Grantee Research Project Results
2004 Progress Report: Conduct Research and Monitoring That Contributes to a Better Understanding of the Measurement, Sources, Size Distribution, Chemical Composition, Physical State, Spatial and Temporal Variability, and Health Effects of Suspended PM in the Los Angeles Basin (LAB)
EPA Grant Number: R827352C017Subproject: this is subproject number 017 , established and managed by the Center Director under grant R827352
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Southern California Children's Environmental Health Center
Center Director: McConnell, Rob Scot
Title: Conduct Research and Monitoring That Contributes to a Better Understanding of the Measurement, Sources, Size Distribution, Chemical Composition, Physical State, Spatial and Temporal Variability, and Health Effects of Suspended PM in the Los Angeles Basin (LAB)
Investigators: Sioutas, Constantinos , Hinds, William C. , Nel, Andre E. , Cho, Arthur K. , Froines, John R. , Miguel, Antonio
Institution: University of Southern California , University of California - Los Angeles
EPA Project Officer: Chung, Serena
Project Period: June 1, 1999 through May 31, 2005 (Extended to May 31, 2006)
Project Period Covered by this Report: June 1, 2003 through May 31, 2004
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air
Objective:
The overall objective of this project is to conduct research and monitoring that contributes to a better understanding of the measurement, sources, size distribution, chemical composition, physical state, spatial and temporal variability, and health effects of suspended particulate matter (PM) in the Los Angeles Basin (LAB). Intensive aerosol measurements, well beyond the traditional PM2.5 mass, sulfate and nitrate concentrations, were conducted in several areas of the Los Angeles Basin. These included particle number concentrations, size distributions, and detailed PM chemical composition as a function of particle size. Sampling locations were chosen to provide wide geographical and seasonal coverage, including urban “source” sites and downwind “receptor” sites. Intensive PM measurements were also conducted up and downwind of several freeways of the LAB, to characterize near-roadway exposure environments and to support several in vivo and in vitro health studies.
Progress Summary:
PM Characterization
- PM size and chemical composition in the Los Angeles Basin depends on locations and season. Ultrafine particle concentrations (particle diameter dp < 0.1 μm) were found to be the highest at the source sites resulting from fresh vehicular emissions. Mass concentrations in the accumulation mode (0.1 < dp < 2.5 μm) were lower in winter than in summer, especially at the receptor sites. PM concentrations in the coarse mode (2.5 < dp <10 μm) were lower in winter and were composed mostly of nitrate and crustal elements (iron, calcium, potassium, silicon, and aluminum). Consistent relative levels of these elements indicate a common source of soil and/or road dust. In the accumulation mode, nitrate and organic carbon were predominant with higher nitrate levels found at the receptor sites. The ultrafine mode PM consisted of mostly organic carbon, with higher wintertime levels at the source sites due to increased organic vapor condensation from vehicles at lower temperatures. Conversely, higher ultrafine organic carbon levels at the receptor areas are due to secondary organic aerosol formation by photochemical reactions as well as increased advection of polluted air masses from upwind. (Sardar, et al., 2005)
- Similarly, the size distribution of ultrafine particles in source sites was generally unimodal with a mode diameter of 30–40 nm and without significant monthly variations. The number-based particle size distributions obtained in receptor sites were bimodal, with a significant increase in accumulation mode as the season progressed from winter to summer. Afternoon periods in the warmer months are characterized by high number counts while mass and EC remain low, suggesting the formation of new particles by photochemistry. Particle mode diameters range from 30 nm up to above 100 nm, a result not seen in most other studies of particle size distributions in other urban or rural areas where mode diameters are generally less than 50 nm. Evidence is presented that the observed ultrafine particle concentrations and size distributions are influenced by long range advection and photochemical processes as well as vehicular emissions, which have been previously assumed to dominate day to day ultrafine particle levels. (Fine, et al., 2004)
