2009 Progress Report: Sources, Composition, Variability and Toxicological Characteristics of Coarse (PM10-2.5) Particles in Southern CaliforniaEPA Grant Number: R833743
Title: Sources, Composition, Variability and Toxicological Characteristics of Coarse (PM10-2.5) Particles in Southern California
Investigators: Sioutas, Constantinos , Cho, Arthur K. , Froines, John R. , Moore, Katharine F. , Nel, Andre E. , Schauer, James J.
Current Investigators: Sioutas, Constantinos , Cho, Arthur K. , Froines, John R. , Moore, Katharine F. , Nel, Andre E. , Schauer, James J.
Institution: University of Southern California , University of California - Los Angeles , University of Wisconsin - Madison
EPA Project Officer: Chung, Serena
Project Period: November 1, 2007 through October 31, 2009 (Extended to October 31, 2012)
Project Period Covered by this Report: November 1, 2008 through October 31,2009
Project Amount: $1,120,641
RFA: Sources, Composition, and Health Effects of Coarse Particulate Matter (2006) RFA Text | Recipients Lists
Research Category: Air , Air Quality and Air Toxics , Particulate Matter
The objective of this study is to provide the much-needed information on the relationships between coarse particulate matter (PM) sources, spatial and seasonal characteristics, and toxicity in Southern California. The multidisciplinary research currently underway combines ambient measurements, exposure assessment and toxicology. The results of this study – the Los Angeles Basin (LAB) Coarse PM Study – will be integrated with other major research efforts currently under way in Southern California, including the EPA-funded Southern California PM Center.
During Year 1, the LAB Coarse PM Study performed the following tasks:
- Designed, assembled, tested and deployed ten outdoor coarse PM samplers to the field to collect the time-integrated filter samples across the Los Angeles Basin. Field sampling campaign commenced in April 2008 (Q2) and the weekly collection of coarse PM samples, each integrated of 24 hours sampling time, continued uninterruptedly till May 2009 (the end of Q2).
- Designed, assembled, tested and deployed two indoor coarse PM samplers to the field to collect the indoor filter samples in two indoor sites associated with their corresponding outdoor sites. Phase I of the indoor sampling started in mid-July 2008 (Q3) and continued successfully for 9 consecutive weeks through early September 2008 (Q4). Collection of a single 24-hour integrated weekly sample was carried out concurrently with the operation of the associated outdoor coarse PM sampler.
- Following factory recalibration and testing at USC, three tapered element oscillating microbalance (TEOM) units modified to measure coarse PM only were deployed to sampling sites in Riverside, Lancaster and downtown Los Angeles to provide continuous hourly data of ambient coarse PM concentration. Deployment commenced during April and May 2008 (Q2) and measurements continued through the end of the campaign.
- Detailed field sampling maintenance protocols were developed for the collection of both the time-integrated filter samples and continuous data for the regular weekly visit to each site.
- Supporting hourly air quality data (e.g. meteorological parameters) were acquired for each coarse PM sampling site covering the period of concurrent time-integrated filter sampling from Q2 of 2008 through Q2 of 2009.
- The mass concentration of each filter was determined by the gravimetric measurement of the filters in sampling each site on an on-going basis.
During Year 2, the LAB Coarse PM Study performed the following tasks:
- Completed the collection of weekly 24-hr integrated filter samples starting from early-April 2008 (Q2) to end of May 2009 (14 months). The coarse PM samplers at all the sites except sites in Los Angeles, Lancaster and Riverside were disassembled. The three samplers in the aforementioned sites were modified and designated for the intensive coarse PM sampling campaign.
- Designed, assembled, tested and deployed the coarse PM samplers to the field using an additional set of USC virtual impactor (VI) samplers for winter and summer intensive campaigns in 3 of the 10 sites representing distinct regions of Los Angeles Basin. The purpose of the intensive campaign is to collect samples in four distinct daily time periods to assess the diurnal variations in coarse PM concentrations and chemical composition. Phase 1 of the intensive campaign started in mid-July 2009 (Q3) and continued successfully for 5 consecutive weeks through late August 2009 at three locations. Phase 2 of the campaign will start in mid-January 2010 (Q1) and will continue until 4 successful consecutive data sets are obtained.
- QA/QC was performed on the continuous and time-integrated measurements (including measurements from intensive campaign) based primarily on the mass concentration data reported for each filter. Comparisons between the continuous and time-integrated data also helped to identify problematic data. > 88% of all collected filter samples passed QA/QC and were submitted for chemical and biological analysis.
