The retention of TFA in soil by abiotic processes is being assessed in representative soils from 14 LTER sites
The Montreal Protocol on Substances That Deplete the Ozone Layer in 1987 and the subsequent London amendments of 1990 require a complete phaseout of chiorofluorocarbons (CFCs) by the year 2000. In the United States, the 1990 amendments to the Clean Air Act call for similar controls on CFCs. The chemical manufacturing industry will initially use hydrochlorofluorocarbons (HCFCs) as transition materials to replace CFCs, with plans to ultimately shift use to hydrofluorocarbons (HFCs) early in the next century. This shift from fully halogenated to partially halogenated compounds will reduce the lifetime of these materials in the atmosphere and help mitigate the depletion of stratospheric ozone. Hydrofluorocarbons have essentially no ozone depleting potential because they contain no chlorine.
Trifluoroacetate (TFA) is an important breakdown product of the CFC replacement chemicals (HCFCs and HFCs). As CFCs are replaced by HCFCs and HFCs, TFA will be produced in the atmosphere and transported via precipitation to the Earth’s surface. The fate of TFA is uncertain. Preliminary laboratory studies suggested that TFA does not adsorb to soil and that atmospheric deposition of TFA to the terrestrial environment may be conservatively transported within the aqueous phase. However, soil absorption experiments conducted to date have not been comprehensive.
Charles T. Driscoll (Hubbard Brook LTER) and Gene E. Likens (Institute of Ecosystem Studies) have initiated a cross-site investigation to examine the adsorption of TFA in soils from LTER sites. Representative soils have been obtained from 14 LTER sites including Cedar Creek, Coweeta, Harvard Forest, H.J. Andrews, Hubbard Brook, Jornada, Kellogg, Konza, Luquillo, Niwot Ridge, Sevilleta, Arctic Tundra, North Temperate Lakes, and Virginia Coast. Batch adsorption experiments are being conducted to assess the retention of TFA in soil by abiotic processes and to determine the role that various soil characteristics, such as pH and content of Fe and Al oxides, have in regulating TFA adsorption.
Preliminary findings suggest that a Spodosol mineral soil from Hubbard Brook exhibits limited adsorption of added TFA. As a result, atmospheric deposition of TFA would not be readily retained in the site’s soils. In contrast, soils which are acidic and/or contain high concentrations of aluminum and iron oxides, such as Ultisols or Oxisols, may adsorb TFA.
Researchers interested in results or associated with additional sites who would like to participate, may contact Charles Driscoll, 315-443-3434, cDriscoll@LTERnet.edu.