AIRMoN Dry Data Summaries

The data presented in the links below represent the best estimates currently available from the AIRMoN-dry network. They are made available with a strong recommendation for caution in their use. The science of dry deposition continues to evolve. The data presented here are expected to be modified as more is learned about the processes that control dry deposition.

Dry deposition rates are computed in the AIRMoN network by combining estimates of site-specific and time-evolving deposition velocities with measurements of air concentrations obtained using a weekly sampling protocol. The intent has been to mirror the 0900 Tuesday sample change standards adopted by the National Atmospheric Deposition Program. At times, the AIRMoN dry samples are obtained over substantially different periods, because of operator absence or problems with instrumentation. The data summaries have been arranged so that each sequential week is represented, even though some of the initial data represent periods longer than a single week.

The AIRMoN concentration sampler is a three-element filterpack, with a leading teflon filter to remove particles, a middle nylon filter to extract nitric acid vapor, and a final doped cellulose filter intended primarily to sample sulfur dioxide. An inlet tube is used to impose a small amount of heat on the incoming air stream, to protect against liquid formation on the filters in periods of high humidities. There is no doubt that this influences the measurement of ammonium nitrate. In practice, any temperature change imposed on collected ammonium nitrate particles will cause some change in the sample, so that any long-term accumulative measurement of related species (such as that reported here) will be susceptible to error because of the effects of the diurnal cycle in air temperature. Tests of the AIRMoN sampling system indicate that particulate ammonium nitrate deposited on the teflon filter is incompletely disassociated with minor consequences on the measurement of nitric acid vapor and of sulfur dioxide, but with major influence on the measurement of nitrate on the doped cellulose filter. For this reason, measurements of nitrate reported here are considered to be unreliable.

It should also be noted that tests indicate that the values associated with nitric acid vapor are underestimates, on the average by 25%. The values listed should be increased accordingly, to correct for this error (due to deposition on the walls of the inlet tube).

Deposition velocities tabulated here are derived using a multi-layer numerical model, driven by field observations of selected key variables (such as wind speed, the standard deviation of the wind direction, surface wetness, incident solar radiation, temperature, humidity, plant species distribution, etc.) It is estimated that these deposition velocities might be in error by as much as 30%.

Weekly average deposition rates are computed as the product of the weekly average deposition velocities and the weekly average concentration, thus omitting consideration of a correlation term that can be significant when air concentrations display a consistent and significant diurnal cycle.

Access the Data

The data are available here as Lotus Spreadsheet files with the AIRMoN sites identified as follows:

ANL Argonne National Laboratory, Argonne, IL - FTP the data

BND Bondville, IL - FTP the data

BUR Proctor Maple Research Center, near Burlington, VT - FTP the data

HUN Huntington Forest, NY - FTP the data

HOW Howland, ME - FTP the data

LDM Lost Dutchman State Park, NM

OKR Oak Ridge, TN - FTP the data

PAN Panola State Park, GA - FTP the data

PAW Pawnee Grasslands, CO - FTP the data

PSU Pennsylvania State University, State College, PA - FTP the data

SEQ Sequoia, CA - FTP the data

WFM Whiteface Mountain, NY - FTP the data

WPT West Point, NY - FTP the data

WYE Wye, MD - FTP the data

BBH