Abstract
Establishing mercury (Hg) source-receptor (SR) relationship matrices provides a tool to improve the understanding of the geographic relationship between regions of Hg release and its eventual deposition. SR relationship matrices are therefore a useful starting point for the development of policies aimed at reducing the impact of Hg emissions from anthropogenic activities (Hganthr) on sensitive ecosystems and areas potentially at risk of Hg contamination. A global Chemical Transport Model (CTM) has been used to simulate the emission, transport and fate of Hganthr from 12 source regions, considering a range of uncertainty in the modelled chemical and physical processes. This ensemble of simulations gives an estimate of the Hg deposition which derives from each source region, as well as an estimate of the uncertainty of the calculated deposition flux. The uncertainty has been calculated using the bootstrap method to estimate this uncertainty in terms of the normalised confidence interval amplitude of the mean (NCIAM). Within the calculated confidence ranges, for almost all regions the contribution to the Hg deposition flux from remote sources is greater than that from domestic sources. Europe and South Asia, where the contributions are statistically indistinguishable, are exceptions, as is East Asia, with local sources dominating the Hg deposition flux. East Asia is the single most important remote source region for most receptor regions. The results yield such high uncertainties in the deposition flux for many receptor regions that the results are unlikely to be taken into consideration by policy makers. This uncertainty is particularly relevant when considering the “domestic” contribution to regional deposition, highlighting the need for more studies to resolve remaining uncertainties in the atmospheric Hg cycle, and Hganthr emission inventories.
Highlights
Mercury (Hg) is considered to be a global pollutant since it threatens ecosystems which are remote from its emission sources, due principally to its long range transport in the atmosphere [1].The Minamata Convention on Mercury, October 2013, aims to reduce mercury contamination resulting from anthropogenic activities [2].The assessment of the magnitude of the impact of anthropogenic Hg (Hganthr ) from a given region has on ecosystems in other regions requires the characterisation of how Hg is released to the atmosphere
The emission speciation and injection height distribution are the major contributors to the uncertainty in the simulated Hg emissions from anthropogenic activities (Hganthr) deposition flux within a given region
Analysis of the normalised confidence interval amplitude for the mean (NCIAM) reveals that the global uncertainty in the annual mean deposition flux of Hganthr from each of the source regions in Figure 1, shows very different distributions
Summary
Mercury (Hg) is considered to be a global pollutant since it threatens ecosystems which are remote from its emission sources, due principally to its long range transport in the atmosphere [1]. The assessment of the magnitude of the impact of anthropogenic Hg (Hganthr ) from a given region has on ecosystems in other regions requires the characterisation of how Hg is released to the atmosphere. Knowledge of the amount and location of Hganthr emissions as well as information concerning their speciation and injection height distribution within the atmosphere. These emissions characteristics differ significantly among the various Hganthr emission sectors, but play. The trans-boundary dispersion of Hganthr over longer distances and its eventual deposition depends on the physical and chemical processes which occur in the atmosphere, including, but not limited to, red-ox reactions, global circulation patterns and the type and frequency of precipitation events, all of which vary over time, and generally differ from year to year [4,5,6]
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