【作者】 丁恩俊；

【导师】 谢德体； 魏朝富；

【作者基本信息】 西南大学 ， 农业资源利用， 2010， 博士

【摘要】 当前,随着水环境问题的日益突出及点源污染控制水平的逐渐提高,面源污染尤其是农业生产和农村生活引起的农业面源污染问题己成为当今水环境污染的主要污染源,严重威胁着人类的生存与发展,并成为世界各国普遍关注的热点问题之一。农业面源污染形成的根本原因在于人类不合理的土地利用活动,它与土地利用类型、不同土地利用类型组合结构以及土地利用空间分异特征和土地利用管理措施等因素关系紧密。鉴于此,目前围绕土地利用与面源污染的关系已开展了诸多研究,但主要侧重于不同土地利用对面源污染的影响,关于不同土地利用与面源污染之间关系的定量研究以及据此构建适宜的土地利用优化模式和管理措施以控制农业面源污染的研究甚少,更没有一种系统的、可靠的研究理念和研究范式。三峡工程是举世瞩目的特大型水利工程,工程生态环境影响是国内外关心的重大问题,其中三峡库区水质问题则是关注焦点。三峡水库作为我国的战略水资源库,其水质状况不仅影响到三峡库区居民的生活、生产用水安全,同时也对长江中下游地区居民生产生活、经济发展以及南水北调工程的成败产生十分重要的影响。目前随着三峡工程的竣工和运营,工程生态环境影响逐步突现。由于库区特殊的生态环境条件和移民压力,特别是库区农业化学品的不合理投入、种养殖有机废弃物不合理排放等,农业面源污染日益严重,部分支流己出现“水华”现象。以上种种导致库区水质状况不容乐观,水环境安全问题令人担忧。面源污染是导致受纳水体水质恶化重要原因之一,因此,尽快开展面源污染控制措施研究已刻不容缓。能否针对三峡库区脆弱生态环境特点和农业面源污染发生特征,对三峡库区不同土地利用格局下的面源污染进行研究,提出适宜的面源污染控制的土地利用优化模式及管理措施,对三峡库区面源污染防控和水质保护具有重要的理论价值和现实意义。鉴于此,本研究引入土地利用优化配置这一概念,并根据三峡库区流域脆弱生态环境特征和农业面源污染发生特征,提出了三峡库区农业面源污染控制的一个理念——整体优化(规划)控制,局部关键(管理)控制,和一个范式——农村居民点-旱坡地-水田-消落带多重拦截与消纳农业面源污染物的综合防控技术体系和控制模式,据此确定了三峡库区农业面源污染控制的土地利用优化途径。同时在三峡库区重庆段涪陵区珍溪镇遴选了一个封闭的典型农业流域——王家沟小流域为例进行了实证分析。通过在王家沟小流域广泛的实地调查获取了大量的基础数据,并通过地理信息系统(Geographic Information System, GIS)与现场监测和定位实验结合的技术手段以及景观生态学的研究方法,探讨了该小流域土地利用与面源污染的关系,构建了流域最佳土地利用优化模式和管理措施,进而提出了解决三峡库区面源污染的控制理念和措施。具体思路是,首先利用实地调查和实测数据分析了土地利用对土壤养分、农业面源污染物影响,并据此构建了农业面源污染控制的土地利用整体优化调控模式,同时筛选出农业面源污染关键源区及敏感的土地利用类型,最后在关键源区及敏感的土地利用类型上实施相应的控制措施,并对其实施效果进行预测和评价。本研究取得了如下成果：(1)三峡库区小流域面源污染基础数据库建立根据研究需要,对三峡库区王家沟小流域自然环境和社会经济状况进行了全面调查,结合现场测绘和实地调查结果,在1：1000地形图调绘基础上,采用GIS软件获得土地利用类型图,并建立小流域数字高程模型(Digital Elevation Model, DEM)、坡度和坡向情况；并对小流域交通和农用基本设施等进行了初步规划布局；同时根据调查资料,分析了小流域主要面源污染来源。据此构建了面源污染基础数据库。该工作为进一步开展面源污染后续研究并提出适合王家沟小流域甚至三峡库区特征的面源污染控制工程及技术措施提供系统的、可靠的基础资料支撑。(2)三峡库区小流域土壤养分空间变异及其对土地利用格局的响应采用地统计学与GIS相结合的方法,以三峡库区王家沟小流域为研究区,研究了表层土壤(0-20cm)的pH值、有机质(soil organic matter, SOM)、全氮(total nitrogen, TN)、全磷(total phosphorus,TP)、全钾(total kalium, TK)、碱解氮(available nitrogen, AN)、有效磷(available phosphorus, AP)和速效钾(available kalium, AK)等8种养分的空间变异特征。研究结果表明：(1)SOM的含量普遍较低,AN的含量普遍较高；土壤养分的变异系数大小是AP(99.7%)>AK(39.7%)>TP(37.4%)>SOM(27.2%) >AN(26.1%)>TN(21.6%)>pH(19.9%)>TK(15.7%),均为中等程度的空间变异性；土壤pH、TP和的AK半方差函数理论模型为球状模型,SOM、TN和AP为指数模型,TK和AN均为线性模型；pH具有强烈的空间相关性,结构性因素是影响其空间变异的主要因素,其余土壤元素存在中等的空间相关性,随机因素引起的空间变异性所占比重较大。(2)pH值沿东南到西北逐渐增加,多数区域土壤呈酸性微酸性。SOM除东南有高值区外,其他地方由中心到四周辐射降低。TN值由中间向两翼降低。TP值除东北、西北有大片高值区和中部偏东有少量高值区,其他部分则由中部向四周递增。TK值则较破碎,在西北、东南有高值区。AN值由东北、西北向南部,逐渐增加。AP值在西北、东南有高值区,其他地方变异不大。AK值由中部向东北西南降低,大部分区域AK含量处于较高水平。(3)不同土地利用类型其养分含量差异显著,园地的pH值、TP和TK均高于其他地类,与此同时园地的SOM、AN和AK也都低于其他地类；旱地的SOM、TN和AN均高于其他地类,其中AP却低于其他地类；林地的AK最高,但pH、TN、TP和TK又是最低；水田AP含量明显高于其他地类。研究结果可为小流域综合治理中土壤养分管理、农业面源污染控制与植被恢复提供理论依据。(3)三峡库区小流域面源氮(N)污染时空变异及其对土地利用格局的响应为揭示三峡库区小流域面源N污染的时空分布特征,以位于三峡库区腹心地区的王家沟小流域为研究对象,在自然降雨条件下,通过2008年9月～2009年11月期间11次对沟渠、塘、井3种水体水质中的总氮(Total Nitrogen, TN)、溶解态氮(Dissolved Ditrogen, DN)、硝态氮(Nitrate-N,NO3-N)、氨氮(Ammonium-N, NH4-N)等不同形态N素野外水样监测分析以及流量的测定,研究了王家沟小流域面源N污染的时空变化规律。研究结果表明：(1)该小流域N素污染非常严重,其浓度最高达到45.27mg/l,每次都超过地表水V类标准,这与该区是典型的农业耕作区有关；(2)从空间尺度来看,同一时间不同水体中不同N素平均浓度变化趋势为：TN(井)>TN(沟渠)>TN(塘),DN(井)>DN(沟渠)>DN(塘),井中的硝态氮大于其他塘和沟渠两种水体中的硝态氮,这与不同水体周边有不同的土地利用方式密切相关；(3)从季节变化来看,N素的最高输出浓度与负荷的季节,不是发生在雨水丰盛的夏季,而是发生在细雨的秋季,输出负荷跟径流量成乘幂回归关系,输出负荷最高的两月分别是11月和10月,整个小流域中总氮月输出负荷最高达到1233kg。(4)从N素输出形式来看,主要以溶解态为主,但也有个别月份输出以颗粒态为主的,这主要是与土地利用方式和降雨密切相关。(4)三峡库区小流域土地利用格局优化分析农业面源污染“起”于人类不合理土地利用活动,它与土地利用类型、不同土地利用类型组合结构以及土地利用空间分异特征等因素存在着紧密关系,相应地农业面源污染控制应“止”于人类合理土地利用活动,通过土地利用优化配置影响土地利用和覆被类型以及土地利用方式和管理措施,以达到农业面源污染的有效控制。鉴于此,以王家沟小流域为研究区,对现有土地利用进行了系统分析,探讨通过土地利用的优化,在宏观层面上实现农业面源污染控制的最佳途径。研究结果表明：(1)从数量结构来看,王家沟小流域耕地、未利用地和农村居民点处于减少状态,其中耕地减少幅度最大,尤其是旱地；园地、林地、交通运输用地、水域及水利设施用地处于增加状态,其中林地和园地增加最多,约束年两者面积达到55.36%；(2)以水质保护为目标,利用耗费表面模型,结合景观格局特征以及生态系统服务功能价值等分析方法,提出景观格局优化方案,构建了生态上较为安全的格局优化途径。(5)三峡库区小流域农业面源污染关键源区识别农业面源磷污染是水体富营养化和和水质恶化的重要原因,而对农业面源磷流失的关键源区进行有效识别是农业面源污染控制和管理的重要内容和重要组成部分。以位于王家沟小流域为研究区,在GIS支持下,采用改进的磷指数法开展农业面源污染磷流失关键源区识别。研究结果表明：该小流域中关键源区(即磷流失危险性极高和较高的区域)占到整个流域面积的44.9%,危险性中等的地区占到45.6%,危险性低的地区仅仅占到9.5%；其中具有高和中等危险性的区域主要分布在水系周边地区和坡耕地上,这些区域应作为下一步农业面源磷污染的重点控制地区,并根据其不同形成原因采取适当的控制措施。