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N2O is one of the most important greenhouse gases and ozone depletor, which was a matter of more and more concerned. The Southern Ocean was considered as one of the most important N2O source and was believed to account for ~1/4 of oceanic budget. However, there is uncertainty about this budget due to limited data availability. In this study, field and lab works were conducted for better understanding of N2O dynamics during sea ice melting and sea ice formation. In the field study, taking advantage of the Chinese Antarctic cruise, a 10 days’ time series study was carried out at a station in the Prydz Bay, Antarctica, where, surface water N2O was observed continuously, and the adjacent ice cores were taken for N2O analysis. In the lab, an ice growing simulation system was constructed to study the N2O dynamics during the sea ice formation. The result of endmember mixing models and calculation of N2O partition in three phases during sea ice formation provide important information about the dynamics of N2O during ice melting and sea ice formation processes, that is, the sea ice melting regulated N2O concentration and saturation status, which can be an explanation for reported N2O undersaturation observed in polar oceans, whereas during the sea ice formation, most of the N2O will be expelled to the deeper water while a small amount of retain the sea ice and less amount of N2O release to the atmosphere.

Nitrous oxide (N2O) is one of the most important greenhouse gases and contributes to the depletion of ozone in the stratosphere. Estuaries are areas of intensive biological production and associated N2O emissions through both denitrification and nitrification processes. The spatial and temporal variations of N2O in the Jiulong River Estuary, a subtropical estuary, were explored to evaluate sources and sinks of N2O in this area. The estuary was found to be a strong source of N2O, its saturation in the surface water ranged from 113 to 2926% relative to the ambient atmospheric concentrations, showing great temporal and spatial variations and was influenced by multiple factors such as the concentration of dissolved inorganic nitrogen (DIN, i.e., NO3−,NH4+, and NO2−), salinity and dissolved oxygen. N2O concentrations were at a high level in upper estuary but reduced to the lower parts of the estuary. Groundwater input could be another contributor to N2O in the estuary. Almost all N2O within the estuary was released into the atmosphere rather than being transported to the bay. The N2O flux in the estuary (mean 597 μmol/m2/d) was at the higher end of the range observed in estuaries worldwide due to the very high DIN loads in the Jiulong River Estuary. Our data indicate that the N2O saturation in the estuary continues to increase, although the DIN inputs began to decline in 2011, which might be relate to the improved environmental conditions with increased oxygen concentrations. N2O production pathways have changed from predominantly denitrification in the past toward significant production from nitrification in the present. Further investigation is needed to better understand the behavior of N2O in the Jiulong River Estuary.