The scientists studied pollution in the upper part of the Huangpu River. They found four main sources of pollution: industries, businesses, homes, and animals. In this area, a lot of water is used, and a significant amount of sewage is released. Industries are the biggest polluters, followed by businesses and homes. Most of the pollution goes straight into the river, either from industries, after being treated at sewage plants, or through combined sewage systems. Understanding this pollution helps protect the environment and improve water quality in the region.