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Credible acidification assessments in a changeable environment

estimating the natural acidity of boreal lakes in Sweden

Erlandsson, Martin (2008). Credible acidification assessments in a changeable environment. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2008:52
ISBN 978-91-85913-85-5
[Doctoral thesis]

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Despite major reductions in acidifying deposition and varying degrees of recovery in acidified surface waters, there is still an urgent need to improve tools for acidification assessments on regional scales. The most accepted models for estimating acidification reference values are often too complex for this purpose. Here, a meta-model is derived from the established, dynamic MAGIC acidification model. The meta-model (metaMAGIC) relates generally available variables of contemporary water chemistry to the pre-industrial buffering capacity predicted by MAGIC. MetaMAGIC was able to reproduce the pre-industrial ANC (Acid Neutralizing Capacity) predicted by MAGIC with an absolute median error of 13.2 µeq/l (or 8 %), for 95 Swedish lakes. This approach ultimately relies on the accuracy of the MAGIC reconstructions themselves, which were compared to a set of paleolimnological reconstructions of pre-industrial pH. No bias was detected between the two reconstructions (mean difference was 0.03 pH-units for 55 lakes), provided that lake specific estimates of TOC (Total organic carbon) and partial pressure of CO2 are used when converting MAGIC ANC to pH. A complication in acidification assessments is that surface water acidity varies on all time scales, from diel to centennial. The variability in pH is here compared to the criteria for acidification in the Swedish EQC (Environmental Quality Criteria), where a decline in pH of 0.4 units or more from the natural state is defined as significant acidification. When reference time series of pH were reconstructed for 95 lakes, it was found that the seasonal variability exceeded 0.4 units over 15 years in all lakes. On a longer time scale, a decade of TOC increase in many lakes has lowered pH. For 24 lakes with 30-140 % increases in TOC, the median effect on pH was 0.24 pH-units. The TOC increase affects the recovery from acidification and raises questions about what the “natural state” really is. The answer will have a profound impact on assessments of acidification.

Authors/Creators:Erlandsson, Martin
Title:Credible acidification assessments in a changeable environment
Subtitle:estimating the natural acidity of boreal lakes in Sweden
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2008
Number of Pages:52
ALLI. Erlandsson, M., Bishop, K., Fölster, J., Guhrén, M., Korsman, T., Kronnäs, V., Moldan, F. (2008). A comparison of MAGIC and paleolimnological predictions of pre-industrial pH for 55 Swedish lakes. Environmental Science and Technology 42: 43-48. II. Erlandsson, M., Fölster, J., Wilander, A., Bishop, K. (2008). A metamodel based on MAGIC to predict the pre-industrial acidity status of surface waters. Aquatic Sciences 70: 238-247. III. Erlandsson, M., Fölster, J., Laudon, H., Weyhenmeyer, G., Bishop, K. (2008). Natural variability in lake pH on seasonal, interannual and decadal time scales: Implications for assessment of human impact. Environmental Science and Technology 42: 5594-5599. IV. Erlandsson, M., Cory, N., Köhler, S., Bishop, K. Changes in acidification status for 24 Swedish lakes due to increasing levels of organic acids. (manuscript).
Place of Publication:Uppsala
Publisher:Institutionen för vatten och miljö, Sveriges lantbruksuniversitet
ISBN for printed version:978-91-85913-85-5
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:lakes, acidity, ph, acidification, environmental impact, environmental impact assessment, models, sweden
Keywords:pH modelling, reference values, temporal variability, environmental quality criteria, ecological status, MAGIC, ANC, DOC, CO2
Permanent URL:
ID Code:1807
Department:(NL, NJ) > Dept. of Aquatic Sciences and Assessment
Deposited By: Martin Erlandsson
Deposited On:04 Sep 2008 00:00
Metadata Last Modified:02 Dec 2014 10:14

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