The study looked at pollution in rainwater runoff in Xiamen. They used GIS to calculate nitrogen and phosphorus levels in the runoff. After a 12 mm rainfall, they found that urban roads are the main sources of nitrogen and phosphorus pollution, followed by commercial and industrial areas. Nitrogen accounted for 93.4% and phosphorus for 92.0% of the pollution on Xiamen island. They also found that different types of land use have different levels of nitrogen and phosphorus pollution. The researchers suggested ways to reduce pollution in urban runoff.