The study looked at pollution in cities that doesn't come from one specific source. They found that the main pollutants in urban runoff are solid particles, which are more concentrated than in sewage. Heavy metals and hydrocarbons in urban runoff are similar to those in untreated sewage. Pollutants like COD, BOD_5, and nitrogen are lower in urban runoff compared to sewage. Shopping centers have the worst runoff pollution. Metals in runoff mostly come from roofs, while hydrocarbons stick to particles. Other pollutants are less certain. Factors like rainfall, land use, air pollution, and land cleanliness affect urban runoff pollution.