| Carbon emission from human activities, especially from fossil fuels’burning, is the main reason that contributes to the constant soar of CO2 concentration in global atmosphere in recent decades. In the recent years, transportation industry accounts for 14 percent and on a rise among anthropogenic emission sources according to a study. Therefore, this survey targets at four typical trunk roads in Nanjing urban areas according to the road layout and traffic flow, and applied vehicle-mounted L1-840A NDIR CO2/H2O analysis meters to observe CO2 concentration for four season (from the winter of 2013 to the fall of 2014). In addition, the experimental data is employed to analyze the spatial and temporal distribution features of CO2 concentration in trunk roads of Nanjing urban areas as well as their relationship with the impact factors.The main conclusions drawn include:(1) During the observation, the mean CO2 concentration is 494.6±58.1 ppm of the trunk roads in Nanjing urban and winter reaches 502.3±61.6ppm, with fall 502.2±61.8ppm, summer 488.0±55.7ppm and spring 486.0±50.6ppm. Moreover, the overall CO2 concentration distributes mainly between 390-550ppm, with its frequency values exceeding 82.3%. During weekdays, the highest CO2 concentration is witnessed in fall, reaching 514.0±61.5ppm, while summer is the lowest, arriving at 484.3±53.8ppm; During weekends, the maximum CO2 concentration is in summer, at 500.0±59.7ppm, and the minimum CO2 concentration is in spring, at 459.6±36.4ppm.(2) During the observation, traffic CO? concentration mostly centralizes between 390-510ppm during the time periods of 06:00～07:00,11:30～12:30 and 22:00-23:00; while during rush hours (07:30～08:30 and 17:30～188:30), traffic CO2 concentration climbs to approximately 550ppm.(3) As to daily shift of CO? concentration in weekdays all the four seasons witness a bimodal pattern, with two peaks appearing during the time periods of 07:30～08:30 and 17:30～18:30, exactly corresponding to the rush hours in mornings and afternoons. As to daily shift of CO2 concentration in weekends, a bimodal pattern is experienced in winter and fall, but not in spring and summer.(4) The CO2 concentration in the four selected roads mainly distributes between 390-510ppm in spring and winter and 390-550ppm in summer and fall. In terms of the average CO2 concentration both in weekdays and weekends, the auxiliary road of east ranks no.1 in spring and winter while the main trunk road in north-south reaches the highest in summer and fall. At contrast, the auxiliary road of west remains the lowest in four seasons.(5) In any given season, CO2 concentration mainly distributed in 475-550 ppm of the road sections in downtown, and in 400-475 ppm of the road sections in suburb; Mean CO2 concentration is 504.0±62.3 ppm in the road sections in downtown,and is 455.2±26.0 ppm in the road sections in suburb.(6) In the factors affecting the concentration of road CO2 concentration, there is significant positive correlation between actual vehicle number and CO2 concentration; There is significant negative correlation between actual driving speed and CO2 concentration, and the correlation is even more obvious during workdays due to the fact that human traffic habits are more regular during workdays; When the wind parallel to the direction of the road is able to change temporal and spatial variations of CO2 concentrations significantly within a short period. |
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