| Summary: | Air-snow exchange fluxes of ozone(O3) and NOx (NO+NO2) were measured at Summit, Greenland, to capture effects of changing insulation, snowpack properties. The study site included a buried laboratory facility, snow-sampling manifold, and a meteorological tower installed in the clean air sector ∼650 m southwest of the main camp structures. A multi-inlet snow sampling manifold (‘snow tower’) for measuring trace gases at multiple depths in interstitial air was constructed for use in this study. Pairs of sampling inlets were located on each cross arm on the tower; cross arms were rotated orthogonally to the arms above and below. Flow rates were 1.2–2.5 L per min and were split between the inlet pairs, producing effective flow rates of 0.6–1.25 L per min through each inlet. Sample inlets were fitted with 25 mm Acrodisc® hydrophobic polytetrafluoroethylene (PTFE) syringe filters (Pall Life Sciences, Ann Arbor, Michigan, USA). Inlet pairs were connected via a Teflon perfluoroalkoxy (PFA) union tee to a 30 m × 0.64 cm OD (0.40 cm ID) Teflon PFA sampling line. Measurements include O3, gaseous elemental mercury (GEM), and NOx levels and gradients both within and above the snowpack and eddy-correlation O3 fluxes at two heights above the snowpack; ancillary measurements characterized atmospheric turbulence, actinic flux, micrometeorological parameters and the snowpack's physical and radiative properties.
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