USGS Hydrologist Collaborates with Danish Scientists on Groundwater Research

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Groundwater provides much of the world's drinking water. When a supply of groundwater becomes contaminated, determining the timing and source of the contamination is an obvious concern. But the answers aren’t always clear. Contaminants may have different sources, even in a single groundwater well.

depth-specific sampling illustration

This illustration shows how depth-specific sampling was used to detect the source and history of pesticide contamination in a supply well in Denmark.

A team of international scientists led by the Geological Survey of Denmark and Greenland worked with California Water Science Center Research Hydrologist, Bryant Jurgens, to study the source of bentazon and 1,2-dibromo-3-chloropropane (DBCP) contamination in a supply well near Løkken, Denmark. These pesticides have been banned (DBCP) or restricted (bentazon) by the Danish government so the timing and source of these contaminants in this well can help evaluate the efficacy of pesticide regulations.

The team combined depth-specific sampling, age tracer modeling, particle tracking simulations, geological characterization, and contaminant properties to show that DBCP entered the well with deeper, older, agriculturally-derived groundwater, while bentazon entered the well with younger, shallow groundwater from an adjacent golf course.  These results indicate that restrictions of bentazon and DBCP use for agricultural purposes have largely been effective.

map of study area

The image on the left shows the relative position of the drinking water well and additional wells installed during this study at the Løkken site. The aerial photo on the right shows the landscape around the drinking water well. The outer boundaries of the golf course are marked with a red line. The outer boundaries of the particle tracking simulation results are marked with a blue line The red dot on the inserted map of Denmark shows the location of the Løkken site.

Mr. Jurgens involvement in the project was voluntary, done with sponsorship from the USGS National Water-Quality Assessment (NAWQA) program. Results from this project have recently been published in the journal, Environmental Science & Technology.

Read the full article:  History and Sources of Co-Occurring Pesticides in an Abstraction Well Unraveled by Age Distributions of Depth-Specific Groundwater Samples.