Mercury cycling in the global marine environment

Mercury is a globally distributed contaminant that exists in the atmosphere in its elemental form as a stable monoatomic gas. Having a residence time of around one year in air allows it to be transported far from emission sources and end up in polar ecosystems. Gaseous elemental mercury (GEM) can in air be oxidized by photo-induced processes which produce water soluble oxidized forms of mercury which are more easily deposited. Deposited mercury can in the environment be transformed to organic and bio-accumulating compounds which are neurotoxic, making mercury a global concern. <br /><br />Deposited oxidized mercury into the sea can be reduced back to the elemental form (GEM) and be re-emitted to air. This re-evasion constitutes of around 30% of the total emissions of mercury to air and originates from both natural and anthropogenic sources. Models have estimated that the yearly mercury emission from global sea surfaces is between 2000 and 3000 tonnes. The mercury flux rate at the interphase between air and water depends on the Henry´s law constant, the concentration gradient and the gas transfer velocity. How to properly account for weather parameters such as wind speed, and how to accurately adjust the flux model to mercury (originally developed for CO2) has been debated in the literature and have resulted in diverse results of mercury flux rates.  <br /><br />In this work, mercury has been measured in air and in seawater during several campaigns in Antarctica, the Mediterranean Sea, the west coast of Sweden, Northern Finland and in the Arctic. From measured concentrations of mercury, the mercury flux rates from the studied areas were calculated using the gas exchange model described in Johnson (2010). Large spatial and seasonal variations of measured mercury concentrations were found which resulted in similar variations in calculated flux rates. <br /><br />In Antarctica and the Arctic, high concentrations of mercury were also measured in the sea ice environment. Seasonal variations in mercury concentrations were found and a correlation between solar radiation and the photo-production of elemental mercury in sea ice was discovered. The sea ice was suggested to affect the global marine cycling of mercury in several ways: acting as a cap preventing elemental mercury to evade from sea surfaces in Polar Regions, acting as barrier against direct atmospheric deposition and being a significant reservoir of mercury. <br /><br />Climate change will likely affect the cycling of mercury in global marine environments due to an increase in temperature, leading to enhanced mercury evasion, and diminishing and melting sea ice causing an increased input of mercury into polar oceans. Results presented in this thesis bring new insights about how mercury is cycling in the global marine environment and the new collected mercury data from remote and inaccessible areas are valuable for future modeling. However, more research is needed to further understand and quantify the accumulation of mercury in vulnerable marine ecosystems

Distribution of total mercury and methylated mercury species in Central Arctic Ocean water and ice

The central Arctic Ocean remains largely unexplored when it comes to the presence and cycling of mercury and its methylated forms including mono- and dimethylmercury (MMeHg and DMeHg, respectively). In this study, we quantified total Hg (HgT) and methylated Hg species in seawater, ice cores, snow, brine, and water from melt ponds collected during the SWEDARCTIC 2016 expedition to the Amerasian and Eurasian side of the Lomonosov Ridge. In the water column, concentrations of HgT, MMeHg and DMeHg ranged from 0.089 to 1.5 pM, &lt;25 to 520 fM and from &lt;1.6 to 160 fM, respectively. HgT was enriched in surface waters while MMeHg and DMeHg were low at the surface (i.e. in the polar mixed layer) and enriched at a water depth of around 200–400 m. A 1:2 ratio of DMeHg to MMeHg was observed in the water column suggesting a lower ratio in the central parts of the Arctic Ocean than what has previously been reported from other parts of the Arctic Ocean. At the ice stations, average HgT ranged from 0.97 \ub1 1.2 pM in the ice cores to 27 \ub1 17 pM in melt pond waters and average MeHgT (total MeHg) from 28 \ub1 15 fM in brine to 130 \ub1 18 fM in melt pond water. The HgT observed in melt ponds and brine was an order of magnitude greater than HgT observed in surface waters and HgT in the upper part of the ice-cores was ~4–8 times higher HgT in comparison to lower layers. Our study suggests that ice may act as a source of HgT to surface waters but not to be a likely source of the methylated Hg forms. Unlike elemental Hg, DMeHg did not enrich in surface waters covered by ice. Concentrations of DMeHg observed in the ice cores and other samples collected from the ice stations were low, suggesting ice to not act as a source of DMeHg to the atmosphere nor to surface waters

First direct observation of sea salt aerosol production from blowing snow above sea ice

