| 1. |
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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. |
- Eklöf, Karin, et al.
(författare)
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Forestry Influence by Stump Harvest and Site Preparation on Methylmercury, Total Mercury and Other Stream Water Chemistry Parameters Across a Boreal Landscape
- 2012
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Ingår i: Ecosystems (New York. Print). - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 15:8, s. 1308-1320
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Eklöf, Karin, et al.
(författare)
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Impact of Forestry on Total and Methyl-Mercury in Surface Waters : Distinguishing Effects of Logging and Site Preparation
- 2014
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 48:9, s. 4690-4698
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Tidskriftsartikel (refereegranskat)abstract
- Forestry operations can increase the export of mercury (both total and methyl) to surface waters. However, little is known about the relative contribution of different forestry practices. We address this question using a paired-catchment study that distinguishes the effects of site preparation from the antecedent logging. Runoff water from three catchments, two harvested and one untreated control, was sampled biweekly during one year prior to logging, two years after logging, and three years after site preparation. The logging alone did not significantly increase the concentrations of either total or methyl-mercury in runoff, but export increased by 50-70% in one of the harvested catchments as a consequence of increased runoff volume. The combined effects of logging and site preparation increased total and methyl-mercury concentrations by 30-50% relative to preharvest conditions in both treated catchments. The more pronounced concentration effect after site preparation compared to logging could be related to site preparation being conducted during summer. This caused more soil disturbance than logging, which was done during winter with snow covering the ground. The results suggest that the cumulative impact of forest harvest on catchment mercury outputs depends on when and how forestry operations are implemented.
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| 5. |
- Eklöf, Karin, et al.
(författare)
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Impact of stump harvest on run-off concentrations of total mercury and methylmercury
- 2013
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 290, s. 83-94
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Eklöf, Karin, et al.
(författare)
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Parsimonious Model for Simulating Total Mercury and Methylmercury in Boreal Streams Based on Riparian Flow Paths and Seasonality
- 2015
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 49:13, s. 7851-7859
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Tidskriftsartikel (refereegranskat)abstract
- The complexity of mercury (Hg) biogeochemistry has made it difficult to model surface water concentrations of both total Hg (THg) and especially methylmercury (MeHg), the species of Hg having the highest potential for bioaccumulation. To simulate THg and MeHg variation in low-order streams, we have adapted a conceptual modeling framework where a continuum of lateral flows through riparian soils determines streamflow concentrations. The model was applied to seven forest catchments located in two boreal regions in Sweden spanning a range of climatic, soil, and forest management conditions. Discharge, and simulated riparian soil water concentrations profiles, represented by two calibrated parameters, were able to explain much of the variability of THg and MeHg concentrations in the streams issuing from the catchments (Nash Sutcliffe (NS) up to 0.54 for THg and 0.58 for MeHg). Model performance for all catchments was improved (NS up to 0.76 for THg and 0.85 for MeHg) by adding two to four parameters to represent seasonality in riparian soil water THg and MeHg concentrations profiles. These results are consistent with the hypothesis that riparian flow-pathways and seasonality in riparian soil concentrations are the major controls on temporal variation of THg and MeHg concentrations in low-order streams.
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| 7. |
- Gantner, Nikolaus, et al.
(författare)
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MERCURY CONCENTRATIONS IN LANDLOCKED ARCTIC CHAR (SALVELINUS ALPINUS) FROM THE CANADIAN ARCTIC. PART I : INSIGHTS FROM TROPHIC RELATIONSHIPS IN 18 LAKES
- 2010
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Ingår i: Environmental Toxicology and Chemistry. - : Wiley. - 0730-7268 .- 1552-8618. ; 29:3, s. 621-632
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Tidskriftsartikel (refereegranskat)abstract
- 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 delta C-13 and delta N-15 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 delta C-13 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. Environ. Toxicol. Chem. 2010; 29: 621-632. (C) 2009 SETAC
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| 8. |
- Gantner, Nikolaus, et al.
(författare)
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MERCURY CONCENTRATIONS IN LANDLOCKED ARCTIC CHAR (SALVELINUS ALPINUS) FROM THE CANADIAN ARCTIC. PART II : INFLUENCE OF LAKE BIOTIC AND ABIOTIC CHARACTERISTICS ON GEOGRAPHIC TRENDS IN 27 POPULATIONS
- 2010
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Ingår i: Environmental Toxicology and Chemistry. - : Wiley. - 0730-7268 .- 1552-8618. ; 29:3, s. 633-643
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Tidskriftsartikel (refereegranskat)abstract
- Among-lake variation in mercury (Hg) concentrations in landlocked Arctic char was examined in 27 char populations from remote lakes across the Canadian Arctic. A total of 520 landlocked Arctic char were collected from 27 lakes, as well as sediments and surface water from a subset of lakes in 1999, 2002, and 2005 to 2007. Size, length, age, and trophic position (delta N-15) of individual char were determined and relationships with total Hg (THg) concentrations investigated, to identify a common covariate for adjustment using analysis of covariance (ANCOVA). A subset of 216 char from 24 populations was used for spatial comparison, after length-adjustment. The influence of trophic position and food web length and abiotic characteristics such as location, geomorphology, lake area, catchment area, catchment-to-lake area ratio of the lakes on adjusted THg concentrations in char muscle tissue were then evaluated. Arctic char from Amituk Lake (Cornwallis Island) had the highest Hg concentrations (1.31 mu g/g wet wt), while Tessisoak Lake (Labrador, 0.07 mu g/g wet wt) had the lowest. Concentrations of THg were positively correlated with size, delta N-15, and age, respectively, in 88, 71, and 58% of 24 char populations. Length and delta N-15 were correlated in 67% of 24 char populations. Food chain length did not explain the differences in length-adjusted THg concentrations in char. No relationships between adjusted THg concentrations in char and latitude or longitude were found, however, THg concentrations in char showed a positive correlation with catchment-to-lake area ratio. Furthermore, we conclude that inputs from the surrounding environment may influence THg concentrations, and will ultimately affect THg concentrations in char as a result of predicted climate-driven changes that may occur in Arctic lake watersheds. Environ. Toxicol. Chem. 2010; 29: 633-643.
