By tracing the abundance and distribution of bacteria in an abandoned California mine, scientists may have found a better way to predict the potential environmental consequences of mining metal ores.
Writing this week (March 6) in the journal Science, a team of University of Wisconsin-Madison scientists presents the first in situ, molecular-level ecological study of the naturally occurring microbes that mediate some of the most severe pollution events associated with sulfide mining. The findings could provide the mining industry and others with a new predictive technology, one capable of estimating acid mine drainage from a given site.
Acid mine drainage is the flow of sulfuric acid into ground and surface water from metallic-ore mines. In addition to contributing sulfuric acid to nearby water supplies, the sulfuric acid itself facilitates the release and suspension of heavy metals into water, one of the most vexing consequences of sulfide mining.
In nature, minerals exposed to oxygen and water form sulfuric acid. Around mines, an abundance of minerals is exposed to the surface in tailings and the exposed surfaces of ore bodies, and they oxidize naturally. But contributing to the process are naturally-occurring bacteria which, like tiny factories, greatly accelerate the rate of oxidation. The bacteria are widely considered to be the microorganisms that control the production rate of acid mine drainage.
Knowing precisely where and under what conditions the microbes thrive in nature can be a powerful new tool to predict the effects of sulfide mining at a given site, said Katrina J. Edwards, a UW-Madison graduate student and a co-author of the study.
Prior to the new study, conducted at Iron Mountain, Calif., an abandoned and heavily polluted iron mine, two species of bacteria, Thiobacillus ferrooxidans and Leptospirillum ferrooxidans, were believed to be the primary microbial culprits involved in accelerating acid mine drainage.