scholarly journals Investigation of processes controlling GEM oxidation at mid-latitudinal marine, coastal, and inland sites

2016 ◽  
Author(s):  
Z. Ye ◽  
H. Mao ◽  
C.-J. Lin ◽  
S. Y. Kim
Keyword(s):  
Marine Boundary Layer ◽  
State Of The Art ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Chemical Mechanism ◽  
Atmospheric Conditions ◽  
Gaseous Elemental Mercury ◽  
Mixing Ratios ◽  
Marine Site ◽  
Study Sites

Abstract. A box model incorporating a state-of-the-art chemical mechanism for atmospheric mercury (Hg) cycling was developed to investigate oxidation of gaseous elemental mercury (GEM) at three locations in the northeastern United States: Appledore Island (marine), Thompson Farm (coastal, rural), and Pack Monadnock (inland, rural, elevated). The chemical mechanism improved model's ability to simulate the formation of gaseous oxidized mercury (GOM) at the study sites. At the coastal and inland sites, GEM oxidation was predominated by O3 and OH, contributing 80–99 % of total GOM production during daytime. H2O2 initiated GEM oxidation was significant (~ 33 % of the total GOM) at the inland site during nighttime. In the marine boundary layer (MBL), Br and BrO were dominant GEM oxidants contributing ~ 70 % of the total GOM production during mid-day, while O3 dominated GEM oxidation (50–90 % of GOM production) over the remaining day. Following the production of HgBr from GEM + Br, HgBr was oxidized by BrO, HO2, OH, ClO, and IO to form Hg(II) brominated GOM species. However, under atmospheric conditions, the prevalent GEM oxidants in the MBL could be Br / BrO or O3 / OH depending on Br and BrO mixing ratios. Relative humidity and products of the CH3O2 + BrO reaction possibly affected significantly the mixing ratios of Br or BrO radicals and subsequently GOM formation. Gas-particle partitioning could be potentially important in the production of GOM as well as Br and BrO at the marine site.

scholarly journals Investigation of processes controlling summertime gaseous elemental mercury oxidation at midlatitudinal marine, coastal, and inland sites

2016 ◽  
Vol 16 (13) ◽  
pp. 8461-8478 ◽  
Author(s):  
Zhuyun Ye ◽  
Huiting Mao ◽  
Che-Jen Lin ◽  
Su Youn Kim
Keyword(s):  
Marine Boundary Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Box Model ◽  
Chemical Mechanism ◽  
Gaseous Elemental Mercury ◽  
Diurnal Cycles ◽  
Mixing Ratios ◽  
Halogen Chemistry ◽  
Marine Site

Abstract. A box model incorporating a state-of-the-art chemical mechanism for atmospheric mercury (Hg) cycling was developed to investigate the oxidation of gaseous elemental mercury (GEM) at three locations in the northeastern United States: Appledore Island (AI; marine), Thompson Farm (TF; coastal, rural), and Pack Monadnock (PM; inland, rural, elevated). The chemical mechanism in this box model included the most up-to-date Hg and halogen chemistry. As a result, the box model was able to simulate reasonably the observed diurnal cycles of gaseous oxidized mercury (GOM) and chemical speciation bearing distinct differences between the three sites. In agreement with observations, simulated GOM diurnal cycles at AI and TF showed significant daytime peaks in the afternoon and nighttime minimums compared to flat GOM diurnal cycles at PM. Moreover, significant differences in the magnitude of GOM diurnal amplitude (AI > TF > PM) were captured in modeled results. At the coastal and inland sites, GEM oxidation was predominated by O3 and OH, contributing 80–99 % of total GOM production during daytime. H2O2-initiated GEM oxidation was significant (∼ 33 % of the total GOM) at the inland site during nighttime. In the marine boundary layer (MBL) atmosphere, Br and BrO became dominant GEM oxidants, with mixing ratios reaching 0.1 and 1 pptv, respectively, and contributing ∼ 70 % of the total GOM production during midday, while O3 dominated GEM oxidation (50–90 % of GOM production) over the remaining day when Br and BrO mixing ratios were diminished. The majority of HgBr produced from GEM+Br was oxidized by NO2 and HO2 to form brominated GOM species. Relative humidity and products of the CH3O2+BrO reaction possibly significantly affected the mixing ratios of Br or BrO radicals and subsequently GOM formation. Gas–particle partitioning could potentially be important in the production of GOM as well as Br and BrO at the marine site.

