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Assessing the parameterisation of the settling flux in a depth-integrated model of the fate of decaying and sinking particles, with application to fecal bacteria in the Scheldt Estuary

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Debrauwere, Anouk [UCL] Deleersnijder, Eric [UCL]

The fate of reactive tracers is often modelled by depth-averaged equations. When integrating the depth-resolved equations, it appears that the term describing the settling of particles is dependent on the concentration just above the bottom. Because in a depth-averaged framework this quantity is not available, the settling term needs to be parameterised. The most natural choice is to make the settling flux dependent on the average concentration. This approximation is acceptable if the water column is well mixed, but these conditions are not necessarily met in real applications. Therefore, this study aims at assessing and understanding the error made by using a depth-averaged model in a range of realistic conditions. For the definition of these conditions, typical values for the Scheldt Estuary and the Dutch-Belgian coast were taken. The realistic inspiration for the reactive tracer in this study is the fecal bacterium Escherichia coli, whose own dynamics are characterised by settling and gradual decay by mortality. In an attempt to understand the relative importance of several factors like settling, mortality, mixing and stratification on the error made by a depth-averaged approach, a number of simplified test cases were investigated. It follows that, as expected, the error is acceptable if the situation is mixing-dominated. However, the effect of mortality and stratification was less obvious in advance. For instance, it appeared that errors can also be significant if settling and mortality have the same characteristic timescales. Stratification often has the effect to increase the error made by the depth-averaged model.

Document type Article de périodique (Journal article) – Article de recherche
Access type Accès restreint
Publication date 2010
Language Anglais
Journal information "Environmental Fluid Mechanics (Dordrecht, 2001)" - Vol. 10, no. 1-2, p. 157-175 (2010)
Peer reviewed yes
Publisher Springer (Dordrecht)
issn 1567-7419
e-issn 1573-1510
Publication status Publié
Affiliation UCL - SST/IMMC - Institute of Mechanics, Materials and Civil Engineering
Keywords Settling ; Mixing ; Mortality ; Decay ; Pycnocline ; Residence time ; Depth-integrated model ; Reactive tracer
Links
  1. Alvarez-Vázquez LJ, Martínez A, Vázquez-Méndez ME, Vilar MA (2006) Optimal location of sampling points for river pollution control. Math Comput Simul 71: 149–160
  2. Bolin B, Rodhe H (1973) A note on the concepts of age distribution and transit time in natural reservoirs. Tellus 25: 58–62
  3. Burchard H, Deleersnijder E, Meister A (2003) A high order conservative Patankar-type discretisation for stiff systems of production-destruction equations. Appl Numer Math 47: 1–30
  4. Burchard H, Deleersnijder E, Meister A (2005) Application of modified Patankar schemes to stiff biogeochemical models for the water column. Ocean Dyn 55: 326–337
  5. Dahlquist G, Bjorck A (1974) Numerical methods. Prentice-Hall, City
  6. Deleersnijder Eric, Beckers Jean-Marie, Campin Jean-Michel, El Mohajir Mohammed, Fichefet Thierry, Luyten Patrick, Some mathematical problems associated with the development and use of marine models, The Mathematics of Models for Climatology and Environment (1997) ISBN:9783642644726 p.39-86, 10.1007/978-3-642-60603-8_2
  7. Deleersnijder E, Beckers J-M, Delhez EJM (2006) The residence time of settling particles in the surface mixed layer. Environ Fluid Mech 6: 25–42
  8. Delhez EJM, Heemink AW, Deleersnijder E (2004) Residence time in a semi-enclosed domain from the solution of an adjoint problem. Estuar Coast Shelf Sci 61: 691–702
  9. Delhez EJM (2006) Transient residence and exposure times. Ocean Sci 2: 1–9
  10. Delhez EJM, Deleersnijder E (2006) The boundary layer of the residence time field. Ocean Dyn 56: 25–42
  11. Garcia-Armisen T., Thouvenin B., Servais P., Modelling faecal coliforms dynamics in the Seine estuary, France, 10.2166/wst.2006.466
  12. Garcia-Armisen T, Servais P (2008) Partitioning and fate of particle-associated E. coli in river waters. Water Environ Res 80(3): 282–288
  13. George I, Anzil A, Servais P (2004) Quantification of fecal coliform inputs to aquatic systems through soil leaching. Water Res 38: 611–618
  14. Hofmann AF, Soetaert K, Middelburg JJ (2008) Present nitrogen and carbon dynamics in the Scheldt estuary using a novel 1-D model. Biogeosciences 5: 981–1006
  15. Inoue M, Wiseman WJ Jr (2000) Transport, mixing and stirring processes in a Louisiana estuary: a model study. Estuar Coast Shelf Sci 50: 449–466
  16. Jamieson R, Gordon R, Joy D, Lee H (2004) Assessing microbial pollution of rural surface waters. A review of current watershed scale modeling approaches. Agric Water Manage 70: 1–17
  17. JAMIESON R, JOY D, LEE H, KOSTASCHUK R, GORDON R, Transport and deposition of sediment-associated in natural streams, 10.1016/j.watres.2005.04.040
  18. Patankar SV (1980) Numerical heat transfer and fluid flow. McGraw-Hill, New York
  19. Roache PJ (1972) On artificial viscosity. J Comput Phys 10: 169–184
  20. Servais Pierre, Garcia-Armisen Tamara, George Isabelle, Billen Gilles, Fecal bacteria in the rivers of the Seine drainage network (France): Sources, fate and modelling, 10.1016/j.scitotenv.2006.12.010
  21. Steets BM, Holden PA (2003) A mechanistic model of runoff-associated fecal coliform fate and transport through a coastal lagoon. Water Res 37: 589–608
  22. Takeoka H (1984) Fundamental concepts of exchange and transport time scales in a coastal sea. Cont Shelf Res 3: 311–326
  23. Vanderborght JP, Folmer IM, Aguilera DR, Uhrenholdt T, Regnier P (2007) Reactive-transport modelling of C, N and O2 in a river-estuarine-coastal zone system: application to the Scheldt estuary. Mar Chem 106: 92–110
  24. Yuan D, Lin B, Falconer RA (2007) A modeling study of residence time in a macro-tidal estuary. Estuar Coast Shelf Sci 71: 401–411
Bibliographic reference Debrauwere, Anouk ; Deleersnijder, Eric. Assessing the parameterisation of the settling flux in a depth-integrated model of the fate of decaying and sinking particles, with application to fecal bacteria in the Scheldt Estuary. In: Environmental Fluid Mechanics (Dordrecht, 2001), Vol. 10, no. 1-2, p. 157-175 (2010)
Permanent URL http://hdl.handle.net/2078.1/34198