Atmospheric Environment (v.39, #39)

7th International Conference on Mercury as a Global Pollutant by Ralf Ebinghaus; Nicola Pirrone; Steve Lindberg (7449-7450).

Emissions, dispersion and human exposure of mercury from a Swedish chlor-alkali plant by I. Wängberg; L. Barregard; G. Sällsten; M. Haeger-Eugensson; J. Munthe; J. Sommar (7451-7458).
Mercury in air near a mercury cell chlor-alkali plant in Sweden has been measured within the EU-project EMECAP. Based on the measurements and modelling the annual distributions of GEM and RGM have been calculated for the local area around the plant. The average concentration of GEM in residential areas near the plant was found to be 1–3.5 ng m−3 higher in comparison to the background concentration in this part of Sweden. The emission of RGM (0.55 kg year–1) results in elevated RGM concentrations close to the plant. The greatest impact on the local area is due to wet deposition of RGM. However, only a small fraction (0.4%) of all mercury being emitted was found to be deposited in the local area. No impact on urinary mercury could be demonstrated in the population living close to the plant.
Keywords: Chlor-alkali industry; Emission of elemental and reactive gaseous mercury; Mercury deposition; Urinary mercury;

Mercury emission to atmosphere from Lanmuchang Hg–Tl mining area, Southwestern Guizhou, China by Shaofeng Wang; Xinbin Feng; Guangle Qiu; Zhongqing Wei; Tangfu Xiao (7459-7473).
In situ mercury emission fluxes from soil in Lanmuchang Hg–Tl mining area, southwestern Guizhou, China, were measured using dynamic flux chamber (DFC) method in December 2002 and May 2003, respectively. Huge mercury emission fluxes from soil were obtained in the mining area, ranging from −623 to 10 544 ng m−2  h−1 ( n = 92 ) with the maximal mean Hg flux of 2283±2434 ng m−2  h−1. Meanwhile, highly elevated total gaseous mercury (TGM) concentrations in the ambient air observed during the sampling periods varied from 35.2±26.1 ng m−3 (7.9–353.8 ng m−3, n = 532 ) in cold season to 111.2 ± 91.8 ng m - 3 ( 12.7 – 468.0 ng m - 3 , n = 903 ) in the warm season, respectively. The correlations between mercury emission fluxes and environmental parameters, such as solar radiation, temperature, TGM concentration in air, relative humidity and soil Hg concentration are studied. The strong Hg emission fluxes resulted in the elevated TGM concentrations in the ambient air in the study area. We acquired a significant Log–Log correlation between the ratio of average Hg flux and average solar radiation and the soil Hg concentrations at all sampling sites in warm and cold seasons. Within the Langmuchang Hg–Tl mining area with a total area of ∼2.9 km2, the annual Hg emission rate is calculated to be ∼3.54 kg Hg, which is a strong mercury emission source to the local ambient air.
Keywords: Atmosphere; Hg emission fluxes; Naturally Hg enriched area; Lanmuchang Hg–Tl mine;

Elemental mercury emissions from chlor-alkali plants measured by lidar techniques by Rasmus Grönlund; Mikael Sjöholm; Petter Weibring; Hans Edner; Sune Svanberg (7474-7480).
Differential absorption lidar (DIAL) techniques have been utilized to measure elemental gaseous mercury fluxes from mercury cell chlor-alkali (MCCA) plants as a part of the European Union funded European mercury emissions from chlor-alkali plants (EMECAP) project. Three plants have been selected as study objects and a total of six measurement campaigns have been performed, one intercalibration campaign and five flux evaluation campaigns, in both winter and summer. The measurements were carried out using the Swedish optical parametric oscillator- (OPO) based mobile lidar system developed at Lund Institute of Technology. The study shows large differences in the mercury emissions measured in winter or summer and at the different plants. The average values for the campaigns ranged from 6 g h−1 in the winter campaign at the Swedish plant to 54 g h−1 in the summer campaign at the Italian plant.
Keywords: DIAL; Atmospheric mercury flux; EMECAP; Chlor-alkali plant; OPO;

