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(→‎Tidal flats from space)
(Time scales for pollution assessment)
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==Tidal flats from space==
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==Time scales for pollution assessment==
  
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[[Image:Tidal_Flats_1.jpg|thumb|right|'''Figure 1'''  
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'''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.
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True color image of Landsat 7 (July 15th 2002 scene size 185 x 185 km) with overlayed false color image of ASTER (April 2nd 2005, scene size 60 x 60 km).]]
 
  
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The objective of our research was to classify the different surface types of the tidal flat areas with satellite data in combination with ground truth measurements. Remote sensing has many advantages such as large coverage and the recording of multi-temporal data. Both are useful for monitoring conditions in near real time as well as detecting changes of the environment when analysing historical data. Tidal flats are unique ecosystems because of the water cover, which changes permanently with the tidal phase. They play an important role as a cleansing site for North Sea water, as a nursery for young fish and as a feeding ground for many bird species. They form a transitional zone between land and ocean. Traditional monitoring techniques of larger areas are limited by the factor time. This means that they are time-dependent and time-consuming. Due to the expanse of the tidal flat of nearly 10,000 km2, the variability of water cover and the variability of the sediment, remote sensing has become an indispensable technique. The whole German Wadden Sea can be detected under the same environmental conditions with only two scenes of the Landsat satellite, which has been an operational satellite system since 1972. Remote sensing data support mapping and monitoring programmes. They support the identification of proxi-parameters and indicators and fill the temporal gap between in-situ data and field measurements.
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Transport time scales are useful tools to quantify the importance of hydrodynamic processes in the transport and fate of [[pollutant|pollutants]] in coastal and estuarine water systems. Indeed, the water quality of a system depends crucially on the retention of [[pollutant|pollutants]] within the system and its ability to flush them out. Transport time scales are often compared with the [[pollutant]] source time scales or biogeochemical processes to evaluate the relative importance of physical and water quality processes. <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> <ref name="Salomon">Salomon J.C. and Pomepuy M. (1990). Mathematical modeling of bacterial contaminationof the Morlaix estuary (France). ''Water Research'' '''24(8)''' 983-994.</ref> They are also used to understand population dynamics <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> and to serve as indicators to classify and compare estuarine systems.<ref name="Jay:>Jay D. (1994). ''Residence times, box models and shear fluxes in tidal channel flows, Changes in Fluxes in Estuaries'', Dyer and Orth (eds.), 3-12, Olsen and Olsen, Fredensborg, Denmark.</ref>

Revision as of 15:41, 22 September 2008

Time scales for pollution assessment

Time scales for pollution assessment can be considered using three commonly used methods: 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.

Transport time scales are useful tools to quantify the importance of hydrodynamic processes in the transport and fate of pollutants in coastal and estuarine water systems. Indeed, the water quality of a system depends crucially on the retention of pollutants within the system and its ability to flush them out. Transport time scales are often compared with the pollutant source time scales or biogeochemical processes to evaluate the relative importance of physical and water quality processes. [1] [2] They are also used to understand population dynamics [1] and to serve as indicators to classify and compare estuarine systems.[3]
  1. ↑ 1.0 1.1 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.
  2. ↑ Salomon J.C. and Pomepuy M. (1990). Mathematical modeling of bacterial contaminationof the Morlaix estuary (France). Water Research 24(8) 983-994.
  3. ↑ Jay D. (1994). Residence times, box models and shear fluxes in tidal channel flows, Changes in Fluxes in Estuaries, Dyer and Orth (eds.), 3-12, Olsen and Olsen, Fredensborg, Denmark.
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