The researchers studied pollution in Baiyangdian Lake by collecting water and sediment samples. They found that the lake is eutrophicated, with varying levels of pollution across different areas. Water quality has improved in recent years due to pollution control measures. Sediment pollution is severe, with high levels of nitrogen and phosphorus. Heavy metal pollution is mainly from cadmium, zinc, and copper, with some sites at high ecological risk. Pollution in the lake changes from north to south, with different factors influencing pollution levels.