title: Facility fence-line monitoring using passive samplers.
abstract: In 2009, the U.S. Environmental Protection Agency (EPA) executed a year-long field study at a refinery in Corpus Christi, TX, to evaluate the use of passive diffusive sampling technology for assessing time-averaged benzene concentrations at the facility fence line. The purpose of the study was to investigate the implementation viability and performance of this type of monitoring in a real-world setting as part of EPA's fence-line measurement research program. The study utilized 14-day, time-integrated Carbopack X samplers deployed at 18 locations on the fence line and at two nearby air monitoring sites equipped with automated gas chromatographs. The average fence-line benzene concentration during the study was 1075 parts per trillion by volume (pptv) with a standard deviation of 1935 pptv. For a 6-month period during which wind direction was uniform, the mean concentration value for a group of downwind sites exceeded the mean value of a similar upwind group by 1710 pptv. Mean value differences for these groups were not statistically significant for the remaining 6-month time period when wind directions were mixed. The passive sampling approach exhibited acceptable performance with a data completeness value of 97.1% (n = 579). Benzene concentration comparisons with automated gas chromatographs yielded an r2 value of 0.86 and a slope of 0.90 (n = 50). A linear regression of duplicate pairs yielded an r2 of 0.97, unity slope, and zero intercept (n = 56). In addition to descriptions of technique performance and general results, time-series analyses are described, providing insight into the utility of 2-week sampling for source apportionment under differing meteorological conditions. The limitations of the approach and recommendations for future measurement method development work are also discussed.
authors.affiliation: U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, Research Triangle Park, NC 27711, USA. thoma.eben@epa.gov
authors.forename: Eben D
authors.initials: ED
authors.lastname: Thoma
authors.forename: Michael C
authors.initials: MC
authors.lastname: Miller
authors.forename: Kuenja C
authors.initials: KC
authors.lastname: Chung
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Parsons
authors.forename: Brenda C
authors.initials: BC
authors.lastname: Shine
mesh_terms: D000393:Air Pollutants / Q000032:analysis; D000395:Air Pollutants, Occupational / Q000032:analysis*; D001554:Benzene / Q000032:analysis; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods; D007221:Industry; D010578:Petroleum; D015203:Reproducibility of Results; D014481:United States; D014484:United States Environmental Protection Agency
chemical_list: D000393:Air Pollutants; D000395:Air Pollutants, Occupational; D010578:Petroleum; D001554:Benzene