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| 9. |
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| 10. |
- Guimarães, Jean R.D., et al.
(författare)
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Simultaneous radioassays of bacterial production and mercury methylation in the periphyton of a tropical and a temperate wetland
- 2006
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Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797 .- 1095-8630. ; 81:2, s. 95-100
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory radioassays were made to study mercury (Hg) methylation together with bacterial production in the periphyton of two aquatic macrophytes, the submerged Myriophyllum spicatum, from a constructed wetland in Sweden and the floating Eichhornia crassipes, from a eutrophied tropical lake in Brazil. Time course incubations were made by addition of 203HgCl2 and the methylmercury formed was extracted at pre-defined time intervals. Bacterial production (14C-leucine incorporation) was measured at the same time intervals, with plants removed from parallel incubations made with and without addition of cold HgCl2. For E. crassipes, higher methylmercury production was observed at elevated bacterial production, whereas for M. spicatum, the bacterial production was significantly lower, and Hg methylation was below the detection limit. The combined results confirm the importance of microbial processes for Hg methylation, although other factors are known to influence this process in complex ways. The addition of Hg did not significantly influence bacterial production, while the incubation temperatures used (25 and 35 1C) resulted in different methylation rates. Radiotracer techniques for measurements of bacterial production such as 14C-leucine uptake can provide useful insights into the Hg cycle in aquatic environments, and our data suggest that they may be used as a proxy of mercury methylation potentials.
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| 11. |
- Hylander, Lars D., et al.
(författare)
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500 years of mercury production: global annual inventory by region until 2000 and associated emissions
- 2003
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Ingår i: Sci. Total Environ. ; 304:1-3, s. 13-27
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Tidskriftsartikel (refereegranskat)abstract
- Since pre-industrial times, anthropogenic emissions of Hg have at least doubled global atmospheric Hg deposition rates.In order to minimize environmental and human health effects, efforts have been made to reduce Hg emissions from industries and power plants, while less attention has been paid to Hg mining.This paper is a compilation of available data on primary Hg production and associated emissions with regional and annual resolution since colonial times.Globally, approximately one million tons of metallic Hg has been extracted from cinnabar and other ores during the past five centuries, half already before 1925.Roughly half has been used for mining of gold and silver, but the annual Hg production peaked during a short period of recent industrial uses.Comparison with total historic Hg deposition from global anthropogenic emissions (0.1–0.2 Mtons) suggests that only a few percent of all mined Hg have escaped to the atmosphere thus far.While production of primary Hg has changed dramatically over time and among mines, the global production has always been dominant in the region of the mercuriferous belt betweenthe western Mediterranean and central Asia, but appears to be shifting to the east.Roughly half of the registered Hg has been extracted in Europe, where Spanish mines alone have contributed one third of the world’s mined Hg. Approximately one fourth has been mined in the Americas, and most of the remaining registered Hg in Asia. However, the Asian figures may be largely underestimated.Pr esently, the dominant Hg mines are in Almade´n in Spain (236 t of Hg produced in 2000), Khaydarkan in Kyrgyzstan (550 t), Algeria (estimated 240 t) and China (ca. 200 t).Mer cury by-production from mining of other metals (e.g. copper, zinc, gold, silver) in 2000 includes 48 t from Peru, 45 t from Finland and at least 15 t from the USA.Since 1970, the recorded production of primary Hg has been reduced by almost an order of magnitude to approximately 2000 t in the year 2000.Mining is thus still of similar magnitude as all current anthropogenic Hg emissions to the atmosphere, and mined Hg may account for more than one third of these emissions.Also before use, mercury is emitted from Hg mines locally during the mining and refining processes and from mining waste.Global direct emissions to the atmosphere amount to 10–30 t per year currently (up to 10 at Almade´n alone), and probably exceed 10 000 t historically.T ermination of Hg mining will reduce associated local emissions to the atmosphere and biosphere.Since several economically viable Hg-free alternatives exist for practically all applications of Hg, the production and use of Hg can be further reduced and all primary production of Hg other than by-production terminated.
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| 12. |
- Hylander, Lars D., et al.
