Cross-shelf and along-shore transport of trace metals in shelf sediments of the East China Sea

Abstract

The transport and distribution of trace metals in marine sediments are fundamental to the biogeochemical functioning of coastal and oceanic ecosystems. This study investigates the spatial distribution and transport mechanisms of trace metals (Cd, Ni, Zn, and Cr) in the sediments of the inner shelf of the East China Sea . Results show that trace metal concentrations decrease from the nearshore to the outer shelf, with higher levels observed near the Changjiang River estuary. This pattern is attributed to riverine inputs, with the metals primarily transported by terrestrial materials. The distribution of these metals is strongly correlated with fine-grained sediments, which serve as the primary carriers of trace metals, facilitating their along-shore transport by coastal currents. In addition to along-shore transport, cross-shelf transport also plays an important role in distributing these trace metals. A notable tongue-shaped anomaly in metal concentrations centered at approximately 29°N suggests that trace metals are transported across the shelf from the inner to the outer shelf and even into the deep sea. These findings highlight the complex interaction between along-shore and cross-shelf transport mechanisms in controlling trace metal distribution. Understanding these processes is crucial for evaluating the impacts of trace metal transport on marine ecosystems and their role in global biogeochemical cycles.