A54A-01
National Trends in Trace Metals Concentrations in Ambient Particulate Matter
Ambient measurements of trace metals identified as hazardous air pollutants (HAPs, air toxics) collected in the United States from 1990 to 2006 were analyzed for long-term trends. Trace metals analyzed include lead, manganese, arsenic, chromium, nickel, cadmium, and selenium. Visual and statistical analyses were used to identify and quantify temporal variations in air toxics at national and regional levels. Trend periods were required to be at least five years. Lead particles decreased in concentration at most monitoring sites, but trends in other metals were not consistent over time or spatially. In addition, routine ambient monitoring methods had method detection limits (MDLs) too high to adequately measure concentrations for trends analysis. Differences between measurement methods at urban and rural sites also confound trends analyses. Improvements in MDLs, and a better understanding of comparability between networks, are needed to better quantify trends in trace metal concentrations in the future.
A54A-02
Lead in single atmospheric particles
Single particle measurements using PALMS have shown that a significant fraction of accumulation mode particles contain trace amounts of Pb. This talk will explore the reasons for the frequency of Pb in fine particles now that most gasoline is unleaded. Trace amounts of Pb were found in 5 to 25 percent of 250 to 3000 nm diameter particles sampled by both aircraft and surface instruments in the eastern and western United States. Lead was found on all types of particles, including Pb present on biomass burning particles from remote fires. Less common particles with high Pb contents contributed a majority of the total amount of Pb. Single particles with high Pb content often also contained alkali metals, Zn, Cu, Sn, As, and Sb. The association of Pb with Zn and other metals is also found in IMPROVE network filter data from surface sites. Sources of airborne Pb in the United States are reviewed for consistency with these data. The frequent appearance of trace Pb is consistent with widespread emissions of fine Pb particles from combustion sources followed by coagulation with larger particles during long-range transport. Clean regions of the western United States show some transport of Pb from Asia but most Pb over the United States comes from North American sources.
A54A-03
Speciated Elemental and Isotopic Characterization of Atmospheric Aerosols – Recent Advances
Detailed elemental, isotopic, and chemical speciation analysis of aerosol particulate matter (PM) can provide valuable information on PM sources, atmospheric processing, and climate forcing. Certain PM sources may best be resolved using trace metal signatures, and elemental and isotopic fingerprints can supplement and enhance molecular maker analysis of PM for source apportionment modeling. In the search for toxicologically relevant components of PM, health studies are increasingly demanding more comprehensive characterization schemes. It is also clear that total metal analysis is at best a poor surrogate for the bioavailable component, and analytical techniques that address the labile component or specific chemical species are needed. Recent sampling and analytical developments advanced by the project team have facilitated comprehensive characterization of even very small masses of atmospheric PM. Historically; this level of detail was rarely achieved due to limitations in analytical sensitivity and a lack of awareness concerning the potential for contamination. These advances have enabled the coupling of advanced chemical characterization to vital field sampling approaches that typically supply only very limited PM mass; e.g. (1) particle size-resolved sampling; (2) personal sampler collections; and (3) fine temporal scale sampling. The analytical tools that our research group is applying include: (1) sector field (high-resolution-HR) ICP-MS, (2) liquid waveguide long-path spectrophotometry (LWG-LPS), and (3) synchrotron x-ray absorption spectroscopy (sXAS). When coupled with an efficient and validated solubilization method, the HR-ICP-MS can provide quantitative elemental information on over 50 elements in microgram quantities of PM. The high mass resolution and enhanced signal-to-noise of HR-ICP-MS significantly advance data quality and quantity over that possible with traditional quadrupole ICP-MS. The LWG-LPS system enables an assessment of the soluble/labile components of PM, while simultaneously providing critical oxidation state speciation data. Importantly, the LWG- LPS can be deployed in a semi-real-time configuration to probe fine temporal scale variations in atmospheric processing or sources of PM. The sXAS is providing complementary oxidation state speciation of bulk PM. Using examples from our research; we will illustrate the capabilities and applications of these new methods.
