【作者】 许磊；

【导师】 陈英旭； 梁新强；

【作者基本信息】 浙江大学 ， 环境工程， 2010， 博士

【摘要】 农村面源污染是我国水体污染防治的重点,农村水环境安全是保障农村生态环境安全和农村社会、生产协调发展的首要前提。如何有效治理农村面源污染,成为当前加速国家污染防治进程与新农村建设的研究热点。本研究以南太湖地区农村小型浅水湖泊为对象,利用3S技术和数学模型,量化水环境容量与纳污量,提出基于土地调控方式的污染源削减方案；同时研究湖泊水体自净规律及影响因素,评价沉积物和水生植物在湖泊水体自净中的作用。研究结果主要包括：1.建立了一套适用于评估面源污染区小型浅水湖泊水环境容量的操作方法。该方法将3S技术与输出系数模型应用于南太湖地区农村面源污染调控上,并应用卫星遥感图像、水质模型、输出系数模型、VC++程序相结合的方法。研究结果表明：南太湖地区农业面源污染区内小型浅水湖泊的主要污染源为农田排水、农村生活污水和养殖废水。2006年排入四个湖泊的COD、TN、TP量为总环境容量的0.68、0.82、2.34倍,TP需要削减1702.84 kg/a。南太湖区域内土地利用结构对面源污染输出有显著的影响,需集中收集处理农村径流和网箱养殖污水。建立生活污水和生活垃圾的收集／处理装置,减少农村径流的影响,增加植被面积可以达到减少区域污染物输出浓度的效果。2.明晰了南太湖地区农业面源污染区内小型浅水湖泊的自净能力及其影响因子。湖泊对高锰酸盐指数、总氮(TN)、铵(NH4+)、硝酸盐(NO3-)、总磷(TP)、叶绿素a (Chl-a)的净化能力季节性差异较大：春季和冬季自净效果较好,夏季主要污染物为NH4+和NO3-,秋季为TP和Chl-a。湖泊水体TN、TP污染严重,有机污染较轻。氮磷浓度条件适宜藻类生长,水体容易发生富营养化,且磷为藻类生长限制性因子。Chl-a浓度显示湖泊在夏秋两季处于富营养化水平,冬春两季转变为中营养水平。水生植物的种类和数量影响水体pH值和溶解氧(DO)浓度,农田肥料流失和农村生活污水排放造成水体中氮磷含量过高。过量使用尿素使得夏季水体中有机氮占TN的主要部分,其他季节NO3-占TN的主要部分。主成份分析结果表明,影响南太湖地区小型浅水湖泊自净能力的3个主成份分别为浮游植物因子(水温、pH、高锰酸盐指数和Chl-a)、农田排水因子(pH、高锰酸盐指数和TN)和营养因子(TN和TP)。聚类分析结果表明,3个湖泊11个采样点4个季节的水质可聚为两大类,春秋冬季为一类,夏季为一类,说明该地区湖泊水质受季节变化影响明显。利用水温和pH两个水质指标拟合出适用于计算湖泊水体中的高锰酸盐指数、TN、TP、Chl-a的线性方程,提高了现场快速预测能力。3.揭示了南太湖地区湖泊沉积物、水生植物在不同自然条件下的吸附／释放规律。劣Ⅴ类水质条件下,沉积物能较快的吸附PO43-,对NH4+的吸附能力最大。Ⅲ-Ⅴ类水质条件下,沉积物释放NH4+,吸附NO3-和PO43-。有机物有利于沉积物吸附PO43-,不利于吸附NH4+。随着pH值的增加,沉积物释放NH4+和PO43-的能力呈“U”型曲线,pH值过高或过低都会引起沉积物释放NH4+与PO43-。水生植物影响了沉积物磷形态和TOC含量的季节性变化：草控型湖泊和半草控型湖泊沉积物中OP含量冬季高于夏季,两季的主要污染源分别为水生植物残体和污水。非草控型湖泊OP含量夏季高于冬季,主要污染源是生活污水,水体中OP降解性能差。草控型湖泊BAP含量冬季显著高于夏季,半草型湖泊和非草型湖泊两季也有显著不同。黄花水龙适合作为南太湖地区主要的水面植物,并与沉水植物-狐尾藻相搭配,作为主体构建南太湖地区小型浅水湖泊水生生物群落。4.发现湖泊水体的NH4+、NO3-和PO43-含量会在7℃和14℃左右发生突变现象。沉积物系统中,7～14℃时的NO3-浓度比0～7℃时NO3-浓度要显著升高；较高气压下,NO3-浓度变化相对较大；较高湿度下,NH4+、NO3-的浓度变化相对较小。水生植物系统中,温度的升高会引起水体中NO3-和PO43-的浓度升高,NH4+浓度则降低；大气压的升高会引起NH4+和NO3-的浓度升高,PO43-先下降后升高；空气湿度的升高会引起NH4+浓度下降,NO3-和PO43-则先升高后下降。阐明南太湖农业面源污染区小型浅水湖泊水质变化机理并提出相应调控技术,有利于减少流域面源输出,减少太湖水质恶化程度,并为国家面源污染控制体系提供参考方案。更多还原

