Chemical Contaminants from the Drilling and Sampling Equipment

Chemical contaminants from drilling and sampling equipment will depend on the composition of the equipment, its fabrication history, and cleaning protocols prior to use. Machine oils (cutting fluids) are routinely used in metal working to cool the cutting tools and to wash away the metal filings (http://www.mfg.mtu.edu/testbeds/cfest/ fluid.html#cfintro_name). They may be mixed with lubricants and typically contain many additives including hydroxyalkylamines as emulsifiers, chlorinated paraffins to control viscosity, corrosion inhibitors such as sodium nitrite, and biocides to prevent microbial growth. The addition of nitrites can result in the production of toxic N-nitroso compounds (nitrosamines) such as nitrosodiethanolamine (NDELA), which can occur in high concentration in water-based cutting fluids. The detection limit for NDELA and other nitrosamines in aqueous systems is 20 pg by GC-MS (Wigfield et al. 1988).

Phthalate esters are widely used as plasticizers in polyvinyl chloride (PVC), polyvinyl acetates, cellulosics, and polyurethanes. Their solubility in water varies by orders of magnitude depending on the length of their alkyl chain. A large collection of literature exists on their distribution and bioaccumulation throughout the environment. Limits of detection vary with the method applied and can be less than 50 ng L−1 in water using solid phase extraction (Staples 2003).

Rubber hosing has the potential to release a variety of contaminants. For example, styrene, used in the synthetic rubber industry and in the production of other polymers, is required to be monitored in U.S. drinking water supplies if levels exceed 500 ng L−1 (http://www.freedrinkingwater.com/water-contamination/styrene-contaminants-removal-water.htm).

POTENTIAL SOURCES OF BIOLOGICAL CONTAMINATION

Any form of invasive sampling of a subglacial lake will result in some level of perturbation to the environment in question. Since many of the subglacial aquatic environments are likely to contain a low biomass of microbes it is of critical importance to minimize the introduction of exogenous microbes, whether living or dead, and even of exogenous nucleic acids to (1) prevent changes in the native microbial composition and (2) allow for proper investigation of the native microbial community (and not contaminants) of the subglacial lake environment.

Potentially, a variety of allochthonous microbes (“contaminants”) could be introduced into subglacial lake environments via drilling and sampling activities. These allochthonous microbes may include microorganisms native to the surface environment or introduced from humans or equipment brought to the sampling area. Microbes immured in glacial ice for long periods of time might conceivably proliferate once they are released back into the modern-day biosphere through natural melting processes or through research activities. The majority of this release is likely to be of prokaryotic organisms, although possible introduction of microeukaryotes and viruses cannot be discounted (e.g., Rogers et al. 2004; Smith et al. 2004). For example, tomato mosaic virus, a member of the highly stable tobamovirus group, has been isolated from decontaminated Greenland ice cores ranging in age from <500 to 140,000 years before the present (Castello et al. 2005). Human and animal pathogens are also likely to be present in glaciers and ice sheets (Shoham 2005). Even if these microbes and pathogens



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