【作者】 陈莹；

【导师】 赵剑强；

【作者基本信息】 长安大学 ， 交通环境与安全技术， 2011， 博士

【摘要】 随着城市化进程的加快和点源污染逐步得到有效控制,作为除生活污水和工业废水之外的第二大城市水污染源,城市地表径流逐渐成为城市水环境质量恶化的主要原因。路面径流作为城市地表径流中污染效应最强的部分,对受纳水体的影响十分严重。近年来,关于路面径流的研究成为环境科学、水文学、道路生态学、自然地理学等学科领域交叉研究的热点。本论文在对路面径流污染国内外研究现状、存在问题、污染控制必要性进行简要分析的基础上,在西安市城市主干道南二环路建立路面径流原位采样站,利用自制流量等比例采样装置,对2009年3月-2010年11月的多场径流进行采样测试,就西安市路面径流污染特征、污染负荷、排污规律及污染控制技术展开研究。西安市路面径流污染特征的研究结果表明：①西安市路面径流污染物事件平均浓度(Event Mean Concentration, EMC)变异大且污染严重,SS、COD、溶解性COD、NH3-N、Pb、Zn和溶解性Zn的EMC中值分别为1601mg/L、613mg/L、143mg/L、1.9mg/L、0.042mg/L、0.223mg/L和0.111mg/L, SS、COD的EMC中值远大于《污水综合排放标准》三级标准,是径流的主要污染物。②路面径流中Pb主要以颗粒态存在,46.2%的Zn和26.4%的COD呈溶解态。③颗粒物是许多其他污染物的载体,COD、Pb、Zn均与SS在显著性水平0.01时显著相关,相关系数分别为0.797、0.825和0.893。④表征降雨特征的各因子中,降雨量、最大降雨强度与污染物浓度呈负相关,降雨历时与除NH3-N之外的其他污染物呈负相关,相关性依次为降雨量>最大降雨强度>降雨历时,前期晴天时间与溶解性Zn和溶解性COD浓度正相关,但与其它指标不相关。⑤SS、COD及NH3-N等与大气降尘有关的污染物浓度随季节明显变化,而与交通排污有关的溶解态COD、重金属Pb、Zn和溶解态Zn的浓度季节差异不大。西安市路面径流次污染负荷的研究结果表明：①西安市路面径流SS、COD、溶解性COD、NH3-N、Pb、Zn和溶解性Zn的次污染负荷分别为4.56-778.39kg/hm2、2.22-308.7kg/hm2、0.76-52.33kg/hm2、0.01-1.39kg/hm2、0.05-33.09g/hm2、1.38-115.82g/hm2和0.27-86.12g/hm2,不同场次径流事件携带入受纳水体的污染物量差异大,对受纳水体造成冲击影响。②表征降雨特征的各因子中,降雨量与次污染负荷呈显著正相关,在显著性水平0.01时相关系数为0.734-0.943,最大降雨强度和降雨历时也与次污染负荷显著正相关,前期晴天时间与次污染负荷不相关。③利用多元回归方法建立了路面径流次污染负荷与降雨量、降雨历时、最大降雨强度、季节累积降雨量等影响因素的数学模型,所建立的数学模型可通过显著性检验,可用于对路面径流次污染负荷的预测。西安市路面径流年污染负荷及采样次数对年污染负荷估算准确性影响的研究结果表明：①西安市路面径流SS、COD、溶解态COD、NH3-N、Pb、Zn和溶解态Zn的年污染负荷分别为11090.29kg/(hm2.a)、3462.5kg/(hm2.a)、812.48kg/(hm2.a)、13.49kg/(hm2.a)、0.28kg/(hm2.a)、1.35kg/(hm2.a)和0.59kg/(hm2.a),具有较大的污染潜力。②由于EMC的宽幅变异性,当实测径流场次较少时,其EMC平均值不能准确表征路面径流污染的统计特征,用其代表地点平均浓度(Site Mean Concentration, SMC)计算年污染负荷误差较大。③随机抽样研究结果表明,当采样场次大于16场时,路面径流各污染指标随机抽样样本EMC均值与SMC的最大相对误差均小于30%,也即,若能保证至少实测16场径流,以其EMC平均值作为SMC计算的径流年污染负荷的最大相对误差在30%以内。西安市路面径流初期冲刷效应的研究结果表明：①径流过程污染物浓度变化规律与其赋存状态有关,SS、COD、Pb等以颗粒态为主的污染物的浓度随雨强变化剧烈波动；NH3-N、溶解态COD、溶解态Zn等以溶解态为主的污染物浓度受雨强影响较小,随径流过程逐渐下降。②西安市路面径流污染严重,降雨数小时后的末期径流中SS和COD分别为358-422mg/L和179-367mg/L,末期径流仍具有较高的污染水平。③路面径流初期冲刷现象并非普遍存在,与污染物的赋存状态和场次降雨特征密切相关。溶解态污染物易于出现初期冲刷现象,颗粒态污染物是否出现初期冲刷与场次降雨特征有关。④测试的3场径流事件初期30%的径流携带的SS、COD、溶解性COD、NH3-N、Pb、Zn和溶解性Zn的负荷占场次径流总负荷的比例分别为21.8%-50.0%、25.5%-49.3%、36.3%-52.6%、52.6%-66.7%、26.8%-45.0%、27.2%-63.4%和36.2%-62.6%,表明仅对初期径流进行治理无法实现对西安市路面径流污染的有效控制。西安市路面径流污染控制技术的研究结果表明：①西安市径流污染需从非工程管理措施和工程技术措施角度、从污染物产前、产中和产后多个层面、从污染物源头消减、输移途径控制和终端治理多个环节开展系统治理。②沉淀可有效去除径流中的颗粒物,沉淀60min和2h,SS的平均去除率为60.2%和72.5%；不同场次径流达到相同的颗粒物沉降去除率其表面负荷变化大,要达到45%、60%和80%的沉淀去除率,表面负荷分别为1.1-9.3cm/min、0.6-5.9cm/min和0.1-2.7cm/main,沉淀去除率每提高10%,对应的表面负荷减少1.3-3倍。③不同场次径流中颗粒物粒径分布呈宽幅变化,d10、d50、d90分别为3-23μm、17-56μm和40-65μm,表明径流中颗粒物以细颗粒为主,应对3-65μm粒径颗粒的污染效应及迁移转化规律予以关注。④若需保证在5年一遇的暴雨流量下截污网袋不发生溢流,由130g/m2、150g/m2和300g/m2土工布制作的截污网袋需至少保证75mm、94mm、175mm的有效过滤高度,网袋对SS的平均去除率分别为56.0%、69.4%和76.5%。更多还原

【Abstract】 With the accelerated urbanization process and effective control of point source pollution, urban runoff, as the second pollution source for urban water environment besides domestic sewage and industrial wastewater, has become the main reason for deterioration of water quality. Road runoff, as the strongest polluted part of urban runoff, affects the quality of receiving waterbodies with special severity. In recent years, research about road runoff has developed into an independent field and become multidisciplinary scientific field of environmental science, hydrology, road ecology, physical geography and other disciplines.Based on analysis of road runoff research status, existing problems and necessity of pollution control, a sampling station, which was equiped with a self-made volume proportional collecting device, was built at south second ring road in Xi’an city. Road