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The Quest for Average Water
Citation:
Sayre, R., M. Serre, Woodrow Setzer, AND J. Wambaugh. The Quest for Average Water. Univ of NC Chapel Hill Dept. of Environmental Sciences and Engineering In-House Seminar, Virtual, N/A, February 17, 2021. https://doi.org/10.23645/epacomptox.19115906
Impact/Purpose:
Presentation to the UNC Dept. of Environmental Sciences and Engineering and Gillings School of Public Health In-House Seminar February 2021. This presentation describes the state of work supporting the ecological SEEM surface water chemical concentration forecasting tool.
Description:
Under ideal circumstances, any time someone wished to know the concentration of a given organic chemical in water, they could take a sample and analyze it. However, you’ve probably experienced that this is no trivial task. Imagine if you needed to know the concentrations of thousands of chemicals for waters across the United States! This project presents a method for estimating representative surface water concentrations across many chemicals, using mechanistic environmental fate models calibrated with samples taken by U.S. EPA, USGS, the states, and other groups over the last twenty years. Since these samples were collected for many purposes, the first step was to decide how to filter and clean the data to the subset that is most useful for this task. One of the most critical challenges in this dataset is how to incorporate measurements described as non-detects – more than 70% of all samples! In this presentation you will learn about a couple methods for incorporating measurements below a detection limit into a range of values. Once the methods have been described, you’ll see whether different methods influence risk rankings based on the comparison of the resulting representative concentrations with each chemical’s toxicity to standard freshwater species. Finally, I’ll demonstrate that even under these conditions of high uncertainty, a signal strong enough to be useful can be detected. Learning objectives: 1) What is a representative concentration, and when is it useful? 2) How may you calculate a representative concentration when some measurements are below a detection limit? 3) Are representative concentrations incorporating different types of below-limit values, or calculated using different methods of handling below-limit values, different enough to influence risk decisions? This abstract does not necessarily represent the views or policies of the U.S. Environmental Protection Agency.
URLs/Downloads:
DOI: The Quest for Average Water
SAYRE_SEMINAR_10NOV2020_V2_M.PDF (PDF, NA pp, 1201.614 KB, about PDF)