A method for the analysis of ultra-trace levels of semi-volatile and non-volatile organic compounds in snow and application to a Greenland snow pit

A method was developed to quantify a suite of organic compounds from snow melt water samples present at trace level concentrations, using a dichloromethane liquid–liquid extraction and GC–MS. Samples from a 3-m snow pit sampled in 2005 from Summit, Greenland were analyzed using the method developed, and a profile of organics over the past ∼4 years was compiled. Supporting data including the concentrations of total organic carbon (TOC), low molecular weight acids, and trace elements were determined using well established methods. The results show that low molecular weight acids contribute a significant percentage, up to 20%, of the measured TOC. Hopanes were measured quantitatively for the first time in Greenland snow. Hopanes, as well as PAHs, are at very low concentrations and contribute 0.0002–0.004% to TOC. Alkanes and alkanoic acids were also quantified, and contribute less than 1% and up to 7%, respectively to TOC. No apparent seasonal pattern was found for specific classes of organic compounds in the snow pit. The lack of seasonal pattern may be due to post-depositional processing.