Anaerobic subsurface environments, microbial

Given the low concentrations of oxygen in the subsurface environment, along with its poor solubility and poor mass-transfer efficiency, anaerobic treatment is an attractive alternative, provided that it is biologically possible. Studies by other researchers and in our own laboratory indicate that nitrate is an electron acceptor that can satisfactorily substitute for oxygen in microbially mediated processes and allow the degradation of a number of components of BTX (40-43). 

Francis AJ. 1985. Anaerobic microbial dissolution of toxic metals in subsurface environments. Upton,... 

Constructed wetlands (CWs) can promote removal of PhCs through a number of different mechanisms, including photolysis, plant uptake, microbial degradation and sorption to the soil. The main benefits of horizontal and vertical subsurface flow systems are the existence of aerobic, anaerobic and anoxic redox conditions in proximity to plant rhizomes this provides an ideal environment for reducing... 

Ward, T.E. (1985) Characterizing the aerobic and anaerobic microbial activities in surface and subsurface soils. Environ Toxicol. Chem. 4, 727-737. 

In addition to dilution of acid rock/mine drainage under oxidizing conditions, neutralization can occur under mildly or highly anaerobic conditions. This will create distinctive environments in which microorganisms thrive and nanoparticles form as a result of their activity. We describe two examples of such subsurface systems below. However, before turning to these topics, we note that Fe-based microbial ecosystems are not only found in association with metal sulfide deposits, but may be broadly relevant in the subsurface where Fe-rich minerals (biotite, olivine, pyroxenes, etc.) are present in reasonable abundance and dissolve, releasing aqueous ferrous iron. 

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