|SREL Reprint #0764|
Fates of Cadmium Introduced into Channels Microcosm
P. Giesy, John W. Bowling, Henry J. Kania, Robert L. Knight, and Susan Mashburn
Five and 10 mg Cd 1-1 were
continuously input to aquatic microcosm channels for one year.
Cadmium accumulation in both biotic and abiotic components was
determined. Cadmium inputs and
outputs equilibriated within approximately 20 days of initial Cd inputs.
Most community components accumulated Cd proportional to Cd water
concentrations. Equilibrium Cd
concentrations of sediments, aufwuchs, macrophytes, chironomids, and mosquito
fish exposed to 10 mg
Cd 1-1 were 0.59, 55,
250, 40, and 40 mg
Cd g-1, dry weight, respectively.
Cadmium was rapidly eliminated from all biotic components when Cd inputs
were terminated. Cadmium
concentrations were similar to those in control channels within a few weeks in
the aufwuchs community to a few months in macrophytes after Cd inputs were
terminated. Cadmium uptake fluxes
by the aufwuchs community and mosquito fish were first order, with respect to Cd
concentration in the water. The
rate constants for uptake and depuration for the aufwuchs community were 0.42
and 0.66 d-1, respectively (concentration basis).
The rate constants for uptake and depuration of Cd by mosquito fish were
approximately 25 and 0.004 d-1, respectively (concentration basis).
Cadmium concentrations in organic headpool sediments had not
significantly decreased six months after cessation of Cd inputs, which indicates
that the abiotic half time for contaminated organic sediments is very long.
Half times for elimination from channel sand sediments were 72 and 38 d
for 5 and 10 mg
1-1 exposure, respectively, after Cd inputs were terminated.
Cd concentrations in macroinvertebrates varied seasonally.
The carrying capacity of the channels microcosm limited the number of
samples of secondary and tertiary consumers which could be sampled.
It was concluded that experimental channels of the size described here
were not appropriate as screening tools for the fates of trace contaminants, but
were effective for the study of trace contaminants, especially in conjunction
with mathematical modeling efforts and less complex laboratory studies.
SREL Reprint #0764
Giesy, J.P., J.W. Bowling, H.J. Kania, R.L. Knight, and
S. Mashburn. 1981. Fates of cadmium introduced into channels
microcosm. Environment International 5:159-175.