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

The National Atmospheric Deposition Program/National Trends Network
(NADP/NTN) is a 200-station, rural, wet-only deposition monitoring
network throughout the continental United States, Alaska, and Puerto
Rico. The NADP was established in 1978 to provide a focal point for
the development of research to address the problem of acidic chemical
deposition.

Each station follows criteria and protocols established by the
NADP/NTN. Each station uses an Aerochem Metrics wet/dry precipitation
collector to collect cumulative weekly samples of precipitation for
chemical analysis, and a Belfort 5-780 Universal recording rain gage,
equipped with an event pen, to make independent precipitation
measurements. Samples are collected weekly and sent to the Central
Analytical Laboratory (CAL) operated by the Illinois State Water
Survey at the University of Illinois. 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:

"http://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) ("http://nadp.sws.uiuc.edu/mdn/") and the Atmospheric
Integrated Research Monitoring Network (AIRMoN)
("http://nadp.sws.uiuc.edu/airmon/")