History and sources of co-occurring pesticides in an abstraction well unravelled by age distributions of depth specific groundwater samples

Environmental Science & Technology
By: , and 

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Abstract

When groundwater-based drinking water supply becomes contaminated, the timing and source of contamination are obvious questions. However, contaminants often have diffuse sources and different contaminants may have different sources even in a single groundwater well, making these questions complicated to answer. Age dating of groundwater has been used to reconstruct contaminant travel times to wells; however, critics have highlighted that groundwater flow is often complex with mixing of groundwater of different ages. In drinking water wells, where water is typically abstracted from a large depth interval, such mixing is even more problematic. We present a way to overcome some of the obstacles in identifying the source and age of contaminants in drinking water wells by combining depth-specific sampling with age tracer modeling, particle tracking simulations, geological characterization, and contaminant properties. This multitool approach was applied to a drinking water well, where bentazon and dichlorprop contamination was found to have different pollutant sources and release histories, even though both pesticides can be associated with the same land use. Bentazon was derived from recent application to a golf course, while dichlorprop was derived from agricultural use more than 30 years ago. The advantages, limitations, and pitfalls of the proposed course of action are then further discussed.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title History and sources of co-occurring pesticides in an abstraction well unravelled by age distributions of depth specific groundwater samples
Series title Environmental Science & Technology
DOI 10.1021/acs.est.9b03996
Volume 54
Issue 1
Year Published 2020
Language English
Publisher American Chemical Society
Contributing office(s) California Water Science Center
Description 8 p.
First page 158
Last page 165
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