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37 SECTION 6 Ambient Hazardous Air Pollutant Measurements This section reviews the measurements of ambient HAP infer any information regarding average concentrations. For concentrations on or near airports and is divided this into example, the benzene concentrations reported varied from three main categories: (1) inside terminal buildings, (2) on 0.15 to 13.1 ppb. airport grounds, and (3) in nearby communities. Instead of During the recent APEX campaigns, most instruments presenting an exhaustive review of all known studies, we pre- used for the study sampled airport air continuously between sent only key results from various studies and refer to two dedicated engine tests and thus collected several days worth excellent documents that present a more in-depth review of of data at OAK and Cleveland Hopkins International Airport past measurement campaigns--the 2005 ORD final environ- (CLE). At the OAK site, the measurement team was set up at mental impact statement (FAA 2005), and the 2003 FAA a ground run-up enclosure that was downwind of an active review (URS 2003). taxiway. As such, the site was exposed to advected exhaust plumes 10 to 60 sec in duration from idling aircraft. Over long time periods (more than 3 hr), the average concentra- 6.1 Hazardous Air Pollutants tions were minimally affected by this intermittent compo- Concentrations Inside the Airport nent and were very close to the "background" concentrations. There are few measurements of HAPs inside airport build- At times of heavy air traffic, however, the average concentra- ings. Measurements of aldehydes in an airport in Strasbourg, tions could be significantly higher depending on the how France found a negligible difference between indoor and out- often idling aircraft passed upwind of the site. For example, door concentrations at the airport, though the outdoor during one busy 45-min time period, the average concentra- concentrations were among the highest recorded at various tion of formaldehyde was 2.4 ppb, compared to background outdoor locations. Average formaldehyde and acetaldehyde concentrations of 0.6 ppb. These measurements show that concentrations were 11 g/m3 and 4 g/m3, respectively the air at OAK is not well mixed, and that accurately quanti- (Marchand, Buillot et al. 2006). PAH measurements inside an fying the air quality at an airport would require measure- Italian airport found benzo[b+j+k] fluoranthene and benzo ments at numerous locations. [a]-pyrene concentrations to be of concern (Iavicoli, Carelli In contrast, the measurement site at APEX3 was situated and Bergamaschi 2006). Other PAHs measured included on the outskirts of the airport property and no discernable naphthalene, 2-methylnaphthalene, 1-methylnaphthalene, aircraft exhaust plumes were observed. There has been little and biphenyl. analysis of diurnal data taken at this site. 6.2 Hazardous Air Pollutants 6.3 Hazardous Air Pollutants Concentrations on Airport Concentrations in Adjacent Grounds Neighborhoods Among the only peer-reviewed papers are measurements Much more effort has been devoted to the measurement of of CO, NOx, and numerous VOCs from Zurich airport HAPs in adjacent neighborhoods and at airport boundaries, (Schurmann, Schafer et al. 2007). VOC measurements were with mixed results. Some measurements have shown that limited to several "snapshot" measurements near the taxiway. concentrations are no higher than in other urban settings Due to the limited number of measurements, it is hard to (McGulley, Frick and Gilman, Inc. 1995), whereas others
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38 have inferred an airport influence based on comparison of trations presumably because they were affected less by auto upwind and downwind measurements (Rhode Island emissions." Only eight compounds were above the instru- Department of Environmental Management 2007). Most mental detection limit (Municipality of Anchorage 2003, 7). studies have relied on measurements with low temporal res- Ambient pollutant concentrations were measured at olution and have struggled to identify the cause of the Toronto's Lester B. Pearson International Airport (LBPIA) enhanced concentrations (aircraft versus nearby roads, etc). from May 2005 through April 2006 (Tradewind Scientific Most of the compounds emitted by aircraft exhaust (NOx, 2006). The purpose of the study was to assess the air pollution CO, black carbon, VOCs, SO2) are also emitted by other resulting from airport activities and aircraft operations. The urban sources, particularly on-road vehicles. There are few if study employed a mobile laboratory that was moved between any unique tracer compounds that have been used to connect five carefully chosen locations on the airport grounds. ambient measurements to airport emissions (which include Stationary monitoring was conducted at each location for both aircraft and vehicle emissions). Furthermore, a conclu- extended time periods. Mixing ratios of several pollutants sion that demonstrates that pollutant concentrations near an were reported as hourly averages. The study continuously airport are no higher than in other urban locations does not measured levels of CO, NO2, NO, NOx, O3 and PM2.5 as well imply that the airport had no influence. as