【作者】 艾蕾；

【导师】 史志华；

【作者基本信息】 华中农业大学 ， 资源环境信息工程， 2013， 博士

【摘要】 水环境污染是当今全球化的重大环境问题。我国水资源短缺且时空分布不均,水土流失面源污染引发的地表水体污染严重制约了人类生存与社会经济的快速可持续发展。针对我国规模宏大的跨流域水资源配置战略工程——南水北调中线工程水源区面临的潜在水土流失面源污染问题,以及丹江口水库水质安全、水环境健康与水资源长效利用的环境保护需求,基于水源区地形、土壤、气候、土地利用组成及土地利用格局等自然景观因子,借助遥感和地理信息系统等信息技术手段,综合采用野外实地调查、模糊决策理论方法、SWAT模型模拟预测、景观格局特征分析、偏最小二乘回归PLSR等多种方法手段,借鉴生态环境综合集成研究的思路,将南水北调中线工程水源区划分为多层次系统,从多方位、多角度逐级开展水源区不同流域土壤侵蚀影响因素的重要性差异、土壤侵蚀风险的时空分布与变化特征、土壤侵蚀产沙时空特征与演变趋势、流域水化学特性时空差异、不同景观特征与流域侵蚀产沙及水化学特性耦合关系的集成研究,为水源区生态环境建设、流域水环境质量保障、区域环境保护和经济社会可持续发展提供科技支撑。本文取得的主要结论和成果如下：(1)以南水北调中线水源区的核心生态安全保障区和水质保护最敏感区域丹江口库区为研究对象,在提取侵蚀响应单元基础上提出了适于大尺度区域土壤侵蚀风险快速评估的方法,构建的侵蚀风险评估最优化模糊决策树分类结果表明,库区土壤侵蚀风险等级被划分为5个类别：极低侵蚀风险、低侵蚀风险、中侵蚀风险、高侵蚀风险和极高侵蚀风险。月均降雨量为侵蚀最显著影响因素,当其处于相对较低等级时,土壤侵蚀其他因素影响明显偏小,侵蚀风险等级也相对较低；反之则地形坡度、土壤可蚀性和植被覆盖度的多因素综合影响作用更突出,且侵蚀风险也相对较高。(2)基于模糊决策树判别结果,综合分析库区侵蚀风险时空分布表明,库区高等级和极高等级侵蚀风险主要集中在6月到8月,其中以7月和8月分布最广,超过研究区总面积80%；其次为6月,分布达研究区总面积65%。11月到次年3月主要为低等级侵蚀风险,面积占研究区总面积超过90%。而中等级侵蚀风险主要分布在4月、5月、9月和10月,面积超过研究区总面积79%。此外,大量农田、稀疏草地和未利用地分布的陡坡区域在雨季显示出相对偏高的侵蚀风险,验证表明本研究提出的评估方法精度达到76%,在该区域适用且有效,值得推广应用到其他相似的大尺度区域。(3)以长江流域汉江水系最大支流、水源区水土流失多发地区堵河上游流域为研究对象,利用校准和验证后的SWAT模型进行1978、1987、1999和2007年的侵蚀产沙模拟,结果表明,4年中土壤侵蚀强度最大的子流域集中在流域北部；流域年均土壤侵蚀率分别为9.47、10.40、14.14、7.64t/ha；1978年和1987年子流域土壤侵蚀最大负荷位于8号子流域,1999年和2007年转移到34号子流域；流域年均产沙量分别为3.72、5.36、7.30、3.69t/ha,1978年流域最大产沙量为8号子流域,而1987年、1999年和2007年流域最大产沙量则分别为6、39和21号子流域。研究区侵蚀产沙变化与区域土地利用变化趋势一致。(4)研究选取的15个具有代表性的景观指数分析流域侵蚀产沙景观格局特征表明,107个子流域的景观格局特征相差较大,特别是平均斑块面积、斑块密度、Shannon多样性指数、边界密度、平均最近邻距离和最大斑块指数具有较明显的变异。利用偏最小二乘回归方法对研究区子流域尺度上的土壤侵蚀、产沙和泥沙输移比与土地景观格局耦合关系研究表明,三者与流域土地景观格局关系密切,其中Shannon多样性指数、聚集度指数、最大斑块指数、蔓延度和斑块连通度指数是控制流域土壤侵蚀和产沙的主要景观指数；当土地景观格局分散性较强且斑块数目较多时,土壤侵蚀和泥沙输出显著增加。(5)以丹江口水库水环境水质监测的9个典型入库支流流域为研究对象分析水化学特性时空差异发现,2005年溶解氧含量最高为白河、陶岔和旬阳,高锰酸盐指数和总磷含量神定河和张湾较高,氨氮含量神定河远高于其他支流,重金属砷含量差异不明显,石油类含量神定河最高。对比发现2006年至2009年水化学特性与2005年基本保持一致趋势,高锰酸盐指数、氨氮含量神定河远高于其他流域,总磷含量总体较低且神定河最高。研究区入库支流中神定河水质状况相对较差。(6)入库支流景观特征分析表明,城镇、林地、草地和农地面积比、地形坡度、流域面积和土壤有机质与其他变量相比变异更明显,景观指数中变异最明显的是最大斑块指数、蔓延度、景观形状指数、Shannon多样性指数和Simpson多样性指数。溶解氧主控因素为4个形态变量；对高锰酸盐指数贡献较大的为高程积分、城镇面积比、土壤有机质和总氮、斑块连通度指数；对氨氮和总磷贡献较大的为高程积分、流域面积、城镇面积比、土壤有机质和总氮、斑块连通度指数；重金属砷主控因素为流域面积、土壤有机质、最大斑块指数、景观形状指数；高程积分、城镇面积比、土壤有机质和总氮、斑块连通度指数、流域面积对石油类贡献性较高。总的来看,流域面积、高程积分、城镇面积比、土壤有机质和总氮、以及斑块连通度指数对入库支流水化学普遍具有较大影响。更多还原

【Abstract】 Water pollution poses a serious problem not only in China but around the world. Water resource is characterized by extreme shortage and uneven distribution in China. Diffuse pollution from soil erosion leads to surface water pollution, which restricts sustainable development of social-economy. For dealing with soil erosion and diffuse pollution emerged in water source areas of the Middle Route Project under the South-to-North Water Transfer Scheme, the study presented in this paper was undertaken based on landscape features including topography, soil, climate, pattern and composition of land use. According to the ideas of integrated eco-environment study, information technologies such as remote sensing and geographic information system were combined with reconnaissance field surveys, fuzzy decision theory, SWAT model prediction, landscape feature analysis and PLSR (partial least square regression) approach for studying soil erosion, sediment yield and water chemistry from multi-level perspectives across