Urban stormwater runoff contains pollutants like sediments, litter, and chemicals that harm water quality. This study looked at tiny particles in the water that make it murky and harm aquatic life. The researchers measured how much of these particles come from different urban surfaces during storms. They found that these particles carry nutrients like phosphorus, which can cause algal blooms in water bodies. This information will help identify where pollution in urban areas comes from and improve how we manage stormwater.