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.