water source areas. The specific contents of this integrated study include importance of the dominating factors affecting soil erosion, spatio-temporal patterns and dynamic changes of soil erosion risk, spatio-temporal characteristics of soil erosion, sediment yield and water chemistry and their responses to landscape features in watersheds. This study can provide useful information for ecological construction, environmental protection, water quality assurance, and sustainable social-economic development in water source areas. The main results and conclusions of the present study are as follows:(1) The Danjiangkou Reservoir Area is the core region of ecological security and water quality assurance in water source areas, which was therefore chosen as one of the case study areas. Based on subdivided Erosion Response Units (ERUs), a fuzzy decision tree approach for rapid evaluation and mapping of monthly soil erosion risk across broad areas has been developed in this study. An optimal fuzzy decision tree was determined to classify monthly soil erosion risk into five levels, including very low, low, medium, high and very high. The most important factor impacting on soil erosion is mean monthly precipitation. Soil erosion risk is at a level of low or medium when the level of mean monthly precipitation is relatively low, no matter what degree the slope, soil erodibility and vegetation coverage are. However, when mean monthly precipitation is relatively high, soil erosion risk is influenced by more complex integrated effects from the slope, soil erodibility and vegetation coverage.(2) According to produced monthly soil erosion risk maps with five levels derived from the results of the fuzzy decision tree, high and very high soil erosion risk in the DRA is mainly concentrated in June to August, of which July and August show the highest erosion risk covering the largest area (greater than80%), followed by June which has a proportion of65%. November to the following March is dominated by low erosion risk which accounts for more than90%of the area while the medium risk level is dominant (greater than79%) in April, May, September and October. Besides, large tracts of farmland, sparse grasslands and wastelands distributed on steep slopes, which show a relatively high soil erosion risk in most rainy months. With a validated accuracy of76%, the efficiency of the presented method suggests it is worth attempting in other analogous broad area regions.(3) The Upper Du River watershed is the largest tributary of the Yangtze River and an erosion-prone area in water source areas, which was also chosen as one of the case study areas. The annual soil erosion and sediment yield distributions for the years1978,1987,1999and2007were simulated with the calibrated and validated SWAT model, which shows that the most intensively eroded sub-basins were situated in the northern part of the study area. The watershed-averaged soil erosion rates for the years1978,1987,1999, and2007were9.47,10.40,14.14, and7.64t/ha/yr, respectively. The maximum sub-basin loads of soil erosion in1978,1987,1999, and2007occurred in sub-basins8,8,34, and34, respectively. The watershed-averaged sediment yields for the