S83: Frontiers in the biogeochemistry of acid mine drainage and acidic pit lakes

Conveners:	Christian Blodau	(Christian.Blodau@uni-bayreuth.de)
	Danielle Fortin	(dfortin@science.uottawa.ca)
Keynote:	Kirk Nordstrom	(Boulder)

Acid mine drainage (AMD) is an often pervasive consequence of mineral and coal extraction. The generation of highly mineralized and often acidic waters, their fate in watersheds and their impact on discharging waters are the result of complex and coupled geochemical, microbiological, and hydrological processes. While many individual processes involved in AMD are understood in principle, their interaction on different temporal and spatial scales is poorly understood. This interdisciplinary session invites contributions dealing with the rates, controls, and modeling of microbial, chemical, and hydrological processes involved in acid mine drainage and the geochemical dynamics of pit lakes generated from mining activities. Of particular interest are contributions addressing (I) critical bacteria-mineral-solution interactions, (II) secondary mineral formation and transformations, (III) the movement and fate of acidity in the subsurface and on the watershed scale, and (IV) the longevity of AMD generation and the biogeochemical system dynamics of acidic pit lakes.

S84: Radiogeochemical aspects of nuclear waste disposal

Conveners:	Dirk Bosbach	(dirk.bosbach@ine.fzk.de)
	Lara Duro	(lduro@enviros.biz)
Keynote:	Horst Geckeis	(Karlruhe)

The disposal of nuclear waste in geological formations poses major scientific and social challenges to be met in the next decades. One of the key issues is related to the long term safety of a waste repository system over extended periods of time (up to 1 mio. years). Demonstrating the safety over such geologic time scales requires a sound understanding of the migration and retention of radionuclides in the geosphere. In recent years it has been demonstrated that understanding fundamental reactions on a molecular level can improve the reliability of geochemically based long-term predictions. The session is intended to bring together experts from various fields related to radio-geo-chemical aspects of nuclear waste disposal with special focus on the long-term safety. It will cover fundamental aspects as well as applied issues related to nuclear waste disposal. This includes waste forms, the geochemical evolution of the waste matrix (near-field processes), migration of key radionuclides in the geosphere (far-field processes) as well as natural analogues.

S85: Geochemical records of recent environmental change in sediment systems

Conveners:	Andy Cundy	(A.Cundy@brighton.ac.uk)
	Kevin Taylor	(K.G.Taylor@mmu.ac.uk)
Keynote:	John Farmer	(Edinburgh)

This session is focussed on the use of geochemical records, contained in peats, coastal sediments, lake sediments, and other sediment systems, in examining Late Holocene environmental change. Contributions are invited on geochemical records of both natural (e.g., recent sea-level change, climatic rhythms) and anthropogenic (e.g., atmospheric and aquatic contamination, mining and industrial / urban development) change, including the use of isotope proxies, and the combination of geochemistry with other indicators of environmental change (e.g., pollen, diatom records etc).

S86: Natural and anthropogenic particulate matter in the atmosphere: Mineralogy, isotope geochemistry, environment, health

Conveners:	Martin Ebert	(mebert@geo.tu-darmstadt.de)
	Reto Gieré	(giere@uni-freiburg.de)
	Peter Stille	(pstille@illite.u-strasbg.fr)
Keynote:	Peter Brimblecombe	(Norwich)
	Bernard Grobéty	(Fribourg, Switzerland)

The proposed session aims to present recent developments in characterizing particulate matter (PM) in the troposphere. Such information is important to assess the interaction between aerosol particles (PM10, PM2.5, PM1 or ultrafine particle fraction) and atmospheric gases, water, body fluids, or plants, and thus the environmental and health impacts of PM. In order to identify anthropogenic impacts of e.g. trace heavy metals or soot it is also necessary to characterize the naturally occurring particulates (e.g., from volcanic eruptions, continental erosion, forest and coal fires, sea spray). We invite mineralogical, geochemical and isotopic contributions, which address problems related to the impacts of particulates on environment and human health. Of special interest are topics such as, single-particle characterization (composition, structure, size, morphology); isotopic tracing of anthropogenic sources (e.g., waste incinerators, steel and coal plants, smelters); characterization of air-filter and road dusts; deposition of PM on soils, plants, surface waters, and ice; and PM solubility and migration.

