Virus and Bacteria Transport in a Sandy Aquifer, Cape Cod, MA

Abstract

Transport of the bacteriophage PRD‐1, bacteria, and latex microspheres was studied in a sandy aquifer under natural‐gradient conditions. The field injection was carried out at the U.S. Geological Survey's Toxic Substances Hydrology research site on Cape Cod. The three colloids and a salt tracer (Br−) moved along the same path. There was significant attenuation of the phage, with PRD‐1 peak concentrations less than 0.001 percent of Br− peaks 6 m from the source; but the low detection limit (one per ml) enabled tracking movement of the PRD‐1 plume for 12 m downgradient over the 25‐day experiment. Attenuation of phage was apparently due to retention on soil particles (adsorption). Attenuation of bacteria and microspheres was less, with peak concentrations 6 m from the source on the order of 10 and 0.4 percent of Br−, respectively. Injection of a high‐pH pulse of water 20 days into the experiment resulted in significant remobilization of retained phage, demonstrating that attached phage remained viable, and that PRD‐1 attachment to and detachment from the sandy soil particles was highly pH dependent. Phage behavior in this experiment, i.e. attenuation at pH 5.7 and rapid resuspension at pH 6–8, was consistent with that observed previously in laboratory column studies. Results illustrate that biocolloids travel in a fairly narrow plume in sandy (relatively homogeneous) media, with virus concentrations dropping below detection limit several meters away from the source; bacteria concentrations above detection limits can persist over longer distances.

Processes in microbial transport in the natural subsurface

“…Harvey and Garabedian [51] applied filtration theory to quantitatively model transport of bacteria in a subsequent naturalgradient experiment at the same site, and estimated a collision efficiency of 5 Â 10 À3 to 1 Â 10 À2 at a travel distance of 6.9 m. Harvey et al [52] demonstrated the importance of physical heterogeneity in controlling field-scale bacterial transport. Observations of micro-sphere, bromide, and bacterial transport 6 m downgradient of the injection point varied significantly in three sampling ports separated by a total vertical distance of 0.7 m. Bales et al [5] observed bacterial breakthrough at a distance of 11 m, but their experiment focused on effects of pH on phage (virus) attenuation and remobilization. Harvey et al [53] studied the transport of groundwater protozoa at the Cape Cod site, and found that the protozoa were attenuated more rapidly than bacteria although the protozoa were of the optimal size for transport based on experiments with microspheres of various diameters.…”

Assessment of Factors Influencing Direct Enumeration of Viruses within Estuarine Sediments

“…It is often more difficult to measure viral and bacterial abundance in porous media such as soils and sediments than in water samples due to the necessity of removing viruses and bacteria from the sediment matrix. Although a priori studies have shown the effects of clay (33,35), pH (3,31), and organic matter (42,56) on viral mobility and transport, none have addressed extractability. Correlation For Chesapeake Bay sediments, correlation analysis showed that the sand and clay composition had the most significant correlations to viral abundances (P Ͻ 0.01), with lesser contributions from porosity and water content (P Ͻ 0.05).…”

Development of a Vital Fluorescent Staining Method for Monitoring Bacterial Transport in Subsurface Environments

“…Labeling cells with fluorescent stains has been employed to examine bacterial attachment to surfaces (13), to count the numbers of total and active cells in a variety of environmental samples (37,39,55), and for in situ injection of groundwater bacteria (1,(16)(17)(18)(19). One of the stains used, 4Ј,6-diamino-2-phenylindole (DAPI), specifically binds to nucleic acids (RNA and DNA), which enables it to universally label cells in an organism-independent manner.…”