The goal of this project was to reduce mercury levels in fish in the South River through contaminated soil removal and capping approaches. Both approaches included adding a mixture of biochar and sand within a geocell when capping the contaminated soil remains. Biochar was used for these applications because it has the ability to absorb mercury and bind it into place, reducing or eliminating the amount of mercury-contaminated soil that could be eroded and deposited into the South River.
In Virginia, the scenic South River and South Fork Shenandoah River, stretching from Waynesboro for 125 miles downstream to Front Royal, are tainted with the shadows of mercury contamination. A significant contributor to this environmental concern was a former DuPont facility in Waynesboro, which discarded mercury waste from 1929 to 1950. The aftermath has been so detrimental that regulatory actions are predominantly focusing on the health threat posed to individuals consuming mercury-tainted fish from these streams.
Michael Liberati, DuPont's project director, is steering the charge in implementing biochar as a part of the remediation process. Biochar, a special kind of hardwood treated at low temperatures until it becomes similar to charcoal, has shown significant promise in immobilizing mercury. By excavating regions with high mercury pollution and backfilling them with biochar, the approach aims not only to extract the bulk of the mercury but also to effectively contain any residual traces.
In addition to the use of biochar, the project emphasizes the importance of replanting native vegetation along the riverbanks. This strategy enhances the riverbank ecosystem and also acts as a safeguard against potential future mercury leaching.
However, the application of biochar and the larger remediation initiative are part of a more extensive research and response framework. Regular sampling of fish by the VADEQ has revealed alarming mercury concentrations. For instance, in 2002, smallmouth bass had mercury levels peaking at 4 ppm, way above the state-mandated maximum of 0.5 ppm. Such findings led the Virginia Department of Health to issue a fish consumption advisory for the affected rivers.
The US Environmental Protection Agency (EPA) has mandated Virginia to draft action plans for cleaning its polluted streams, with the TMDL study serving as a foundational blueprint for cleaning the South River and South Fork Shenandoah River. As part of this holistic effort, the Virginia DEQ conducts annual fish samplings and had scheduled a comprehensive sediment survey for 2007.
Additionally, DuPont, in its bid to understand and address the issue, sponsors extensive mercury studies via the South River Science Team (SRST), which includes professionals from government agencies, academic institutions, environmental non-profit organizations, and DuPont itself. This collaborative team meets regularly, sharing scientific insights and strategizing future research. SRST is currently spearheading studies into mercury's presence in diverse environmental components, from water to wildlife.
In 2005, furthering their commitment, DuPont entered an agreement with environmental organizations to conduct a six-year ecosystem research of the South River watershed, aiming for a holistic understanding of the mercury issue.
The primary goal of the South River Mercury TMDL study is to comprehend methyl mercury's behavior in the South River and discern mercury reduction techniques that will safeguard the fish. As part of this approach, continuous monitoring stations, managed by the VDEQ and the USGS, have been set up at key locations. These stations will periodically measure mercury and related water-quality parameters for a duration of two years.
This multi-faceted approach, blending biochar usage with expansive research and collaboration, might well be the roadmap for other regions grappling with similar environmental challenges.
In batch tests containing biochar and river water spiked with mercury, total mercury concentrations decreased and percent mercury removal increased. Initially a 50/50 mix of biochar/soil was used, and then reduced to 15% by weight due to a use of a new source of biochar.
Fact Sheet: https://southriverwatershed.org/wp-content/uploads/2018/08/FactSheet-NO8-4-25-17.pdf
Mercury Remediation of the South River, Virginia Report: https://biochar-us.org/sites/default/files/presentations/Mercury%20Remediation_Liberati.pdf