An intensive field study quantifying total gaseous mercury (TGM) and mercury speciation fluxes in a wetland ecosystem (Bay St. François wetlands, Québec, Canada) was conducted in summer 2003. This study is one of the first attempts to design and develop an innovative approach—dynamic flux bag (DFB) technique to measure in situ mercury air–vegetation exchange with a monoculture of river bulrush (Scirpus fluviatilis). Air–vegetation flux measurements were conducted under dry condition at site 1 and flood condition at site 2. TGM fluxes fluctuated from −0.91 to 0.64 ng/m2 (leaf area)/h with an average value of –0.26±0.28 ng/m2 (leaf area)/h at site 1 and ranged from −0.98 to 0.08 ng/m2 (leaf area)/h with a mean flux of −0.33±0.24 ng/m2 (leaf area)/h at site 2 (positive sign means volatilization, and negative sign indicates deposition). The data indicated that TGM air–vegetation exchange is bidirectional. However, the net flux is primarily featured by dry deposition of TGM from atmosphere to the vegetation. In mercury speciation study using the DFB approach, particulate mercury (PM) and reactive gaseous mercury (RGM) represented less than 1% of total mercury. Ambient ozone concentrations had significant influences on RGM concentrations (r=0.54, p<0.05), implicating oxidation of gaseous elemental mercury (GEM) by ozone to form RGM. A discussion about the similarities and discrepancies between the DFB and other approaches (dynamic flux chamber and modified Bowen ratio) is presented. During the course of this study, some operational effects associated with the bag design, mainly the emergence of condensation within the bag, were encountered. Several improvements relating to the DFB design were recommended. Upon improvement, the DFB method could be one of the most promising techniques to study the role of a single plant in air–vegetation exchange of mercury.
Keywords: Air–vegetation exchange; Mercury speciation; Wetlands; Dynamic flux bag;

Increases in mercury volatilization from naturally enriched soils due to precipitation events have been observed in the field [Lindberg et al., 1999. Journal of Geophysical Research 104(D17), 21879–21888; Poissant et al., 1999. Journal of Geophysical Research 104(D17), 21845–21857] and indicate that further research on the exact mechanisms responsible for the increased fluxes are required. In this research, the effects of precipitation on Hg fluxes are simulated in a controlled laboratory experiment using a dynamic flux chamber system coupled with an internal precipitation generator and soil lysimeter. The experimental results indicate a sharp and rapid spike in the Hg(0) flux during the precipitation event which is due, in part, to the physical displacement of the Hg-containing interstitial soil air by the infiltrating rain water. After the precipitation event, the soil moisture prior to the event plays an important role in the Hg(0) emissions. When the soil is initially fairly dry (5–6 vol%), an enhancement in Hg(0) flux on the order of 12–16 times is observed after the precipitation event. However, when the soil is initially relatively moist (>15 vol%), no enhancement in the Hg(0) flux after the precipitation event is observed. This enhancement in the Hg(0) flux is well-correlated to the soil moisture before a rain event using a decaying exponential function.
Keywords: Gaseous elemental mercury; Dynamic flux chamber; Soil mercury flux; Precipitation effect;

The influence of ozone on atmospheric emissions of gaseous elemental mercury and reactive gaseous mercury from substrates by Mark A. Engle; Mae Sexauer Gustin; Steve E. Lindberg; Alan W. Gertler; Parisa A. Ariya (7506-7517).
Experiments were performed to investigate the effect of ozone (O3) on mercury (Hg) emission from a variety of Hg-bearing substrates. Substrates with Hg(II) as the dominant Hg phase exhibited a 1.7 to 51-fold increase in elemental Hg (Hgo) flux and a 1.3 to 8.6-fold increase in reactive gaseous mercury (RGM) flux in the presence of O3-enriched clean (50 ppb O3; 8 substrates) and ambient air (up to ∼70 ppb O3; 6 substrates), relative to clean air (oxidant and Hg free air). In contrast, Hgo fluxes from two artificially Hgo-amended substrates decreased by more than 75% during exposure to O3-enriched clean air relative to clean air. Reactive gaseous mercury emissions from Hgo-amended substrates increased immediately after exposure to O3 but then decreased rapidly. These experimental results demonstrate that O3 is very important in controlling Hg emissions from substrates. The chemical mechanisms that produced these trends are not known but potentially involve heterogenous reactions between O3, the substrate, and Hg. Our experiments suggest they are not homogenous gas-phase reactions. Comparison of the influence of O3 versus light on increasing Hgo emissions from dry Hg(II)-bearing substrates demonstrated that they have a similar amount of influence although O3 appeared to be slightly more dominant. Experiments using water-saturated substrates showed that the presence of high-substrate moisture content minimizes reactions between atmospheric O3 and substrate-bound Hg. Using conservative calculations developed in this paper, we conclude that because O3 concentrations have roughly doubled in the last 100 years, this could have increased Hgo emissions from terrestrial substrates by 65–72%.
Keywords: Mercury; Air-surface exchange; Natural mercury sources; Tropospheric ozone; Mercury soil emissions;

