Abstract:

Distributions and saturations of nitrous oxide (N2O) were investigated in the Kongsfjorden and Bayelva River of the Svalbard islands in August 2013 and 2015. The concentrations of dissolved N2O in the surface water of the Kongsfjorden ranged from 10.95 to 13.32 nmol·L–1 with an average of (12.47 ± 0.71) nmol·L–1 in August 2013. In August 2015, the concentrations ranged from 11.40 to 13.07 nmol·L–1 with an average of (12.39 ± 0.53) nmol·L–1. Dissolved N2O concentrations in the surface waters of the Bayelva River ranged from 10.66 to 16.83 nmol·L–1 with an average of (14.65 ± 1.54) nmol·L–1 in August 2013. In August 2015, the concentrations ranged from 9.38 to 15.45 nmol·L–1 with an average of (12.99 ± 1.98) nmol·L–1. The warm and saline Atlantic water flow was thought to be the dominant factor in the N2O distributions in northwestern Kongsfjorden, while the N2O distributions in southeastern Kongsfjorden were mainly regulated by glacier meltwater. Meanwhile, sediment N2O produced through denitrification might be an important contributor to the accumulation of N2O in the Kongsfjorden. Negative correlations were found between the ΔN2O and apparent oxygen utilization (AOU), indicating that biological activities had limited contributions to the N2O production and consumption in the Kongsfjorden. N2O in the glacier meltwater of Ny-Ålesund was undersaturated (78%) in August 2013. N2O saturations in the Bayelva River increased from the upper stream to the estuary because of the water-air exchange and temperature. The N2O undersaturation in the Kongsfjorden was the result of dilution by sea ice meltwater. N2O saturations in the surface waters of the Kongsfjorden ranged from 77% to 98% with an average of (89 ± 6)% in August 2013 and from 90% to 101% with an average of (95 ± 4)% in August 2015. Furthermore, other factors including temperature had an effect on the saturation of N2O in the different water bodies of Ny-Ålesund. Because of the undersaturation of dissolved N2O, the Kongsfjorden and Bayelva River were sinks for atmospheric N2O.

Key words: Arctic, fjord, river, nitrous oxide, production, glacier meltwater