【作者】 王铭玮；

【导师】 杨凯；

【作者基本信息】 华东师范大学 ， 环境科学， 2011， 博士

【摘要】 伴随着经济快速发展、人口迅速膨胀的过程,自然水体中所受纳的污染物总量逐年增加,特别是在城市化进程较快的长江中下游地区,浅水湖泊几乎全部富营养化。长江中下游地区分布的湖泊往往是其分布地区主要的饮用水源之一,近年来富营养化所引起的蓝藻暴发事件在这些水源地的发生频率和规模不断上升,威胁到饮用水供应安全,导致附近水厂被迫关停,严重影响了附近居民的生活和工业企业的发展。上海地处太湖流域下游和长江河口地区,从1985年起承担饮用水供应的淀山湖开始了蓝藻暴发的历程,而长江口地区新建的水库性水源地在蓝藻易发季节亦在局部地区出现大面积蓝藻聚集,如何控制蓝藻暴发成为上海城市饮用水源地亟待解决的安全问题。论文以黄浦江上游水源地和长江口水源地典型代表为研究对象,综合运用环境科学、环境工程、生态学以及管理学的理论和手段,在对水源地水环境、生态环境以及社会经济发展充分调研的基础上,结合室内模拟实验与野外生态调查的结果,从不同的角度分析上海城市饮用水源地蓝藻暴发的问题：对于已经出现蓝藻暴发的开放型水源地,按照“成因分析-评估-修复与应急响应”的思路,探索基于蓝藻暴发的水源地控制管理对策；对于存在潜在暴发风险的水库型水源地,采用“野外调查-模拟-预警和防控结合”的研究路线,探索水源地预警预控管理体系的建立,在对暴发因素研究的基础上形成上海地区城市水源地控制蓝藻暴发的控制管理体系。论文的主要研究成果可以概括为以下几个方面：1.主要水源地水质不断下降是上海市水源地重心转移的内在推动力。21世纪初上海饮用水源地正在经历三个主要变化：供水规模将由上世纪末的9.51×106m3/d逐步扩大至1.72×107m3/d；饮用水取水重心逐步从黄浦江转移至的长江口；城市主要的供水模式将由开放型水源地供水向水库型水源地供水模式过渡。对水源地水质分析的结果显示,水质变化的共性问题表现为氮、磷营养盐持续升高,水质不断下降,分散型内河取水口的水质劣于集中式水源地取水口,黄浦江上游水源地的水质劣于长江口水库水质,由此可见长江口水资源的开发最重要的作用是提升了上海优质饮用水的供给量。然而,水资源供给量的提高并不意味着上海市饮用水源地的矛盾得以解决,陈行水库在夏季高温天气中局部会出现蓝藻暴发,这种现象的出现意味着在未来相当长的阶段内,预防及控制蓝藻暴发都将成为上海市饮用水源地管理的重点。2.淀山湖蓝藻暴发是营养盐总量增加、生态系统退化以及特殊的水文、气象条件共同作用的结果。淀山湖目前氮、磷营养盐的净输入量分别由1985年的220.2 t/a、6.0 t/a上升至2009年的3026.5 t/a、39.3 t/a,造成净输入量增加的主要原因包括：上游来水的水量及营养盐浓度均大幅度增加,湖体自身的净化作用已经无法承受,尽管出湖区域的水质较好,仍有大量的营养盐滞留在水体里；淀山湖底泥较薄,湖泊生态系统较为脆弱,高等水生植物大面积的消失几乎瓦解了整个生态系统的基础,与此同时鱼类和底栖生物的生物量由于人为干扰强度过大而下降,在淀山湖营养盐条件充足的环境下,缺少竞争压力的浮游植物逐年成为影响生态系统演替的主要因素,其中蓝藻凭借特殊的生理机能逐渐成为浮游植物的优势种群。营养盐负荷增加仅仅是蓝藻暴发的充分条件之一,淀山湖蓝藻暴发的时间及地点不固定,在一定程度上意味着其他环境条件才是诱发蓝藻暴发的关键因素。通过对2007-2009年蓝藻暴发事件的分析,特别是对暴发时间、暴发区域(MODIS数据分析)以及暴发期内水文、气象因素的分析,可以归纳、总结出淀山湖蓝藻暴发的影响因素：上海地区夏季温度普遍较高,蓝藻的增殖速率加快,能够在短时间内达到较大的生物量；黄浦江涨潮的顶托作用以及太浦河下泄量增加带来的壅水作用,延长了淀山湖水力停留期,为蓝藻增殖提供了稳定的水文条件；蓝藻特有的浮力调节机制使其能够在低气压环境中上浮至水体表面,继而在低风速条件下聚集,最终形成暴发。蓝藻暴发是对水体营养盐过剩的一种自然反馈机制,不仅存在于淀山湖,长江中下游地区富营养化严重的浅水湖泊里已经成为常见现象,这种自然现象本身能够减少水体中营养盐的含量,但由于淀山湖面积较大,蓝藻不易收集捕捞,逐渐形成了困扰饮用水源地取水的主要因素,控制蓝藻暴发的根本性措施就是恢复湖泊原来的生态系统、增加生物多样性、延长营养盐循环的过程等。3.青草沙水库全面暴发蓝藻的可能性较低,但局部滞水区仍存在暴发的可能。长江口整体水质较好,陆源污染物排放的影响较小,但氮、磷浓度偏高的问题仍比较突出,已经逼近超标的临界值。在青草沙水库修建期内,长江原水氮、磷浓度下降,并且无机态的氮、磷比例较少,结合生态调查的结果,可以认为于水力停留期增加有利于浮游植物的增长,消耗部分营养盐,另一部分则可能沉积进入库区底部的泥沙中。青草沙库区内高等植物分布面积较广但种类单一,随着人为干扰的增强,有可能出现生物量下降的现象。浮游植物的总量及种类均低于淀山湖,并且随水温变化而增加在8月份达到生长高峰,在群落结构上已经完全转化为淡水水库型,以绿藻为主。水库的蓝藻种类与淀山湖不同,以颤藻属、鱼腥藻属等固氮型为主,生物量同样呈现随温度升高而增加的趋势,8月份水温升至顶点时在部分区域成为生物量最高的种类。蓝藻主要分布在水深较浅的库首及青草沙两侧,8月份在取水口附近测到较高的生物量,并且由于水库比热容较大导致水温下降速度较缓,蓝藻高生物量的状态可以维持到10月份,未来可能对水库供水产生不利因素。由于青草沙原水中营养盐浓度较低,蓝藻的倍增时间被拉长至20 d左右,甚至低于绿藻门的倍增时间,从根本限制了蓝藻生物量在短时间内大量增殖的可能。水温达到24℃时蓝藻生长最好,因此野外生物增加可以从5、6月份即开始,而光照对于蓝藻的影响并不明显,仅当水文条件被改变时,特别是水流速度加快时,蓝藻的生长受限制开始下降,10d左右在营养盐供给不够的前提下有可能分解、沉降甚至死亡,因此对于水库这种半自然水体而言,水力调度有可能成为水库蓝藻暴发最有效的控制措施。青草沙水库由于处在较低的营养盐水平,现有低营养状态下,以及氮磷限制、水力条件变化、水流速度增加、停留期缩短等影响,青草沙水库最长21天的连续停留时间内暴发蓝藻的可能性比较小,并且咸潮入侵的时间多发生在水温较低的阶段,延长停留期对于藻类生长而言无促进影响。但同时也需要注意,库区面积较大、水文条件也存在较大的差异,再加上底泥释放营养盐的影响,在部分滞水区以现在的营养盐状况,若遇到小范围内水力停留时间较长的状况,仍有可能形成大量浮游植物的累积。4.基于蓝藻暴发的上海城市水源地管理应充分考虑水源地类型、营养盐现状、水文特点以及历史暴发情况等,建立目标相同但控制措施有区别的管理体系。淀山湖蓝藻暴发概率高,管理体系应包含暴发后应急响应与控藻措施等两部分：基于时间特征指数的蓝藻暴发评估体系为淀山湖蓝藻暴发的预测提供了快速判断的准则,在此基础上采用拦藻、纳藻以及生物除藻的一系列应急控藻措施,来能够保障饮用水源地供水安全。但这些应急措施从根本上无法解决营养盐浓度过高的核心问题,因而需要采用改造湖滨带、恢复湖泊生态系统的长期控制对策,根据淀山湖湖区特性建立从近岸带到湖中心、从先锋种到建群种逐步恢复湖泊生态系统。青草沙水库生态系统和水质状况均比较好,蓝藻暴发概率较低,但这种半自然的水源地在不利水文气象条件下亦存在暴发的可能性。水库基于蓝藻暴发控制的管理体系应包括预警及防控技术相结合的策略,制定完备的蓝藻暴发预警方案,采用巩固水生植被、源头削减负荷、增加生态系统多样性等预控技术合理的调控,减小水库型水源地蓝藻暴发的概率。更多还原