(författare)
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Fish mercury increase in Lago Manso, a new hydroelectric reservoir in tropical Brazil
- 2006
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Ingår i: Journal of Environmental Management. - : Elsevier BV. - 0301-4797 .- 1095-8630. ; 81:2, s. 155-166
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Tidskriftsartikel (refereegranskat)abstract
- It has been frequently demonstrated that mercury (Hg) concentrations in fish rise in newly constructed hydroelectric reservoirs in the Northern Hemisphere. In the present work, we studied whether similar effects take place also in a tropical upland reservoir during impoundment and discuss possible causes and implications. Total Hg concentrations in fish and several soil and water parameters were determined before and after flooding at Rio Manso hydroelectric power plant in western Brazil. The Hg concentrations in soil and sediment were within the background levels in the region (22-35 ng g(-1) dry weight). There was a strong positive correlation between Hg and carbon and sulphur in sediment. Predatory fish had total Hg concentrations ranging between 70 and 210 ng g(-1) f.w. 7 years before flooding and between 72 and 755 ng g(-1) f.w. during flooding, but increased to between 216 and 938 ng g(-1) f.w. in the piscivorous and carnivorous species Pseudoplatystoma fasciatum, cachara, and Salminus brasiliensis, dourado, 3 years after flooding. At the same time, concentrations of organic carbon in the water increased and oxygen concentrations decreased, indicating increased decomposition and anoxia as contributing to the increased Hg concentrations in fish. The present fish Hg concentrations in commonly consumed piscivorous species are a threat to the health of the population dependent on fishing in the dam and downstream river for sustenance. Mercury exposure can be reduced by following fish consumption recommendations until fish Hg concentrations decrease to a safe level.
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| 13. |
- Hylander, Lars Daniel, 1954-, et al.
(författare)
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Mercury By-Production and Emissions at Pyrometallurgical Extraction of Nonferrous Sulfide Ores Globally
- 2009
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Ingår i: Proceedings of the 9th International Conference on Mercury as a Global Pollutant. ; , s. 42-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Pyrometallurgical extraction of nonferrous sulfide ores may be a significant source of mercury (Hg) emissions and Hg by-production globally. In this study, we estimate Hg emissions from the pyrometallurgical treatment of Cu, Pb, and Zn sulfide ores. We base our calculations on quantities processed and Hg content in the concentrates, derived from unique global databases on smelter feed and production. In 2005, about 275 tons of Hg were emitted globally to the atmosphere from Cu, Pb, and Zn smelters. Nearly one-half was emitted from Zn smelters and the other half equally divided between Cu and Pb smelters. Most Hg was emitted in China, followed by the Russian Federation, India, and South Korea. Calculations indicate that Hg abatementtechnologies applied to flue gases may have recovered 8.8 tons and 228 tons Hg from Pb and Zn smelters, respectively, most of which was probably sold as a byproduct. In conclusion, Hg emitted from processing copper, lead, and zinc ores has been largely underestimated in Hg emission inventories, amounting to rougly the same amounts of Hg by-production and Hg emissions as industrial gold mining. Reducing these emissions may be one of the most economical measures to reduce global Hg emissions.
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| 14. |
- Hylander, Lars D, et al.
(författare)
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The rise and fall of mercury: converting a resource to refuse after 500 years of mining and pollution.
- 2005
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Ingår i: Critical reviews in environmental science and technology. - : Taylor & Francis Inc.. - 1064-3389 .- 1547-6537. ; 35:1, s. 1-36
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Tidskriftsartikel (refereegranskat)abstract
- The link of mercury (Hg) pollution to Hg mining is rarely made,although Hg primary production presently is as large as global Hg emissions from coal combustion. Here we present historical comparisons on global, continental and national scales, covering up to five centuries of Hg production and consumption. Nearly half of the historical consumption has been pre-industrial, notably for silver and gold mining by amalgamation. More than half has been mined in Europe and one quarter in the Americas. Four economic periods with different control of global Hg price and production were discerned: The Hg price rose sharply after 1830 when Spain no longer controlled the Hg market and when consumption started to shift to gold mining in North America and later on industrial uses. In the 1970’s, however, the price as well as quantities consumed plunged as a result of rising health and environmental concerns. In Sweden, per-capita consumption has recently dropped below pre-industrial levels, exemplifying a successful implementation of environmental policy. The chlor-alkali industry is still the globally dominating Hg consumer, and large stocks to be decommissioned in industrialized countries need political guidance to avoid transfer of Hg and related risks to other countries, a potential transfer to small-scale miners favoured by low Hg prices.
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| 15. |
- Hylander, Lars Daniel, 1954-, et al.
(författare)
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Zero mercury emission strategy in Sweden.
