Large scale patterns of chemical recovery in lakes in Norway and Sweden: Importance of seasalt episodes and changes in dissolved organic carbon

Trends from 160 lakes in Norway and Sweden for the period 1990–2004 reveal that Scandinavian lakes show clear signs of recovery from acidification. Sulphate has decreased and ANC, alkalinity and pH have increased. During the last 5 a, the decline in SO 4 - has ceased, whereas ANC continues to increa...

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Bibliographic Details
Published in:Applied geochemistry 2007-06, Vol.22 (6), p.1174-1180
Main Authors: Skjelkvåle, Brit Lisa, Borg, Hans, Hindar, Atle, Wilander, Anders
Format: Article
Language:English
Subjects:
Earth sciences
Earth, ocean, space
Engineering and environment geology. Geothermics
Exact sciences and technology
Geochemistry
Pollution, environment geology
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Summary:Trends from 160 lakes in Norway and Sweden for the period 1990–2004 reveal that Scandinavian lakes show clear signs of recovery from acidification. Sulphate has decreased and ANC, alkalinity and pH have increased. During the last 5 a, the decline in SO 4 - has ceased, whereas ANC continues to increase. The results also show decreasing trends for Cl, while Na shows no or very small trends. The increase in the Na/Cl-ratio explains part of the increase in ANC. On average for the period 1990–2004 the decrease in Cl contributes 20–50% of the increase in ANC. The main cause of the trends in Cl in southern Sweden and Norway are probably due to declining seasalt inputs due to a higher frequency of heavy storms in the late 1980s and early 1990s. TOC exhibits increasing trends in regions with median TOC concentrations > 3 mg C/L, however, this does not contribute significantly to the observed increase in ANC.
ISSN:0883-2927
1872-9134
DOI:10.1016/j.apgeochem.2007.03.040