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Modelling dissolved organic carbon turnover in humic Lake Örträsket, Sweden.
Swedish Meteorological and Hydrological Institute.
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Climate Impacts Research Centre, Abisko, Sweden \ Dept. of Ecology and Environmental Science, Umeå University, Sweden.
Dept. of Ecology and Environmental Science, Umeå University, Sweden.
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2001 (English)In: Environmental Monitoring & Assessment, ISSN 0167-6369, E-ISSN 1573-2959, Vol. 6, no 3, 159-172 p.Article in journal (Refereed) Published
Abstract [en]

The organic carbon balance of a lake with high input of allochthonous organic carbon is modelled integrating physical, chemical and biological processes. The physical model captures the behaviour of real thermal stratification in the lake for different flow situations during the period 1993–1997. The dissolved organic carbon model is based on simulated trajectories of water parcels. By tracking parcels, account is kept of environmental factors such as temperature and radiation as well as DOC quality for each parcel. The DOC concentration shows seasonal variations primarily dependent on inflow. The organic matter degradation (bacterial- and photodegradation) in the lake amounts to 1.5–2.5 mg C l–1 yr–1, where photooxidation is responsible for approximately 10%. The estimated DIC production in the lake is large compared to sediment mineralisation and primary production. The main conclusion is that the model with the selected parameterisations of the degradation processes reasonably well describes the DOC dynamics in a forest lake.

Place, publisher, year, edition, pages
2001. Vol. 6, no 3, 159-172 p.
Keyword [en]
humic substances, modelling
National Category
Social Sciences Interdisciplinary
URN: urn:nbn:se:liu:diva-30604DOI: 10.1023/A:1011953730983Local ID: 16195OAI: diva2:251427
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-07-09Bibliographically approved
In thesis
1. Modelling organic matter dynamics in aquatic systems
Open this publication in new window or tab >>Modelling organic matter dynamics in aquatic systems
2000 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Organic matter is a small but active part of the global carbon cycle. About one third is stored in the oceans where it has a relatively short residence time. The rest is found in the terrestrial biomass and in the soil. Aquatic systems exchange C02 with the atmosphere. Autotrophic organisms fix C02 into their biomass, while heterotrophic organisms respire C02 when utilising organic matter. Systems with large supply of organic matter by inflow can be net heterotrophic, which thus release more C02 than what they fix.

Two systems are studied, the Lake Ortrasket in northern Sweden and the Baltic Sea. In the Baltic primary production is the main source of organic matter, while in the lake dissolved organic matter from inflow dominates. Other characteristics of the Baltic Sea are that it is brackish and has a long residence time compared to the freshwater lake. These systems are studied with different types of models.

For the Baltic proper deep water, an inverse model of the water, salt and heat fluxes was used to estimate an oxygen budget including oxygen consumption. The oxygen levels in the Baltic proper deep water are critical due to the low supply and large consumption. The oxygen consumption is mainly due to organic matter degradation. The low oxygen and salinity levels in the Baltic have consequences for, among other things, the cod spawning success.

The lake model is a mechanistic model of dissolved organic carbon based on a Lagrangian fluid particle model and a one-dimensional physical model. The results show that Lake Ortrasket is a net heterotrophic system. In spite of the differences between the systems, both seems to have similar organic matter degradation rates, ~50 g C m-2 yr-1.

To supplement, time series of phosphate concentration were studied in the Baltic proper surface layer. These show seasonal variations coupled to the primary production, and this time dependence was modelled. The main purpose of the model is to complete corrupt observation time series, which is useful for environmental model studies.

Place, publisher, year, edition, pages
Motala: Kanaltryckeriet, 2000. 77 p.
Linköping Studies in Arts and Science, ISSN 0282-9800 ; 214
Vatten, Kol, Oceanografi, Hydrologi
National Category
Social Sciences Interdisciplinary
urn:nbn:se:liu:diva-32133 (URN)17993 (Local ID)91-7219-825-7 (ISBN)17993 (Archive number)17993 (OAI)
Public defence
2000-09-22, Hörsal Planck, Fysikhuset, Universitetsområdet Valla, Linköping, 10:00 (Swedish)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2014-08-27Bibliographically approved

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Rahm, Lars
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