千岛湖区域生态风险评价研究

【作者】 文军；

【导师】 魏美才； 唐代剑；

【作者基本信息】 中南林学院 ， 生态学， 2004， 博士

【摘要】 千岛湖是解放初期国家在浙江西部淳安县境内建设新安江大坝之后蓄水形成的大型深水人工湖泊，其兼具有发电、防洪、灌溉等多项功能。改革开放后，千岛湖的旅游功能不断提升，先后被评为国家级重点风景名胜区和国家级森林公园，2001年被评国家AAAA级旅游区和国家级生态示范区。随着区域经济特别是旅游开发活动的升温，千岛湖流域正面临着开发过程中不断增强的人为活动的影响。客观科学地评价由此所带来的生态风险问题，是指导千岛湖区域经济与生态环境协调发展的理论基础。本研究以生态风险评价基本理论为指导，在环境现状评价的基础上，对近10年来的常规监测数据、酸雨、底泥进行了系统分析，构建了水域生态风险胁迫因子总氮和总磷的预测模型，最后从风险管理对策和风险管理技术两方面提出千岛湖区域生态风险管理体系。主要研究结果如下： 利用2002年的环境常规监测数据，对千岛湖区域的生态环境质量现状进行了定量评价，全湖水质达到饮用水水质标准。但是，千岛湖区域酸雨污染问题非常突出，千岛湖局部区域水质已受到一定程度的污染，影响千岛湖平均水质的最主要污染因子是TN，其次为TP，再次是高锰酸盐指数、粪大肠菌群及BOD₅。全湖水质分析的结果表明，TN的污染负荷比高达50％，TP的污染负荷比为17％，高锰酸盐指数、粪大肠菌群及BOD₅的污染负荷比分别为12％、9％及8％，其余项目污染负荷比只占4％。从富营养化评价结果显示，总体评分为35.8分，全湖水质已为中营养状态。此外建筑扬尘、油烟污染、噪声等环境污染也比较突出。 通过对千岛湖区域的生态风险源与胁迫因子的系统分析，确定了本区域生态风险源主要有农业污染、城镇化、采矿业、点源排污、交通运输、大气沉降、旅游业、畜牧水产养殖业、林业、外来生物入侵、洪水灾害等。区域风险胁迫因子主要是有毒化学物质、病原体、营养物质等方面。确定了以千岛湖水质变化为生态风险评价终点，并提出了以保持或提高本区域水质；遏制区域内酸雨恶化或劣变趋势；本区域的濒危物种种群数量的恢复与增长；保证水力发电、防洪与灌溉的需要；延长水库的使用寿命；保障娱乐与旅游业的需要等为区域生态风险管理目标。 千岛湖水质综合污染指数分析，近十年来千岛湖多数监测项目和各断面污染指数都出现显著下降的趋势，全湖综合水质出现趋好的走势，表明千岛湖总体水质的变化正处于相对低的风险状态之中。各断面水污染综合指数的对比分析显示，代表千岛湖三个主要来水水质的街口、航头岛和百亩畈三个断面分列前三，通过河流污染物的输入是千岛湖水质下降的主要风险来源，其中街口指标显著高于其它断面，它是正常年份中污染输入强度最大的来源。各监测项目污染指数的对比分析表明，总氮、溶解氧和高锰酸钾指数排列前面，仅有总氮项目的综合污染指数高出国家标准限值，各断面的总平均值达到1.6，而其它各项均低于0.5，说明总氮的输入是在近期千岛湖水质下降风险中首要问题。根据各断面水质污染综合指数负荷比的比较分析，街口、航头岛和百亩畈三个断面排在前列，街口该指标远高于其它断面，多年平均负荷比高达17％。趋势分析中，除街口和西园码头外其它各断面负荷比均表现出不同程度的下降趋势，表明它们对整体水质上升的贡献不高，分别表现出入湖水质和人为活动在延缓水质上升过程中的不利影响。在考核各监测项目综合污染指数分担率的分析中，总氮、溶解氧和高锰酸钾指数排在前列，三项分担率之和达全湖71％，其中总氮接近49％，显著地高于其它项目。趋势分析中总氮的分担率出现了显著性的下降趋势，同时其它项目也都表现出不同程度的下降趋势，大肠杆菌的变化趋势尚不明确。以有序聚类法分析全湖水质变化趋势的一致性结果显示，1998至1999年是千岛湖水质状态变化规律的最优分割点，并且在1998年后全湖总体水质上升的一致性明显高于此前各年份变化过程。 洪水对千岛湖的水质构成极为严重的威胁，19%年洪灾中千岛湖总体水质在多年走势图中出现“污染峰r，现象，表明外来面源污染是主要污染来源。根据洪灾前后水质变化对比分析，千岛湖水体受洪灾的影响仅局限于当年，通过水体的缓冲和自净能力的恢复，各项污染指数在灾后都能迅速恢复至止常状态。在洪灾年中，水质污染指数排序及负荷比均是百亩贩、航头岛、街口和三潭岛，四断面总负荷达到全湖72%。与正常年份不同，百亩贩是洪灾中水质最差的断面，根据洪灾年与灾前年的污染指数比值显示，水质变化对洪灾的敏感性次序是百亩贩、航头岛、二潭岛和街口，受洪灾影响变化最大且对全湖水质影响最大断面均是百亩贩和航头岛，二者上升幅度达到三倍之多。对洪灾年的各项监测项目的分析显示，洪灾年中综合污染指数对全湖分担率最高的是大肠杆菌和总氮，其它各项目分担率很低，对洪灾年中的总体水质几无影响，大肠杆菌分担率高达46.6%，取代了总氮的位置成为洪灾年中水质的最大污染因素。洪灾年与灾前年的污染指数比值显示，对洪灾影响敏感而污染指数发生迅速上升的监测项目依次是大肠杆菌、总锅、氨氮、总错和总氮，其它项目无明显变化。，又肠杆菌在洪灾年中的问题显得特别突出?更多还原

