Characteristics Study On Pollutants Transfer And Distribution In Roof-runoff System

With the acceleration of urbanization, diffuse pollution caused by roof runoff has becoming more and more serious. Characterizing the transport and distribution of pollutants in the micro-system of "roof-runoff—accumulated particles—roof material" plays an important role in the managemenet of roof-runoff pollution. This thesis takes the "micro-system' as the research object,and use the simulated rainfall method to explore the influence of different factors (including rainfall duration,antecedent dry day (ADD) and roof gradient) on the pollutants' transfer and fate in the "micro-system". In addition,the transfer and fate of lead originating from wet deposition and accumulated sediments was determined by using isotopic tracing technology. The main conclusions of this thesis as below:(1) The size of the accumulated particles on roof surface ranges from 40?m to 230?m. And the roof accumulated particles is mainly composed of feldspar which takes the proportion of 42.9% of total mineral composition. These properties meaning that the accumulation particles have strong ability of absorb pollutants.(2) The concentration of pollutants decreases with rainfall time and reaches to a steady level. It is positively related with ADD and roof slope, the higher pollutants concentration is appears in the events of longer ADD and greater roof slop.(3) The proportion of pollutants that transfer with roof-runoff is positively correlated with rainfall duration and roof slop, while is negatively related with ADD.The proportion of pollutants that appears in residual particles indicates negative correlation with rainfall duration and roof slope, while it is presents conspicuous positive correlation with ADD. Pollutants absorbed on roof materials present no evident correlation with rainfall duration and ADD; the respective proportion of roof material absorbed TP, As and Pb presents negative correlation with roof slope, while roof material absorbed TN presents no correlation with roof slope.(4) The proportion of lead which originating from accumulated particles and appearing in roof-runoff presents conspicuous positive correlation with rainfall intensity. The corresponding value of lead absorbed by roof material presents conspicuous negative correlation with rainfall intensity. The fate of lead which origination from rainwater has no obvious correlation with rainfall intensity.