The time-integrated mass concentration results indicate that ambient coarse PM varies from 0.5 µg/m3 to more than 35 µg/m3 at the ten sites in the Los Angeles basin. Mean 24-hour coarse PM concentrations at all sites are typically 10 µg/m3 with the exception of Lancaster site, where the average concentration is about half (5 µg/m3). Summer concentrations were typically 2 to 4 times higher than the winter concentrations at most sites. However summer concentrations in Long Beach were lower than in the winter. Concentrations derived from both of the samplers (PCIS and USC VI) were compared to each other at 9 of the 10 outdoor monitoring sites. Agreement in the coarse PM concentrations produced by these two samplers is very reasonable (within 15% on average) with PCIS concentrations typically lower.
CPM concentration correlations between different sites reveal similar trends of CPM concentrations in nearby sites. The Long Beach site, which is located in the “source” regions of Los Angeles basin, had weak correlations with other sites, while strong correlations were observed among the urban Los Angeles sites. Correlations between measured CPM and PM2.5 were investigated. PM2.5 particles are produced predominantly from vehicular emissions and high correlations indicate that the dominant source of coarse particles is traffic-induced resuspended PM in urban areas, where correlations were relatively higher. The relatively lower correlations in rural sites indicate that wind-blown dust is the significant contributor to CPM concentrations. Correlation of CPM and PM2.5 concentrations are much higher during winter than summer highlighting the increasing role of windblown dust in windier and dryer months in summer.
Spatial coefficients of divergence for the 24-hr integrated PCIS coarse PM mass concentrations were calculated. The median COD values ranged from 0.15 to 0.33 suggesting a fairly homogeneous-to modestly heterogeneous distribution of 24-hr based CPM for all the sites with the exception of Lancaster. With the inclusion of only the urban sites, the average median COD value is 0.13 indicating low spatial variability. There was no significant seasonal pattern discerned in the COD analysis.
Observations of continuous coarse PM concentrations and additional supporting data at three sites yielded interesting observations. Review of the diurnal profile of the monthly CPM concentrations indicated that month-to-month variability was limited and thus a seasonal description of the data was provided. The results show that the “source (USC)”, “receptor (Riverside)” and “desert (Lancaster)” CPM concentrations vary remarkably between sites in their diurnal patterns, seasonal variations, absolute concentrations and relationship to additional parameters including PM2.5 and PM10 concentrations. At almost all of the sites, CPM concentrations can be explained by wind-induced road dust re-suspension, particularly in drier seasons. In the desert site (Lancaster), CPM concentrations are virtually identical to PM10 concentrations while in Mira Loma and downtown Los Angeles, PM2.5 makes a more significant contribution to total PM10 concentrations. Correlation between the CPM concentrations at the three sites is generally poor with median r values varying from 0.1 to 0.4. However, the moderately high COD values (median COD > 0.35) indicate overall heterogeneity in inter-community CPM concentrations. CODs are relatively lower (0.4 or less) in the early morning and during middle of the day periods, while the values are higher during the morning commute and early evening hours. The higher values might result from doing the analysis using continuous data as opposed to 24-hour mean values, which emphasizes the benefit of collecting the data with higher temporal resolution. This result suggests that improved exposure assessments for CPM may be city-specific, and the daily temporal variability in mass concentrations should be considered to improve the accuracy of analysis.
Spatial variability was also assessed between the CPM concentrations at the paired Mira Loma/Rubidoux (separated by 7 km) and USC/downtown Los Angeles (separated by 2 km) sites. The CODs calculated for these two site pairs indicate higher heterogeneity (median COD up to 0.6) than that observed for the Lancaster-USC-Mira Loma site pairs separated by greater distances (median COD of around 0.4). These results suggest that variability in sources on sub-km scales can produce considerably different ambient concentrations of CPM, leading to highly variable population exposures to these particles. We conclude that improved exposure assessments for CPM must take into consideration the sharp gradients possible in CPM sources and sinks on relatively small spatial scales.
The major objectives for the next reporting period of the LAB Coarse PM project are:
- Start the second phase of intensive sample collection study,
- Continue chemical analysis of the collected samples,
- Continue biological analysis of the collected samples,
- Continue data analysis
- Prepare and present preliminary results at technical conferences, and
- Begin and complete the upcoming technical manuscripts to be submitted for peer-reviewed publication.
The second phase of the intensive sample collection study will be performed during Q1/Q2 to obtain “winter” data to pair with phase of summer data. The first phase of the intensive study was done in Q3/Q4. Chemical and biological analyses, data analysis, the preparation of conference presentations and technical manuscripts will continue through all 4 quarters of Year three.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
|Other project views:||All 21 publications||12 publications in selected types||All 12 journal articles|
||Moore KF, Verma V, Minguillon MC, Sioutas C. Inter-and Intra-community variability in continuous coarse particulate matter (PM10-2.5) concentrations in the Los Angeles area. Aerosol Science and Technology 2010;44(7):526-540.||
||Pakbin P, Hudda N, Cheung KL, Moore KF, Sioutas C. Spatial and temporal variability of coarse (PM10-2.5) particulate matter concentrations in the Los Angeles area. Aerosol Science and Technology 2010;44(7):514-525.||