[Temporal and Spatial Distribution Characteristics and Source Apportionment of Runoff Pollution in Langfang City]

Urban runoff pollution can carry pollutants into the receiving water through scouring and leaching, causing black color and odor or eutrophication. Understanding and mastering the characteristics of runoff pollution is a prerequisite for the effective control of runoff pollution. This study aimed to comprehensively analyze the temporal and spatial distribution characteristics of runoff pollution and the correlation between pollutants in the urban area of Langfang City. Rainfall runoff samples were collected seven times by setting up 14 sampling sites within the urban area. The suspended solids (SS), chemical oxygen demand (COD), N, P, fecal E. coli, anionic surfactants, volatile phenols, and Zn, Cr⁶⁺, As, Cu, etc. were analyzed. The source and distribution of pollutants were summarized and analyzed through principal component analysis and cluster analysis. The results showed that the concentration of pollutants in runoff in Langfang City varied greatly at different times and locations. The average ρ(SS) at each point ranged from 150-500 mg·L^-1, and the average concentrations of COD, N, P, and fecal E. coli all exceeded those of the surface water standard Ⅴ. The average concentration of anionic surfactants, petroleum, and volatile phenols were between those of the surface water standard Ⅰ and standard Ⅳ. The concentrations of metal pollutants were relatively low. NH₄⁺-N had a positive correlation with total nitrogen (TN), volatile phenols, and As. COD had a certain positive correlation with TN, total phosphorus (TP), Cr⁶⁺, and As, whereas fecal E. coli had a certain negative correlation with Zn and Cu. The organic matter, P, Cu, and SS were probably derived from vehicle tires and road surfaces. All sampling sites could be roughly divided into four types according to the features of pollution:mainly commercial service areas, residential areas, larger arterial roads, and small roads between communities. The pollution of runoff in Langfang City was relatively serious, especially that of COD, N, and P. This research provides important reference values for the control and regulation of runoff pollution in urban areas and other northern cities.