【作者】 曹琳；

【导师】 吉芳英；

【作者基本信息】 重庆大学 ， 环境科学与工程， 2011， 博士

【摘要】 三峡水库消落带被认为是长江沿线生态最为脆弱的地带,区别于任何现有消落带或人工湿地。在综合三峡库区消落带磷研究现状的基础上,论文基于2008年秋三峡水库首次蓄水至172.5米的契机,以三峡库区消落带首次逆季节干湿交替为线索,以沿江13个典型新生消落带为对象,结合水库“蓄清排浊”完整调蓄周期,研究得到了首次干湿交替消落带表层土壤/沉积物中内源磷的赋存形态、时空分布特征,揭示了磷在水-土壤/沉积物界面的源汇转化规律,及吸附、释放、转化、累积机理,为三峡库区消落带生态系统逐步形成演化过程中持续研究消落带沉积物磷迁移转化积累背景参考数据,为库区新生消落带内源磷控制提供理论数据参考,为三峡库区库岸水体富营养化污染控制提供科学依据。结果表明:①三峡库区消落带上覆水总磷含量11月<5月<8月,覆水水位越高,库区上下游总磷含量波动越小,趋于平稳,出露期消落带上覆水总磷沿程分布呈现上游(滩涝至万州段)至下游(云阳至秭归段)含量逐渐降低,沿程波动逐渐减小的趋势。成库初期消落带逆季节干湿交替特征对上覆水总磷季节变化影响不明显。②消落带出露期沉积物总磷呈现以下规律,5月沉积物总磷(716.40mg/kg)>8月沉积物总磷(658.65mg/kg),且覆水沉积物总磷>落干沉积物总磷,表明夏季水库开闸放水排沙,且消落带夏季出露期降雨资源丰富,致使出露消落带表层沉积物被冲刷排除,反映出三峡水库逆季节干湿交替调蓄模式有利于消落带表层沉积物内源磷素的排出,相对于本底土壤(TP 1006.26mg/kg)来说,从总磷水平上降低了沉积物再次覆水时潜在释磷风险,对控制消落带沉积物内源磷释放和防治库岸水体富营养化起到促进作用。③消落带逆季节干湿交替有利于相对稳定的闭蓄态磷、钙磷排出,有利于沉积物中活性较高的活性磷、有机磷累积,且累积量接近本底土壤中活性磷、有机磷含量水平,一定程度上增大了消落带再次覆水沉积物潜在释磷风险。④消落带本底土壤在2008年秋首次蓄水时,表现为以释放磷为主,覆水至11月则表现为吸附磷为主,表明成库初期,土壤主要呈现出由源到汇的转变。⑤原始沉积物、去除轻组有机质沉积物以及沉积物矿物质最大磷吸附量(Qm)随着有机质的逐步去除,逐渐降低,且干湿交替沉积物矿物质及本底土壤矿物质的Qm值(338.81mg/kg)基本处于一致水平,表明沉积物有机质特别是轻组有机质,控制着磷在表层沉积物上的释放。覆水沉积物、落干沉积物及本底土壤,除去轻组有机质后,Qm一致呈现出降低,且沉积物表现更为明显,表明干湿交替消落带表层沉积物固磷能力较本底土壤相比受轻组有机质影响更大,易解吸磷(RDP)随轻组有机质去除均呈现出升高的态势,表明沉积物轻组有机质去除对磷释放起促进作用。⑥模拟实验发现由于干湿交替过程中落干期有机磷、活性磷的累积,导致再次覆水时磷释放现象更为明显,且本底土壤较沉积物释放量更大。更多还原

【Abstract】 The water level fluctuating zone in Three Gorges Reservoir Area (TGRA) is considered to be the most fragile ecological zones along the Yangtze River belt, different from the any other existing fluctuating zone or artificial wetlands. Based on Phosphorus Research of TGRA and opportunity when water level reaches 172.5m for the very first time in 2008, this paper studies 13 newly typical fluctuating zones according to anti-seasonal wet-dry alternation. Furthermore, combined with entire cycle of "storing the clean and dredging the muddy", this research shows existing forms and distribution features of endogenesis phosphorous in the upper layer of soil /sediments of the first wet-dry alternation. This reveals source-sink law of phosphorous in water soil/sediment, complemented with mechanism of adsorption, release, transformation and accumulation, which accumulates reference data for continual research on phosphorous transformation and transfer and endogenesis phosphorous control during the gradual formation of TGRA eco-system. Finally, this article provides reference scientific basis for pollution control of eutrophication in TGRA. The results showed that:①The total phosphorus (TP) in overlying water in TGRA presents a climbing trend following as: November<May<August. Also, the higher the water level is, the fluctuation of TP in lower and upper reaches is smaller. During exposed period, TP in overlying water shows a declining trend from upper reaches (Tanlao to Wanzhou section) to lower reaches (Yunyang to Zigui section), as does the TP fluctuation. Therefore, anti-seasonal wet-dry alternation has little impact on TP in overlying water of TGRA during the initial phase of reservoir formation.②In exposed period, TP in sediments in TGRA presents the following patterns: TP (716.40mg/kg) sediment in May > TP (658.65mg/kg) sediment in August and TP in submerged sediment > TP in exposed sediment. It indicates the upper layer of exposed sediments were eroded because of abundant rainfall and water and sand discharge in summer, which presents anti-seasonal wet-dry alternation cycle is conductive to releasing endogenesis phosphorous. Compared with soils (TP 1006.26mg/kg), this reduces TP potential release risk on the next submerging and has a promoting effect on controlling endogenesis phosphorous and preventing and curing eutrophication.③Anti-seasonal wet-dry alternation is helpful to discharging relatively stable occlude phosphorus (O-P) and calcium bounded phosphorus (Ca-P) and promotes the accumulation of active phosphorus (Ac-P) and organic phosphorus (Or-P) in sediments which is close to Ac-P, Or-P in soils respectively. It increases the potential release risk in sediments on second submerging.④During 2008 fall, the first submerging, soils in TGRA presents a dominant release trend, whereas till November, this trend switches to absorbing, revealing soils transformed from source to sink in the initial phase.⑤The max adsorption quantity of phosphorus (Qm) in sediments, sediments with light fraction organic matter removal and sediments minerals all drop gradually with the removing of organic matter. Besides Qm (338.81mg/kg) in sediments minerals and soils minerals during wet-dry alternation stay in the same level, suggesting organic matter particularly light fraction organic matter controls the phosphorus release in the upper layer of sediments. After removing light fraction organic matter, Qm in submerged sediments, exposed sediments and soils all present a decreasing mode, especially obvious in sediments, which indicates the phosphorus stabilizing in upper layer in sediments were more affected by light fraction organic matter than that in soils. Readily desorbed phosphorus (RDP) in the same soils sample increases with the removal of light fraction organic matter, signifying light fraction organic matter removal stimulates the release of phosphorous.⑥Lab simulation experiment reveals that the wet-dry cycle can accelerate the phosphorus release on second submerging due to the accumulation of Or-P and Ac-P, additionally, release in soils are more in sediments.更多还原