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National Trends Network

Sponsoring Organization:  National Atmospheric Deposition Program

Acronym:  NTN

Description:  The NTN is the only network providing a long-term record of precipitation chemistry across the United States. Sites predominantly are located away from urban areas and point sources of pollution. Each site has a precipitation chemistry collector and gage. The automated collector ensures that the sample is exposed only during precipitation (wet-only-sampling). Site operators follow standard operational procedures to help ensure NTN data comparability and representativeness. They collect samples weekly on Tuesday morning, using only containers cleaned at the Central Analytical Laboratory (CAL) at the Illinois State Water Survey (ISWS). They weigh the collection bucket to determine sample volume and transfer the sample from the collection bucket to a shipping bottle. All samples are sent to the CAL for analysis, and data entry, verification, and screening.

Web Site:  http://nadp.sws.uiuc.edu/ntn/

Duration:  01/01/1978 to present  (as of 08/29/2012)

Program Contact:  Matt Layden

Program Contact Email:  ntn@isws.illinois.edu

Program Contact Web URL:  http://nadp.sws.uiuc.edu/NTN/contacts.aspx

Data Access Web URL:  http://nadp.sws.uiuc.edu/data/ntndata.aspx

Data Access Policy:  Data and information presented on this website (http://nadp.sws.uiuc.edu/) are in the public domain, unless otherwise indicated. Some images and graphics on this website have been created by other organizations and are used by the NADP with permission. Under copyright law, if you want to use images or graphics used by the NADP with permission, you first need to obtain the permission of the copyright holder.

Data Access Policy Web URL:  http://nadp.sws.uiuc.edu/nadp/useConditions.aspx

Sampling Frequency:  Weekly

Sample Collection:  Site operators follow standard operational procedures to help ensure NTN data comparability and representativeness. Site operators collect samples weekly on Tuesday morning, using only containers cleaned at the Central Analytical Laboratory (CAL) at the Illinois State Water Survey (ISWS). They weigh the collection bucket to determine sample volume and transfer the sample from the collection bucket to a shipping bottle. All samples are sent to the CAL for analysis, and data entry, verification, and screening

Quality Assurance Plan:  The CAL reviews field and laboratory data for completeness and accuracy, and flags samples that were mishandled, compromised by precipitation collector failures, or grossly contaminated. The CAL delivers all data and information to the NADP Program Office, which applies a final set of checks and resolves remaining discrepancies. Data then are made available on the NADP Web site.

Parameters Measured:  The CAL measures free acidity (H+ as pH), conductance, calcium (Ca2+), magnesium (Mg2+ ), sodium (Na+ ), potassium (K+ ), sulfate (SO42-), nitrate (NO3+ ), chloride (Cl- ), and ammonium (NH4+). The CAL also measures orthophosphate, but only for quality assurance as an indicator of sample contamination.

Monitoring Stations:  50 stations are registered in the database (search/display)

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