Time scales for pollution assessment - Bewerkingsoverzicht

Bex op 29 nov 2007 om 13:05

2007-11-29T13:05:25Z

Bex: /* Terminology */

2007-11-26T14:43:08Z

‎Terminology

Harveytw: /* Continuously stirred tank reactor (CSTR) method */

2007-11-26T14:36:15Z

‎Continuously stirred tank reactor (CSTR) method

Harveytw: /* Tidal prism method */

2007-11-26T14:35:47Z

‎Tidal prism method

Bex op 26 nov 2007 om 14:29

2007-11-26T14:29:36Z

Bex: /* Continuously stirred tank reactor (CSTR) method */

2007-11-26T12:39:51Z

‎Continuously stirred tank reactor (CSTR) method

Bex: /* Terminology */

2007-11-26T12:39:01Z

‎Terminology

Bex op 26 nov 2007 om 12:25

2007-11-26T12:25:51Z

Bex op 26 nov 2007 om 11:56

2007-11-26T11:56:17Z

Bex op 26 nov 2007 om 11:53

2007-11-26T11:53:53Z

@@ Regel 13: / Regel 13: @@
 Many retention time scales can be found in the literature, often with distinct definitions for the same concept (see for instance Oliveira and Baptista, (1997) <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>, Shen and Haas, (2004) <ref name="Shen">Shen J. and Haas L. (2004). Calculating age and residence time in the tidal York River using three-dimensional model experiments, ''Estuarine, Coastal and Shelf Science'', '''61''' 449-461.</ref> for more details). Here, three fundamentally different concepts are presented, following the classification presented in Monsen et al. (2002) <ref name="Monsen">Monsen N.E., Cloern J.E. and Lucas L.V (2002). A comment on the use of flushing time, residence time, and age as transport time scales. ''Limnology and Oceanography'', '''47'''(5) 1545-1553.</ref> : [[Flushing Time|flushing time]], [[residence time]] and age.
-Flushing time is the "time to replace the freshwater volume of the estuary by the total freshwater input flux (river, discharges, rainfall, etc.)" (Officer and Kester, 1991) or, in a more general way, "the ratio of the mass of a scalar in a reservoir to the rate of renewal of the scalar".<ref name="Geyer">Geyer W.R., Morris J.T., Pahl F.G. and Jay D.A. (2000). '' Interaction between physical processes and ecosystem structure. A comparative approach''. 177-206pp, In EStuarine Science: a synthetic approach to research and practice, Hobbie J.E. (ed.), Island Press.</ref> this transport time scale is a whole-system indicator of the renewal capacity, but does not allow for the distinction between several forcing mechanisms (e.g., the influence of tidal motion to flush out the system) or the spatial and time variability of the renewal capacity.
+Flushing time is the "time to replace the freshwater volume of the estuary by the total freshwater input flux (river, discharges, rainfall, etc.)" <ref name="Officer">Officer C.B. and D.R. Kester (1991). On estimating the non-advective tidal exchanges and advective gravitational circulation exchanges in an Estuary, ''Estuarine, Coastal and Shelf Science'', '''32''' 99-103.</ref> or, in a more general way, "the ratio of the mass of a scalar in a reservoir to the rate of renewal of the scalar".<ref name="Geyer">Geyer W.R., Morris J.T., Pahl F.G. and Jay D.A. (2000). '' Interaction between physical processes and ecosystem structure. A comparative approach''. 177-206pp, In EStuarine Science: a synthetic approach to research and practice, Hobbie J.E. (ed.), Island Press.</ref> this transport time scale is a whole-system indicator of the renewal capacity, but does not allow for the distinction between several forcing mechanisms (e.g., the influence of tidal motion to flush out the system) or the spatial and time variability of the renewal capacity.
-Residence time is the "time it takes for any waterparcel of the sample to leave the lagoon through its outlet to the sea". <ref name="Dronkers">Dronkers J. and Zimmerman J.T.F. (1982). Some principles of mixing in tidal lagoons. Oceanologica Acta. ''Proceedings of the International Symposium on Coastal Lagoons'', p. 107-117.</ref> It can be used to analyse the spatial variation of flushing properties and the variation of renewal for different environmental conditions (effect of tidal amplitude and phase, relative importance of different forcings – waves, currents, etc.). These detailed properties makes [[residence time|residence times]] very useful for comparative analyses of the effects of several engineering interventions (dredging, hard-struture building), and also to characterize changes in the system’s contaminant inputs (changes in the nature, location and frequency of the sources of contaminants). The specific way to define "the time to leave the system" can also lead to different concepts of residence times which can be very important for water quality analyses. If [[residence time|residence times]] are defined as the "time for a water parcel to leave the system once" (once-through residence times, Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), the concept is very useful to characterize the flushing of [[pollutant|pollutants]] that are significantly altered once outside the system (for instance due to strong variations in salinity and/or temperature). An opposite definition is "the time for a water parcel to leave the system without returning at a later tide" (denoted re-entrant [[residence time|residence times]] in Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), which is useful for the analysis of the retention of conservative tracers in a system. Finally, residence times can also be defined as the "time spent in the domain of interest" (denoted as exposure time in Deleersnjider and Delhez, 2005). This definition is particularly important in coastal [[pollution]] since it quantifies the time of exposure of a system to a specific contaminant.
