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2014 | Brevia (Rome)

Dynamic modelling of the long term behaviour of cadmium, lead and mercury in Swiss forest soils using CHUM-AM.

Rieder S.R.; Tipping E.; Zimmermann S.; Graf-Pannatier E.; Waldner P.; Meili M.; Frey B.
2014 | Sci. Total Environ. | vol.468–469 (864-876)
hg , mercury

Impact of forestry on total and methyl-mercury in surface waters: distinguishing effects of logging and site preparation.

Eklöf, K.; Schelker, J.; Sørensen, R.; Meili, M.; Laudon, H.; von Brömssen, C.; Bishop, K.
2014 | Environ. Sci. Technol. | 48 (4690-4698)
hg , mercury

Half a century of changing mercury levels in Swedish freshwater fish

Åkerblom, S.; Bignert, A.; Meili, M.; Sonesten, L.; Sundbom, M.
2014 | Ambio | 43 (S91-103)
hg , mercury

The variability of mercury (Hg) levels in Swedish freshwater fish during almost 50 years was assessed based on a compilation of 44 927 observations from 2881 waters. To obtain comparable values, individual Hg concentrations in fish from any species and of any size were standardized to correspond to a 1-kg pike [median: 0.69 mg kg-1 wet weight, mean ± SD: 0.84 ± 0.67 mg kg-1]. The EU Environmental Quality Standard of 0.02 mg kg-1 was exceeded in all waters, while the FAO/WHO-based guideline for Hg levels in fish used for human consumption (0.5 mg kg-1) was exceeded in 52.5 % of Swedish waters after 2000. Different trend analysis approaches indicated an overall long-term decline of at least 20 % during 1965–2012, but trends did not follow any regionally consistent pattern. During the latest decade (2003–2012), however, a spatial gradient has emerged with decreasing trends predominating in southwestern Sweden.

Impact of stump harvest on run-off concentrations of total mercury and methylmercury.

Eklöf, K.; Meili, M.; Åkerblom, S.; von Brömssen, C.; Bishop, K.
2013 | For. Ecol. Manage. | 290 (83-94)
hg , mercury

Forest harvesting operations have been reported to increase the levels of both total mercury (THg) and methylmercury (MeHg) in runoff water and downstream biota. Mobilization of such harmful substances by logging may pose ecological risks that may be influenced further by site preparation and stump harvest. Stump harvest is currently being explored as a method to increase the supply of biofuels. In this catchment study we investigated the effects of stump harvest, in comparison with ordinary site-preparation, on the runoff concentrations of THg and MeHg as well as several other chemistry parameters. Both treatments were also compared with unharvested reference catchments. Water samples from watercourses draining these catchments were analyzed for various variables including THg, MeHg, total organic carbon, absorbance and total suspended solids. One year of pre-treatment data, starting when the treated areas were just logged, and 2 years of post-treatment data, after stump harvest or site-preparation, were collected with a sample frequency of twice a month.

The concentrations of THg and MeHg in the treated areas were decreasing after both stump harvest and site preparation relative to the reference catchment. Further, our results indicate that stump harvest has not caused increased concentrations of any of the studied parameters in relation to traditional site preparation. Two factors are proposed to be responsible for the lack of response to stump harvest and site preparation; (1) the areas are still undergoing recovery from the former logging which may have led to greater Hg export and/or (2) there is variability among sites in how they respond to forestry operations, depending on the biogeochemical and hydrological status of the area.

Although no forestry response caused by stump harvest or site preparation was found, we noted that the concentrations of both THg and especially MeHg were high (median THg: 4.5–10.4 ng L−1, median MeHg: 0.7–2.1 ng L−1) in all catchments both before and after treatment, compared to other studies. Variables indicating the organic carbon content were the ones most strongly correlated to the variation of both THg and MeHg in the PLS models based on the dataset from the whole sampling period and all catchments. The relatively high concentrations of THg and MeHg during the study period appeared to be more influenced by organic carbon, but also hydrology and temperature as well as possibly the initial logging rather than by the soil disturbance caused by either stump harvest or site preparation.

Comparison of levels and sources of lead in modern and ancient soils in Low Volga steppes.

Pampura, T.V.; Demkin, V.A.; Meili, M.; Kylander, M.E.; Holm, K.; Probst, A.
2013 | E3S Web of Conferences (EDP Sciences) | vol.1 (08002:1-3) | Report No: 08002

Eight boreal wetlands as sources and sinks for methyl mercury in relation to soil acidity, C/N ratio and small-scale flooding.

