Preview of 1994 Ozone Precursor Concentrations in the Norteastern U.S.
The Photochemical Assessment Monitoring Stations (PAMS) program is required by the Clean Air Act Amendments of 1990 (CAAA) in ozone non-attainment areas of the United States that are designated serious, severe, or extreme. This network of enhanced ozone monitoring stations must be deployed by 1998. The PAMS program is an EPA-sponsored, technology-forcing initiative. Unlike previous ozone monitoring networks, the PAMS measurements include volatile organic compounds (VOCs) and inorganic ozone precursors. This necessitates the use of sophisticated field instruments capable of "simultaneously" measuring more than sixty atmospheric pollutants, mostly VOCs, on an hourly basis.
In general, each PAMs network is composed of four different kinds of sites (Type 1 through Type 4). Type 1 sites measure ozone and its precursors upwind of major metropolitan areas located within each ozone non-attainment area. Type 2 sites measure ozone and its precursors within or immediately downwind of the metropolitan area, and are optimally located to characterize the maximum precursor emissions that emanate from the metropolitan area. These sites also operate on a more intensive schedule and measure a larger array of ozone precursors than other PAMS sites. Type 3 sites are located downwind of the metropolitan areas, in regions of maximum ozone production. Further downwind are the Type 4 sites, which are intended to help characterize transport.
The PAMS program was born out of the frustration of scientists, regulators and policy makers who were unable to reconcile VOC precursor emissions controls with reductions in ozone. VOC emissions controls have been the cornerstone of the overall ozone precursor control program for the last twenty years. On paper, substantial reductions in VOCs have occurred over this time period. These reductions have come from a variety of strategies, including: chemical changes in motor vehicle fuels, reduction or elimination of certain solvents used in industrial activities, technological controls on emissions from major industrial facilities (chemical manufacturing, refineries, plastics manufacturing, coating and processing), reduction in evaporative emissions from fuel storage and marketing activities, on-board motor vehicle emissions controls, and reformulation of household and industrial products. Together these controls significantly reduced the potential emissions of VOCs; they did not, however, "solve" the ozone problem.
Many of the VOC emission reductions have been eroded by increased production of goods and services and by a continuing increase in motor vehicle use. VOC emissions from "unregulated" sources, including biogenics, are increasingly recognized as important ozone precursors (and are possibly increasing as a result of human activities). Nitrogen oxide emissions have remained relatively constant over the past few decades, and have increased in some regions. Overall results of these historical emissions changes are unclear, as no comprehensive, long-term measurements were conducted during the 1970's or 1980's to track effects of VOC emissions reductions on ambient concentrations of ozone or its photochemical precursors.
Since the Clean Air Act of 1970 and the subsequent CAA of 1979, the scientific basis for developing ozone control strategies has grown exponentially. The scientific paradigm of ozone production is more complex now than ten or twenty-five years ago. The current focus is on the role of nitrogen compounds in enhancing ozone production, the importance of biogenic emissions, incremental reactivities of VOCs and other organic compounds, and the refinement of elaborate multi-dimensional computer simulations of ozone production. Within the past five years, it has become apparent that measuring atmospheric changes in ozone precursors is as important as modeling ozone changes caused by ozone precursor control strategies. This point was emphasized in the NRC report to Congress, Rethinking the Ozone Problem In Urban and Regional Air Pollution.1 This document emphasized what steps were necessary to significantly increase the effectiveness of future ozone control programs. One of the principal recommendations was to establish a comprehensive enhanced ozone monitoring program that would measure ambient concentrations of ozone precursors, including nitrogen compounds and secondary reactive components of photochemistry. The NRC argued that the enhanced ozone monitoring program should be able to track long and short-term changes in ozone precursors caused by changes in emissions and meteorology. It also recommended that the network provide relevant information to support mesoscale modeling of ozone, and verify emissions inventories.
In the Northeast, non-attainment areas lie adjacent to each other, along the eastern seaboard. The proximal nature of these non-attainment areas, and frequent ozone and ozone precursor transport across non-attainment areas, provide an opportunity to optimize the overall NESCAUM Region PAMS network and link it with upwind PAMS sites in other regions. It is anticipated that the multi-state PAMS network will eventually contain as many as 24 sites in the NESCAUM (New England, New York, New Jersey) region. The locations of PAMS sites proposed or operating as of 1995 are displayed in Figure 2.1.
Figure 2.1 1995 Photochemical Assesment Monitoring Stations in the NESCAUM Region
Over the past several years, the northeast states have developed overall network plans, and begun deployment of the PAMS network for each non-attainment area. In 1994, seven PAMS sites were operating in the NESCAUM region. These sites included: Cape Elizabeth, ME; Lynn, MA; Chicopee, MA; East Providence, RI; Stafford Springs, CT; East Hartford, CT; and the Botanical Gardens, NY. Four additional sites (Kittery, ME; Newbury, MA; Quabbin Summit/Ware, MA; Rider College, NJ) were in advanced stages of planning or installation during 1994 and should be operational in 1995 (see Figure 2.1). The final integrated PAMS network in the Northeast is expected to be completed by 1997.