- 2008
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Ingår i: NIMD Forum 2008. Mercury Recycling and Environmental Monitoring for a Sustainable Society. - Minamata City, Kumamoto, Japan. : Ministry of the Environment, Japan, National Institute for Minamata Disease. ; , s. 16-27
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Mercury (Hg) is of world-wide concern because of its toxicity not only to humans but also to other higher forms of life as well as microorganisms in natural environments. Methyl-Hg is the species of particular concern for birds, fish and mammals, where biomagnification in long food chains results in hazardous exposure of top predators including humans. Elemental Hg is transformed to methyl-Hg in nature by processes difficult to control, and any emission of inorganic Hg will ultimately result in increased levels of methyl-Hg in our environment. Restricting anthropogenic emissions of Hg is thus a priority for counteracting an increase of methyl-Hg levels in biota. To eliminate the sources is a cost-effective way of eliminating related emissions. There are three primary sources of anthropogenic Hg emissions: 1.) combustion of fossil fuels; 2.) dedicated mining of Hg; and 3.) refining processes and mining of minerals for recovering of other elements than Hg. Mercury produced by mining and refining is used in a wide variety of products such as thermometers, dental amalgam, lamps, and batteries, resulting in Hg emissions at production, usage, and disposal. Swedish authorities were first to act by enforcing nationwide legislation against the use of Hg, to avoid tragedies such as those in Minamata, Japan. Consequently, seed dressing with methyl-Hg was prohibited in 1966, and fenyl-Hg in slimicides was prohibited in 1967. Total emissions of Hg from Swedish chlor-alkali plants to air and waters were reduced from more than 30 t per year in the 1950’s and 1960’s to less than 0.1 t nowadays. Sale of clinical thermometers containing Hg is prohibited since 1992, and Hg exports are banned since 1997. A general ban on the use of Hg in processes and products is presently considered by the government. From the ban there will be exceptions only where Hg free alternatives still have a limited market share, such as energyefficient lamps. Recycling of Hg is discouraged in Sweden, since continued use of Hg-containing products inevitably results in losses of Hg to air, soil and water, thus adding to the risks of human exposure. Mercury-containing equipments, products, and waste are instead collected for permanent disposal in a safe deep-bedrock repository with minimal losses. This has by Swedish authorities been considered as the only feasible solution to obtain zero Hg emissions from the Swedish technosphere. Further information may be obtained from the Swedish Chemicals Agency (www.kemi.se) and the Swedish Environmental Protection Agency (www.naturvardsverket.se).
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| 16. |
- Jonsson, Anders, et al.
(författare)
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Whole-lake mineralization of allochthonous and autochthonous organic carbon in a large humic lake (Örträsket, N. Sweden)
- 2001
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 46:7, s. 1691-1700
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Tidskriftsartikel (refereegranskat)abstract
- Organic carbon mineralization was studied. in a large humic lake (Lake Örträsket) in northern Sweden during a well-defined summer stratification period following high water flow during snowmelt. Several independent methods including plankton counts, measurements of bacterioplankton and phytoplankton production, stable isotope monitoring, sediment trapping, and mass balance calculations were used. Total organic carbon mineralization showed a summer mean of 0.3 g C m(-2) d(-1) and was partitioned about equally between water and sediment. In the water column, organic matter was mineralized by bacteria (60%) and protozoan and metazoan zooplankton (30%), as well as by photooxidation (10%). Most of the mineralized organic carbon was of allochthonous origin. Primary production in the lake contributed at most 5% of the total organic carbon input and about 20% of the total organic carbon mineralization. Total carbon mineralization in. the epilimnion and metalimnion agreed well with an estimate of CO2 evasion from the stratified lake, while CO2 accumulation in the hypolimnion matched the O-2 consumption and resulted in a very negative delta C-13 of DIC before autumn overturn (-23 parts per thousand). Isotopic compositions of DIC and POC confirmed the dominant influence of terrestrial organic input on the cycling of both organic and inorganic carbon in the lake.
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| 17. |
- Jönsson, Anders, et al.
(författare)
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Evaluation of the Stockholm archipelago, northwestern Baltic Sea proper, as a trap for freshwater-runoff organic carbon
- 2005
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 56:1-2, s. 167-178
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Tidskriftsartikel (refereegranskat)abstract
- Time-series data on the freshwater inflow of total organic carbon (TOC) to the Stockholm Archipelago, Baltic Sea, covering four full years, showed a distinct seasonal pattern with six times higher monthly flow in winter–spring than in the summer with an annual freshwater TOC input of 28 Gg year−1. Estimation of burial flux and source apportionment of sedimentary OC in the Inner Archipelago (IA) was based on extensive sediment sampling of seismically surveyed accumulation bottom areas. The resulting IA-averaged OC content was 56±16 mg g dw−1 sediment, yielding an IA-wide bottom sediment deposition for the 1992–1995 period of 3.1 Gg year−1. The sediments in the eastern Lake Mälaren (LM), IA, and Outer Archipelago (OA) were geochemically distinguishable based on their stable carbon isotope signatures (δ13C). The δ13C values were −28.2±0.6, −25.4±1.0, and −23.6±0.3, respectively, for LM (n=15), IA (n=17), and OA (n=31). These spatial trends were consistent with the C:N ratios, which were 9.96±1.2, 9.29±0.73, and 9.13±0.22 for the same subsystems. Using a simple isotopic mass balance model, it was deduced that about one-third (39%) of the OC burial in the IA sediments was of Lake Mälaren runoff origin. Hence, a low archipelago-trapping efficiency of only 4% for the runoff TOC was found to be accumulating in the sediments underlying the approximately 30 km transect through the IA eastward of Stockholm. This scenario suggests that the organic matter and associated substances added by the Lake Mälaren outflow, passing through urban Stockholm, are largely either remineralised and released to the IA water column, or transported with the currents to more pristine offshore Baltic ecosystems.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Munthe, John, et al.