scholarly journals Gaseous elemental mercury depletion events observed at Cape Point during 2007–2008

2010 ◽  
Vol 10 (3) ◽  
pp. 1121-1131 ◽  
Author(s):  
E.-G. Brunke ◽  
C. Labuschagne ◽  
R. Ebinghaus ◽  
H. H. Kock ◽  
F. Slemr
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Chemical Mechanism ◽  
Polar Regions ◽  
Gaseous Elemental Mercury ◽  
Transport Distance ◽  
Gaseous Mercury ◽  
Urban Emissions

Abstract. Gaseous mercury in the marine boundary layer has been measured with a 15 min temporal resolution at the Global Atmosphere Watch station Cape Point since March 2007. The most prominent features of the data until July 2008 are the frequent occurrences of pollution (PEs) and depletion events (DEs). Both types of events originate mostly within a short transport distance (up to about 100 km), which are embedded in air masses ranging from marine background to continental. The Hg/CO emission ratios observed during the PEs are within the range reported for biomass burning and industrial/urban emissions. The depletion of gaseous mercury during the DEs is in many cases almost complete and suggests an atmospheric residence time of elemental mercury as short as a few dozens of hours, which is in contrast to the commonly used estimate of approximately 1 year. The DEs observed at Cape Point are not accompanied by simultaneous depletion of ozone which distinguishes them from the halogen driven atmospheric mercury depletion events (AMDEs) observed in Polar Regions. Nonetheless, DEs similar to those observed at Cape Point have also been observed at other places in the marine boundary layer. Additional measurements of mercury speciation and of possible mercury oxidants are hence called for to reveal the chemical mechanism of the newly observed DEs and to assess its importance on larger scales.

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 Speciated mercury at marine, coastal, and inland sites in New England – Part 1: Temporal variability

2012 ◽  
Vol 12 (11) ◽  
pp. 5099-5112 ◽  
Author(s):  
H. Mao ◽  
R. Talbot
Keyword(s):  
New England ◽  
Marine Boundary Layer ◽  
Limit Of Detection ◽  
Inversion Layer ◽  
Warm Season ◽  
Elemental Mercury ◽  
Positive Trend ◽  
Gaseous Elemental Mercury ◽  
Mixing Ratios ◽  
Nocturnal Inversion

Abstract. A comprehensive analysis was conducted using long-term continuous measurements of gaseous elemental mercury (Hg0), reactive gaseous mercury (RGM), and particulate phase mercury (HgP) at coastal (Thompson Farm, denoted as TF), marine (Appledore Island, denoted as AI), and elevated inland (Pac Monadnock, denoted as PM) sites from the AIRMAP Observatories in southern New Hampshire, USA. Decreasing trends in background Hg0 were identified in the 7.5- and 5.5-yr records at TF and PM with decline rates of 3.3 parts per quadrillion by volume (ppqv) yr−1 and 6.3 ppqv yr−1, respectively. Common characteristics at these sites were the reproducible annual cycle of Hg0 with its maximum in winter-spring and minimum in fall, comprised of a positive trend in the warm season (spring – early fall) and a negative one in the cool season (late fall – winter). Year-to-year variability was observed in the warm season decline in Hg0 at TF varying from a minimum total (complete) seasonal loss of 43 ppqv in 2009 to a maximum of 92 ppqv in 2005, whereas variability remained small at AI and PM. The coastal site TF differed from the other two sites with its exceptionally low levels (as low as below 50 ppqv) in the nocturnal inversion layer possibly due to dissolution in dew water. Measurements of Hg0 at PM exhibited the smallest diurnal to annual variability among the three environments, where peak levels rarely exceeded 250 ppqv and the minimum was typically 100 ppqv. It should be noted that summertime diurnal patterns at TF and AI were opposite in phase indicating strong sink(s) for Hg0 during the day in the marine boundary layer, which was consistent with the hypothesis of Hg0 oxidation by halogen radicals there. Mixing ratios of RGM in the coastal and marine boundary layers reached annual maxima in spring and minima in fall, whereas at PM levels were generally below the limit of detection (LOD) except in spring. RGM levels at AI were higher than at TF and PM indicating a stronger source strength in the marine environment. Mixing ratios of HgP at AI and TF were close in magnitude to RGM levels and were mostly below 1 ppqv. Diurnal variation in HgP was barely discernible at TF and AI in spring and summer. Higher levels of HgP were observed during the day, while values that were smaller, but above the LOD, occurred at night.

