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APPENDIX G - DATA QUALITY INDICATORS
Environment Canada
Paul Horvatin Keith Puckett Quality Indicators (DQIs) are statements of data quality commonly used to express measurement uncertainty as precision, accuracy, representativeness, completeness, and comparability. DQIs in IADN are based on what is achievable through the current state of the art and serve as specifications of the quality of the data, however that quality determination is made. The IADN measurement data consists of determinations of the concentration of various toxic chemicals in both air and precipitation. The primary use of the measured concentration data will be to determine the deposition of the toxic chemicals to the Great Lakes in terms of seasonal and annual averages. Deposition estimates are to be derived from the concentration measurements through the use of certain loading equations (see Section 1.3). These loading equations make use of additional parameters and constants (such as deposition velocity and Henry's Law constant) that have additional uncertainties associated with them. Participants of the 1992 workshop that reviewed initial drafts of the first QAPP agreed that for IADN to meet its program goals, the deposition of certain chemicals would need to be determined with an uncertainty of roughly 30 percent. They also agreed that the current state of knowledge and measurement art is such that it is not possible to determine the deposition of many of these chemicals to better than within a factor of two. These same participants also agreed that determining the concentration of specific compounds is subject to an uncertainty of roughly 50 percent for many of the chemicals of interest. Most of the uncertainty in deposition estimates arises from uncertainties in the terms and parameters used in the loading equations. |
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