus flux phosphorus form spatial-temporal variation |