scholarly journals Ten years trends in atmospheric mercury concentrations, meteorological effects and climate variables at Zeppelin, Ny-Ålesund

2013 ◽  
Vol 13 (1) ◽  
pp. 2273-2312
Author(s):  
T. Berg ◽  
K. A. Pfaffhuber ◽  
A. S. Cole ◽  
O. Engelsen ◽  
A. Steffen
Keyword(s):  
Relative Humidity ◽  
Wind Direction ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Climate Indices ◽  
Atmospheric Conditions ◽  
Gaseous Elemental Mercury ◽  
Surface Emission ◽  
Wind Speeds

Abstract. Results from ten years of gaseous elemental mercury (GEM) measurements at Zeppelin Station, Ny-Ålesund, Svalbard, show no overall annual trend between 2000 and 2009. Seasonal trend analysis showed significantly decreasing trends in January, February, March and June and significantly increasing trends in May and July through December. Results showed that atmospheric mercury depletion events (AMDEs) were equally distributed between April and May with only a few having been observed in March and June. A negative correlation between AMDEs and temperature is reported and supports earlier observations that AMDEs tend to occur at low temperatures. Lower concentrations of GEM were seen at lower temperatures below a threshold of 0°C. The occurrence of AMDEs and wind direction were well correlated with the lowest GEM measured when the wind direction was from the Arctic Ocean region. Wind speed was found to not correlate with AMDEs, but the lowest GEM concentrations were observed at low wind speeds between 4 and 11 m s−1. AMDEs and relative humidity did not correlate well, but the lowest GEM levels appeared when the relative humidity was between 80 and 90%. Diurnal variation was observed especially during the month March and is likley due to daytime snow surface emission induced by solar radiation. Relationships between GEM concentration and the Northern Hemisphere climate indices were investigated to assess if these climate parameters might reflect different atmospheric conditions that enhance or reduce spring AMDE activity. No consistent pattern was observed.

scholarly journals Trends in long-term gaseous mercury observations in the Arctic and effects of temperature and other atmospheric conditions

2010 ◽  
Vol 10 (10) ◽  
pp. 4661-4672 ◽  
Author(s):  
A. S. Cole ◽  
A. Steffen
Keyword(s):  
Polar Vortex ◽  
Elemental Mercury ◽  
Early Spring ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Atmospheric Conditions ◽  
Climate Data ◽  
Gaseous Elemental Mercury ◽  
Teleconnection Patterns ◽  
Kinetic Calculations

Abstract. Gaseous elemental mercury (GEM) measurements at Alert, Canada, from 1995 to 2007 were analyzed for statistical time trends and for correlations with meteorological and climate data. A significant decreasing trend in annual GEM concentration is reported at Alert, with an estimated slope of −0.0086 ng m−3 yr−1 (−0.6% yr−1) over this 13-year period. It is shown that there has been a shift in the month of minimum mean GEM concentration from May to April due to a change in the timing of springtime atmospheric mercury depletion events (AMDEs). These AMDEs are found to decrease with increasing local temperature within each month, both at Alert and at Amderma, Russia. These results support the temperature dependence suggested by previous experimental results and theoretical kinetic calculations on both bromine generation and mercury oxidation and highlight the potential for changes in Arctic mercury chemistry with climate. A correlation between total monthly AMDEs at Alert and the Polar/Eurasian Teleconnection Index was observed only in March, perhaps due to higher GEM inputs in early spring in those years with a weak polar vortex. A correlation of AMDEs at Alert with wind direction supports the origin of mercury depletion events over the Arctic Ocean, in agreement with a previous trajectory study of ozone depletion events. Interannual variability in total monthly depletion event frequency at Alert does not appear to correlate significantly with total or first-year northern hemispheric sea ice area or with other major teleconnection patterns. Nor do AMDEs at either Alert or Amderma correlate with local wind speed, as might be expected if depletion events are sustained by stable, low-turbulence atmospheric conditions. The data presented here – both the change in timing of depletion events and their relationship with temperature – can be used as additional constraints to improve the ability of models to predict the cycling and deposition of mercury in the Arctic.