(författare)
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Mercury in Nordic ecosystems
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report provides a first comprehensive compilation and assessment of available data on mercury in air, precipitation, sediments and fish in the Nordic countries. The main conclusion is that mercury levels in Nordic ecosystems continue to be affected by long-range atmospheric transport. The geographical patterns of mercury concentrations in both sediments and fish are also strongly affected by ecosystem characteristics and in some regions possibly by historical pollution. An evaluation of geographical variations in mercury concentrations in precipitation indicates that the influence from anthropogenic sources from Central European areas is still significant. The annual variability of deposition is large and dependant of precipitation amounts. An evaluation of data from stations around the North Sea has indicated a significant decrease in mercury concentrations in precipitation indicating a continuous decrease of emissions in Europe (Wängberg et al., 2007). For mercury in air (TGM), the geographical pattern is less pronounced indicating the influence of mercury emissions and distribution over a larger geographical area (i.e. hemispherical transport). Comparison of recent (surficial) and historical lake sediments show significantly elevated concentrations of mercury most likely caused by anthropogenic atmospheric deposition over the past century. The highest pollution impact was observed in the coastal areas of southern Norway, in south western Finland and in Sweden from the coastal areas in the southwest across the central parts to the north-east. The general increase in recent versus old sediments was 2-5 fold. Data on mercury in Nordic freshwater fish was assembled and evaluated with respect to geographical variations. The fish data were further compared with temporal and spatial trends in mercury deposition and mercury contamination of lake sediments in order to investigate the coupling between atmospheric transport and deposition of mercury and local mercury pollution effects (i.e. methylmercury in fish). The general pattern of fish contamination follows to some extent a pattern similar to that of current and previous atmospheric pollution. Large areas have fish with mercury concentrations exceeding the health advisory guideline of 0.5 mg/kg or 1.0 mg/kg (for northern pike) in the EU and of around 0.3 mg kg-1 in the USA, thus restricting their use for human consumption. A more comprehensive assessment of factors influencing levels of methylmercury in fish has to include a number of other parameters such as catchment characteristics (e.g. relative size, presence of wetlands), contents and fluxes of DOC in soil run-off and surface waters as well as methylation potential within ecosystems.
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| 23. |
- Olchev, Alexander, et al.
(författare)
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Evidence of temperature and precipitation change over the past 100years in a high-resolution pollen record from the boreal forest of Central European Russia
- 2017
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 27:5, s. 740-751
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Tidskriftsartikel (refereegranskat)abstract
- Near-annual pollen records for the last 100years were obtained from a 65-cm peat monolith from a raised peat bog in the Central Forest State Natural Biosphere Reserve (southern part of the Valdai Hills, European Russia) and compared with the available long-term meteorological observations. An age-depth model for the peat monolith was constructed by Pb-210 and Cs-137 dating. Cross-correlation and the Granger causality analysis indicated a broad range of statistically significant correlations between the pollen accumulation rate (PAR) of the main forest-forming trees and shrubs (Picea, Pinus, Betula, Tilia, Quercus, Ulmus, Alnus, and Corylus) and the air temperature and precipitation during the previous 3years. Results showed that high air temperatures during the growing season (May-September) in the year prior to the flowering led to an increase in pollen productivity of the main tree species. The statistically significant correlation between the PAR of trees and shrubs and winter precipitation of the current and previous years could reflect the influence of winter precipitation on soil water availability and as a result on tree growth and functioning in the spring.
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| 24. |
- Pampura, T. V., et al.
(författare)
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Buried Paleosols as Reference Objects for Assessing the Current Level of Soil Pollution with Lead in the Lower Volga Steppes
- 2019
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Ingår i: Eurasian Soil Science. - 1064-2293 .- 1556-195X. ; 52:1, s. 34-49
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Tidskriftsartikel (refereegranskat)abstract
- The estimation of soil contamination with anthropogenic lead requires uncontaminated analogues of the recent soils for comparison. For this purpose, a paleosol buried under a 2-m high burial mound of the Bronze Age and protected by it from atmospheric deposition during 4500 years was studied. The content and isotopic composition of mobile and total lead in the buried and recent soils (roadside and remote from lead sources) were compared. Obvious signs of anthropogenic contamination were revealed in only the upper layer of the roadside soil within 10 m from a highway. These were an increase in the absolute content of all lead forms; a high relative content of mobile forms; high ratios of Pb relative to Ti, Zr, and Y; and the similarity between isotopic compositions of the soil lead and the lead from modern atmospheric aerosols and Russian gasoline. Interestingly, no significant difference was found in the total lead contents or in the isotopic compositions between the recent soil remote from roads and the buried soil. However, some signs of anthropogenic impact could be revealed by the analysis of mobile lead forms, which make up a small portion of the total content.
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| 25. |
- Ribeiro Guevara, S., et al.
(författare)
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Sediment records of highly variable mercury inputs to ultraoligotrophic mountain lakes in Patagonia during the past millennium.
- 2010
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Ingår i: Atmospheric Chemistry And Physics. - 1680-7316 .- 1680-7324. ; 10, s. 3443-3453
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Tidskriftsartikel (refereegranskat)abstract
- 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 Tonˇcek, 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 μgm−2 y−1 in Lake Tonˇcek. 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.
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| 26. |
- Rieder, Stephan R., et al.