【Abstract】 Qiandao Lake, located in Chun’an County, Zhejiang Province, is a large-scale artificial lake with diverse practical functions, such as electricity generation, flood prevention, and agricultural irrigation. It came into being as a result of the Xin’anjiang Dam project in early 1950’s. Since China implemented the reform and opening policies in late 1970s, Qiandao Lake has been recognized as both a key national scenic area and a national forestry park. In 2001, it was further appraised as an AAAA tourist destination and a national ecological demonstration zone. However, due to the increased regional economic development, especially tourism development, Qiandao Lake is facing more and more severe threats from human activities.It is cf great importance to assess the emerging ecological risk in this area in order that the regional economy and ecological environment can co-develop in a harmonious manner. Under the direction of relevant ecological risk assessment theories, this study: assesses the current environmental situation of Qiandao Lake; makes a systematic data analysis of the water quality, acid rain and bottom mud in recent ten years; constructs the mathematical forecasting models of the ecological risk stress factors TN and TP; brings forv/ard the ecological risk management system, specifically risk management countermeasures and risk management technologies. Major conclusions are described as follows.The ecological environment quality of the Qiandao Lake region was assessed quantitatively with Year 2002 data. The result indicates that its water quality meets the drinking water standards. However, the acid rain issue of the Qiandao Lake region is serious. In some areas, the water has been polluted to some extent. The most significant water pollution factor is TN, followed by TP, potassium permanganate index, fecal coliform, and BOD5. The water quality analysis of the whole lake area shows that the pollutant load ratio of TN reaches as high as 50%, TP 17%, potassium permanganate index 12%, fecal coliform 9%, BOD5 8%, and rest items only 4%. The score of eutrophication assessment is 35.8, indicating that the water quality of the whole lake area has been in mesotrophic status. Moreover, other environmental pollution sources such as construction dust, lampblack, and noise are also comparatively prominent.A systematic analysis of the sources of ecological risk and the stress factors of the Qiandao region demonstrates that the major sources of ecological risk are agricultural pollution, urbanization, mining, point-source discharge, traffic and transportation, atmospheric sedimentation, tourism, stockbreeding and aquaculture, forestry, nonnative invasive species, floods, etc. Major regional risk stress factors are toxic chemicals, pathogens, and nutriments. Taking the changes of water quality as the endpoint of ecological risk assessment, this study brings forward the objectives of regional ecological risk management, i.e., keeping or improving the water quality, controlling the worsening of acid rain, resuming and increasing endangered species, guaranteeing electricity generation, flood prevention and irrigation, prolonging the reservoir’s longevity, meeting the needs of entertainment and tourism, etc.According to the analysis of the comprehensive pollution index, in recent ten years most monitoring items and sectional pollution indexes demonstrate a notable declining tendency, which indicates that the water quality of Qiandao Lake is faced with relatively low risk. The comprehensive water pollution index comparisons among sections show that the sections of Jiekou, Hangtou Island, and Baimufan, which represent the three main water sources of Qiandao Lake, are the most serious three. The pollutants inputted through rivers are the primary threat of the water quality. Jiekou has the highest intensity of contamination input in normal years. Its index is significantly higher than that of other sections. The comparative analysis of the comprehensive pollution indexes of all monitoring items shows that the indexes of to更多还原