该研究成果成果能为该小流域进一步开展农业面源污染控制和管理并将其在空间上进行有效集成提供依据,同时也为其他流域进行农业面源污染控制和管理提供借鉴。(6)三峡库区小流域农业面源污染控制的最佳管理措施研究仅仅通过不同土地利用类型(地块)之间的优化配置来实现控制农业面源污染还不够,还需要对已确定被控制的关键源区或敏感土地利用类型(地块)实施相应的控制措施。鉴于此,以王家沟小流域为例,根据该小流域农业面源污染特征,并结合土地利用状况、地形地貌、降雨特征等条件,设计了一套融农村居民点—旱坡地—水田—消落带于一体的多重拦截与消纳农业面源污染物的农业面源污染控制系列化最佳管理措施(BMPs),并对其中部分BMPs运行效果进行了评价。研究结果表明：(1)保护性农业技术措施秸秆覆盖能有效减少旱坡地泥沙流失,却增加了径流中氮、磷流失量,且具有较强的时效性；金银花植物篱技术在常年都具有较好的保水保土和防治氮磷流失功能；(2)坡耕地PAM优化利用技术可使泥沙流失量减少80%-90%,氮、磷流失量分别减少20%-30%和25%-35%：(3)水稻田以及垄作拦截和消纳技术一周左右就可以有效地控制污水中的无机态氮和外源污水中的磷；(4)针对分散型畜禽粪便污染而设计的沼气化农业生态循环利用技术,其治污效果和经济效益都较好；(5)消落带芦苇植被拦截带可以有效地吸收和截留氮和磷流失,其中对总氮流失的控制效果最好为30.00%,总磷最好为65.00%。本研究所设计的系列化BMPs对王家沟小流域农业面源污染中N、P和泥沙等污染物的综合去除率达到89%以上。该研究结果可以推广应用到三峡库区其它小流域以控制和管理农业面源污染。更多还原

【Abstract】 In recent years, as water environment pollution problem becomes more and more serious and point sources(PS) pollution control level increases, the non-point source(NPS) pollution has gradually become a major pollution source of water pollution and the key deciding whether the water environmental problem could be solved effectively. Meanwhile, among which the agricultural NPS pollution caused by farmers’ agricultural production and rural living has been recognized to the main source of water pollution, which covers wider range with greater uncertainty and is more difficult to calculate simulate, control and manage. NPS pollution is a landscape-scale phenomenon with various origins, including agriculture, silviculture, mining, and construction, etc. It is driven by multiple factors and includes diffuse pollution which is exclusively a result of human land abuse and land use changes. Generation, transport, and transformation of NPS pollution is closely related to human activities and natural factors. And among them, land use is one of the most important affecting drivers that determine the generation and transport of NPS pollution. Land abuse is one of the most direct forms of human activities, while irrational land-use activities and management mode will lead to soil erosion and nutrient loss with surface runoff, therefore, the large area of NPS pollution to watershed is formed. Meanwhile, small watershed is the headwaters of the water bodies, such as reservoires, rivers and lakes. Its soil erosion can lead to siltation in the river channel, and its soil nutrition loss caused by surface runoff and sediment can make water quality impairment and even eutrophication. All these become one of the main sources of NPS pollution, therefore, it has a significance to control and manage the generation and transport of NPS pollutants. Considering this, it is important to build best management practices(BMPs) based on rational land use through examining the effect of land use on NPS pollution systematically and analyzing the relationship between NPS pollutants and land use in a watershed comprehensively.The Three-Gorges Project(TGP) is one of the largest hydropower projects in the world, which has attracted worldwide attention for its potential influences on the ecological environment. It is ranked as a key project for the improvement and development of the Yangtze River, which has formed a gigantic multi-operation business pattern for flood prevention, power generation, navigation, etc. However, as water levels were driven up, current velocity and diffusivity were dramatically reduced, and the retention time of pollutants was prolonged after the water was cut off. Thus, the TGP also had a profound impact on the environment, such as non-point source pollution. With the completion and operation of the TGP, the influence of it exerting on the ecological environment gradually emerges. The Three-gorge Reservoir areas(TGRA) which is affected greatly by the TGP, because of the special ecological environment and the immigration pressures, and unreasonable human land use activities, the