The aim of this study was to get a better knowledge of the metal pollution and the mining
history of the Falun area. It adds new information on the geochemistry of the lakes and the
beginning of mining in the Falun region, together with the influence of early land use. The
main focus is on three lakes Hagtjärnen, Stugutjärnen and Nästjärnen, which were previously
dated and analyzed regarding acidification by Anna Ek. Additional supporting information is
provided from records from 10 other lakes, which are located at distances between 0-27 km
from the Falun Copper mine. Another specific focus is on the lake Tisken, which has been
assumed over the past 50 years to represent faithful historical record of mining in the Falun
area. In this study this lake record was dated and analyzed, too. The analyses of all the lakes
included resulted in four significant phases of environmental change, indicating the start of
agriculture and mining, the development of each sector, as well as the sharp increase in
pollution in the modern time period. Phase I covers the time period A.D. 700-1000 and
represents the time of the early beginning of land use and small scale mining activities. Phase
II represents the time between A.D. 1200 to 1450, which is dominated by an ongoing
development of mining and a sharp increase in metal concentrations and occurrence of
cultivated plants and plants favored by disturbance from A.D. 1450 onwards. The third phase,
representing the year A.D. 1540, clearly displays another period of sharp increases among the
metal concentrations, which coincides with a peak in Cu production volumes. Phase IV
covers the time period A.D. 1750-1900, referred to as Modern time, and features a clear
increase in Pb pollution, which is linked to the introduction of tetra ethyl Pb in the 1970s.
Other metals increase also, together with cultivated plants like cereals, indicating an ongoing
expansion of mining and agriculture. The results also indicate that Cu was not emitted as far
as other elements, like for example Pb, which led to great pollution only in the lakes close to
the Falun mine.
Another important finding is that the lake Tisken does not represent a continual historical
record, because the sediment is not a chronological sequence and instead likely represents
mostly a catastrophic input of debris of mixed age. The C-14 dating shows, that the sediment
is mixed and disturbed in Tisken. As a consequence, the long-standing interpretation of
Tisken’s sediment record as an archive for the historical start and late development of mining
at the Falun copper mine is incorrect