PM02 Metals in the Environment: Aquatic Biological Perspectives
Exhibit Hall
8:00 AM - Monday, 10 November 2003
(PM044) Studying the accumulation of some trace metals in the larvae of the midge Chironomus riparius by three single extraction procedures.
Qadah, Diab1, Bervoets, Lieven1, Blust, Ronny1, 1 Department of Biology, Univeristy of Antwerp, Antwerp, Belgium
ABSTRACT- Sediments are a complex mixture of a number of solid phases that may include clay, silica, organic matter, metal oxides and sulfides where contaminants as metals might be trapped and concentrated. Benthic organisms that are continuously in direct contact with bottom sediments are therefore at risk due to their exposure to these contaminants. To evaluate the mobility and potential availability of trace metals to marine organisms, standard extraction procedures are always recommended, however, some of them may not necessarily reflect what is happening in the real environment, particularly, with respect to the extraction time required to reach equilibrium. In this study, the effect of the extraction time of three standard single extraction procedures (0.01M CaCl2, 1 M NH4NO3, and 0.05M EDTA) on the amount of metal extracted was assessed. In addition, relation with accumulated metal levels in larvae of the midge Chironomus riparius was assessed enabling us to evaluate the biological relevance of the three extraction procedures. At 12 sites in small watercourses, sediment was collected and placed in small enclosures along with 100 first-instar midge larvae. After 4 weeks of exposure, sediment and larvae were collected from the cages, extraction procedures performed and metal levels were measured. Our results indicated that for ammonium nitrate and to a lesser extent for calcium chloride, two hours extraction time, as recommended by the standard procedures, might be sufficient to reach the equilibrium status for several elements. Whereas, for the EDTA extraction, the results revealed that two hours extraction was not enough to reach the equilibrium status for most of the studied elements. Relations between accumulated metal levels in larvae of the midge Chironomus riparius, metal levels in the three extractants as well as metal levels in the water are discussed.
Key words: Extraction, Trace metals, Accumulation, Sediments