runoff caused by rainfall events were sampled from Mar.2009to Nov.2010. Pollution characteristics, pollution load, first flush effect and pollution control technology of urban road runoff in Xi’an city were studied in the dissertation.Study on pollution characteristics of urban road runoff in Xi’an city showed that:(1) EMC of main runoff pollutants varied greatly and the median EMC of SS, COD, dissolved COD, NH3-N, Pb, Zn and dissolved Zn were1601mg/L,613mg/L,143mg/L,1.9mg/L,0.042mg/L,0.223mg/L and0.111mg/L respectively. The coefficient of variation ranged from0.47to0.8. EMCs of SS and COD were far greater than the values of Integrated Wastewater Discharge Standard Grade III, so SS and COD were the main pollutants of road runoff.(2) The occurrence of Pb was mainly granular state and46.2%of Zn,26.4%of organic pollutants was dissolved.(3) The correlation of COD, Pb and Zn with SS were significant at0.01level and the correlation coefficients were0.797,0.825and0.893respectively, which showed that particulate matters were carrier for many other pollutants.(4) The descending order for influence weights of rainfall characteristics on pollutants’concentration was as follows: rainfall volume> maximum rainfall intensity> rainfall duration. Antecedent dry period (ADP) had no correlation with EMC of many pollutants except dissolved Zn and dissolved COD.(5) Result of one factor analysis of variance showed that EMC of SS, COD and NH3-N varied with seasons significantly, while the variation tendency of other pollutants, such as dissolved COD, Pb and Zn was not obvious.Study on pollution loads of urban road runoff in Xi’an city showed that:(1) The pollution load of SS, COD, dissolved COD, NH3-N, Pb, Zn and dissolved Zn were4.56-778.39kg/hm2,2.22-308.7kg/hm2,0.76-52.33kg/hm2,0.01-1.39kg/hm2,0.05-33.09g/hm2,1.38-115.82g/hm2and0.27-86.12g/hm2respectively. The amount of pollutants entering into the receiving waters carried by road runoff in different runoff events were quite different and caused shock effect on receiving water bodies.(2) Rainfall had most significant impact on pollution load positively and the correlation coefficients were0.734-0.943at the significant level of0.01. Maximum rain intensity and rain duration were also positively correlated with pollution loads, while ADP had few relationship with it.(3) The established multiple regression models of runoff pollution loads with rainfall, maximum rain intensity, rain duration and cumulative seasonal rainfall passed the model significant test unanimously and can be used for forecast of road runoff pollution load.Annual pollution loads of urban road runoff in Xi’an city were calculated. In addition, impact of sampling size on estimation accuracy of annual pollution load was investigated. The results were as follows:(1) The annual pollution load of SS, COD, dissolved COD, NH3-N, Pb, Zn and dissolved Zn were11090.29kg/(hm2.a),3462.5kg/(hm2.a),812.48kg/(hm2.a),13.49kg/(hm2.a),0.28kg/(hm2.a),1.35kg/(hm2.a) and0.59kg/(hm2.a) respectively, which indicated that urban road runoff in Xi’an city had a rather high polution potential.(2) The pollution loads of urban road runoff in Xi’an city were quite different between various rainfall events as EMC of road runoff varied widely. The mean EMC can not represent the statistical characteristics of road runoff pollution accurately when the sampling size is not big enough. The error of calculated annual pollution load would be quite big if SMC is represented by the mean EMC of the small sample.