Particulate air pollution in transport micro-environments
To understand the dynamics of particulate matter inside train coaches and public cars, an investigation was carried out during 2004–2006. For air-conditioned rail coaches, during peak journey times, the mean concentrations of PM10, PM2.5 and PM1 were 44 µg m−3, 14 µg m−3 and 12 µg m−3, respectively. The levels fell by more than half (21 µg m−3, 6 µg m−3, and 4 µg m−3) for the same size fractions, on the same route, during the off-peak journeys. On the other hand, in non-air-conditioned coaches, the PM10 concentrations of up to 95 µg m−3 were observed during both peak and off-peak journeys. However the concentrations of PM2.5 and PM1 were 30 µg m−3 and 12 µg m−3 in peak journeys in comparison to 14 µg m−3 and 6 µg m−3 during off-peak journeys. Over a period of four months the concentrations of PM10, PM2.5 and PM1 in car journeys were generally similar during both morning and evening journeys with average values of 21 µg m−3 for PM10, 9 µg m−3 for PM2.5 and 6 µg m−3 for PM1. However during October the average concentration of PM10 was 31 µg m−3. An analysis of nearby fixed monitoring sites for both PM10 and PM2.5 revealed an episode of high particulate pollution over southern England during one week of October. There was no statistically significant difference between particulate matter levels for morning and evening car journeys. A statistically significant correlation was found between morning and evening PM10 (0.45), PM2.5 (0.39) and PM1 (0.46). In train journeys, a statistically significant difference was observed for peak and off-peak levels of PM10, PM2.5 and PM1 in air-conditioned coaches. On the other hand, in non air-conditioned coaches a significant difference was documented only for PM2.5 and PM1.