(författare)
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Dynamic modelling of the long term behaviour of cadmium, lead and mercury in Swiss forest soils using CHUM-AM
- 2014
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 468, s. 864-876
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Tidskriftsartikel (refereegranskat)abstract
- The applicability of the dynamic soil model CHUM-AM was tested to simulate concentrations of Cd, Pb and Hg in five Swiss forest soils. Soil cores of up to 50 cm depth were sampled and separated into two defined soil layers. Soil leachates were collected below the litter by zero-tension lysimeters and at 15 and 50 cm soil depths by tension lysimeters over two years. The concentrations of Cd, Pb and Hg in the solid phase and soil solution were measured by ICP-MS (Cd, Pb) or CV-AFS (Hg). Measured metal concentrations were compared with modelled concentrations using CHUM-AM. Additionally we ran the model with three different deposition scenarios (current deposition; maximum acceptable deposition according to the Swiss ordinance on Air Pollution Control; critical loads according to CLRTAP) to predict metal concentrations in the soils for the next 1000 years. Assuming current loads concentrations of Cd and Pb showed varying trends (increasing/decreasing) between the soils. Soils rich in organic carbon or with a high pH value showed increasing trends in Cd and Pb concentrations whereas the concentrations in the other soils decreased. In contrast Hg concentrations are predicted to further increase in all soils. Critical limits for Pb and Hg will partly be exceeded by current loads or by the critical loads proposed by the CLRTAP but the critical limits for Cd will rarely be reached within the next 1000 years. In contrast, maximal acceptable deposition will partly lead to concentrations above the critical limits for Pb in soils within the next 400 years, whereas the acceptable deposition of Cd will not lead to concentrations above the proposed critical limits. In conclusion the CHUM-AM model is able to accurately simulate heavy metal (Cd, Pb and Hg) concentrations in Swiss forest soils of various soil properties.
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| 27. |
- Skyllberg, Ulf, et al.
(författare)
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Chemical speciation of mercury, sulfur and iron in a dystrophic boreal lake sediment, as controlled by the formation of mackinawite and framboidal pyrite
- 2021
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533 .- 0046-564X. ; 294, s. 106-125
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Tidskriftsartikel (refereegranskat)abstract
- The chemical speciation of mercury (Hg), methyl mercury (MeHg), sulfur and iron was investigated in the sediment and porewater of Lake Angessjon, a boreal, shallow (maximum depth 2.5 m), oligo-/dystrophic lake in northern Sweden. The lake receives terrestrial stream runoff from surrounding coniferous forest soils and peatlands having a low pH (4.6) and high concentrations of dissolved organic matter (DOM, annual average: 45 mg L-1), Fe (60 mu M), sulfate (105 mu M), inorganic Hg (1200 pM) and MeHg (250 pM). Sulfur K-edge XANES and Hg L-m-edge EXAFS spectroscopic measurements were used to characterize and quantify the sulfur speciation in the lake sediment at nine occasions, covering different seasons in the years of 2007 and 2009. In the surface sediment (0-3 cm) sulfate is reduced to zero-valent S and inorganic sulfide, that in turn reacts with Fe to form FeSm (mackinawite) and FeS2 (framboidal pyrite). The latter mineral becomes increasingly dominant by depth in the sediment. Thermodynamic modeling successfully predicted measured porewater concentrations of Hg in the sediment. Metacinnabar (beta-HgS) and Hg(NOM-RS)(2) complexes (the latter formed as a reaction between Hg(II) and thiol groups associated with natural organic matter, NOM-RSH) were the dominant forms of Hg(II) in the solid phase of sediments and Hg(II)-polysulfides (aq) dominated in the porewater. We argue that FeS m is a key component that indirectly controlled the Hg (II) speciation in the sediment by keeping the aqueous phase concentration of inorganic sulfide in the 0.5-2 mu M range throughout the year. Besides providing a pool of readily soluble inorganic sulfide for formation of beta-HgS(s), as demonstrated by previously reported EXAFS experiments, we further suggest FeS m may serve as a precursor for the formation of a more crystalline (less soluble) beta-HgS(s) phase than present in environments devoid of FeSm. Support for this was provided by comparing our results with previously reported thermodynamic modelling results of Hg(II) and MeHg solubility in organic soils devoid of FeSm. In more general terms, we suggest the presence or absence of FeSm, through its influence on the chemical speciation of Hg and MeHg, may be a key factor behind the variability in rates of Hg(II) and MeHg transformation processes, such as methylation, reduction and demethylation, reported for different environmental settings.
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| 28. |
- Skyllberg, Ulf, et al.
(författare)
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Elevated Concentrations of Methyl Mercury in Streams after Forest Clear-Cut : A Consequence of Mobilization from Soil or New Methylation?
