NTN Lab Methods
At the Central Analytical Laboratory (CAL), the concentrations of the important inorganic chemicals in precipitation
are analyzed. These chemicals or analytes include acidity (measured as pH),
sulfate, nitrate, ammonium, chloride, and base cations.
The data are checked to ensure their quality, and special codes are applied to
help in interpreting the data. These sample validity codes indicate the quality of the
sample, for instance, whether it was collected according to standard protocols and
whether there is any sign of contamination.
After this initial data processing, the data are sent electronically to the NADP Program
Office, which performs further checks of accuracy and completeness. The entire data
record is confirmed as being consistent with standard NTN procedures and documentation.
Sophisticated data processing programs are run to detect discrepancies in the coding
of the samples validity and in the completeness of each sites data records. Any such
discrepancies are carefully screened and resolved.
Only after data verification is complete is the sample record entered into the NADP
database, ready for distribution to the public and inclusion in NADP publications.