Tjerngren, I.; Meili, M.; Björn, E.; Skyllberg, U.
2012 | Environ. Sci. Technol. | 46 (8052-8060)
hg , mercury

Four years of catchment export and wetland input–output mass balances are reported for inorganic Hg (Hginorg), methyl mercury (MeHg), dissolved organic carbon (DOC), and sulfate in eight Swedish boreal wetlands. All wetlands had a history of artificial drainage and seven were subjected to small-scale flooding during the complete study period (two sites) or the two last years (five sites). We used an approach in which specific runoff data determined at hydrological stations situated at a distance from the studied sites were used in the calculation of water and element budgets. All wetlands except one were significant sinks for Hginorg. Seven wetlands were consistent sources of MeHg and one (an Alnus glutinosa swamp) was a significant sink. The pattern of MeHg yields was in good agreement with previously determined methylation and demethylation rates in the wetland soils of this study, with a maximum MeHg yield obtained in wetlands with an intermediate soil acidity (pH 5.0) and C/N ratio (20). We hypothesize that an increased nutrient status from poor to intermediate conditions promotes methylation over demethylation, whereas a further increase in nutrient status and trophy to meso- and eutrophic conditions promotes demethylation over methylation. Small-scale flooding showed no or moderate changes in MeHg yield, maintaining differences among wetlands related to nutrient status.

Forestry influence by stump harvest and site preparation on methylmercury, total mercury and other stream water chemistry parameters across a boreal landscape.

Eklöf, K.; Kraus, A.; Weyhenmeyer, G.A.; Meili, M.; Bishop, K.
2012 | Ecosystems | 15 (1308-1320)
hg , mercury

Forestry has been reported to cause elevated mercury (Hg) concentrations in runoff water. However, the degree to which forestry operations influence Hg in runoff varies among sites. A synoptic study, covering 54 catchments distributed all over Sweden, subjected to either stump harvest (SH), site preparation (SP) or no treatment (Ref), was undertaken to reveal the degree of forestry impact and causes of eventual variation. All streams were sampled twice, in autumn 2009 and summer 2010. There were no significant differences in total mercury (THg) and methylmercury (MeHg) concentrations between the three treatments in either 2009 or 2010. However, when pooling the treated catchments (that is, SH and SP) and taking catchment properties such as latitude into account, the treatment had a significant influence on the THg and MeHg concentrations. Although the treatment effect on THg and MeHg did not differ between SH and SP, the study did reveal significant forestry effects on potassium (K) and total nitrogen (TN) that were greater in the SH catchments and lower in the SP catchments. Partial least square (PLS) regressions indicated that organic matter was the most important variable influencing both the THg and MeHg concentrations. There were no significant differences between the treatment groups when comparing the ratios of THg/total organic carbon (TOC) and MeHg/TOC, suggesting that the high concentrations of THg and MeHg observed at some of the treated catchments are associated with increased concentrations of TOC rather than new methylation or increased mobilization caused by factors other than TOC.

Large geographical differences in the sensitivity of ice-covered lakes and rivers in the Northern Hemisphere to temperature changes.

Weyhenmeyer, G.A.; Livingstone, D.M.; Meili, M.; Jensen, O.; Benson, B.; Magnuson, J.J.
2011 | Glob. Change Biol. | 17 (1) (268-275)

Based on a unique dataset of more than 50 000 observations of ice phenology from 1213 lakes and 236 rivers in 12 different countries, we show that interannual variations in the timing of ice-on and ice-off on lakes and rivers are not equally pronounced over the entire Northern Hemisphere, but increase strongly towards geographical regions that experience only short periods during which the air temperature falls below 0 °C. We explain our observations by interannual fluctuation patterns of air temperature and suggest that lake and river ecosystems in such geographical regions are particularly vulnerable to global warming, as high interannual variability is known to have important ramifications for ecosystem structure and functioning. We estimate that the standard deviation of the duration of ice cover, viewed as a measure of interannual variability, exceeds 25 days for lakes and rivers located on 7% of the land area of the Northern Hemisphere. Such high variability might be an early warning signal for a critical transition from strictly dimictic, ice-covered systems to monomictic, open-water systems. Using the Global Lake and Wetland Database, we suggest that 3.7% of the world's lakes larger than 0.1 km2 are at high risk of becoming open-water systems in the near future, which will have immediate consequences for global biogeochemical cycles.

Sediment records of highly variable mercury inputs to mountain lakes in Patagonia during the past millennium.

Ribeiro Guevara, S.; Meili, M.; Rizzo, A.; Daga, R.; Arribére, M.
2010 | Atmos. Chem. Phys. | 10 (7) (3443-3453)
hg , mercury