- Although previous research does suggest a relationship between coarse mode and intermodal (1-2.5 μm) PM, the sites in which these studies were conducted are not representative of all locations. Similar data for coarse, intermodal, and fine PM were collected across four sites in the Los Angeles Basin. While some similarities exist between these results and those of comparable studies, our Supersite studies showed that intermodal PM consists of a significant portion of particles that are similar in chemical composition to PM1 particles that are thought to cause the greatest health effects. This study was performed to shed light on the origin and chemical composition of intermodal particles between the coarse and fine PM modes in Los Angeles, a unique city where crustal, oceanic, anthropogenic primary, and secondary sources are responsible for the high observed PM levels. Our results indicate that a PM1 standard would not constitute an unambiguous separation of coarse and fine mode PM in this urban air shed. (Geller, et al., 2004)
- The effects of atmospheric transport on the size distribution of PAHs, EC, OC, SO4-2, and NO3- are also reported, in receptor sites of the LAB. From October to February, the size distributions of PAHs are similar, but different from March to July, with increasing temperature and atmospheric transport. A significant fraction of the PAH and the NO3- mass moved towards the coarse mode, as compared with the previous period. The correlation of temperature with the concentration of all PAHs in the less volatile or particle-phase group (BAA-IND) was negative, consistent with increased partitioning from the vapor-phase with decreasing temperature. During all seasons, the form and shape of the EC size distributions did not vary much and are distinguished by prominent mass in the ultrafine and accumulation modes. For the individual modes of the major species measured, the highest correlations were found in the ultrafine mode for sulfate and EC, suggesting increased atmospheric transport of vehicular emissions from the urban downtown Los Angeles region. (Miguel, et al., 2004)
- Ambient measurements of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs were carried out in source and receptor sites. Atmospheric concentrations of PAHs and nitro-PAHs are of interest because both of these compound classes include potent mutagens and carcinogens. To augment our current understanding of atmospheric formation of nitro-PAHs, four sampling periods were employed to study the diurnal variations of these compounds. The PAH concentrations were highest in Los Angeles during winter, as a result of traffic input at this source site under tight wintertime atmospheric inversions. In contrast, nitro-PAH levels were highest in Riverside during summer, as a result of enhanced summertime photochemistry. Hydroxyl radical-initiated reactions produced nitro-PAHs in both seasons, while in winter little evidence for nitrate radical chemistry was seen. For the summer samples, nitrate radical-initiated formation of nitro-PAHs is suggested by nitro-PAH isomer profiles not only at the downwind location as anticipated, but also at the source site. In southern California, the contribution of atmospheric formation through gas-phase radical-initiated PAH reactions to the ambient burden of nitro-PAHs is dominant, with the semi-volatile nitro-PAHs being the most abundant and 2-nitrofluoranthene being the major particle-associated nitro-PAH. (Reisen, et al., 2003)
- In a separate study we explored the size-fractionated ultrafine (10-180 nm) chemical composition at urban source sites (USC and Long Beach) and inland receptor sites (Riverside and Upland) in the Los Angeles basin over three different seasons. Size-fractionated ultrafine particles were collected by a NanoMOUDI over a period of 2 weeks at each site. The chemical composition of ultrafine particles ranged from 32 to 69% for organic carbon (OC), 1-34% for elemental carbon (EC), 0-24% for sulfate, and 0-4% for nitrate. A distinct OC mode was observed between 18 and 56 nm in the summer, likely due to photochemical secondary organic aerosol formation. The EC levels are higher in winter at the source sites due to lower inversion heights and are higher in summer at the receptor sites due to increased long-range transport from upwind source areas. Nitrate and sulfate were measurable only in the larger particle size ranges of ultrafine PM. Collocated continuous measurements of particle size distributions and gaseous pollutants helped to differentiate ultrafine particle sources at each site. We showed that in addition to primary emissions, photochemical reactions in the atmosphere can form new particles via nucleation. (Sardar, et al., 2004)
