U.S. Geological Survey Precipitation Chemistry Quality Assurance Project Data 2019 – 2020

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) NTN Interlaboratory-comparison, (2) MDN Interlaboratory-comparison program, (3) NTN Field-Audit program, and (4) MDN System-Blank program. Measured parameters include precipitation depth, pH, specific conductance, and ion concentrations for calcium, magnesium, sodium, potassium, ammonium, chloride, bromide, nitrate, sulfate, phosphate, and total mercury.