Wolfgang F. Rogge

Source apportionment of airborne particulate matter using organic compounds as tracers

A chemical mass balance receptor model based on organic compounds has been developed that relates sours; contributions to airborne fine particle mass concentrations. Source contributions to the concentrations of specific organic compounds are revealed as well. The model is applied to four air quality monitoring sites in southern California using atmospheric organic compound concentration data and source test data collected specifically for the purpose of testing this model. The contributions of up to nine primary particle source types can be separately identified in ambient samples based on this method, and approximately 85% of the organic fine aerosol is assigned to primary sources on an annual average basis. The model provides information on source contributions to fine mass concentrations, fine organic aerosol concentrations and individual organic compound concentrations. The largest primary source contributors to fine particle mass concentrations in Los Angeles are found to include diesel engine exhaust, paved road dust, gasoline-powered vehicle exhaust, plus emissions from food cooking and wood smoke, with smaller contribution:; from tire dust, plant fragments, natural gas combustion aerosol, and cigarette smoke. Once these primary aerosol source contributions are added to the secondary sulfates, nitrates and organics present, virtually all of the annual average fine particle mass at Los Angeles area monitoring sites can be assigned to its source.

Levoglucosan, a tracer for cellulose in biomass burning and atmospheric particles

Abstract The major organic components of smoke particles from biomass burning are monosaccharide derivatives from the breakdown of cellulose, accompanied by generally lesser amounts of straight-chain, aliphatic and oxygenated compounds and terpenoids from vegetation waxes, resins/gums, and other biopolymers. Levoglucosan and the related degradation products from cellulose can be utilized as specific and general indicator compounds for the presence of emissions from biomass burning in samples of atmospheric fine particulate matter. This enables the potential tracking of such emissions on a global basis. There are other compounds (e.g. amyrones, friedelin, dehydroabietic acid, and thermal derivatives from terpenoids and from lignin—syringaldehyde, vanillin, syringic acid, vanillic acid), which are additional key indicators in smoke from burning of biomass specific to the type of biomass fuel. The monosaccharide derivatives (e.g. levoglucosan) are proposed as specific indicators for cellulose in biomass burning emissions. Levoglucosan is emitted at such high concentrations that it can be detected at considerable distances from the original combustion source.

Quantification of urban organic aerosols at a molecular level : identification, abundance and seasonal variation

Organic aerosol samples collected systematically throughout a complete annual cycle at four urban sites in southern California are examined by high-resolution gas chromatography and gas chromatography/mass spectrometry. More than 80 organic compounds are quantified and their seasonal ambient concentration patterns are discussed. Primary organic aerosol constituents are readily identified, revealing an annual pattern, with high winter and low summer concentrations. In contrast, aliphatic dicarboxylic acids of possible secondary origin show a reverse pattern, with high concentrations in late spring/early summer. Concentration patterns similar to the secondary dicarboxylic acids also are found for aromatic polycarboxylic acids, certain lower molecular weight n-alkanoic acids, a nonanal and other compounds. Molecular markers characteristic of woodsmoke are identified, and their concentrations change by season in close agreement with prior estimates of the seasonal use of wood as a fuel. This data set can be used to evaluate the predictions of mathematical models for the atmospheric transport and reaction of organic aerosol constituents defined at a molecular level.

Sources of Fine Organic Aerosol. 6. Cigarette Smoke in the Urban Atmosphere

Molecular marker compounds that can be used to trace cigarette smoke particles in the outdoor urban atmosphere are identified. While the most abundant resolved organic compounds present are nitrogen-containing heterocyclics (e.g., nicotine), other potential tracers that will be more stable in the outdoor urban atmosphere also are found. Iso- and anteisoalkanes (C_(29)-C_(34)) are enriched in cigarette smoke particles and show a concentration pattern characteristic of tobacco leaf surface waxes that is distinctly different from leaf surface abrasion products shed from plant leaves that grow in the Los Angeles area. Relative to major leaf surface wax n-alkanes, these iso- and anteisoalkanes are enriched by a factor of more than 40 in tobacco and tobacco smoke particles as compared to leaf surface waxes from Los Angeles area plants. It is found that the iso- and anteisoalkanes concentration pattern generated by cigarette smoke is preserved in the urban atmosphere and is measured at levels that are comparable to emissions estimates based on daily cigarette consumption. Using these marker compounds, ambient fine cigarette smoke particles are estimated to be present at a concentration of 0.28-0.36 µg m^(-3) in the Los Angeles outdoor air, accounting for 1.0-1.3% of the fine particle mass concentration.