- Individual organic compounds can be used as tracers for primary sources of ambient particulate matter in chemical mass balance receptor models. By examining the seasonal, temporal, geographical, size-fractionation, and inter-correlations of individual organic compounds, the sources and atmospheric fate of these tracers can be better understood and their utility as molecular markers can be assessed. We have used a high-flow rate, low pressure-drop ultrafine particle separator to collect sufficient mass for organic speciation of ultrafine and accumulation mode aerosol on a diurnal basis. Sampling was conducted at two sites (source and receptor) over two seasons (summer and winter). Hopanes, used as organic markers for vehicular emissions were found to exist primarily in the ultrafine mode. Levoglucosan, an indicator of wood combustion, was quantified in both size ranges but more was present in the accumulation mode particles. An indicator of photochemical secondary organic aerosol formation, 1,2-benzenedicarboxylic acids, was found primarily in the accumulation mode and varied with site, season and time of day as one would expect for a photochemical product. These data will be used to assess the concentration of specific PM sources to personal exposure and ultimately health effects in upcoming epidemiological and toxicological studies in LAB. (Fine, et al., 2004b)
- As part of our evaluation of sampling artifacts from continuous and time integrated methods for PM measurement, we conducted a study to obtain insights into the dynamics of volatilization from the heated TEOM filter. The primary hypothesis that tested was that the rate of ammonium nitric acid and ammonia gas volatilization from particle-bound ammonium nitrate that is loaded on the TEOM’s fiber filter occurs over time scales that are longer than the five-minute cycle time for the system. This is important to the use of the Differential TEOM, which utilizes the vaporization measured during alternate five-minute periods as a reference baseline value for its particle mass measurements. Our experiments showed that under ambient conditions, the mass lost from the Differential TEOM tracks well the ambient particulate nitrate concentration. The saturation ratio for nitrate vapor immediately downstream of the filter ranged from 0.05 to 0.2. By comparison, for laboratory collection of ammonium nitrate aerosol the vaporization reached a maximum value corresponding to a saturation of nitrate vapor downstream of the heated filter. This difference is due to the relatively higher particle concentrations used for the laboratory experiments. For the ambient measurements the particulate nitrate concentrations were consistently lower than the equilibrium vapor concentration at the TEOM filter temperature. In both cases the nitrate vaporization is driven by the temperature of the TEOM filter and independent of the pressure drop across the filter. (Hering, et al., 2004)
Support of Health Effects and Exposure Research
- In collaboration with CARB, we developed a mobile platform designed to characterize UFP and associated pollutants inside vehicles, during commute in Los Angeles freeways and residential streets. Average concentrations of UFP and related pollutants varied strongly by location, road type, and truck traffic volumes, suggesting a relationship between these concentrations and truck traffic density. Freeway concentrations were frequently an order of magnitude higher than on residential streets for UFP, NOx, BC, and CO, with higher NOx and BC values observed in diesel traffic freeways than those with mostly light duty vehicle traffic. (Westerdahl, et al., 2005)
- We examined volatility of penetrating ultrafine outdoor particles, predominantly from freeway emissions, into indoor environments where other particle sources were minimized and no cooking activities took place, using a. tandem differential mobility analyzer (TDMA) system. Our findings suggest that outdoor particles are more volatile than indoor aerosols. Increasing temperature from ambient to 130°C decreased and broadened indoor and outdoor aerosol mode diameters, however greater mode decreases were observed for outdoor particles. Furthermore, outdoor particles lost more of their volume upon heating than indoor aerosols. No significant particle losses due to volatilization were observed at 60°C for either indoor or outdoor aerosols. Heated outdoor particles with diameters greater than 45 nm showed bi-modal distributions, indicating that some of the aerosol is composed of primarily non-volatile particles, whereas the remaining particles are composed of mainly volatile material and consequently shrink. Evaluation of outdoor particle volatility as a function of distance to the freeway revealed that aerosol volatility decreases with increasing distance from the source. (Kuhn, et al., 2005)