wind speed, wind direction, and ambient temperature. In addition, total suspended particulates (TSP) and speciated hydrocarbon compounds were determined using samples 6.3.1 Discerning an Airport Influence acquired during 24-hr periods every sixth day. The measure- on Elevated Concentrations ment data were analyzed using a variety of methods includ- Results from the TF Green Air Monitoring Study at Prov- ing interspecies correlation, correlation with wind speed, and idence Airport (PVD) (Rhode Island 2007) showed that no comparison with simultaneous measurements made at a VOC concentrations exceeded the acute or chronic non- nearby air quality monitoring station. This study did not cancer health benchmarks at five sites near the airport in focus on HAPs measurements though there is undoubtedly Warwick. Average concentrations, however, of benzene, 1,3- some information about HAPs emissions in the less frequent butadiene, formaldehyde, acetaldehyde, acetone, chloroform, speciated hydrocarbon measurements. carbon tetrachloride, and perchloroethylene exceeded the The major conclusions of the study were that the meas- cancer benchmark levels. At all measurement sites, the con- ured pollutant concentrations at the airport are strongly centrations of these HAPs were lower than at an urban meas- affected by the background concentrations surrounding urement site in Providence. Since the chlorinated com- the airport and that this data set could be used for further pounds are mainly caused by use of chlorinated solvents (as studies of air pollution impacts, pollutant distribution, dis- opposed to combustion sources such as aircraft or diesel ex- persion processes and emission chemistry. Also, the com- haust), the Rhode Island Department of Environmental plete data set could be used to test dispersion models of the Management is inspecting sources of such solvents in the airport's pollutant emissions. One specific finding was that area. Inference of an airport influence based solely on the CO levels were elevated at the measurement site that was measured VOC concentrations and wind direction was in- located on the apron near one of the terminals. Local conclusive, mainly because the averaging time was 24 hr for sources at that location would probably include aircraft most data (with some 3-hr samples) and thus correlations service vehicles, idling aircraft and the terminal itself. As with wind speed were not very meaningful. However, 1-min the study concluded, further analysis of the measurement averaged measurements of black carbon, which is emitted by data is needed to draw stronger conclusions about source both aircraft and diesel engines, showed a clear increase at the strengths and locations. four measurement sites closest to the airport when the wind was blowing from the airport. Furthermore, the temporal 6.3.2 Source Apportionment profile of the elevation in black carbon measurements coin- cided with the increase in jet activity at the airport in the early The 1999 study by KM Chng attempted to use "advanced morning. Further measurement studies and investigation of chemical fingerprinting" to ascertain the influence of aircraft lung cancer data are planned. exhaust on soot deposition near ORD. The study concluded In contrast, a suite of 24-hr average VOC measurements that samples collected near ORD more closely resembled on- conducted for one month at various locations near Ted road vehicle exhaust than they did aircraft exhaust (KM Chng Stevens Anchorage International Airport was unable to dis- 1999). Although this study focused on particulate matter, its cern a difference between upwind and downwind sites, and findings on VOC emissions and concentrations were similar. concluded that "Sites in and around airport tended to have This study was subsequently criticized by the Park Ridge lower BETX (benzene ethylbenzene toluene xylene) concen- studies (ENVIRON 2000).
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39 Figure 14. San Leandro Marina and Oakland International Airport. Figure 15. Time series of measurements recorded 2 km downwind of OAK. 6.3.3 San Leandro Measurements craft exhaust plumes resulting from idle, take-off, and landing activity could be resolved. The average HCHO At the conclusion of the JETS-APEX2 study, the Aerodyne concentration in the time series shown is 1.3 ppb, while the Mobile Laboratory spent two days at the San Leandro Marina interpolated background value is approximately 0.8 (simi- (Figure 14), which is ~2 km downwind of the OAK runway. lar to the background value observed on the airport Winds were consistently from the northwest. Although lim- grounds). More importantly, a dilution factor of ~5000 can ited in duration, these measurements are unique in that they be inferred for most of the observed plumes based on com- enabled observations of diluted airport emissions with no parison of the observed CO2 to known CO2 concentrations interferences from non-airport sources, since there is no land at the exit of a high-bypass turbine engine. Such a simplified in between the emissions and the measurement site. source-receptor scheme would be an ideal scenario for test- A 6-hr time-series of HCHO, CO, NOx, CO2, and PM ing dispersion models. number concentration is shown in Figure 15. Individual air-