Submit to Atmosphere Review for Atmosphere Propose a Special Issue

Journal Menu

Journal Browser

► Journal Browser

Atmospheric Mercury

Special Issue Editors
Special Issue Information
Keywords
Published Papers

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Air Quality".

Deadline for manuscript submissions: closed (30 June 2014) | Viewed by 103249

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special issue Atmospheric Mercury book cover image

Share This Special Issue

Special Issue Editor

Prof. Dr. Robert W. Talbot <sup>†</sup>

E-Mail Website
Guest Editor

Institute for Climate and Atmospheric Science, Department of Earth & Atmospheric Sciences, University of Houston, Houston, TX 77204, USA
Interests: sources of anthropogenic atmospheric methane; autonomous drone system for detecting fugitive methane leaks; controls on ozone in Southern Texas; impact of Saharan dust on air quality along the U.S. Gulf Coast; sources and cycling of atmospheric mercury; green sustainable urban areas; Houston port activities impact on local air quality
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Mercury is a serious environmental toxin that is distributed globally by large-scale atmospheric circulations. Atmospheric chemists have only been studying mercury in earnest for approximately the past 10 years. In the troposphere elemental mercury (Hg^o) is observed ubiquitously with contemporary mixing ratios at the parts per quadrillion by volume (ppqv; 1 ng m⁻³ = 112 ppqv) level. The distributions of gaseous oxidized mercury (GOM) and particulate mercury (Hg^P) are not well documented at this time. In fact, the chemical composition of GOM is presently highly uncertain. At most mid-latitude locations, Hgo exhibits seasonality with the lowest mixing ratios in the fall and the greatest in late winter/early spring. It is highly desirable to conduct measurements of a variety of trace gases along with atmospheric mercury to facilitate source identification, but few studies have done so to date. A serious drawback in modeling atmospheric mercury is a lack of reliable rigorous emission inventories. Consequently, much work is needed to identify mercury sources and to quantify emission strengths.

There are few published papers on measurements of atmospheric mercury from aircraft. Initial work has shown that there is little to no Hg^o above the tropopause and that Hg^P is elevated there. The chemical cycling and transformations in the tropopause region are essentially unstudied. Both measurements and modeling are required to ascertain the important processes affecting atmospheric mercury in the tropopause region.

Manuscripts on all aspects of atmospheric mercury are welcome for this special issue.

Prof. Dr. Robert W. Talbot
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

elemental mercury
gaseous oxidized mercury
particulate mercury
chemical transformations of atmospheric mercury
cycling of atmospheric mercury
regional and global modeling of atmospheric mercury
emission inventories for atmospheric mercury

Published Papers (12 papers)

Download All Papers

Research

11630 KiB

Open AccessArticle

A Survey of Mercury in Air and Precipitation across Canada: Patterns and Trends

by Amanda S. Cole, Alexandra Steffen, Chris S. Eckley, Julie Narayan, Martin Pilote, Rob Tordon, Jennifer A. Graydon, Vincent L. St. Louis, Xiaohong Xu and Brian A. Branfireun

Atmosphere 2014, 5(3), 635-668; https://doi.org/10.3390/atmos5030635 - 11 Sep 2014

Cited by 72 | Viewed by 10352

Abstract

Atmospheric mercury (Hg) measurements from across Canada were compiled and analysed as part of a national Hg science assessment. Here we update long-term trends of Hg in air and precipitation, and present more extensive measurements on patterns and trends in speciated Hg species (gaseous elemental mercury—GEM, reactive gaseous mercury—RGM, and total particulate mercury on particles <2.5 μm—TPM_2.5) at several sites. A spatial analysis across Canada revealed higher air concentrations and wet deposition of Hg in the vicinity of local and regional emission sources, and lower air concentrations of Hg at mid-latitude maritime sites compared to continental sites. Diel and seasonal patterns in atmospheric GEM, RGM and TPM_2.5 concentrations reflected differences in patterns of anthropogenic emissions, photo-induced surface emissions, chemistry, deposition and mixing. Concentrations of GEM decreased at rates ranging from −0.9% to −3.3% per year at all sites where measurements began in the 1990s. Concentrations of total Hg in precipitation declined up to 3.7% yr⁻¹. Trends in RGM and TPM_2.5 were less clear due to shorter measurement periods and low concentrations, however, in spring at the high Arctic site (Alert) when RGM and TPM_2.5 concentrations were high, concentrations of both increased by 7%–10% per year. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

