Characterization and prediction of gross solids mass, organic matter, and total phosphorus in urban stormwater.

Gross solid materials carried in stormwater runoff can obstruct stormwater systems and transport nutrients and other pollutants to waterways. To characterize key drivers of the mass of gross solid delivered to stormwater systems and the amount of total phosphorus (TP) contributed by these solids, we collected these materials from the inlets of 13 stormwater control measures (SCMs) located in the Minneapolis - St. Paul metropolitan region in Minnesota, USA. Samples were collected from sampler devices during the years 2021-2022. Dry mass and mass organic matter (OM) were measured for all 420 samples collected, and 35% of all samples were analyzed for TP. A regression equation was developed to estimate TP mass for all samples based on measured OM. Additional analysis was performed to determine statistically significant factors that predicted the mass of gross solid material collected at each SCM. Annual dry mass, mass OM, and mass TP of the gross solid materials ranged from 6.1 to 76.9, 1.9 to 45.4, and 0.004 to 0.119 kg yr^-1, respectively. The tree canopy area over the street was the best predictor of the annual dry mass, OM mass, and TP mass delivered at the SCMs, with R² values of 0.44, 0.47, and 0.5, respectively.