- 2009
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:22, s. 8535-8541
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Tidskriftsartikel (refereegranskat)abstract
- Concentrations of inorganic, mercuric mercury (Hg-II), methyl mercury (MeHg) and ancillary chemistry measured in first-order streams draining 0-4 (N = 20) and 4-10 (N = 27) year-old clear-cuts of former Norway Spruce Picea abies (Karst.) forest stands were compared with concentrations in streams draining 70 year-old Norway Spruce reference stands(N = 10). Concentrations of MeHg, and ratios of MeHg TOC-1 and Hg-II TOC-1, were significantly (p 0.01)elevated in 0-4 year-old clear-cuts, as compared to references. The only ancillary variable showing a significant elevation for 0-4 year-old clear-cuts was Mn (P 0.02). The 4-10 year-old clear-cuts showed intermediate concentrations with nonsignificant differences as compared to references, pH, nitrate, sulfate, Ca, Fe, TOC, TON, and the aromaticity of TOC (SUVA(254 nm)) showed nonsignificant differences between clear-cut age classes and references, Assuming that MeHg and Hg-II are mobilized from soil to stream to a similar relative extent as a consequence of clear-cutting, a calculation showed that 1/6 of the elevated MeHg concentration was due to enhanced mobilization from soil and 5/6 was due to new methylation of Hg-II 0-4 years after clear-cut New methylation after clear-cut is suggested to be stimulated by an increased availability of electron donors for methylating bacteria, as a consequence of degradation of logging residue ("slash") and soil organic matter. A subdivision of sites situated above and below the highest postglacial coastline (HC) revealed a significant elevation of MeHg, MeHg TOC-1 and Hg-II TOC-1 (p 0.05) beyond their references in 0-4 year-old clear-cuts above (but not below) the HC. This suggests that postglacial deposits of FeS(s) and FeS2(s) were not an important factor for elevation of MeHg after clear-cut.
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
- Sörensen, Rasmus, et al.
(författare)
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Forest Harvest Increases Runoff Most during Low Flows in Two Boreal Streams
- 2009
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Ingår i: Ambio. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 38:7, s. 357-363
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- To understand how forest harvest influences the aquatic environment, it is essential to determine the changes in the flow regime. This paper presents changes in the hydrological regime during the first 2 y after harvest in two catchments of the Balsjo Catchment Study in Sweden. The changes were judged relative to a reference catchment, calibrated during an 18-mo pretreatment period starting in September 2004. From August 2006 through March 2008, there was an average of 35% more runoff from the harvested catchments relative to the reference. The flow increased most during the growing seasons and at base flows (< 1 mm d(-1); 58-99% increase), followed by dormant season and intermediate flows (30-43%). No significant changes were observed during the highest flows (over 5 mm d(-1)), except for the spring flood a few weeks after harvest, which was delayed and attenuated. Large relative changes in low flow may influence the ecosystem by altering the aquatic habitat
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| 34. |
- Sörensen, Rasmus, et al.
(författare)
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The Effects of Forest Harvest Operations on Mercury and Methylmercury in Two Boreal Streams : Relatively Small Changes in the First Two Years prior to Site Preparation
- 2009
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Ingår i: Ambio. - : Royal Swedish Academy of Sciences. - 0044-7447 .- 1654-7209. ; 38:7, s. 364-372
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Tidskriftsartikel (refereegranskat)abstract
- Forest harvest is hypothesized to increase the mercury (Hg) load in aquatic ecosystems. The Balsjo paired catchment study examined the outputs of methylmercury (MeHg) and total mercury (Hg-tot) from two boreal catchments during the 2 y following forest harvest but prior to site preparation. This enabled us to separate the effect of the two operations that followed best management practices. Hg-tot concentrations increased by approximately 15%, and fluxes by 20-30%. The MeHg concentrations and fluxes either declined or increased by up to 60%, depending on whether annual MeHg peaks during summer low flows were considered to have been influenced by forest harvest. The lack of a severalfold increase in Hg outputs after forest harvest, as reported from other sites, may be the result of minimal soil disturbance during the winter forest harvest operations. If so, there may be a greater Hg response after soil scarification to prepare for planting
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| 35. |
- Tjerngren, Ida, et al.
(författare)
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Eight Boreal Wetlands as Sources and Sinks for Methyl Mercury in Relation to Soil Acidity, C/N Ratio, and Small-Scale Flooding
- 2012
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 46:15, s. 8052-8060
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Tidskriftsartikel (refereegranskat)abstract
- Four years of catchment export and wetland input-output mass balances are reported for inorganic Hg (Hg-inorg), 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 Hg-inorg. 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 similar to 5.0) and C/N ratio (similar to 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.
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| 36. |
- Vuorio, K., et al.
(författare)
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Natural isotopic composition of carbon (delta C-13) correlates with colony size in the planktonic cyanobacterium Gloeotrichia echinulata
- 2009
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 54:3, s. 925-929
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Tidskriftsartikel (refereegranskat)abstract
- To assess variability in carbon isotope signatures (delta C-13) between and within populations under natural conditions, with a particular emphasis on colony size, we repeatedly collected planktonic colonies of a freshwater cyanobacterium Gloeotrichia echinulata in two lakes, Pyhajarvi (southwest Finland) and Erken (southeast Sweden). Despite substantial differences in the average delta C-13 signature of Gloeotrichia between lakes (-6.9 parts per thousand in Pyhajarvi and -20.7 parts per thousand in Erken), a similar, systematic increase in delta C-13 with colony size was observed in both lakes (of 2-3 parts per thousand in Pyhajarvi and 3-5 parts per thousand in Erken). This suggests declining isotope fractionation with increasing colony size, probably related to diffusion limitation of carbon availability. Temporal variation explained a minor fraction of total subsample variability (range delta C-13 similar to 4 parts per thousand in Pyhajarvi and similar to 6 parts per thousand in Erken). Isotopic C-13 fractionation in Gloeotrichia was likely affected both by carbon source and by colony size.
