1 research outputs found
Acid Rock Drainage and Rock Weathering in Antarctica: Important Sources for Iron Cycling in the Southern Ocean
Here we describe
biogeochemical processes that lead to the generation
of acid rock drainage (ARD) and rock weathering on the Antarctic landmass
and describe why they are important sources of iron into the Antarctic
Ocean. During three expeditions, 2009โ2011, we examined three
sites on the South Shetland Islands in Antarctica. Two of them displayed
intensive sulfide mineralization and generated acidic (pH 3.2โ4.5),
iron-rich drainage waters (up to 1.78 mM Fe), which infiltrated as
groundwater (as Fe<sup>2+</sup>) and as superficial runoff (as Fe<sup>3+</sup>) into the sea, the latter with the formation of schwertmannite
in the sea-ice. The formation of ARD in the Antarctic was catalyzed
by acid mine drainage microorganisms found in cold climates, including <i>Acidithiobacillus ferrivorans</i> and <i>Thiobacillus plumbophilus</i>. The dissolved iron (DFe) flux from rock weathering (nonmineralized
control site) was calculated to be 0.45 ร 10<sup>9</sup> g DFe
yr<sup>โ1</sup> for the nowadays 5468 km of ice-free Antarctic
rock coastline which is of the same order of magnitude as glacial
or aeolian input to the Southern Ocean. Additionally, the two ARD
sites alone liberate 0.026 and 0.057 ร 10<sup>9</sup> g DFe yr<sup>โ1</sup> as point sources to the sea. The increased iron input
correlates with increased phytoplankton production close to the source.
This might even be enhanced in the future by a global warming scenario,
and could be a process counterbalancing global warming