+Residence time is the "time it takes for any waterparcel of the sample to leave the lagoon through its outlet to the sea". <ref name="Dronkers">Dronkers J. and Zimmerman J.T.F. (1982). Some principles of mixing in tidal lagoons. Oceanologica Acta. ''Proceedings of the International Symposium on Coastal Lagoons'', p. 107-117.</ref> It can be used to analyse the spatial variation of flushing properties and the variation of renewal for different environmental conditions (effect of tidal amplitude and phase, relative importance of different forcings – waves, currents, etc.). These detailed properties makes [[residence time|residence times]] very useful for comparative analyses of the effects of several engineering interventions (dredging, hard-struture building), and also to characterize changes in the system’s contaminant inputs (changes in the nature, location and frequency of the sources of contaminants). The specific way to define "the time to leave the system" can also lead to different concepts of residence times which can be very important for water quality analyses. If [[residence time|residence times]] are defined as the "time for a water parcel to leave the system once" (once-through residence times, Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), the concept is very useful to characterize the flushing of [[pollutant|pollutants]] that are significantly altered once outside the system (for instance due to strong variations in salinity and/or temperature). An opposite definition is "the time for a water parcel to leave the system without returning at a later tide" (denoted re-entrant [[residence time|residence times]] in Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), which is useful for the analysis of the retention of conservative tracers in a system. Finally, residence times can also be defined as the "time spent in the domain of interest" (denoted as exposure time in <ref name="Deleersnijder">Deleersnijder E., J.-M. Campin and E.J.M. Delhez (2001). The concept of age in marine modelling: I. Theory and preliminary model results, ''Journal of Marine Systems'', '''28''' 229-267.</ref>). This definition is particularly important in coastal [[pollution]] since it quantifies the time of exposure of a system to a specific contaminant.
-Using a reservoir concept, the age of a contaminant can be referred to as "the time elapsed since it entered the system". <ref name="Bolin">Bolin B. and Rodhe A. (1973). ''A note on the concepts of age distribution and transit time in natural reservoirs''. Tellus, 2558-62.</ref> Zimmerman (1976) <ref name="Zimmerman">Zimmerman J.T.F. (1976). Mixing and flushing of tidal embayments in the westren Dutch Wadden Sea. Part I: Distribution of salinity and calculation of mixing time scales. ''Netherlands Journal of Sea Research'', '''10'''(2) 149-191.</ref> proposed a definition that explicitly accounts for the spatial variability of this time scale: “age of a water parcel is the time elapsed since the particle departed the region where its age is zero”. A general theory for age, based on tracer concentrations, can be found in Deleersnijder et al. (2001). Age is the complement of [[residence time|residence times]] and can be used to understand the pathways of contaminants and organisms within the system, in particular in the influence of external sources/sinks of contaminants to coastal systems.
+Using a reservoir concept, the age of a contaminant can be referred to as "the time elapsed since it entered the system". <ref name="Bolin">Bolin B. and Rodhe A. (1973). ''A note on the concepts of age distribution and transit time in natural reservoirs''. Tellus, 2558-62.</ref> Zimmerman (1976) <ref name="Zimmerman">Zimmerman J.T.F. (1976). Mixing and flushing of tidal embayments in the westren Dutch Wadden Sea. Part I: Distribution of salinity and calculation of mixing time scales. ''Netherlands Journal of Sea Research'', '''10'''(2) 149-191.</ref> proposed a definition that explicitly accounts for the spatial variability of this time scale: “age of a water parcel is the time elapsed since the particle departed the region where its age is zero”. A general theory for age, based on tracer concentrations, can be found in Deleersnijder et al. (2001 <ref name="Deleersnijder">Deleersnijder E., J.-M. Campin and E.J.M. Delhez (2001). The concept of age in marine modelling: I. Theory and preliminary model results, ''Journal of Marine Systems'', '''28''' 229-267.</ref>). Age is the complement of [[residence time|residence times]] and can be used to understand the pathways of contaminants and organisms within the system, in particular in the influence of external sources/sinks of contaminants to coastal systems.
 ==Methodologies and tools==

