Change in heavy metal depositional fluxes in the tidal flat of Liaodong Bay since 1955 and its relation to human activities

The Gaizhou tidal flat is one of the major wetlands located in the Liaohe estuary.A sediment core was acquired there in 2015.The concentrations of metal elements including As、Ca、Cr、Cu、Fe、Mn、Mg、Ni、Pb、Sr、Ti and Zn are measured by the authors with inductively coupled plasma atomic emission spectrometry (ICP-OES) for study of the historical input and fluxes of heavy metals.Mean particle size and total organic matter content are also analyzed for reference.Elements Fe and Ca, as proxy of grain size is selected for normalizing the other 10 kinds of metal elements and calculation of metal enrichment factors (EF) and anthropogenic heavy metal sedimentary fluxes.The characteristics of sediment components, as well as the significant correlation among the metal elements suggest that the source of metal elements in the sediment core is quite consistent, and the Gaizhou tidal flat are lightly polluted by six kinds of heavy metals including As, Cr, Mn, Ni, Pb and Zn over the past 60 years (the age of sediments is dated by artificial radionuclide¹³⁷ Cs).Contaminations due to anthropogenic activities are regarded as the main source of heavy metals pollution.