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| 37. |
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| 38. |
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| 39. |
- Weyhenmeyer, Gesa, et al.
(författare)
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Large geographical differences in the sensitivity of ice-covered lakes and rivers in the Northern Hemisphere to temperature changes
- 2011
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 17:1, s. 268-275
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Tidskriftsartikel (refereegranskat)abstract
- 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 degrees 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.
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| 40. |
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| 41. |
- Åkerblom, Staffan, et al.
(författare)
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Half a century of changing mercury levels in Swedish freshwater fish
- 2014
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 43, s. 91-103
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Tidskriftsartikel (refereegranskat)abstract
- 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 of fish from any species and of any size were normalized to correspond to a standard 1-kg pike [median: 0.69 mg kg(-1) wet weight (ww), mean +/- SD: 0.84 +/- 0.67 mg kg(-1) ww]. The EU Environmental Quality Standard of 0.02 mg kg(-1) was exceeded in all waters, while the guideline set by FAO/WHO for Hg levels in fish used for human consumption (0.5-1.0 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 consistent regional pattern. During the latest decade (2003-2012), however, a spatial gradient has emerged with decreasing trends predominating in southwestern Sweden.
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| 42. |
- Åkerblom, Staffan, et al.
(författare)
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Organic Matter in Rain : An Overlooked Influence on Mercury Deposition
- 2015
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Ingår i: Environmental Science and Technology Letters. - : American Chemical Society (ACS). - 2328-8930. ; 2:4, s. 128-132
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Tidskriftsartikel (refereegranskat)abstract
- The importance of Hg emissions for deposition will be scrutinized in the future as new legislation to control emissions of Hg to the atmosphere comes into effect. We show that mercury (Hg) concentrations in rainfall are closely linked to organic matter (OM) with consistent Hg/TOC ratios over large spatial scales decreasing from that in an open field (OF, 1.5 mu g g(-1)) to that in throughfall (TF, 0.9 mu g g(-1)). The leaf area index was positively correlated with both TF [Hg] and total organic carbon ([TOC]), but not the Hg/TOC ratio. This study shows that the progression in the Hg/TOC ratio through catchments starts in precipitation with Hg/TOCbulk dep > Hg/TOCsoil (water) > Hg/TOCstreamwater These findings raise an intriguing question about the extent to which it is not just atmospheric [Hg] but also OM that influences [Hg] in precipitation. This question should be resolved to improve the ability to discern the importance of changing global Hg emissions for deposition of Hg at specific sites.
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| 43. |
- Åkerblom, Staffan, et al.
(författare)
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Partitioning of Hg between solid and dissolved organic matter in the humus layer of boreal forests
- 2008
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Ingår i: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 1573-2932 .- 0049-6979. ; 189:1-4, s. 239-252
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Tidskriftsartikel (refereegranskat)abstract
- The mobility of mercury (Hg) deposited on soils controls the concentration and toxicity of Hg within soils and in nearby streams and lakes, but has rarely been quantified under field conditions. We studied the in situ partitioning of Hg in the organic top layer (mor) of podsols at two boreal forest sites differing in Hg deposition and climatic regime (S. and N. Sweden, with pollution declining to the north). Soil solution leaching from the mor layer was repeatedly sampled using zero-tension lysimeters over 2 years, partly in parallel with tension lysimeters. Concentrations of Hg and dissolved organic carbon (DOC) were higher while pH was lower at the southern site (means +/- SD: Hg=44 +/- 15 ng L-1, DOC=63.0 +/- 31.3 mg L-1, pH=4.05 +/- 0.53) than at the northern site (Hg=22 +/- 6 ng L-1, DOC=41.8 +/- 12.1 mg L-1, pH=4.28 +/- 0.43). There was a positive correlation over time between dissolved Hg and DOC at both sites, even though the DOC concentration peaked during autumn at both sites, while the Hg concentration remained more constant. This correlation is consistent with the expected strong association of Hg with organic matter and supports the use of Hg/C ratios in assessments of Hg mobility. In the solid phase of the overlying O-f layer, both Hg concentrations and Hg/C ratios were higher at the southern site (means +/- SD: 0.34 +/- 0.06 mu g g(-1) dw and 0.76 +/- 0.14 mu g g(-1) C, respectively) than at the northern site (0.31 +/- 0.05 mu g g(-1) dw and 0.70 +/- 0.12 mu g g(-1) C, respectively). However, concentrations in the solid phase differed less than might be expected from the difference in current atmospheric input, suggesting that the fraction of natural Hg is still substantial. At both sites, Hg/C ratios in the upper half of the mor layer were only about two thirds of those in the lower half, suggesting that the recent decrease in anthropogenic Hg deposition onto the soil is offset by a natural downward enrichment of Hg due to soil decomposition or other processes. Most interestingly, comparison with soil leachate showed that the average Hg/C ratios in the dissolved phase of the mor layers at both sites did not differ from the average Hg/C ratios in the overlying solid organic matter. These results indicate a simple mobilisation with negligible fractionation, despite differences in Hg deposition patterns, soil chemistry and climatic regimes. Such a straight-forward linkage between Hg and organic matter greatly facilitates the parameterisation of watershed models for assessing the biogeochemical fate, toxic effect and critical level of atmospheric Hg input to forest soils.
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