scholarly journals Two new sources of reactive gaseous mercury in the free troposphere

2012 ◽  
Vol 12 (11) ◽  
pp. 29203-29233 ◽  
Author(s):  
H. Timonen ◽  
J. L. Ambrose ◽  
D. A. Jaffe
Keyword(s):  
Source Region ◽  
Elemental Mercury ◽  
Anthropogenic Pollution ◽  
Atmospheric Mercury ◽  
Free Troposphere ◽  
Mercury Deposition ◽  
Gaseous Elemental Mercury ◽  
Reactive Gaseous Mercury ◽  
Gaseous Mercury ◽  
The Pacific

Abstract. Mercury (Hg) is a neurotoxin that bioaccumulates in the food chain. Mercury is emitted to the atmosphere primarily in its elemental form, which has a long lifetime allowing global transport. It is known that atmospheric oxidation of gaseous elemental mercury (GEM) generates reactive gaseous mercury (RGM) which plays an important role in the atmospheric mercury cycle by enhancing the rate of mercury deposition to ecosystems. However, the primary GEM oxidants, and the sources and chemical composition of RGM are poorly known. Using speciated mercury measurements conducted at the Mt. Bachelor Observatory since 2005 we present two previously unidentified sources of RGM to the free troposphere (FT). Firstly, we observed elevated RGM concentrations, large RGM/GEM-ratios, and anti-correlation between RGM and GEM during Asian long-rang transport events, demonstrating that RGM is formed from GEM by in-situ oxidation in some anthropogenic pollution plumes in the FT. During the Asian pollution events the measured RGM/GEM-ratios reached peak values, up to ~0.20, which are significantly larger than ratios typically measured (RGM/GEM < 0.05) in the Asian source region. Secondly, we observed very high RGM levels – the highest reported in the FT – in clean air masses that were processed upwind of Mt. Bachelor Observatory over the Pacific Ocean. The high RGM concentrations (up to 700 pg m−3), high RGM/GEM-ratios (up to 1), and very low ozone levels during these events provide the first observational evidence indicating significant GEM oxidation in the lower FT. The identification of these processes changes our conceptual understanding of the formation and distribution of oxidized Hg in the global atmosphere.

scholarly journals Oxidation of elemental Hg in anthropogenic and marine airmasses

2013 ◽  
Vol 13 (5) ◽  
pp. 2827-2836 ◽  
Author(s):  
H. Timonen ◽  
J. L. Ambrose ◽  
D. A. Jaffe
Keyword(s):  
Source Region ◽  
Elemental Mercury ◽  
Anthropogenic Pollution ◽  
Atmospheric Mercury ◽  
Mercury Deposition ◽  
Air Masses ◽  
Gaseous Elemental Mercury ◽  
The Pacific ◽  
Global Transport ◽  
Clean Air

Abstract. Mercury (Hg) is a neurotoxin that bioaccumulates in the food chain. Mercury is emitted to the atmosphere primarily in its elemental form, which has a long lifetime allowing global transport. It is known that atmospheric oxidation of gaseous elemental mercury (GEM) generates reactive gaseous mercury (RGM) which plays an important role in the atmospheric mercury cycle by enhancing the rate of mercury deposition to ecosystems. However, the primary GEM oxidants, and the chemical composition of RGM are poorly known. Using speciated mercury measurements conducted at the Mt. Bachelor Observatory since 2005 we present two previously unidentified sources of RGM to the free troposphere (FT). Firstly, we observed elevated RGM concentrations, large RGM/GEM-ratios, and anti-correlation between RGM and GEM during Asian long-rang transport events, demonstrating that RGM is formed from GEM by in-situ oxidation in some anthropogenic pollution plumes in the FT. During the Asian pollution events the measured RGM/GEM-enhancement ratios reached peak values, up to ~0.20, which are significantly larger than ratios typically measured (RGM/GEM < 0.03) in the Asian source region. Secondly, we observed very high RGM levels – the highest reported in the FT – in clean air masses that were processed upwind of Mt. Bachelor Observatory over the Pacific Ocean. The high RGM concentrations (up to 700 pg m−3), high RGM/GEM-ratios (up to 1), and very low ozone levels during these events provide observational evidence indicating significant GEM oxidation in the lower FT in some conditions.