S87: Microbial mineralization: from environmental processes to new technologies

Conveners:	Terry Beveridge	(tjb@uoguelph.ca)
	Jon Lloyd	(jon.lloyd@manchester.ac.uk)
	David Vaughan	(david.vaughan@manchester.ac.uk)
Keynote:	Lynne Macaskie	(Birmingham)

The activities of micro-organisms can have a dramatic effect on geochemical processes and much can be learnt from our attempts to understand the natural systems. Increasingly, such studies are being directed towards potential applications in new technologies concerned not only with environmental cleanup but also with energy generation, industrial processing, and fabrication of new materials.

S88: Biogeochemical processes in natural acidic environments

Conveners:	Stefan Peiffer	(s.peiffer@uni-bayreuth.de)
	Leigh Sullivan	(leigh.sullivan@scu.edu.au)
Keynote:	Ed Burton	(Lismore, Australia)

Natural acidic environments such as acid sulfate soils, acidic ground waters and lakes, or acidic bog waters cover a significant fraction of the earth¥s surface. Regulation and control of element fluxes in such environments, some of which being regarded to at least partly mimic geochemical conditions potentially met on planet Mars, is, however, only poorly understood. This session shall bring together scientists from various disciplines to exchange scientific observations and concepts with respect to a generalisation of the biogeochemical processes occurring in acidic environments. In particular, the analogies and differences to environments affected by acid mine drainage shall be outlined which makes this session complementary to the session on "Frontiers in the biogeochemistry of acid mine drainage and acidic pit lakes". Contributions are welcome dealing with the rates, controls, and modelling of microbial, chemical, and hydrological processes involved in natural acidic environments.

S89: Natural radioactive isotopes as tracers in studies of environmental processes

Conveners:	Michael Schubert	(michael.schubert@ufz.de
	Jan Scholten	(J.Scholten@iaea.org)
Keynote:	Willard S. Moore	(Columbia, South Carolina)

Investigations in applied and environmental geosciences are often concerned with processes that do not allow for direct monitoring, a fact which often hampers the appropriate assessment of the given situation. For instance, a detailed investigation of groundwater migration and/or of contamination dispersion in the subsurface is often impeded by the lack of parameters permitting direct quantitative assessment of the relevant processes.

Water-soluble and/or gaseous natural radioisotopes, when used as tracers, have been shown to provide valuable information by indirectly giving insight into environmental processes and thus allowing for their comprehensive understanding. The aim of the session is to present and discuss innovative approaches that apply naturally-occurring radioisotopes as environmental tracers. Presentations on theoretical aspects relevant to the use of naturally-occurring radioisotopes as tracers as well as studies focusing on respective practical applications will be presented during the session.

S90: Trace element interactions with sulfur species in reducing environments

Conveners:	Dirk Wallschläger	(DWallsch@TrentU.ca)
	Irena Ciglenecki-Jusic	(irena@irb.hr)
	George Helz	(helz@umd.edu
Keynote:	Terry Seward	(Zü:rich)

This topic touches upon a wide range of active research in geochemistry. Examples of practical issues of current interest include understanding the mobility of arsenic in anaerobic groundwaters and inferring the redox status of ancient sedimentary environments from concentrations of such elements as Mo, Re or U in black shales. Examples of more fundamental issues include distinguishing the roles of complexes, clusters and nanoparticles in controlling the mobility and bioavailability of trace elements, developing mechanistic models of stable isotope fractionation for sulphophile metals (e.g. Fe, Cu, Zn, Mo etc.) and using new spectroscopic tools to refine understanding of trace element adsorption processes involving sulfide minerals. We anticipate including papers on new developments in analytical and computational chemistry methodologies.