Goldschmidt 2019

Goldschmidt 2019
Dates: 18 – 23 August 2018
Location: Barcelona

For further information: https://goldschmidt.info/2019/

Abstract submission deadline: 29 March 2019

GEOTRACES sessions:

10c: Arctic and sub-Arctic Processes: Understanding Changing Ocean Circulation and Biogeochemistry

Conveners: Núria Casacuberta, Michael Karcher, John Smith, Lauren Kipp, Christian März, Robyn Tuerena

Research in the context of GEOTRACES and beyond has shown the value of using chemical tracers in seawater for documenting and understanding transient ocean processes. Tracer applications in ocean models have provided significant additional insights into physical oceanography and fostered the improvement of ocean models. Natural and anthropogenic tracers such as radionuclides, gas tracers, oxygen isotopes, DOM, etc. can facilitate a better understanding of circulation and mixing in high latitude regimes. With a focus on the Arctic Ocean and its adjacent seas we invite contributions dealing with chemical tracers as tools for investigations on the circulation within and exchanges between the Arctic and sub-Arctic Seas, including the northern Atlantic and Pacific oceans. We encourage contributions on large-scale processes occurring over annual to decadal time scales, that provide insight into dispersion pathways in the Arctic and sub-Arctic seas and tele-connections between Arctic circulation and the Meridional Overturning Circulation via the Arctic Loop Current. We especially encourage contributions combining modelling with tracer measurements. Questions to be addressed may include: • What can be learned about circulation and modification of water masses in the northern oceans based on tracer observations and modelling? • What are the elements of water mass dispersion that appear to be stable over timescales of years to decades, and which are changing? • What are the governing physics and bio-geochemistry factors? • What are the most promising new tracers for the Arctic domain? • How can collaboration between observational tracer science and modelling be improved?

10j: Biogeochemical Cycles of Low Oxygen Zones and their Response to Ocean Deoxygenation

Conveners: Nicole Bale, Darci Rush, Ruifang Xie, Tim Conway, Insa Rapp, Laura Bristow

Keynote: Caroline Slomp (Utrecht University)

Observations in the past decades have confirmed steadily declining dissolved oxygen concentrations in the subsurface oceans including coastal systems (coastal hypoxia) and open ocean oxygen minimum zones. Future expansion and spread of oxygen deficient zones in the ocean is predicted as a consequence of climate change, and will result in major changes to marine biogeochemical cycles. These changes will impact sources and sinks of nitrogen, phosphorus, sulfur and redox-sensitive trace metals in the oceans, with global effects on the biota that utilize these elements. This session seeks to bring together geochemical, biological and physical scientists working on present and past low-oxygen environments, in order to gain an integrated view of biogeochemistry in these systems. We thus invite submissions of field, experimental and modelling studies focusing on major nutrients, trace elements, dissolved gases, microbial ecology, molecular biomarkers, productivity and physical drivers in these systems. We encourage submissions focusing on (1) the distribution, isotopic composition, and speciation of macro- (e.g., N, P, S, Si) and micronutrients (e.g., Fe, Zn, Cd, Ni, Cu) across the entire oxic-anoxic transition both in the modern ocean and the geologic past such as oceanic anoxic events, (2) assessment of the marine sources and sinks of these elements from low-oxygen environments, (3) N2O and CH4 production and emissions in low-oxygen systems, and (4) the impacts of chemical and physical change on productivity and microbial pathways. Regional or global interpretations based on earth system models or large chemical datasets from programs such as GEOTRACES are especially encouraged.

10k: Trace Metal Cycling and Radioisotope Tracers of Ocean Biogeochemistry (GEOTRACES)

Conveners: Aridane G. González, Hannah Whitby, Amber Annett, Emilie Le Roy

This session will highlight recent advances in marine trace element chemistry and the use of radionuclides as tracers in the marine system. In particular, we focus on the speciation and ligand-binding reactions of trace metals, and investigation of both micro- and macro-nutrient cycles and fluxes using natural and anthropogenic radionuclides. The GEOTRACES program, which aims to map the world’s oceans for trace elements and their isotopes with unprecedented resolution, has facilitated rapid progress in these research areas. Radioisotopes are becoming increasingly powerful tracers for studying the biogeochemical cycles of carbon, nutrients, trace elements and isotopes in the world’s oceans. These tracers can be naturally-occurring or anthropogenic, with a wide range of half-lives allowing their application to a broad array of processes. Methodological advances and standardization (e.g. through GEOTRACES and RiO5) are contributing to increasing spatial coverage and temporal resolution of data of many marine radioisotopes. In order to understand the processes behind trace metal fluxes and export, we must also understand the physico-chemical interactions and organic speciation of trace metals, which play an important role in their biogeochemical cycling. The GEOTRACES effort has vastly increased the database of metal-binding organic ligand distributions, demonstrating key features and distinct regional trends. However the identification of these ligands, as well as their effect on the redox reactions and bioavailability of trace metals in natural waters, are still largely unconfirmed. In this session, we invite observational, experimental and modelling contributions on the distribution and characterization of organic ligands in the ocean, as well as their effect on the redox reactions of metals in seawater. In tandem, this session brings together studies using radionuclides to investigate aspects of marine biogeochemistry from local to global scale: fluxes and export of particulate material, sources and sinks of macro- and micro-nutrients, elemental cycles at ocean margins (e.g. estuaries, sediments, hydrothermal vents, air-sea interface), or rates of biological processes (e.g. biological export and remineralisation). Studies presenting advances in methodology, novel applications of radionuclide tracers, or using radioisotopes to quantify human impacts on ocean biogeochemistry are also welcome.

