| Römpp, A; Klemm, O; Frank, H: Haloacetates in Fog, , 64-64 (1999) | |
| Abstract: Atmospheric haloactetates originate from direct anthropogenic and natural emissions, and from atmospheric degradation of halogenated hydrocarbons. Haloacetates are highly soluble in water, and fog may contribute significantly to their wet deposition. However, only little information is available about fogwater concentrations of haloacetates under various meterological conditions. Monofluoroacetate (MFA), difluoroacetate (DFA), trifluoroacetate (TFA), monochloroacetate (MCA), dichloroactetate (DCA), trichloroacetate (TCA), monobromoacetate (MBA), and dibromoacetate (DBA) were measured in fogwater. The fogwater samples for this study were collected at the ecological research site "Waldstein" in the Fichtelgebirge (NE Bavaria). Samples were collected from July through October, 1998, and from December 1998 through March 1999, using active cloudwater collectors. Overall, about 100 samples were collected. TFA is used as an example to illustrate the behavior of haloactetes in fog water. TFA results from the atmospheric degradation of hydrofluorocarbons (HFC) such as HFC-134a, which currently is the single most important CFC substitute. TFA is able to accumulate in plants and may be phytotoxic. The highest concentrations (up to 1350 ng TFA / L) were found in August and September. During winter, maximum concentrations were about 400 ng TFA / L. Haloacetate concentrations show a strong dependence on wind direction: Fog events that were associated with westerly winds showed higher levels of TFA. This phenomenon is particularly interesting as most other trace substances in fog water (e.g. sulfate) show higher concentrations during easterly winds at this research site. Two fog collectors with different collection efficiencies for small droplets were used to obtain the fogwater samples. A comparison of these collectors indicates that smaller droplets (D < 10 µm ) contain higher concentrations of TFA than larger ones. |