【Abstract】 With a rapid increase rate of economic development and population expansion, the sum of pollutants in the water increased every year, especially in the downstream region of Yangtze River, which suffered a rapid urbanization process recently, the eutrophication occurred in every shallow lakes in that region. These lakes were the main drinking water source for the local residents, and due to the increase of the frequency and scale of Cyanobacteria blooming, the water supply was in danger, the water plant nearby was off-set. Shanghai is located in both the lower regions of Taihu Lake basin and the Yangtze River estuary region, and the first time of Cyanobacteria blooming occurred in Shanghai was 1985 in Lake Dianshan. Recently, Cyanobacteria blooming also appeared in the new reservoir in Yangtze River estuary region, so it became a urgent problem for the safety of the drinking water source in Shanghai. This thesis chose the water sources as the objects in upper stream region of Huangpu River and in Yangtze River estuary region, and used the theory and measurement of the environmental science, environmental engineer, ecology and management to analysis the Cyanobacteria blooming in Shanghai in many aspects, based on the results of the simulation experiments and the ecological survey. For the lakes, the research focused on the cause and evaluation of Cyanobacteria blooming, and set up a management system including the ecology restoration and response system fo rthe blooming. For the reservoir, the research method changed to ecological survey and stimulation, and the forces of management changed to early warning and control for the blooming. All the results showed below:The core of the water source in Shanghai had changed due to the deterioration of water quality. In 2010s, there were three main changes:the sum of water supply was gradually expanding to 1.72×107 m3/d from the level of 9.51×106 m3/d in the end of last century, and the new core of water source was Yangtze River estuary region, and the mode of water supply changed from the open resource to the reservoir. The analysis results showed that the main problem of water quality in different water source was the increasing concentration of nitrogen and phosphorus. The quality in minor rivers was more inferior to that of Lake Dianshan and Huangpu River, but the quality in Yangtze River estuary region was superior. In that case, the water quality of Shanghai would be improved by the water from Yangtze River estuary region, but it didn’t mean all the problems were solved. Occasional cyanobacteria blooming in Chenhang Reservoir in summer showed that the prevention and control of alga would last for a long