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Mercury in tundra vegetation of Alaska: Spatial and temporal dynamics and stable isotope patterns.

https://arctichealth.org/en/permalink/ahliterature299087
Source
Sci Total Environ. 2019 Apr 10; 660:1502-1512
Publication Type
Journal Article
Date
Apr-10-2019
Author
Christine L Olson
Martin Jiskra
Jeroen E Sonke
Daniel Obrist
Author Affiliation
Division of Atmospheric Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA.
Source
Sci Total Environ. 2019 Apr 10; 660:1502-1512
Date
Apr-10-2019
Language
English
Publication Type
Journal Article
Keywords
Alaska
Climate change
Lichens - chemistry
Mercury - analysis - chemistry
Mercury Isotopes - analysis - chemistry
Soil Pollutants - analysis
Tundra
Abstract
Vegetation uptake of atmospheric mercury (Hg) is an important mechanism enhancing atmospheric Hg deposition via litterfall and senescence. We here report Hg concentrations and pool sizes of different plant functional groups and plant species across nine tundra sites in northern Alaska. Significant spatial differences were observed in bulk vegetation Hg concentrations at Toolik Field station (52?±?9?µg?kg-1), Eight Mile Lake Observatory (40?±?0.2?µg?kg-1), and seven sites along a transect from Toolik Field station to the Arctic coast (36?±?9?µg?kg-1). Hg concentrations in non-vascular vegetation including feather and peat moss (58?±?6?µg?kg-1 and 34?±?2?µg?kg-1, respectively) and brown and white lichen (41?±?2?µg?kg-1 and 34?±?2?µg?kg-1, respectively), were three to six times those of vascular plant tissues (8?±?1?µg?kg-1 in dwarf birch leaves and 9?±?1?µg?kg-1 in tussock grass). A high representation of nonvascular vegetation in aboveground biomass resulted in substantial Hg mass contained in tundra aboveground vegetation (29?µg?m-2), which fell within the range of foliar Hg mass estimated for forests in the United States (15 to 45?µg?m-2) in spite of much shorter growing seasons. Hg stable isotope signatures of different plant species showed that atmospheric Hg(0) was the dominant source of Hg to tundra vegetation. Mass-dependent isotope signatures (d202Hg) in vegetation relative to atmospheric Hg(0) showed pronounced shifts towards lower values, consistent with previously reported isotopic fractionation during foliar uptake of Hg(0). Mass-independent isotope signatures (?199Hg) of lichen were more positive relative to atmospheric Hg(0), indicating either photochemical reduction of Hg(II) or contributions of inorganic Hg(II) from atmospheric deposition and/or dust. ?199Hg and ?200Hg values in vascular plant species were similar to atmospheric Hg(0) suggesting that overall photochemical reduction and subsequent re-emission was relatively insignificant in these tundra ecosystems, in agreement with previous Hg(0) ecosystem flux measurements.
PubMed ID
30743942 View in PubMed
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Mercury in tundra vegetation of Alaska: Spatial and temporal dynamics and stable isotope patterns.

