Trifluoroacetic Acid: Its Environmental Occurrence and Its Effects in Biota in Seasonal Wetlands Downwind from Sources of Precursor HCFCs and HFCs

该提案已提交给环境地球化学和生物地球化学（EGB）招标NSF 96-152。下面描述的项目是由大气科学部和地球科学部联合支持的。本项目研究三氟乙酸（TFA）的环境发生及其对生物群的影响。TFA是某些氯氟烃和氢氟碳化物在大气中降解的产物，它们是氯氟烃的替代化合物。本项目的主要目标是：(1)测量空气、湿沉降、干沉降、地表水和源区下风选定地点植物中TFA的环境浓度，并将其与大气中前体化合物的浓度联系起来；(2)在控制暴露条件下，确定高平面TFA的吸收和效应，以及TFA对季节性湿地代表性微生物的影响。此外，TFA发生和分布的实验数据将与哈佛大学进行的建模工作进行比较。加州和内华达州的季节性湿地将被确定，这些湿地可能特别容易受到TFA随着时间的推移而累积的影响。环境采样将包括近处的下风地点和内华达山脉和大盆地的更偏远的地点。将使用PI最近开发的GC/MS技术分析TFA的甲酯。将对选定的湿地和作物品种使用喷雾室和长期水培暴露，控制植物暴露于已知数量的TFA。将测量气态和雾溶TFA进出植物表面的通量，以及选定作物和湿地植物物种对TFA的根吸收和排放，以确定TFA的生物浓度和毒性效应。在微生物研究中，将从湿地环境中收集的土壤添加不同浓度的TFA，并通过测量微生物呼吸来监测对微生物群落的影响。

9708504 Seiber This proposal was submitted to the Environmental Geochemistry and Biogeochemistry (EGB) solicitation NSF 96-152. The project described below is being jointly supported by the Divisions of Atmospheric Sciences and Earth Sciences. This project addresses the environmental occurrence of trifluoroacetic acid (TFA) and its effects in biota. TFA is a product of the atmospheric degradation of certain hydrochlorofluorocarbons and hydrofluorocarbons, which are replacement compounds for chlorofluorocarbons. The primary objectives of this project are: (1) To measure environmental concentrations of TFA in air, wet deposition, dry deposition, surface waters and plants at selected sites downwind from source regions, and to relate them to atmospheric concentrations of the precursor compounds; (2) To determine the uptake and effects of TFA in higher plans and the effects of TFA on microbes representative of seasonal wetlands under controlled exposure conditions. In addition, the experimental data on TFA occurrence and distribution will be compared with modeling efforts carried out at Harvard University. Seasonal wetlands in California and Nevada will be identified which might be particularly susceptible to effects of TFA from buildup over time. Environmental sampling will include both proximate downwind sites and more remote sites in the Sierra Nevada and Great Basin. TFA will be analyzed as its methyl ester using GC/MS, a technique recently developed by the PI. Controlled exposures of plants to known amounts of TFA will be conducted using misting chambers and long-term hydroponic exposures for selected wetland and crop species. The flux of gaseous and fog-dissolved TFA to and from plant surfaces, and the root uptake and emission of TFA from selected crop and wetland plant species will be measured to determine bioconcentration and toxic effects of TFA. For the microbial study, soils collected from wetland environments will be amended with TFA at several concentrations and the effect on microbial communities monitored by measuring microbial respiration.