time.Cyanobacteria blooming in Lake Dianshan were a complex consequence of nutrient increase, ecological degradation and environmental factors. The net input of nutrient was increase to 3026.5 tN/a in 2009 from the number of 220.2 in 1985, and the numbers in 2009 and 1985 for phosphorus were 39.3 and 6.0 tP/a. The causes included the net amount of the nutrient increase mainly from the increasing concentration of upper stream, which had overload. Another was the ecological degradation caused by Macrophytes disappear, and the biomass of fish and Benthos decreased. Phytoplankton became the key factor of the lake succession, and the biomass of cyanobacteria blooming became the largest.Increased nutrient loading was one reason of blooming, and another were the environmental factors, which effected the unfixed blooming time and region. The variations of blooming time, region (based on the results of MODIS analysis), hydrology and weather revealed some rulers about blooming in Shanghai during the cyanobacteria blooming in 2007-2009:the high temperature in Shanghai induced a large biomass in short time; the backwater effect to Lake Dianshan from Huangpu River and Taipu River extended the hydraulic retention period, and benefited the cyanobacteria proliferation; cyanobacteria floated up to the surface controlled by a special buoyancy regulation mechanism, and gathered in a low pressure, so the blooming formed eventually.Cyanobacteria blooming were a natural feedback mechanism to the nutrient overload in water. The blooming occurred in every shallow lake located in the downstream of the Yangtze River region. In this way, nutrients in water were reduced, but the cyanobacteria were not easy to collect due to a large area, so it became a main problem for drinking water supply. a fundamental measure for controlling outbreaks was to rebuilt the eco-system in Lake Dianshan by increasing biodiversity and extending the recycle processes of nutrient.The blooming possibilities in Qingcaosha Reservoir were quite low, but it didn’t include the stagnant water areas in the reservoir. The water quality in Yangtze River estuary was good, and the impact from land emission was low, but the increasing nutrient concentrations had been close to the respective limit values. The concentration of nutrient in Qingcaosha Reservoir was lower than the origin, and the ratios of inorganic forms was low, which means the consumption of nutrient were mainly from the increasing biomass of phytoplankton, especially for the cyanobacteria, and the less part were Deposition into the sediments.The distribution areas of macrophysics were large, but the construction was simple, and the biomass would decline if the human activities enhanced. The total amount and types of phytoplankton were lower than that of Lake Dianshan, but increased with the higher temperature, and the peak value appeared in August. The community construction of phytoplankton had been