Establishment of N2O simulation in the Yodo River estuary

N₂O concentration in the air is relatively low, but the greenhouse effect of N₂O is higher than that of the carbon dioxide for the long term. N₂O emission per area from the coastal sea surface is high. Although N₂O concentration in the sea is changed by the biochemical and physical process, amount of those processes is not clarified. To clarify the amount of N₂O flux of each process is necessary to estimate the flux of N₂O between the air and sea in high precision. Therefore we established the numerical model for N₂O based on the observational data in the Yodo River estuary in Osaka Bay, Japan. Observation was carried out in the Yodo river estuary from June 29th to July 14th, 2004. The biochemical process and physical process related to N₂O are formulized in the numerical model. We considered nitrification as the biochemical process. It is influenced by bacterial activity and promoted by increase of water temperature. N₂O is produces by nitrification as the intermediate product in the aerobic environment. Advection, diffusion and the exchange between the sea and air are included in the model as the physical processes. And physical parameters are calculated by the water and salt budget. Tendency of the variation of calculated N₂O concentration is corresponding to the observed one mostly. And the correlation coefficient is 0.79. Therefore we consider that the calculation result is reasonable and can used to discuss the variation mechanism of N₂O concentration in the sea surface layer and the N₂O exchange volume between the air and sea in Yodo River estuary.