High Hg levels in the pristine lacustrine ecosystems of the Nahuel Huapi National Park, a protected zone situated in the Andes of Northern Patagonia, Argentina, have initiated further investigations on Hg cycling and source identification. Here we report Hg records in sedimentary sequences to identify atmospheric sources during the past millennium. In addition to global transport and deposition, a potential atmospheric Hg source to be considered is the local emissions associated with volcanic activity, because the Park is situated in the Southern Volcanic Zone. Two sediment cores were extracted from Lake Tonček, a small, high-altitude system reflecting mainly direct inputs associated with atmospheric contributions, and Lake Moreno Oeste, a much larger and deeper lake having an extended watershed covered mostly by native forest. The sedimentary sequences were dated based on both 210Pb and 137Cs profiles. In addition, tephra layers were identified and geochemically characterized for chronological application and to investigate any association of volcanic eruptions with Hg records. Hg concentrations in sediments were measured along with 32 other elements, as well as organic matter, subfossil chironomids, and biogenic silica. Observed background Hg concentrations, determined from the sequence domains with lower values, ranged from 50 to 100 ng g−1 dry weight (DW), whereas the surficial layers reached 200 to 500 ng g−1 DW. In addition to this traditional pattern, however, two deep domains in both sequences showed dramatically increased Hg levels reaching 400 to 650 ng g−1 DW; the upper dated to the 18th to 19th centuries, and the lower around the 13th century. These concentrations are not only elevated in the present profiles but also many-fold above the background values determined in other fresh water sediments, as were also the Hg fluxes, reaching 120 to 150 μg m−2 y−1 in Lake Tonček . No correlation was observed between Hg concentrations and the contents of organic matter, subfossil chironomids, biogenic silica, or the other elements determined. However, distinctly increased Hg concentrations were observed immediately above some tephra layers, suggesting a link to volcanic events. Extended fires might be another potential atmospheric source because the earlier Hg peaks coincide with reported charcoal peaks, whereas the upper Hg peaks coincide with evidences of extended forest fires from tree-ring data and historical records.

Large geographical differences in the sensitivity of ice-covered lakes and rivers in the Northern Hemisphere to temperature changes.

Weyhenmeyer, G.A.; Livingstone, D.M.; Meili, M.; Jensen, O.; Benson, B.; Magnuson, J.J.
2010 | Glob. Change Biol.

Based on a unique dataset of more than 50 000 observations of ice phenology from 1213 lakes and 236 rivers in 12 different countries, we show that interannual variations in the timing of ice-on and ice-off on lakes and rivers are not equally pronounced over the entire Northern Hemisphere, but increase strongly towards geographical regions that experience only short periods during which the air temperature falls below 0 °C. We explain our observations by interannual fluctuation patterns of air temperature and suggest that lake and river ecosystems in such geographical regions are particularly vulnerable to global warming, as high interannual variability is known to have important ramifications for ecosystem structure and functioning. We estimate that the standard deviation of the duration of ice cover, viewed as a measure of interannual variability, exceeds 25 days for lakes and rivers located on 7% of the land area of the Northern Hemisphere. Such high variability might be an early warning signal for a critical transition from strictly dimictic, ice-covered systems to monomictic, open-water systems. Using the Global Lake and Wetland Database, we suggest that 3.7% of the world's lakes larger than 0.1 km2 are at high risk of becoming open-water systems in the near future, which will have immediate consequences for global biogeochemical cycles.

Mercury concentrations in landlocked Arctic char () from the Canadian Arctic. Part I: Insights from trophic relationships in 18 lakes.

Gantner, N.; Power, M.; Iqaluk, D.; Meili, M.; Borg, H.; Sundbom, M.; Solomon, K.R.; Lawson, G.; Muir, D.C.
2010 | Environ. Toxicol. Chem. | 29 (3) (621-632)
hg , mercury

Concentrations of mercury (Hg) have increased slowly in landlocked Arctic char over a 10- to 15-year period in the Arctic. Fluxes of Hg to sediments also show increases in most Arctic lakes. Correlation of Hg with trophic level (TL) was used to investigate and compare biomagnification of Hg in food webs from lakes in the Canadian Arctic sampled from 2002 to 2007. Concentrations of Hg (total Hg and methylmercury [MeHg]) in food webs were compared across longitudinal and latitudinal gradients in relation to δ13C and δ15N in periphyton, zooplankton, benthic invertebrates, and Arctic char of varying size-classes. Trophic magnification factors (TMFs) were calculated for the food web in each lake and related to available physical and chemical characteristics of the lakes. The relative content of MeHg increased with trophic level from 4.3 to 12.2% in periphyton, 41 to 79% in zooplankton, 59 to 72% in insects, and 74 to 100% in juvenile and adult char. The δ13C signatures of adult char indicated coupling with benthic invertebrates. Cannibalism among char lengthened the food chain. Biomagnification was confirmed in all 18 lakes, with TMFs ranging from 3.5 ± 1.1 to 64.3 ± 0.8. Results indicate that TMFs and food chain length (FCL) are key factors in explaining interlake variability in biomagnification of [Hg] among different lakes.

Contact information

Visiting addresses:

Geovetenskapens Hus,
Svante Arrhenius väg 8, Stockholm

Arrheniuslaboratoriet, Svante Arrhenius väg 16, Stockholm (Unit for Analytical and Toxicological Chemistry)

Mailing address:
Department of Environmental Science and Analytical Chemistry (ACES)
Stockholm University
106 91 Stockholm

Press enquiries should be directed to:

Stella Papadopoulou
Science Communicator
Phone +46 (0)8 674 70 11
stella.papadopoulou@aces.su.se