completely changed as the freshwater reservoir types. The main types of Cyanobacteria were Oscillatoria and Anabaena, increasing with higher temperature. The biomass of Cyanobacteria increased to the largest in some spots in August. Cyanobacteria are mainly distributed in the swallow water like the influent area and both side of Qingcaosha. The specific heat capacity of the reservoir was so high that the temperature in October was still benefit for the reproduction, and it may be an adverse factor in the reservoir.The double proliferate time of cyanobacteria was extended to about 20 days, even lower than chlorophyta, due to low nutrient concentrations in the reservoir, and it fundamentally limits the possibility of cyanobacteria blooming in the short period of time. The best temperature for cyanobacteria was 24, so the result of ecological survey showed that the biomass increase of cyanobacteria started from May, and the illumination did no effect on it. However, the changes in hydrology conditions could limit the growth of cyanobacteria, especially in a rapid flow.10 days was the longest time for cyanobacteria in a rapid flow without nutrient supply, and the cells became decomposition, or even death. So for the semi-nature reservoir, hydro scheduling may be the best management for the blooming control.Due to the reasons above, the possibility of cyanobacteria blooming in Qingcaosha Reservoir was low in a longest hydraulic retention period of 21 days, but considering the nutrients from the sediment, the blooming may appeared in some parts of the reservoir when the hydrological conditions changed.To control the cyanobacteria blooming in urban water source in Shanghai, the management should consider the types of water sources, nutrient status, hydrological characteristics and history of the blooming, and establish different management system for different water source aimed at the blooming control. The management system for Lake Dianshan includes two parts:emergency response and algal control measurement. The time-based feature evaluation index system was employed to evaluate the blooming in Lake Dianshan, and some control measures to protect drinking water sources. But these emergency measures couldn’t solve a fundamental core issue of excessive nutrient concentrations in the lake, so a long-term control measures including Lake Ecosystem Restoration need to adopt in the management system.Both the ecosystem and water quality in Qingcaosha Reservoir were in a good condition. Although the probability of the cyanobacteria bloomin was low, it still may appear in under the benefit hydrological or weather conditions in such a semi-nature water source. The management should include both the early warning, prevention and control strategy, in order to establish a stable ecosystem in the reservoir, cut off the source load, increase the diversity, et al., aimed to reduce the probability of the cyanobacteria blooming更多还原