Real-world emission factors of carbonyl compounds measured in a Rio de Janeiro tunnel, Brazil

Real-world vehicle emissions of carbonyls compounds (CC) were determined at the Rebouças Tunnel, Rio de Janeiro (Brazil). The tunnel is a two-bore tunnel with three lanes in each direction and has a length of 2840 m, divided in two sections. On average, approximately 5,000 vehicles (95% light duty) were passing the tunnel per hour. Sixteen samples were simultaneously collected 500 and 1500 m inside from the entrance. The main CC were formaldehyde, acetaldehyde, acetone, propionaldehyde and benzaldehyde. A total of 16 samples were collected in each point in 8 different days. In 5 days, CO and CO2 were also monitored during the sampling period. Emission factors were calculated. Using the Pierson method, emission factors were 7.5 ± 2.6 and 13.8 ± 5.7 mg km-1 for formaldehyde and acetaldehyde, respectively. Using the fuel consumption method, values were 6.3 ± 2.1 and 11.8 ± 3.9 mg km-1 for the same compounds. The differences between both methods were lower than 20% and may be considered acceptable considering all the approximations in the calculations. Ozone forming potentials (OFP) were also estimated as 90.4 ± 37.3 and 70.7 ± 24.6 mg km-1 for formaldehyde and acetaldehyde, respectively.

本数据集针对巴西里约热内卢雷博萨斯隧道（Rebouças Tunnel）内实际道路车辆的羰基化合物（carbonyls compounds, CC）排放开展测定。该隧道为双孔结构，每个通行方向设置三条车道，全长2840米，分为两个区段。隧道平均每小时通行车辆约5000台，其中95%为轻型车辆。在隧道入口内侧500米及1500米两个点位同步采集样品，每个采样点位在8个不同采样日内累计采集16组样品。本次检测的主要羰基化合物包括甲醛、乙醛、丙酮、丙醛及苯甲醛。其中5个采样日内，采样期间同步监测了一氧化碳（CO）及二氧化碳（CO2）浓度。研究人员计算了车辆排放因子：采用皮尔逊（Pierson）法计算得到，甲醛与乙醛的排放因子分别为7.5±2.6 mg·km⁻¹和13.8±5.7 mg·km⁻¹；采用燃油消耗法计算得到的同类化合物排放因子分别为6.3±2.1 mg·km⁻¹和11.8±3.9 mg·km⁻¹。两种方法的计算结果差异小于20%，结合计算过程中引入的各项近似假设，该差异处于可接受范围。此外，研究人员还估算了甲醛与乙醛的臭氧生成潜势（Ozone forming potentials, OFP），分别为90.4±37.3 mg·km⁻¹和70.7±24.6 mg·km⁻¹。