Distribution of magnetic properties of surface sediment and its implications on sediment provenance and transport in Pearl River Estuary

摘要

This study examines the magnetic properties of surface sediments and their implications on sediment provenance and transport in the Lingding Bay (LDB), which is the largest bay of Pearl River Estuary in China. The concentration of magnetic and high-coercivity minerals exhibits a low-high-low distribution pattern in the north-middle-south direction. The western LDB is mainly covered by finer magnetic mineral particles, whereas the eastern LDB is dominated by coarser particles. Three surface sediment provenances (i.e., three groups) are identified according to magnetic properties and particle size. Groups I and III have terrestrial sources from the East River and West/North River, respectively, whereas Group II is from a marine source in the adjacent sea. The distribution of these three sediment provenances and their magnetic properties indicate that surface sediments are transported towards the southern direction with a sediment sink that occurs in the outer LDB, as further confirmed by the grain size trend analysis results. The main sediment depocenter moves southward because of human interventions. The results further suggest that the ratio of saturation isothermal remanent magnetization to magnetic susceptibility (SIRM/chi) may be used as an indicator for distinguishing marine and terrestrial provenances, and the S ratio (S_100) may be employed as an indicator of sediment transport. Our findings demonstrate that sediment magnetic diagnosis provides an efficient approach to trace sediment provenance and transport and thereafter monitors the sediment process impacted by human intervention in estuaries worldwide.