Nitrate samples were originally collected as 0.2-1.5 kg snow samples in the field along the CHICTABA traverse, Antarctica. Snow was collected in three methods: snow pits, skin layer, and 1 m depth layer. For snow pits, snow was collected in increments of 3 cm thick layers. Skin layer samples were collected as the loose snow grains 2-6 mm deep on the surface. The 1 m depth layer samples were taken as a 5-10 cm thick layer surrounding 1 m depth, which was then thoroughly mixed. Samples were melted and nitrate concentrated with a ion exchange resin at Concordia Station, Antarctica. Isotopic analysis performed with MAT253 mass spectrometer at IGE, Grenoble, France.