Two consecutive cruises in the Weddell Sea, Antarctica, in winter 2013 provided the first direct observations of sea salt aerosol (SSA) production from blowing snow above sea ice, thereby validating a model hypothesis to account for winter time SSA maxima in the Antarctic. Blowing or drifting snow often leads to increases in SSA during and after storms. For the first time it is shown that snow on sea ice is depleted in sulfate relative to sodium with respect to seawater. Similar depletion in bulk aerosol sized ∼0.3–6 µm above sea ice provided the evidence that most sea salt originated from snow on sea ice and not the open ocean or leads, e.g. &gt;90 % during the 8 June to 12 August 2013 period. A temporally very close association of snow and aerosol particle dynamics together with the long distance to the nearest open ocean further supports SSA originating from a local source. A mass budget estimate shows that snow on sea ice contains even at low salinity (&lt;0.1 psu) more than enough sea salt to account for observed increases in atmospheric SSA during storms if released by sublimation. Furthermore, snow on sea ice and blowing snow showed no or small depletion of bromide relative to sodium with respect to seawater, whereas aerosol was enriched at 2 m and depleted at 29 m, suggesting that significant bromine loss takes place in the aerosol phase further aloft and that SSA from blowing snow is a source of atmospheric reactive bromine, an important ozone sink, even during winter darkness. The relative increase in aerosol concentrations with wind speed was much larger above sea ice than above the open ocean, highlighting the importance of a sea ice source in winter and early spring for the aerosol burden above sea ice. Comparison of absolute increases in aerosol concentrations during storms suggests that to a first order corresponding aerosol fluxes above sea ice can rival those above the open ocean depending on particle size. Evaluation of the current model for SSA production from blowing snow showed that the parameterizations used can generally be applied to snow on sea ice. Snow salinity, a sensitive model parameter, depends to a first order on snowpack depth and therefore was higher above first-year sea ice (FYI) than above multi-year sea ice (MYI). Shifts in the ratio of FYI and MYI over time are therefore expected to change the seasonal SSA source flux and contribute to the variability of SSA in ice cores, which represents both an opportunity and a challenge for the quantitative interpretation of sea salt in ice cores as a proxy for sea ice. This research has been supported by the Natural Environment Research Council (UK) through the BLOWSEA project (grant nos. NE/J023051/1 and NE/J020303/1

Mercury cycling in the global marine environment

Mercury is a globally distributed contaminant that exists in the atmosphere in its elemental form as a stable monoatomic gas. Having a residence time of around one year in air allows it to be transported far from emission sources and end up in polar ecosystems. Gaseous elemental mercury (GEM) can in air be oxidized by photo-induced processes which produce water soluble oxidized forms of mercury which are more easily deposited. Deposited mercury can in the environment be transformed to organic and bio-accumulating compounds which are neurotoxic, making mercury a global concern. Deposited oxidized mercury into the sea can be reduced back to the elemental form (GEM) and be re-emitted to air. This re-evasion constitutes of around 30% of the total emissions of mercury to air and originates from both natural and anthropogenic sources. Models have estimated that the yearly mercury emission from global sea surfaces is between 2000 and 3000 tonnes. The mercury flux rate at the interphase between air and water depends on the Henry\ub4s law constant, the concentration gradient and the gas transfer velocity. How to properly account for weather parameters such as wind speed, and how to accurately adjust the flux model to mercury (originally developed for CO2) has been debated in the literature and have resulted in diverse results of mercury flux rates.\ua0 In this work, mercury has been measured in air and in seawater during several campaigns in Antarctica, the Mediterranean Sea, the west coast of Sweden, Northern Finland and in the Arctic. From measured concentrations of mercury, the mercury flux rates from the studied areas were calculated using the gas exchange model described in Johnson (2010). Large spatial and seasonal variations of measured mercury concentrations were found which resulted in similar variations in calculated flux rates. In Antarctica and the Arctic, high concentrations of mercury were also measured in the sea ice environment. Seasonal variations in mercury concentrations were found and a correlation between solar radiation and the photo-production of elemental mercury in sea ice was discovered. The sea ice was suggested to affect the global marine cycling of mercury in several ways: acting as a cap preventing elemental mercury to evade from sea surfaces in Polar Regions, acting as barrier against direct atmospheric deposition and being a significant reservoir of mercury. Climate change will likely affect the cycling of mercury in global marine environments due to an increase in temperature, leading to enhanced mercury evasion, and diminishing and melting sea ice causing an increased input of mercury into polar oceans. Results presented in this thesis bring new insights about how mercury is cycling in the global marine environment and the new collected mercury data from remote and inaccessible areas are valuable for future modeling. However, more research is needed to further understand and quantify the accumulation of mercury in vulnerable marine ecosystems

