The study looked at lead levels in the bottom waters of Jiaozhou Bay in 1990. They found that lead levels ranged from 2.96 to 9.41 ?g L-1, with pollution levels ranging from slight to moderate. The most polluted area shifted from the north of the bay mouth in May to the bay center in August. Sedimentation processes differed between the two months, with lead levels decreasing from the north of the bay mouth to the bay center in May, and from the bay center to the bay mouth in August. Overall, lead levels decreased as water exchanged between the bay and open waters.