2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
The dating using 137 Cs indicates the position of the 1986
and 1961-2 events. The organic carbon, total sulphur, PAHs
and PCBs provide a tentative pattern related to depositional
history and flow rate. The geochemical profiles show a
general upward increase in eutrophication and organic matter
accumulation associated with increased cyanobacterial
blooms. The sum of nine PAHs often exceeds the 10 mg kg –1
EPA limit value and their pyrogenic character suggests an origin
in low-quality fuel and furnaces used in the villages and
recreational facilities in the watershed.
Fig. 2. Vertical changes in organochlorine pollutants levels in
one-meter-deep well core profiles from the Brno Lake (2001)
The higher-chlorinated PCB congeners 138, 153 and
180, and p,p-DDE (a highly stable aerobic metabolite of the
notorious insecticide p,p-DDT) are the most abundant organochlorine
compounds detected in the sediments. PCBs show
upward increase from a depth of 0.6 (0.8–0.5) m (Fig. 2.),
which marks the beginning of the use of PCBs and DDT. A
s372
stagnation in the PCB and DDT concentration is observed in
the upper part of the profile (0.25–0.00 m) deposited during
the last decade. The differences in POP concentrations found
in individual cores and layers are closely associated with
variable sedimentation rates and occurrences of bottom currents
affecting the organic matter deposition.
Conclusions
The pollution archive related to the depositional history
of the Brno Lake suggest at least 5 cycles, each about 60 cm
thick, defined by the maxima in magnetic susceptibility and
minima in total organic carbon which are associated with
major floods or migration of bottom currents. The amount
of POPs is low in more sandy early sediments, increases
at a specific depth and age throughout the basin and finally
stagnates during the last decade of mud deposition indicating
decreased input of POPs into the environment.
This work has been supported by The Ministry of the
Environment of the Czech Republic,Project SP/1b7/156/07.
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