Analysis of VOC Data

To help assess the contribution of various pollutants to the formation of ozone air pollution, the U.S. Environmental Protection Agency (EPA) initiated the Photochemical Assessment Monitoring Stations (PAMS) program for serious, severe, and extreme ozone nonattainment areas. PAMS stations monitor for volatile organic compounds (VOCs), ozone, oxides of nitrogen (NOx), and meteorological parameters.

In January 1998 the MARAMA Board authorized a project to analyze regional PAMS data and produce a report on the importance of mobile sources in the Mid-Atlantic Region. MARAMA contracted with Sonoma Technology, Inc. and E.H. Pechan Associates to prepare a series of related reports.

In 2000-2001 MARAMA collaborated with NESCAUM on a larger analysis of PAMS data.

The following briefly summarize the reports available on this website and provides a link to the NESCAUM website.  Except for the website, all the reports are in Adobe Acrobat® format.

NESCAUM & MARAMA PAMS Assessment Project (2000-2001)

A program of data validation and analysis was carried out between September 2000 and June 2001 by Sonoma Technology, Inc. (STI). This analysis was aimed at identifying potential modifications or revisions of the current network that would result in both increased efficiency and overall usefulness of the program.

Reconciliation of an Emissions Inventory with PAMS Ambient Monitoring Data in the Mid-Atlantic Region- May 2000, Till Stoeckenius and Michele Jimenez, ENVIRON International Corporation.

Comparisons were made between emissions inventories and ambient air quality data for ratios of ozone precursor species using data for two PAMS monitoring sites, in Baltimore and Washington, DC. Morning (6 – 9 am) TNMHC:NOx ratios in the ambient samples were found to be greater on average than corresponding emission ratios. This discrepancy could be due either to some combination of systematic under estimation of morning VOC emissions and overestimation of morning NOx emissions or to the influence of uncertainty in spatial and temporal disaggregation in the inventory or to errors in speciation of HC emissions or to factors affecting the monitoring data.

Characteristics of Volatile Organic Compounds in the Mid-Atlantic RegionCharacteristics of Volatile Organic Compounds in the Mid-Atlantic Region, November 1999, H. Main, S. Hurwitt, P. Roberts, Sonoma Technology, Inc.

Analysis of 1997 data showed that motor vehicles were the dominate source of VOCs at the PAMS sites, although some sites were significantly affected by other sources. Morning NMHC/NOx ratios for all PAMS sites in the Mid-Atlantic region in 1997 generally were VOC-limited indicating that VOC controls may be effective in reducing ozone levels.

The report identifies all PAMS sites as "VOC limited." Mid-Atlantic PAMS sites in general are located in or downwind of major metropolitan areas. Combustion sources, including both motor vehicles and other fuel burning in metropolitan areas, are a rich source of NOx emissions. Because NOx emissions are high in urban areas, the amount of ozone produced may be limited by the availability of VOCs. This finding should be confirmed using other data analysis techniques before being used to influence control strategy selection. The report includes recommendations for further analysis.

Validation of PAMS VOC Data in the Mid-Atlantic Region, February 1999, H. Main and P. Roberts, Sonoma Technology, Inc.

An extensive data validation effort was undertaken for 12 sites for 1996 and 1997 data. The observations are quantitatively and qualitatively reviewed for accuracy, completeness, and internal consistency. The MARAMA member agencies made a concerted and commendable effort to address data quality issues, revise problem data, and resubmit the revised data to AIRS. As a result of these efforts, the data for the Mid-Atlantic region are of good quality.