agricultural NPS pollution becomes more and more serious and is seriously restricting sustainable development of agricultural economy and rural environment. And from the point of view of the generation, transport, and transformation mechanism on NPS pollution, it mainly depends on land use/land cover change model. Therefore, it is urgent to strengthen research on the control of NPS pollution, especially studying NPS pollution based on different land use pattern and putting forward land use optimization management mode and measures for controlling NPS have an important theory value and practical significance in protecting water quality.Taking account into the generation and, on the basis of hypotheses, Wangjiagou watershed in the core zone of the TGRA has been selected as a study site. A large number of basic data were collected through the extensive on-site investigation, and through integrated technique means of field monitoring, location experiment and geographic information system(GIS), this study discusses the relationship between watershed land use and the NPS pollution. By establishing basin optimization model of harmonization between environment and economy, this study discusses the best management pattern of land use. Accordingly, this study put forward the theoretical assumption which including an control idea and a control paradigm, the former is land optimization(planning) control in the whole and the latter is BMPs control based on rational land use in the part. To be specific, a paradigm for intercepting and controlling NPS pollution which using the rural residential area-slopping land-paddy field ecosystem-hydro-fluctuation belt system to intercept and reduce NPS pollutants.The main content and result achievements are as follows:(1) The foundation database of Wangjiagou watershed in the Three Gorges Reservoir area NPS pollution research is establishedAccording to research needs, this part carried out a comprehensive investigation and analysis on natural environment and socioeconomic situation of Wangjiagou watershed, and combining on-site investigation, using the GIS software and so on as platform, to establish DEM. And land use type map is acquired from topographic map investigation.The soil type map is acquired by digitizing the Wangjiagou watershed 1:1000 soil type map. Consequently, the foundation databases for the NPS pollution research.are provided.(2) Spatial variability of soil nutrients and its response to land use pattern in small watershed of the Three Gorges Reservoir areaThe geostatistics combined with GIS method was used to analyze and determine spatial variability of surface soil nutrients(0-20cm) which included pH, soil organic matter(SOM), total nitrogen(TN), total phosphorus(TP), total K(TK), available nitrogen(AN), available phosphorus(AP), available K(AK) in Wangjiagou watershed of the TGRA. The results showed that:(1) From the view of soil nutrients statistic characteristics, The soils were widely deficient of OM, and the content of soil AN was relatively higher; The variation coefficients of soil nutrients were graded as AP>AK>TP>OM>AN>TP>pH>TK, and all these presented moderate spatial dependence; the semivariograms of pH, TP and AK in topsoil were best described by spherical model, that of soil SOM, TN and AP submitted exponential model, and those of TK and AN submitter linear model; soil pH have intense spatial self-correlation, and the spatial variability was determined mostly by structural factors, such as parent material, soil type, climate and water conditions, and other soil nutrients have moderate spatial self-correlation, and the spatial variability was determined mostly by random factors, such as crop type, fertilization level and land use management measures. (2)pH tended to increase gradually from southeast to northwest, and most areas in this watershed