A54A-04
Properties and Composition of Size Fractionated Indoor, Outdoor, and Personal Particulate Matter in Retirement Homes of the Los Angeles Basin
Size fractionated indoor, outdoor and personal particulate matter (PM) samples were collected at four retirement communities of the Los Angeles basin between June 2005 and February 2007 by using personal cascade impactor samplers (PCISs). Two different 6-weeks sampling campaigns were conducted at each site and 24-hr coarse, accumulation, and quasi-ultrafine (UF) mode particles were sampled 6 times per week. A total of 60 nonsmoking subjects age 65 and older affected by coronary artery disease (CAD) were monitored during the sampling period. Daily PM fractions were collected co-currently at indoor and outdoor stationary sites. Hourly indoor and outdoor PM2.5, OC, EC, particle number (PN), ozone (O3), carbon monoxide (CO) and nitrogen oxides (NO and NO2) concentrations were also measured at these sites. Primarily results showed that personal levels were better correlated to indoor levels than the outdoor levels, as elderly subjects spent most of their time indoors. Indoor/outdoor correlations were higher for accumulation mode particles than for UF and coarse particles, suggesting that this size fraction penetrates indoors with great efficiency. Chemical speciation analysis are being implemented on weekly composites of size-resolved indoor and outdoor samples. The UF composites are being analyzed for organic species, metals and water soluble organic carbon (WSOC). Reactive oxygen species (ROS) analyses of water extracts from UF samples are also being implemented to investigate the relationships between the ROS and the chemical composition of UF particles, and analyze its indoor and outdoor spatial and seasonal variations. Accumulation mode samples are being analyzed for metals and WSOC, while coarse mode particles are only being analyzed for metals. Factor analysis will be applied on the chemical speciated indoor and outdoor data to identify potential sources of PM in the study area, and to assess the extent of human exposure to indoor and outdoor PM.
A54A-05
The Composition of Organic Aerosols in Southeast Asia During The 2006 Haze Episode
The regional smoke haze in Southeast Asia is a recurring air pollution problem. Uncontrolled forest fires from land-clearing activities in Sumatra and Borneo, and to a lesser extent Malaysia, have occurred almost every dry season since the late 1990s. The smoke haze that took place in October 2006 shrouded an estimated 215,000 square miles of land on Indonesia's islands of Sumatra and Borneo, and persisted for several weeks. Satellite pictures showed numerous hotspots in both Sumatra and Kalimantan. The prevailing, South-Southwesterly, winds blew smoke from land and forest fires in central and south Sumatra to Singapore, affecting the regional air quality significantly and reducing atmospheric visibility. During this haze episode, we carried out an intensive field study in Singapore to characterize the composition of organic aerosols, which usually account for a large fraction of airborne particulate matter (PM). A total of 17 PM samples were collected while the hazy atmospheric conditions persisted in Singapore, and subjected to accelerated solvent extraction with dichloromethane and acetone. The extracted compounds were grouped into three major fractions (n-alkanes, polycyclic aromatic hydrocarbons, and polar organic compounds). More than 180 particulate-bound organic compounds were determined using gas chromatography/mass spectrometry (GC-MS). In order to investigate the origin of organic species, the carbon preference indexes as well as diagnostic ratios were used. The compositional differences of organic aerosols between the haze- and non- haze periods will be presented. The atmospheric implications of the composition of organic aerosols of biomass burning origin will be discussed. Keywords: smoke haze, organic aerosols, n-alkanes, polycyclic aromatic hydrocarbons, polar organic compounds
A54A-06
Tracking Petroleum Refinery Emission Events Using Lanthanum and Lanthanides as Elemental Markers for Fine Particulate Matter
This presentation reports the development and application of an analytical method to quantify the rare earth elements (REEs) in atmospheric particulate matter and emissions of catalyst material from the petroleum refining industry. Inductively coupled plasma – mass spectrometry following high temperature/high pressure microwave digestion has been used to study the REE composition of several fresh and spent catalysts used in fluidized-bed catalytic cracking (FCC) units in petroleum refineries as well as in ambient atmospheric fine particulate matter collected in Houston, TX. The results show that the routine emissions from local FCC units in Houston contribute a constant and low amount to ambient PM2.5 of ~0.1 micrograms per cubic meter. However, a significant (33 – 106 fold) increase in the contributions of FCC emissions to PM2.5 is quantified during an upset emission event compared with background levels associated with routine operation. The impact of emissions from the local refinery that reported the emission event was tracked to a site approximately 50 km downwind from the source, illustrating the potential exposure of humans over a large geographical area through the long-range transport of atmospheric fine particles as well as the power of elemental signatures to understand the sources of fine particles.
