AN APPRAISAL OF NO PASSIVE SAMPLING X by Leah Kathleen Cambal BS Chemistry, Saint Vincent College, 2008 MPH, University of Pittsburgh, 2012 Submitted to the Graduate Faculty of Graduate School of Public Health in partial fulfillment of the requirements for the degree of Doctor of Public Health University of Pittsburgh 2015 UNIVERSITY OF PITTSBURGH GRADUATE SCHOOL OF PUBLIC HEALTH This dissertation was presented by Leah Kathleen Cambal It was defended on April 6th, 2015 and approved by Linda Pearce, PhD, Assistant Professor, Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh Emily Elliott, PhD, Associate Professor, Department of Geology and Planetary Sciences, Dietrich School of Arts and Sciences, University of Pittsburgh Ravi Sharma, PhD, Assistant Professor, Department of Behavioral and Community Health Sciences, Graduate School of Public Health, University of Pittsburgh Dissertation Advisor: James Peterson, PhD, Associate Professor, Department of Environmental and Occupational Health, Graduate School of Public Health, University of Pittsburgh ii Copyright © by Leah K. Cambal 2015 iii James Peterson, PhD AN APPRAISAL OF NO PASSIVE SAMPLING X Leah K. Cambal, DrPH University of Pittsburgh, 2015 ABSTRACT Associated with chronic and short-term health effects, the public health consequences of ambient air pollution are considerable. Accurate measurement of air pollutants is critical for assessing exposure to pollutants as well as an essential step in reducing public health impacts through implementation of regulations and emission controls. Passive sampling devices are often used for the regional-scale determination of pollutants when knowledge of hourly fluctuations in concentrations is unnecessary. Often advantageously described as cost-effective and simple to use, passive samplers are increasingly utilized as an alternative to conventional active sampling. However, the accuracy of these descriptions is challenged by the findings of the subsequent research. The overall objective of this research was to assess the ability of a well-known passive sampler to accurately measure concentrations of nitrogen oxides (NO ) x in the ambient environment. While the passive measurement of numerous pollutants is heavily studied, literature evaluating the use of passive sampling devices for the measurement of NO is exceedingly x limited. NO is a generic term for a group of highly reactive gases composed of oxygen and nitrogen but x most commonly NO is defined as the sum of nitric oxide (NO) and nitrogen dioxide (NO ). The trapping x 2 of NO using filters coated with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) for x quantitative analysis was investigated using various methods including ambient sampling, electronic absorption spectroscopy, mass spectrometry, and electron paramagnetic resonance. A first of its kind air sampling campaign in New Zealand measured ambient NO concentrations at multiple locations using x Ogawa passive samplers. High spatial variability in pollutant concentrations was found across the sampling area but accuracy of the concentrations was questioned. At low ambient NO concentrations x PTIO was found to contribute significantly to the analytical absorbance value. The fraction contributed by PTIO became increasingly difficult to quantitate as the contribution was not uniform across exposed filters. Degradation of PTIO during ambient exposure, evident by the loss of the filter color, was heavily dependent on the sampling environment. Intra- and inter-season variations in the magnitude of degradation are reported. Common limitations of various types of passive samplers are presented as well as challenges currently unaddressed in the literature. iv TABLE OF CONTENTS PREFACE .......................................................................................................................................... XI DEFINITIONS & ABBREVIATIONS ..................................................................................................... XIII 1.0 INTRODUCTION – NITROGEN OXIDES (NO ) ................................................................................1 X 1.1 HEALTH EFFECTS OF NO ...................................................................................................3 X 1.2 PROTECTION AGAINST EXPOSURE TO NO .........................................................................5 X 1.3 AMBIENT SOURCES OF NO ...............................................................................................5 X 1.4 VEHICULAR SOURCES ........................................................................................................6 1.4.1 The combustion process – NO formation in engines .............................................6 x 1.4.2 Emissions of NO from vehicles .............................................................................7 x 1.4.3 Mitigation of vehicle emissions .............................................................................9 1.4.4 The NO /NO ratio ................................................................................................9 2 x 1.5 PHOTOCHEMICAL REACTIONS AND THE PRODUCTION OF OZONE ..................................... 11 1.6 MONITORING METHODS FOR NO ................................................................................... 13 X 1.6.1 Active monitoring ............................................................................................... 14 1.6.2 Passive monitoring – the Ogawa sampler ............................................................ 15 1.6.3 Characteristics of active and passive monitors ..................................................... 18 2.0 INSTRUMENTATION & METHODS ............................................................................................. 19 2.1 INSTRUMENTATION ........................................................................................................ 19 2.1.1 Concentration analysis ........................................................................................ 19 2.1.2 Degradation analysis .......................................................................................... 