Hansen, J. L. S., Timm, U., and Kiørboe, T., 1995. Adaptive
significance of phytoplankton stickiness with emphasis on the
diatom Skeletonema costatum. Marine Biology, 123(4),
667–676.
IUPAC, 1997. Compendium of Chemical Terminology, 2nd edn.
(the “Gold Book”). Compiled by McNaught, A. D., and
Wilkinson, A. Oxford: Blackwell Scientific Publications.
XML on-line corrected version: http://goldbook.iupac.
org (2006) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/
goldbook.
McCave, I. N., 1984. Size spectra and aggregation of suspended
particles in the deep ocean. Deep-Sea Research Part
a-Oceanographic Research Papers, 31(4), 329–352.
Passow, U., 2002. Transparent exopolymer particles (TEP) in
aquatic environments. Progress in Oceanography, 55(3–4),
287–333.
Simon, M., Grossart, H. P., Schweitzer, B., and Ploug, H., 2002.
Microbial ecology of organic aggregates in aquatic ecosystems.
Aquatic Microbial Ecology, 28(2), 175–211.
Vandamme, D., Foubert, I., and Muylaert, K., 2013. Flocculation as
a low-cost method for harvesting microalgae for bulk biomass
production. Trends in Biotechnology, 31(4), 233–239.
Verney, R., Lafite, R., and Brun-Cottan, J. C., 2009. Flocculation
potential of estuarine particles: the importance of environmental factors and of the spatial and seasonal variability of
suspended particulate matter. Estuaries and Coasts, 32(4),
678–693.
Wilén, B.-M., Lund Nielsen, J., Keiding, K., and Nielsen, P. H.,
2000. Influence of microbial activity on the stability of activated
sludge flocs. Colloids and Surfaces B: Biointerfaces, 18(2),
145–156.
Cross-references
pH
Sediment Transport
Tides
FLUSHING TIME
Edward H. Dettmann
U.S. Environmental Protection Agency, Office
of Research and Development/NHEERL Atlantic
Ecology Division, Narragansett, RI, USA
Synonyms
e-Folding time; Freshwater replacement time; Freshwater
residence time, Freshwater transit time; Freshwater turnover time
Definition
The flushing time of an estuary is generally defined as the
turnover time of freshwater in the estuary (t fw ), that is,
the time required to replace the freshwater contained in
the estuary with freshwater inflow. The flushing time of
an estuary is calculated as the ratio of the volume
of freshwater in the estuary (V fw ) to the total rate of freshwater input (Q fw ):
t fw ¼
V fw
Q fw
While V fw increases as Q fw does, it does so more slowly,
so that flushing time decreases as freshwater flow
increases (Pilson, 1985).
Measurement
The freshwater content (V fw ), and therefore t fw , may be
determined by mass balance calculations from the estuary volume, the volume-weighted average salinity in
the estuary, and the salinity outside the seaward boundary
(Pilson, 1985). This is termed the freshwater replacement
method.
Flushing time may also be estimated by introducing
a conservative tracer, such as dye, at a constant concentration into the freshwater inflow until the mass or average
concentration of tracer in the estuary at a given tide
stage attains equilibrium. After termination of tracer input,
the spatially averaged concentrations will decrease
approximately exponentially as tracer is flushed from the
estuary. The time required for the concentration to attain
e
À1 times the initial concentration, often referred to as
the e-folding time, is an estimator of the flushing time.
Applications
Flushing time is a useful indicator of the behavior of
materials introduced into an estuary with freshwater.
For instance, the fraction of nitrogen entering the estuary
from the watershed that flows through the estuary to the
sea, and the fraction lost within the estuary to processes
such as denitrification and permanent burial in sediments, may be estimated using the flushing time
(Dettmann, 2001). The turnover or mean transit time of
conservative materials introduced with freshwater are
equal to the flushing time of freshwater, while those of
nonconservative materials that are consumed by processes in the estuary have shorter turnover times. See
Dettmann (2008) for details in an application to freshwater lakes.
Flushing time, as described above, applies to an estuary
as a whole. The concept of a flushing time may also be
applied to a portion of an estuary, e.g., in a box model
(Hagy et al., 2000).
Other concepts related to flushing time are sometimes
used in describing material movement through an
estuary. Examples are estuarine residence time, that is,
the residence time in the estuary of a conservative
substance introduced uniformly in concentration throughout the estuary, and pulse residence time (the residence
time of a conservative substance introduced as an
FLUSHING TIME
329
significance of phytoplankton stickiness with emphasis on the
diatom Skeletonema costatum. Marine Biology, 123(4),
667–676.
