Haloacetates in fog and rain

Atmospheric haloacetates can arise from photochemical degradation of haloge nated hydrocarbons and from direct anthropogenic emissions. Furthermore, th ere is also evidence of natural sources although these are quantitatively u ncertain. As haloacetates are highly soluble in water, hydrometeors are mos t significant for their deposition. Fogwater (96 samples) and rainwater sam ples (over 100 samples) were collected from July 1998 to March 1999 at an e cological research site in northeastern Bavaria, Germany. They were analyze d for monofluoroacetate (MFA), difluoroacetate (DFA), trifluoroacetate (TFA ), monochloroacetate (MCA), dichloroacetate (DCA), trichloroacetate (TCA), monobromoacetate (MBA), and dibromoacetate (DBA). The major inorganic ions were also determined. High concentrations of up to 11 mug/L MCA, 5 mug/L DC A, 2 mug/L TCA, and 2 mug/L TFA were found in fogwater associated with west erly winds. Backward trajectories were calculated to determine the origin o f the air masses. MBA and DBA have highest concentrations in fogwater advec ted with air originating from the Atlantic, suggesting the marine origin of these two compounds. All analyzed substances show higher average concentra tions in fog than in rain. Estimates of the deposition of haloacetates sugg est that the contribution of fog may be more important than rain for the to tal burden of a forest ecosystem.