Seasonal Cycling of Mercury in the Antarctic Sea Ice Environment

Mercury is a globally distributed contaminant that exists in the atmosphere as a stable monoatomic gas. Having almost a year’s residence time in the air allows it to reach remote polar regions. Deposited airborne mercury can be transformed in the environment to the organic and bio-accumulating compound methyl mercury. Methyl mercury is neurotoxic and affects land living and marine animals all over the world. Springtime atmospheric mercury depletion events, first discovered in 1995 in the Arctic, occur when the return of sunlight induces the formation of halogen radicals that oxidize tropospheric elemental mercury. These spring events occurring in polar regions increase the net deposition of mercury into polar marine ecosystems. Some studies have been performed on the fate of mercury deposited onto snowpack but the transportation and transformation of mercury through and within snow and sea ice are still not fully understood. This thesis is based on data from three oceanographic expeditions to Antarctica (winter, spring and summer). Here unique seasonal data are presented for mercury species in air and elemental and total mercury concentrations in snow, sea ice, sea water and brine. Results presented in this thesis show that atmospheric mercury depletion events also occur over sea ice areas in the middle of the dark winter period. The dark depletions lead to an increased net deposition of mercury onto surface snow. Results also show that when approaching warmer and more sunlit seasons, the reduction of deposited oxidized mercury increases and this leads to more re-emission of elemental mercury back into the atmosphere. Melting sea ice also increases the leaching of mercury in snow and ice via run-off and via brine channels to the sea water under the ice floes. In this thesis it is also shown that the amount of solar radiation and overlaying snowpack affect the concentrations of elemental mercury in sea ice. This indicates that photo-reduction of mercury occurs within sea ice and may be important for mercury transportation and transformation within the polar marine environment. The new discoveries bring new insights to the global mercury cycle and the fate of mercury in polar regions. However, more research is needed to further understand and quantify the accumulation of mercury in polar ecosystems

Nedfall och avrinning av metaller, svavel och kväve i närheten av Rönnskärsverken från 1986/87 - 2017/18 - Årsrapport 2019

Sedan mitten av 1980-talet har IVL Svenska Miljöinstitutet AB utfört undersökningar av deposition och avrinning av bland annat svavel, kväve samt metaller i ett granskogsområde vid Holmsvattnet, ca 15 km SSV om Rönnskärsverken. I denna rapport jämförs resultaten från mätningarna 2017/18 vid Holmsvattnet med tidigare mätningar i området samt med mätningar vid andra närliggande stationer inom Krondroppsnätet. Syftet med mätningarna är att kvantifiera det atmosfäriska nedfallet samt beskriva förändringar i kemin i det avrinnande vattnet

Nedfall och avrinning av metaller, svavel och kväve i närheten av Rönnskärsverken från 1986/87 - 2019/20 : Årsrapport 2021

På uppdrag av Boliden Mineral AB genomför IVL Svenska Miljöinstitutet AB sedan mitten av 1980-talet undersökningar av deposition och avrinning av bland annat svavel, kväve samt metaller i ett granskogsområde vid Holmsvattnet, ca 15 km SSV om Rönnskärsverken.  Jämfört med tidigare år visade nedfallsmätningarna av metaller på öppet fält och som krondropp en ökning av vissa metaller under 2019/20. Blynedfallet på öppet fält var något högre än tidigare år, beroende på ett förhöjt nedfall under oktober och november. Orsaken till detta är oklar och kan bero på kontaminering men inga andra metaller var förhöjda på samma sätt under dessa båda månader. Även årsnedfallet av zink och nickel på öppet fält var högre 2019/20 jämfört med 2018/19. Kopparnedfallet var kraftigt förhöjt under maj-juli, viket bedöms bero på kontaminering av utrustningen varför dessa månaders kopparhalter istället har uppskattats utifrån interpolering och relativa jämförelser. Kopparnedfallet 2019/20 på öppet fält blev något högre jämfört med året innan medan nedfallet via krondropp var på en liknande nivå. Metallhalter i avrinning visar också på en ökning av koppar och bly, samt arsenik, under det hydrologiska året 2019/20 jämfört med året innan. Övriga uppmätta metaller visar istället en minskning från 2018/19 som då, troligtvis temporärt, visade förhöjda halter.  Under 2019/20 uppmättes vid många mätplatser i Sverige ett lågt svavelnedfall, så också vid Holmsvattnet och närliggande mätplatser. Svavelnedfallet (utan havssalt) har ofta varit högre vid Holmsvattnet jämfört med närliggande lokaler. Detta gällde också för 2019/20, då det totala svavelnedfallet vid Holmsvattnet var 1,3 kg/ha, vilket var cirka 40 % högre än vid två närliggande kustlokaler inom Krondroppsnätet. För hela Sverige uppmättes det högsta svavelnedfallet i krondroppet under 2019/20 i Blekinge med 4 kg/ha. Mätningarna tyder på en fortsatt betydande andel torrdeposition vid Holmsvattnet. Under 2019/20 var kvävenedfallet via nederbörden över öppet fält cirka 1,2 kg/ha, vilket var något lägre jämfört med de fyra närmast föregående åren. Även om man inkluderar torrdepositionen av kväve var det totala kvävenedfallet vid Holmsvattnet under den kritiska haltnivån på 5 kg/ha för påverkan på vegetationen i barrskogen. I denna rapport redovisas mätresultaten från det hydrologiska året 2019/20 vad gäller metaller, svavel och kväve i deposition och avrinning i närheten av Boliden Mineral AB:s smältverk vid Rönnskär. I rapporten redovisas även jämförelser mot tidigare års resultat, sedan mitten av 1980-talet, och mot andra relevanta lokaler med liknande mätningar inom Krondroppsnätet i norra Sverige. Syftet med mätningarna är att kvantifiera det atmosfäriska nedfallet samt beskriva förändringar i kemin i det avrinnande vattnet

