A century long sedimentary record of anthropogenic lead (Pb), Pb isotopes and other trace metals in Singapore

Reconstructing the history of metal deposition in Singapore lake sediments contributes to understanding the anthropogenic and natural metal deposition in the data-sparse Southeast Asia. To this end, we present a sedimentary record of Pb, Pb isotopes and eleven other metals (Ag, As, Ba, Cd, Co, Cr, Cu, Ni, Tl, U and Zn) from a well-dated sediment core collected near the depocenter of MacRitchie Reservoir in central Singapore. Before the 1900s, the sedimentary Pb concentration was less than 2 mg/kg for both soil and sediment, with a corresponding Pb-206/Pb-207 of similar to 1.20. The Pb concentration increased to 55 mg kg in the 1990s, and correspondingly the Pb-206/Pb-207 decreased to less than 1.14. The Pb-206/Pb-207 in the core top sediment is concordant with the Pb-206/Pb-207 signal of aerosols in Singapore and other Southeast Asian cities, suggesting that Pb in the reservoir sediment was mainly from atmospheric deposition. Using the Pb concentration in the topmost layer of sediment, the estimated atmospheric Pb flux in Singapore today is similar to 1.6 x 10(-2) g/m(2) yr. The concentrations of eleven other metals preserved in the sediment were also determined. A principal component analysis showed that most of the metals exhibit an increasing trend towards 1990s with a local concentration peak in the mid-20th century. (C) 2016 Published by Elsevier Ltd.