A Sampling Device for Collection of Ground Water Bacteria under Natural Gradient Flow Conditions

Abstract

AbstractA passive sampler was tested for the purpose of collecting ground water bacteria under natural gradient conditions. Samples were collected within a series of dual‐port dialysis cells (originally containing sterile water) mounted within a length of polyvinyl chloride pipe that was suspended within the center of the screened interval of a monitoring well. Previous passive sampling devices, the design of which the present study was based on, have been employed in evaluating in situ bacterial activity (primarily contaminant degradation ability) and the collection of colloids; however, the characterization of the collected bacterial fraction has yet to be demonstrated. Concern for the performance of this collection device, particularly with respect to sampling of the biological population, is addressed through laboratory and field experiments. These experiments demonstrated (1) the ability to maintain a dynamic equilibrium with respect to bacterial concentrations within and outside of the dialysis cells; (2) unbiased sampling related to bacterial communities as determined by denaturing gradient gel electrophoresis; (3) uniform collection by dialysis cells throughout the length of the sampler; and (4) acquisition of a representative sample, although a minimum suspension time could not be determined with available data. These results have provided a level of confidence in the ability of the passive sampler to collect ground water samples for the purpose of bacterial characterization.