20 2.2 PASSIVE SAMPLING METHODS ........................................................................................ 21 2.3 ANALYTICAL METHODS ................................................................................................... 26 2.3.1 NO and NO filter preparation for analysis .......................................................... 26 x 2 2.3.2 NO concentration analysis ................................................................................. 26 2 2.3.3 NO concentration analysis ................................................................................. 27 x 2.3.4 Concentration calculations .................................................................................. 29 2.3.5 O concentration analysis.................................................................................... 30 3 2.3.6 Degradation analysis .......................................................................................... 31 2.3.6.1 Influence of specific environmental factors – light and temperature .......... 31 v 2.3.6.2 Influence of storage .................................................................................. 32 2.3.6.3 Identification of compounds present on NO filters.................................... 32 x 3.0 PASSIVE NO SAMPLING IN AUCKLAND, NEW ZEALAND ............................................................ 34 X 3.1 INTRODUCTION ............................................................................................................... 34 3.2 RESULTS .......................................................................................................................... 40 3.2.1 Ambient concentrations ..................................................................................... 40 3.2.2 Passive NO /NO Ratios ...................................................................................... 45 2 x 3.2.3 Variation in NO filters ........................................................................................ 47 x 3.3 DISCUSSION .................................................................................................................... 49 3.3.1 Ambient concentrations ..................................................................................... 49 3.3.2 Passive NO /NO ratios ....................................................................................... 51 2 x 3.3.3 Variation in NO filters ........................................................................................ 53 x 3.4 CONCLUSIONS AND LIMITATIONS .................................................................................... 57 3.4.1 NO and NO concentration values caveat ............................................................ 58 x 4.0 DEGRADATION OF PTIO COATED NO FILTERS .......................................................................... 59 X 4.1 INTRODUCTION ............................................................................................................... 59 4.2 RESULTS .......................................................................................................................... 61 4.2.1 Challenges ensuing from the measurement of NO filters .................................... 61 x 4.2.2 Influence of specific environmental factors – light and temperature .................... 65 4.2.3 Influence of storage ............................................................................................ 66 4.2.4 Identification of compounds present on NO filters ............................................. 66 x 4.2.4.1 Electronic absorption spectroscopy ........................................................... 66 4.2.4.2 Mass spectrometry ................................................................................... 68 4.2.4.3 Electron paramagnetic resonance ............................................................. 75 4.3 DISCUSSION .................................................................................................................... 77 4.3.1 Challenges ensuing from the measurement of NO filters .................................... 77 x 4.3.2 Influence of specific environmental factors – light and temperature .................... 78 4.3.3 Influence of storage ............................................................................................ 79 4.3.4 Identification of compounds present on NO filters ............................................. 80 x 4.3.4.1 Mass spectrometry ................................................................................... 80 4.3.4.2 Electron paramagnetic resonance ............................................................. 80 4.3.4.3 Electronic absorption spectroscopy ........................................................... 80 vi 4.4 CONCLUSIONS ................................................................................................................. 81 5.0 A REVIEW OF PASSIVE SAMPLING WITH SPECIAL REGARD TO NO ANALYSES ............................ 84 X 5.1 INTRODUCTION ............................................................................................................... 84 5.2 TYPES OF PASSIVE SAMPLERS .......................................................................................... 87 5.2.1 Tube-type samplers ............................................................................................ 87 5.2.2 Badge-type samplers .......................................................................................... 88 5.2.3 Radial-type samplers .......................................................................................... 89 5.3 ANALYTICAL METHODS ................................................................................................... 91 5.4 INLFUENCE OF ENVIRONMENTAL FACTORS ON PASSIVE SAMPLING .................................. 91 5.4.1 Influence of air velocity....................................................................................... 91 5.4.2 Influence of temperature .................................................................................... 94 5.4.3 Influence of humidity .......................................................................................... 