Early warning system for tracking groundwater contamination
LBL says that long-term monitoring, however, could be costly over time for large contaminations. What’s more, current long-term monitoring strategies do not consider how abrupt or gradual changes in weather, such as heavy rain events, might influence plume behaviors. This aspect is particularly important when considering persistent plumes, such as those associated with metal or radionuclide contamination.
The new approach starts with sensors to track water quality variables that have been determined to be reliable indicators of contaminant levels. For the purposes of this study, the researchers tracked levels of tritium and uranium-238 in the groundwater at the Savannah River Site, a former nuclear weapons production site in South Carolina managed by the DOE.
For this site, they measured the acidity (or pH) levels and specific conductance (a measure of electrical conductance); these variables were determined to be reliable indicators for tritium and uranium-238 concentrations. The data from the multiple sensors were then fed into a Kalman filter to estimate contaminant concentrations. A Kalman filter is not a physical filter but rather a mathematical algorithm that can integrate mixed time-series data to make estimates. It is commonly used in various fields, such as traffic prediction and remote sensing.
Using historical data from the Savannah River Site, the researchers found that their technique provided reliable information about plume behavior over the last 20 years, indicating that the new approach holds significant promise as a long-term monitoring strategy for rapidly assessing a contaminant’s plume stability. Another advantage over conventional approaches is that it can reduce the frequency of manual groundwater sampling and lab analysis, and thus reduce the monitoring cost.
Wainwright, who is an expert in groundwater contamination and environmental data analytics, said this methodology can be used for both surface and underground water. It can also potentially be used to track other metals, radionuclides, and organic compounds commonly found in groundwater, such as arsenic, chromium, and fuels.
“There are so many different types of sensors available now, and sensor networking and rapid statistical analysis is straightforward,” she said. “We can put together all types of in situ sensors and estimate the target contaminant concentration using this framework for data integration in real-time.”
She added: “Improved monitoring techniques are essential to protect public health and the ecology. People feel safe if it’s properly monitored. Our technique is a way to monitor such sustainable remediation – effectively and cheaply.”
The study was funded by DOE’s Office of Environmental Management and Office of Science. The other co-authors of the study are Franziska Schmidt of UC Berkeley, Boris Faybishenko of Berkeley Lab, Miles Denham of Panoramic Environmental Consulting, and Carol Eddy-Dilek of Savannah River National Laboratory. The advances build upon concepts developed through the Office of Science’s Watershed Scientific Focus Area project.
Read more in Franziska Schmidt et al.,“In Situ Monitoring of Groundwater Contamination Using the Kalman Filter,” Environmental Science & Technology (22 June 2018) (DOI: 10.1021/acs.est.8b00017)
