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Titel |
E. coli transport to stream water column from bottom sediments to the stream water column in base flow conditions |
VerfasserIn |
Yakov Pachepsky, Daniel Shelton, Matthew Stocker |
Konferenz |
EGU General Assembly 2016
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 18 (2016) |
Datensatznummer |
250123761
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Publikation (Nr.) |
EGU/EGU2016-3066.pdf |
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Zusammenfassung |
E. coli as an indicator bacterium is commonly used to characterize microbiological water
quality, to evaluate surface water sources for microbiological impairment, and to assess
management practices that lead to the decrease of pathogens and indicator influx in surface
water sources for recreation and irrigation. Bottom sediments present a large reservoir of
fecal indicator bacteria that are known to be released to water column during high flow events
caused by rainstorms and snowmelt. The objective of this work was to see if the influx of E.
coli from sediments to water occurs also during base flow periods when groundwater rather
than runoff provides the major water input to the stream. The experiment was carried
out at the first-order creek in Maryland flowing in the riparian zone in base flow
conditions. An inert tracer was released to creek water from the manifold for 5 hours.
Streamflow and concentrations of E. coli and tracer were monitored in water 10 m below
tracer release location, and at the downstream location at 450 m from the release
location. The tracer mass recovered at the downstream location was close to the
released tracer mass. We then could directly compare the total numbers of E. coli
in volumes of water containing tracer at the upstream (release) location and the
downstream location. There was a substantial (3 to 6 times) increase in flow between the
upstream and downstream locations as well as the substantial increase in the E.
coli total numbers in water (14 to 26 times). The average E. coli influx from the
bottom sediment was about 400 cells m-2s-1. Although this value is about 2 to 5
times less than published E. coli release rates during high flow events, it still can
substantially change the microbial water quality assessment without any input from animal
agriculture or manure application. Interesting research objectives include finding
out whether the transport of E. coli from bottom sediment to water column during
the base flow periods is an active or passive transport, and how it is affected by
the E. coli concentrations in sediment, sediment properties, and flow conditions. |
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