scholarly journals Dynamic recycling of gaseous elemental mercury in the boundary layer of the Antarctic Plateau

2012 ◽  
Vol 12 (7) ◽  
pp. 18133-18161 ◽  
Author(s):  
A. Dommergue ◽  
M. Barret ◽  
J. Courteaud ◽  
P. Cristofanelli ◽  
C. P. Ferrari ◽  
...  
Keyword(s):  
Mixing Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Photochemical Reactions ◽  
Solar Irradiation ◽  
The Arctic ◽  
Gaseous Elemental Mercury ◽  
Antarctic Plateau ◽  
Mixing Ratios ◽  
The Antarctic

Abstract. Gaseous elemental mercury (Hg(0)) was investigated in the troposphere and in the interstitial air extracted from the snow at Dome Concordia station (alt. 3320 m) on the Antarctic Plateau during January 2009. Measurements showed evidence of a very dynamic and daily cycling of Hg(0) inside the mixing layer with a range of values from 0.2 ng m−3 up to 2.3 ng m−3. During low solar irradiation periods, fast Hg(0) oxidation processes in a confined layer were observed leading to an enrichment of the upper snow layers in divalent Hg. Unexpectedly high Hg(0) concentrations for such a remote place were measured under higher solar irradiation due to the reemission of Hg(0) by the snowpack via photochemical reactions. Hg(0) concentrations showed a negative correlation with ozone mixing ratios, which contrasts with atmospheric mercury depletion events observed during the Arctic spring. It remains unclear whether halogens are involved in Hg(0) oxidation. We suggest that snow surfaces may play a role in promoting the heterogeneous oxidation of Hg(0). The cycling of other oxidants should be investigated together with Hg in order to clarify the complex reactivity on the Antarctic Plateau.

scholarly journals Total gaseous mercury depletion events observed at Cape Point during 2007–2008

2009 ◽  
Vol 9 (5) ◽  
pp. 20979-21009 ◽  
Author(s):  
E.-G. Brunke ◽  
C. Labuschagne ◽  
R. Ebinghaus ◽  
H. H. Kock ◽  
F. Slemr
Keyword(s):  
Marine Boundary Layer ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Chemical Mechanism ◽  
Polar Regions ◽  
Air Masses ◽  
Transport Distance ◽  
Gaseous Mercury ◽  
Urban Emissions ◽  
Emission Ratios

Abstract. Gaseous mercury in the marine boundary layer has been measured with a 15 min temporal resolution at the Global Atmosphere Watch station Cape Point since March 2007. The most prominent features of the data until July 2008 are the frequent occurrences of pollution (PEs) and depletion events (DEs). Both types of events originate mostly within a short transport distance (up to about 100 km), which are embedded in air masses ranging from marine background to continental. The Hg/CO emission ratios observed during the PEs are within the range reported for biomass burning and industrial/urban emissions. The depletion of gaseous mercury during the DEs is almost quantitative in many cases and suggests a lifetime of elemental mercury as short as a few dozens of hours, which is in contrast to the commonly used estimate of approximately 1 year. The characteristics of the DE occurrence at Cape Point is neither similar to the halogen driven atmospheric mercury depletion events (AMDEs) observed in Polar Regions nor to the DEs reported for plumes of urban air. Additional measurements are necessary to reveal the chemical mechanism of the observed DEs and to assess its importance on larger scales.

scholarly journals Overview of the 2007 and 2008 campaigns conducted as part of the Greenland Summit Halogen-HO<sub>x</sub> Experiment (GSHOX)

