Estimating Uncertainty in Global Mercury Emission Source and Deposition Receptor Relationships

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 (Hg anthr ) 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 Hg anthr 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 Hg anthr emission inventories.

Screening of Mercury pollution sources to European inland waters using high resolution earth surface data

“…Reducing Hg pollution will hence require control of atmospheric releases. In Europe, about 50% of the total deposition originates from releases within the EU (particularly from thermal power stations and cement production), the rest coming from long range transport (De Simone et al, 2017;AMAP/UNEP, 2019). Considering this large share of atmospheric deposition in Europe originating from other regions of the world, the international management of long-range atmospheric Hg pollution remains key also for Hg pollution reduction in European freshwaters.…”

Are mercury emissions from satellite electric propulsion an environmental concern?*

“…To compensate for the relatively limited number of scenarios included in the ensemble, the bootstrap method (Mudelsee 2014), was used to calculate the average deposition fields that would be produced if a more comprehensive set of parameters and initial conditions had been tested (Parker 2013). To avoid redundancy of information within the ensemble, a reduced or 'inspected' ensemble (Solazzo and Galmarini 2015) was identified to include only the results which differ the most (as in De Simone et al 2015Simone et al , 2017aSimone et al , 2017b. The similarity of the deposition fields was therefore assessed by means of both horizontal pattern correlation (Santer et al 1995(Santer et al , 1996 and the non-parametric Kolmogorov-Smirnov two-sample test, to include only those simulated Hg deposition fields where the test indicates that it is improbable (at a 95% level of confidence) that they belong to the same distribution.…”

A Chemical Transport Model Emulator for the Interactive Evaluation of Mercury Emission Reduction Scenarios

“…Thus, each of the countries involved will apply their own measures unilaterally. However, it is clear that Hg pollution is a global concern, and a number of studies indicate that a coordinated set of actions is required for Hg emission control to be effective, due to the large uncertainties regarding the processes that determine the global atmospheric cycle of Hg, and thus in establishing Source-Receptor (SR) relationships [4][5][6].…”

“…Indeed, each of the Best Available Technologies (BATs) and Best Environmental Practices (BEPs) to be considered for reducing Hg anthr emissions will result in a change of emission speciation [8], and therefore on the ratio of local to nonlocal Hg anthr deposition. Furthermore, it does not provide information concerning the statistical significance of the outcome of any given reduction approach, which is necessary when facing the significant degree of uncertainty in modelling the processes related to Hg cycle in the different ecosystem compartments [4,5,[9][10][11][12].…”

“…The output from HERMES allows the evaluation of the short-term (nominally one-year) effects on Hg anthr deposition fluxes due to Hg anthr emission perturbation. To cover a wide range of scenarios, in this work perturbations cover both emission reduction percentage and speciation, simulating the effect and the benefits of the BATs available to policy-makers for reducing Hg anthr emissions, within a source-receptor framework [4].…”