A54A-07
Two-Step Single Particle Mass Spectrometry for On-Line Monitoring of Polycyclic Aromatic Hydrocarbons Bound to Ambient Fine Particulate Matter
Polycyclic aromatic hydrocarbons (PAH) are formed as trace products in combustion processes and are emitted to the atmosphere. Larger PAH have low vapour pressure and are predominantly bound to the ambient fine particulate matter (PM). Upon inhalation, PAH show both, chronic human toxicity (i.e. many PAH are potent carcinogens) as well as acute human toxicity (i.e. inflammatory effects due to oxi-dative stress) and are discussed to be relevant for the observed health effect of ambient PM. Therefore a better understanding of the occurrence, dynamics and particle size dependence of particle bound-PAH is of great interest. On-line aerosol mass spectrometry in principle is the method of choice to investigate the size resolved changes in the chemical speciation of particles as well the status of internal vs. external mixing of chemical constituents. However the present available aerosol mass spectrometers (ATOFMS and AMS) do not allow detection of PAH from ambient air PM. In order to allow a single particle based monitoring of PAH from ambient PM a new single particle laser ionisation mass spectrometer was built and applied. The system is based on ATOFMS principle but uses a two- step photo-ionization. A tracked and sized particle firstly is laser desorbed (LD) by a IR-laser pulse (CO2-laser, λ=10.2 μm) and subsequently the released PAH are selectively ionized by an intense UV-laser pulse (ArF excimer, λ=248 nm) in a resonance enhanced multiphoton ionisation process (REMPI). The PAH-ions are detected in a time of flight mass spectrometer (TOFMS). A virtual impactor enrichment unit is used to increase the detection frequency of the ambient particles. With the current inlet system particles from about 400 nm to 10 μm are accessible. Single particle based temporal profiles of PAH containing particles ion (size distribution and PAH speciation) have been recorded in Oberschleissheim, Germany from ambient air. Furthermore profiles of relevant emission sources (e.g. gasoline and diesel engine, wood combustion) and the obtained chemical profiles were compared with the ones from the ambient PAH containing particles.
A54A-08
Lubricating Oil and Fuel Contributions to Particulate Matter Emissions From Light Duty Gasoline and Heavy Duty Diesel Vehicles
Size-resolved particulate matter emissions from heavy duty diesel vehicles (HDDVs) and light duty gasoline vehicles (LDGVs) operated under realistic driving cycles were analyzed for elemental carbon (EC), organic carbon (OC), hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs). Measured hopane and sterane size distributions did not match the total carbon size distribution in most cases, suggesting that lubricating oil was not the dominant source of particulate carbon in the vehicle exhaust. Regression analysis using 17α(H)- 21β(H)-29-norhopane as a tracer for lubricating oil and benzo[ghi]perylene as a tracer for gasoline showed that gasoline fuel and lubricating oil both make significant contributions to particulate EC and OC emissions from LDGVs. A similar regression analysis performed using 17α(H)-21β(H)-29-norhopane as a tracer for lubricating oil and flouranthene as a tracer for diesel fuel was able to explain the size distribution of particulate EC and OC emissions from HDDVs. The size- and composition-resolved analysis showed that EC emitted from all diesel vehicles operated under relatively high load conditions was dominated by diesel fuel contributions with little EC attributed to lubricating oil. Particulate OC emitted from diesel vehicles was more evenly apportioned between fuel and oil contributions. EC emitted from LDGVs operated under fuel-rich conditions was dominated by gasoline fuel contributions. OC emitted from visibly smoking LDGVs was mostly associated with lubricating oil, but OC emitted from all other categories of LDGVs was dominated by gasoline fuel. The results of the current study clearly illustrate that fuel and lubricating oil make separate and distinct contributions to particulate matter emissions from motor vehicles. These particles should be tracked separately during ambient source apportionment studies since the atmospheric evolution and ultimate health effects of these particles may be different. The source profiles for fuel and lubricating oil contributions to EC and OC emissions derived in this study provide a foundation for future ambient source apportionment calculations.