| 1. |
- Bergman, Inger, et al.
(författare)
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The influence of sulphate deposition on the seasonal variation of peat pore water methyl Hg in a boreal mire
- 2012
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:9, s. e45547-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we investigate the hypothesis that long-term sulphate (SO42-) deposition has made peatlands a larger source of methyl mercury (MeHg) to remote boreal lakes. This was done on experimental plots at a boreal, low sedge mire where the effect of long-term addition of SO42- on peat pore water MeHg concentrations was observed weekly throughout the snow-free portion of 1999. The additions of SO42- started in 1995. The seasonal mean of the pore water MeHg concentrations on the plots with 17 kg ha(-1) yr(-1) of sulphur (S) addition (1.3 +/- 0.08 ng L-1, SE; n=44) was significantly (p<0.0001) higher than the mean MeHg concentration on the plots with 3 kg ha(-1) yr(-1) of ambient S deposition (0.6 +/- 0.02 ng L-1, SE; n=44). The temporal variation in pore water MeHg concentrations during the snow free season was larger in the S-addition plots, with an amplitude of >2 ng L-1 compared to +/-0.5 ng L-1 in the ambient S deposition plots. The concentrations of pore water MeHg in the S-addition plots were positively correlated (r(2)=0.21; p=0.001) to the groundwater level, with the lowest concentrations of MeHg during the period with the lowest groundwater levels. The pore water MeHg concentrations were not correlated to total Hg, DOC concentration or pH. The results from this study indicate that the persistently higher pore water concentrations of MeHg in the S-addition plots are caused by the long-term additions of SO42- to the mire surface. Since these waters are an important source of runoff, the results support the hypothesis that SO42- deposition has increased the contribution of peatlands to MeHg in downstream aquatic systems. This would mean that the increased deposition of SO42- in acid rain has contributed to the modern increase in the MeHg burdens of remote lakes hydrologically connected to peatlands.
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| 2. |
- Bishop, Kevin, et al.
(författare)
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The Effects of Forestry on Hg Bioaccumulation in Nemoral/Boreal Waters and Recommendations for Good Silvicultural Practice
- 2009
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Ingår i: Ambio. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 38:7, s. 373-380
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Tidskriftsartikel (refereegranskat)abstract
- Mercury (Hg) levels are alarmingly high in fish from lakes across Fennoscandia and northern North America. The few published studies on the ways in which silviculture practices influence this problem indicate that forest operations increase Hg in downstream aquatic ecosystems. From these studies, we estimate that between one-tenth and one-quarter of the Hg in the fish of high-latitude, managed forest landscapes can be attributed to harvesting. Forestry, however, did not create the elevated Hg levels in the soils, and waterborne Hg/MeHg concentrations downstream from harvested areas are similar to those from wetlands. Given the current understanding of the way in which silviculture impacts Hg cycling, most of the recommendations for good forest practice in Sweden appear to be appropriate for high-latitude regions, e.g., leaving riparian buffer zones, as well as reducing disturbance at stream crossings and in moist areas. The recommendation to restore wetlands and reduce drainage, however, will likely increase Hg/MeHg loadings to aquatic ecosystems
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| 3. |
- Fritsche, Johannes, et al.
(författare)
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Evasion of Elemental Mercury from a Boreal Peat land Suppressed by Long-Term Sulfate Addition
- 2014
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Ingår i: ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS. - : American Chemical Society (ACS). - 2328-8930. ; 1:10, s. 421-425
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the evasion of TGM (total gaseous mercury) from experimental plots on a boreal peatland that had been exposed for 15 years to different combinations of atmospheric sulfur (5) and nitrogen (N) deposition as well as greenhouse treatments simulating climate change. Shaded dynamic flux chamber measurements during the summer in 2009 showed emission of TGM to the atmosphere from most of the treated plots (0.7 +/- 0.94 ng m(-2) h(-1)). However, TGM exchange rates were significantly lower, occasionally indicating Hg uptake, on plots subjected to S addition at rates of 20 kg ha(-1) year(-1). Enhanced nitrogen deposition and greenhouse treatment had no significant effect on TGM fluxes. We hypothesize that the lower Hg evasion from the sulfur-treated plots is related to either earlier Hg evasion or Hg binding to S in organic matter, making, Hg less susceptible to volatilization and more prone to transport in runoff.
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| 4. |
- Hansson, Katarina, et al.
