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

The U.S. Geological Survey has operated the Precipitation Chemistry Quality Assurance (PCQA) Project to evaluate and document the data quality for the National Atmospheric Deposition Program (NADP) for 40 years. The PCQA is primarily focused on data quality for the NADP National Trends Network (NTN) and Mercury Deposition Network (MDN). The PCQA implements programs to evaluate the variability and bias of NADP data. The programs are described in several USGS reports: 1. See, R.B., Willoughby, T.C., and Brooks, M.H., 1990. Programs and analytical methods for the U.S. Geological Survey Acid Rain Quality Assurance Project: U.S. Geological Water-Resources Investigations Report 90-4029. 2. Latysh, N.E., and Wetherbee, G.A., 2005. External quality-assurance programs managed by the U.S. Geological Survey in support of the National Atmospheric Deposition Program/National Trends Network: U.S. Geological Survey Open-File Report 2005-1024. 3. Latysh, N.E., and Wetherbee, G.A., 2007. External Quality Assurance Programs Managed by the U.S. Geological Survey in Support of the National Atmospheric Deposition Program/Mercury Deposition Network: U.S. Geological Survey Open-file Report 2007-1170. 4. Wetherbee, G.A., and Martin, RoseAnn, 2017, Updated operational protocols for the U.S. Geological Survey Precipitation Chemistry Quality Assurance Project in support of the National Atmospheric Deposition Program: U.S. Geological Survey Open-File Report 2016-1213, 18 p., https://doi.org/10.3133/ofr20161213. Data users are referred to these reports for guidance to properly use the data. The data fields are described in data dictionaries in this data release. This data release provides the PCQA data from 1978 to 2017 for all PCQA programs. However, for the Colocated Sampler Program, only the colocated site data are provided herein because the original site data are available from the NADP web site at: http://nadp.slh.wisc.edu/NADP/networks.aspx.