95 5.5 CHEMICAL INTERFERENCES DURING PASSIVE SAMPLING .................................................. 99 5.6 THE USE OF SHELTERS AND PROTECTIVE MEMBRANES ................................................... 102 5.7 TRIETHANOLAMINE (TEA) ABSORBENT .......................................................................... 104 5.7.1 Chemical interferences with TEA ....................................................................... 106 5.8 COMPARISION OF RESULTS – ACTIVE VERSUS PASSIVE MONITORING ............................. 107 5.9 CONCLUSIONS AND CONSIDERATIONS ........................................................................... 107 6.0 OVERALL CONCLUSIONS AND RECOMMENDATIONS ............................................................... 109 BIBLIOGRAPHY ............................................................................................................................... 111 vii LIST OF TABLES Table 1. Ogawa NO and NO Filter Characteristics .................................................................................... 17 x 2 Table 2. Comparative characteristics of passive and active air samplers ................................................... 18 Table 3. Calculation of NOx, NO2, NO Concentrations Part 1 .................................................................... 29 Table 4. Calculations of NOx, NO2, NO Concentrations Part II ................................................................... 30 Table 5. Average over (+) or under (-) estimation of concentration (ppb) from passive samplers ............ 49 Table 6. Measured temperature and humidity values across studies ........................................................ 56 Table 7. Mass spectrometry results: Sigma-Aldrich PTIO solution ............................................................. 70 Table 8. Mass spectrometry results: Sigma-Aldrich PTIO solution in amber vial ....................................... 72 Table 9. Mass spectrometry results: Filters unexposed to ambient conditions ......................................... 73 Table 10. Mass spectrometry results: Filters exposed to ambient conditions ........................................... 73 Table 11. Mass spectrometry results: PTIO solutions + NO ........................................................................ 74 Table 12. Effect of meteorological factors on a variety of TEA absorbent NO2 passive badges ................ 99 viii LIST OF FIGURES Figure 1. Ogawa sampler components ....................................................................................................... 16 Figure 2. Multipollutant air sampling unit .................................................................................................. 22 Figure 3. Gas samplers housed in Ogawa shelters...................................................................................... 23 Figure 4. “SpaRTANZ” gas monitoring locations ......................................................................................... 24 Figure 5. The Auckland Region of New Zealand ......................................................................................... 35 Figure 6. A brown haze over Auckland ....................................................................................................... 36 Figure 7. Temporally adjusted [NO] in Auckland, New Zealand ................................................................. 41 Figure 8. Temporally adjusted [NO ] in Auckland, New Zealand ................................................................ 42 2 Figure 9. Temporally adjusted [NO ] in relation to diesel sources ............................................................. 44 x Figure 10. [NO ] versus distance to nearest diesel source ......................................................................... 45 2 Figure 11. Ratio of NO /NO versus [O ] ..................................................................................................... 46 2 x 3 Figure 12. Ratio of NO2/NOx versus [NO ] ................................................................................................. 47 x Figure 13. Variation in filter coatings following exposure .......................................................................... 48 Figure 14. Two types of shelters used in air monitoring studies ................................................................ 54 Figure 15. Variation in NO filters between batches ................................................................................... 55 x Figure 16. Reaction between PTIO and NO ................................................................................................ 59 Figure 17. Electronic absorption spectrum: NO filter extract solution and a standard NaNO solution .. 62 x 2 Figure 18. Blank-corrected NO and NO calibration curves....................................................................... 63 2 x Figure 19. Blank-corrected NO and NO calibration curves post ether extraction ................................... 64 2 x Figure 20. Detection of NO - in filter extracts unexposed to the ambient environment ........................... 68 2 Figure 21. Protonation of PTIO ................................................................................................................... 69 Figure 22. Mass spectrometry: PTIO solution – hv ..................................................................................... 70 ix Figure 23. Mass spectrometry: PTIO solution + hv ..................................................................................... 71 Figure 24. Formation of [PTIH + H] + in the presence of NO ....................................................................... 75 Figure 25. Electronic paramagnetic resonance of various PTIO solutions.................................................. 76 Figure 26. Schematic diagram of a tube-tube diffusion sampler ............................................................... 86 Figure 27. Badge-type sampler ................................................................................................................... 89 Figure 28. Radial-type sampler ................................................................................................................... 90 x