2 research outputs found
Metal Mobilization by Iron- and Sulfur-Oxidizing Bacteria in a Multiple Extreme Mine Tailings in the Atacama Desert, Chile
The marine shore sulfidic mine tailings dump at the Chañaral
Bay in the Atacama Desert, northern Chile, is characterized by extreme
acidity, high salinity, and high heavy metals concentrations. Due
to pyrite oxidation, metals (especially copper) are mobilized under
acidic conditions and transported toward the tailings surface and
precipitate as secondary minerals (Dold, <i>Environ. Sci. Technol</i>. <b>2006</b>, <i>40</i>, 752–758.). Depth
profiles of total cell counts in this almost organic-carbon free multiple
extreme environment showed variable numbers with up to 10<sup>8</sup> cells g<sup>–1</sup> dry weight for 50 samples at four sites.
Real-time PCR quantification and bacterial 16S rRNA gene diversity
analysis via clone libraries revealed a dominance of <i>Bacteria</i> over <i>Archaea</i> and the frequent occurrence of the
acidophilic ironÂ(II)- and sulfur-oxidizing and ironÂ(III)-reducing
genera <i>Acidithiobacillus</i>, <i>Alicyclobacillus</i>, and <i>Sulfobacillus.</i> Acidophilic chemolithoautotrophic
ironÂ(II)-oxidizing bacteria were also frequently found via most-probable-number
(MPN) cultivation. Halotolerant ironÂ(II)-oxidizers in enrichment cultures
were active at NaCl concentrations up to 1 M. Maximal microcalorimetrically
determined pyrite oxidation rates coincided with maxima of the pyrite
content, total cell counts, and MPN of ironÂ(II)-oxidizers. These findings
indicate that microbial pyrite oxidation and metal mobilization preferentially
occur in distinct tailings layers at high salinity. Microorganisms
for biomining with seawater salt concentrations obviously exist in
nature
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 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 × 10<sup>9</sup> g DFe
yr<sup>–1</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 × 10<sup>9</sup> g DFe yr<sup>–1</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