An investigation of air/surface exchange of mercury, performed at the Negro River Basin, (Amazonian region) in January 2003 and January 2004, is presented. Five sites were investigated: a flooding primary forest, a non-flooding primary forest and three deforested areas. The fluxes were estimated by using a dynamic flux chamber with sampling times varying between 6 and 12 h. The average mercury flux in deforested sites (13.7±10.3 pmol m−2  h−1) was significantly higher than in forest sites (0.1±1.8 pmol m−2  h−1). Our results showed that deforestation could be responsible for significantly increasing soil Hg emissions, mainly because of the high soil temperatures reached in deforested sites. Atmospheric gaseous mercury concentrations were generally low when compared with background areas from the Northern hemisphere. The average atmospheric Hg concentrations were 1.4±0.9 and 0.4±0.2 ng m−3 for forest and deforested sites, respectively.
Keywords: Mercury fluxes; Atmosphere–soil exchange; Flux chamber; Soil temperature;

Development of a processor in BEIS3 for estimating vegetative mercury emission in the continental United States by Che-Jen Lin; Steve E. Lindberg; Thomas C. Ho; Carey Jang (7529-7540).
We have developed a regression-based processor for estimating vegetative mercury emission within the framework of Biogenic Emission Inventory System Version 3.11 (BEIS3 V3.11). In this development, we incorporated the 230 categories of USGS landcover data to generate the vegetation-specific mercury emission in a 36-km Lambert Conformal model grid covering the continental United States (CONUS). The surface temperature and cloud-corrected solar radiation from a Mesoscale Meteorological model (MM5) were retrieved and used for calculating the diurnal variation. The implemented emission factors were either evaluated from the measured mercury flux data for selected tree species, wetland and water, or assumed for the tree species without available flux data. Annual simulations using the 2001 USEPA MM5 data were performed to investigate the seasonal emission variation. From our sensitivity analysis using three sets of emission factors, we estimated that the vegetative mercury emission in the CONUS domain ranges from a lower limit of 31 ton yr−1 to an upper limit of 140 ton yr−1, with the best estimate at 44 ton yr−1. The modeled vegetative emission was mainly contributed from southeast US. Using the best estimate data, it is shown that mercury emission from vegetation is comparable to that from anthropogenic sources in summer (nearly half of the total emission). However, the vegetative emission decreases greatly in winter, leaving anthropogenic sources as the major emission source (>90% in winter months). Modeling assessment indicates that including vegetative emission (44 ton yr−1) can force an increase of ambient mercury concentration of up to 0.2 ng m−3 in summer midday, but has little impact on dry deposition of mercury. Additional emission factors can be implemented in the model once further mercury flux data become available.
Keywords: Mercury emission; Natural source; Anthropogenic source; Emission inventory estimates; BEIS3;

Dispersion of mercury in the atmosphere of the Northern Hemisphere is studied by means of atmospheric modelling. Mercury concentration in the ambient air and deposition levels are investigated as well as the intercontinental transport of mercury is assessed. It is demonstrated that the contribution of external anthropogenic and natural sources to mercury deposition to different continents varies from 30% to 70% of total value. Besides, about half the mercury deposition to such a remote region as the Arctic is due to the transport from anthropogenic emission sources. Thus, it could be concluded that the contribution of the intercontinental atmospheric transport of mercury is comparable with that of regional pollution even in industrially developed regions of the Northern Hemisphere.
Keywords: Atmospheric modelling; Mercury depositions; Intercontinental transport;