【Abstract】 Rural non-point source pollutions were the focus of water pollutions control in China. Rural water environment safety impacted the rural ecological environment and rural society/ production coordinated development. How to control non-point source pollution in rural areas effectively has become the research highlight of national pollution control processing. This study focused on the small shallow lakes in South Taihu Lake region to rural non-point source pollution carrier, relying on 3S technology and mathematical models to quantify the water environmental capacity and the quantity of pollutants, proposed pollution reduction program by controlling land-based sources, investigated the rules and influence factors of water self-purification, and estimated the contribution of sediment and aquatic plants in water purification. The main results are summarized as follows.1. A method to estimate water environment capacity of rural non-point pollution source in South Lake Taihu was established.3S technology and the export coefficient model were applied to control the rural non-point pollution of South Taihu Lake. Satellite remote sensing, water quality model, output coefficient model combined with VC++procedures were used to establish a simple and practical program for controlling water environment capacity of small shallow lakes which affected by rural non-point pollution. The results showed that the main source of pollution were farmland drainage, rural sewage and aquaculture waste water in small shallow lakes of South Taihu Lake region which were polluted by agricultural non-point pollution. COD, TN, TP volume dumped in to the four lakes were 0.68,0.82,2.34 times of the total environmental capacity in 2006. TP was need to cut 1702.84 kg/a. Land-use structure has a significant impact on the output of non-point pollution. Collection and disposal needed to focus on cage culture of rural runoff and sewage. The establishment of sewage and garbage collection/processing device could reduce the impact of rural runoff. Increased grassland area can also reduce the concentration of pollutants in the output.2. The self-purification ability of the lake and its influencing factors were distinct. Seasonal differences of self-purification of potassium permanganate index, total nitrogen (TN), ammonium (NH4+), nitrate (NO3-), TP, chlorophyll (Chl-a) in small shallow lakes were remarkable. Effects of self-purification were better in spring and winter, worse in summer by NH4+and NO3- and in autumn by TP and Chl-a. TN and TP pollution were serious in lake and organic pollution was light. Concentrations of TN and TP facilitated algae growth, and lakes were eutrification easily by the limiting factor of phosphorus. Concentrations of Chl-a were showed that the lakes were eutrophic in summer or autumn and mesotrophic in winter or spring. Species and quantity of aquatic plants were the main factors to affect the change of pH and dissolved oxygen (DO), and loss of fertilizer and domestic wastewater was the main reasons for high nitrogen and phosphorus concentrations in lakes. Organic nitrogen was the main portion of TN by using excessive carbamide in summer, and NO3- was the main portion in other seasons. The principal component analysis result showed that the three principal components of self-purification ability were phytoplankton factors (water temperature, pH, potassium permanganate index and Chl-a), farm drainage factors (pH, DO and TN), nutrient factors (TN and TP). The cluster analysis result showed that the water quality of four seasons in 11 sampling sites of three lakes can be divided into two categories:firstly, in spring, autumn and winter; secondly, in summer, which indicated that the water quality of lakes in the region were impacted by seasonal. Water temperature and pH were used to calculate the concentrations of potassium permanganate index, TN, TP, Chl-a by linear equations, which improved the quick prediction ability in locale.3.Method of the adsorption/release of sediment and aquatic plants were investigated in different natural conditions. Sediment could absorb PO43- fast and absorb more NH4+ in bad V category water conditions. Sediment released NH4+ and absorbed NH4+/PO43- in III-V category water conditions. Organic matter facilitated PO43- absorption and inhibited NH4+ absorption of sediment, and released NH4+/PO43- from sediment at extravagant high and low pHs, like U-shaped curve. Water plants impacted the seasonal change of the TOC content and phosphorus fractions in sediment. Domestic sewage and aquatic plant debris contributed the OP content in sediment of macrophytic lake which were higher in winer than in summer. Domestic sewage contributed the OP content in the sediment of semi-macrophytic lake and non-macrophytic lake which were higher in summer than in winter., and the low degradation of OP might cause by low aquatic paints. In the sediment of macrophytic lake, bioavailable phosphorus content was higher in winter than in summer, while there was no obvious variation in semi-macrophytic lake and non-macrophytic lake. Jussiaea repens were suitable for lakes, and made up the aquatic community with Myriophyllum verticillatum.4. Water self-purification of natural small shallow lakes obviously changed in 7℃and 14℃due to release of sediment. In shallow lake sediment system, NO3- concentration significantly increased in 7～14℃than in 0～7℃. NO3- concentration was relatively large in high atmospheric pressure. NH4+ and NO3- concentrations changed relatively small in higher temperature. In aquatic plants system, concentrations of NO3-and PO43- increased by water by temperature increased with NH4+concentrations reduced. Concentrations of NH4+and NO3- increased by atmospheric pressure growth with PO43- concentrations first decreased and then increased. NH4+ concentrations decreased by air humidity increase with NO3-and PO43- first increased and then decreased.So, clarify the water quality controlling mechanism and the corresponding technology of nonpoint source pollution of small shallow lake in South Lake Taihu in favour of reducing watershed pollution output and the deterioration of water quality of Lake Taihu, and providing references to natioanl nonpoint pollution control regime.更多还原