Impact of Forestry on Total and Methyl-Mercury in Surface Waters: Distinguishing Effects of Logging and Site Preparation

Eklöf, Karin; Schelker, Jakob; Sørensen, Rasmus; Meili, Markus; Laudon, Hjalmar; Brömssen, Claudia von; Bishop, Kevin

doi:10.1021/es404879p

Cited by 59 publications

(66 citation statements)

References 45 publications

(103 reference statements)

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“…In Table all studies reporting MeHg/DOC ratios after clear‐cutting are listed. Our reported average MeHg/DOC ratios for the 10 REFs (0.014 g g −1 above and 0.016 g g −1 below the ML) are similar to the average for Boreal coniferous forest reference stands (0.015 g g −1 , Table ) reported by Eklöf et al [] and de Wit et al []. In these two studies clear‐cutting only had minor effects on the MeHg/DOC ratio in the former and no effect in the latter study.…”

Section: Discussionsupporting

confidence: 87%

“…At a site from mid‐Sweden situated at a similar altitude (295–444 MASL) above the ML and with similar types of coniferous forest ( Picea abies and Pinus silvestris ) and topography as our sites, the runoff increased by 85% and 110% (220 and 274 mm yr −1 ) as an average over 8 years after final harvest when 50 and 95% of the watershed area were clear‐cut, respectively [ Rosén et al , ]. At another similar site in northern Sweden, also situated above the ML, the runoff increased by 47% 1–3 years after clear‐cutting 64% of a catchment with mixed Picea abies and Pinus silvestris stands and by 11% 1–3 years after clear‐cutting 35% of another similar catchment [ Eklöf et al , ]. Site preparation (soil scarification) and planting did not have any additional effect on runoff compared to logging.…”

Section: Discussionmentioning

confidence: 99%

“…The effect of coniferous forest clear‐cutting on DOC export has been reported to increase by 47 to 79% (as related to nonharvested reference stands) [ Schelker et al , ; Eklöf et al , ]. In both studies sites were situated above the ML in north‐central Sweden.…”

Section: Discussionmentioning

confidence: 99%

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Forest harvest contribution to Boreal freshwater methyl mercury load

Kronberg

Drott

Jiskra

et al. 2016

Global Biogeochemical Cycles

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Effects of Boreal forest harvest on mercury (Hg) and methyl mercury (MeHg) soil pools and export by stream runoff were quantified by comparing 10 reference watersheds (REFs) covered by >80 year old Norway spruce (Picea abies Karst.) forests with 10 similar watersheds subjected to clear-cutting (CCs). While total Hg soil storage did not change, MeHg pools increased seven times (p = 0.006) in the organic topsoil 2 years after clear-cutting. In undulating terrain, situated above the postglacial marine limit (ML) of the ancient Baltic Sea, the mass ratio between flux-weighted MeHg and dissolved organic carbon (MeHg/DOC) in stream runoff increased 1.8 times (p < 0.004) as a consequence of forest harvest. When recalculated to 100% clear-cutting of the watershed, the annual MeHg stream export increased 3.8 times (p = 0.047). Below the ML, where the terrain was flatter, neither the MeHg/DOC ratio nor the annual export of MeHg differed between REFs and CCs, likely because of the larger contribution of MeHg exported from peaty soils and small wetlands. The most robust measure, MeHg/DOC, was used to calculate MeHg loadings to Boreal headwaters. If the forest harvest effect lasts 10 years, clear-cutting increases MeHg runoff by 12-20% in Sweden and 2% in the Boreal zone as a whole. In Sweden, having intensely managed forests, 37% and 56% of MeHg are exported from peatlands and forest soils, respectively, and forest clear-cutting is adding another 6.6%. In the Boreal zone as a whole peatlands and forests soils contribute with 53% and 46%, respectively, and clearcutting is estimated to add another 1.0%. An expected rapid increase in Boreal forest harvest and disturbance urge for inclusion of land use effects in mercury biogeochemical cycling models at different scales.

