Size-Segregated Atmospheric Particle Mass Concentration in Urban Areas in Luxembourg

This study examines the dependencies between emission sources, meteorological conditions, and particle mass concentration on different temporal and spatial scales. Particulate matter (PM)10, PM2.5, and PM1 were measured in an urban area in Southwest Luxembourg during two field campaigns carried out between 2008 and 2010. Data sampling at various suburban and urban sites accounts for different emission sources and human exposure to particle pollution. Long-range transport and regional source characteristics dominate PM1 mass concentrations resulting in high Pearson correlation coefficients (0.77–0.96) and low coefficients of divergence (0.12–0.18) between measurement stations. In comparison, the coarse particle fractions PM10−PM2.5 and PM2.5−PM1 show higher spatial gradients between stations, which are mainly governed by local sources with lower Pearson correlation coefficients (0.39–0.70) and higher coefficients of divergence (0.21–0.61). The PM10−PM2.5 particle fraction is largely influenced by road transport characteristics reproducing weekday and daily cycles. PM10 mass concentration during winter is dominated by the finer particle fractions, due to domestic heating, whereas concentrations during spring and summer are mostly coarse particles, originating from pollen and windblown dust. Particle mass concentrations of different size fractions were sensitive to dispersion. Unstable atmospheric boundary conditions during the day caused a shift of the PM2.5 /PM10 and PM1/PM2.5 ratios to smaller values in comparison to neutral boundary conditions. A comparison between large-scale clean air and pollution episodes showed differences in the daily cycle of PM10−PM2.5 resulting from local emission sources, transport, and removal.