@@ Regel 13: / Regel 13: @@
 Many retention time scales can be found in the literature, often with distinct definitions for the same concept (see for instance Oliveira and Baptista, (1997) <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>, Shen and Haas, (2004) <ref name="Shen">Shen J. and Haas L. (2004). Calculating age and residence time in the tidal York River using three-dimensional model experiments, ''Estuarine, Coastal and Shelf Science'', '''61''' 449-461.</ref> for more details). Here, three fundamentally different concepts are presented, following the classification presented in Monsen et al. (2002) <ref name="Monsen">Monsen N.E., Cloern J.E. and Lucas L.V (2002). A comment on the use of flushing time, residence time, and age as transport time scales. ''Limnology and Oceanography'', '''47'''(5) 1545-1553.</ref> : [[Flushing Time|flushing time]], [[residence time]] and age.
-Flushing time is the "time to replace the freshwater volume of the estuary by the total freshwater input flux (river, discharges, rainfall, etc.)" (Officer and Kester, 1991) or, in a more general way, "the ratio of the mass of a scalar in a reservoir to the rate of renewal of the scalar".<ref name="Geyer">Geyer W.R., Morris J.T., Pahl F.G. and Jay D.A. (2000). '' Interaction between physical processes and ecosystem structure. A comparative approach''. 177-206pp, In EStuarine Science: a synthetic approach to research and practice, Hobbie J.E. (ed.), Island Press.</ref> his transport time scale is a whole-system indicator of the renewal capacity, but does not allow for the distinction between several forcing mechanisms (e.g., the influence of tidal motion to flush out the system) or the spatial and time variability of the renewal capacity.
+Flushing time is the "time to replace the freshwater volume of the estuary by the total freshwater input flux (river, discharges, rainfall, etc.)" (Officer and Kester, 1991) or, in a more general way, "the ratio of the mass of a scalar in a reservoir to the rate of renewal of the scalar".<ref name="Geyer">Geyer W.R., Morris J.T., Pahl F.G. and Jay D.A. (2000). '' Interaction between physical processes and ecosystem structure. A comparative approach''. 177-206pp, In EStuarine Science: a synthetic approach to research and practice, Hobbie J.E. (ed.), Island Press.</ref> this transport time scale is a whole-system indicator of the renewal capacity, but does not allow for the distinction between several forcing mechanisms (e.g., the influence of tidal motion to flush out the system) or the spatial and time variability of the renewal capacity.
 Residence time is the "time it takes for any waterparcel of the sample to leave the lagoon through its outlet to the sea". <ref name="Dronkers">Dronkers J. and Zimmerman J.T.F. (1982). Some principles of mixing in tidal lagoons. Oceanologica Acta. ''Proceedings of the International Symposium on Coastal Lagoons'', p. 107-117.</ref> It can be used to analyse the spatial variation of flushing properties and the variation of renewal for different environmental conditions (effect of tidal amplitude and phase, relative importance of different forcings – waves, currents, etc.). These detailed properties makes [[residence time|residence times]] very useful for comparative analyses of the effects of several engineering interventions (dredging, hard-struture building), and also to characterize changes in the system’s contaminant inputs (changes in the nature, location and frequency of the sources of contaminants). The specific way to define "the time to leave the system" can also lead to different concepts of residence times which can be very important for water quality analyses. If [[residence time|residence times]] are defined as the "time for a water parcel to leave the system once" (once-through residence times, Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), the concept is very useful to characterize the flushing of [[pollutant|pollutants]] that are significantly altered once outside the system (for instance due to strong variations in salinity and/or temperature). An opposite definition is "the time for a water parcel to leave the system without returning at a later tide" (denoted re-entrant [[residence time|residence times]] in Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), which is useful for the analysis of the retention of conservative tracers in a system. Finally, residence times can also be defined as the "time spent in the domain of interest" (denoted as exposure time in Deleersnjider and Delhez, 2005). This definition is particularly important in coastal [[pollution]] since it quantifies the time of exposure of a system to a specific contaminant.

