Volatile organic compounds (VOCs) and nitrogen oxides (NO_x) play a key role in tropospheric chemistry. A typical urban scenario, under VOC-controlled conditions (low VOC/NO_x 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 NO_x 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.

挥发性有机化合物（VOC）和氮氧化物（NO _x）在对流层化学中起关键作用。在VOC控制的条件下（VOC / NO _x低的典型城市情景）比率），重点讨论了导致巴西市区臭氧浓度高的动力学条件。作为基础案例，在Irajá地区（巴西里约热内卢）评估了单个VOC的动力学和机械反应性，该地区接受了来自工业区的空气质量。芳香族化合物占总质量的41.1％。在MIR，MOIR和EBIR量表中，它们是反应性最高的物质，分别占总动力学反应性的48.8％和机械反应性的71.0、61.0和55.9％。结果表明，较高的臭氧浓度是由多种条件共同导致的，主要是NO _x相对较低含量和相对较高的活性VOC混合物，主要来自工业领域。对于MIR，MOIR和EBIR标度，样品的平均臭氧形成潜能分别计算为3.57、1.39和0.74。