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The Environmental Protection Agency’s (EPA) Clean Air Status and Trends Network
(CASTNet) was started in 1991 as a continuation and expansion of the National Dry Deposition
Network (NDDN). NDDN began in 1987 with the goal of collecting air quality, meteorological,
and land use data in order to estimate dry deposition across the eastern United States. By the end
of 1989, 56 sites were operational of which 41 are still on line. At present, the network consists
of 77 dry deposition monitoring sites with excellent coverage in the eastern continental United
States, good coverage in the western continental United States, and single sites in Alaska,
Hawaii, and the Virgin Islands. The National Park Service (NPS), who joined CASTNet in
1994, operates 27 sites, primarily in the west. EPA operates the remaining sites along with 8
visibility sites. Harding ESE is responsible for operation of the EPA component of the network.
Harding ESE is also responsible for the collection, validation, archival, and delivery of all data
(including NPS data) to EPA. Harding ESE runs the Multi-Layer Model (MLM) to simulate
deposition velocities and dry deposition fluxes. The CASTNet database contains more than 20
million records and includes data from the past fourteen years. The database can be divided into
primarily three categories: continuous meteorological data, filter pack concentrations, and dry
deposition calculations. The continuous data set consists of hourly average values for standard
meteorological parameters. The continuous database also includes hourly ozone concentrations
and hourly average rates of flow though the CASTNet three-stage filter pack. Filter pack
concentrations, maintained in units of micrograms per cubic meter, are calculated by combining
analyte weights, in micrograms, with the aggregated flow volume, in meters cubed, for the
weekly runtime of the sample. Finally, the MLM is used to simulate hourly and weekly average
deposition velocities in centimeters per second. The deposition velocities are combined with
concentrations to model estimates of dry deposition, in kilograms per hectare. The historical
database is archived primarily by the EPA Clean Air Markets Division (formerly the Acid Rain
Division). The EPA database currently is administered in MySQL but is undergoing a transition
to ORACLE. The working database, also containing all historical data, is archived at Harding
ESE. The Harding ESE databases are currently maintained in SQL Server 7.0. Future plans for
the CASTNet database include the development of an improved web based delivery system and
local replication of the historical database at Harding ESE.
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CNumber:
ACE 2001 ORLANDO, FLORIDA
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Publication Type:
Proceedings
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Publication Date:
June 2001
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