08m: Wally Broecker: A Scientific Celebration of a Life in Geochemistry

Conveners: Sidney Hemming, Edouard Bard, Sigurdur Gislason, Roberta L. Rudnick

Wally Broecker was a towering figure in geochemistry. His research themes that spanned many sub-fields of modern geochemistry, notably radiocarbon dating (the topic of his Ph.D. thesis), chemical oceanography and atmospheric chemistry and their changes through time. He developed methods for dating and tracing processes in the Earth system and applied them to various natural archives such as sediments from the deep-sea and from lakes on land, fossil corals from tropical islands, speleothems from caves and varnish deposits from deserts. This allowed him to address myriad research questions, including testing the orbital theory; determining paleo-hydroclimate in drylands and documenting abrupt climate change that involved coupling between atmosphere and ice-sheets dynamics and the general circulation of the global ocean.
Wally became intensely interested in, and worried about, the fate of anthropogenic CO2 in the atmosphere, ocean and biosphere and its consequences such as greenhouse warming and ocean acidification. He was among the first scientists to warn us about the negative aspect of global warming and pleaded for engineering solutions to capture and sequester fossil fuel CO2.
Over his long and exceptional career, Wally always had a powerful and positive influence on a large number of students, post-docs, collaborators and fellow scientists working in other institutions on all continents. This session is in honor of Wally’s legacy and in the spirit of his wide-ranging interests and generosity.

Includes the GEOTRACES talk:

GEOTRACES: Inspired by GEOSECS to Investigate Trace Elements and their Isotopes in the Ocean
Anderson R, Francois R, Frank M, Henderson G, Jeandel C & Sharma M
https://goldschmidt.info/2019/abstracts/abstractView?id=2019002892
Wednesday 21 August 2019, 10h15

GEOTRACES-related sessions:

08f: The Role of Carbon in Regulating Climate States: Lessons from Earth’s Past

Conveners: Kate Littler, Gerhard Kuhn, Norbert Frank, Thomas Chalk, William Gray

Keynotes: Jessica Tierney (University of Arizona), Robert (Bob) Anderson (LDEO – Columbia Univ.)

This session aims to bring together scientists from the proxy and model communities that study all aspects of past cold and warm states of the Earth’s climate system. We welcome model or proxy studies of biogeochemical cycles and climate change that bring new evidence to light of the concentration and movement of carbon between atmosphere, biosphere, oceans, and sediments and its role in regulating the climate states. This is because Earth’s climate is strongly forced by the concentration of CO2 in the atmosphere on a number of different timescales and climate models rely on accurate information from carbon reservoirs to reconstruct our past and predict our future climate states. Therefore, this session aims to gather work on reconstructing CO2 and/or its movements between reservoirs to narrow down on the primary mechanisms of climate change on geological timescales, as well as divining our near future through past evidence of glacial CO2 changes, long-term CO2 drawdown and release, and major climate transitions. Submissions interrogating the nature of orbital scale climate variability from any period are strongly encouraged as well as those looking at modern processes of carbon regulation and uptake.

10a: Silicate Alteration in Ocean Sediments and Synthetic Glasses: Process, Consequence, and Kinetics

Conveners: Wei-Li Hong, Jianghui Du, Isabelle Muller, David A McKeown

Keynote: Catherine Jeandel

Reverse weathering and alteration of silicate mineral-glass under low temperature is of fundamental importance in the source and sink of various elements, planetary climate, carbon cycling, and considerations for long-term nuclear waste glass storage. Silicate glass stability is of concern to many scientific studies: basaltic glasses in geochemical systems, nuclear waste glasses in their final repository, and weathering of industrial or cultural heritage glass objects. These processes have been studied through field observations as well as by laboratory experiments. For example, reverse weathering is known to acidify solution through the neo-formation of clay minerals, which constitutes significant sinks for trace elements and alkalinity in the ocean and sediments. Weathering of marine silicate minerals, on the other hand, has been shown to buffer solution pH and promote the precipitation of authigenic carbonates by increasing alkalinity and the release of cations. The interaction of silicate glass and water has been investigated by laboratory leach tests that range from days to over 30 years. These leach studies have identified smectites concomitant with long-term glass stability at low leach rates, as well as the common occurrence of rapid acceleration of glass alteration associated with zeolite formation at high temperatures or high ratios of glass surface area to leachant volume. Outstanding issues concerning silicate alteration that will be addressed in this session include: the impact on benthic fluxes of various elements in the ocean; the effect on the global elemental cycle and planetary climate; how the strength of these processes vary with time and space; the factors governing the formation of aluminosilicate minerals (such as zeolites and smectites), the associated kinetics during glass alteration and its modeling. The two keynote speakers will share their insights on how submarine weathering of lithogenic material affects benthic fluxes of macro- & micro-nutrients (Dr. Catherine Jeandel from LEGOS), and macroscopic to atomic scale silicate glass alteration (Dr. Stéphane Gin from CEA).

