Meteorological variables and PM10 exceedances effect on aerosol particles in a low emission zone using compositional data analysis

Particulate air pollution is a significant environmental concern due to its potential effects on the environment and human health. Meteorological variables can affect greatly on PM accumulation, also establishing a possible obstacle to the achievement of air quality standards. The objective of the study is to evaluate the effect of meteorological variables such as temperature, relative humidity and daily precipitation on coarse and fine size fraction of PM with and without considering PM10 exceedances conditions using a multiple compositional linear model. The study was conducted in an environmental traffic site placed in a low emission zone (LEZ) of Milan, which is located in the Po Valley (Northern Italy), during the cold season. The results indicated that an increasing in temperature of about 4.7 °C determined a decrease in fine size fraction of PM of about 6.2 % and 24.1 % with and without exceedances, respectively. Whereas an increase in relative humidity of about 19 % determined an increase in fine size fraction of PM of about 10.5 %. In addition, the analysis showed that the PM10 measured when there were PM10 exceedances was compositionally different from that measured when there were not PM10 exceedances as it was richer in fine particles of about 17.2 %. The study showed that PM10 exceedances were mainly caused by an increase in the fine size fraction of PM rather than the coarse one. Furthermore, research results indicated that changes in temperature and relative humidity could affect the particle size fractions of PM. A decrease in temperature and an increase in relative humidity led to an increase in the PM fine size fraction. The study provides insights into the underlying mechanisms affecting both fine and coarse size PM fractions.