| 题名 | 村镇降雨径流污染与自然沟渠净化机制研究——以紫色丘陵区林山村镇为例 |
| 作者 | 罗专溪 |
| 学位类别 | 博士 |
| 答辩日期 | 2008 |
| 授予单位 | 中国科学院水利部成都山地灾害与环境研究所 |
| 授予地点 | 成都 |
| 导师 | 朱波 |
| 关键词 | 迁移 自净机制 初期冲刷效应 生态优化 面源污染 村镇 |
| 其他题名 | Stormwater runoff pollution and its control mechanism of natural ditch in a rural township |
| 学位专业 | 自然地理学 |
| 中文摘要 | 降雨径流污染是河口、湖泊、水库等水体的重要面源污染源。村镇降雨径流污染特征与控制机理的研究十分匮乏，难以满足新形势下村镇城镇化与水环境保护的可持续发展需要，是当前面源污染研究中的薄弱环节之一。紫色丘陵区处于长江上游生态屏障的最前沿，人口密度大，村镇发展快速，村镇生产、生活废水因缺乏排污管道和处理系统而无序排放、随机堆积，并通过降雨径流输移至下游水体。村镇的污、废水在流域内具有最高的污染负荷，对附近或流域水环境造成很大压力。自然沟渠作为面源污染源与水体之间的缓冲过渡区，能够通过其中的土壤（泥沙）吸附、植物吸收等一系列自然净化机制，截留净化氮磷等面源污染物。但很少有人对自然沟渠的自然净化机制开展系统的研究。因此，研究紫色丘陵区村镇的降雨径流污染特征、污染物在自然沟渠中的迁移特征和净化机理，以及自然沟渠净化能力与影响因素具有明显的区域特色和重要的环境保护意义。本文通过观测紫色丘陵区村镇降雨径流过程中污染物迁移转化特征，分析各种面源污染物在自然沟渠时空变化规律，探讨面源污染物在自然沟渠中与土壤（泥沙）、植物等的相互作用机制，研究自然沟渠对面源污染物的净化能力与影响因素，查明紫色丘陵区村镇降雨径流污染过程特征，初步阐明土壤（泥沙）截控固持、跌落曝氧、植物吸收等自然净化机理与作用机制，基本掌握自然沟渠对面源污染物的净化能力与影响因素，为优化设计控制村镇高负荷面源污染的自然沟渠，构建生态沟渠奠定科学基础，以促进村镇可持续发展与受纳水体（尤以重点水域为甚）水环境保护，推进社会主义和谐新农村的建设。研究获得以下重要结果与结论：（1） 村镇降雨径流污染特征村镇降雨径流TN、TP、COD与SS的事件平均浓度EMCs（Event Mean Concentrations）均值分别为21.31、3.00、536、1941 mg L-1，年污染负荷分别为47.17、6.64、1186、4297 kg ha-1。溶解态氮、颗粒态磷分别是村镇径流污染氮磷素输出的主要形态。村镇降雨径流的污染物峰值都发生在径流峰值之前，二者间隔时间为3~47min。TN、TP、COD、SS的EMCs和FF30（由占总径流量30%的初期径流所运移的负荷）之间存在显著的负相关关系(P<0.05, n=12)，表明初期径流运移的负荷较大，有将近40%的污染负荷为占总径流量30%的初期径流所运移。村镇降雨径流污染普遍存在中等初期冲刷效应。（2） 降雨径流污染在自然沟渠的迁移转化特征 NO3--N浓度在空间沿程上呈先减后增而再减的趋势，其他降雨径流污染物呈现空间沿程的递减趋势。溶解态氮是降雨径流氮素在空间沿程上的主要迁移形态，溶解态磷是流量限制型事件降雨径流磷素空间沿程的主要迁移形态，而颗粒态磷是物质限制型事件降雨径流磷素空间沿程的主要迁移形态。颗粒态氮是氮素初期径流的主要迁移形态，而后期径流的主要迁移形态是溶解态氮。溶解态磷、颗粒态磷分别是磷素在流量限制型事件、物质限制型事件整个径流过程的主要迁移形态。降雨径流氮和物质限制型事件的COD与SS在自然沟渠迁移过程中，有随径流时间增加而急剧递减的变异规律，而降雨径流磷和流量限制型事件的COD与SS随径流时间的增加而呈平稳下降趋势。（3） 自然沟渠对降雨径流污染净化的作用机制土壤（泥沙）截控固持是自然沟渠控制降雨径流污染最重要的作用机制，有效降低径流中颗粒物浓度和拦截泥沙是自然沟渠控制降雨径流污染的关键。自然沟渠通过泥沙截控、存储以及泥沙本身的吸附性能等对污染物的截控固持作用，可去除氮磷平均分别为144.51、65.20 g m-2（降雨量平均为37.85mm），最大可去除氮磷分别为165.73、73.43 g m-2（降雨量为111.7mm），植被段土壤约可吸附去除氮磷分别为14.11、9.45 g m-2。植物吸收是植被段氮磷去除的重要作用机制，在雨季（4~9月）共吸收氮磷分别可达82.69、12.52 g m-2。跌落曝氧也是降雨径流污染控制的重要作用机制。跌落段对NH4+-N的场均去除负荷为15.05 g m-2，对COD的场均去除负荷为0.84 kg m-2。跌落段的硝化能力偏低，而COD净化能力较高。（4） 自然沟渠对降雨径流污染的净化能力与影响因素自然沟渠对降雨径流污染的场均去除率较高，分别达到64.52%（TN）、78.11%（TP）、74.31%（COD）和79.50%（SS），最小去除率分别仅为44.63%（TN）、37.90%（TP）、52.92%（COD）和45.66%（SS）。自然沟渠净化能力缺乏稳定性。村镇降雨径流TN、TP场均去除负荷较低，分别为14.06、2.30 g m-2，COD和SS场均去除负荷较高，分别达2706、5809 g m-2。TN、TP、COD、SS在自然沟渠全年去除负荷分别为0.85、0.13、38.43、89.54 kg m-2。径流系数、径流时间是自然沟渠净化降雨径流污染的主要控制因素。自然沟渠径流系数越大，径流时间越长，径流污染物去除率越低，径流污染物净化反应速率也越低。村镇降雨径流初期冲刷效应越强，氮磷污染物净化速率越快。受初期径流冲刷效应影响，自然沟渠在短时间内不能很好的净化降雨径流氮和物质限制型事件的COD、SS。沟渠土壤解吸系数和解吸率较大，要及时清除自然沟渠沉降段、沉沙凼截控的泥沙，加强植被段植物对土壤养分的吸收利用，防止二次污染。延长污染物在自然沟渠的水力停留时间，改善自然沟渠土壤矿物组成类型而提高其吸附性能，增加复合介质渗滤系统处理分流的初期污染径流是提高自然沟渠净化能力的有效途径。 |
| 英文摘要 | Stormwater runoff from urban areas including suburbs and rural townships is identified as one of the leading sources of water quality impairment in surface waters. Lack researches on characteristics and control mechanisms of stormwater runoff in rural townships make it almost impossible to effectively protect water environment nearby. It is therefore hard to meet the criteria of sustainable development for protection of water environment and urbanization of rural townships. Purple soils are widely distributed in the hilly area along the Yangtze River with land area of 300,000 km2, and concentrated in the Sichuan Basin and the core of Three Goreges Reservoir, China. The rapid urbanization in rural townships in hilly area of purple soils inevitably introduces high-load stormwater runoff pollution in their watershed scales. Lack drainage pipeline network in these rural townships makes it almost impossible to effectively centralize treatment of polluted water. Commonly, sewage and slaughter wastewater are not intercepted for treatment, but directly discharge into the environment. Although the amount of the wastewater is smaller, the concentrations of pollutants are often higher. Most of them accumulate in drainage