2367 KiB

Open AccessArticle

Programmable Thermal Dissociation of Reactive Gaseous Mercury, a Potential Approach to Chemical Speciation: Results from a Field Study

by Cheryl Tatum Ernest, Deanna Donohoue, Dieter Bauer, Arnout Ter Schure and Anthony J. Hynes

Atmosphere 2014, 5(3), 575-596; https://doi.org/10.3390/atmos5030575 - 13 Aug 2014

Cited by 8 | Viewed by 5802

Abstract

Programmable Thermal Dissociation (PTD) has been used to investigate the chemical speciation of Reactive Gaseous Mercury (RGM, Hg²⁺). RGM was collected on denuders and analyzed using PTD. The technique was tested in a field campaign at a coal-fired power plant in Pensacola, Florida. Stack gas samples were collected from ducts located after the electrostatic precipitator and prior to entering the stack. An airship was used to sample from the stack plume, downwind of the stack exit. The PTD profiles from these samples were compared with PTD profiles of HgCl₂. Comparison of stack and in-plume samples suggest that the chemical speciation are the same and that it is possible to track a specific chemical form of RGM from the stack and follow its evolution in the stack plume. Comparison of the measured plume RGM with the amount calculated from in-stack measurements and the measured plume dilution suggest that the stack and plume RGM concentrations are consistent with dilution. The PTD profiles of the stack and plume samples are consistent with HgCl₂ being the chemical form of the sampled RGM. Comparison with literature PTD profiles of reference mercury compounds suggests no other likely candidates for the speciation of RGM. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

1402 KiB

Open AccessArticle

Airborne Vertical Profiling of Mercury Speciation near Tullahoma, TN, USA

by Steve Brooks, Xinrong Ren, Mark Cohen, Winston T. Luke, Paul Kelley, Richard Artz, Anthony Hynes, William Landing and Borja Martos

Atmosphere 2014, 5(3), 557-574; https://doi.org/10.3390/atmos5030557 - 13 Aug 2014

Cited by 33 | Viewed by 7159

Abstract

Atmospheric transport and in situ oxidation are important factors influencing mercury concentrations at the surface and wet and dry deposition rates. Contributions of both natural and anthropogenic processes can significantly impact burdens of mercury on local, regional and global scales. To address these key issues in atmospheric mercury research, airborne measurements of mercury speciation and ancillary parameters were conducted over a region near Tullahoma, Tennessee, USA, from August 2012 to June 2013. Here, for the first time, we present vertical profiles of Hg speciation from aircraft for an annual cycle over the same location. These airborne measurements included gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate bound mercury (PBM), as well as ozone (O₃), sulfur dioxide (SO₂), condensation nuclei (CN) and meteorological parameters. The flights, each lasting ~3 h, were conducted typically one week out of each month to characterize seasonality in mercury concentrations. Data obtained from 0 to 6 km altitudes show that GEM exhibited a relatively constant vertical profile for all seasons with an average concentration of 1.38 ± 0.17 ng∙m⁻³. A pronounced seasonality of GOM was observed, with the highest GOM concentrations up to 120 pg∙m⁻³ in the summer flights and lowest (0–20 pg∙m⁻³) in the winter flights. Vertical profiles of GOM show the maximum levels at altitudes between 2 and 4 km. Limited PBM measurements exhibit similar levels to GOM at all altitudes. HYSPLIT back trajectories showed that the trajectories for elevated GOM (>70 pg∙m⁻³) or PBM concentrations (>30 pg∙m⁻³) were largely associated with air masses coming from west/northwest, while events with low GOM (<20 pg∙m⁻³) or PBM concentrations (<5 pg∙m⁻³) were generally associated with winds from a wider range of wind directions. This is the first set of speciated mercury vertical profiles collected in a single location over the course of a year. Even though there are current concerns that the KCl denuders used in this study may under-collect GOM, especially in the presence of elevated ozone, the collected data in this region shows the strong seasonality of oxidized mercury concentrations throughout the low to middle free troposphere. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

