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

Özet

Volatile organic compounds (VOCs) and nitrogen oxides (NOx) play a key role in tropospheric chemistry. Atypical urban scenario, under VOC-controlled conditions (low VOC/NOxratios), is discussed with emphasis onthe kinetic conditions leading to high ozone concentrations for an urban area of Brazil. As a base case, kineticand 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% oftotal mass. They were the most reactive species, representing 48.8% of the total kinetic reactivity and 71.0, 61.0and 55.9% of the mechanistic reactivity, in MIR, MOIR and EBIR scales, respectively. Results showed that highozone concentrations are due to a combination of conditions, mainly, relatively low NOxlevels and a relativelyhigh reactive VOC mix, primarily originating from an industrial area. Average ozone forming potential for thesamples were calculated as 3.57, 1.39 and 0.74 for the MIR, MOIR and EBIR scales, respectively.