【作者】 王莹；

【导师】 潘学军；

【作者基本信息】 昆明理工大学 ， 环境科学， 2012， 博士

【摘要】 内源污染的实质是沉积物污染,在适宜的环境条件下,沉积物-水界面氮磷营养盐浓度差达到一定程度则会向水体释放,严重时可造成水体富营养化。同样,沉积物中的重金属和难降解的有机物在一定条件下也会向水体释放,通过生物富集对生物体产生较强的毒害作用,并有可能通过食物链威胁人类身体健康。现阶段,内源污染的治理研究已成为国际上环境保护工作的热点之一。我国也在重点湖泊的内源污染治理方面开展了大量的研究工作,在不同湖泊分别实施了底泥疏挖、生态修复、引水冲刷和原位控制等工程。然而,一直以来对各种内源污染治理技术都只是针对一种技术进行相关分析和效果预测,尚未有人对不同治理技术进行综合对比分析研究。因此,如何选用合理的治理技术,用有限的治理资金去取得最大的环境效益成为环境保护管理决策者面前的一道难题。滇池作为三湖治理的难点,其污染问题受到政府的高度重视和国内外学者的广泛关注。当前,滇池外源性污染在严格的环境监管体系下已得到较好的控制,而内源污染则成为水体污染控制所面临的严峻挑战。鉴于滇池治理的紧迫性和重要性,不同内源污染治理技术综合对比研究的缺乏性,本论文以滇池为研究区域,系统研究了滇池污染底泥疏挖及处置工程、滇池水葫芦圈养及资源化利用工程以及牛栏江-滇池补水工程三种不同技术对滇池内源污染治理的影响效果,旨在为滇池以及其他湖泊的内源污染治理工作提供科学依据。(1)通过对疏挖区和未疏挖区进行有无对比法研究,综合分析了疏挖工程对水体和底泥理化性质、氮磷营养盐、重金属和砷污染物以及生物多样性的影响,同时对底泥疏挖的社会效益进行了研究。水体和底泥的理化性质在疏挖后均有一定程度的改善。相比未疏挖区,草海南部疏挖区水体浊度平均降低5FTU,透明度平均升高11.5cm,盘龙江和大清河疏挖区变化较小；三个疏挖区水体电导率降低5-13s/m,而DO、pH、ORP等指标没有明显变化。盘龙江和大清河疏挖区底泥有机质含量和烧失量明显下降,含水率变化不大,而草海疏挖区含水率明显下降,有机质含量和烧失量变化不大；三个疏挖区粉粒含量均增多,粘粒含量则不同程度的减少。各疏挖区水和间隙水中不同形态氮磷含量基本低于未疏挖区,而重金属及砷在水中均未检出。各疏挖区底泥中污染物含量明显低于未疏挖区,经估算疏挖工程共去除总氮1.15万吨,总磷5432吨,Pb458.7吨,Cu439.8吨,Zn1030.5吨,Cd5.3吨,Cr365.7吨,As85.9吨。对外海两个疏挖区的柱状底泥进行氮磷形态分级,结果表明：疏挖后生物有效性氮含量相比未疏挖区大量减少,只有部分表层沉积物呈现出潜在的释放趋势；Ca-P和Fe-P所占总磷的比例较大,其随深度的变化和总磷相似,呈逐渐降低的趋势,而疏挖条件并未导致Ca-P和Fe-P的大量释放,对水体含磷量的影响不大。使用地质累积指数法和潜在生态风险评价法对沉积物中的重金属和砷的污染级别和潜在生态危害性进行评价,结果发现：疏挖区五种重金属和砷的污染程度均低于未疏挖区；以单个重金属的潜在生态危害系数进行评价,疏挖区的生态危害因子小于未疏挖区；以多个重金属的潜在生态危害系数进行评价,发现滇池表层沉积物中重金属和砷的生态危害总体处于轻微程度。对各水域浮游生物多样性的分析研究表明：疏挖区相较于未疏挖区,藻类生物量有所增多,生物多样性指数得到升高,但生物多样性总体处于极低水平,盘龙江和大清河疏挖区仍为重污水带。通过问卷调查的方式,研究了该工程的社会效益。绝大部分公众和被调查企事业单位对底泥疏挖工程持积极肯定态度,并具有较高的支付意愿；该工程为周围居民提供了一些就业机会,改善了生态景观和城市投资环境,促进了旅游发展；同时该工程也是一项生动的环保宣传活动,增强了人们的环保意识,具有较好的社会效益。(2)在水葫芦圈养种植期间,通过对滇池草海水质8个月的跟踪监测,初步研究了圈养水葫芦对滇池草海水体中氮磷营养盐的去除效果,分析了长期种植水葫芦对草海沉积物间隙水中氮磷营养盐的影响,评估了圈养水葫芦对湖泊内源污染的治理效果。结果表明,草海水域水体理化指标在2011年10月15日前均有不同程度的好转,水体透明度、溶解氧、氧化还原电位升高,pH和电导率降低；而10月15日后各理化指标呈现恶化的趋势。水葫芦在整个试验期间对水体中不同形态磷的净化效果明显,总磷、可溶性总磷和正磷酸盐分别由初始浓度0.44±0.09mg/L、0.17±0.01mg/L、0.15±0.01mg/L降至0.07±0.01mg/L、0.01±0.001mg/L、0.003±0.001mg/L,去除率为84.09%、94.12%和98.00%；而对水体中不同形态氮的净化效果不明显,在10月15日前,水体中总氮、硝氮和氨氮的最高去除率分别为17.24%、50.07%和75.76%,而至次年1月15日,水体中总氮和硝氮浓度明显升高,分别为5.09±0.76mg/L和3.34±0.08mg/L,氨氮浓度相对较低,为0.26±0.08mg/L。间隙水中主要以铵态氮和正磷酸盐为主,且不同形态氮磷浓度均呈现先升高后降低的趋势,表明水葫芦的圈养种植对沉积物中营养盐的释放产生了影响。各水质指标间的相关性分析表明,温度和pH是影响水葫芦净化水体的重要因素,温度升高和pH降低可以促进水体的净化；而pH值的上升则会引起沉积物中营养盐的释放,导致水质恶化。(3)通过搜集有关牛栏江补水工程的相关资料,对滇池水污染物最大允许排放量、生态环境补水量以及补水效果进行科学预测。运用二维水质模型得到2020年滇池污染物水平,外海平均水质TP浓度为0.10mg/L、TN为1.45mg/L,CODMn指标好于Ⅲ类水质目标要求,满足2020年滇池外海水质达到Ⅳ类水质的要求。运用零维模型,得到外海TN和TP的衰减系数分别为11.27/a和10.88/a,草海TN和TP的衰减系数分别为2.41/a和2.73/a,生态补水使滇池TN和TP的最大允许纳污量分别提高了约20%。为使2020年滇池水质基本满足其规划水质目标要求,滇池所需环境补水量约为5.5～6.5亿m3/a。本文对三种内源污染治理技术的对比研究表明,在滇池草海、外海入湖河口、外海东部、北部等沉积物污染较为严重、水体污染物浓度都较高的区域,可以优先实施底泥疏挖工程,随后实施水葫芦控制性圈养；在滇池外海湖区,由于水体本身较高的污染物负荷以及较长的换水周期,要快速改善滇池水质,在引水水源和资金充足的条件下可考虑实施引水工程。更多还原

【Abstract】 The essence of internal pollution is sediment contamination. In the appropriate environmental conditions, nitrogen and phosphorus would be released to water resulting from some extent concentration difference in sediment-water interface, which would cause the eutrophication. Similarly, heavy metals and refractory organics in sediments would be released under certain conditions also. They could be enriched through the biological enrichment and cause strong poison effect, while may threat the human health through food chain. Currently, the research of internal pollution management has become one of the hot issues in the international environmental protection. Large numbers of internal pollution management researches have been developed in major lakes in China. Some projects, such as sediments dredging, ecological restoration, water diversion and situ-control have been taken into measures in different lakes. However, the treatment technology of internal pollution has long been focused on the related analysis and outcome prediction for one specific technology, while the comprehensive comparison and study for different treatment techniques has not been carried out. So it is difficult for decision makers of environmental protection management to choose the appropriate technology, which can gain