ditches in dry days due to little runoff. When rain events occur, stormwater runoff from rural townships can carry non-point source pollutants along with the pollutants accumulated in drainage ditches. As a result, the runoff mixes with large variety of pollutants from point and non-point sources in the form high load in a short time, posing a greatly threat to the water environment nearby. As one of buffer corridors between non-point sources pollution and water bodies, natural ditch can retain and purify some pollutants such as nitrogen, phosphorus, etc. through several self-purified mechanisms including soil adsorption, vegetation assimilation, and biodegradation. It is therefore regional significance of environmental protection for the researches on characteristics of stormwater runoff pollution, pollutants movement and its purified mechanisms across natural ditch, and technical optimization for retention and purification of natural ditch in rural townships in purple soils. The main objectives of the thesis were ① to characterize stormwater runoff pollution process, transport forms and load of pollutantns, ② to examine pollutants transport and its control mechanisms of stormwater runoff in natural ditch, ③ to investigate removal effects and its influenced factors of stormwater runoff, then to provide insight into technical optimization of natural ditch for stormwater runoff pollution control. Primary results were as follows. (1) Characteristics of stormwater runoff pollution The average EMCs (Event mean concentrations) values of TN (Total nitrogen), TP (Total phosphorus), COD (Chemical oxygen demand), and SS (suspended soilds) for 12 rain events in Linshan were 21.31, 3.00, 536, 1941 mg L-1, respectively. The annual pollutant loads for TN, TP, COD and SS were 47.17, 6.64, 1186 and 4297 kg ha-1, respectively. PP (Particulate phosphorus) and DN (Dissolved nitrogen) were the main forms of nitrogen and phosphorus in stormwater runoff. The intervals between the peak of pollutant concentration and the peak of flow rate ranged 3 – 47 min for the selected 12 rain events. There were significant negative correlations between the EMCs and the FF30 for TN, TP, COD and SS (P<0.05, n=12), indicating that the transport load by first flush runoff was pertinent greater. In fact, near 40% of the masses of TN, TP, COD and SS were transported by the first 30% of the total flow volume, supporting that medium first flush effects were common for the stormwater runoff pollutants in Linshan Township. The FF30 (FF, First flush) values of TN, TP, COD and SS were positively correlated to the maximum rainfall intensity (P<0.05, n=12), and that of TP was also positively correlated to the average rainfall intensity (P<0.05, n=12). The EMCs of TN, TP, DN and PP were negatively correlated to the maximum rainfall intensity, total flow volume, duration and runoff duration (P<0.05, n=12). (2) Transport of stormwater runoff pollution across natural ditch Concentrations for NO3--N tended to decrease first before increase, then decrease with increasing distance downstream, while Concentrations for other pollutants reduced with increasing distance downstream, including TN, PN, NH4+-N, TP, PP, PO43--P and COD, as well as SS. DN was primary transport form for nitrogen with increasing distance downstream. DP (Dissolved phosphorus) was primary transport form for phosphorus with increasing distance downstream under Flow-limited events, while PP was that under Mass-limited events. PP was the primary transport form for nitrogen during the first flush runoff, while DN was that under the latter runoff. DP (Dissolved phosphorus) was primary transport form for phosphorus during the process of runoff under Flow-limited events, while PP was that under Mass-limited events. The sharp decrease with increasing runoff duration appeared for nitrogen, COD