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Five-stage size-segregated ambient aerosol particles were collected during January 2003 until October 2004 at one urban and one suburban site of Beijing to investigate the seasonal size distributions of aliphatic and polycyclic aromatic hydrocarbons. The concentrations of total n-alkanes ranging from C11 to C35 varied between 2.1 and 2446 ngm3, with higher values at the urban site than suburban site. A seasonal fluctuation was clearly evident, with higher concentrations occurring during the colder period. The carbon preference index (CPI) of the n-alkanes displayed the highest values in the spring and apparently decreased in winter. Furthermore, smaller size airborne particle-bound n-alkanes tend to have lower CPI values. In addition, the presence of pristane, phytane, n-alkylcyclohexanes, hopanes, and steranes, together with the major unresolved complex mixture (UCM) of branched and cyclic compounds, confirmed the contribution from fossil fuel use in ambient aerosol particles of Beijing. The concentrations of 18 unsubstituted PAHs (18-PAH) varied from 0.84883 ngm3, with the content at the urban site 1.16.6 times higher than those for the suburban site. The seasonal variation of 18-PAH concentrations was as follows winter > autumn > spring > summer. About 6788 of the PAHs were associated with particles having an aerodynamic diameter 2.0 m. PAHs concentration diagnostic ratios reflect that the major source of fine particles is from fossil fuel utilization. [ABSTRACT FROM AUTHOR]

Investigations of natural and engineered environmental systems require achieving a complete characterization and identification of contaminants of concern. However, the differentiation of lipid molecular markers (MMs) that originated from various sources is difficult when based simply on their chemical compositions. A comprehensive fractionation protocol of lipid MMs is thus needed for discriminating contamination sources using chemometric (i.e., mathematical and statistical) techniques. The lack of information about the environmental quality of the coastal environment of Alexandria (Egypt) and the impact of anthropogenic sources of pollution in the area have initiated research to study the different extractable lipid classes and MMs in both natural and engineered environmental systems. Samples representing the complexity of the analyzed Alexandria environment were analyzed qualitatively and quantitatively for their lipid classes. A chemometric approach for the interpretation of the lipid data is presented. This unique approach consists of analysis of variance (ANOVA), discriminant partial least squares (D-PLS), and regularized discriminant analysis (RDA). ANOVA was used to compare the relative magnitudes of sample site and type variances. A variable selection approach based on the PLS regression coefficients was proposed to identify the most important lipid classes with their MMs for the classification, and to improve the results. RDA used a regularized covariance matrix estimate for the conventional statistical discriminant analysis methods. The results in this analysis indicated that: (a) the D-PLS and RDA methods provide satisfactory classification of lipid classes, with RDA being slightly better, and (b) the variable selection strategy was able to improve the classification results, and to help identify the most important lipid classes and contaminant MMs for distinguishing and characterizing the environmental samples. [ABSTRACT FROM AUTHOR]

Residential wood combustion is an important contributor to ambient fine particle levels in the United States. About one-half to two-thirds of the residential wood combustion in the United States occurs in wood stoves as opposed to fireplaces. Thus, any differences between these two sources must be accounted for in chemical mass balance receptor models which attempt to determine the contribution of wood smoke sources to ambient fine particle samples. To fully characterize the fine particle emissions from wood stoves and compare the emissions profiles to those determined from previous fireplace experiments, a series of source tests were conducted on the burning of the most prevalent U.S. tree species in wood stoves. The catalyst-equipped wood stove chosen for these tests was operated under both noncatalytic and catalytic conditions to assess the effects of the catalyst on fine particle emissions. Analysis of the wood smoke includes fine particle mass emission factors, organic and elemental carbon content, ionic and elemental composition, and detailed organic speciation by GC/MS. Between 60 and 90% of the fine particle mass emissions were attributed to measured chemical species. The fine particle emissions from wood stoves show the same general patterns as those from the fireplace combustion of the same tree species; important differences between hardwood and softwood combustion are seen among the substituted phenols and diterpenoids, and levoglucosan is the most abundant individual organic compound emitted. However, fine particle mass emission factors from wood stoves are significantly lower than those from fireplaces. The elemental carbon content of the fine particle mass is generally higher in wood stove smoke than in fire- place smoke, and is even higher when the catalyst was employed. Furthermore, a greater fraction of the organic compounds is identifiable by GC/MS methods in the wood stove smoke vs. the fireplace smoke. These results suggest that differences in the source profiles between wood stove and fireplace combustion merit consideration in source apportionment calculations using organic compounds as tracers. [ABSTRACT FROM AUTHOR]