(författare)
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Näringsbelastningen på Östersjön och Västerhavet 2017 : Sveriges underlag till HELCOM:s sjunde Pollution Load Compilation
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Havs- och vattenmyndigheten har gett SMED i uppdrag att genomföra beräkningar av kväve- och fosforbelastning från olika källor för år 2017 till sjöar, vattendrag och havet för hela Sverige. Syftet är att ge underlag till Sveriges rapportering till HELCOM PLC7 samt till vattenförvaltningens arbete i Sverige. Denna rapport, tillsammans med underlagsrapporter, redovisar resultat, underlagsdata, och beräkningsmetoder på detaljnivå för att uppnå transparens och spårbarhet samt för att möjliggöra vidareanvändning i arbetet inom svensk vattenförvaltning.Beräkningarna genomfördes i så stor utsträckning som möjligt med den metodiken som togs fram inom föregående projekt (PLC6). Arbetet innebär att stora mängder data har bearbetats och beräknats för att ge heltäckande information för hela Sverige fördelat på cirka 24 500 vattenförekomstområden. Resultaten är tillgängliga för alla via webbverktyget Tekniskt Beräkningssystem Vatten (TBV, tbv.smhi.se). Resultaten presenteras som brutto- samt nettobelastning för varje näringskälla, fördelat på total, antropogen och bakgrundsbelastning. Bruttobelastning är den mängd näringsämnen som släpps ut vid källan till ett vattendrag eller sjö. Nettobelastning är den del av bruttobelastningen som når havet. Skillnaden mellan brutto- och nettobelastningen benämns retention. Jordbruks- och skogsmark är de två största källorna till den totala belastningen på havet (nettobelastning) för både kväve och fosfor, med 33 400 respektive 31 670 ton/år kväve, samt 1 010 respektive 870 ton/år fosfor år 2017. Tillsammans står dessa källor för cirka 60 % av den totala belastningen. Av den antropogena belastningen står jordbruket för den största andelen (19 470 ton/år kväve samt 710 ton/år fosfor), följt av utsläpp från avloppsreningsverk (14 050 ton/år kväve samt 230 ton/år fosfor). Belastningen från skogsmark ingår enbart i bakgrund och den antropogena belastningen från hyggen bidrar endast med 1 540 ton/år kväve och 20 ton/år fosfor.Bottenhavet, Egentliga Östersjön och Kattegatt är de bassänger som tar emot mest kväve av Sveriges totala belastning på havet (28 560 ton/år, 26 150 ton/år respektive 27 700 ton/år, vilket motsvarar cirka 25 % vardera). I Bottenhavet är dock en stor del av belastningen naturlig bakgrundsbelastning. Egentliga Östersjön och Kattegatt tar emot mest av Sveriges antropogena belastning av kväve, 30 % respektive 31 %. I jämförelse mellan vilka havsbassänger som är mest belastade av fosfor, så är det Bottenhavet som tar emot mest (1 040 ton/år eller 32 % av den totala belastningen). Strax under en fjärdedel av Sveriges totala belastning på havet, rinner till Egentliga Östersjön (790 ton/år) och omkring en femtedel belastar Bottenviken och Kattegatt (640 respektive 620 ton/år). Aktionsplanen för Östersjön (Baltic Sea Action Plan, BSAP) anger utsläppsmål för alla länder kring Östersjön, med syfte att nå ”God miljöstatus” i Östersjön och Kattegatt. För fosfor är målet uppnått i alla bassänger utom Egentliga Östersjön, där det är ett utmanande mål och det kommer att bli mycket svårt att minska fosforbelastningen under belastningstaket (308 ton/år). Det krävs omfattande åtgärder av de antropogena källorna, men dessutom så utgör bakgrundsbelastningen en betydande del av den totala belastningen. Total nettobelastning av fosfor till Egentliga Östersjön är 790 ton enligt dessa beräkningar, varav 230 ton är beräknat som bakgrundsbelastning. För att Egentliga Östersjön ska kunna uppnå god miljöstatus med avseende på övergödning kommer det även att behövas åtgärder i Östersjöns andra delbassänger. På grund av skillnader i metoder och indata, är det inte möjligt att direkt jämföra hur belastningen från diffusa källor har ändrats sedan PLC6 (2014). En metodikskillnad som särskilt bör noteras är beräkningen av bakgrundsbelastningen av fosfor från jordbruksmark. Beräkningsmetoden för bakgrunden har utvecklats mellan olika PLC-beräkningar, vilket också lett till starkt skiftande resultat för bakgrundsbelastningen. I PLC6-beräkningen blev bakgrundsbelastningen hög eftersom en förändring i modellen visade sig ha gett en förmodad alltför stor förlust av partikulärt fosfor. Detta har korrigerats i den senaste modellversionen (PLC6.5 och PLC7) vilket är en av anledningarna till att bakgrundsbelastningen är lägre i PLC7 än i PLC6. Det är dock viktigt att notera att bakgrundsberäkningen alltid kommer att vara osäker eftersom den dels i mycket stor utsträckning bygger på antaganden och eftersom det dels saknas mätdata för att jämföra beräkningsresultaten med.För att resultaten för de diffusa källorna ska vara jämförbara mellan åren krävs att det görs en omräkning, antingen med gamla PLC-data och med den nya metoden eller med nya data och med den gamla metoden. En sådan omräkning kan bringa klarhet i hur mycket av skillnaden i resultaten som beror av förfinade indata eller förbättrade metoder och hur mycket som beror på implementerade åtgärder för att minska belastningen. Belastningen från punktkällorna beräknas på samma sätt som i PLC6. Utsläppen till havet i PLC 7 (2017) från avloppsreningsverk är ungefär i samma storleksordning som i PLC 6 (år 2014) 230 respektive 240 ton fosfor samt 14 000 ton kväve (netto). Industrier har minskat sin belastning på havet och svarar 2017 för 210 ton fosfor samt 3 320 ton kväve, jämfört med 250 fosfor och 3 800 ton kväve år 2014.
