National Atmospheric Deposition Program/National Trends Network (NADP/NTN): Precipitation Chemistry Database

Precipitation pH and conductance are measured prior to shipment ("field pH") and again at the CAL ("lab pH"). The samples are then filtered and measurements are made at the CAL for the following ions: hydrogen (H or pH), ammonium (NH4), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), sulfate (SO4), nitrate (NO3), chloride (Cl), orthophosphate (PO4), and specific conductance. Conductance and pH are analyzed by electrometric methods; NH4 is measured by automated colorimetry; Ca, Mg, Na, and K are measured by atomic absorption spectroscopy; and SO4, NO3, Cl, and PO4 are measured by ion chromatography.

All chemical measurements are quality assured by the CAL. All NADP/NTN data are stored at the NADP/NTN Coordination Office and are available on the World-Wide Web at: "nadp.sws.uiuc.edu/" Data products available from that office include: Annual Data Summaries - printed reports that include annual statistical summaries, annual isopleth maps, seasonal summaries, and weekly ion concentrations and precipitation amounts.

These reports include data for all sites in operation. Precipitation-weighted mean concentrations in milligrams/liter (mg/L) or microequivalents/liter (ueq/L) for annual, seasonal and monthly summary periods. Deposition totals in kiligrams/hectare (kg/ha) for annual and seasonal summary periods.

Weekly data consisting of ion concentrations in mg/L and precipitation amounts for individual weekly samples. Data are available 6 months following the date of sample collection. Data products listed above, except Annual Data Summaries, are available in electronic form (diskettes, magnetic tape, Internet) for all sites or a subset of sites in the network.

All are available in printed form for a subset of sites and/or time periods. Also available are bibliographies listing publications which: a) describe network design, operating procedures, data quality, and assessments thereof; b) report network data, or c) cite, in peer-reviewed journals and books, NADP/NTN data or the procedures and protocols of the network. The NADP has expanded its sampling to include the Mercury Deposition Network (MDN) ("nadp.sws.uiuc.edu/mdn/") and the Atmospheric Integrated Research Monitoring Network (AIRMoN) ("nadp.sws.uiuc.edu/airmon/")