Background:
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 is 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.
QA/QC Issues:
QA/QC
Documentation:
(Some
documents are Adobe PDF format and will require Adobe Acrobat Reader)
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Quality Management and Quality Assurance (QA)
Plans:
Operations Manuals :
Archived Documents :
External Programs:
-
USGS Precipitation Chemistry Quality Assurance Project -
The USGS Acid Rain Quality Assurance Project uses 5 distinct programs to
document and improve the networks data quality from the point of sample
collection through electronic data storage. These include: 1) Intersite
Comparison Program, 2) Sample Handling Evaluation (formerly the
Blind-Audit Program), 3) Interlaboratory Comparison Program, 4) Field
Audit Program, and 5) Collocated Sampler Program.
- U.S.
EPA - Site Visitation
Program
Other
QA Information:
For
further QA information contact:
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