Distributions, sources and atmospheric fluxes of nitrous oxide in Jiaozhou Bay

The distributions, sources and atmospheric fluxes of nitrous oxide (N₂O) in the seawater of Jiaozhou Bay were investigated during four surveys in 2003 to evaluate this area as a source of N₂O to the atmosphere. N₂O concentrations in both the surface and bottom waters of Jiaozhou Bay showed obvious variability with both seasons and tidal cycles. Atmospheric fluxes of N₂O in Jiaozhou Bay showed seasonal and spatial variations, with the highest values occurring in summer and the lowest in winter. The annual emission of N₂O from the bay was estimated to be 1.09 × 10⁶–2.23 × 10⁶ mol yr⁻¹. N₂O in the water column of Jiaozhou Bay was found to come from several external sources including riverine water, sewage water and groundwater input, among which the riverine input was dominant while the groundwater input was rather limited. The spatial variation in distribution and atmospheric fluxes of N₂O in Jiaozhou Bay was influenced by the input of polluted river waters and sewage effluent along the eastern coast, which highlights the effects of human impacts on N₂O emission rates.