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A field investigation of the relationship between zinc
and acid volatile sulfide concentrations in freshwater sediments
Gerald T. Ankley1,
Karsten Liber2, Daniel J.
Call2, Thomas P. Markee2,
Timothy J. Canfield3 &
Christopher G. Ingersoll3
1Mid-continent Ecology
Division, U.S. Environmental Protection Agency,
6201 Congdon Boulevard, Duluth,Minnesota 55804, USA
2Lake Superior Research
Institute, University of Wisconsin-Superior,
1800 Grand Avenue, Superior, Wisconsin54880, USA
3National Biological Service,
Midwest Science Center, 4200 New Haven Road,
Columbia, Missouri 65201, USA
Received 3 April 1996; accepted in
final form 28 August 1996
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Abstract
Understanding relationships between cationic metals
such as cadmium, copper, nickel, lead and zinc, and amorphous iron
sulfides, measured as acid volatile sulfide (AVS), is key to predicting
metal bioavailability and toxicity in sediments. The objective of
the present study was to assess seasonal and spatial variations
of AVS in freshwater sediments contaminated with zinc. Sediments
were sampled from three streams with varying levels of zinc contamination
at two different times, March and June of 1995, representing cold-
and warm-weather situations. Interstitial (pore) water concentrations
of zinc, and solid phase concentrations of AVS and zinc were measured
in surficial and deep sediment horizons. Toxicity tests (10-d) with
the amphipod Hyalella azteca were conducted using intact
cores. Sediment zinc concentrations from six sites within the primary
test stream differed by about five-fold, and also varied seasonally.
Acid volatile sulfide concentrations were generally lower than those
of zinc, and pore water zinc concentrations typically were elevated.
There was a positive correlation between solid-phase AVS and zinc
concentrations, suggesting that the system was dominated by zinc,
as opposed to iron sulfides. In contrast to expectations arising
from some studies of seasonal variations of AVS in iron-dominated
systems, AVS concentrations were smaller in June than in March.
However, this was likely due to a major storm event and associated
sediment scouring before the June sampling, rather than to seasonal
processes related to variations in temperature and dissolved oxygen.
Based upon an indirect analysis of depth variations in AVS, there
was some indication that zinc sulfide might be less prone to oxidation
than iron sulfide. There was a strong correlation between toxicity
of the sediment samples to H. azteca and interstitial water
concentrations of zinc; however, the possible contribution of other
contaminants to sediment toxicity cannot be dismissed.
Keywords: sediment, acid volatile sulfide, zinc, interstitial
water, bioavailability, toxicity
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