years1978,1987,1999, and2007were3.72,5.36,7.30,3.69t/ha/yr, respectively. The sediment yield of the individual sub-basins varied significantly. The maximum sediment yields in1978,1987,1999, and2007were located in sub-basins8,6,39, and21, respectively. Soil erosion and sediment yield changed consistent with land use in the study area. (4) The15selected landscape metrics were used to analysis landscape pattern characteristics of soil erosion and sediment yield, which shows that the landscape characteristics of the107sub-basins in the analysis varied widely. Especially, the mean patch size (AREA_MN), patch density (PD), Shannon’s diversity index (SHDI), edge density (ED), Mean Euclidian nearest-neighbor distance (ENN_MN) and largest patch index (LPI) shows greater variances than other measures. Partial least square regression (PLSR) was used to explore the relationship between soil erosion, sediment yield, sediment delivery ratio and landscape pattern, respectively. The results show that Shannon’s diversity index (SHDI), Aggregation index (AI), Largest patch index (LPI), Contagion (CONTAG) and Patch cohesion index (COHESION) were the master factors controlling soil erosion and sediment yield. Greater interspersion and higher patch numbers of land cover types may significantly accelerate soil erosion and increase sediment export.(5) Nine typical tributaries in the Danjiangkou reservoir were chosen as the case study areas for characterizing the spatio-temporal patterns of water chemistry, which shows that the dissolved oxygen content was highest in Bai river, Taocha and Xun yang, while the content of potassium permanganate index and total phosphorus were relatively high in Shending river and Zhangwan. Compared with other watersheds, the content of ammonia nitrogen and petroleum in Shending river were highest, while the difference of arsenic content was not obvious. From2006to2009, water chemistry characteristics changed consistent with that in2005. The contents of potassium permanganate index and ammonia nitrogen were extremely high in Shengding river, which indicated that water quality in shending river was relatively poor.(6) Analysis of watershed characteristics for all the tributaries demonstrated that the proportion of urban area, forest, grassland and farmland, and the slope, watershed area and soil organic matter shows greater variances than other variables. LPI, CONTAG, LSI, SHDI and SIDI show greatest variances than other landscape metrics. Dissolved Oxygen was mainly controlled by the four morphometric variables, while hypsometric integral, proportion of urban area, soil organic matter, total nitrogen, and COHESION were the master factors of potassium permanganate index. The master factors of ammonia nitrogen and total phosphorus were almost the same with potassium permanganate index except watershed area. Arsenic was mainly controlled by watershed area, soil organic matter, LPI and LSI, while petroleum was mainly controlled by hypsometric integral, the proportion of urban area, soil organic matter, total nitrogen and COHESION. Summarily, watershed area, hypsometric integral, the proportion of urban area, soil organic matter, total nitrogen and COHESION determine the situation of water chemistry in the tributaries.更多还原