- Physical and chemical characteristics, including volatility of PM in the proximity of a Light-Duty Vehicle (LDV) freeway were also measured and analyzed. The ultrafine number concentrations next to the freeway were 46000 cm-3 on average during the sampling period. The MOUDI ultrafine mass concentration, nitrate, and EC were higher next to the freeway than at the background site, farther from the freeway. The other components analyzed in the ultrafine mode had similar concentrations next to the freeway and at the background site. Volatility ranged from about 65% volume losses of 120 nm particles heated to 110°C, to 95% of 20 nm particles. The 20 nm aerosol was only internally mixed, whereas increasing non-volatile fractions were found for 40 nm (6% next to the freeway), 80 nm (20%), and 120 nm (28%) aerosols. (Kuhn, et al., 2005b)
- Our freeway PM measurements were compared to those performed in two bores of the Caldecott Tunnel in Northern California. One bore (Bore 1) is open to both heavy-and light-duty vehicles (HDV-LDV) while heavy-duty vehicles are prohibited from entering the second bore (Bore 2). A strong association between particle number and normalized vehicle speed (R2 = 0.69) was observed in bore 1 of the tunnel. Heavy-duty diesel vehicles showed higher particle number emissions than light-duty vehicles. The PM10 mass emission factor for heavy-duty vehicles was 14.5 times higher than that of light-duty vehicles. The particles derived from diesel are more abundant in elemental carbon, 70.9% of PM10 emissions, as compared to the light-duty vehicles with a lower EC fraction of 40.5%. Conversely, a greater percentage of OC was found in light-duty emissions than heavy-duty emissions. Compared to previous studies at the Caldecott tunnel, less particle mass but more particle numbers (by factors of 2-4 fold) are emitted by vehicles than was the case 7 years ago. As the emissions of carbonaceous PM of newer engines decreases, the formation of nucleation mode particles is favored due to the reduction of the available surface for adsorption of the semi-volatile material. The resulting supersaturation of the mostly organic vapor increases the production of nano-particles by nucleation. (Geller, et al., 2005)
- Ultrafine particles, which dominate the particle number concentration of ambient aerosols, recently have been the focus of several health studies. It has been hypothesized traditionally that these particles originate from vehicular emissions; thus, the concentrations of gases such as CO, NO, or NO2 that also originate from traffic sources can be used as a surrogate measures of ultrafine PM. The advantage of this approach is that concentrations of these gases are monitored routinely in compliance networks and on personal levels by means of relatively simple and easy-to use monitors. The validity of the assumption using gases as surrogates of ultrafine PM was tested in this study in five sites of the Los Angeles Basin over the course of one calendar year. Our studies indicated overall lack of significant associations between hourly and 24-hr PN versus gaseous co-pollutant concentrations, which can be attributed to the differences in the sources and formation mechanisms that are responsible for generating these pollutants in the environment of the Los Angeles Basin. These findings also imply that potential confounding effects of co-pollutants will not affect epidemiologic analysis seeking to link ultrafine particles to health effects because of the general lack of associations between PN and co-pollutant concentrations. (Sardar, et al., 2004b)
References:
Fine PM, Shen S, Sioutas C. Inferring the sources of fine and ultrafine particulate matter at downwind receptor sites in the Los Angeles Basin using multiple continuous measurements. Aerosol Science & Technology 2004;38(S1):182-195.
Fine PM, Chakrabarti B, Krudysz K, Schauer J, Sioutas C. Diurnal variations of individual organic compound constituents of ultrafine and accumulation mode particulate matter in the Los Angeles Basin. Environmental Science & Technology 2004b;38:1296-1304.
Geller MD, Fine P, Sioutas C. The relationship between real-time and time-integrated fine and coarse particle concentrations at an urban site in Los Angeles. Journal of the Air & Waste Management Association 2004;54:1029-1039.
Geller MD, Sardar S, Fine PM, Sioutas C. Measurements of particle number and mass concentrations in a roadway tunnel environment. Environmental Science & Technology 2005;39(29):8653-63.
Hering S, Fine P, Sioutas C, Jaques P, Ambs J, Hogrefe O, Demerjian K. Field assessment of the dynamics of particulate nitrate vaporization using differential TEOM and automated nitrate monitors. Atmospheric Environment 2004;38(31):5183-5192.
Kuhn T, Krudysz M, Zhu Y, Fine PM, Hinds WC, Froines JF, Sioutas C. Volatility of indoor and outdoor ultrafine particulate matter near a freeway. Journal of Aerosol Science 2005;36(3):291-302.
Kuhn T, Biswas S, Fine PM, Geller M, Sioutas C. Physical and chemical characteristics and volatility of PM in the proximity of a light-duty vehicle freeway. Journal of Aerosol Science 2005b;39(4):347-357.
