During the 1997 ozone smog season, ambient data was collected at three PAMS (Photochemical Assessment Monitoring Station) sites and fifteen ozone monitoring sites within Maine. One of the ozone monitors was located on the Scotia Prince, a passenger ferry that traveled daily between Yarmouth, Nova Scotia and Portland, Maine.

Assessment of the PAMS data, collected during times when Maine's ozone monitoring sites recorded exceedences of the federal ozone standard (0.124 ppm), indicated that ozone levels in Maine are elevated by short-range, anthropogenic (human-made) precursor emissions. Analysis of benzene/toluene, NMOC/NOx, NMOC/NOy ratios, MIR's (Maximum Incremental Reactivity) and other hydrocarbon relationships demonstrates that ozone precursor emissions are transported into and generated within the State of Maine.

Mobile sources are important contributors to these emissions.

The study of transported pollution into and throughout the Northeast is not a new undertaking. To Maine's benefit, a tremendous amount of new information over the last few years has enlightened scientists to more fully appreciate the complex meteorological processes that influence pollution transport at a coastal interface. Over the past several years, the Bureau of Air Quality has dedicated significant resources to quantify the extent and significance of pollution transported into Maine, and the significance of pollution generated within the state. Ongoing analysis of pollution during the last several years indicates that human-made pollution made within short distance of air samplers do have a negative influence on the air quality within the state of Maine.

While it is widely recognized that good science should be the driving force behind good policy, air pollution control administrators have often been forced to make environmental decisions based on political and economic pressures rather than on science alone. Such has been the case in Maine where policymakers have been forced to decide what strategies to employ for reducing air pollution, amid scientific uncertainty and strong public opposition. The findings detailed here provide insight as to which human-made compounds contribute most to the formation of ground-level ozone, and will be useful in making future policy determinations.

Ozone smog is a secondary pollutant, meaning that It is not created by one process, but rather through a series of complex atmospheric and chemical reactions. Ozone has both natural and human-made (anthropogenic) sources in the lower levels of the atmosphere. The primary natural source of ozone near the earth's surface is direct injection from the stratosphere. In addition, ozone is photochemically (with the direct interaction from sunlight) produced in the troposphere from ozone precursors. Precursors are the raw chemical ingredients that react to generate ozone. They are the oxides of nitrogen (NOx), and volatile organic compounds (VOC's). At elevated levels ozone is known to damage human lungs and vegetation. It also plays a role in fashioning climate change. Because of its role in tropospheric photochemistry, ozone can modify global climate by influencing the concentrations of chemically active "greenhouse" gases such as methane.

Since 1993, the Bureau of Air Quality has been involved in continuous ambient hydrocarbon (VOC) monitoring at Two Lights State Park in Cape Elizabeth, Maine, southeast of Portland, Maine. These hydrocarbon measurements have been used in international field studies focusing on ozone smog production in the North Atlantic, and have provided the basis for deploying two other gas chromatographs along the coast of Maine. The data collected at these locations, in conjunction with Maine's 15 ozone monitors, has recently provided analysts a much clearer picture of the significance of local and regional ozone precursor pollution. The sampling and analysis procedures followed were those of the U.S. Environmental Protection Agency's Photochemical Assessment Monitoring Stations Program.

Throughout the course of this paper, the reader should be familiar with the following acronyms: CETL (Cape Elizabeth Two Lights monitor), BHCM (Bar Harbor Cadillac Mountain monitor), BHMF (Bar Harbor McFarland Hill monitor) and KFS (Kittery Frisbee Street monitor). Surface temperatures will be noted in degrees Fahrenheit, while temperatures aloft will be frequently noted in degrees Celsius. The two layers aloft (850 mb and 500 mb's) are two pressure levels that can best describe the mechanics of what is happening in the atmosphere above the surface. The 850 mb chart details weather conditions at the 850 mb level or around 5000 feet above sea level. The 500 mb level is often referred to as the steering level. Most weather systems and precipitation follow the winds at this height. This level averages around 18,000 feet above sea level and is roughly half-way up through the weather producing part of the atmosphere called the troposphere. NOAA stands for the National Oceanic and Aviation Administration.

Some of the most vital information in this study was generated by three continuous air sampling monitors, gas chromatographs (or GC's). The State of Maine Department of Environmental Protection, (DEP) and the State of New Hampshire are required to analyze the impacts of upwind pollution from Boston, Mass., and Portsmouth, New Hampshire and other metropolitan areas at three GC's located within the state of Maine. The first site is located in Kittery (KFS), the second in Cape Elizabeth (CETL), and the third is located on Cadillac Mountain in Acadia National Park (BHCM).

