Practical Methods for Collecting and Pretreating Frozen Wet Deposition Samples for X‐Ray Absorption Spectroscopy

Practical methods for collecting and pretreating fresh snow and rime ice, a type of frozen wet deposition formed when supercooled droplets freeze upon contact with surfaces, for X‐ray absorption fine structure (XAFS) analysis of their insoluble fraction are presented. By elevating the snow sampler to 1 m and the rime ice sampler to 0.7 m above ground level in a region with limited snowfall, contamination from soil particles and fragments of low vegetation was minimized. To collect the insoluble fraction from frozen wet deposition, two filtration procedures were compared: complete melting prior to filtration and gradual melting during filtration. Because the former method may lead to loss of the insoluble fraction, the latter method was found to be more suitable for recovering it. Filters prepared from fresh snow and rime ice samples using the gradual melting method were employed to measure sulfur K‐edge XAFS spectra. This study demonstrates that the dominant oxidation state of sulfur can be identified using filters prepared from 500 g of frozen samples containing a minor amount of insoluble sulfur (0.026–0.132 mg kg −1 ).