Monitoring of total gaseous mercury (TGM) concentrations has been carried out at Mace Head on the west coast of Ireland and at Zingst on the southern shore-line of the Baltic Sea. We have used the continuous measurements to assess long-term trends and seasonal variations of TGM concentrations over the same time period. Between 1998 and 2004 the annually averaged TGM concentrations measured at Mace Head (1.72 ng m−3) and Zingst (1.66 ng m−3) remained fairly stable. At both stations we measured higher TGM levels during winter months and lower concentrations during summer months. We also observed an unexpected West to East gradient and found that the overall mean Mace Head TGM concentration was 0.06 ng m−3 higher than those of Zingst. For the January to June period, the Mace Head TGM values (6-year mean=1.75 ng m−3) are significantly elevated compared to the Zingst results (6-year mean=1.64 ng m−3). Since no local anthropogenic mercury sources exist near the Mace Head station, enhanced emission from the sea appears to provide the most probable explanation for the observed differences. Multiple regression analysis with the atmospheric mercury concentrations measured at Zingst were made with selected meteorological and air quality parameters (wind component, dew point, dust and NOx concentrations). The short-term variation in the TGM concentrations at Zingst shows a strong positive correlation with weather conditions and selected air quality parameters, making TGM a usable tracer of air masses originating from different source regions.
Keywords: Mercury in ambient air; Long-term trends; Spatial distribution; Seasonal variations;

Methyl and total mercury in precipitation in the Great Lakes region by B.D. Hall; H. Manolopoulos; J.P. Hurley; J.J. Schauer; V.L. St. Louis; D. Kenski; J. Graydon; C.L. Babiarz; L.B. Cleckner; G.J. Keeler (7557-7569).
Methylmercury (MeHg) and total mercury (THg) concentrations were measured in precipitation collected from five US sites in the Great Lakes region: three sites on the southern shore of Lake Superior (Brule River, WI, Eagle Harbor, MI, and Tahquamenon Falls, MI), one at Isle Royale National Park (MI), and one in southern Wisconsin (Devil's Lake), between May 1997 and December 2003. MeHg and THg concentrations at these sites were compared to MeHg and THg concentrations in precipitation collected at the Experimental Lakes Area (ELA) in north-western Ontario, Canada. Detectable MeHg concentrations (>0.01 ng L−1) were found in the majority of rain and snow samples collected from all sites (range=0.01–0.85 ng L−1). In general, the lowest MeHg concentrations were observed in samples taken at Tahquamenon Falls and the ELA, and the highest MeHg concentrations in precipitation were observed in samples collected from Brule River and Eagle Harbor. Total Hg concentrations in precipitation were generally between 10 and 60 ng L−1, exceeding 60 ng L−1 in one precipitation event sampled from each of Brule River, Isle Royale, Tahquamenon Falls, and Devil's Lake. The proportion of THg that was MeHg (%MeHg), was less than 6% at all sites, with the exception of seven events at Tahquamenon Falls and two events at the ELA that were between 6% and 18% MeHg. Generally, the highest MeHg concentrations were found in low-volume precipitation events (<100 mL). At Tahquamenon Falls, meteorological analysis indicated that events with higher MeHg concentrations and %MeHg exceeding 6% were generally associated with lake effect precipitation and weak local winds.
Keywords: Methylmercury; Precipitation; Great Lakes; Meteorological analysis; Wisconsin; Michigan; Ontario; Lake Superior;