1425 KiB

Open AccessArticle

Temporal Variability of Atmospheric Total Gaseous Mercury in Windsor, ON, Canada

by Xiaohong Xu, Umme Akhtar, Kyle Clark and Xiaobin Wang

Atmosphere 2014, 5(3), 536-556; https://doi.org/10.3390/atmos5030536 - 12 Aug 2014

Cited by 8 | Viewed by 7835

Abstract

Atmospheric Total Gaseous Mercury (TGM) concentrations were monitored in Windsor, Ontario, Canada, during 2007 to 2011, to investigate the temporal variability of TGM. Over five years, the average concentration was 2.0 ± 1.3 ng/m³. A gradual decrease in annual TGM concentrations from 2.0 ng/m³ in year 2007 to 1.7 ng/m³ in 2009 was observed. The seasonal means show the highest TGM concentrations during the summer months (2.4 ± 2.0 ng/m³), followed by winter (1.9 ± 1.4 ng/m³), fall (1.8 ± 0.81 ng/m³), and spring (1.7 ± 0.73 ng/m³). Diurnal patterns in summer, fall, and winter were similar. A different diurnal pattern was observed in spring with an early depletion in the morning. The TGM concentrations were lower on weekends (1.8 ± 0.77 ng/m³) than on weekdays (2.0 ± 1.5 ng/m³), suggesting 10% of TGM in Windsor was attributable to emissions from industrial sectors in the region. Directional TGM concentrations also indicated southwesterly air masses were TGM enriched due to emissions from coal-fired power plants and industrial facilities. Correlation and principal component analysis identified that combustion of fossil fuel, ambient temperature, wind speed, synoptic systems, and O₃ concentrations influenced TGM concentrations significantly. Overall, inter-annual, seasonal, day-of-week, and diurnal variability was observed in Windsor. The temporal patterns were affected by anthropogenic and surface emissions, as well as atmospheric mixing and chemistry. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

2697 KiB

Open AccessArticle

Seasonal and Diurnal Variations of Total Gaseous Mercury in Urban Houston, TX, USA

by Xin Lan, Robert Talbot, Patrick Laine, Barry Lefer, James Flynn and Azucena Torres

Atmosphere 2014, 5(2), 399-419; https://doi.org/10.3390/atmos5020399 - 30 May 2014

Cited by 15 | Viewed by 8011

Abstract

Total gaseous mercury (THg) observations in urban Houston, over the period from August 2011 to October 2012, were analyzed for their seasonal and diurnal characteristics. Our continuous measurements found that the median level of THg was 172 parts per quadrillion by volume (ppqv), consistent with the current global background level. The seasonal variation showed that the highest median THg mixing ratios occurred in summer and the lowest ones in winter. This seasonal pattern was closely related to the frequency of THg episodes, energy production/consumption and precipitation in the area. The diurnal variations of THg exhibited a pattern where THg accumulated overnight and reached its maximum level right before sunrise, followed by a rapid decrease after sunrise. This pattern was clearly influenced by planetary boundary layer (PBL) height and horizontal winds, including the complex sea breeze system in the Houston area. A predominant feature of THg in the Houston area was the frequent occurrence of large THg spikes. Highly concentrated pollution plumes revealed that mixing ratios of THg were related to not only the combustion tracers CO, CO₂, and NO, but also CH₄ which is presumably released from oil and natural gas operations, landfills and waste treatment. Many THg episodes occurred simultaneously with peaks in CO, CO₂, CH₄, NO_x, and/or SO₂, suggesting possible contributions from similar sources with multi-source types. Our measurements revealed that the mixing ratios and variability of THg were primarily controlled by nearby mercury sources. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

4712 KiB

Open AccessArticle

Mercury Plumes in the Global Upper Troposphere Observed during Flights with the CARIBIC Observatory from May 2005 until June 2013

by Franz Slemr, Andreas Weigelt, Ralf Ebinghaus, Carl Brenninkmeijer, Angela Baker, Tanja Schuck, Armin Rauthe-Schöch, Hella Riede, Emma Leedham, Markus Hermann, Peter Van Velthoven, David Oram, Debbie O'Sullivan, Christoph Dyroff, Andreas Zahn and Helmut Ziereis