Detailed ambient pollutant and meteorological measurements are currently conducted or planned for these Northeastern PAMS sites. More than fifty hydrocarbon (C2-C10) compounds, along with ozone (O3), nitrogen oxides (NO, NO2, NOx) are measured continuously during the summer (one hour measurements from June though August). Carbonyl measurements are taken at 3-hour sampling intervals at Type 2 sites. Surface (10 meter) meteorological measurements include: wind speed, wind direction, air temperature, humidity, barometric pressure, solar radiation, UV radiation and precipitation (optional). A network of upper air meteorological stations is also required within the PAMS program. During 1994, two `upper air' sites - on the Connecticut coast, and in north central New Jersey - were in the late planning or early deployment stages. Both of these sites were initiated as public-private partnerships involving state, federal, private and academic collaboration. Additional upper air meteorological stations are anticipated in 1996.
Measurements at PAMS sites vary slightly. Siting criteria for similar types of PAMS sites are subject to different interpretations by different states and EPA Regions. Not all sites measure the same components. For instance, only Type 2 (maximum emissions density) PAMS sites measure carbonyls - which are generally measured on a 3-hour basis. Measurement frequencies can vary depending on the size of the non-attainment area. Most of the Northeast PAMS sites measure hydrocarbons on an hourly basis, but some sites take three hour composite samples. Measurement methods and data screening procedures also vary from site to site. These differences among the PAMS sites add considerable complexity to the task of PAMS data assessment. At the same time, the process of data assessment can provide valuable feedback for improving the existing regional network configuration of sites and measurements.
In 1993, NESCAUM, EPA Region I and OAQPS co-sponsored development of the AIRS/Voyager Data Delivery System (DDS).2 The DDS system, which provides an option for extracting AIRS air quality data in a format compatible with the PC-based Voyager data exploration software, is accessible to all AIRS users via the NCC/EPA mainframe computer. The Voyager Software (freeware) is available from CAPITA
- via Internet anonymous ftp (ftp capita.wustl.edu - under /pub/utilities directory) or,
- via Internet Mosaic (http://capita.wustl.edu - under "SoftwareUtilities").
NESCAUM and OAQPS currently sponsor a CAPITA project to enhance the Voyager and DDS systems to facilitate extraction and analysis of PAMS data. This (PAVLOVS) project includes 3 major elements:
- Modifications to AIRS/Voyager DDS to allow extraction of PAMS data in Voyager format,
- Modifications to Voyager Software applications to facilitate manipulation and analysis of PAMS data,
- Preparation and storage of prepared data sets of PAMS and related Air Quality data, and Voyager data analysis tools on the CAPITA Internet FTP Server.
When this report was initiated, few NESCAUM States had mastered the difficult task of submitting PAMS data to AIRS. The primary data set employed here (pams794g.voy) includes PAMS data for two 3-day July, 1994 episodes for 6 sites in New England (Figure 2.1: sites 2, 3, 6, 10, 12, 16). Earlier versions of this data (pams794a-f.voy) were gathered, processed and compiled in Voyager format by CT DEP staff. During data analysis, several erroneous data values were identified and eliminated from the current data set. Other related NE regional data sets for July 1994 (ozone, NOx, CO, met., etc.), were extracted with the AIRS/Voyager DDS. Other Voyager data files, including all US 1993 PAMS data from AIRS (prepared by CAPITA), 1990 Atlanta study data (prepared by CAPITA) and 1993 California PAMS data (prepared by CARB) are incorporated in various sections of the report (see Figure 2.2).
Figure 2.2 Locations of PAMS Sites with Data Employed in this Report(Available via Internet)
Data from the (NESCAUM region) NY Botanical Gardens and Ryder University, NJ sites during the selected episode periods have more recently become available in spreadsheet format (NY data are reviewed separately in Section 8).
All of these data sets are posted on the CAPITA ftp server (under /pub/PAMS directory) as follows:
File Name Size Description
pams794g.voy 342,404 PAMS data from 6 NE sites for 7/6,7,8/94 and 7/20,21,22/94
neoz794.voy 317,922 Ozone data from all NE States for month of 7/94
nenox794.voy 385,767 NO, NO2 and NOX data from all NE States for month of 7/94
newsd794.voy 271,682 Wind Speed and Direction data from all NE States for month of 7/94
neco794.voy 147,210 CO data from all NE States for month of 7/94
pams93vy.zip 818,433 Voyfile of all 93 US PAMS data in AIRS as of 1/1/95 (from CAPITA)
atlanta.zip 407,778 Voyfile of O3, NOx, VOC, Met data from Atlanta, 1990 (from CAPITA)
sum93voy.zip 185,216 Voyfile of California PAMS data for Summer, 1993 (from CARB)
nypams94.zip 280,282 NY Botanical Gardens PAMS data (WK1 format) for Summer, 1994
njjuly94.xls 28,672 NJ Ryder U. PAMS data (XLS format) for 7/7/94 and 7/22/94
Several Voyager data manipulation Scripts used in this report are also available from the CAPITA server:
File Name Size Description
diurcyc1.scp 4,228 calculates diurnal averages, with options for screens, ratios, etc.
arrow.scp 1,458 creates arrow vectors from wind speed and direction data in Map view
houragg.scp 3,574 calculates daily max. or averages for selected hours in Time view
avgtrend.scp 1,218 calculates average values for multiple sites in Time view
scat1.scp 486 identifies individual sites in a multi-site Scatter view
movav.scp 637 calculates moving averages in a Time view