These GC's draw in outside (ambient) air continuously for forty minutes each hour, and identify what types of volatile organic compounds (hydrocarbons) are present in the atmosphere. For the most part, these instruments sample human-made VOC's, although they also measure biogenic (natural) compounds. The data generated by the GC's can also be used to ascertain the relative age of the reactive hydrocarbons, and their potential to generate ozone pollution.

The Scotia Prince is a commercial passenger ship that traverses the Atlantic waters between Portland, ME and Yarmouth, NS. The vessel makes the voyage twice daily, and allows researchers (for the first time), the opportunity to document the phenomena of multiple plumes of ozone pollution in the marine environment.

Daily synoptic weather features (surface analysis and infrared satellite photos) at both 12Z and 0Z were obtained by accessing the Purdue Weather Archive network on the web. Winds aloft and 850 mb temperatures were extrapolated using files generated from the NOAA's ETA model.

Ratios between known compounds (such as Benzene/Toluene); and their relative reactivities have been effective in determining the "freshness" or "age" of an air parcel. Age means that more reactive organic compounds have undergone photochemical reactions and have chemically changed. It is a way to determine whether or not the pollution captured is old, transported air, or is newly generated (and more than likely attributable to nearby sources).

Morning NMOC/NOy, NMOC/NOx ratios have been used to indicate if the precursors to ozone formation are Nox-limited or VOC-limited. There are two time periods that seem to establish the ozone formation limitations of an air parcel in Maine. The first time period, between the hours of 5 AM and 9 AM, represents the time of day when ozone production has "reset itself" to reflect lowest reading of the day. Also, at this time of day there is little or no discernable influence of vertical mixing (the transporting of ozone and its precursors from higher elevations back down to the surface after the sun's rays break up the morning inversion), and there is less dilution potential. Ozone precursors that are emitted early in the day provide the raw ingredients for photochemistry. The second important time for determining the limitations of an air parcel's ability to create ozone is just before the event occurs. One caveat must be noted at this time. NOy is an indicator of reacted NOx. A NMOC/NOy ratio in the morning may not be as useful for the purpose of determining whether an ozone event is NOx limitation.

A detailed account of the ozone exceedance day summary for Maine can be viewed at the end of the document.

Meteorology:

Several assessment techniques can be used to determine whether or not additional VOC's or additional NOx were enhanced ozone formation. On the whole, O3/Noy and O3-40/NOy ratios seem to indicate that an air mass is more inclined to be more NOx limited. The latest school of thought by atmospheric chemists on determining the appropriate limitation of an air parcel tends to lean toward NMOC/NOx and NMOC/NOy ratios as the best indicators.

The 1997 Maine data illustrates that all of the fresh, short-range transported anthropogenic emissions within 150 miles of the receptors in Maine negatively impacted the air quality within Maine. Support for this conclusion comes from the executive summary from the Ozone Transport Assessment Group (OTAG), (OTAG 1995) which concluded that the most substantial affects on an areas' inability to attain the federal ozone standard lies within the short range transport range of 30-150 miles. OTAG's claim is substantiated by findings here in, which indicate that anthropogenic emissions from Maine and New Hampshire (as well as the other New England states) are significant contributors to elevating ozone concentrations in Maine.

The Cape Elizabeth and Kittery sites appear to be slightly more VOC-limited (meaning that an increase in hydrocarbons yields elevated ozone smog readings), whereas the ozone production at the downwind site of Cadillac Mountain is more dependent on the existence of nitrogen oxides. This is consistent with many previous findings that indicate as urban plumes move downwind, the accumulated source of hydrocarbons eventually exceeds the supply of NOx and the chemistry shifts from VOC to NOx-limited.

The quantity of biogenic VOC's, especially the most prevalent reactive species of isoprene, was found to comprise half (or less than half) of the "reactive compounds" during both of the episodes analyzed. This means that even though biogenic VOC's played a role in the production of ozone during these time periods, it was in no means the prominent generator of ozone. A comparison of the air samples taken in Boston, laden with the signature of fresh automobile exhaust, and those found at the Cape Elizabeth and Kittery sites are remarkably alike and exhibit similar benzene to toluene ratios. Historically, the greatest number of ozone exceedances occur during holiday weekends in the summer when transportation and utility demands are greatest throughout the state, and anthropogenic emissions are at their annual peaks.

If Maine wanted to reduce the compounds that created the most ozone during the days of federal exceeedances, the following compounds should be targeted: isoprene, toluene, ethane, ethylene, propylene, isopentane, m&p-xylene and 1,2,3- trimethylbenzene, benzene, 2-Methylpentane and n-Butane. These compounds all were found in exhaust from automobiles or diesels with the exception of: 1,2,3- trimethylbenzene (Sagebiel 1996). Isoprene is produced mostly by trees, but, it does make up a small part of exhaust of autos and diesels ( Sagebiel 1996).

