| Stormwater samples were analyzed from 17 urban monitoring sites (n = 272) during spring 2011 to better understand urban land use suspended sediment contributions to receiving water bodies in central Missouri, USA. Samples from receiving water bodies had higher total concentrations of suspended sediment (323 mul/l and 319 mul/l, respectively) relative to urban sites (205 mul/l), which contained approximately 35% less total sediment. However, mean particle size was significantly lower (p < 0.001) from urban sites (59 mum) relative to receiving waters (167 mum and 131 mum, respectively). Receiving waters had higher silt volumes (173 mul/l and 148 mul/l, respectively) relative to urban sites (124 mul/l). The percentage of silt volume to total sediment volume for urban stormwater and receiving water bodies was 60%, 46%, and 53%, respectively. Over the course of the study period, silt volume increased by more than 43% and 53% in receiving waters. Collectively, results indicate a disproportionate contribution of fine sediment from the urban environment. Receiving waters' particle size class dynamics suggest the presence of a climate-driven punctuated equilibrium of sediment transport, which was not apparent in urban areas. This study represents one of the first suspended sediment particle size class investigations of an urban environment and holds global implications for urbanizing watersheds and aquatic ecosystem health. |
