New Zealand Journal of Marine and Freshwater Research abstracts
Transport and attenuation of bacteria and bacteriophages in an alluvial
gravel aquifer
L. W. SINTON1
M. J. NOONAN2
R. K. FINLAY3
L. PANG1
M. E. CLOSE1
1Christchurch Science Centre
Institute of Environmental Science
& Research Ltd
P. O. Box 29 181
Christchurch, New Zealand
email: lester.sinton@esr.cri.nz
2Animal and Food Sciences Division
Lincoln University
P. O. Box 84
Canterbury, New Zealand
3Technical Services, Headquarters
Public Health Laboratory Service
61 Colindale Ave
London NW9 5HT, United Kingdom
Abstract The relative attenuation of rhodamine WT dye, two
strains of
Escherichia coli,
Bacillus subtilis endospores,
and the F-RNA bacteriophage MS2 in an alluvial gravel aquifer was investigated
in two tracing experiments at Burnham, near Christchurch, New Zealand. A
simulated concentration curve was fitted to the observed breakthrough curves
using the contaminant transport model AT123D, by optimising hydraulic
conductivity (K), longitudinal dispersivity ([[alpha]]x), and a removal
constant ([[lambda]]) (which includes die-off and physical removal processes)
with the Parameter Estimation (PEST) optimisation routine. When comparing the
parameters, the hydraulic conductivity was converted to velocity (V). The V
ranking was
E. coli 2690 >
B. subtilis endospores
> rhodamine WT in Experiment 1 and
E. coli J6-2 > phage MS2 >
rhodamine WT in Experiment 2. These rankings are consistent with the concept of
pore size exclusion, whereby larger particles are preferentially transported in
the larger interconnected pores where water velocities are higher. The
longitudinal dispersivity ([[alpha]]x) rankings were consistent with pore size
exclusion in Experiment 1, and broadly consistent in Experiment 2. Of the two
parameters, V is considered to provide the more reliable result, because it is
easier to determine peak position in time than peak height. Little useful
information could be derived from the [[lambda]] values in our study, because
of high levels of uncertainty associated with determining peak heights,
particularly in Experiment 1. Overall, the curve fits were better in Experiment
2, because of a greater number of bores and observations. Although this
complicated between-experiment comparisons, an overall retardation (R) ranking
of rhodamine WT > phage MS2;
B. subtilis endospores >
E.
coli J6-2 >
E. coli 2690 is broadly consistent with pore size
exclusion. Overall, our study showed that the application of the AT123D model
to the observed velocities of the tracer curves demonstrated an effect
consistent with pore size exclusion.
Keywords Bacillus subtilis; Escherichia
coli;
bacteriophage MS2; rhodamine WT; tracers; groundwater; AT123D
model
M98062
Received 2 September 1998; accepted 4 October 1999
PDF file of entire paper: medium quality (939K); (scanned from paper original: notes about this process)
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