https://arctichealth.org/en/permalink/ahliterature298184
Source
Sci Total Environ. 2019 Apr 10; 660:1502-1512
Publication Type
Journal Article
Date
Apr-10-2019
Author
Christine L Olson
Martin Jiskra
Jeroen E Sonke
Daniel Obrist
Author Affiliation
Division of Atmospheric Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA.
Source
Sci Total Environ. 2019 Apr 10; 660:1502-1512
Date
Apr-10-2019
Language
English
Publication Type
Journal Article
Abstract
Vegetation uptake of atmospheric mercury (Hg) is an important mechanism enhancing atmospheric Hg deposition via litterfall and senescence. We here report Hg concentrations and pool sizes of different plant functional groups and plant species across nine tundra sites in northern Alaska. Significant spatial differences were observed in bulk vegetation Hg concentrations at Toolik Field station (52?±?9?µg?kg-1), Eight Mile Lake Observatory (40?±?0.2?µg?kg-1), and seven sites along a transect from Toolik Field station to the Arctic coast (36?±?9?µg?kg-1). Hg concentrations in non-vascular vegetation including feather and peat moss (58?±?6?µg?kg-1 and 34?±?2?µg?kg-1, respectively) and brown and white lichen (41?±?2?µg?kg-1 and 34?±?2?µg?kg-1, respectively), were three to six times those of vascular plant tissues (8?±?1?µg?kg-1 in dwarf birch leaves and 9?±?1?µg?kg-1 in tussock grass). A high representation of nonvascular vegetation in aboveground biomass resulted in substantial Hg mass contained in tundra aboveground vegetation (29?µg?m-2), which fell within the range of foliar Hg mass estimated for forests in the United States (15 to 45?µg?m-2) in spite of much shorter growing seasons. Hg stable isotope signatures of different plant species showed that atmospheric Hg(0) was the dominant source of Hg to tundra vegetation. Mass-dependent isotope signatures (d202Hg) in vegetation relative to atmospheric Hg(0) showed pronounced shifts towards lower values, consistent with previously reported isotopic fractionation during foliar uptake of Hg(0). Mass-independent isotope signatures (?199Hg) of lichen were more positive relative to atmospheric Hg(0), indicating either photochemical reduction of Hg(II) or contributions of inorganic Hg(II) from atmospheric deposition and/or dust. ?199Hg and ?200Hg values in vascular plant species were similar to atmospheric Hg(0) suggesting that overall photochemical reduction and subsequent re-emission was relatively insignificant in these tundra ecosystems, in agreement with previous Hg(0) ecosystem flux measurements.
PubMed ID
30743942 View in PubMed
Less detail

Tundra uptake of atmospheric elemental mercury drives Arctic mercury pollution.

https://arctichealth.org/en/permalink/ahliterature283905
Source
Nature. 2017 Jul 12;547(7662):201-204
Publication Type
Article
Date
Jul-12-2017
Author
Daniel Obrist
Yannick Agnan
Martin Jiskra
Christine L Olson
Dominique P Colegrove
Jacques Hueber
Christopher W Moore
Jeroen E Sonke
Detlev Helmig
Source
Nature. 2017 Jul 12;547(7662):201-204
Date
Jul-12-2017
Language
English
Publication Type
Article
Abstract
Anthropogenic activities have led to large-scale mercury (Hg) pollution in the Arctic. It has been suggested that sea-salt-induced chemical cycling of Hg (through 'atmospheric mercury depletion events', or AMDEs) and wet deposition via precipitation are sources of Hg to the Arctic in its oxidized form (Hg(ii)). However, there is little evidence for the occurrence of AMDEs outside of coastal regions, and their importance to net Hg deposition has been questioned. Furthermore, wet-deposition measurements in the Arctic showed some of the lowest levels of Hg deposition via precipitation worldwide, raising questions as to the sources of high Arctic Hg loading. Here we present a comprehensive Hg-deposition mass-balance study, and show that most of the Hg (about 70%) in the interior Arctic tundra is derived from gaseous elemental Hg (Hg(0)) deposition, with only minor contributions from the deposition of Hg(ii) via precipitation or AMDEs. We find that deposition of Hg(0)-the form ubiquitously present in the global atmosphere-occurs throughout the year, and that it is enhanced in summer through the uptake of Hg(0) by vegetation. Tundra uptake of gaseous Hg(0) leads to high soil Hg concentrations, with Hg masses greatly exceeding the levels found in temperate soils. Our concurrent Hg stable isotope measurements in the atmosphere, snowpack, vegetation and soils support our finding that Hg(0) dominates as a source to the tundra. Hg concentration and stable isotope data from an inland-to-coastal transect show high soil Hg concentrations consistently derived from Hg(0), suggesting that the Arctic tundra might be a globally important Hg sink. We suggest that the high tundra soil Hg concentrations might also explain why Arctic rivers annually transport large amounts of Hg to the Arctic Ocean.
PubMed ID
28703199 View in PubMed
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