presented acidity and subacidity; the highest OM content was found in the southeast of this watershed and other areas decrease gradually from center to around; TN decrease gradually from center to around; the highest TP content was found in the northeast, northwest and central areas with shifts eastward, and other areas increase gradually from center to around; TK presented crushing characteristics and had the highest content in the northwest and southeast; AN tended to increase gradually from northeast and southeast to south; the highest AP content was found in the northwest and southeast, and other areas had no significantly variation; AK tended to decrease gradually from the center to northeast and southwest, and in most areas maintained high level. (3) Soil nutrients were significantly affected by different land use types and their spatial positions. Higher values of pH, TP and TK were found in garden land, and its SOM, AN and AK lower than other land use types; higher values of SOM, TN and AN from upland, and AP lower than other land use type; forest land had higher values of AK, but it also had lower values of pH、TN、TP and TK; higher values of AP was found in paddy field, and meanwhile its other soil nutrients maintained intermediate position.(3) Temporal and spatial variation of non-point nitrogen pollution and its response to land use pattern in small watershed of the Three Gorges Reservoir areaSurface water nitrate contamination has aroused nationwide concern recently. In order to reveal temporal and spatial variation of non-point nitrogen pollution, this part take Wangjiagou watershed as an example, based on the data from investigation and monitor from September,2008 to November,2009 under natural rainfall condition in this watershed, temporal and spatial variation characteristics of different forms of nitrogen concentrations were studied. The results showed that:(1) Nitrate contamination in this watershed has been very seriously, and the maximum concentration of N was 45.27mg/l which far exceeds the "V" standard of surface water quality, and this was related to typical agricultural farming area; (2) From the point of spatial scale, the variation rule of average nitrogen concentrations was, well>ditch>pond, and was associated with different land use management practices around the water bodies; (3) From the point of seasonal variation, top nitrogen producer concentrations and load was autumn which in the drizzle but which summer which have sufficient rainwater; there is the power regression relation between nitrogen export load and runoff amount, and maximum export load happened at November and October, and the highest TN export load could reach to 1233kg; (4)And the nitrogen output form was mainly dissolved nitrogen, but in some month was particles nitrogen, Rainfall and human land use activity are important factors for influencing the nitrogen export.(4) Land use pattern optimization analysis in small watershed of the Three Gorges Reservoir areaNPS pollution is a landscape-scale phenomenon with various origins, and they are driven by multiple factors and includes diffuse pollution which is exclusively a result of human land abuse and land use changes. That is, there is a strong relationship between different land use and NPS pollutants. Therefore, the mitigation of NPS pollution should be fully considered rational land use and scientific land management practices. Considering this, this part uses Wangjiagou watershed as investigation demonstrate-on,on the base of analysis on the present status of land use, studies the configuration and quantity characteristics of land use and the problems in existence of land use, and puts forward a land-use patterns optimization approach for controlling agricultural NPS pollution in the macroscopic scale. The results showed that:(1) The cultivated land, unused land and rural resident land will reduce and other land types will be increase, and the rates of forest land and garden land could reach to 55.36%; (2) In order to maintain ecological balance and protect water quality in this watershed, this paper attempts to construct a landscape functional network based on least-cost modeling and combines with ecosystem services and spatial interactions of landscape types, analyzes the spatial difference of the ecological function in Wangjiagou watershed and further discusses the landscape pattern optimization proposal.