@@ Regel 44: / Regel 44: @@
 <math>C(t) = C_0*e^{-\frac{t}{FT}}</math>
-where ''C'' is the concentration of a [[pollutant]] at time ''t'', due to an instantaneous load at time ''t<sub>0</sub>'' that leads to the initial concentration ''C<sub>0</sub>''. This method assumes that
+where ''C'' is the concentration of a [[pollutant]] at time ''t'', due to an instantaneous load at time ''t<sub>0</sub>'' that leads to the initial concentration ''C<sub>0</sub>''. This method assumes that:
-# no further mass is introduced in the system,
+# no further mass is introduced in the system;
-# flow and volume in the CSTR are constant in time and
+# flow and volume in the CSTR are constant in time, and
 # instantaneous and complete mixing of the [[pollutant]] in the system.

@@ Regel 34: / Regel 34: @@
 <math>FT = V*\frac{T}{P}</math>
-where ''V'' - water volume at high tide, ''T'' - tidal period, ''P'' - tidal prism of a representative flood tide. This method only requires basin geometry and tidal range information. It assumes that
+where ''V'' - water volume at high tide, ''T'' - tidal period, ''P'' - tidal prism of a representative flood tide. This method only requires basin geometry and tidal range information. It assumes that:
-# the system is well mixed,
+# the system is well mixed;
-# tidal flow is the dominant flushing mechanism,
+# tidal flow is the dominant flushing mechanism;
 # the system is at steady-state with a sinusoidal tidal signal, and
 # the system is fully flushed in a single tidal cycle.

← Oudere versie		Versie van 26 nov 2007 om 14:29
Regel 1:		Regel 1:
−	{{~~Revision~~}}	+	{{Featured}}

	'''Time scales for pollution assessment''' can be considered using three commonly used methods: [[Flushing Time\|flushing time]], [[residence time]] and age. In this article the methodologies and tools to quantify each of these methods is explained as well as the applicability of each method.		'''Time scales for pollution assessment''' can be considered using three commonly used methods: [[Flushing Time\|flushing time]], [[residence time]] and age. In this article the methodologies and tools to quantify each of these methods is explained as well as the applicability of each method.

← Oudere versie		Versie van 26 nov 2007 om 12:39
Regel 58:		Regel 58:


−	The methodologies to compute age are the same as those used for [[residence time]]. The readers are referred to Shen and Haas, (2004)<ref name="Shen">Shen J. and Haas L. (2004). Calculating age and residence time in the tidal York River using three-dimensional model experiments, ''Estuarine, Coastal and Shelf Science'', '''61''' 449-461.</ref> and Kennedy et al. (2006)<ref name="Kennedy">Kennedy M.G., Ahlfeld D.P., Schmidt D.P. and Tobiason J.E. (2006). Three-dimensional modeling for estimation of hydraulic retention time in a reservoir, ''Journal of Environmental Engineering'', '''132'''(9) 976-984.</ref> for details on the application of concentration and particle models for the calculation of age.	+	The methodologies to compute age are the same as those used for [[residence time]]. The readers are referred to Shen and Haas, (2004) <ref name="Shen">Shen J. and Haas L. (2004). Calculating age and residence time in the tidal York River using three-dimensional model experiments, ''Estuarine, Coastal and Shelf Science'', '''61''' 449-461.</ref> and Kennedy et al. (2006) <ref name="Kennedy">Kennedy M.G., Ahlfeld D.P., Schmidt D.P. and Tobiason J.E. (2006). Three-dimensional modeling for estimation of hydraulic retention time in a reservoir, ''Journal of Environmental Engineering'', '''132'''(9) 976-984.</ref> for details on the application of concentration and particle models for the calculation of age.

