Seasonal variability of Nitrous Oxide (N2O) in Rwanda

Abstract

N2O is the third most important greenhouse gas after carbon dioxide (CO2) and methane (CH4). It contributes to global warming and ozone layer depletion though not given too much attention compared to CO2 and CH4. It is necessary to assess the variability of N2O in Rwanda in order to get its status and how N2O concentration varies with seasons. N2O data were measured using the mid infrared analyzer, also known as Picaro G5105. The data used have been recorded from Rwanda Climate observatory, Mugogo station during the year 2017, starting from January up to December. Up on analysis of N2O data, it has been found that the concentration of Nitrous oxide increased during the year 2017. The N2O concentration passed from the 329.79 ppb during the January to February season to 330.15 ppb during the October to December season. The mean annual concentration for Nitrous oxide was 329.5 ppb. That mean value of N2O concentration shows that the concentration of N2O continues to increase, because the N2O concentration previously reported ranged from 320 to 324 ppb in the atmosphere. The seasonal variation of N2O showed that the March-April-May (MAM) season had the lowest mean concentration of 329.08 ppb .The sharp decrease is probably due to lack of coupling between the soil temperature and rainfall received by the soil. The next lowest seasonal concentration of N2O was found during the June-July-August-September (JJAS) season. JJAS season’s con centration was 329.30 ppb. Though the concentration was still below the one found during the January-February (JF) season, it had increased compared to MAM season. The reason behind that increase may have been the addition of nitrogen fertilizers and manure to soil, because it was a growing season. But also because N2O is a long lived species, the contribution from remote locations may be taken into account. The highest seasonal concentration is found in the October-November-December (OND) season with a value of 330.15 ppb. The reason is the rainfall received, and temperature which is higher compared to the one experienced during the MAM season. The seasonal patterns of the N2O for Rwanda and Australia exhibit almost the same behaviour. The correlation coefficient between Nitrous oxide concentration and temperature, and humidity as well, yielded the values of 0.1085 and -0.1325 respectively for temperature and for humidity.The values suggested that the correlation is negative with RH and positive with T although it is still not significant and is therefore weak. For better elucidation of the seasonal dependence of N2O concentration variation, data for more than one year should be used for future research.The use of inventories estimation shall help in quantifying the N2O emissions by sectors and non-incountry emissions.