Seasonal and spatial evasion of mercury from the western Mediterranean Sea

Continuous measurements of gaseous elemental mercury (GEM) in air and dissolved gaseous mercury (DGM) in surface seawater were performed during two oceanographic campaigns (Fenice 2011 (25/10-11/11) and Fenice 2012 (11-29/8)), carried out in the Tyrrhenian Sea (Fenice 211), western Mediterranean Sea and the Atlantic Ocean (Fenice 2012) as part of the GMOS project (Global Mercury Observation System). Measured GEM and DGM were used to estimate the air-sea exchange of elemental mercury by using a two-thin film gas exchange model. Measured GEM concentrations showed significantly higher values in fall (1.7 +/- 0.4 ng m(-3)) compared to summer (1.5 +/- 03 ng m(-3),

Nedfall och avrinning av metaller, svavel och kväve i närheten av Rönnskärsverken från 1986/87 - 2019/20 : Årsrapport 2021

På uppdrag av Boliden Mineral AB genomför IVL Svenska Miljöinstitutet AB sedan mitten av 1980-talet undersökningar av deposition och avrinning av bland annat svavel, kväve samt metaller i ett granskogsområde vid Holmsvattnet, ca 15 km SSV om Rönnskärsverken.  Jämfört med tidigare år visade nedfallsmätningarna av metaller på öppet fält och som krondropp en ökning av vissa metaller under 2019/20. Blynedfallet på öppet fält var något högre än tidigare år, beroende på ett förhöjt nedfall under oktober och november. Orsaken till detta är oklar och kan bero på kontaminering men inga andra metaller var förhöjda på samma sätt under dessa båda månader. Även årsnedfallet av zink och nickel på öppet fält var högre 2019/20 jämfört med 2018/19. Kopparnedfallet var kraftigt förhöjt under maj-juli, viket bedöms bero på kontaminering av utrustningen varför dessa månaders kopparhalter istället har uppskattats utifrån interpolering och relativa jämförelser. Kopparnedfallet 2019/20 på öppet fält blev något högre jämfört med året innan medan nedfallet via krondropp var på en liknande nivå. Metallhalter i avrinning visar också på en ökning av koppar och bly, samt arsenik, under det hydrologiska året 2019/20 jämfört med året innan. Övriga uppmätta metaller visar istället en minskning från 2018/19 som då, troligtvis temporärt, visade förhöjda halter.  Under 2019/20 uppmättes vid många mätplatser i Sverige ett lågt svavelnedfall, så också vid Holmsvattnet och närliggande mätplatser. Svavelnedfallet (utan havssalt) har ofta varit högre vid Holmsvattnet jämfört med närliggande lokaler. Detta gällde också för 2019/20, då det totala svavelnedfallet vid Holmsvattnet var 1,3 kg/ha, vilket var cirka 40 % högre än vid två närliggande kustlokaler inom Krondroppsnätet. För hela Sverige uppmättes det högsta svavelnedfallet i krondroppet under 2019/20 i Blekinge med 4 kg/ha. Mätningarna tyder på en fortsatt betydande andel torrdeposition vid Holmsvattnet. Under 2019/20 var kvävenedfallet via nederbörden över öppet fält cirka 1,2 kg/ha, vilket var något lägre jämfört med de fyra närmast föregående åren. Även om man inkluderar torrdepositionen av kväve var det totala kvävenedfallet vid Holmsvattnet under den kritiska haltnivån på 5 kg/ha för påverkan på vegetationen i barrskogen. I denna rapport redovisas mätresultaten från det hydrologiska året 2019/20 vad gäller metaller, svavel och kväve i deposition och avrinning i närheten av Boliden Mineral AB:s smältverk vid Rönnskär. I rapporten redovisas även jämförelser mot tidigare års resultat, sedan mitten av 1980-talet, och mot andra relevanta lokaler med liknande mätningar inom Krondroppsnätet i norra Sverige. Syftet med mätningarna är att kvantifiera det atmosfäriska nedfallet samt beskriva förändringar i kemin i det avrinnande vattnet