Sorption behavior of formaldehyde to ice grains

Abstract

The equilibritun partitioning of fonnaldehyde between air and snow was studied in a senes of laboratory experitnents conducted at -S"C, -15"C and -35()C, with the intention of developing a quantitative relationship of the ternperature dependence of the bulk partitioning transfer coefficient, K0 , for fonnaldehyde in polar snow. The results of the experitnents it1dicate that the original field based paratneterization of the n1odel does use realistic values for both the partitioning coefficient, K0 , and the pseudo-fust order transfer rate coefficient, k1 ,. Measurements of K0 were 1.75, 1.97, and 2.39 (Log 1nol L-1 atm-) for -5°C, -15oC and -35()C, respectively. Estitnates of k1 , for the satne three tetnperatures in units of s-1 were 4.11 x 10-4, 1.07 x 10-4, and 1.08 x 1 o s, respectively. Attnospheric tneasuretnents of fonnaldehyde in polar regions reveal concentrations that are higher than predicted frotn current 1nodelll1g. Additionally, firn and firn-air concentrations of fonnaldehyde i11 the polar snow pack have been observed to have a unique profile of preserved concentrations that are not consistent with other reversibly deposited species. These experitnents help to further define the behavior of fonnaldehyde sorption to ice, and the preservation of it in the snow. It has been shown that fonnaldehyde observations it1 fun can be 1nodeled solely through the use of a parameterized tnodel of tetnperature dependent sorption