The researchers studied heavy metal pollution in sediments of the Yangtze River estuary. They found that industrial and agricultural activities were major sources of heavy metals like Cd and Hg. The south branch of the river had higher pollution levels due to industrial and domestic waste. Cd and Hg posed the highest ecological risks, with Cd being moderately to heavily polluted and Hg heavily polluted at most sites. Overall, the sediments in the estuary had very high potential ecological risks.