An update of the Pb isotope inventory in post leaded-petrol Singapore environments

摘要

AbstractPb is a trace metal that tracks anthropogenic pollution in natural environments. Despite recent leaded petrol phase out around Southeast Asia, the region's growth has resulted in continued exposure of Pb from a variety of sources. In this study, sources of Pb into Singapore, a highly urbanised city-state situated in the central axis of Southeast Asia, are investigated using isotopic ratios and concentrations. We compiled data from our previous analyses of aerosols, incineration fly ash and sediments, with new data from analyses of soil from gas stations, water from runoff and round-island coastal seawater to obtain a spatio-temporal overview of sources of Pb into the Singapore environment. Using206Pb/207Pb ratio, we identified three main Pb source origins: natural Pb (1.215 ± 0.001), historic/remnant leaded petrol (1.123 ± 0.013), and present-day industrial and incinerated waste (1.148 ± 0.005). Deep reservoir sediments bore larger traces of Pb from leaded petrol, but present-day runoff waters and coastal seawater were a mix of industrial and natural sources with somewhat variable concentrations. We found temporal variability in Pb isotopic ratio in aerosols indicating alternating transboundary Pb sources to Singapore that correspond to seasonal changes in monsoon winds. By contrast, seasonal monsoon circulation did not significantly influence isotopic ratios of coastal seawater Pb. Instead, seawater Pb was driven more by location differences, suggesting stronger local-scale drivers of Pb such as point sources, water flushing, and isotope exchange. The combination of multiple historic and current sources of Pb shown in this study highlights the need for continued monitoring of Pb in Southeast Asia, especially in light of emerging industries and potential large sources of Pb such as coal combustion.Graphical abstractDisplay OmittedHighlights•Sources of Pb in Singapore are investigated using isotopic ratios (206Pb/207Pb).•Soils, runoff water, coastal water, aerosols, ashes and sediments studied.•3 sources found: natural, historic leaded petrol and industrial/incinerated waste.•Runoff water and coastal seawater are a mix of industrial and natural sources.•Processes controlling coastal seawater Pb and aerosol Pb are different.Pb sources in Singapore are reported as natural, historic leaded petrol and current industrial/incinerator waste based on Pb isotope and concentrations analyses.