An investigation on suspended solids sources in urban stormwater runoff using ⁷Be and ²¹⁰ Pb as tracers

Radionuclides ⁷Be and ²¹⁰Pb were used as tracers to identify suspended solid sources and transport pathways in the storm runoff events from urban catchments. Water samples were collected in runoff of storm events in Wuhan City, China. Suspended solids, COD, TN, TP, and the ⁷Be and ²¹⁰Pb activities in the suspended solids were analyzed. Following the pathway of urban runoff pollution, the rain precipitation, urban ground dust, gutter sediments, and sewer deposit samples were analyzed for ⁷Be and ²¹⁰Pb activities. The results show that the ⁷Be/²¹⁰Pb ratio decreased through the system from a value of 0.86±0.44 in ground dust, to 0.63±0.18 in suspended solids in storm runoff from the sewer outlet, to 0.55±0.31 in gutter sediments, and to 0.41±0.13 in combined sewer deposits. The ⁷Be/²¹⁰Pb ratio decrease suggests that 60±12% of suspended solids at sewer outlet originated from the drainage system sediments, the rest was from the wash-off of urban ground dust during the rainfall events. The ⁷Be and ²¹⁰Pb trace approach can give insight into the short-term source and transport of pollutant during storm runoff in urban drainage systems and it can help to develop management strategies.