No abstract

This study reports for the first time a time series analysis of daily urban air pollutant levels (CO, NO, NO2, O3, PM10, and SO2) in Beirut, Lebanon. The study examines data obtained between September 2005 and July 2006, and their descriptive analysis shows long-term variations of daily levels of air pollution concentrations. Strong persistence of these daily levels is identified in the time series using an autocorrelation function, except for SO2. Time series of standardized residual values (SRVs) are also calculated to compare fluctuations of the time series with different levels. Time series plots of the SRVs indicate that NO and NO2 had similar temporal fluctuations. However, NO2 and O3 had opposite temporal fluctuations, attributable to weather conditions and the accumulation of vehicular emissions. The effects of both desert dust storms and airborne particulate matter resulting from the Lebanon War in July 2006 are also discernible in the SRV plots.

Atmospheric concentrations of PM2.5 and PM10 were measured in Beirut, Lebanon, for a period of 12 months. The daily average concentrations of PM10 and PM2.5 were found to be 51.3 ± 33.1 and 30.3 ± 9.4 µg.m −3 , respectively, with corresponding maximum values of 359.7 and 208.6 µg.m −3. The annual average concentrations of PM10 and PM2.5 exceeded the World Health Organization's standards by 150% and 200%, respectively. The mean concentration of coarse particles (PM10-2.5) was found to be 41% of the average PM10, suggesting that the site was also influenced by re-suspended surface dust and soil. The mean PM2.5/PM10 ratio for the entire study period was 0.61 ± 0.12. This indicates that in Beirut, PM2.5 accounts for about 61% of PM10. Such a large fraction of fine particles could have considerable effect on health; thus, it is necessary to quantify its impact. Daily concentrations of PM10 and PM2.5 exceeded the upper threshold limit on 133 and 129 days, respectively, representing 39% and 38% of the entire sample, respectively. These findings indicate the important role dust events play within this area. Concentrations of PM2.5 were highly correlated with NO2, whereas concentrations of PM10 and PM10-2.5 were not associated with any gaseous pollutant. Regression analysis showed that 93% of PM2.5 and 43% of PM10 particle mass concentrations were derived from road traffic exhaust in Beirut.

No abstract

No abstract