Quality Assurance Support for the NADP


The concentrations of dissolved substances in precipitation are generally quite low (less than 1% of NADP precipitation samples have total dissolved chemical concentrations > 20 mg/L). Chemical measurements of precipitation samples require thorough quality assurance (QA) and quality control (QC) procedures to assure that meaningful data are obtained. Biases can result from: sample handling contamination; losses to sample container walls; chemical, physical, and biological changes; and variations in collection and analytical procedures. Stringent QA and QC procedures are essential for obtaining unbiased, precise, and representative atmospheric deposition measurements and for maintaining the integrity of the sample during collection, handling, and analysis. Equally stringent procedures must be applied to data management to assure that the accuracy of the data is maintained.

QA is stressed in all aspects of NADP operations. Sites are required to meet minimum siting standards, use approved instruments, and follow standard procedures. The NADP analytical laboratories operate under well-defined QA programs with well-defined QC criteria. QA continues for processing, coding, and reporting data to the Program Office. QA procedures, however, are not static sets of rules. They are modified to accommodate program changes and in response to the experience accumulated from past practices. NADP QA programs are aimed toward providing representative data of documented bias, precision, and completeness to assist data users in evaluating the appropriateness of the data for a particular application. Specifically, it is the NADP quality management policy to accomplish the following:

  • Develop scientifically-based methodologies for data collection and assessment to provide continued quality improvement.

  • Provide quality assessments of network operations to assist network management and cooperating agencies in improving network monitoring strategies.

  • Provide estimates of completeness, precision, bias and representativeness for all spatial and temporal data values reported.

  • Provide complete and concise records of NADP policies, procedures and quality assessments.

  • Permanently associate network quality assurance documentation with reported data.

Standard Operating Procedures

QA/QC Issues:

External Programs:

Other QA Information: