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Inorganic nitrogen retention in acid‐sensitive lakes in southern Norway and southern Ontario, Canada—a comparison of mass balance data with an empirical N retention model
Author(s) -
Kaste Ø.,
Dillon P. J.
Publication year - 2003
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.1249
Subject(s) - hydrology (agriculture) , environmental science , ammonium , norwegian , nitrogen , tin , acid deposition , nitrate , chemistry , soil science , ecology , geology , soil water , biology , linguistics , philosophy , geotechnical engineering , organic chemistry
In‐lake retention of inorganic nitrogen species (nitrate and ammonium) was estimated from mass balances in five acid‐sensitive lakes in southern Norway and eight in southern Ontario, Canada, to evaluate an empirical in‐lake N retention ( R N ) model. This model is included in the First‐order Acidity Balance (FAB) model, which currently is used for calculation of critical acid loads and exceedances in many countries. To estimate in‐lake R N , the FAB model uses a recommended mass transfer coefficient ( S N ) of 5 m year −1 , which mainly is derived from NO 3 − mass balances in Canadian lakes. To date, the in‐lake R N model has not been evaluated for large parts of Europe. At the Norwegian study sites receiving the highest N deposition (>120 meq m −2 year −1 ) the net in‐lake retention of inorganic N (TIN) exceeded the corresponding terrestrial retention by a factor of 1·1–2·6. Despite differences in N loading and hydrology at the Norwegian and Canadian sites, both the mean mass transfer coefficients for NO 3 − ( S NO3 ; 6·5 versus 5·6 m year −1 ) and TIN ( S TIN ; 7·9 versus 7·0 m year −1 ) were of comparable magnitude. Both mean values and ranges of S NO3 suggest that the default S N value presently recommended for FAB model applications seems valid over a large range in N inputs and areal water loads ( q s ). However, owing to the relatively few data available for lakes with high q s values (15–150 m year −1 ), it is recommended that more lakes within this range be included in future studies to obtain a more precise prediction of in‐lake N retention over a wide q s gradient. Also, when considering that the FAB model treats all inorganic N leaching from a catchment as NO 3 − , it seems reasonable to use a default S TIN value instead of just S NO3 when estimating in‐lake R N . In that case, the in‐lake R N presently calculated by the FAB model might be slightly underestimated. Copyright © 2003 John Wiley & Sons, Ltd.