Atmosphere 2014, 5(2), 342-369; https://doi.org/10.3390/atmos5020342 - 28 May 2014

Cited by 22 | Viewed by 11656

Abstract

Tropospheric sections of flights with the CARIBIC (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrumented Container) observatory from May 2005 until June 2013, are investigated for the occurrence of plumes with elevated Hg concentrations. Additional information on CO, CO₂, CH₄, NOy, O₃, hydrocarbons, halocarbons, acetone and acetonitrile enable us to attribute the plumes to biomass burning, urban/industrial sources or a mixture of both. Altogether, 98 pollution plumes with elevated Hg concentrations and CO mixing ratios were encountered, and the Hg/CO emission ratios for 49 of them could be calculated. Most of the plumes were found over East Asia, in the African equatorial region, over South America and over Pakistan and India. The plumes encountered over equatorial Africa and over South America originate predominantly from biomass burning, as evidenced by the low Hg/CO emission ratios and elevated mixing ratios of acetonitrile, CH₃Cl and particle concentrations. The backward trajectories point to the regions around the Rift Valley and the Amazon Basin, with its outskirts, as the source areas. The plumes encountered over East Asia and over Pakistan and India are predominantly of urban/industrial origin, sometimes mixed with products of biomass/biofuel burning. Backward trajectories point mostly to source areas in China and northern India. The Hg/CO₂ and Hg/CH₄ emission ratios for several plumes are also presented and discussed. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

1509 KiB

Open AccessArticle

Tracing Sources of Total Gaseous Mercury to Yongheung Island off the Coast of Korea

by Gang S. Lee, Pyung R. Kim, Young J. Han, Thomas M. Holsen and Seung H. Lee

Atmosphere 2014, 5(2), 273-291; https://doi.org/10.3390/atmos5020273 - 30 Apr 2014

Cited by 15 | Viewed by 6887

Abstract

In this study, total gaseous mercury (TGM) concentrations were measured on Yongheung Island off the coast of Korea between mainland Korea and Eastern China in 2013. The purpose of this study was to qualitatively evaluate the impact of local mainland Korean sources and regional Chinese sources on local TGM concentrations using multiple tools including the relationship with other pollutants, meteorological data, conditional probability function, backward trajectories, and potential source contribution function (PSCF) receptor modeling. Among the five sampling campaigns, two sampling periods were affected by both mainland Korean and regional sources, one was caused by mainland vehicle emissions, another one was significantly impacted by regional sources, and, in the remaining period, Hg volatilization from oceans was determined to be a significant source and responsible for the increase in TGM concentration. PSCF identified potential source areas located in metropolitan areas, western coal-fired power plant locations, and the southeastern industrial area of Korea as well as the Liaoning province, the largest Hg emitting province in China. In general, TGM concentrations generally showed morning peaks (07:00~12:00) and was significantly correlated with solar radiation during all sampling periods. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

2118 KiB

Open AccessArticle

Mercury Speciation at a Coastal Site in the Northern Gulf of Mexico: Results from the Grand Bay Intensive Studies in Summer 2010 and Spring 2011

by Xinrong Ren, Winston T. Luke, Paul Kelley, Mark Cohen, Fong Ngan, Richard Artz, Jake Walker, Steve Brooks, Christopher Moore, Phil Swartzendruber, Dieter Bauer, James Remeika, Anthony Hynes, Jack Dibb, John Rolison, Nishanth Krishnamurthy, William M. Landing, Arsineh Hecobian, Jeffery Shook and L. Greg Huey

Atmosphere 2014, 5(2), 230-251; https://doi.org/10.3390/atmos5020230 - 29 Apr 2014

