No abstract

No abstract

In urban environments, vehicle emissions are the main source of hydrocarbons (HC) which contribute to formation of tropospheric ozone. Since individual HC exhibit a wide range of ozone formation reactivity, speciated analyzes are necessary to assess the overall impact of vehicle exhaust emissions. Flex-fuel represents more than 90% of the light duty vehicle sales in Brazil. In this project, sampling and analytical methods were implemented and optimized for determination of speciated HC (C 4 -C 12 ). Three flex-fuel vehicles (PROCONVE L4, L5 and L6) were tested, with both gasoline (E22) and ethanol (E100). Vehicle exhaust samples were obtained during emissions testing with FTP75 drive cycle (according to ABNT/NBR 6601) for each of the three phases: cold start, stabilized and hot start. The exhaust was collected in Tedlar bags and transferred to electropolished stainless steel canisters. HC were analyzed using thermal desorption and gas chromatography with a mass spectrometry detector. The analytical procedure was based on Method TO-15 (US EPA). Quantification was performed using a standard reference mixture that covered the entire concentration range of the samples. Using gasoline, E22, experimental emission values for phase 1 were 0.037, 0.017 and 0.019 g HC (C 4 -C 12 ) km -1 for PROCONVE L4, L5 and L6 vehicles, respectively. Average MIR values (specific reactivity) for exhaust phase 1 were 3.04, 3.03 and 2.27, respectively, for PROCONVE L4, L5 and L6 vehicles. Weighted Maximum Incremental Reactivity (MIR) and Ozone Formation Potential (OFP) values, for C 4 -C 12 fraction, were approximately in the intervals 2.00-2.76 and 0.013-0.099, respectively. Aromatic organic compounds in the exhaust of ethanol tests were < 1 ppmC for all phases and vehicles. Results suggest that these compounds are not due to the combustion of ethanol and their contribution for total HC (C 4 -C 12 ) reactivity was considered negligible. A new method will be implemented in future tests to determine the low HC fraction (C 2 and C 3 ) by chromatography. Speciated HC emission data may be useful for technical discussions about the ozone formation potential using Brazilian fuels.

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 CO 2 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.

Meassurements of pollutants concentrations in tunnels can reflect the actual characteristics of mobile sources in order to provide a control strategy to reduce emissions and secondary pollutants formation. Concentration levels of CO, NOx, SO2 and PM10 (particulate matter less than 10 m in diameter) were recorded inside Rebouças Tunnel, in a continuous monitoring station installed at about 1,500 m from the entrance. The reported data are the hourly average values through the year of 2002, bracketed only for the weekdays, weekends excluded. In terms of typical day cycles, the highest concentration levels occur close to traffic peaks and the criteria pollutants show good overall correlation levels with CO, as expected, given their common combustion-bound origin. CO hourly averages ranged from 10 to 50 ppm and the average CO/NO ratio (on a ppm basis) was 0.011, in good agreement with preliminary data for other locations in Brazil. NO concentration levels ranged from less than 1 ppm to about 4 ppm and this form is by far the dominant for nitrogen oxides (NOx) found in the tunnel, accounting for more than 90% of the sum of NO plus NO2. Sulfur oxides (measured as SO2 ) and inhalable particles concentrations ranged from 55 to 140 ppb and about 60 to 250 µg m-3 , respectively, for the composite annual profiles.