Present nitrogen and carbon dynamics in the Scheldt estuary using a novel 1-D model

TY - JOUR

T1 - Present nitrogen and carbon dynamics in the Scheldt estuary using a novel 1-D model

AU - Hofmann, A.F.

AU - Soetaert, K.E.R.

AU - Middelburg, J.J.

N1 - Reporting year: 2008 Metis note: 4331;CEME; ES; file:///C:/pdfs/PDFS2008/Hofmann_ea_4331.pdf

PY - 2008

Y1 - 2008

N2 - A 1-D, pelagic, reactive-transport model of a completely mixed, turbid, heterotrophic estuary – the Scheldt estuary – is presented. The model resolves major carbon and nitrogen species and oxygen, as well as pH. The model features two organic matter degradation pathways, oxic mineralisation and denitrification, and includes primary production as well as nitrification. Apart from advective-dispersive transport along the length axis, the model also describes O2, CO2, and N2 air-water exchange. The aim of this study is to present a model which is as simple as possible but still fits the data well enough to determine the fate and turnover of nutrients entering the estuary and their spatial patterns in the years 2000 to 2004. Nitrification is identified as one of the most important processes in the estuary, consuming a comparable amount of oxygen as oxic mineralisation (1.7 Gmol O2 y−1 vs. 2.7 Gmol O2 y−1). About 10% of the 2.5 Gmol of nitrogen entering the estuary per year is lost within the estuary due to denitrification. Nitrogen and carbon budgets are compared to budgets from the seventies and eighties, showing that nitrification activity has peaked in the eighties, while denitrification steadily declined. Our model estimates an average CO2 emission of 3.3 Gmol y−1 in the years 2001 to 2004, which is a comparatively low estimate in the context of previous estimates of CO2 export from the Scheldt estuary.

AB - A 1-D, pelagic, reactive-transport model of a completely mixed, turbid, heterotrophic estuary – the Scheldt estuary – is presented. The model resolves major carbon and nitrogen species and oxygen, as well as pH. The model features two organic matter degradation pathways, oxic mineralisation and denitrification, and includes primary production as well as nitrification. Apart from advective-dispersive transport along the length axis, the model also describes O2, CO2, and N2 air-water exchange. The aim of this study is to present a model which is as simple as possible but still fits the data well enough to determine the fate and turnover of nutrients entering the estuary and their spatial patterns in the years 2000 to 2004. Nitrification is identified as one of the most important processes in the estuary, consuming a comparable amount of oxygen as oxic mineralisation (1.7 Gmol O2 y−1 vs. 2.7 Gmol O2 y−1). About 10% of the 2.5 Gmol of nitrogen entering the estuary per year is lost within the estuary due to denitrification. Nitrogen and carbon budgets are compared to budgets from the seventies and eighties, showing that nitrification activity has peaked in the eighties, while denitrification steadily declined. Our model estimates an average CO2 emission of 3.3 Gmol y−1 in the years 2001 to 2004, which is a comparatively low estimate in the context of previous estimates of CO2 export from the Scheldt estuary.

U2 - 10.5194/bg-5-981-2008

DO - 10.5194/bg-5-981-2008

M3 - Article

VL - 5

SP - 981

EP - 1006

JO - Biogeosciences

JF - Biogeosciences

SN - 1726-4170

IS - 4

ER -