Mathematical modeling of atmospheric fine particle‐associated primary organic compound concentrations

An atmospheric transport model has been used to explore the relationship between source emissions and ambient air quality for individual particle phase organic compounds present in primary aerosol source emissions. An inventory of fine particulate organic compound emissions was assembled for the Los Angeles area in the year 1982. Sources characterized included noncatalyst- and catalyst-equipped autos, diesel trucks, paved road dust, tire wear, brake lining dust, meat cooking operations, industrial oil-fired boilers, roofing tar pots, natural gas combustion in residential homes, cigarette smoke, fireplaces burning oak and pine wood, and plant leaf abrasion products. These primary fine particle source emissions were supplied to a computer-based model that simulates atmospheric transport, dispersion, and dry deposition based on the time series of hourly wind observations and mixing depths. Monthly average fine particle organic compound concentrations that would prevail if the primary organic aerosol were transported without chemical reaction were computed for more than 100 organic compounds within an 80 km × 80 km modeling area centered over Los Angeles. The monthly average compound concentrations predicted by the transport model were compared to atmospheric measurements made at monitoring sites within the study area during 1982. The predicted seasonal variation and absolute values of the concentrations of the more stable compounds are found to be in reasonable agreement with the ambient observations. While model predictions for the higher molecular weight polycyclic aromatic hydrocarbons (PAH) are in agreement with ambient observations, lower molecular weight PAH show much higher predicted than measured atmospheric concentrations in the particle phase, indicating atmospheric decay by chemical reactions or evaporation from the particle phase. The atmospheric concentrations of dicarboxylic acids and aromatic polycarboxylic acids greatly exceed the contributions that are due to direct emissions from primary sources, confirming that these compounds are principally formed by atmospheric chemical reactions.

Contribution of primary aerosol emissions from vegetation‐derived sources to fine particle concentrations in Los Angeles

Field measurements of the n-alkanes present in fine atmospheric aerosols show a predominance of odd carbon numbered higher molecular weight homologues (C_(27)–C_(33)) that is characteristic of plant waxes. Utilizing a local leaf wax n-alkane profile in conjunction with an air quality model, it is estimated that, at most, 0.2–1.0 μg m^(−3) of the airborne fine particulate matter (d_p < 2.1 μm) present in the Los Angeles basin could originate from urban vegetative detritus; this corresponds to approximately 1–3% of the total ambient fine aerosol burden. However, some of the observed vegetation aerosol fingerprint in the Los Angeles air may be due in part to emissions from food cooking rather than plant detritus. Seasonal trends in the ambient n-alkane patterns are examined to seek further insight into the relative importance of anthropogenic versus natural sources of vegetation-derived fine particulate matter.

Major Source Categories for PM2.5 in Pittsburgh using PMF and UNMIX

An objective of the Pittsburgh Air Quality Study was to determine the major sources of PM2.5 in the Pittsburgh region. Daily 24-hour averaged filter-based data were collected for 13 months, starting in July 2001, including sulfate and nitrate data from IC analysis, trace element data from ICP-MS analysis, and organic and elemental carbon from the thermal optical transmittance (TOT) method and the NIOSH thermal evolution protocol. These data were used in two source-receptor models, Unmix and PMF. Unmix, which is limited to a maximum number of seven factors, resolved six source factors, including crustal material, a regional transport factor, secondary nitrate, an iron, zinc and manganese factor, specialty steel production and processing, and cadmium. PMF, which has no limit to the number of factors, apportioned the PM2.5 mass into ten factors, including crustal material, secondary sulfate, primary OC and EC, secondary nitrate, an iron, zinc and manganese factor, specialty steel production and processing, cadmium, selenium, lead, and a gallium-rich factor. The Unmix and PMF common factors agree reasonably well, both in composition and contributions to PM2.5. To further identify and apportion the sources of PM2.5, specific OC compounds that are known markers of some sources were added to the PMF analysis. The results were similar to the original solution, except that the primary OC and EC factor split into two factors. One factor was associated with vehicles as identified by the hopanes, PAHs, and other OC compounds. The other factor had strong correlations with the OC and EC ambient data as well as wood smoke markers such as levoglucosan, syringols, and resin acids.