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NADP/NTN Data Validation Coding and Use of Site History: Comparison of Utilizing Analyte Concentration vs. Analyte Deposition
Barbara Suever*, Jane Rothert and Tom Bergerhouse
Illinois State Water Survey, NADP/CAL
2004 Griffith Drive, Champaign, IL 61820
| The National Atmospheric Deposition Program/National
Trends Network (NADP/NTN) is committed to providing high-quality, consistent
data to researchers and other data users. One of our responsibilities
is to ensure that contaminated samples have been thoroughly screened for
anomalous chemistry. The NADP/NTN compares the concentration of analytes
of incoming contaminated samples with the historical concentration of
analytes for that site to determine if outliers occur. The program used
to determine the historical concentrations for a site includes chemistry
from all wet-type samples without noticeable contamination from the start-up
of that site. Each chemistry value is then assigned a score based on its
position within the distribution of that particular site’s historical
concentrations. If the score is =4, a Screening Level (SL) code of “C”
is assigned and that particular sample will be labeled as having anomalous
chemistry or is considered to be contaminated. This is done to ensure
that the chemistry from grossly contaminated samples is not used by researchers
or other data users.
We have seen, over time, an ever-expanding distribution of chemistry data. This may result in a decrease of the frequency of SL coding with “C” and allow some samples that should be labeled as having anomalous chemistry pass through undetected. We hypothesized that utilizing the deposition of each analyte for site history, instead of concentration, would limit the expansion of the distributions and more accurately assign SL coding. Results from this study are presented in this poster with recommendations for future directions in regards to historical concentration usage.
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