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Nitrogen loss rates in streams: Scale-dependence and up-scaling methodology
KTH, Superseded Departments, Land and Water Resources Engineering.
2004 (English)In: Geophysical Research Letters, ISSN 0094-8276, Vol. 31, no 13, L13501- p.Article in journal (Refereed) Published
Abstract [en]

We show that the large spatial aggregation of model parameters in common catchment scale nitrogen budget modeling leads to artifacts that may, for instance, be a factor in explaining reported decreases of calibrated instream nitrogen loss rates, lambda(s)(*), with increasing stream size. In general, the common assumption of a single representative solute travel time for an entire stream reach may lead to considerable underestimation of the actual underlying local biogeochemical loss rate lambda(s) by lambda(s)(*), which increases with actual lambda(s) value and/ or increasing mean solute travel time and travel time variability in the stream. We propose an up-scaling methodology to overcome such model artifacts, in form of closed-form expressions of catchment-scale, in-stream nitrogen delivery factors for diffuse and point sources, as functions of local-scale nitrogen loss rates, lambda(s).

Place, publisher, year, edition, pages
2004. Vol. 31, no 13, L13501- p.
Keyword [en]
sorptive solute, mass arrival, transport, eutrophication, groundwater, watersheds, catchments, retention, marine
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:kth:diva-5539DOI: 10.1029/2004GL019996ISI: 000222654100003ScopusID: 2-s2.0-4544280420OAI: diva2:9938
QC 20100907Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2011-09-26Bibliographically approved
In thesis
1. Physical process effects on catchment-scale pollutant transport-attenuation, coastal loading and abatement efficiency
Open this publication in new window or tab >>Physical process effects on catchment-scale pollutant transport-attenuation, coastal loading and abatement efficiency
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Pollutants follow various subsurface and surface water pathways from sources within a catchment to its outlet and may cause detrimental effects on downstream water quality and ecosystems. Along their different transport pathways through a catchment, pollutants may be attenuated subject to different physical and biogeochemical processes. In this thesis, physical process effects on such catchment-scale pollutant transport and attenuation, resulting coastal pollutant loading and its efficient abatement are investigated. For this purpose, pollutant transport-attenuation is modeled both generically using a Lagrangian Stochastic Advective-Reactive (LaSAR) approach and site specifically for the Swedish Norrström basin using the GIS-based dynamic nitrogen transport-attenuation model POLFLOW. Furthermore, the role of such modeling for catchment-scale pollutant abatement is also investigated by use of economic optimization modeling.

Results indicate that appropriate characterization of catchment-scale solute transport and attenuation processes requires accurate quantification of the specific solute pathways from different sources in a catchment, through the subsurface and surface water systems of the catchment, to the catchment outlet. The various physical processes that act on solute transported along these pathways may be quantified appropriately by use of relevant solute travel time distributions for each water subsystem that the pathways cross through the catchment. Such distributions capture the physical solute travel time variability from source to catchment outlet and its effects on reactive pollutant transport. Results of this thesis show specifically that neglect of such physical solute travel time variability in large-scale models of nitrogen transport and attenuation in catchments may yield misleading model estimates of nitrogen attenuation rates.

Results for nitrogen abatement optimization in catchments further indicate that inefficient solutions for coastal nitrogen load reduction may result from simplifying physical transport assumptions made in different catchment-scale nitrogen transport-attenuation models. Modeling of possible future nitrogen management scenarios show also that slow nitrogen transport and reversible mass transfer processes in the subsurface water systems of catchments may greatly delay and temporally redistribute coastal nitrogen load effects of inland nitrogen source abatement over decades or much longer. Achievement of the national Swedish environmental objective to reduce the anthropogenic coastal nitrogen loading by 30% may therefore require up to a 40% reduction of both point sources, for achieving a fast coastal load response, and diffuse sources, for maintaining the coastal load reduction also in the long term.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 1x, 25 p.
Trita-LWR. PHD, ISSN 1650-8602 ; 1028
Efficient pollutant load abatement, groundwater-surface water interactions, biogeochemical cycles, nitrogen, Lagrangian stochastic travel time approach, GIS
National Category
Oceanography, Hydrology, Water Resources
urn:nbn:se:kth:diva-3900 (URN)91-7178-315-6 (ISBN)
Public defence
2006-04-21, D3, Lindstedtsv 5, Kungl tekniska högskolan, Stockholm, Sverige, 10:00
QC 20100908Available from: 2006-04-05 Created: 2006-04-05 Last updated: 2010-09-08Bibliographically approved

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