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| 5. |
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| 6. |
- Jonsson, Sofi, et al.
(författare)
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Terrestrial discharges mediate trophic shifts and enhance methylmercury accumulation in estuarine biota
- 2017
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Ingår i: Science Advances. - : American association for the advancement of science. - 2375-2548. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- The input of mercury (Hg) to ecosystems is estimated to have increased two- to fivefold during the industrial era, and Hg accumulates in aquatic biota as neurotoxic methylmercury (MeHg). Escalating anthropogenic land use and climate change are expected to alter the input rates of terrestrial natural organic matter (NOM) and nutrients to aquatic ecosystems. For example, climate change has been projected to induce 10 to 50% runoff increases for large coastal regions globally. A major knowledge gap is the potential effects on MeHg exposure to biota following these ecosystem changes. We monitored the fate of five enriched Hg isotope tracers added to mesocosm scale estuarine model ecosystems subjected to varying loading rates of nutrients and terrestrial NOM. We demonstrate that increased terrestrial NOM input to the pelagic zone can enhance the MeHg bioaccumulation factor in zooplankton by a factor of 2 to 7 by inducing a shift in the pelagic food web from autotrophic to heterotrophic. The terrestrial NOM input also enhanced the retention of MeHg in the water column by up to a factor of 2, resulting in further increased MeHg exposure to pelagic biota. Using mercury mass balance calculations, we predict that MeHg concentration in zooplankton can increase by a factor of 3 to 6 in coastal areas following scenarios with 15 to 30% increased terrestrial runoff. The results demonstrate the importance of incorporating the impact of climate-induced changes in food web structure on MeHg bioaccumulation in future biogeochemical cycling models and risk assessments of Hg.
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| 7. |
- Osterwalder, S., et al.
(författare)
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Comparative study of elemental mercury flux measurement techniques over a Fennoscandian boreal peatland
- 2018
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Ingår i: Atmospheric Environment. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1352-2310 .- 1873-2844. ; 172, s. 16-25
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Tidskriftsartikel (refereegranskat)abstract
- Quantitative estimates of the land-atmosphere exchange of gaseous elemental mercury (GEM) are biased by the measurement technique employed, because no standard method or scale in space and time are agreed upon. Here we present concurrent GEM exchange measurements over a boreal peatland using a novel relaxed eddy accumulation (REA) system, a rectangular Teflon (R) dynamic flux chamber (DFC) and a DFC designed according to aerodynamic considerations (Aero-DFC). During four consecutive days the DFCs were placed alternately on two measurement plots in every cardinal direction around the REA sampling mast. Spatial heterogeneity in peat surface characteristics (0-34 cm) was identified by measuring total mercury in eight peat cores (57 +/- 8 ng g(-1), average SE), vascular plant coverage (32-52%), water table level (4.5-14.1 cm) and dissolved gaseous elemental mercury concentrations (28-51 pg L-1) in the peat water. The GEM fluxes measured by the DFCs showed a distinct diel pattern, but no spatial difference in the average fluxes was detected (ANOVA, alpha = 0.05). Even though the correlation between the Teflon DFC and Aero-DFC was significant (r = 0.76, p < 0.05) the cumulative flux of the Aero-DFC was a factor of three larger. The average flux of the Aero-DFC (1.9 ng m(-2) h(-1)) and REA (2 ng m(-2) h(-1)) were in good agreement. The results indicate that the novel REA design is in agreement for cumulative flux estimates with the Aero-DFC, which incorporates the effect of atmospheric turbulence. The comparison was performed over a fetch with spatially rather homogenous GEM flux dynamics under fairly consistent weather conditions, minimizing the effect of weather influence on the data from the three measurement systems. However, in complex biomes with heterogeneous surface characteristics where there can be large spatial variability in GEM gas exchange, the small footprint of chambers ( < 0.2 m(2)) makes for large coefficients of variation. Thus many chamber measurement replications are needed to establish a credible biome GEM flux estimate, even for a single point in time. Dynamic flux chambers will, however, be able to resolve systematic differences between small scale features, such as experimentally manipulated plots or small scale spatial heterogeneity.
