Solid-phase arsenic speciation in aquifer sediments: A micro-X-ray absorption spectroscopy approach for quantifying trace-level speciation

Arsenic (As) is a geogenic contaminant affecting groundwater in geologically diverse systems globally. Arsenic release from aquifer sediments to groundwater is favored when biogeochemical conditions, especially oxidation-reduction (redox) potential, in aquifers fluctuate. The specific objective of this research is to identify the solid-phase sources and geochemical mechanisms of release of As in aquifers of the Des Moines Lobe glacial advance. The overarching concept is that conditions present at the aquifer-aquitard interfaces promote a suite of geochemical reactions leading to mineral alteration and release of As to groundwater. A microprobe X-ray absorption spectroscopy (μXAS) approach is developed and applied to rotosonic drill core samples to identify the solid-phase speciation of As in aquifer, aquitard, and aquifer-aquitard interface sediments. This approach addresses the low solid-phase As concentrations, as well as the fine-scale physical and chemical heterogeneity of the sediments. The spectroscopy data are analyzed using novel cosine-distance and correlation-distance hierarchical clustering for Fe 1s and As 1s μXAS datasets. The solid-phase Fe and As speciation is then interpreted using sediment and well-water chemical data to propose solid-phase As reservoirs and release mechanisms. The results confirm that in two of the three locations studied, the glacial sediment forming the aquitard is the source of As to the aquifer sediments. The results are consistent with three different As release mechanisms: (1) desorption from Fe (oxyhydr)oxides, (2) reductive dissolution of Fe (oxyhydr)oxides, and (3) oxidative dissolution of Fe sulfides. The findings confirm that glacial sediments at the interface between aquifer and aquitard are geochemically active zones for As. The diversity of As release mechanisms is consistent with the geographic heterogeneity observed in the distribution of elevated-As wells

Räume des Erinnerns und Vergessens bei Wolfgang Hilbig. Erinnerungskonstellationen im Hilbigschen Werk

Hilbig’s self-reflexive literary landscapes constitute a rich tapestry of personal reminiscence and cultural memory. Via readings of Hilbig’s post-Wende retro texts I explore facets of memory loss, a central concern in his largely autofictional writings. Throughout his oeuvre Hilbig thematicises memory loss as a process occurring on several planes, for example, as a psychological and existential phenomenon (selective amnesia), as a neurological condition facilitated by bouts of drinking, or as an abandonment of ecological consciousness . At the same time, the preservation of cultural memory is problematised by virtue of its associations with the GDR’s ideological and semantic (re)interpretation or whitewashing of the recent past. It will be shown how Hilbig’s aesthetic reappropriation/reworking of literary romanticisms and modernisms represents an act of inner ‘resistance’ to the State’s distortion or realignment of cultural and intellectual tradition. To the extent that for Hilbig lapses of memory are equally bound up with poetics, namely with the creative writing process itself, two narrative texts in particular, Die Kunde von den Bäumen (1992) and his confessional ‘artist’ novel Das Provisorium (2000), focus on the dialectic of remembering and forgetting as an integral part of the aporia of linguistic and literary representation in a postmodern age of commodified culture. Das Provisorium also presents the author as a postmodern flaneur, as a culturally dislocated and deracinated voyeur no longer able to claim custodianship of a collective cultural identity