Source and sinks of 210Pb in oceanic margins of east coast Peninsular Malaysia

Abstract

A total of 97 surficial sediment samples were collected from the Kelantan River, Pahang River and offshore water of Peninsular Malaysia located in the east coast mainly in to investigate the sources and sinks of 210Pb in the southern South China Sea region. At the locations studied, the concentration activity of 210Pb was recorded from the Kelantan River (n = 28), Pahang River (n = 44) and offshore waters (n = 25), ranging from 2.7 ± 0.46 Bq/kg to 52.07 ± 5.23 Bq/kg, 8.65 ± 3.56 Bq/kg to 83.04 ± 6.71 Bq/kg, and 6.72 ± 2.92 Bq/kg to 42.2 ± 3.94 Bq/kg, respectively. Both riverine systems received huge amounts of 210Pb concentrations via mobilised particulate matter, where erosional igneous rocks and weathered sedimentary layers were prominent in elevating the amount of 210Pb from the source towards the sinks. In the offshore margins, the concentrations differed according to the source. As both rivers move towards the sinks in the coastal territories, boundary scavenging becomes prominent. In the offshore territories, a deficiency of 210Pb leads to excess 226Ra in the water column. Scavenged nuclide imported from several sources may increase the total concentrations lingering in the offshore waters of Peninsular Malaysia. Particulate matter mobilised from several sources via upwelling or downwelling in the bottom current through lateral transport further enhances the removal of particle-reactive nuclides from the water column. At the same time, atmospheric deposition via precipitation and transboundary mobilisation of aerosol by mineral dust may increase the total flux on the offshore waters of Peninsular Malaysia.