Gaseous mercury in coastal urban areas

2010 ◽  
Vol 7 (6) ◽  
pp. 537 ◽  
Author(s):  
Anne L. Soerensen ◽  
Henrik Skov ◽  
Matthew S. Johnson ◽  
Marianne Glasius
Keyword(s):  
Urban Areas ◽  
Marine Boundary Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Mercury Deposition ◽  
Mercury Emissions ◽  
Gaseous Elemental Mercury ◽  
Gaseous Mercury ◽  
Range Transport ◽  
Aquatic Food

Environmental context Mercury is a neurotoxin that bioaccumulates in the aquatic food web. Atmospheric emissions from urban areas close to the coast could cause increased local mercury deposition to the ocean. Our study adds important new data to the current limited knowledge on atmospheric mercury emissions and dynamics in coastal urban areas. Abstract Approximately 50% of primary atmospheric mercury emissions are anthropogenic, resulting from e.g. emission hotspots in urban areas. Emissions from urban areas close to the coast are of interest because they could increase deposition loads to nearby coastal waters as well as contribute to long range transport of mercury. We present results from measurements of gaseous elemental mercury (GEM) and reactive gaseous mercury (RGM) in 15 coastal cities and their surrounding marine boundary layer (MBL). An increase of 15–90% in GEM concentration in coastal urban areas was observed compared with the remote MBL. Strong RGM enhancements were only found in two cities. In urban areas with statistically significant GEM/CO enhancement ratios, slopes between 0.0020 and 0.0087 ng m–3 ppb–1 were observed, which is consistent with other observations of anthropogenic enhancement. The emission ratios were used to estimate GEM emissions from the areas. A closer examination of data from Sydney (Australia), the coast of Chile, and Valparaiso region (Chile) in the southern hemisphere, is presented.

scholarly journals Atmospheric mercury over sea ice during the OASIS-2009 campaign

2013 ◽  
Vol 13 (14) ◽  
pp. 7007-7021 ◽  
Author(s):  
A. Steffen ◽  
J. Bottenheim ◽  
A. Cole ◽  
T. A. Douglas ◽  
R. Ebinghaus ◽  
...  
Keyword(s):  
Sea Ice ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Mercury Deposition ◽  
International Polar Year ◽  
Bromine Oxide ◽  
Gaseous Elemental Mercury ◽  
Significant Difference ◽  
Mercury Cycle

Abstract. Measurements of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (PHg) were collected on the Beaufort Sea ice near Barrow, Alaska, in March 2009 as part of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) and OASIS-Canada International Polar Year programmes. These results represent the first atmospheric mercury speciation measurements collected on the sea ice. Concentrations of PHg averaged 393.5 pg m−3 (range 47.1–900.1 pg m−3) and RGM concentrations averaged 30.1 pg m−3 (range 3.5–105.4 pg m−3) during the two-week-long study. The mean concentration of GEM during the study was 0.59 ng m−3 (range 0.01–1.51 ng m−3) and was depleted compared to annual Arctic ambient boundary layer concentrations. It is shown that when ozone (O3) and bromine oxide (BrO) chemistry were active there is a positive linear relationship between GEM and O3, a negative one between PHg and O3, a positive correlation between RGM and BrO, and none between RGM and O3. For the first time, GEM was measured simultaneously over the tundra and the sea ice. The results show a significant difference in the magnitude of the emission of GEM from the two locations, with significantly higher emission over the tundra. Elevated chloride levels in snow over sea ice are proposed to be the cause of lower GEM emissions over the sea ice because chloride has been shown to suppress photoreduction processes of RGM to GEM in snow. Since the snowpack on sea ice retains more mercury than inland snow, current models of the Arctic mercury cycle may greatly underestimate atmospheric deposition fluxes because they are based predominantly on land-based measurements. Land-based measurements of atmospheric mercury deposition may also underestimate the impacts of sea ice changes on the mercury cycle in the Arctic. The predicted changes in sea ice conditions and a more saline future snowpack in the Arctic could enhance retention of atmospherically deposited mercury and increase the amount of mercury entering the Arctic Ocean and coastal ecosystems.

scholarly journals Natural and anthropogenic atmospheric mercury in the European Arctic: a fractionation study

2011 ◽  
Vol 11 (13) ◽  
pp. 6273-6284 ◽  
Author(s):  
A. O. Steen ◽  
T. Berg ◽  
A. P. Dastoor ◽  
D. A. Durnford ◽  
O. Engelsen ◽  
...  
Keyword(s):  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Seasonal Distribution ◽  
The Arctic ◽  
Mercury Distribution ◽  
Gaseous Elemental Mercury ◽  
Reactive Gaseous Mercury ◽  
Complete Dataset ◽  
European Arctic ◽  
Non Local