	==References==		==References==

@@ Regel 11: / Regel 11: @@
 ==Terminology==
-Many retention time scales can be found in the literature, often with distinct definitions for the same concept (see for instance Oliveira and Baptista, (1997) <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>, Shen and Haas, (2004) <ref name="Shen">Shen J. and Haas L. (2004). Calculating age and residence time in the tidal York River using three-dimensional model experiments, ''Estuarine, Coastal and Shelf Science'', '''61''' 449-461.</ref> for more details). Here, three fundamentally different concepts are presented, following the classification presented in Monsen et al. (2002) <ref name="Monsen">Monsen N.E., Cloern J.E. and Lucas L.V (2002). A comment on the use of flushing time, residence time, and age as transport time scales. ''Limnology and Oceanography'', '''47'''(5) 1545-1553.</ref> :flushing time, residence time and age.
+Many retention time scales can be found in the literature, often with distinct definitions for the same concept (see for instance Oliveira and Baptista, (1997) <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>, Shen and Haas, (2004) <ref name="Shen">Shen J. and Haas L. (2004). Calculating age and residence time in the tidal York River using three-dimensional model experiments, ''Estuarine, Coastal and Shelf Science'', '''61''' 449-461.</ref> for more details). Here, three fundamentally different concepts are presented, following the classification presented in Monsen et al. (2002) <ref name="Monsen">Monsen N.E., Cloern J.E. and Lucas L.V (2002). A comment on the use of flushing time, residence time, and age as transport time scales. ''Limnology and Oceanography'', '''47'''(5) 1545-1553.</ref> : [[Flushing Time|flushing time]], [[residence time]] and age.
-Flushing time has been defined as the "time to replace the freshwater volume of the estuary by the total freshwater input flux (river, discharges, rainfall,...)" (Officer and Kester, 1991) or, in a more general way, as "the ratio of the mass of a scalar in a reservoir to the rate of renewal of the scalar".<ref name="Geyer">Geyer W.R., Morris J.T., Pahl F.G. and Jay D.A. (2000). '' Interaction between physical processes and ecosystem structure. A comparative approach''. 177-206pp, In EStuarine Science: a synthetic approach to research and practice, Hobbie J.E. (ed.), Island Press.</ref> his transport time scale is a whole-system indicator of the renewal capacity, but does not allow for the distinction between several forcing mechanisms (e.g., the influence of tidal motion to flush out the system) or the spatial and time variability of the renewal capacity.
+Flushing time is the "time to replace the freshwater volume of the estuary by the total freshwater input flux (river, discharges, rainfall, etc.)" (Officer and Kester, 1991) or, in a more general way, "the ratio of the mass of a scalar in a reservoir to the rate of renewal of the scalar".<ref name="Geyer">Geyer W.R., Morris J.T., Pahl F.G. and Jay D.A. (2000). '' Interaction between physical processes and ecosystem structure. A comparative approach''. 177-206pp, In EStuarine Science: a synthetic approach to research and practice, Hobbie J.E. (ed.), Island Press.</ref> his transport time scale is a whole-system indicator of the renewal capacity, but does not allow for the distinction between several forcing mechanisms (e.g., the influence of tidal motion to flush out the system) or the spatial and time variability of the renewal capacity.
-Residence time has been defined as "the time it takes for any waterparcel of the sample to leave the lagoon through its outlet to the sea". <ref name="Dronkers">Dronkers J. and Zimmerman J.T.F. (1982). Some principles of mixing in tidal lagoons. Oceanologica Acta. ''Proceedings of the International Symposium on Coastal Lagoons'', p. 107-117.</ref> They can be used to analyse the spatial variation of flushing properties and the variation of renewal for different environmental conditions (effect of tidal amplitude and phase, relative importance of different forcings – waves, currents, …). These detailed properties makes residence times very useful for comparative analyses of the effects of several engineering interventions (dredging, hard-struture building), and also to characterize changes in the system’s contaminant inputs (changes in the nature, location and frequency of the sources of contaminants). The specific way to define "the time to leave the system" can also lead to different concepts of residence times which can be very important for water quality analyses. If residence times are defined as the "time for a water parcel to leave the system once" (once-through residence times, Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), the concept is very useful to characterize the flushing of pollutants that are significantly altered once outside the system (for instance due to strong variations in salinity and/or temperature). An opposite definition is "the time for a water parcel to leave the system without returning at a later tide" (denoted re-entrant residence times in Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), which is useful for the analysis of the retention of conservative tracers in a system. Finally, residence times can also be defined as the "time spent in the domain of interest" (denoted as exposure time in Deleersnjider and Delhez, 2005). This definition is particularly important in coastal pollution since it quantifies the time of exposure of a system to a specific contaminant.
