Data for the U.S. Geological Survey Precipitation Chemistry Quality Assurance Project for the National Atmospheric Deposition Program, 1978–2017

The USGS Precipitation Chemistry Quality Assurance Project (PCQA) operates QA programs to challenge and test the National Atmospheric Deposition Program (NADP) data-collection processes for both the National Trends Network (NTN) and Mercury Deposition Network (MDN). PCQA data are available in separate tables for each quality-assurance program: (1) Intersite comparison for field pH and specific conductance, (2) Blind Audit for NTN, (3) Sample Handling Evaluation for NTN, (4) Interlaboratory-comparison for NTN, (5) Interlaboratory-comparison program for MDN, (6) Field-Audit program for NTN, (7) System-Blank program for MDN, (8) MDN Blind Audit program, and (9) Colocated Sampler program for NTN. Measured parameters include precipitation depth, pH, specific conductance, and ion concentrations for calcium, magnesium, sodium, potassium, ammoium, chloride, bromide, nitrate, sulfate, phosphate, and total mercury.