(5) Critical sources area identification of agricultural non-point phosphorus loss in small watershed of the Three Gorges Reservoir areaAgricultural nonpoint phosphorus(P) pollution is an important cause of eutrophication and water quality deterioration in many water bodies. Identifying critical sources areas that at high risk for P loss to surface water in watershed and concentrating management efforts on these minimal portions of lands are better measures than implementing general strategies over a broad area. A modified catchment scale phosphorus ranking scheme was developed for agricultural areas in Wangjiagou watershed. The result showed that:highest risk areas, take up about 44.9% of the watershed, and middle risk areas contain 45.6%, and lowest risk areas contain 9.5%, and the highest risk areas mainly spread near the downstream parts of main water systenms to the reservoir and from upland. These areas should be regarded as critical source areas to be treated in priority, and then best management practice(BMPs) should be implemented in a high priority to minimize P loss to sensitive watercourses.(6) Research on BMPs of agricultural non-point sources pollution in small watershed of the Three Gorges Reservoir areaMany researchers advocate BMPs to reduce nutrients(N、P) and sediment loss in agricultural areas. Considering the eco-environment vulnerability around the TGRA, and the generation and transport characteristics of agricultural NPS pollution in the TGRA, and with combining, ameliorating and designing a series of techniques and methods relating to the researches on agricultural NPS pollution control, the paper, adopting the comprehensive control thought of combining source control, process block and terminal regulation, designs a series of BMPs based on the rural residential area-slopping land-paddy field ecosystem-water-level-fluctuating zone to intercept and reduce agricultural non-point pollutants in the study area. The results showed that:(1) agrotechnical measures, such as straw mulching can effectively reduce sediment loss from effectively reduce, but it increased the loss amounts of N and P; (2)PAM optimum utilization technique can reduce loss amounts of sediment by 80%-90%, loss amounts of TN and TP by 20%-30% and 25%-35% separately; (3)Rice paddy field ecosystems could effectively control the inorganic nitrogen in sewage and rural sewage phosphorus within just 1 week; (4)Marsh gas tanks for rural households and dispersed livestock and poultry manure have good control effect on N and P, and have good economy benefits; (5) Riparian reed vegetable buffers of water-level-fluctuating zone can decrease the loss of N and P, and the load of TN reduced by 30.00%, and that of TP by 65.00% at least.This paper is a progress report of an ongoing research project from which the expected final product will be an control idea and a control paradigm which also named an integral technology system to control NPS pollution in the TGRA. And because the research results of this paper is just only the beginning, there still remains much work to be done systematically and comprehensively based on the previous research achievement so as to form an systematic control idea and an integral technology system to control NPS pollution in the TGRA.更多还原