Clearly the influence of short-range transport of ozone and its precursors introduced into the atmosphere close to and within Maine during these three days in 1997 caused a significant degradation of air quality within Maine. It is obvious that long-range pollution transported into Maine negatively influences the air quality within Maine, but obviously to a much lesser degree.

The key question for Maine policy-makers is: "What emission reduction strategy should Maine use to reduce Maine's ozone problem?". The analysis of monitored data from these three days, during the summer of 1997 when ozone smog levels exceeded the federal standard, demonstrates that improvements in Maine's air quality would be gained if there were substantially less human-made VOC's and NOx generated within the State of Maine.

Figure 1. Comparison of Ozone Values Across Maine 6/21/97-6/22/97

Figure 2. Ozone Conc. on 6/21/97 mapped with the Ozone Mapping System

Figure 3. Surface Plot for 00Z 22 Jun 1997

Figure 4. 500 mb winds for 0000Z Jun 22 1997

Figure 5. 850 mb temperatures for 0000Z Jun 22 1997

Figure 6. GOES East IR Satellite for 0015Z Jun 22 1997

Figure 7. KFS 24 Hour Back Trajectory for 00UTC 22 Jun 1997

Figure 8. CETL 24 Hour Back Trajectory for 00UTC 22 Jun 1997

Figure 9. BHCM 24 Hour Back Trajectory for 00UTC 22 Jun 1997

Figure 10. NOx Limited or VOC Limited on 6/21/97 and 6/22/97

Figure 11. Comparison of TNMOC Values on 6/21/97 and 6/22/97

Figure 12. Comparison of Benzene Values on 6/21/97 and 6/22/97

Figure 13. Comparison of Toluene Values on 6/21/97 and 6/22/97

Figure 14. Comparison of m/p Xylene Values on 6/21/97 and 6/22/97

Figure 15. Comparison of Ethylene Values on 6/21/97 and 6/22/97

Figure 16. Comparison of Benzene and Toluene Ratios on 6/21/97 and 6/22/97

Figure 17. Comparison of 1997 Maine data and EPA Round Robin Canisters

Figure 18. MIR for KFS on 6/21/97 and 6/22/97

Figure 19. MIR for CETL on 6/21/97 and 6/22/97

Figure 20. MIR for BHCM on 6/21/97 and 6/22/97

Figure 21. Scotia Prince Yarmouth to Portland 6/21/97

Figure 22. Scotia Prince Portland to Yarmouth 6/21/97 to 6/22/97

Figure 23. Surface Plot for 00Z 23 Jun 1997

Figure 24. GOES East IR Satellite for 0015Z Jun 1997

Figure 25. 500 mb winds for 0000Z Jun 23 1997

Figure 26. 850 mb temperatures for 0000Z Jun 23 1997

Figure 27. Ozone Conc. on 6/22/97 mapped with the Ozone Mapping System

Figure 28. KFS 24 Hour Back Trajectory for 00UTC 23 Jun 1997

Figure 29. CETL 24 Hour Back Trajectory for 00UTC 23 Jun 1997

Figure 30. BHCM 24 Hour Back Trajectory for 00UTC 23 Jun 1997

Figure 31. Ozone Conc. on 6/29/97 mapped with the Ozone Mapping System

Figure 32. Ozone Conc. on 6/30/97 mapped with the Ozone Mapping System

Figure 33. Ozone Conc. on 7/01/97 mapped with the Ozone Mapping System

Figure 34. Comparison of Ozone Values Across Maine 6/29/97-7/01/97

Figure 35. 500 mb winds for 0000Z Jul 01 1997

Figure 36. Surface Plot for 00Z 01 Jul 1997

Figure 37. 850 mb temperatures for 0000Z Jul 01 1997

Figure 38. GOES East IR Satellite for 0015Z Jul 01 1997

Figure 39. GOES East IR Satellite for 0015Z Jun 02 1997

Figure 40. KFS 24 Hour Back Trajectory for 00UTC 01 Jul 1997

Figure 41. CETL 24 Hour Back Trajectory for 00UTC 01 Jul 1997

Figure 42. BHCM 24 Hour Back Trajectory for 00UTC 01 Jul 1997

Figure 43. KFS 24 Hour Back Trajectory for 00UTC 02 Jul 1997

Figure 44. CETL 24 Hour Back Trajectory for 00UTC 02 Jul 1997

Figure 45. BHCM 24 Hour Back Trajectory for 00UTC 02 Jul 1997

Figure 46. NOx Limited or VOC Limited on 6/28/97 through 7/01/97

Figure 47. NOx Limited or VOC Limited on 6/30/97 through 7/01/97

Figure 48. Comparison of Benzene and Toluene Ratios 6/28/97 to 7/01/97

Figure 49. Comparison of m/p Xylene/Benzene Ratios 6/29/97 to 7/01/97

Figure 50. Comparison of NOy and NOx Values 6/28/97 to 7/01/97

Figure 51. Comparison of Benzene Values 6/28/97 to 7/01/97

Figure 52. Comparison of Toluene Values 6/28/97 to 7/01/97

Figure 53. Comparison of Ethylene Values 6/28/97 to 7/01/97

Figure 54. Comparison of m/p Xylene Values 6/28/97 to 7/01/97

