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POTENTIAL USE AND MODIFICATION OF EXISTING MESOCOSMS FOR VAPOR PHASE PHOTOTOXICITY
Citation:
Pfleeger, T G., D M. Olszyk, AND R A. Shimabuku. POTENTIAL USE AND MODIFICATION OF EXISTING MESOCOSMS FOR VAPOR PHASE PHOTOTOXICITY. Presented at SETAC meeting, Salt Lake City, UT, November 16-20, 2002.
Description:
With vapor phase plant toxicity testing becoming a requirement in Europe, there is a pressing need to develop and implement acceptable tests protocols. The quickest way to proceed is to examine and modify existing methodologies while determining if new technologies are needed. The objective of this poster is to demonstrate the usefulness of existing field / mesocosm methodologies including exposures. Laboratory tests are fast, inexpensive and less variant than field tests. However, laboratory tests lack the ecological realism that is present in the field. Mesocosms are an attempt to link the two with some of the control of laboratory tests and the ecological interactions found in natural systems. Open-top chambers (OTCs) were probably the first large scale use of a field mesocosm methodology to study air pollutants. They have been used extensively around the world to study the effects of ozone and other air pollutants on plants. OTCs have been used with both field-grown and potted plants. We modified OTCs to grow artificial plant communities in native soils. The open tops are a single pass flow system with the pollutant injected into the air stream just prior to entering the lower third of the chamber through a plenum. This increases the opportunities for an even mixing of the toxicant across the chamber. Excess air leaves through the top of the chamber. Closed mesocosms are a more-recently developed system where the air is continuously recycled, monitored and adjusted in relation to ambient conditions. Studies have been performed in the closed mesocosms to determine integrated above- and belowground nutrient (C, N) and water budget for plants exposed to elevated CO2, air temperature and O3. Several different experimental mesocoms have been used to expose plants to formaldehyde and acidic fog, including the OTCs and specially designed greenhouse chambers. Experience with different types of mesocosms indicates that altering existing experimental facilities to meet the needs of a new type of toxicity testing is an acceptable alternative to designing new vapor testing methodologies.