Nitrous oxide emissions from coastal waters in Tokyo Bay

摘要

The distribution, source and atmospheric flux of nitrous oxide (N_2O) in seawater in Tokyo Bay were investigated from May to October 1994 to evaluate this area as an N_2O source to the atmosphere. N_2O was measured from seawater at 23 sampling stations (n = 178). Nitrate (NO_3), nitrinte (NO_2), ammonium (N H_4 - ), oxygen (O_2), water temperature and salinity were also determined. N_2O was supersaturated in all surface seawater, the surface N_2O saturation ranged from 116 to 1630/100. Both the high concentration of surface N_2O in the low salinity region and absence of significant spatial deviation in the distribution of N_2O with season suggested that the main source of N_2O was input of fresh water, discharge of treated sewage waters containing N_2O in the bay area is probably the main source of the observed high concentrations of N_2O in seawater there.