Figure 55. Comparison of Isoprene Values 6/28/97 to 7/01/97

Figure 56. MIR for KFS on 6/30/97 and 7/01/97

Figure 57. MIR for CETL on 6/30/97 and 7/01/97

Figure 58. MIR for BHCM on 6/30/97 and 7/01/97

Figure 59. Scotia Prince Yarmouth to Portland 6/30/97

Figure 60. Scotia Prince Portland to Yarmouth 6/30/97 to 7/01/97

Figure 61. Scotia Prince Yarmouth to Portland 7/01/97

Figure 62. Scotia Prince Portland to Yarmouth 7/01/97 to 7/02/97

Appendix: 1997 Ozone Exceedance Days Summary for Maine

The author of this paper would like to recognize the efforts of the following people contributing to this paper:

The staff of the Field Services Division of the State of Maine Bureau of Air Quality, Alan VanArsdale of US EPA Region I Lexington Laboratory, Lexington. Mass., Paul Sanborn and Jim Archer of the New Hampshire Department of Environmental Services, Rich Poirot of the Vermont Department of Environmental Conservation, NARSTO (the North American Research Study on Tropospheric Ozone), and the NARSTO forecasting team.

Sagabiel et al. Real-World Emissions and calculated Reactivities of Organic Species From Motor Vehicles. Atmospheric Environment Vol 30, No. 12 pp 2287-2296.

F.C. Fehsenfeld et al. 1993. North Atlantic Regional Experiment summer intensive: Forward (Paper 96JD03629)

Ray and Michaelsen et al. 1995. North Atlantic Regional Experiment. Surface level measurements of ozone and precursor at coastal and offshore locations in the Gulf of Maine (Paper 96JD02010)

Poirot, R.L., and C. Michaelsen. 1996. Toward a more efficient transboundary exchange of air quality data. Paper presented at Air Quality Conference - Clean Air in the Northeast held on April 30-May 1, 1996 in St. John, New Brunswick.

NESCAUM (Northeast States for Coordinated Air Use Management). 1993. 1992 regional ozone concentrations in the northeastern United States. R. Poirot, ed. Boston, MA.

NESCAUM 1994. Preview of 1994 Ozone Precursor Concentrations in the Northeastern U.S. August, 1995.

NESCAUM 1997. Miller, Amar and Tatsutani. The Long-Range Transport of Ozone and Its Precursors in the Eastern United States. February, 1997

OTAG (Ozone Transport Assessment Group). Executive Report 1997. This document is OTAG's final report to USEPA summarizing the impacts of transported ozone.

Henry, R.C., C.W. Lewis, J.F. Collins. 1994. Vehicle-related hydrocarbon source compositions from ambient data: the GRACE/SAFER method. Environ. Sci. Technol. 28:823-832.

Sillman, Sanford. April, 1997. Review Article: The Relation between Ozone, NOx and Hydrocarbons in Urban and Polluted Rural Environments. Submitted to J. Geophys. Res. (Special session, Middle Tennessee Ozone Study)

Main, Roberts, and Korc of Sonoma Technology. October 1996. PAMS Data Analysis Workshop: Illustrating the Use of PAMS Data to Support Ozone Control Programs. Presented at EPA Region I Headquarters Boston, MA.

Roberts, J.M. 1990. Review Article: The Atmospheric Chemistry of Organic Nitrates. Atmospheric Environment Vol. 24A, No. 2, pp. 243-287.

Summers, P.W. 1997. Long-Range Transport of Ground-Level Ozone and Its Precursors: Assessment of Methods to Qualtify Transboundary Transport Within the Northeastern United States and Eastern Canada. Commission for Environmental Cooperation / A Report prepared by the Secretariat of the Commission for Environmental Cooperation

(based on data available as of September 29, 1997)

(based on data available as of September 29, 1997)

1. CASTNet sites operated by EPA, difficult to poll with our equipment. May be revised slightly upward in final

report.

* For informational purposes only; not included in state or federal days/hours summaries

(based on data available as of September 29, 1997)

* For informational purposes only; not included in state or federal days/hours summaries

(based on data available as of September 29, 1997)

* For informational purposes only; not included in state or federal days/hours summaries

(based on data available as of September 29, 1997)

* For informational purposes only; not included in state or federal days/hours summaries

(based on data available as of September 29, 1997)