Monitored natural attenuation of arsenic:promises and pitfalls from two case studies

摘要

Monitored natural attenuation (MNA) relies on processes, such as sorption and precipitation that sequester arsenic (As) in the subsurface and thus protect downgradient receptors. It is not a simple exercise to determine whether MNA could be a viable strategy for managing As-contaminated groundwater at a specific site. On the basis of two previously-described case studies, the type of evidence that could support selection of MNA as a management option is summarized. The potential for MNA to be effective is discussed in the context of the mechanisms by which As is mobilized in the source area and sequestered away from the source area. Particular attention is paid to the assumption that persistence of As in the source area is evidence of biogeochemical control of mobilization. The situations where MNA is most likely to be effective are suggested.