Astrobiology December 2007, 7(6): 971-986
http://www.liebertonline.com/doi/pdfplus/10.1089/ast.2006.0096
Dissolved H2 concentrations up to the mM range and H2 levels up to 9-58% by volume in the free gas phase are reported for groundwaters at sites in the Precambrian shields of Canada and Finland. Along with previously reported dissolved H2 concentrations up to 7.4 mM for groundwaters from the Witwatersrand Basin, South Africa, these findings indicate that deep Precambrian Shield fracture waters contain some of the highest levels of dissolved H2 ever reported and represent a potentially important energy-rich environment for subsurface microbial life. The