Current and past mercury distribution in air over the Idrija Hg mine region, Slovenia by Jože Kotnik; Milena Horvat; Tatjana Dizdarevič (7570-7579).
Mercury in air over the Idrija region, where the world's second largest mercury (Hg) mine is located, decreased significantly in the last decade, from more than 20,000 ng m−3 in the early 1970s to values below 100 ng m−3 in the 1980s, and finally reached a level of 10 ng m−3 or even lower at the summer of the year 2004.The air concentration of Hg was continuously monitored after closure of the Hg mine. Hg0 in air was mapped in November 2003 at over 100 locations in the Idrija region during a 3-day period under different weather conditions, and the concentrations found were between 2.5 to over 2000 ng m−3. The Hg concentration in air was mostly below 10 ng m−3. The highest values were observed in the near vicinity of the former smelting plant, as well under its chimney. Elevated concentrations were also observed at some other locations in Idrija town. Mercury evaporation from topsoil was measured continuously for a 24 h period at two heavily polluted locations in Idrija and 50 km downstream the River Idrijca at Bača pri Modreju. The average Hg concentration in air at Bača pri Modreju was 5.5 ng m−3, with an average Hg flux from soil to atmosphere of 34 ng m−2  h−1. At the site in Idrija the average Hg concentration in air was 11 ng m−3 with an average Hg flux from soil to the atmosphere of 84.4 ng m−2  h−1.
Keywords: Mercury; Air; Evasion; Flux chamber; Idrija;

Seasonal mercury concentrations measured in rural air in Southern Poland by Urszula Zielonka; Stanislaw Hlawiczka; Janina Fudala; Ingvar Wängberg; John Munthe (7580-7586).
The concentration of total atmospheric gaseous mercury (TGM) and total particulate mercury (TPM) have been measured during one summer campaign (19–29 August 2003) and one winter campaign (26 January–3 February 2004) at a rural site in Poland. Mercury deposition was also measured using bulk samplers. The measurement campaigns were performed in a typical agricultural area of Southern Poland where 85% of the houses use low capacity domestic heating units (DHUs) fuelled with hard coal during the cold season. An average TGM value of 1.63 ± 0.35 ng m - 3 was obtained in the summer campaign, whereas a 2.5 times higher TGM concentration was found during winter. The mean TPM concentration during summer was 0.11 ± 0.05 ng m - 3 while 10 times higher values were obtained during the winter campaign. The mercury deposition was also found to be much higher during winter in comparison to summer. The summer TGM values are at the same level as the annual average TGM at background locations in most West European countries including Scandinavia. The higher TGM values in winter are most likely due to the use of DHUs in the local area. However, both summer and winter TPM concentrations and mercury deposition fluxes are much higher than in most neighbouring West European countries. This probably reflects the regional use of coal combustion for electric energy production and in low-capacity DHUs.
Keywords: Total gaseous mercury; Total particulate mercury; Mercury bulk dry deposition; Coal combustion; Atmosphere;

Atmospheric mercury data for the Coquimbo region, Chile: influence of mineral deposits and metal recovery practices by Pablo Higueras; Roberto Oyarzun; Javier Lillo; Jorge Oyarzún; Hugo Maturana (7587-7596).
This work reports data of atmospheric mercury for northern Chile. The study was centered in the Coquimbo region, a realm rich in mineral deposits. Some of the mining districts have historic importance and have been exploited almost continuously since the Spanish colonial time (16–18th century). Two of these districts are particularly relevant: (1) Andacollo, initially exploited for gold, and then for copper and gold; and (2) Punitaqui, initially exploited for mercury, and then for copper and gold. The continuous mercury measurement procedures carried out during this survey, have proved to be an excellent tool to detect Hg signatures associated with the mining industrial activities. The combination of cumulative log-probability graphs and atmospheric mercury concentration profiles, allows clear differentiation between areas subjected to agriculture (2–3 ngHg m−3), from those in which mining and metal concentration activities take place (>10 ngHg m−3, most data well beyond this figure). Gold recovery involving milling and amalgamation appear as the most contaminant source of mercury, and yield concentrations in the order of 104–105  ngHg m−3 (Andacollo). Second in importance are the vein mercury deposits of Punitaqui, with concentrations above 100 ngHg m−3, whereas the flotation tailings of the district yield concentrations near to 100 ngHg m−3. The large and modern open pit operations of Andacollo (Carmen: Cu; Dayton: Au) do not show high concentrations of atmospheric mercury.
Keywords: Mercury; Atmosphere; Air geochemistry; Coquimbo; Chile;