the maximum environmental benefits with limit management funds.As a difficulty of management among the Three Lakes, the pollution problem of Dianchi Lake had attracted the government and scholars’widely attentions. At present, external pollution of Dianchi Lake has well controlled under the strict environmental monitoring and managing system. However, the internal pollution has become the severe challenge to water pollution control. In view of the urgency and importance of the Dianchi Lake management, as well as the lack of comprehensive comparable research within the different internal pollution management technologies, Dianchi Lake was chosen as the study area in this paper that the effects of Dianchi Lake polluted sediment dredging and disposal project, captive breeding of Water Hyacinth and resource utilization project, and Niulan River-Dianchi Lake water diversion project in managing internal pollution were studied systematicly. It aims at approving scientific basis to internal pollution management in Dianchi Lake and other lakes. (1) Through comparing dredging and un-dredging areas with with and without comparison method, the influences of dredging project on physical and chemical properties, nitrogen and phosphorus pollutants, heavy metals and As loading, and biodiversity in water and sediment were analyzed in this paper, also the social benefits the project brought.The results showed that there were some improvements on the physical and chemical properties of the water and sediment. Compared with un-dredging areas, the average turbidity was5FTU lower and average transparency was11.5cm higher in dredging areas of southern Caohai, while there was little difference in Panlong River and Daqing River. Among the three dredging areas, the water conductivity decreased5-13s/m, and DO, pH, ORP didn’t change obviously. The organic matter contents and ignition loss decreased sharply, while the moisture contents didn’t change too much in dredging areas of Panlong River and Daqing River. However, these indexes were opposite in Caohai dredging areas. The silt contents increased and the clay contents decreased to different degrees in the three dredging areas.The contents of various forms of nitrogen and phosphorus in dredging areas were basicly lower than the un-dredging areas, while heavy metals and As were not found in water. The pollutants contents in dredging areas sediment were sharply lower than the un-dredging areas. It was estimated that11,500tons TN,5,432tons TP,458.7tons Pb,439.8tons Cu,1,030.5tons Zn,5.3tons Cd,365.7tons Cr, and85.9tons As were wiped off through the dredging project. The different forms nitrogen and phosphorus in core sediments of the two dredging areas in Waihai have been fractionized, the results showed that the bio-available nitrogen decreased sharply, and only parts of the surface sediments appeared potential releasing trend. Ca-P and Fe-P took a large portion of TP, and the variation trend with depth was gradually decreased, similar to TP. Dredging didn’t cause the Ca-P and Fe-P releasing largely, which had little affected on TP contents in water. By using the geological cumulative index method and potential ecological risk assessment method, the potential ecological risk of heavy metals and As have been assessed, the results showed that the pollution levels of five heavy metals and As in dredging areas were lower than the un-dredging areas. The ecological risk in dredging areas was less than the un-dredging areas resulting from the assessment of potential ecological risk factors of single heavy metal. While the ecological risk of heavy metals and As in surface sediment was in a slight degree, using the assessment of potential ecological risk factors of multiple heavy metals. The research of plankton diversity showed that, the alga biomass and diversity indexes in dredging areas were more than that in un-dredging areas, and the biodiversity was in a low level overall, while dredging areas in Panlong River and Daqing River were still polluted seriously.In