+Residence time is the "time it takes for any waterparcel of the sample to leave the lagoon through its outlet to the sea". <ref name="Dronkers">Dronkers J. and Zimmerman J.T.F. (1982). Some principles of mixing in tidal lagoons. Oceanologica Acta. ''Proceedings of the International Symposium on Coastal Lagoons'', p. 107-117.</ref> It can be used to analyse the spatial variation of flushing properties and the variation of renewal for different environmental conditions (effect of tidal amplitude and phase, relative importance of different forcings – waves, currents, etc.). These detailed properties makes [[residence time|residence times]] very useful for comparative analyses of the effects of several engineering interventions (dredging, hard-struture building), and also to characterize changes in the system’s contaminant inputs (changes in the nature, location and frequency of the sources of contaminants). The specific way to define "the time to leave the system" can also lead to different concepts of residence times which can be very important for water quality analyses. If [[residence time|residence times]] are defined as the "time for a water parcel to leave the system once" (once-through residence times, Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), the concept is very useful to characterize the flushing of [[pollutant|pollutants]] that are significantly altered once outside the system (for instance due to strong variations in salinity and/or temperature). An opposite definition is "the time for a water parcel to leave the system without returning at a later tide" (denoted re-entrant [[residence time|residence times]] in Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), which is useful for the analysis of the retention of conservative tracers in a system. Finally, residence times can also be defined as the "time spent in the domain of interest" (denoted as exposure time in Deleersnjider and Delhez, 2005). This definition is particularly important in coastal [[pollution]] since it quantifies the time of exposure of a system to a specific contaminant.
-Using a reservoir concept, the age of a contaminant can be defined as "the time elapsed since it entered the system". <ref name="Bolin">Bolin B. and Rodhe A. (1973). ''A note on the concepts of age distribution and transit time in natural reservoirs''. Tellus, 2558-62.</ref> Zimmerman (1976) <ref name="Zimmerman">Zimmerman J.T.F. (1976). Mixing and flushing of tidal embayments in the westren Dutch Wadden Sea. Part I: Distribution of salinity and calculation of mixing time scales. ''Netherlands Journal of Sea Research'', '''10'''(2) 149-191.</ref> proposed a definition that explicitly accounts for the spatial variability of this time scale: “age of a water parcel is the time elapsed since the particle departed the region where its age is zero”. A general theory for age, based on tracer concentrations, can be found in Deleersnijder et al. (2001). Age is the complement of residence time and can be used to understand the pathways of contaminants and organisms within the system, in particular in the influence of external sources/sinks of contaminants to coastal systems.
+Using a reservoir concept, the age of a contaminant can be referred to as "the time elapsed since it entered the system". <ref name="Bolin">Bolin B. and Rodhe A. (1973). ''A note on the concepts of age distribution and transit time in natural reservoirs''. Tellus, 2558-62.</ref> Zimmerman (1976) <ref name="Zimmerman">Zimmerman J.T.F. (1976). Mixing and flushing of tidal embayments in the westren Dutch Wadden Sea. Part I: Distribution of salinity and calculation of mixing time scales. ''Netherlands Journal of Sea Research'', '''10'''(2) 149-191.</ref> proposed a definition that explicitly accounts for the spatial variability of this time scale: “age of a water parcel is the time elapsed since the particle departed the region where its age is zero”. A general theory for age, based on tracer concentrations, can be found in Deleersnijder et al. (2001). Age is the complement of [[residence time|residence times]] and can be used to understand the pathways of contaminants and organisms within the system, in particular in the influence of external sources/sinks of contaminants to coastal systems.
 ==Methodologies and tools==