Total and methyl mercury patterns in Arctic snow during springtime at Resolute, Nunavut, Canada by Nazafarin Lahoutifard; Melissa Sparling; David Lean (7597-7606).
Patterns of gaseous elemental mercury (GEM) were monitored at 20 and 150 cm above the snowpack near Resolute Bay, Cornwallis Island, Nunavut, Canada near the Upper Air Station of Environment Canada (74°42′N, 94°58′W) from 7 May (day 127) to 12 June (day 163) 2003. At this time of year there was 24 h daylight but still a strong diel change in solar radiation. Daily patterns of GEM-tracked solar radiation with a lag of about 2 h and the GEM gradient between these two heights showed the direction of flux. In addition to the previously established autocatalytic reactions involving halogens where reactive gaseous mercury and fine particulate mercury result in direct deposition to the snow, both diffusion to and volatilization from the snow occurred on a regular basis. Total mercury (THg) in the snowpack increased to near 30 ng L−1 following 8 d of atmospheric mercury depletion then decreased to values near 1 ng L−1. Losses from the snow could not be accounted for in melt water as stream runoff values were also low. In other words, most of the mercury associated with increased levels in snow was volatilized back to the atmosphere either directly from the snow or from the water surfaces. However, using accepted mass transport coefficients, the flux appeared low and other mechanisms are suggested. In contrast to THg, methyl mercury (MeHg) in the snow reached values near 140 pg L−1 but also declined to less than detection limit (10 pg L−1) with the onset of warmer temperatures. MeHg in stream runoff water was similar to maximal values seen in the snow. This observation is consistent with the view that MeHg came in the snowfall or was deposited to the snow pack rather than produced in the snow. In contrast, much of the THg associated with mercury depletion events was volatilized back to the atmosphere.
Keywords: Arctic; Gaseous elemental mercury; Methyl mercury; Air/snow mercury transport; Diel patterns; Solar radiation; Mercury pollution;

Measurements of atmospheric mercury species during an international study of mercury depletion events at Ny-Ålesund, Svalbard, spring 2003. How reproducible are our present methods? by Katrine Aspmo; Pierre-Alexis Gauchard; Alexandra Steffen; Christian Temme; Torunn Berg; Enno Bahlmann; Cathy Banic; Aurelien Dommergue; Ralf Ebinghaus; Christophe Ferrari; Nicola Pirrone; Francesca Sprovieri; Grethe Wibetoe (7607-7619).
Six groups participated in an international study of springtime atmospheric mercury depletion events (AMDEs) at Ny-Ålesund in the Norwegian Arctic during April and May 2003 with the aim to compare analytical methods for measurements of atmospheric mercury species and study the physical and chemical processes leading to AMDEs. Five groups participated in the method comparison that was conducted at three different locations within Ny-Ålesund. Various automated and manual instrumentation were used to sample, measure and compare gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and mercury associated with particles (Hg-P). The concentration of GEM was reproducible during background conditions. For the first time using ambient air, the statistics associated with round robin test procedures were applied. This was found to be an appropriate tool to investigate the reproducibility of GEM measurements in ambient air. The precision for each group measuring GEM concentrations was found to be consistently good (within 5%). Five AMDEs were recorded during the study. Using four different methods, including single and replicate samples, all groups recorded higher values of RGM and Hg-P during AMDEs. The results show that measuring comparable atmospheric mercury species at both the same and different locations (within the Ny-Ålesund area) is difficult. Not only do site location and site characteristics create challenges when trying to intercompare results but there are difficulties, as well, in obtaining comparable results with similar sampling and analysis methods. Nevertheless, with our current procedures for atmospheric mercury identification we can differentiate with certainty between “high” and “low” concentration values of RGM and Hg-P.
Keywords: Gaseous elemental mercury; Reactive gaseous mercury; Particle bound mercury; Intercomparison; Round robin test procedures; Arctic;

