In the single lake profiles (Fig. ), three points in time of increased concentrations are visible, mirroring the averaged profile of the lakes of Fig. : The first is between 1955 and 1965, especially prominent in Lakes FH, BL, OR and PL, while in Lake SL it is five years later. The second event is in the 1970s and can be seen in Lakes AR, CR, and, PL. Lake TF is the only lake where the third event in ca.