亚热带河道型水库沉积物-水界面磷赋存形态与迁移转化机制

Speciation,migration,and release mechanism of phosphorus at the sediment-water interface of subtropical river-type reservoir

由水库建设引起的河流湖库化和富营养化,是全球普遍面临的重大生态环境问题.而内源污染负荷过大会加剧水库富营养化和水质恶化的风险.因缺乏亚热带河道型水库沉积物中内源磷污染解析,本文采用薄膜扩散梯度(DGT)和高分辨率渗析技术(HR-Peeper)以原位、高分辨率技术对河道型深水水库闽江水口水库中磷(P)、铁(Fe)、锰(Mn)、硫(S)进行监测,并研究河道型水库P-Fe-Mn-S的地球化学耦合机制以及磷的赋存形态和迁移释放机制.结果表明:氢氧化钠提取磷(NaOH-P)是沉积物中磷形态的主要形式,铁结合态磷是控制沉积物磷释放的关键因素,水口水库水体和沉积物营养化程度高,沉积物内源磷污染较严重;在垂直剖面上,沉积物中的P与Fe、Mn、S呈显著正相关,铁锰氧化物的还原溶解和硫酸盐还原有利于磷活化和释放;沉积物中P、Fe、Mn、S会形成正释放从而扩散到上覆水中,在水库开闸和泄洪期间,对流会暂时打破分层,内源磷的释放高于多数天然浅水湖库,这突出了河道型水库内源磷污染治理的重要性和紧迫性.

The construction of reservoirs leads to the transition of rivers to lakes and reservoirs,leading to a global environmental issue known as eutrophication.Excessive endogenous pollutant loads further exacerbate the risk of reservoir eutrophication and water quality degradation.Due to the lack of analysis of endogenous phosphorus pollution in sediments of subtropical river-type reservoirs,a study was conducted to investigate the geochemical coupling of phosphorus(P)with iron(Fe),manganese(Mn),and sulfur(S),as well as the speciation,migration,and release mechanism of phosphorus.The high-resolution distribution of P,Fe,Mn,and S in the riverine deep-water reservoir(Shuikou Reservoir)was measured using diffusive gradients in thin films(DGT)and high-resolution dialysis(HR-Peeper).The results showed that the NaOH-P(NaOH extracted P)was the main form of phosphorus in sediments;iron-bound phosphorus was a key factor controlling phosphorus release from sediments;water and sediments were highly nutrient-rich,and endogenous phosphorus pollution was serious in sediments of Shuikou Reservoir;in vertical profiles,P in sediments correlated significantly and positively with Fe,S,and Mn.The reduction and dissolution of Fe/Mn oxides and sulfate reduction were conducive to the release and activation of phosphorus.The positive diffusion fluxes of P,Fe,Mn,and S at the sediment-water interface indicated that the sediments would release these materials to the overlying water.During the opening and release of reservoirs,convection temporarily break stratification,resulting in a higher release flux of endogenous phosphorus compared to most natural shallow lakes and reservoirs.These findings underscore the importance and urgency of addressing endogenous phosphorus pollution in riverine reservoirs.