(3) Results of random sampling showed that when sampling size is more than16, the maximum relative error between SMC with mean EMC is below30%. That is to say, if at least16runoff events are sampled and monitored, the mean EMC of those runoff events can represent SMC with rather high accuracy and the maximum relative error of calculated annual pollution load is below30%.Study on first flush effect of urban road runoff in Xi’an city showed that:(1) The rule of runoff concentration variation was related with the mode of occurrence of pollutants. The concentrations of granular state pollutants, such as SS, COD and Pb, were mainly influenced by rainfall intensity during runoff process, while concentrations of soluble pollutants, such as NH3-N, dissolved COD, dissolved Zn, were gradually reduced during runoff process and were not influenced by rainfall intensity seriously.(2) Urban road runoff in Xi’an city was seriously polluted and the final part runoff after hours’rainfall still had a high pollution level. SS remained as high as358-422mg/L, which was close to or above the value of Integrated Wastewater Discharge Standard Grade Ⅲ. COD remained as high as179-367mg/L, which exceeded the value of Integrated Wastewater Discharge Standard Grade II.(3) First flush phenomena of road runoff were not common, which was influenced by the mode of occurrence of pollutants and rainfall characteristics. Dissolved contaminants in runoff were prone to first flush phenomena, while first flush effect of granular state pollutants were seriously influenced by rainfall characteristics.(4) The load ratios of SS, COD, dissolved COD, NH3-N, Pb, Zn, and dissolved Zn of initial30%runoff volume to that of total runoff volume were21.8%-50.0%,25.5%-49.3%,36.3%-52.6%,52.6%-66.7%,26.8%-45.0%,27.2%-63.4%and36.2%-62.6%, respectively, which indicated that only initial runoff treatment will not successful pollution control of urban road runoff in Xi’an city be finally realized.Study on pollution control technology of urban road runoff in Xi’an city showed that:(1) Road runoff pollution in Xi’an city should be controled successfully through the combination of non-engineering measures and engineering measures. The minimization of contamination was suggested from the full process of discharges of contaminants in the runoff.(2) Sedimentation was an effective method to remove particles in runoff. The average removal efficiency of SS was60.2%of60minutes’settling and72.5%of2hours. The surface loads achieving same removal efficiency of different runoff events varied greatly. In order to achieving removal efficiency of45%、60%and80%, the surface loads of sedimentation tank were1.1-9.3cm/min,0.6-5.9cm/min and0.1-2.7cm/min respectively. The surface load decreased1.3-3times as the required particle settling removal efficiency increased10%.(3) The particle size distribution of road runoff varied greatly with regions and rainfall events. The dio, dso and d90of road runoffs in Xi’an city were3-23μm,17-56μm and40-65μm respectively. It’s obvious that most of the particles in runoff were fine particles and we should pay more attention to the pollution intensity and moving and changing rules of fine particles with the diameter of3-65μm.(4) The effective filter height of interception bag made by geotextile of130g/m2，150g/m2and300g/m2was at least75mm,94mm and175mm respectively, and the overflow will not occur under the condition of5-year recurrence interval runoff flow. In addition, removal rates of SS of interception bag made by geotextile of130g/m2,150g/m2and300g/m2was56.0%,69.4%and76.5%respectively.更多还原