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| 8. |
- Osterwalder, Stefan, et al.
(författare)
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Mercury evasion from a boreal peatland shortens the timeline for recovery from legacy pollution
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands are a major source of methylmercury that contaminates downstream aquatic food webs. The large store of mercury (Hg) in peatlands could be a source of Hg for over a century even if deposition is dramatically reduced. However, the reliability of Hg mass balances can be questioned due to missing long-term land-atmosphere flux measurements. We used a novel micrometeorological system for continuous measurement of Hg peatland-atmosphere exchange to derive the first annual Hg budget for a peatland. The evasion of Hg (9.4 mu g m(-2) yr(-1)) over the course of a year was seven times greater than stream Hg export, and over two times greater than wet bulk deposition to the boreal peatland. Measurements of dissolved gaseous Hg in the peat pore water also indicate Hg evasion. The net efflux may result from recent declines in atmospheric Hg concentrations that have turned the peatland from a net sink into a source of atmospheric Hg. This net Hg loss suggests that open boreal peatlands and downstream ecosystems can recover more rapidly from past atmospheric Hg deposition than previously assumed. This has important implications for future levels of methylmercury in boreal freshwater fish and the estimation of historical Hg accumulation rates from peat profiles.
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| 9. |
- Wang, Baolin, et al.
(författare)
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Biogeochemical influences on net methylmercury formation proxies along a peatland chronosequence
- 2021
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier. - 0016-7037 .- 1872-9533 .- 0046-564X. ; 308, s. 188-203
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Tidskriftsartikel (refereegranskat)abstract
- A geographically constrained chronosequence of peatlands divided into three age classes (young, intermediate and old) was used to explore the role of biogeochemical influences, including electron donors and acceptors as well as chemical speciation of inorganic mercury (Hg(II)), on net formation of methylmercury (MeHg) as approximated by the fraction of MeHg to total mercury (THg) in the peat soil. We hypothesized that removing vascular plants would reduce availability of electron donors and thus net MeHg formation. However, we found no effect of the vascular plant removal. The sum of the potential electron donors (acetate, lactate, propionate and oxalate), the electron donation proxy organic C/Organic N, and the potential electron acceptors (Fe(III), Mn and sulfate) in porewater all showed significant correlations with the net MeHg formation proxies in peat soil (MeHg concentration and %MeHg of THg). Thus differences in both electron donor and acceptor availability may be contributing to the pattern of net MeHg formation along the chronosequence. In contrast, Hg(II) concentrations in peat porewater showed small differences along the gradient. A chemical speciation model successfully predicted the solubility of Hg and MeHg in the porewater. The modeling pointed to an enhanced concentration of Hg-polysulfide species in the younger peatlands as a potential factor behind increased Hg(II) solubility and methylation in the more nutrient-rich peatlands. This work contributes to the understanding of Hg and MeHg cycling in peatlands which can help guide mitigation measures to reduce aquatic MeHg biomagnification in peatland dominated landscapes.
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| 10. |
- Wang, Baolin, et al.
(författare)
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Opposing spatial trends in methylmercury and total mercury along a peatland chronosequence trophic gradient
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 718
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Tidskriftsartikel (refereegranskat)abstract
- Peatlands are abundant elements of boreal landscapes where inorganic mercury (IHg) can be transformed into bioaccumulating and highly toxic methylmercury (MeHg). We studied fifteen peatlands divided into three age lasses (young, intermediate and old) along a geographically constrained chronosequence to determine the role of biogeochemical factors and nutrient availability in controlling the formation of MeHg. In the 10 cm soil layer just below the average annual growing season water table, concentrations of MeHg and %MeHg (of total Hg) were higher in younger, more mesotrophic peatlands than in older, more oligotrophic peatlands. In contrast, total mercury (THg) concentrations were higher in the older peatlands. Partial least squares (PLS) analysis indicates that the net MeHg production was positively correlated to trophic demands of vegetation and an increased availability of potential electron acceptors and donors for Hg methylating microorganisms. An important question for further studies will be to elucidate why there is less THg in the younger peatlands compared to the older peatlands, even though the age of the superficial peat itself is similar for all sites. We hypothesize that ecosystem features which enhance microbial processes involved in Hg methylation also promote Hg reduction that makes previously deposited Hg more available for evasion back to the atmosphere.
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