Strategic framework document for liming of acidified
waters in Stockholm County
This report assesses trends in acidification and the status of acidified lakes
and rivers in Stockholm County (SE Sweden). It also presents a framework
for liming of lakes, which includes a liming strategy, an action plan, an
environmental quality monitoring plan and a policy for government
subsidies for liming. The action plan follows the liming strategy presented
in the Swedish national liming guidelines (Swedish Environmental
Protection Agency, Handbook 2002:1).
In order to combat acidification, approximately 30 lakes in Stockholm
County have been treated with lime since the late 1970s. Conditions in the
lakes have clearly improved, and acidic lakes are rare in Stockholm County
today. In eight of the nine reference lakes used for baseline monitoring, pH
values had increased since 1990. On average, pH values in the reference
lakes have increased by 0.013 units per year.
Treatment with lime has been so successful that Stockholm County has now
achieved one of the national interim targets for the Swedish environmental
quality objective “
Natural acidification only”. According to the interim
target, “By 2010 not more than 5 % of all lakes and 15 % of the total length
of running water in the country will be affected by anthropogenic
The lakes of Stockholm County are less affected by acidification than the
average Swedish lake, and are more resistant to deposition of sulphur and
nitrogen. In a study of 164 lakes, acid deposition exceeded the critical load
(the load below which inputs of acidic substances can be neutralized by soilweathering
processes) in eight lakes only. We estimate that at current levels
of acidic deposition, only 8 % of the lakes (66 of all 790 lakes in the county)
risk becoming acidic. This is equivalent to 66 km
2 of lake area, or 2 % of
the total lake area in the county (excluding Lake Mälaren).
2005. , 76 p.