Dual Radioisotope Labeling to Monitor Virus Transport and Identify
Factors Affecting Viral Inactivation in Contaminated Aquifer Sediments
from Cape Cod, Massachusetts
By David W. Metge, Theresa Navigato, Jon E. Larson, Joseph N. Ryan, and Ronald
W. Harvey
ABSTRACT
The in-situ mobility of bacteriophage PRD-1, whose DNA was
labeled with 32P
nucleotides and protein coat was labeled with 35S methionine, was tested using
small-scale (1-4 meter) injection and recovery experiments. The isotope-labeled
virus and a conservative (bromide) tracer were injected into shallow (uncontaminated)
and deep (treated-sewage-contaminated) sandy aquifer sediments within an unconfined
glacial outwash aquifer on Cape Cod, Mass. This contaminated aquifer has sharp
pH and chemical gradients and sediment heterogeneities, which influence the
transport properties of microorganisms (0.05-5.0 micrometers [µm]).
In the presence of treated-sewage contaminants and the common household surfactant
SDBS (sodium dodecyl benzene sulfonate), concentration histories of dual-labeled
phage exhibited much different transport behavior than was observed in an
earlier field experiment using a different surfactant. Peak breakthroughs
of infective virus were 1 to 2 orders of magnitude greater than the earlier
experiment. Also, there was little or no breakthrough of radiolabel in the
absence of infective virus. This was in direct contrast to results from the
earlier experiment where greater than 98% of the observed breakthrough was
as noninfective virus. It is hypothesized that virus infectivity may be due
to virus-sediment binding interactions.
Although virus transport properties differ somewhat from those observed for
groundwater microbial populations, dual-isotope-labeled infective virus were
detected several meters downgradient. The high degree of infective virus transport
in the presence of environmentally relevant concentrations of SDBS suggests
that this surfactant may help protect against virus inactivation and promote
subsurface transport by reducing virus binding to sediment surfaces. Presence
of surfactants appears to have implications in the degree of risk associated
with viral pathogen transport and in the setback distances for public water
supply wells close to sources of sewage contamination.
