Skip common site navigation and headers
United States Environmental Protection Agency
Exposure Research
Begin Hierarchical Links EPA Home > Research & Development > Exposure Research > Publications/Presentations > End Hierarchical Links

 

Field Method Comparison Between Passive Air Samplers and Continuous Monitors for Volatile Organic Compounds and NO2 in El Paso, Texas, USA

spacer
spacer
Abstract: Passive sampling of gas-phase air toxics and criteria pollutants has become an attractive monitoring method in human exposure studies due to the relatively low sampling cost and ease of use. This study evaluates the performance of Model 3300 Ogawa(TM) Passive NO2 Samplers and 3M(TM) 3520 Organic Vapor Monitors (OVMs) by comparing the integrated passive sampling concentrations to averaged hourly NO2 and VOC measurements made at two continuous air monitoring stations (CAMS) operated by the Texas Commission on Environmental Quality (TCEQ) in the U.S.-Mexico border city of El Paso, Texas. Passive samplers were deployed over three time intervals (3 day weekend, 4 day weekday, and 7 day weekly) for three consecutive weeks, from November 29, 1999 through December 17, 1999. OVM concentrations were corrected for ambient pressure to account for the higher elevation in El Paso. Highly precise results (< 5 % relative standard deviation, RSD) were found for NO2 measurements from collocated Ogawa samplers. Reproducibility was lower from duplicate OVMs for the BTEX (benzene, toluene, ethylbenzene, and xylene isomers) VOC species (>/- 7 % RSD for 2 day samples) with better precision for longer sampling periods. Comparison of Ogawa N02 samplers with chemiluminescence measurements averaged over the same time period suggested potential calibration problems with the chemiluminescence analyzer at the sites, although further evaluation of the Ogawa sampler with continuous measurements was considered necessary. For the BTEX species compared, generally good agreement was obtained between OVMs and auto-GC measurements. The OVMs successfully tracked increasing levels of organic pollutants recorded by the continuous monitors. However, except for toluene, the OVM BTEX measurements generally exceeded their continuous counterparts with a mean bias ranging from 5-10 %. Although the interpretation of the study results was limited due to small sample sizes, diffusion barrier influences due to the design of the shelters, used to house the OVMs, and differences in sampling heights between OVMs and the auto-GC inlet may explain the over-estimation. This study demonstrates the need to perform additional evaluation of collocated passive samplers/with continuous monitors and/or other pumped sampling methods to further evaluate the precision and sampling rate.

The U.S. EPA through its Office of Research and Development funded and managed the research described here under contract 68-D-99-012 to Research Triangle Institute and contract 68-D0-0206 to ManTech Environmental Technology, Inc. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.
spacer
Citation:Mukerjee, S., L. Smith, G. A. Norris, M. T. Morandi, M. Gonzales, C. A. Noble, L. Neas, and A. H. Ozkaynak. Field Method Comparison Between Passive Air Samplers and Continuous Monitors for Volatile Organic Compounds and NO2 in El Paso, Texas, USA. JOURNAL OF AIR & WASTE MANAGEMENT ASSOCIATION 54(3):307-319, (2004).
spacer
spacer
Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
spacer
Division: Human Exposure & Atmospheric Sciences Division
spacer
Branch: Exposure Modeling Research Branch
spacer
Product Type: Journal
spacer
Published: 03/01/2004
spacer
Downloads:
spacer
Bullet Item Field Method Comparison Between Passive Air Samplers and Continuous Monitors for Volatile Organic Compounds and NO2 in El Paso, Texas, USA
spacer
spacer
Related Entries:
spacer
Bullet Item Measurement and Modeling of Air Pollutants in El Paso, Texas
spacer Relationship Reason:   A Project of the Product
spacer
spacer
spacer

 

ORD Home | Search EPA | Search NERL | Search EIMS | Contacts | Help

 
Begin Site Footer

EPA Home | Privacy and Security Notice | Contact Us

Last Updated on Monday, October 22, 2007
URL: http://cfpub.epa.gov