Soils were collected from the frozen permafrost layer (> 90 cm below the surface) at four sites underlying tussock or wet sedge vegetation, and on three glacial surfaces on the North Slope of Alaska during summer 2015.  Sampling and preparation of the permafrost leachates from soils collected in 2015 are described in Ward et al. (2017).

Duplicate permafrost leachates were prepared from permafrost soils collected at each site, except for Toolik moist acidic tundra, which did not have an experimental replicate.  Each permafrost leachate was exposed to 18 hours of simulated sunlight at 20 °C (Atlas Suntest XLS+) in Whirl-Pak bags (Nasco, Inc.) alongside dark controls.  Dissolved organic carbon in the light-exposed and dark control waters was isolated by solid-phase extraction, freeze-dried, and analyzed by solid-state 13C nuclear magnetic resonance (NMR; Ward and Cory, 2015, 2016).  The percent loss of carboxyl carbon (C) was calculated (Ward and Cory, 2016) and reported as the average ± 1 standard error (SE) of the experimental replicate leachates (n = 2, except for Toolik moist acidic tundra, which did not have an experimental replicate).

References: 

Bowen, J. C., C. P. Ward, G. W. Kling, R. M. Cory..  Arctic amplification of global warming strengthened by sunlight oxidation of permafrost carbon to CO2.    In review.

Ward, C. P., R. M. Cory.  2015.  Chemical composition of dissolved organic matter draining permafrost soils. Geochim. Cosmochim. Acta, 10.1016/j.gca.2015.07.001

Ward, C. P., R. M. Cory.  2016.  Complete and partial photo-oxidation of dissolved organic matter draining permafrost soils. Environ. Sci. Technol., 10.1021/acs.est.5b05354

Ward, C. P., S. G. Nalven, B. C. Crump, G. W. Kling, G. W., R. M. Cory.  2017.  Photochemical alteration of organic carbon draining permafrost soils shifts microbial metabolic pathways and stimulates respiration. Nat. Commun., 10.1038/s41467-017-00759-2