Study of the origin of atmospheric mercury depletion events recorded in Ny-Ålesund, Svalbard, spring 2003 by Pierre-Alexis Gauchard; Katrine Aspmo; Christian Temme; Alexandra Steffen; Christophe Ferrari; Torunn Berg; Johan Ström; Lars Kaleschke; Aurélien Dommergue; Enno Bahlmann; Olivier Magand; Frédéric Planchon; Ralf Ebinghaus; Cathy Banic; Sonia Nagorski; Patrick Baussand; Claude Boutron (7620-7632).
An international campaign involving six teams was organized in Ny-Ålesund, Svalbard, in order to understand better the origin of atmospheric mercury depletion events (AMDEs). Special emphasis was given to determining the source region of the observed events and the physical and chemical processes leading to AMDEs. Five AMDEs were recorded during a one-month field experiment (10 April–10 May, 2003). The different events presented various characteristics, especially in terms of mercury species formation, atmospheric particle variations and meteorological conditions. After careful examination of each event, we postulate that two were probably due to advection of already depleted air masses and three were a product of local or regional chemistry. The roles of different surfaces (frost flowers, snow, ice aerosol in clouds) involved in heterogeneous reactions leading to AMDEs are also discussed. We speculate that ice clouds may explain the particle variations observed during the three more local events.
Keywords: Atmospheric mercury depletion events; Mercury; Ozone; Particles; Transport;

Snow-to-air exchanges of mercury in an Arctic seasonal snow pack in Ny-Ålesund, Svalbard by Christophe P. Ferrari; Pierre-Alexis Gauchard; Katrine Aspmo; Aurélien Dommergue; Olivier Magand; Enno Bahlmann; Sonia Nagorski; Christian Temme; Ralf Ebinghaus; Alexandra Steffen; Cathy Banic; Torunn Berg; Frédéric Planchon; Carlo Barbante; Paolo Cescon; Claude F. Boutron (7633-7645).
The study of mercury (Hg) cycle in Arctic regions is a major subject of concern due to the dramatic increases of Hg concentrations in ecosystem in the last few decades. The causes of such increases are still in debate, and an important way to improve our knowledge on the subject is to study the exchanges of Hg between atmosphere and snow during springtime. We organized an international study from 10 April to 10 May 2003 in Ny-Ålesund, Svalbard, in order to assess these fluxes through measurements and derived calculations.Snow-to-air emission fluxes of Hg were measured using the flux chamber technique between ∼0 and 50 ng m−2  h−1. A peak in Gaseous Elemental Mercury (GEM) emission flux from the snow to the atmosphere has been measured just few hours after an Atmospheric Mercury Depletion Event (AMDE) recorded on 22 April 2004. Surprisingly, this peak in GEM emitted after this AMDE did not correspond to any increase in Hg concentration in snow surface. A peak in GEM flux after an AMDE was observed only for this single event but not for the four other AMDEs recorded during this spring period.In the snow pack which is seasonal and about 40 cm depth above permafrost, Hg is involved in both production and incorporation processes. The incorporation was evaluated to ∼5–40 pg m2  h. Outside of AMDE periods, Hg flux from the snow surface to the atmosphere was the consequence of GEM production in the air of snow and was about ∼15–50 ng m−2  h−1, with a contribution of deeper snow layers evaluated to ∼0.3–6.5 ng m−2  h−1. The major part of GEM production is then mainly a surface phenomenon. The internal production of GEM was largely increasing when snow temperatures were close to melting, indicating a chemical process occurring in the quasi-liquid layer at the surface of snow grains.
Keywords: Mercury; Snow; Exchange; Production; Incorporation; Quasi-liquid layer;

Atmospheric mercury behavior at different altitudes at Ny Alesund during Spring 2003 by F. Sprovieri; N. Pirrone; M.S. Landis; R.K. Stevens (7646-7656).
Intensive field measurements of atmospheric mercury and related species were carried out in Ny Alesund, Spitsbergen, during the spring of 2003 at two altitudes. Measurements were made at the Italian research station Dirigibile Italia (12 m a.s.l.) and on the top of Zeppelin Mountain at the Norwegian Research Station (474 m a.s.l.). Ambient concentrations of gaseous elemental mercury, divalent reactive gaseous mercury and particulate phase mercury were semi-continuously measured at both sites using an integrated Tekran system. Atmospheric elemental gaseous mercury depletion events (AMDEs) were observed at both locations, the lowest observed Hg0 concentration was 0.3 ng m−3. At sea level, mercury species concentrations following AMDEs were found to be higher and to exhibit larger variability in comparison to those observed at Zeppelin station.
Keywords: Mercury; Arctic; Reactive gaseous mercury; Zeppelin station; Depletion; Polar spring; Dirigibile italia; AMDEs;