IUPAC, 1997. Compendium of Chemical Terminology, 2nd edn.
(the “Gold Book”). Compiled by McNaught, A. D., and
Wilkinson, A. Oxford: Blackwell Scientific Publications.
XML on-line corrected version: http://goldbook.iupac.
org (2006) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/
goldbook.
McCave, I. N., 1984. Size spectra and aggregation of suspended
particles in the deep ocean. Deep-Sea Research Part
a-Oceanographic Research Papers, 31(4), 329–352.
Passow, U., 2002. Transparent exopolymer particles (TEP) in
aquatic environments. Progress in Oceanography, 55(3–4),
287–333.
Simon, M., Grossart, H. P., Schweitzer, B., and Ploug, H., 2002.
Microbial ecology of organic aggregates in aquatic ecosystems.
Aquatic Microbial Ecology, 28(2), 175–211.
Vandamme, D., Foubert, I., and Muylaert, K., 2013. Flocculation as
a low-cost method for harvesting microalgae for bulk biomass
production. Trends in Biotechnology, 31(4), 233–239.
Verney, R., Lafite, R., and Brun-Cottan, J. C., 2009. Flocculation
potential of estuarine particles: the importance of environmental factors and of the spatial and seasonal variability of
suspended particulate matter. Estuaries and Coasts, 32(4),
678–693.
Wilén, B.-M., Lund Nielsen, J., Keiding, K., and Nielsen, P. H.,
2000. Influence of microbial activity on the stability of activated
sludge flocs. Colloids and Surfaces B: Biointerfaces, 18(2),
145–156.
Cross-references
pH
Sediment Transport
Tides
FLUSHING TIME
Edward H. Dettmann
U.S. Environmental Protection Agency, Office
of Research and Development/NHEERL Atlantic
Ecology Division, Narragansett, RI, USA
Synonyms
e-Folding time; Freshwater replacement time; Freshwater
residence time, Freshwater transit time; Freshwater turnover time
Definition
The flushing time of an estuary is generally defined as the
turnover time of freshwater in the estuary (t fw ), that is,
the time required to replace the freshwater contained in
the estuary with freshwater inflow. The flushing time of
an estuary is calculated as the ratio of the volume
of freshwater in the estuary (V fw ) to the total rate of freshwater input (Q fw ):
t fw ¼
V fw
Q fw
While V fw increases as Q fw does, it does so more slowly,
so that flushing time decreases as freshwater flow
increases (Pilson, 1985).
Measurement
The freshwater content (V fw ), and therefore t fw , may be
determined by mass balance calculations from the estuary volume, the volume-weighted average salinity in
the estuary, and the salinity outside the seaward boundary
(Pilson, 1985). This is termed the freshwater replacement
method.
Flushing time may also be estimated by introducing
a conservative tracer, such as dye, at a constant concentration into the freshwater inflow until the mass or average
concentration of tracer in the estuary at a given tide
stage attains equilibrium. After termination of tracer input,
the spatially averaged concentrations will decrease
approximately exponentially as tracer is flushed from the
estuary. The time required for the concentration to attain
e
À1 times the initial concentration, often referred to as
the e-folding time, is an estimator of the flushing time.
Applications
Flushing time is a useful indicator of the behavior of
materials introduced into an estuary with freshwater.
For instance, the fraction of nitrogen entering the estuary
from the watershed that flows through the estuary to the
sea, and the fraction lost within the estuary to processes
such as denitrification and permanent burial in sediments, may be estimated using the flushing time
(Dettmann, 2001). The turnover or mean transit time of
conservative materials introduced with freshwater are
equal to the flushing time of freshwater, while those of
nonconservative materials that are consumed by processes in the estuary have shorter turnover times. See
Dettmann (2008) for details in an application to freshwater lakes.
Flushing time, as described above, applies to an estuary
as a whole. The concept of a flushing time may also be
applied to a portion of an estuary, e.g., in a box model
(Hagy et al., 2000).
Other concepts related to flushing time are sometimes
used in describing material movement through an
estuary. Examples are estuarine residence time, that is,
the residence time in the estuary of a conservative
substance introduced uniformly in concentration throughout the estuary, and pulse residence time (the residence
time of a conservative substance introduced as an
FLUSHING TIME
329