Primary Emission Ratios Obtained From the Monitoring of Criteria Pollutants in Rebouças Tunnel, Rio De Janeiro, Brazil.

Abstract

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.