Thioarsenic species associated with increased arsenic release during biostimulated subsurface sulfate reduction

Introduction of acetate into groundwater at the Rifle Integrated Field Research Challenge (Rifle, CO) has been used for biostimulation aimed at immobilizing uranium. While a promising approach for lowering groundwater-associated uranium, a concomitant increase in soluble arsenic was also observed at the site. An array of field data was analyzed to understand spatial and temporal trends in arsenic release and possible correlations to speciation, subsurface redox conditions, and biogeochemistry. Arsenic release (up to 9 μM) was strongest under sulfate reducing conditions in areas receiving the highest loadings of acetate. A mixture of thioarsenate species, primarily trithioarsenate and dithioarsenate, were found to dominate arsenic speciation (up to 80%) in wells with the highest arsenic releases; thioarsenates were absent or minor components in wells with low arsenic release. Laboratory batch incubations revealed a strong preference for the formation of multiple thioarsenic species in the presence of the reduced precursors arsenite and sulfide. Although total soluble arsenic increased during field biostimulation, the termination of sulfate reduction was accompanied by recovery of soluble arsenic to concentrations at or below prestimulation levels. Thioarsenic species can be responsible for the transient mobility of sediment-associated arsenic during sulfidogenesis and should be considered when remediation strategies are implemented in sulfate-bearing, contaminated aquifers.

Narrowing the gap between rhetoric and the reality of medical ethics

A major challenge for academic medical education is to sensibly balance the needs of students and residents for hands-on training with the rights of patients to receive the highest quality of care. Two aspects of the debate over this issue have received a great deal of attention: the appropriate degree of patient control over the makeup of the treatment team, and the proper role of supervision and accountability for attending physicians. Although the law has ostensibly resolved the conflict between the goals of student participation and the principles of patient autonomy and informed consent, the record of medical practices is too often inapposite. The divergence of law and reality is primarily a reflection of the law's flawed medical model, which poorly matches the dynamics of the physician-patient relationship and ineffectually attempts to reshape it. But the dissonance is also attributable to medicine's autonomous professional culture, which undervalues patient involvement and reinforces benign paternalism. Coherent policy requires a recrystallization of both the legal ideal and the medical reality. Lawyers and ethicists should loosen their rigid consumerist conception of medicine, and physicians should become more conscious of the infiltration of paternalism and instrumentalism into their decisions.