@@ Regel 17: / Regel 17: @@
 Residence time has been defined as "the time it takes for any waterparcel of the sample to leave the lagoon through its outlet to the sea". <ref name="Dronkers">Dronkers J. and Zimmerman J.T.F. (1982). Some principles of mixing in tidal lagoons. Oceanologica Acta. ''Proceedings of the International Symposium on Coastal Lagoons'', p. 107-117.</ref> They can be used to analyse the spatial variation of flushing properties and the variation of renewal for different environmental conditions (effect of tidal amplitude and phase, relative importance of different forcings – waves, currents, …). These detailed properties makes residence times very useful for comparative analyses of the effects of several engineering interventions (dredging, hard-struture building), and also to characterize changes in the system’s contaminant inputs (changes in the nature, location and frequency of the sources of contaminants). The specific way to define "the time to leave the system" can also lead to different concepts of residence times which can be very important for water quality analyses. If residence times are defined as the "time for a water parcel to leave the system once" (once-through residence times, Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), the concept is very useful to characterize the flushing of pollutants that are significantly altered once outside the system (for instance due to strong variations in salinity and/or temperature). An opposite definition is "the time for a water parcel to leave the system without returning at a later tide" (denoted re-entrant residence times in Oliveira and Baptista, 1997 <ref name="Oliveira">Oliveira A. and Baptista A.M. (1997). Diagnostic modeling of residence times in estuaries. ''Water Resources Research'', '''33'''(8) 1935-1946.</ref>), which is useful for the analysis of the retention of conservative tracers in a system. Finally, residence times can also be defined as the "time spent in the domain of interest" (denoted as exposure time in Deleersnjider and Delhez, 2005). This definition is particularly important in coastal pollution since it quantifies the time of exposure of a system to a specific contaminant.
-Using a reservoir concept, the age of a contaminant can be defined as "the time elapsed since it entered the system" (Bolin and Rodhe, 1973). Zimmerman (1976) <ref name="Zimmerman">Zimmerman J.T.F. (1976). Mixing and flushing of tidal embayments in the westren Dutch Wadden Sea. Part I: Distribution of salinity and calculation of mixing time scales. ''Netherlands Journal of Sea Research'', '''10'''(2) 149-191.</ref> proposed a definition that explicitly accounts for the spatial variability of this time scale: “age of a water parcel is the time elapsed since the particle departed the region where its age is zero”. A general theory for age, based on tracer concentrations, can be found in Deleersnijder et al. (2001). Age is the complement of residence time and can be used to understand the pathways of contaminants and organisms within the system, in particular in the influence of external sources/sinks of contaminants to coastal systems.
+Using a reservoir concept, the age of a contaminant can be defined as "the time elapsed since it entered the system". <ref name="Bolin">Bolin B. and Rodhe A. (1973). ''A note on the concepts of age distribution and transit time in natural reservoirs''. Tellus, 2558-62.</ref> Zimmerman (1976) <ref name="Zimmerman">Zimmerman J.T.F. (1976). Mixing and flushing of tidal embayments in the westren Dutch Wadden Sea. Part I: Distribution of salinity and calculation of mixing time scales. ''Netherlands Journal of Sea Research'', '''10'''(2) 149-191.</ref> proposed a definition that explicitly accounts for the spatial variability of this time scale: “age of a water parcel is the time elapsed since the particle departed the region where its age is zero”. A general theory for age, based on tracer concentrations, can be found in Deleersnijder et al. (2001). Age is the complement of residence time and can be used to understand the pathways of contaminants and organisms within the system, in particular in the influence of external sources/sinks of contaminants to coastal systems.
 ==Methodologies and tools==
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