Determination of CO2, CH4 and N2 O: A case study for the city of rio de janeiro using a new sampling method

Abstract

A new sampling method using polypropylene syringes and chemical analysis by gas chromatography was proposed and applied to determine CO2 , CH4 and N2 O. The samples' stability was evaluated and compared with the stability of the samples in stainless steel canisters and Tedlar® bags. This methodology was applied to a case study in the urban area of the city of Rio de Janeiro, Brazil. In 2012, annual averages of 507.6 ± 13.2 μmol mol-1 for CO2 , 1.95 ± 0.06 μmol mol-1 for CH4 and 325.3 ± 3.4 nmol mol-1 for N2 O were obtained. The results for CO2 and CH4 showed peak values in the warmer months and lower values in winter. This CO2 behavior is the opposite of that observed in studies performed in many other cities around the world and may be climate-related. CH4 and N2 O inputs are probably due to the evaporation of liquid and solid waste both from landfill sites located within the city boundaries and from polluted rivers and canals. Additionally, other anthropogenic sources may be considered, such as the release of CH4 by the gas fuel network of the urban area and the emissions due to the use of compressed natural gas by light vehicles.