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Section: Discussionsupporting

confidence: 87%

Section: Discussionmentioning

confidence: 99%

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Forest harvest contribution to Boreal freshwater methyl mercury load

Kronberg

Drott

Jiskra

et al. 2016

Global Biogeochemical Cycles

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“…For example, practices used in forestry are known to cause increased erosion and changed hydrological pathways and yield through the catchment soils, resulting in increased transport of Hg [66,67,68,69]. These processes are even more pronounced when forest is converted to agricultural land use, exposing the mineral soil horizon thus enhancing and accelerating Hg leaching [70].…”

Section: Resultsmentioning

confidence: 99%

Toward an Assessment of the Global Inventory of Present-Day Mercury Releases to Freshwater Environments

Kocman

Wilson

Amos

et al. 2017

IJERPH

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Aquatic ecosystems are an essential component of the biogeochemical cycle of mercury (Hg), as inorganic Hg can be converted to toxic methylmercury (MeHg) in these environments and reemissions of elemental Hg rival anthropogenic Hg releases on a global scale. Quantification of effluent Hg releases to aquatic systems globally has focused on discharges to the global oceans, rather than contributions to freshwater systems that affect local exposures and risks associated with MeHg. Here we produce a first-estimate of sector-specific, spatially resolved global aquatic Hg discharges to freshwater systems. We compare our release estimates to atmospheric sources that have been quantified elsewhere. By analyzing available quantitative and qualitative information, we estimate that present-day global Hg releases to freshwater environments (rivers and lakes) associated with anthropogenic activities have a lower bound of ~1000 Mg·a−1. Artisanal and small-scale gold mining (ASGM) represents the single largest source, followed by disposal of mercury-containing products and domestic waste water, metal production, and releases from industrial installations such as chlor-alkali plants and oil refineries. In addition to these direct anthropogenic inputs, diffuse inputs from land management activities and remobilization of Hg previously accumulated in terrestrial ecosystems are likely comparable in magnitude. Aquatic discharges of Hg are greatly understudied and further constraining associated data gaps is crucial for reducing the uncertainties in the global biogeochemical Hg budget.

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“…combination with increased water levels and standing water pooling in the tracks (Eklöf et al, 2014).…”

Section: A M åGren Et Al: Evaluating Digital Terrain Indices For Smentioning

confidence: 99%

Evaluating digital terrain indices for soil wetness mapping – a Swedish case study

Ågren

Lidberg

Strömgren

et al. 2014

Hydrol. Earth Syst. Sci.

136

117

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Abstract. Trafficking wet soils within and near stream and lake buffers can cause soil disturbances, i.e. rutting and compaction. This -in turn -can lead to increased surface flow, thereby facilitating the leaking of unwanted substances into downstream environments. Wet soils in mires, near streams and lakes have particularly low bearing capacity and are therefore more susceptible to rutting. It is therefore important to model and map the extent of these areas and associated wetness variations. This can now be done with adequate reliability using a high-resolution digital elevation model (DEM). In this article, we report on several digital terrain indices to predict soil wetness by wet-area locations. We varied the resolution of these indices to test what scale produces the best possible wet-areas mapping conformance. We found that topographic wetness index (T WI ) and the newly developed cartographic depth-to-water index (D TW ) were the best soil wetness predictors. While the T WI derivations were sensitive to scale, the D TW derivations were not and were therefore numerically robust. Since the D TW derivations vary by the area threshold for setting stream flow initiation, we found that the optimal threshold values for permanently wet areas varied by landform within the Krycklan watershed, e.g. 1-2 ha for till-derived landforms versus 8-16 ha for a coarsetextured alluvial floodplain.

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Impact of Forestry on Total and Methyl-Mercury in Surface Waters: Distinguishing Effects of Logging and Site Preparation

Cited by 59 publications

References 45 publications

Forest harvest contribution to Boreal freshwater methyl mercury load

Forest harvest contribution to Boreal freshwater methyl mercury load

Toward an Assessment of the Global Inventory of Present-Day Mercury Releases to Freshwater Environments

Evaluating digital terrain indices for soil wetness mapping – a Swedish case study

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