Impacts of aerosol compositions on visibility impairment in Xi'an, China

Daily particle light scattering coefficient, PM2.5 mass and chemical composition were measured in Xi&#39;an from February to December 2009. Visibility was strongly affected by anthropogenic air pollution sources, resulting in an average visual range (VR) of 6.4 &plusmn; 4.5 km. The threshold PM2.5 mass concentration, corresponding to VR &lt;10 km, was &sim;88 &mu;g m&minus;3. The revised IMPROVE equation was applied to estimate chemical extinction (bext), which on average was &sim;15% lower than measured bext. PM2.5 ammonium sulfate was the largest contributor, accounting for &sim;40% of bext, followed by organic matter (&sim;24%), ammonium nitrate (&sim;23%), and elemental carbon (&sim;9%), with minor contributions from soil dust (&sim;3%), and NO2 (&sim;1%). High secondary inorganic aerosol contributions (i.e., SO42&minus; and NO3&minus;) were the main contributors for VR &lt;5 km. A Positive Matrix Factorization (PMF) solution to the Chemical Mass Balance (CMB) receptor model showed that coal combustion was the dominant factor, accounting for &sim;52% of the dry particle light scattering coefficient, followed by the engine exhaust factor (&sim;31%). Other factors included biomass burning (&sim;12%) and fugitive dust (&sim;5%).</p

Chemical Composition of Indoor and Outdoor Atmospheric Particles at Emperor Qin's Terra-cotta Museum, Xi'an, China

Indoor particles and microclimate were measured in summer (August 2004) and winter (January 2005) periods inside and outside Emperor Qin&#39;s Terra-Cotta Museum in Xi&#39;an, China. Indoor temperature ranged from 21.9 degrees C to 32.4 degrees C in summer and from 0 degrees C to 5.3 degrees C in winter. Relative humidity varied from 56% to 80% in summer and from 48% to 78% in winter. The number concentrations of particles were lower (0.3-1.0 mu m) in summer, and were higher (1.0-7.0 mu m) in winter. The average indoor PM(2.5) and TSP concentrations were 108.4 +/- 30.3 mu g/m(3) and 172.4 +/- 46.5 mu g/m(3) in summer and were 242.3 +/- 189.0 mu g/m(3) and 312.5 +/- 112.8 mu g/m(3) in winter, respectively. Sulfate, organic matter, and geological material dominated indoor PM(2.5), followed by ammonium, nitrate, and elemental carbon. Several milligram of sulfate particles can deposited in the museum per square meter each year based on the dry deposition estimate. High concentrations of acidic particles suspended inside the museum and their depositions have high risk for the erosion of the terra-cotta figures.</p

Characterization and seasonal variations oflevoglucosan in fine particulate matter in Xi’an, China

PM2.5 (particulate matter with an aerodynamic diameter &lt;2.5 mm) samples (n &frac14; 58) collected every sixth day in Xi&rsquo;an, China, from 5 July 2008 to 27 June 2009 are analyzed for levoglucosan (1,6-anhydro-b-D-glucopyranose) to evaluate the impacts of biomass combustion on ambient concentrations. Twenty-four-hour levoglucosan concentrations displayed clear summer minima and winter maxima that ranged from 46 to 1889 ng m 3, with an average of 428 399 ng m 3. Besides agricultural burning, biomass/biofuel combustion for household heating with straws and branches appears to be of regional importance during the heating season in northwestern China. Good correlations (0.70 &lt; R &lt; 0.91) were found between levoglucosan relative to watersoluble K&thorn;, Cl , organic carbon (OC), elemental carbon (EC), and glyoxal. The highest levoglucosan/OC ratio of 2.3% was found in winter, followed by autumn (1.5%). Biomass burning contributed to 5.1&ndash;43.8% of OC (with an average of 17.6 8.4%).</p

Characteristics of fine particulate non-polar organic compounds in Guangzhou during the 16th Asian Games: Effectiveness of air pollution controls

The concentrations of organic compounds, including n-alkanes and polycyclic aromatic hydrocarbons (PAHs), in fine particles (PM2.5) were measured in an urban area of Guangzhou before, during, and after the 16th Asian Games (9-30 November 2010). Higher average concentrations of n-alkanes and PAHs occurred in the nighttime, presumably due to a restriction on motor vehicle operation during the day and the accumulation of pollutants due to temperature inversions at night. The carbon preference index, contributions of wax n-alkanes, and PAHs diagnostic ratios indicated that the main sources of n-alkanes and PAHs were anthropogenic, especially motor vehicle emissions. The CMAQ model was used to estimate the percentages of biogenic organic aerosol in the total organic aerosol, then the ratios of source marker PAHs to biogenic organic carbon were used to evaluate the air pollution control policies effectiveness during the Asian Games.</p