Does Aqueous-Phase Oxidation of HCHO Opens a Pathway to Formic Acids in Atmosphere?

摘要

Formic acid is the major contributor to acid rain in some regions but its sources are not fully understood. We investigated the aqueous-phase reactions of HCHO (aq) and OH radicals at enlarged rainwater pH values (2.49-5.89) in Guiyang, China from May 2006 to April 2007. Our results show that there were no significant correlation between the [HC00H]_t/[HCH0] (aq) and the rainwater pH. The ratio did not appear to vary consistently as a function of rainwater pH as predicted by theoretical model. In addition, we saw no clear evidence that oxidation of HCHO (aq) would produce significant HC00H (aq) which indicates this reaction may be only a minor contribution to the budget of HCOOH (g) in atmosphere. Further investigation is strongly suggested to be carried out in field cloud water, fog water, or rainwater because the ratios would be diverged from equilibrium value as a result of other chemical or physical processes.