Environmental Pollution History at the Oujiang Estuary Since 5800 Years: Evidence from Trace Metal Elements

We investigated the concentrations, vertical distribution, and enrichment status of ten trace metal elements (Cr, Hg, Cu, Pb, Zn, Cd, As, Co, V, and Ni) in sediments of core D04 from the muddy area outside the Oujiang River Estuary. In addition to V, As, and Hg, the concentrations of Cr, Cu, Zn, Pb, Cd, Ni and Co were constrained by sediment grain size and organic matter. Although the concentrations of trace metals fluctuated during the 5.8–2.5 kyr BP period, overall variations remained relatively stable. However, during the 2.5–0 kyr BP period, the concentrations of Cd, Zn, Cu, Pb, Ni, Ni, and Cr showed an increasing trend within the fluctuations, ultimately reaching relatively high levels. The muddy area was lightly contaminated by heavy metals such as As, Hg, and Cu. The concentrations of Hg, As, and Cu have been continuously increasing since 2.5 kyr BP, indicating clear impacts from frequent human activities.