Organic and Black Carbon in PM2.5 at an Urban Site at Dhaka, Bangladesh

摘要

The results from 1-year of measurements of PM2.5, organic carbon (OC) and black carbon (BC) concentrations are presented for an urban traffic-influenced site, the Farm Gate in Dhaka, Bangladesh. The measurements were based on sampling using two Air Metrics simultaneously operating samplers. The concentrations of OC and BC concentrations in PM2.5 varied from 5–96 μg/m3 and 4–48 μg/m3, respectively. The concentrations of PM2.5 varied from 11–328 μg/m3. The annual particulate organic matter (POM) accounted for 46 ± 11% in PM2.5 whereas BC stayed at 33 ± 12%. The effects of meteorological conditions on the variability of OC and BC concentration were examined and the contribution of secondary organic aerosol to the total OC was calculated. The concentrations of OC and BC relative to the total PM2.5 are high and have good correlation with wind speed and temperature. The OC/BC ratio correlated with wind speed, temperature and sulfur concentration. Based on these relationships, it can be concluded that both local and regional sources of OC and BC are important. The local sources are traffic, coal and biomass burning. Distant sources include areas where there is extensive agricultural burning.