this paper, the social benefits of the project were discussed through questionnaire. The results showed that the project was endorsed by the local people and the enterprises, the majority of the respondents were willing to donate for the project, believing that the dredging project had good social benefits by providing some employment opportunities, improving the ecological landscape and city investment environment and promoting tourism development. Meanwhile, the project was also a vivid propaganda about environmental protection which enhanced the citizens’ environmental protection consciousness.(2) Through8months monitoring of water quality in Caohai during the captive breeding of water hyacinth experiment, the removal efficiency of nitrogen and phosphorus by captive water hyacinth was investigated preliminary, and the influences to the pore water by long-term planting water hyacinth was analyzed, as well as the effects of improving internal pollution were estimated. The results showed that, the physics and chemistry index was better in different degrees before Oct15th in Caohai, transparency, dissolved oxygen, oxidation-reduction potential increased, while pH and conductivity decreased. However, the physics and chemistry index became worse since Oct15th. In the whole experimental periods, the various forms of phosphorus were purified notably, the contents of TP, DTP, and PO43-were decreased from0.44±0.09mg/L to0.07±0.01mg/L, from0.17±0.01mg/L to0.01±0.001mg/L and from0.15±0.01mg/L to0.003±0.001mg/L respectively, removal rates reached84.09%,94.12%and98.00%; While the various forms of nitrogen were purified poorly, the highest removal rates of TN, NO3--N and NH4+-N were17.24%,50.07%and75.76%before Oct15th. However, the contents of TN and NO3--N increased obviously since Jan15th in the following year, were5.09±0.76mg/L and3.34±0.08 mg/L respectively, while the contents of NH4+-N was comparatively lower,0.26±0.08mg/L. NH4+-N and PO43-were the essential components nutriment in the pore water, and the contents of various forms of nitrogen and phosphorus were increased at first and then decreased. It is indicated that the captive water hyacinth has affected the releasing of nutrient from sediment. The correlation analysis of the water quality indexes showed that temperature and pH were the key factors which affected the purifying capacity of water hyacinth, rising temperature or reducing pH could promote the purification effect; On the contrary, the nutrient in the sediment would release with the rising of pH.(3) The allowed maximum of pollutants emissions, supply water quantity of eco-environment and water supplement effect were forecasted scientifically according to the informations of the water supplement project in Niulan River. The pollutant levels in the year2020were calculated by two-dimensional water quality model that the average concentration of TP and TN were0.10mg/L and1.45mg/L respectively, the concentration of permanganate index reached the requirement of grade Ⅲ which meet the water quality of grade IV in Waihai of Dianchi Lake in2020. By using Zero-dimensional model, the attenuation coefficients of TN and TP were11.27/a and10.88/a in Waihai,2.41/a and2.73/a in Caohai, respectively. The maximum permissible quantity of TN and TP pollutants were increased by about20%. In order to meet the project objective, the environment diversion quantity was about5.5*109-6.5*109m3/a in Dianchi Lake.In this paper, the results of comparative study of the three internal pollution control technologies showed that the sediment dredging project should be carried out preferentially in the areas where sediment and water pollution was quite serious such as Caohai, the estuary and eastern, northern part of Waihai, then taken the water hyacinth control measure. Considering the high water pollutant loading and long lake residence period in Waihai of Dianchi, in order to improve the water quality quickly, water diversion project could be adopted if the water and funds are sufficient.更多还原