In this study, we separately collected rainwater sewer sediments from typical samples in Suzhou city, such as the urban commercial district, historical and cultural protection area, cultural and educational area, and living area, and analyzed the particle size distribution of the sediments and the characteristics of carbon, nitrogen, phosphorus content, and pollution load distribution under each graded particle size. The median particle size D50 of each sample point was 16.55-327.50 μm, and the particle size trend was as follows:commercial area > living area > historical and cultural protection area > cultural and educational area. D50 was related to the total organic carbon (TOC). The total nitrogen (TN), total phosphorus (TP), and ammonia nitrogen (NH4+-N) were significantly positively correlated, as were the pollutants. The spatial difference of ω(TOC), ω(TN), ω(TP), and ω(NH4+-N) in rainwater sewer sediments from different regions was as follows:commercial area > historical and cultural protection area > living area > cultural and educational area, in which ω(TOC) was 0.84%-6.76%, and ω(TN), ω(TP), and ω(NH4+-N) were 917.5-12707.1, 196.1-2524.8, and 9.3-156.8 mg·kg-1, respectively. TOC, TP, and NH4+-N pollution loads were mainly concentrated on particles ≤ 75 μm and 250-1000 μm. Street dust pollutants highly differed spatially, with a high content of attached pollutants on street dust particles with a particle size of ≤ 75 μm. Various pollutants migrated into the street dust-pipes, and TP and TN showed certain enrichment characteristics in the sewer. Controlling the transportation of street dust and the accumulation of sediments in the sewer can reduce the pollution of sediment into the rivers during the rainy season.
Keywords: ammonia nitrogen(NH4+-N); particle size distribution; rainwater sewer; sediments; total nitrogen(TN); total organic carbon(TOC).