A reactivity analysis of volatile organic compounds in a Rio de Janeiro urban area impacted by vehicular and industrial emissions

摘要

Volatile organic compounds (VOCs) and nitrogen oxides (NOx) play a key role in tropospheric chemistry. A typical urban scenario, under VOC-controlled conditions (low VOC/NOx ratios), is discussed with emphasis on the kinetic conditions leading to high ozone concentrations for an urban area of Brazil. As a base case, kinetic and mechanistic reactivities of individual VOCs, were evaluated in the district of Irajá (Rio de Janeiro, Brazil), which receives air masses originating from an industrial area. Aromatic compounds contributed with 41.1% of total mass. They were the most reactive species, representing 48.8% of the total kinetic reactivity and 71.0, 61.0 and 55.9% of the mechanistic reactivity, in MIR, MOIR and EBIR scales, respectively. Results showed that high ozone concentrations are due to a combination of conditions, mainly, relatively low NOx levels and a relatively high reactive VOC mix, primarily originating from an industrial area. Average ozone forming potential for the samples were calculated as 3.57, 1.39 and 0.74 for the MIR, MOIR and EBIR scales, respectively.