Managing Swedish forestry’s impact on mercury in fish: Defining the impact and mitigation measures

Eklöf, Karin; Lidskog, Rolf; Bishop, Kevin

doi:10.1007/s13280-015-0752-7

Cited by 55 publications

(48 citation statements)

References 49 publications

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“…For example, decreased evapotranspiration can lead to an elevated water table, increased soil moisture, and ponding, all of which foster anoxic conditions favorable for methylation (Munthe and Hultberg 2004 ; Braaten and de Wit 2016 ; Kronberg et al 2016a ). Furthermore, fresh organic carbon inputs from logging debris left on the site may enhance microbial activity and MeHg production (Eklof et al 2016 ; Kronberg et al 2016a ). However, increased MeHg concentrations in streamwater draining harvested watersheds have only been clearly observed in some studies (Porvari et al 2003 ; Skyllberg et al 2009 ; Eklof et al 2012 ), whereas others have shown no significant change in MeHg response to forestry operations (Allan et al 2009 ; Eklof et al 2013 ; de Wit et al 2014 ; Kronberg et al 2016a ).…”

Section: Forestry and Deforestationmentioning

confidence: 99%

Challenges and opportunities for managing aquatic mercury pollution in altered landscapes

Hsu‐Kim

Eckley

Achá

et al. 2018

Ambio

201

115

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The environmental cycling of mercury (Hg) can be affected by natural and anthropogenic perturbations. Of particular concern is how these disruptions increase mobilization of Hg from sites and alter the formation of monomethylmercury (MeHg), a bioaccumulative form of Hg for humans and wildlife. The scientific community has made significant advances in recent years in understanding the processes contributing to the risk of MeHg in the environment. The objective of this paper is to synthesize the scientific understanding of how Hg cycling in the aquatic environment is influenced by landscape perturbations at the local scale, perturbations that include watershed loadings, deforestation, reservoir and wetland creation, rice production, urbanization, mining and industrial point source pollution, and remediation. We focus on the major challenges associated with each type of alteration, as well as management opportunities that could lessen both MeHg levels in biota and exposure to humans. For example, our understanding of approximate response times to changes in Hg inputs from various sources or landscape alterations could lead to policies that prioritize the avoidance of certain activities in the most vulnerable systems and sequestration of Hg in deep soil and sediment pools. The remediation of Hg pollution from historical mining and other industries is shifting towards in situ technologies that could be less disruptive and less costly than conventional approaches. Contemporary artisanal gold mining has well-documented impacts with respect to Hg; however, significant social and political challenges remain in implementing effective policies to minimize Hg use. Much remains to be learned as we strive towards the meaningful application of our understanding for stakeholders, including communities living near Hg-polluted sites, environmental policy makers, and scientists and engineers tasked with developing watershed management solutions. Site-specific assessments of MeHg exposure risk will require new methods to predict the impacts of anthropogenic perturbations and an understanding of the complexity of Hg cycling at the local scale.Electronic supplementary materialThe online version of this article (10.1007/s13280-017-1006-7) contains supplementary material, which is available to authorized users.

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Section: Forestry and Deforestationmentioning

confidence: 99%

Challenges and opportunities for managing aquatic mercury pollution in altered landscapes

Hsu‐Kim

Eckley

Achá

et al. 2018

Ambio

201

115

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“…Off-road driving with heavy machines can cause wet soils to deform and displace resulting in deeper tracks and larger soil disturbance than on dry soils where shallower tracks are caused by compaction. Forestry conducted close to streams and lakes has been shown to increase the export of mercury (Eklöf et al 2016) and nutrients (Kreutzweiser et al 2008) to downstream environments (Kuglerová et al 2014). Soil damage in riparian zones can also lead to erosion from ruts and subsequent sediment deposition burying important spawning habitats (Kreutzweiser and Capell 2001).…”

Section: Introductionmentioning

confidence: 99%

Using machine learning to generate high-resolution wet area maps for planning forest management: A study in a boreal forest landscape

Lidberg

Nilsson

Ågren

2019

Ambio

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Comparisons between field data and available maps show that 64% of wet areas in the boreal landscape are missing on current maps. Primarily forested wetlands and wet soils near streams and lakes are missing, making them difficult to manage. One solution is to model missing wet areas from high-resolution digital elevation models, using indices such as topographical wetness index and depth to water. However, when working across large areas with gradients in topography, soils and climate, it is not possible to find one method or one threshold that works everywhere. By using soil moisture data from the National Forest Inventory of Sweden as a training dataset, we show that it is possible to combine information from several indices and thresholds, using machine learners, thereby improving the mapping of wet soils (kappa = 0.65). The new maps can be used to better plan roads and generate riparian buffer zones near surface waters.

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“…To mitigate stimulatory effects of forest harvest on MeHg formation and stream export, adjustment of forest management practices have been suggested, such as leaving zones of gallery forest along streams and avoiding soil disturbance and compaction by heavy machinery. 19,34 However, before such actions can be fully designed and implemented we need to better understand processes and factors in control of MeHg formation in forest soil (before and after harvest) and the spatial distribution of MeHg net producing "hot-spots" and their connections to…”

Section: Introductionmentioning

confidence: 99%

Methyl Mercury Formation in Hillslope Soils of Boreal Forests: The Role of Forest Harvest and Anaerobic Microbes

Kronberg

Jiskra²,

Wiederhold³

et al. 2016

Environ. Sci. Technol.

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Final harvest (clear-cutting) of coniferous boreal forests has been shown to increase streamwater concentrations and export of the neurotoxin methyl mercury (MeHg) to freshwater ecosystems. Here, the spatial distribution of inorganic Hg and MeHg in soil as a consequence of clear-cutting is reported. A comparison of soils at similar positions along hillslopes in four 80 years old Norway spruce (Picea abies) stands (REFs) with those in four similar stands subjected to clear-cutting (CCs) revealed significantly (p < 0.05) enhanced MeHg concentrations (ng g(-1)), MeHg areal masses (g ha(-1)), and percent MeHg of HgTOT in O horizons of CCs located between 1 and 41 m from streams. Inorganic Hg measures did not differ between REFs and CCs at any position. The O horizon thickness did not differ between CCs and REFs, but the groundwater table and soil water content were significantly higher at CCs than at REFs. The largest difference in percent MeHg of HgTOT (12 times higher at CCs compared to REFs, p = 0.003) was observed in concert with a significant enhancement in soil water content (p = 0.0003) at intermediate hillslope positions (20-38 m from stream), outside the stream riparian zone. Incubation experiments demonstrated that soils having significantly enhanced soil pools of MeHg after clear-cutting also showed significantly enhanced methylation potential as compared with similarly positioned soils in mature reference stands. The addition of inhibitors demonstrated that sulfate-reducing bacteria (SRB) and methanogens were key methylators. Rates of demethylation did not differ between CCs and REFs. Our results suggest that enhanced water saturation of organic soils providing readily available electron donors stimulate Hg-methylating microbes to net formation and buildup of MeHg in O horizons after forest harvest.

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Managing Swedish forestry’s impact on mercury in fish: Defining the impact and mitigation measures

Cited by 55 publications

References 49 publications

Challenges and opportunities for managing aquatic mercury pollution in altered landscapes

Challenges and opportunities for managing aquatic mercury pollution in altered landscapes

Using machine learning to generate high-resolution wet area maps for planning forest management: A study in a boreal forest landscape

Methyl Mercury Formation in Hillslope Soils of Boreal Forests: The Role of Forest Harvest and Anaerobic Microbes

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