eCite Digital Repository
Mercury in the Southern Ocean
Citation
Cossa, D and Heimburger, LE and Lannuzel, D and Rintoul, SR and Butler, ECV and Bowie, AR and Averty, B and Watson, RJ and Remenyi, TA, Mercury in the Southern Ocean, Geochimica Et Cosmochimica Acta, 75, (14) pp. 4037-4052. ISSN 0016-7037 (2011) [Refereed Article]
![]() | PDF Restricted - Request a copy 969Kb |
Copyright Statement
Copyright © 2011 Elsevier Ltd
DOI: doi:10.1016/j.gca.2011.05.001
Abstract
We present here the first mercury speciation study in the water column of the Southern Ocean, using a high-resolution
south-to-north section (27 stations from 65.50!S to 44.00!S) with up to 15 depths (0–4440 m) between Antarctica and
Tasmania (Australia) along the 140!E meridian. In addition, in order to explore the role of sea ice in Hg cycling, a study
of mercury speciation in the "snow–sea ice–seawater" continuum was conducted at a coastal site, near the Australian
Casey station (66.40!S; 101.14!E). In the open ocean waters, total Hg (HgT) concentrations varied from 0.63 to
2.76 pmol L!1 with "transient-type" vertical profiles and a latitudinal distribution suggesting an atmospheric mercury
source south of the Southern Polar Front (SPF) and a surface removal north of the Subantartic Front (SAF). Slightly
higher mean HgT concentrations (1.35 ± 0.39 pmol L!1) were measured in Antarctic Bottom Water (AABW) compared to
Antarctic Intermediate water (AAIW) (1.15 ± 0.22 pmol L!1). Labile Hg (HgR) concentrations varied from 0.01 to
2.28 pmol L!1, with a distribution showing that the HgT enrichment south of the SPF consisted mainly of HgR
(67 ± 23%), whereas, in contrast, the percentage was half that in surface waters north of PFZ (33 ± 23%). Methylated
mercury species (MeHgT) concentrations ranged from 0.02 to 0.86 pmol L!1. All vertical MeHgT profiles exhibited
roughly the same pattern, with low concentrations observed in the surface layer and increasing concentrations with depth
up to an intermediate depth maximum. As for HgT, low mean MeHgT concentrations were associated with AAIW, and
higher ones with AABW. The maximum of MeHgT concentration at each station was systematically observed within the
oxygen minimum zone, with a statistically significant MeHgT vs Apparent Oxygen Utilization (AOU) relationship
(p < 0.001). The proportion of HgT as methylated species was lower than 5% in the surface waters, around 50% in deep
waters below 1000 m, reaching a maximum of 78% south of the SPF. At Casey coastal station HgT and HgR concentrations
found in the "snow–sea ice–seawater" continuum were one order of magnitude higher than those measured in open
ocean waters. The distribution of HgT there suggests an atmospheric Hg deposition with snow and a fractionation process
during sea ice formation, which excludes Hg from the ice with a parallel Hg enrichment of brine, probably concurring
with the Hg enrichment of AABW observed in the open ocean waters. Contrastingly, MeHgT concentrations in the
sea ice environment were in the same range as in the open ocean waters, remaining below 0.45 pmol L!1. The MeHgT
vertical profile through the continuum suggests different sources, including atmosphere, seawater and methylation in basal
ice. Whereas HgT concentrations in the water samples collected between the Antarctic continent and Tasmania are comparable to recent measurements made in the other parts of the World Ocean (e.g., Soerensen et al., 2010), the Hg
species distribution suggests distinct features in the Southern Ocean Hg cycle: (i) a net atmospheric Hg deposition on
surface water near the ice edge, (ii) the Hg enrichment in brine during sea ice formation, and (iii) a net methylation
of Hg south of the SPF.
Item Details
Item Type: | Refereed Article |
---|---|
Research Division: | Environmental Sciences |
Research Group: | Ecological applications |
Research Field: | Ecosystem function |
Objective Division: | Environmental Policy, Climate Change and Natural Hazards |
Objective Group: | Understanding climate change |
Objective Field: | Effects of climate change on Antarctic and sub-Antarctic environments (excl. social impacts) |
UTAS Author: | Lannuzel, D (Associate Professor Delphine Lannuzel) |
UTAS Author: | Rintoul, SR (Dr Steve Rintoul) |
UTAS Author: | Butler, ECV (Dr Edward Butler) |
UTAS Author: | Bowie, AR (Professor Andrew Bowie) |
UTAS Author: | Remenyi, TA (Dr Tom Remenyi) |
ID Code: | 72217 |
Year Published: | 2011 |
Web of Science® Times Cited: | 179 |
Deposited By: | IMAS Research and Education Centre |
Deposited On: | 2011-08-24 |
Last Modified: | 2012-05-24 |
Downloads: | 2 View Download Statistics |
Repository Staff Only: item control page