[Pollution Load Characteristics of Runoff from Urban Roofs of Different Materials]

It is of great significance to analyze the runoff pollution load characteristics of different roof materials to improve the estimation accuracy of urban non-point source pollution loads. Yangzhou City was selected as the study area. There, three types of roofs were chosen for rainfall-runoff monitoring, including a Chinese style tile roof, cement tile roof, and concrete flat roof. The pollutant concentrations, scour law, and first flush effect of the three types of roofs were compared. The results show that the event mean concentration (EMC) of total nitrogen (TN), total phosphorus (TP), permanganate index, and total suspended solids (TSS) in the runoff of Chinese style tile roofs are around 4-9 times that in the runoff of cement tile roofs. The rainfall intensity exhibits stronger effect on the change in pollutant concentrations of runoff from the Chinese style tile roof than that from the cement tile roof. The Pearson correlation coefficients (r) of rainfall intensity against TP and TSS in time series were 0.853 and 0.822, respectively. The first flush intensities of the three types of roof materials were in the order cement tile roof > concrete flat roof > Chinese style tile roof. It was found that 60.0% of the roof runoff pollution load could be reduced by intercepting 31.5%, 58.0%, and 60.4% of the initial runoff for the Chinese style tile roof, the cement tile roof, and the concrete flat roof, respectively. The actual emissions of TN, TP, and TSS, and the permanganate index in rainstorm events would be significantly underestimated when roof materials are not distinguished. This would have negative effects on the pollution control of urban non-point sources. It is demonstrated that the fine distinction of roof materials is able to improve the estimation accuracy of urban non-point source loads.