Cryogenic core collection and preservation of subsurface samples for biomolecular analysis

A cryogenic coring system for the collection and preservation of biomolecules in unconsolidated subsurface solid samples is presented here. The sampler is based on existing direct-push coring technology, with the addition of a cryogenic step to freeze the sample in situ. Once brought to the surface, the frozen cores can be packed in dry ice and shipped to the laboratory for further processing and analysis. The approach prevents redistribution of fluids during sample recovery and shipping, and because the cores are frozen in situ there is little loss of solid material during retrieval to ground surface. To evaluate the performance of the approach, DNA analyses of samples collected by cryogenic coring in a very large physical model are compared with results from water samples and horizontal core samples taken in close proximity. The data indicate that the vertical distribution of DNA within the cryogenic core can be measured at the centimeter scale, providing unprecedented characterization of subsurface biogeochemical interfaces.