2012 ◽  
Vol 12 (7) ◽  
pp. 17135-17150
Author(s):  
J. L. Thomas ◽  
J. E. Dibb ◽  
J. Stutz ◽  
R. von Glasow ◽  
S. Brooks ◽  
...  
Keyword(s):  
Marine Boundary Layer ◽  
Vertical Mixing ◽  
Greenland Ice Sheet ◽  
Elemental Mercury ◽  
Near Surface ◽  
Gaseous Elemental Mercury ◽  
Mixing Ratios ◽  
The North ◽  
Polar Snow ◽  
Active Bromine

Abstract. From 10 May through 17 June, 2007 and 6 June through 9 July, 2008 intensive sampling campaigns at Summit, Greenland confirmed that active bromine chemistry is occurring in and above the snow pack at the highest part of the Greenland ice sheet (72°36' N, 38° 25' W and 3.2 km a.s.l.). Direct measurements found BrO and soluble gas phase Br− mixing ratios in the low pptv range on many days (maxima <10 pptv). Conversion of up to 200 pg m−3 of gaseous elemental mercury (GEM) to reactive gaseous mercury (RGM) and enhanced OH relative to HO2 plus RO2 confirm that active bromine chemistry is impacting chemical cycles even at such low abundances of reactive bromine species. However, it does not appear that Bry chemistry can fully account for observed perturbations to HOx partitioning, suggesting unknown additional chemical processes may be important in this unique environment, or that our understanding of coupled NOx-HOx−Bry chemistry above sunlit polar snow is incomplete. Rapid transport from the North Atlantic marine boundary layer occasionally caused enhanced BrO at Summit (just two such events observed during the 12 weeks of sampling over the two seasons). In general observed reactive bromine was linked to activation of bromide (Br−) in, and release of reactive bromine from, the snowpack. A coupled snow-atmosphere one-dimensional model that assumed snow photochemistry as the only source successfully simulated observed NO and BrO at Summit during a three day interval when winds were weak (transport not a factor). The source of Br− in surface and near surface snow at Summit is not entirely clear, but concentrations were observed to increase when stronger vertical mixing brought free tropospheric air to the surface. Reactive Bry mixing ratios above the snow often increased in the day or two following increases in snow concentration, but this response was not consistent. On seasonal time scales concentrations of Br− in snow and reactive bromine in the air were directly related.

scholarly journals Effects of temperature and other atmospheric conditions on long-term gaseous mercury observations in the Arctic

2009 ◽  
Vol 9 (6) ◽  
pp. 27167-27194
Author(s):  
A. S. Cole ◽  
A. Steffen
Keyword(s):  
Polar Vortex ◽  
Elemental Mercury ◽  
Early Spring ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Atmospheric Conditions ◽  
Climate Data ◽  
Gaseous Elemental Mercury ◽  
Teleconnection Patterns ◽  
Kinetic Calculations

Abstract. Gaseous elemental mercury (GEM) measurements at Alert, Canada, from 1995 to 2007 were analyzed for statistical time trends and for correlations with meteorological and climate data. A significant decreasing trend in annual GEM concentration is reported at Alert, with an estimated slope of −0.0086 ng m−3 yr−1 (−0.6% yr−1) over this 13-year period. It is shown that there has been a shift in the month of minimum mean GEM concentration from May to April due to a change in the timing of springtime atmospheric mercury depletion events (AMDEs). These AMDEs are found to decrease with increasing local temperature within each month, both at Alert and at Amderma, Russia. These results agree with the temperature dependence suggested by previous experimental results and theoretical kinetic calculations and highlight the potential for changes in Arctic mercury chemistry with climate. A correlation between total monthly AMDEs at Alert and the Polar/Eurasian Teleconnection Index was observed only in March, perhaps due to higher GEM inputs in early spring in those years with a weak polar vortex. A correlation of AMDEs at Alert with wind direction supports the origin of mercury depletion events over the Arctic Ocean, in agreement with a previous trajectory study of ozone depletion events. Interannual variability in total monthly depletion event frequency at Alert does not appear to correlate significantly with total or first-year northern hemispheric sea ice area or with other major teleconnection patterns. Nor do AMDEs at either Alert or Amderma correlate with local wind speed, as might be expected if depletion events are sustained by stable, low-turbulence atmospheric conditions. The data presented here – both the change in timing of depletion events and their relationship with temperature – can be used as additional constraints to improve the ability of global models to predict the cycling and deposition of mercury in the Arctic.

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