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, 2009–2011, we examined three sites on the South Shetland Islands in Antarctica. Two of them displayed intensive sulfide mineralization and generated acidic (pH 3.2–4.5), iron-rich drainage waters (up to 1.78 mM Fe), which infiltrated as groundwater (as Fe2+) and as superficial runoff (as Fe3+) 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 Acidithiobacillus ferrivorans and Thiobacillus plumbophilus. The dissolved iron (DFe) flux from rock weathering (nonmineralized control site) was calculated to be 0.45 × 109 g DFe yr–1 for the nowadays 5468 km of ice-free Antarctic rock coastline which is of the same order of...