and SS under Mass-limited events, while the gentle decrease appeared for phosphorus, and COD and SS under Flow-limited events. (3) Control mechanisms of stormwater runoff pollution in natural ditch Sediment retention and immobilization (SRI) was the most important mechanism for stormwater runoff pollution control in natural ditch. The key to control stormwater runoff pollution was effective to reduce the concentrations for particulate masses and to retain sediment with larger size. The averages for nitrogen and phosphorus removal were 144.51, 65.20 g m-2 with the average of 37.85 mm for precipitation by means of sediment retention and immobilization in GS (Grit removal segment) and GT (Grit removal tank), while the maximum were 165.73, 73.43 g m-2 with the average of 111.7 mm for precipitation. The removal nitrogen and phosphorus by soil adsorption were approximately 14.11, 9.45 g m-2. Vegetation assimilation was other pivotal mechanism for stormwater runoff pollution control by means of physical retention, oxidation and deoxidation, microorganism biodegradation, etc. In natural segment (NS), Alternanthera philoxeroides (Mart•) assimilated nitrogen and phosphorus with 15.05, 2.06 g m-2 during rainy season (Apr. ~ Sep.), while the roots of Polygonum hydropiper L., with 6.97, 1.31 g m-2, and leafs and stems with 60.67, 9.15 g m-2. The total assimilated nitrogen and phosphorus were 82.69, 12.52 g m-2 during rainy season in natural ditch. Falling aeration was another pivotal mechanism to control stormwater runoff pollution. The nitration ability of Falling segment was somewhat lower since the average of removal load for NH4+-N was 15.05 g m-2, while the purified ability for COD was pertinent higher since the averages of removal load for COD was 0.84 kg m-2. (4) Removal effects of stormwater runoff pollution control and influenced factors in natural ditch. The removal ratios of natural ditch were pertinent low with 64.52% for TN, 78.11% for TP, 74.31% for COD and 79.50% for SS. Removal effects of natural ditch for stormwater runoff pollution control were not enough with stability, since the minimum of removal ratios were somewhat lower with 44.63% for TN, 37.90% for TP, 52.92% for COD and 45.66% for SS. The averages of removal loads for TN and TP were lower with 14.06, 2.30 g m-2, while that for COD and SS were greater with 2706, 5809 g m-2. And the annual removal loads for TN, TP, COD and SS were 0.85, 0.13, 38.43, 89.54 kg m-2 by means of the retention and purification in natural ditch. Runoff coefficient and runoff duration were the two key factors to influence the removal effects of natural ditch. If the greater values were for runoff coefficient and runoff duration, the lower values were for removal ratio and the lower purified reactive rate. Similarly, the more intensive values for first flush effects, the greater values for purified reactive rate. Affected by the first flush effects, the removal concentrations for nitrogen, COD and SS under Mass-limited events were somewhat lower, particularly during the first period of runoff. Secondary pollution needs to control through removing sediment in GS and GT, and strengthening the assimilation of vegetation since the higher values for desorption coefficient of soils in natural ditch. The improvement for pollutants removal by natural ditch can achieve by means of longer reactive time, perfecting mineral forms in soils, and adding complex medium infiltration tank to treat separated first flush runoff. |
| 语种 | 中文 |
| 学科主题 | 土壤学 |
| 公开日期 | 2010-10-14 |
| 分类号 | TU9;TU2 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.imde.ac.cn/handle/131551/2196]  |
| 专题 | 成都山地灾害与环境研究所_成都山地所知识仓储（2009年以前） |
| 推荐引用方式 GB/T 7714 | 罗专溪. 村镇降雨径流污染与自然沟渠净化机制研究——以紫色丘陵区林山村镇为例[D]. 成都. 中国科学院水利部成都山地灾害与环境研究所. 2008. |
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