Abstract
The atmospheric nitrous oxide (N2O) concentration has been measured at four sites, Urawa, Kumagaya, Mt. Dodaira, and the Center for Environmental Science in Saitama (CESS), in Saitama Prefecture for approximately 20 years since 1991. In this study, we examined the long-term trend and seasonal variation in the N2O concentration, and a comparison with other prefectural areas such as Ryori (Iwate Pref.) and Hateruma (Okinawa Pref.) that are observation sites providing the background levels of our country was performed. As a result, there was not a significant difference in the N2O concentration among the four sites in Saitama. In addition, No difference in the N2O concentration was recognized between those in Saitama and those in Ryori and Hateruma. These results suggest that there is little regional variation in the N2O concentration in our country. The concentration of N2O continues to rise at all the observation sites. The increasing rate in the N2O is approximately 0.66-0.68 ppbv per year and more steady than that in the 1990's. On the other hand, it was observed that the N2O concentration was relatively higher in the winter and shows the tendency to be lower from the summer to autumn. However, the variation in the N2O concentration was relatively small at all the observation sites. In particular, seasonal change of the N2O concentration was low in the background area.
