Abstract
Transboundary atmospheric pollution is a major concern throughout much of Southeast Asia (SEA), although most attention has, to date, focused on episodic haze events associated with biomass burning in the region. Here, we reconstruct long-term variations in transboundary inputs of chromium (Cr), an industrial pollutant, to Singapore over the period 1900–2017 by adopting a novel catchment-reservoir mass balance methodology that combines a national emissions inventory and a paleolimnological approach. Results show periods of low (before the 1950s) and relatively stable (the 1950s–1980s) levels of transboundary Cr deposition in Singapore followed by an unambiguous increase from ca. 1990 onwards, most likely linked to the onset of rapid industrialisation in neighbouring parts of Malaysia and Indonesia. Notably, from ca. 2000 onwards, fluxes of transboundary Cr deposition in Singapore further increased by 3% per year, almost doubling from 6 ± 3 tonne Cr yr−1 in 2000 to around 11 ± 3 tonne Cr yr−1 in 2017. This post-2000 rapid increase may reflect the effects of globalisation, pro-export driven economic growth policies and increasing capital inflows to the whole region, including from Singapore, all of which combined to drive industrialisation throughout much of SEA. The current trend of increasing transboundary pollution from anthropogenic activity highlights an urgent need for effective collaboration among countries in SEA in order to improve well-being and help guarantee sustainable development throughout the region.
Highlights
The atmospheric residence time of some pollutants, such as heavy metals, can range from days to weeks, enabling long-distance transportation that can result in deposition far from their sources [1] and transboundary atmospheric pollution (TAP) [2]
Transboundary atmospheric pollution is a major concern throughout much of Southeast Asia (SEA), most attention has, to date, focused on episodic haze events associated with biomass burning in the region
Estimates of W are associated with relatively small chronological errors as they were determined based on documentary sources of hydrological information that include clear calendar dates
Summary
The atmospheric residence time of some pollutants, such as heavy metals, can range from days to weeks, enabling long-distance transportation that can result in deposition far from their sources [1] and transboundary atmospheric pollution (TAP) [2]. In Southeast Asia (SEA), TAP typically peaks during periodic smoke haze events associated with the burning of forests and peatlands [4, 5] and with substantially reduced visibility [6] and enhanced respiratory distress in affected populations across the region [7]. Public pressure on governments to address TAP has been largely driven by, and skewed towards, these major haze pollution events [4, 8]. An example is the establishment of the legallybinding ‘Agreement on Transboundary Haze Pollution’ in 2002 among members of the Association of Southeast Asian Nations (ASEAN) to tackle biomass burning-related TAP [9]. Other nonbiomass burning-related pollutants, such as those arising from industrial activities, maritime traffic and fossil fuel power stations, tend to receive relatively little attention [7, 10]
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