Cited by 18 | Viewed by 9855

Abstract

During two intensive studies in summer 2010 and spring 2011, measurements of mercury species including gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM), trace chemical species including O₃, SO₂, CO, NO, NO_Y, and black carbon, and meteorological parameters were made at an Atmospheric Mercury Network (AMNet) site at the Grand Bay National Estuarine Research Reserve (NERR) in Moss Point, Mississippi. Surface measurements indicate that the mean mercury concentrations were 1.42 ± 0.12 ng∙m⁻³ for GEM, 5.4 ± 10.2 pg∙m⁻³ for GOM, and 3.1 ± 1.9 pg∙m⁻³ for PBM during the summer 2010 intensive and 1.53 ± 0.11 ng∙m⁻³ for GEM, 5.3 ± 10.2 pg∙m⁻³ for GOM, and 5.7 ± 6.2 pg∙m⁻³ for PBM during the spring 2011 intensive. Elevated daytime GOM levels (>20 pg∙m⁻³) were observed on a few days in each study and were usually associated with either elevated O₃ (>50 ppbv), BrO, and solar radiation or elevated SO₂ (>a few ppbv) but lower O₃ (~20–40 ppbv). This behavior suggests two potential sources of GOM: photochemical oxidation of GEM and direct emissions of GOM from nearby local sources. Lack of correlation between GOM and Beryllium-7 (⁷Be) suggests little influence on surface GOM from downward mixing of GOM from the upper troposphere. These data were analyzed using the HYSPLIT back trajectory model and principal component analysis in order to develop source-receptor relationships for mercury species in this coastal environment. Trajectory frequency analysis shows that high GOM events were generally associated with high frequencies of the trajectories passing through the areas with high mercury emissions, while low GOM levels were largely associated the trajectories passing through relatively clean areas. Principal component analysis also reveals two main factors: direct emission and photochemical processes that were clustered with high GOM and PBM. This study indicates that the receptor site, which is located in a coastal environment of the Gulf of Mexico, experienced impacts from mercury sources that are both local and regional in nature. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

1477 KiB

Open AccessArticle

Benefits of European Climate Policies for Mercury Air Pollution

by Peter Rafaj, Janusz Cofala, Jeroen Kuenen, Artur Wyrwa and Janusz Zyśk

Atmosphere 2014, 5(1), 45-59; https://doi.org/10.3390/atmos5010045 - 10 Jan 2014

Cited by 15 | Viewed by 7631

Abstract

This paper presents the methodology and results of impact assessment of renewable energy policies on atmospheric emissions of mercury in Europe. The modeling exercise described here involves an interaction of several models. First, a set of energy scenarios has been developed with the REMix (Renewable Energy Mix) model that simulates different levels of penetration of renewable energies in the European power sector. The energy scenarios were input to the GAINS (Greenhouse Gas and Air Pollution Interactions and Synergies) model, which prepared projections of mercury releases to the atmosphere through 2050, based on the current air pollution control policies in each country. Data on mercury emissions from individual sectors were subsequently disaggregated to a fine spatial resolution using various proxy parameters. Finally, the dispersion of mercury in the atmosphere was computed by the chemistry transport model, implemented to the air quality system, Polyphemus. The simulations provided information on changes in concentrations and depositions of various forms of mercury over Europe. Scenarios that simulate a substantial expansion of renewable energies within the power sector indicate extensive co-benefits for mercury abatement, due to the restructuring of the energy system and changes in the fuel mix. The potential for mercury reductions in Europe depends on the rate of fuel switches and renewable technology deployment, but is also influenced by the stringency and timing of the air quality measures. The overall scope for co-benefits is therefore higher in regions relying on coal combustion as a major energy source. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

2737 KiB

Open AccessArticle

Regional Air Quality Model Application of the Aqueous-Phase Photo Reduction of Atmospheric Oxidized Mercury by Dicarboxylic Acids

by Jesse O. Bash, Annmarie G. Carlton, William T. Hutzell and O. Russell Bullock Jr.

