Understanding factors influencing the detection of mercury policies in modelled Laurentian Great Lakes wet deposition
Open Access
- 1 October 2018
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Environmental Science: Processes & Impacts
- Vol. 20 (10), 1373-1389
- https://doi.org/10.1039/c8em00268a
Abstract
We used chemical transport modelling to better understand the extent to which policy-related anthropogenic mercury emissions changes (a policy signal) can be statistically detected in wet deposition measurements in the Great Lakes region on the subdecadal scale, given sources of noise. In our modelling experiment, we consider hypothetical regional (North American) and global (rest of the world) policy changes, consistent with existing policy efforts ((global) = -18%; (regional) = -30%) that divide an eight-year period. The magnitude of statistically significant (p < 0.1) pre- and post-policy period wet deposition differences, holding all else constant except for the policy change, ranges from -0.3 to -2.0% for the regional policy and -0.8 to -2.7% for the global policy. We then introduce sources of noisetrends and variability in factors that are exogenous to the policy actionand evaluate the extent to which the policy signals can still be detected. For instance, technology-related variability in emissions magnitude and speciation can shift the magnitude of differences between periods, in some cases dampening the policy effect. We have found that the interannual variability in meteorology has the largest effect of the sources of noise considered, driving deposition differences between periods to +/- 20%, exceeding the magnitude of the policy signal. However, our simulations suggest that gaseous elemental mercury concentration may be more robust to this meteorological variability in this region, and a stronger indicator of local/regional emissions changes. These results highlight the potential challenges of detecting statistically significant policy-related changes in Great Lakes wet deposition within the subdecadal scale.Funding Information
- Natural Sciences and Engineering Research Council of Canada (PGS-D 331020418, RGPIN-2018-04893)
- National Science Foundation (#ICER-1313755)
This publication has 85 references indexed in Scilit:
- Decreases in Mercury Wet Deposition over the United States during 2004–2010: Roles of Domestic and Global Background Emission ReductionsAtmosphere, 2013
- Mercury as a Global Pollutant: Sources, Pathways, and EffectsEnvironmental Science & Technology, 2013
- Correction to A Theoretical Study of the Oxidation of Hg0 to HgBr2 in the TroposphereEnvironmental Science & Technology, 2012
- All-Time Releases of Mercury to the Atmosphere from Human ActivitiesEnvironmental Science & Technology, 2011
- Mercury in the Great Lakes region: bioaccumulation, spatiotemporal patterns, ecological risks, and policyEcotoxicology, 2011
- Mercury policy in the Great Lakes states: past successes and future opportunitiesEcotoxicology, 2011
- Mercury temporal trends in top predator fish of the Laurentian Great LakesEcotoxicology, 2011
- Wet deposition of mercury in the U.S. and Canada, 1996–2005: Results and analysis of the NADP mercury deposition network (MDN)Atmospheric Environment, 2009
- Estimated Variability of National Atmospheric Deposition Program/Mercury Deposition Network Measurements Using Collocated SamplersEnvironmental Monitoring and Assessment, 2007
- Global lifetime of elemental mercury against oxidation by atomic bromine in the free troposphereGeophysical Research Letters, 2006