Abstract. Gaseous elemental mercury (GEM) is converted to reactive gaseous mercury (RGM) during springtime Atmospheric Mercury Depletion Events (AMDE). This study reports the longest time series of GEM, RGM and particle-bound mercury (PHg) concentrations from a European Arctic site. From 27 April 2007 until 31 December 2008 composite GEM, RGM and PHg measurements were conducted in Ny-Ålesund (78° 54′ N, 11° 53′ E). The average concentrations of the complete dataset were 1.6 ± 0.3 ng m−3, 8 ± 13 pg m−3 and 8 ± 25 pg m−3 for GEM, RGM and PHg, respectively. For the complete dataset the atmospheric mercury distribution was 99 % GEM, whereas RGM and PHg constituted <1 %. The study revealed a seasonal distribution of GEM, RGM and PHg previously undiscovered in the Arctic. Increased concentrations of RGM were observed during the insolation period from March through August, while increased PHg concentrations occurred almost exclusively during the spring AMDE period in March and April. The elevated RGM concentrations suggest that atmospheric RGM deposition also occurs during the polar summer. RGM was suggested as the precursor for the PHg existence, but long range transportation of PHg has to be taken into consideration. Still there remain gaps in the knowledge of how RGM and PHg are related in the environment. RGM and PHg accounted for on average about 10 % of the depleted GEM during AMDEs. Although speculative, the fairly low RGM and PHg concentrations supported by the predominance of PHg with respect to RGM and no clear meteorological regime associated with these AMDEs would all suggest the events to be of non-local origin. With some exceptions, no clear meteorological regime was associated with the GEM, RGM and PHg concentrations throughout the year.

Global Concentrations of Gaseous Elemental Mercury and Reactive Gaseous Mercury in the Marine Boundary Layer

2010 ◽  
Vol 44 (19) ◽  
pp. 7425-7430 ◽  
Author(s):  
Anne L. Soerensen ◽  
Henrik Skov ◽  
Daniel J. Jacob ◽  
Britt T. Soerensen ◽  
Matthew S. Johnson
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Elemental Mercury ◽  
Gaseous Elemental Mercury ◽  
Reactive Gaseous Mercury ◽  
Gaseous Mercury

scholarly journals High levels of reactive gaseous mercury observed at a high elevation research laboratory in the Rocky Mountains

2009 ◽  
Vol 9 (4) ◽  
pp. 15641-15671 ◽  
Author(s):  
X. Faïn ◽  
D. Obrist ◽  
A. G. Hallar ◽  
I. McCubbin ◽  
T. Rahn
Keyword(s):  
Relative Humidity ◽  
Elemental Mercury ◽  
High Elevation ◽  
Dominant Factor ◽  
Gaseous Elemental Mercury ◽  
Reactive Gaseous Mercury ◽  
Gaseous Mercury ◽  
Long Time ◽  
Chemical Cycling

Abstract. The chemical cycling and spatiotemporal distribution of mercury in the troposphere is poorly understood. We measured gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (HgP) along with CO, ozone, aerosols, and meteorological variables at Storm Peak Laboratory at an elevation of 3200 m a.s.l., in Colorado, from 28 April to 1 July 2008. The mean mercury concentrations were 1.6 ng m−3 (GEM), 20 pg m−3 (RGM) and 9 pg m−3 (HgP). We observed eight events of strongly enhanced atmospheric RGM levels with maximum concentrations up to 135 pg m−3. RGM enhancement events were unrelated to daytime/nighttime patterns and lasted for long time periods of 2 to 6 days. During seven of these events, RGM was inversely correlated to GEM (RGM/GEM regression slope ~ −0.1), but did not exhibit correlations with ozone, carbon monoxide, or aerosol concentrations. Relative humidity was the dominant factor affecting RGM levels with high RGM levels always present whenever relative humidity was below 40 to 50%. We conclude that RGM enhancements observed at Storm Peak Laboratory were not induced by pollution events and were related to oxidation of tropospheric GEM, but the mechanism remain unclear. Based on backtrajectory analysis and a lack of mass balance between RGM and GEM, we propose that in situ production of RGM may have occurred in some distance allowing for scavenging and/or deposition of some RGM prior to reaching the laboratory, and that GEM oxidation is an important tropospheric Hg sink. Our observations provide evidence that the tropospheric pool of mercury is frequently enriched in divalent mercury and that high RGM levels are not limited to the upper troposphere.

