Characterization of Particulate-Phase High Molecular Weight Mono-Carbonyls (C# > 5) and Dicarbonyls in Urban Atmosphere of Xi'an, China

An analytical method to quantify particulate-phase high molecular weight mono-carbonyls (C# &gt; 5) and di-carbonyls has been developed by adopting 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by high performance liquid chromatography/ultra-violet (HPLC/UV) detection. Satisfactory reproducibility and precision of the measurements were achieved. This method was applied to measure the carbonyls in PM2.5 collected on quartz-fiber filters, sampled in Xi&#39;an, China, from 2008 to 2009. Nonanaldehyde was the most abundant compound, followed by octanaldehyde, hexanaldehyde and heptaldehyde, accounting for 40%, 20%, 12% and 11% in the total quantified carbonyls. For dicarbonyls, the concentration of methylglyoxal was much higher than that of glyoxal. The seasonal variations of the particulate-phase mono-carbonyls and dicarbonyls were similar to those in the gas-phase, namely winter &gt; autumn &gt; spring &gt; summer (except octanaldehyde). A strong correlation among those carbonyls was observed in winter, resulting from low temperature partitioning, weaker photochemical reaction, and more primary emission sources. In contrast, in summer, vehicle emissions, cooking emissions and photochemical reactions are the major pollution source in Xi&#39;an.</p

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

Hazardous airborne carbonyls emissions in industrial workplaces in China

A pilot hazardous airborne carbonyls study was carried out in Hong Kong and the Mainland of China. Workplace air samples in 14 factories of various types of manufacturing and industrial operations were collected and analyzed for a panel of 21 carbonyl compounds. The factories can be classified into five general categories, including food processing, electroplating, textile dyeing, chemical manufacturer, and petroleum refinery. Formaldehyde was invariably the most abundant carbonyl compound among all the workplace air samples, accounting for 22.0-44.0% of the total measured amount of carbonyls on a molar basis. Acetone was also found to be an abundant carbonyl in workplace settings; among the selected industrial sectors, chemical manufacturers&#39; workplaces had the highest percentage (an average of 42.6%) of acetone in the total amount of carbonyls measured in air. Benzaldehyde accounted for an average of 20.5% of the total amount of detected carbonyls in electroplating factories, but its contribution was minor in other industrial workplaces. Long-chain aliphatic carbonyls (C-6-C-10) accounted for a large portion (37.2%) of the total carbonyls in food-processing factories. Glyoxal and methylglyoxal existed at variable levels in the selected workplaces, ranging from 0.2% to 5.5%. The mixing ratio of formaldehyde ranged from 8.6 to 101.2 ppbv in the sampled workplaces. The observed amount of formaldehyde in two paint and wax manufacturers and food-processing factories exceeded the World Health Organization (WHO) air quality guideline of 81.8 ppbv. Carcinogenic risks of chronic exposure to formaldehyde and acetaldehyde by the workers were evaluated. The lifetime cancer hazard risks associated with formaldehyde exposure to male and female workers ranged from 2.01x10(-5) to 2.37x10(-4) and 2.68x10(-5) to 3.16x10(-4), respectively. Such elevated risk values suggest that the negative health impact of formaldehyde exposure represents a valid concern, and proper actions should be taken to protect workers from such risks. Implications: Many carbonyl species (e.g., formaldehyde, acetaldehyde, and acrolein) are air toxins and they pose public health risks. The scope of this investigation covers 21 types of carbonyls based on samples collected from 14 different workplaces. Findings of the study will not only provide a comprehensive assessment of indoor air quality with regard to workers&#39; healthy and safety, but also establish a theoretical foundation for future formulation of intervention strategies to reduce occupational carbonyl exposures. No similar study has been carried out either in Hong Kong or the Mainland of China.</p