IMPROVE Data Quality
Reported Uncertainty and MDL
Each reported concentration is accompanied by its calculated uncertainty and minimum detection limit (MDL). The procedures for calculating these values are described in the IMPROVE Data Processing and Validation SOP #351, Section 5.3. When downloading IMPROVE data from the VIEWS website, check "Uncertainty" and "Min. Detection Limit" in the "Fields" tab if you would like to receive these values along with the concentration data.
Beginning in 2003 IMPROVE began collocated measurements at selected sites (see the Feature Article). A fifth sampling module was added to provide an overall estimate of uncertainty from all sources by comparison with its pair. Data analysts at UC Davis are refining procedures that will allow these collocated data to be used to estimate the uncertainty in the reported concentrations. When downloading IMPROVE data from the VIEWS website IMPROVE Data Access, check "POC" in the "Fields" tab to receive an indicator of a collocated module. Collocated data are designated as POC=2.
Data advisories are archived on the VIEWS website to document interesting findings from the IMPROVE database including data anomalies, potential problems, and new uses for the IMPROVE data. Many of these data advisories have been written by IMPROVE staff at UC Davis to describe changes or anomalies that we have encountered.
XRF QA Reports
UC Davis submits a quarterly report documenting the quality of the x-ray fluorescence (XRF) data submitted for each quarter. These reports summarize the quality assurance performed during and after elemental analysis of three months of IMPROVE samples . The elemental analyses include the determination of most elements with atomic numbers from 11 to 40 (Na-Zr) and 82 (Pb) with two energy dispersive X-ray fluorescence systems (XRF), and the determination of hydrogen by Proton Elastic Scattering Analysis (PESA) with the Crocker cyclotron. The following data assessments and quality controls are obtained for all analyses: Concentration calibration and verification; Energy calibration; Laboratory replicates (reanalysis); Systems comparisons and field blanks.