A Perspective on the Development of Novel In Situ Remediation of Contaminated Sediments Using Black Carbon

The field of contaminated sediment remediation was disrupted two decades ago by the emergence of a new way to reduce risk in situ through the amendment of black carbon sorbents─activated carbon and specialized biochars. This required a paradigm shift from a focus on reducing pollutant mass to reducing exposure through bioavailability control. Sorbent amendment technology has advanced from laboratory and pilot field demonstrations to full-scale applications at many sites and has recently been incorporated in USEPA records of decision at Superfund sites. This perspective summarizes critical points in advancing the new technology: 1) accurate problem definition recognizing that sediment pollutant mass reduction does not necessarily lead to risk reduction, 2) breakthroughs in bioavailability science and unraveling the role of native black carbon in sediments, 3) demonstration of pollutant bioavailability reduction with strong sorption, 4) quantitative descriptions of the process, 5) addressing the challenges of mercury, 6) understanding unintended consequences, and 7) development of freely dissolved concentrations as a key bioavailability metric with regulatory and stakeholder engagement. The lessons learned in this journey from early science through technological maturity can help inform other technologies that are in development to address evolving threats to the environment.