Abstract
Gravel aquifers act as important potable water sources in central
western Europe yet they are subject to numerous contamination
pressures. Compositional and textural heterogeneity makes
protection zone delineation around groundwater supplies
in these units challenging; artificial tracer testing aids
characterization. This paper reappraises previous tracer test
results in light of new geological and microbiological data.
Comparative passive gradient testing, using a fluorescent solute
(Uranine), virus (H40/1 bacteriophage), and comparably sized
bacterial tracers Escherichia coli and Pseudomonas putida, was
used to investigate a calcareous gravel aquifer’s ability to remove
microbiological contaminants at a test site near Munich, Germany.
Test results revealed E. coli relative recoveries could exceed those
of H40/1 at monitoring wells 10 m and 20 m from an injection
well by almost four times; P. putida recoveries varied by a factor
of up to three between wells. Application of filtration theory
suggested greater attenuation of H40/1 relative to similarly
charged E. coli occurred due to differences in microorganism size,
while estimated collision efficiencies appeared comparable. By
contrast, more positively charged P. putida experienced greater
attenuation at one monitoring point, while lower attenuation
rates at the second location indicated the influence of
geochemical heterogeneity. Test findings proved consistent with
observations from nearby fresh outcrops that suggested thin
open framework gravel beds dominated mass transport in the
aquifer, while discrete intervals containing stained clasts reflect
localized geochemical heterogeneity. Study results highlight the
utility of reconciling outcrop observations with artificial tracer
test responses, using microbiological tracers with well-defined
properties, to characterize aquifer heterogeneity.
Original language | English |
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Pages (from-to) | 1448-1458 |
Number of pages | 11 |
Journal | Journal of Environmental Quality |
Volume | 44 |
Issue number | 5 |
DOIs | |
Publication status | Published - 16 Sept 2015 |
Keywords
- Bacteria
- Bacteriophage
- Tracers
- Gravel Aquifer
- Heterogeneity