MP4 Metals in the Environment: Aquatic Biological Perspectives
Room 16A/B, Level 4
2:10 PM - 5:30 PM, Monday, 10 November 2003
Chair: Green, Andrew ,
Co-chair: Bielmyer, Gretchen ,
(121) Field validation of zinc effects and the SEM-AVS model: Benthic colonization and in situ toxicity.
Burton, G1, Nguyen, L2, Janssen, C2, McWilliam, R1, Bossuyt, B2, Beltrami, M3, Baudo, R3, Green, A4, 1 Wright State University, Dayton, OH, USA2 University of Ghent, Ghent, Belgium3 Italian Institute of Hydrobiology, Pallanza, Italy4 International Lead Zinc Research Organization, Research Triangle Park, NC, USA
ABSTRACT- A long-term, field study was conducted to validate concentrations of zinc in freshwater sediments that are tolerated by benthic macroinvertebrate communities and determine whether there is a relationship with the acid volatile sulfide (AVS)-simultaneously extracted metal (SEM) model. The study design consisted of spiking sediments with 400 and 1,200 mg/Kg DW Zn from 4 differing environments in Europe, including two lake and two riverine ecosystems. This resulted in a wide range of SEM-AVS ratios. Colonization trays were sampled seasonally, ranging from 6 to 37 weeks of exposure. In situ toxicity tests were also conducted using the amphipod Hyalella azteca, the midge Chironomus riparius, or the cladoceran Daphnia magna. These tests were conducted for two to four days to determine if overlying water toxicity existed at the test sites and to detect acute toxicity from the Zn spiked sediments. In sediments where the SEM:AVS ratio or the AVS and organic carbon normalized fractions exceeded 8 and 583 umol/g OC, toxicity was observed from the Zn spiked sediments. Conversely, when the SEM:AVS ratio or carbon normalized AVS fractions were below 2 or 100 umol/g OC, no toxicity was observed. In the range of 148 to 154 umol/g OC, toxicity varied in two treatments. Total Zn concentrations in sediments showed no relationship to benthic effects. The no observed effect level appeared to be near a SEM:AVS ratio of 2, with slight to no effects between 2.34 and 2.94. No sites with ratios below 2 showed any adverse effects. Acute toxicity was not observed in the in situ toxicity tests, except from one high Zn treatment (1,200 mg/Kg DW) in Italy within 24 hr of initial spiking and deployment. The results support the hypothesis that Zn bioavailability in freshwater sediments is accurately predicted by the SEM-AVS models.
Key words: AVS, sediment, benthos, in situ