To protect groundwater and urban ecological environment,much more sponge cities have been built in China.The sponge road is an important part of a sponge city.In recent years,Shijiazhuang Municipal Design Institute proposes a new sponge road structure,namely planting soil and crushed stone green belt,and it has been extensively used in Shijiazhuang City. In the design of the road structure,it is a key issue whether the infiltration rainwater quality pollutes the groundwater.There-fore,it is necessary to investigate the pollution of road rainwater runoff in Shijiazhuang City for the design of sponge road and the construction of sponge city.To obtain the characteristics of rainwater runoff pollution in Shijiazhuang City,four investiga-tion points are chosen at the intersection of the Nanerhuan Road and Yuxiang Street,the east gate of Hebei University of Sci-ence and Technology,the site under the Xierhuan Road and Zhongshan Road overpass,and the catch-basin along the roadside in Shij iazhuang City.The investigating points are located in the main road of Shij iazhuang urban area, which covers Shijiazhuang City,and can represent the pollution characteristics of road runoff in Shijiazhuang City.Six rainfalls are collected from March to June in 2017.The rainfall on 3,May is viewed as typical middle and light one which is studied in this paper.The concentration of COD,TP,TN,NH3-N and SS in road runoff is tested by potassium dichromate method,ammonium molyb-date spectrophotometry,potassium persulfate digestion-UV spectrophotometry and Nessler's reagent spectrophotometry and filter paper filtration,respectively.The concentrations of Zn ions and Pb ions are tested by inductively coupled plasma method. According to the test results,the concentration evolutions of COD,TP,TN,NH3-N,SS,Zn and Pb ion in runoff during rain-fall are studied.The results show that the contaminant concentration approximately decreases during the rainfall,and then maintain stable for 90 min.The relation between contaminant concentration and rainfall time follows the form of negative expo-nential function.Based on the investigation results,the design values of pollutant concentrations at the initial runoff and the long runoff of rainwater in Shijiazhuang are proposed by time-weighted average method and rainfall-weighted average method, respectively.The recommended values by former method for initial runoff in Shijiazhuang are as follows:TN,NH3-N,TP,SS and COD are 14.49 mg/L,10.93 mg/L,0.45 mg/L,651.00 mg/L and 437.73 mg/L.The recommended values by former method for long runoff of water in Shijiazhuang are as follows:in 90 min TN,NH3-N,TP,SS and COD are 8.05 mg/L,5.60 mg/L,0.59 mg/L,559.22 mg/L,and 237.96 mg/L,respectively.After 90 min they are 5.13 mg/L,4.11 mg/L,0.58 mg/L, 422.67 mg/L and 97.35 mg/L.The recommended values by later method for initial runoff in Shijiazhuang are as follows:TN, NH3-N,TP,SS and COD are 14.40 mg/L,10.86 mg/L,0.50 mg/L,684.10 mg/L and 440.08 mg/L.The recommended val-ues by later method for long runoff of water in Shijiazhuang are as follows:in 90 min TN,NH3-N,TP,SS and COD are 12.46 mg/L,9.19 mg/L,0.52 mg/L,642.80 mg/L and 363.92 mg/L.After 90 min they are 5.13 mg/L,4.11 mg/L,0.58 mg/L, 423.30 mg/L and 97.35 mg/L.Overall the proposed concentration values by the rainfall weighted average method are slightly larger than those by the time weighted average method.For hardly degradable Zn and Pb ions in the soil,the 30 min time-weighted concentration at the initial runoff and the long runoff of rainwater is proposed as the design values of runoff rainwater. The recommended design values of Zn and Pb ions are 0.67 mg/L and 0.11 mg/L,respectively.%为保护地下水和城市生态环境,中国已经开始大规模建设海绵城市.海绵道路是海绵城市建设的重要组成部分.近些年,石家庄市政设计研究院提出了种植土碎石绿化带新型海绵道路结构,并已在石家庄市推广使用.入渗雨水水质是否符合标准,是否会污染地下水是这种道路结构设计中亟待解决的关键问题.为此,弄清石家庄市道路雨水径流污染情况对于石家庄市海绵道路结构设计及海绵城市建设都极为必要.为获得石家庄市道路雨水径流污染特征,在石家庄市南二环与裕翔街口、河北科技大学东门口、西二环与中山路口高架桥下和路边雨水井设置了4个采样点.这些采样点位于石家庄市区主干路上,涵盖了石家庄市区的东部和西部,基本代表了石家庄市区道路雨水径流的污染状况.从2017年3月到6月一共收集了6场雨水,选取典型、可代表石家庄市中小雨道路雨水径流污染物平均状况特征的5月3日的调查结果进行分析.用重铬酸钾法测试了道路径流雨水COD浓度;用钼酸铵分光光度法测试了TP浓度;用过硫酸钾消解-紫外分光光度法测试了TN浓度;用纳氏试剂分光光度法测试了N H 3-N浓度;用滤纸过滤法测试了SS浓度;用电感耦合等离子体法测试了Zn离子和Pb离子浓度.根据测试结果,研究了降雨过程中道路径流雨水COD,TP,TN,NH3-N,SS,Zn离子和Pb离子浓度的演化规律.结果表明:石家庄市道路雨水径流污染物大致随降雨历时而衰减,降雨90 min后渐趋稳定;污染物浓度与降雨历时之间近似呈负指数函数关系.基于调查结果,分别利用时间加权平均和雨量加权平均方法提出了石家庄市道路初期雨水径流和长历时道路雨水径流的污染物浓度特征值.石家庄市初期雨水径流设计质量浓度的时间加权平均法建议值:TN为14.49 mg/L,NH3-N为10.93 mg/L,TP为0.45 mg/L,SS为651.00 mg/L,COD为437.73 mg/L;长历时道路雨水径流的污染物质量浓度值建议值:90 min以内,TN为8.05 mg/L,NH3-N为5.60 mg/L,TP为0.59 mg/L,SS为559.22 mg/L,COD为237.96 mg/L;90 min以后,TN为5.13 mg/L,NH3-N为4.11 mg/L,TP为0.58 mg/L,SS为422.67 mg/L,COD为97.35 mg/L.石家庄市初期雨水径流设计质量浓度的雨量加权平均法建议值:TN为14.40 mg/L,NH3-N为10.86 mg/L,TP为0.50 mg/L,SS为684.10 mg/L,COD为440.08 mg/L;长历时道路雨水径流的污染物质量浓度值建议值:90 min以内,TN为12.46 mg/L,NH3-N为9.19 mg/L,TP为0.52 mg/L,SS为642.80 mg/L,COD为363.92 mg/L;90 min以后,TN为5.13 mg/L,NH3-N为4.11 mg/L,TP为0.58 mg/L,SS为423.30 mg/L,COD为97.35 mg/L.总体来看,雨量加权平均法获得的设计浓度值比时间加权平均法获得的结果略大.Zn离子和Pb离子在土壤中极难降解,且危害大,建议取30 min时间加权质量浓度值作为初期径流雨水和长历时降雨道路径流雨水的设计浓度,Zn离子设计质量浓度建议值为0.67 mg/L,Pb离子设计浓度建议值为0.11 mg/L.
展开▼