scholarly journals Previously unaccounted atmospheric mercury deposition in a midlatitude deciduous forest

2021 ◽  
Vol 118 (29) ◽  
pp. e2105477118
Author(s):  
Daniel Obrist ◽  
Eric M. Roy ◽  
Jamie L. Harrison ◽  
Charlotte F. Kwong ◽  
J. William Munger ◽  
...  
Keyword(s):  
Deciduous Forest ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Aquatic Biota ◽  
Carbon Dioxide Assimilation ◽  
Mercury Deposition ◽  
Gaseous Elemental Mercury ◽  
Photosynthetic Carbon ◽  
Proxy Measure ◽  
High Mercury

Mercury is toxic to wildlife and humans, and forests are thought to be a globally important sink for gaseous elemental mercury (GEM) deposition from the atmosphere. Yet there are currently no annual GEM deposition measurements over rural forests. Here we present measurements of ecosystem–atmosphere GEM exchange using tower-based micrometeorological methods in a midlatitude hardwood forest. We measured an annual GEM deposition of 25.1 µg ⋅ m−2 (95% CI: 23.2 to 26.7 1 µg ⋅ m−2), which is five times larger than wet deposition of mercury from the atmosphere. Our observed annual GEM deposition accounts for 76% of total atmospheric mercury deposition and also is three times greater than litterfall mercury deposition, which has previously been used as a proxy measure for GEM deposition in forests. Plant GEM uptake is the dominant driver for ecosystem GEM deposition based on seasonal and diel dynamics that show the forest GEM sink to be largest during active vegetation growing periods and middays, analogous to photosynthetic carbon dioxide assimilation. Soils and litter on the forest floor are additional GEM sinks throughout the year. Our study suggests that mercury loading to this forest was underestimated by a factor of about two and that global forests may constitute a much larger global GEM sink than currently proposed. The larger than anticipated forest GEM sink may explain the high mercury loads observed in soils across rural forests, which impair water quality and aquatic biota via watershed Hg export.

scholarly journals In-situ and Denuder Based Measurements of Elemental and Reactive Gaseous Mercury with Analysis by Laser-Induced Fluorescence. Results from the Reno Atmospheric Mercury Intercomparison Experiment

2016 ◽  
Author(s):  
Anthony J. Hynes ◽  
Stephanie Everhart ◽  
Dieter Bauer ◽  
James Remeika ◽  
Cheryl Tatum Ernest
Keyword(s):  
Single Photon ◽  
Thermal Dissociation ◽  
Elemental Mercury ◽  
Laser Induced Fluorescence ◽  
Atmospheric Mercury ◽  
Substantial Contribution ◽  
Gaseous Elemental Mercury ◽  
Gaseous Mercury ◽  
The University

Abstract. The University of Miami (UM) deployed a sequential two photon laser-induced fluorescence (2P-LIF) instrument for the in-situ measurement of gaseous elemental mercury, Hg(0), during the Reno Atmospheric Mercury Intercomparison Experiment (RAMIX) campaign. A number of extended sampling experiments, typically lasting 6–8 hours but on one occasion extending to ~ 24 hours, were conducted allowing the 2P-LIF measurements of Hg(0) concentrations to be compared with two independently operated instruments using gold amalgamation sampling coupled with Cold Vapor Atomic Fluorescence Spectroscopic (CVAFS) analysis. At the highest temporal resolution, ~ 5 minute samples, the three instruments measured concentrations that agreed to within 10–25 %. Measurements of total gaseous mercury (TGM) were made by using pyrolysis to convert total oxidized mercury (TOM) to Hg(0). TOM was then obtained by difference. Variability in the ambient Hg(0) concentration limited our sensitivity for measurement of ambient TOM using this approach. In addition, manually sampled KCl coated annular denuders were deployed and analyzed using thermal dissociation coupled with single photon LIF detection of Hg(0). The TOM measurements obtained were normally consistent with KCl denuder measurements obtained with two Tekran speciation systems and with the manual KCl denuder measurements but with very large uncertainty. They were typically lower than measurements reported by the University of Washington (UW) Detector for Oxidized Hg Species (DOHGS) system. The ability of the 2P-LIF pyrolysis system to measure TGM was demonstrated during one of the manifold HgBr2 spikes but the results did not agree well with those reported by the DOHGS system. We suggest that instrumental artifacts make a substantial contribution to the discrepancies in the reported measurements over the course of the RAMIX campaign. This suggests that caution should be used in drawing significant implications for the atmospheric cycling of mercury.

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