Atmosphere 2014, 5(1), 1-15; https://doi.org/10.3390/atmos5010001 - 20 Dec 2013

Cited by 22 | Viewed by 7379

Abstract

In most ecosystems, atmospheric deposition is the primary input of mercury. The total wet deposition of mercury in atmospheric chemistry models is sensitive to parameterization of the aqueous-phase reduction of divalent oxidized mercury (Hg²⁺). However, most atmospheric chemistry models use a parameterization of the aqueous-phase reduction of Hg²⁺ that has been shown to be unlikely under normal ambient conditions or use a non mechanistic value derived to optimize wet deposition results. Recent laboratory experiments have shown that Hg²⁺ can be photochemically reduced to elemental mercury (Hg) in the aqueous-phase by dissolved organic matter and a mechanism and the rate for Hg²⁺ photochemical reduction by dicarboxylic acids (DCA) has been proposed. For the first time in a regional scale model, the DCA mechanism has been applied. The HO₂-Hg²⁺ reduction mechanism, the proposed DCA reduction mechanism, and no aqueous-phase reduction (NAR) of Hg²⁺ are evaluated against weekly wet deposition totals, concentrations and precipitation observations from the Mercury Deposition Network (MDN) using the Community Multiscale Air Quality (CMAQ) model version 4.7.1. Regional scale simulations of mercury wet deposition using a DCA reduction mechanism evaluated well against observations, and reduced the bias in model evaluation by at least 13% over the other schemes evaluated, although summertime deposition estimates were still biased by −31.4% against observations. The use of the DCA reduction mechanism physically links Hg²⁺ reduction to plausible atmospheric processes relevant under typical ambient conditions. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

1551 KiB

Open AccessArticle

Total Gaseous Mercury Concentration Measurements at Fort McMurray, Alberta, Canada

by Matthew T. Parsons, Daniel McLennan, Monique Lapalme, Curtis Mooney, Corinna Watt and Rachel Mintz

Atmosphere 2013, 4(4), 472-493; https://doi.org/10.3390/atmos4040472 - 13 Dec 2013

Cited by 19 | Viewed by 10189

Abstract

Observations are described from total gaseous mercury (TGM) concentrations measured at the Wood Buffalo Environmental Association (WBEA) Fort McMurray—Patricia McInnes air quality monitoring station—from 21 October 2010 through 31 May 2013, inclusively. Fort McMurray is approximately 380 km north-northeast of Edmonton, Alberta, and approximately 30 km south of major Canadian oil sands developments. The average TGM concentration over the period of this study was 1.45 ± 0.18 ng∙m⁻³. Principal component analysis suggests that observed TGM concentrations are correlated with meteorological conditions including temperature, relative humidity, and solar radiation, and also ozone concentration. There is no significant correlation between ambient concentrations of TGM and anthropogenic pollutants, such as nitrogen oxides (NO_X) and sulphur dioxide (SO₂). Principal component analysis also shows that the highest TGM concentrations observed are a result of forest fire smoke near the monitoring station. Back trajectory analysis highlights the importance of long-range transport, indicating that unseasonably high TGM concentrations are generally associated with air from the southeast and west, while unseasonably low TGM concentrations are a result of arctic air moving over the monitoring station. In general, TGM concentration appears to be driven by diel and seasonal trends superimposed over a combination of long-range transport and regional surface-air flux of gaseous mercury. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

1857 KiB

Open AccessArticle

Decreases in Mercury Wet Deposition over the United States during 2004–2010: Roles of Domestic and Global Background Emission Reductions

by Yanxu Zhang and Lyatt Jaeglé

Atmosphere 2013, 4(2), 113-131; https://doi.org/10.3390/atmos4020113 - 10 May 2013

Cited by 27 | Viewed by 8979

Abstract

Wet deposition of mercury (Hg) across the United States is influenced by changes in atmospheric conditions, domestic emissions and global background emissions. We examine trends in Hg precipitation concentrations at 47 Mercury Deposition Network (MDN) sites during 2004–2010 by using the GEOS-Chem nested-grid Hg simulation. We run the model with constant anthropogenic emissions and subtract the model results from the observations. This helps to remove the variability in observed Hg concentrations caused by meteorological factors, including precipitation. We find significant decreasing trends in Hg concentrations in precipitation at MDN sites in the Northeast (−4.1 ± 0.49% yr⁻¹) and Midwest (−2.7 ± 0.68% y^r−1). Over the Southeast (−0.53 ± 0.59% yr⁻¹), trends are weaker and not significant, while over the West, trends are highly variable. We conduct model simulations assuming a 45% decrease in Hg emissions from domestic sources in the modeled period and a uniform 12% decrease in background atmospheric Hg concentrations. The combination of domestic emission reductions and decreasing background concentrations explains the observed trends over the Northeast and Midwest, with domestic emission reductions accounting for 58–46% of the decreasing trends. Over the Southeast, we overestimate the observed decreasing trend, indicating potential issues with our assumption of uniformly decreasing background Hg concentrations. Full article

(This article belongs to the Special Issue Atmospheric Mercury)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Atmospheric Mercury

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (12 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI