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Regional PAMS Assessment

The 1990 Amendments to the Clean Air Act provided for the establishment of PAMS (Photochemical Assessment Monitoring Station) sites in all ozone nonattainment areas designated as serious, severe, or extreme. The PAMS network is composed of four different types of sites: upwind locations relative to designated nonattainment areas (Type 1), locations representing maximum precursor concentrations in nonattainment areas (Type 2), locations of maximum ozone concentrations (Type 3) and locations further downwind (Type 4). This array of differing locations is intended to provide insight into ozone formation and transport mechanisms with the recognition that these are complex, non-linear processes strongly dependant on ambient concentrations of precursor species as well as local emissions and meteorology.

State and local air pollution control agencies operate the PAMS sites. The PAMS networks typically monitor 56 target hydrocarbons and 2 carbonyl compounds, ozone, oxides of nitrogen (NOx and/or NOy), and meteorological measurements. Sample speciation may vary among sites as some agencies report more hydrocarbons and/or carbonyl compounds than the PAMS target list. Differences among analytical techniques also can alter the list (e.g., co-eluters).

The sampling frequency also varies among regions, states, and sites in the PAMS program. For example, hydrocarbons are sampled on a 1-hr or 3-hr average basis; may or may not cover a 24-hr period; and are collected every day, every third day, or on an episodic basis. Carbonyl compounds are typically collected as 3-hr averages every third day but other sampling variations exist. Most sites take surface meteorological measurements, including wind speed, wind direction, and temperature reported hourly. PAMS program upper-air meteorological measurement requirements may be met in a number of ways, including using rawinsondes, radar profilers, or twice daily National Weather Service soundings.

Since establishing the PAMS network in the NESCAUM and MARAMA region in the 1990s, insufficient data and network analysis has been undertaken to evaluate the effectiveness of the network in achieving its intended objectives (i.e. providing information on effectiveness of control strategies, emissions tracking, trends and exposure). The Northeast States have conducted a series of assessment efforts in order to identify ways that the PAMS network could more efficiently meet program objectives, as well as to provide analysts with a quality assured, validated data archive to assist in future analysis efforts. Details of these assessment efforts can be found by following these links:


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