| The pollution impact to the surface water bodies caused by urban runoff has received more and more attention. In order to prevent the surface water bodies from polluted by urban runoff and discuss the pollution characteristics and regulation of pollutants discharge of urban runoff, the distribution of the particulate size and the characteristic of potential pollution of road surface sediments of Xi'an were measured in fine weather, the water quality of roof runoff and road runoff were measured in wet weather, and the water quality of the main urban drainage channels during fine weather and wet weather were compared, in addition, regulation of pollutants discharge of road runoff in different types of rainfall were studied by artificial imitation rainfall experiment. The main results of this study are shown as followed:(1) By analyzing of road surface sediment samples of Xi'an, those road surface sediments causing urban runoff pollution mainly are those very fine particles whose diameters are less than 2mm. The pollutants content of road surface sediments reach to 66109mg/kg for lead, 154345mg/kg for zinc and 38227g/kg for COD, and the content of lead and zinc of road surface sediments decrease gradually with the size of particles increasing.(2) In the term of experiment the range of pollutant concentration of roof runoff is: SS=15 400mg/L, C0D=61 1541mg/L, the event mean concentration (EMC) is: SS=17.340.3mg/L, COD=116.7220.8mg/L, and the pollution of roof runoff mainly occures in the initial stages; There are obvious linear relations among COD, SS, and conductivity of roof runoff; The biologic degradation capacity of roof runoff is not good and ratio between BOD5 and COD is about 0.1 0.23.(3) The pollutant discharge load range of roof runoff caused by subrainfall is: Lcod=2.0 101g, Lss=0.422.3g; The pollutant discharge load caused by annual rainfall is: LyCOD= 1.07kg/(hm2 · a), LySS=0.24kg/(hm2 · a). Roof runoff fit Wash-off model quite well; First flush effect is obvious in some rainfall events, while unconspicuous in other rainfall events. First flush effect often occures in the initial stages of runoff which account for twenty percent of total runoff.(4) The results of artificial imitation rainfall experiment show that when both the weight of initial road surface sediment and the total rainfall is even, the pollutant load of the first type (big -middle- small) caused by subrainfall is most among the three types of rainfall designed followedby the third type (middle -big- small), and the second type (small -middle- big) is least; when the intensity of rainfall shows the trend of big -middle- small and middle -big- small, the change of pollutant concentration of runoff fit Wash-off model quite well, when the intensity of rainfall tends to small -middle- big, the change of pollutant concentration of runoff does not fit Wash-off model; First flush effect of the first type is most obvious among the three types of rainfall followed by the third type, and the second type is most unconspicuous. |
PDF Full Text Request