The researchers collected sediment samples from different areas in Shanghai coastal zone to study heavy metal pollution. They found that copper, lead, zinc, and chromium levels were much higher than normal due to sewage discharge. These metals accumulated near sewage outlets and were more concentrated in high tidal flat sediments. The distribution of these metals was influenced by tidal action and human activities. Cadmium levels were low and not a major concern. Overall, the study shows that industrial and municipal sewage discharge is causing serious heavy metal pollution in Shanghai coastal zone.