Miguel AH, Eiguren-Fernandez A, Jaques P, Froines JR, Grant B, Mayo P, Sioutas C. Seasonal variation of the particle size distribution of polycylic aromatic hydrocarbons and of major aerosol species in Claremont California. Atmospheric Environment 2004;38:3241-3251.
Reisen F, Wheeler S, Arey J. Methyl- and dimethyl-/ethyl-nitronaphthalenes measured in ambient air in Southern California. Atmospheric Environment 2003;37:3653-3657.
Reisen F, Arey J. Atmospheric reactions influence seasonal PAH and nitro-PAH concentrations in the Los Angeles basin. Environmental Science & Technology 2005;39(1):64-73.
Sardar SB, Fine PM, Yoon H, Sioutas C. Associations between particle number and gaseous co-pollutant concentrations in the Los Angeles Basin. Journal of the Air and Waste Management Association 2004;54(8):992-1005.
Sardar SB, Fine PM, Jaques PA, Sioutas C. Seasonal and spatial variability of the size-resolved chemical composition of PM10 in the Los Angeles Basin. Journal of Geophysical Research 2005;110:D07S08.
Sardar SB, Fine PM, Mayo PR, Sioutas C. Size fractionated chemical speciation measurements of ultrafine particles in Los Angeles using the NanoMOUDI. Environmental Science & Technology 2005b;39:932-944.
Westerdahl D, Fruin S, Sax T, Fine PM, Sioutas C. Mobile platform measurements of ultrafine particles and associated pollutant concentrations on freeways and residential streets in Los Angeles. Atmospheric Environment 2005;39(20):3597-3610.
Supplemental Keywords:
RFA, Health, Scientific Discipline, Air, particulate matter, Environmental Chemistry, Air Pollutants, Risk Assessments, Biochemistry, Atmospheric Sciences, particulates, ambient aerosol, toxicology, human health effects, ambient measurement methods, air pollution, particulate exposure, human exposure, toxicity, aerosol composition, allergens, particle concentrator, airborne urban contaminants, human health risk, aerosols, atmospheric chemistry, particle transportRelevant Websites:
http://www.scpcs.ucla.edu Exit
Progress and Final Reports:
Original AbstractMain Center Abstract and Reports:
R827352 Southern California Children's Environmental Health Center Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R827352C001 The Chemical Toxicology of Particulate Matter
R827352C002 Pro-inflammatory and the Pro-oxidative Effects of Diesel Exhaust Particulate in Vivo and in Vitro
R827352C003 Measurement of the “Effective” Surface Area of Ultrafine and Accumulation Mode PM (Pilot Project)
R827352C004 Effect of Exposure to Freeways with Heavy Diesel Traffic and Gasoline Traffic on Asthma Mouse Model
R827352C005 Effects of Exposure to Fine and Ultrafine Concentrated Ambient Particles near a Heavily Trafficked Freeway in Geriatric Rats (Pilot Project)
R827352C006 Relationship Between Ultrafine Particle Size Distribution and Distance From Highways
R827352C007 Exposure to Vehicular Pollutants and Respiratory Health
R827352C008 Traffic Density and Human Reproductive Health
R827352C009 The Role of Quinones, Aldehydes, Polycyclic Aromatic Hydrocarbons, and other Atmospheric Transformation Products on Chronic Health Effects in Children
R827352C010 Novel Method for Measurement of Acrolein in Aerosols
R827352C011 Off-Line Sampling of Exhaled Nitric Oxide in Respiratory Health Surveys
R827352C012 Controlled Human Exposure Studies with Concentrated PM
R827352C013 Particle Size Distributions of Polycyclic Aromatic Hydrocarbons in the LAB
R827352C014 Physical and Chemical Characteristics of PM in the LAB (Source Receptor Study)
R827352C015 Exposure Assessment and Airshed Modeling Applications in Support of SCPC and CHS Projects
R827352C016 Particle Dosimetry
R827352C017 Conduct Research and Monitoring That Contributes to a Better Understanding of the Measurement, Sources, Size Distribution, Chemical Composition, Physical State, Spatial and Temporal Variability, and Health Effects of Suspended PM in the Los Angeles Basin (LAB)
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.