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Determining Representative National Surface Water Chemical Concentration Ranges for Risk Prioritization
Citation:
Sayre, R., Woodrow Setzer, M. Serre, AND J. Wambaugh. Determining Representative National Surface Water Chemical Concentration Ranges for Risk Prioritization. North American Lake Management Society (NALMS) Conference, Virtual, NC, April 19, 2021. https://doi.org/10.23645/epacomptox.18804626
Impact/Purpose:
Presentation to the North American Lake Management Society (NALMS) Conference April 2021. This presentation describes the state of work supporting the ecological SEEM surface water chemical concentration forecasting tool.
Description:
Thousands of chemicals can be observed in surface waters, but it is a complex task to prioritize which of those chemicals may pose a higher relative risk to freshwater aquatic environments in the United States, considering inconsistent data availability on both the hazard and exposure sides. Although thousands of measurements of organic chemical concentrations are taken across the country, they are collected for different purposes, so many aspects of the samples vary widely. This project evaluates the influence of different data curation and statistical conventions on aggregating organic surface water measurements into concentration distributions. Millions of rows of data were available in the National Water Quality Monitoring Council’s Water Quality Portal for over 1700 chemicals sampled in 2114 of 2270 hydrologic subbasins across the United States from 1999 to 2019. First, we provide an overview of the variability of surface water chemical concentrations within categories provided from the metadata such as sampling activity type, time, and location, or analytical chemistry method. These factors are not necessarily compatible; to give an example, samples measured using different analytical chemistry methods may possibly be combined if they are designed for complementary concentration ranges, however it may not be reasonable to combine them (depending on the chemical’s properties) if one is designed for bulk water and one is designed for a dissolved concentration. We explore the effect of grouping sample sets across these categories, striving to include as many samples as possible while maintaining data quality and applicability to aquatic ecotoxicity. A combination of knowledge-based judgments and statistical tests are used to make grouping decisions. Finally, we evaluate the effect of applying different parametric and nonparametric statistical methods to estimate per-chemical central tendencies and their uncertainty intervals for our chosen samples, given the left-censoring and right-skew of the data. Based on these investigations, we develop concentration variability ranges to prioritize chemicals on the basis of risk through comparison with in vivo and in silico ecotoxicity lowest-effect concentrations to identify cases where water concentrations exceed effect threshold levels. The workflow is available as a Python script for reproducibility. The views expressed are those of the authors and do not necessarily reflect the views or policies of the US EPA.
URLs/Downloads:
DOI: Determining Representative National Surface Water Chemical Concentration Ranges for Risk Prioritization
RRSAYRE_NMC2021_M.PDF (PDF, NA pp, 2522.924 KB, about PDF)