10h: The Oceanic Particle Flux and its Cycling within the Deep Water Column

Conveners: Maureen Conte, Rut Pedrosa Pamies, Phoebe Lam, Henry Ruhl

The oceanic particle flux plays a major role in global elemental cycles, the ocean uptake of carbon dioxide, and the transfer of energy and matter to the deep ocean and sediments. The particle flux and its composition represent a dynamic balance between biological processes that generate large sinking particles in the upper ocean and particle cycling processes within the ocean interior that consume, modify and produce new sinking particles, including biologically-driven organic matter remineralization, particle aggregation/disaggregation, chemical scavenging, and authigenic mineral precipitation. New observational platforms, sampling methods and advances in chemical and molecular techniques (e.g., metabolomics, metagenomics, transcriptomics) allowing for expanded particle characterization are providing novel insights on particle flux transformations within the deep water column, including the depth evolution of particle-associated microbial communities and the scavenging of dissolved and suspended materials associated with biological reprocessing of flux materials. Synthesis and modeling studies are providing increased understanding of linkages between ecosystem structure and global patterns in surface export and flux transfer efficiency to the deep ocean. This multidisciplinary session will bring together scientists under research themes related to geochemistry, biology, oceanography, modeling and climatology to present the current status of our understanding of processes controlling the magnitude and composition of the oceanic particle flux, its attenuation and transformation with depth, and its coupling with associated biogeochemical cycles. Session presentations will describe novel findings and syntheses which, in turn, will highlight key knowledge gaps in the particle flux and its role in geochemical cycles.

12a: Hydrobiogeochemical Processes at the Sediment-Water Interface: Wetlands, River Corridors and Coastal Zones

Conveners: Dipankar Dwivedi, Xingyuan Chen, Joseph Tamborski, Valentí Rodellas, Edward O’Loughlin, Yamin Deng, Virginie Sanial

Keynote: Christof Meile (University of Georgia)

Terrestrial-aquatic and surface-groundwater interfaces are transitional zones that play a vital role in controlling the exchange of water and chemical constituents between land and water systems. In terrestrial-aquatic interfaces (e.g., wetlands and lagoons) the movement of water and the biogeochemically catalyzed transformations of its constituents determine the mobility of nutrients and contaminants, the emission of greenhouse gasses into the atmosphere, carbon (C) cycling and sequestration in subsurface environments, and the quality of water itself. Likewise, groundwater-surface water interactions (e.g. hyporheic and porewater exchange, terrestrial and submarine groundwater discharge) have long been recognized as an important component of the hydrological cycle and an essential pathway for the transfer of material (e.g. nutrients, metals, C, and contaminants) to surface water bodies (e.g. coastal ocean, streams, lakes, lagoons, and wetlands). This session brings together studies focusing on hydrobiogeochemical exchanges occurring at terrestrial-aquatic and surface-groundwater interfaces, and their impacts on freshwater and marine systems. We particularly welcome new contributions addressing i) geomorphological and hydrobiogeochemical processes (including redox dynamics and transformations of C, nutrients, metals, and contaminants) occurring in wetland environments (sediments, rhizosphere, and water), coastal aquifers, submarine groundwater discharge zones, and hyporheic zones; ii) modeling of ecosystem processes; iii) the challenges of bridging across scales (e.g., molecular to landscape; regional to global-scale). Method-based contributions which address iv) omics and bioinformatics approaches for identifying microbial interactions, and v) new methodologies and the combination of approaches to trace groundwater-surface water interactions and associated forcing mechanisms, are also welcomed.

13f: Trace Elements Speciation: Novel Methodologies and Insights into Transformations Influencing their Global Biogeochemical Cycle

Conveners: Sylvain Bouchet, Adrien Mestrot

Many trace elements (TE) can be toxic (e.g., As, Hg, Sb) and/or essential (e.g., Cu, I, Se) for humans, plants and wildlife. Some also play important roles in atmospheric processes, e.g., S, I and Br. To understand the biogeochemical cycle and effects of TE, it is crucial not only to quantify them in environmental and biological compartments, but also to determine their speciation. This entails the distribution of TE between specific chemical forms in term of electronic or oxidation state, molecular structure or complexes formed with various ligands. Indeed, the partitioning, transport, bioavailability, bioaccumulation and toxic or beneficial effects of TE largely depend on their speciation. The goal of this session is to highlight recent advances (1) in methodologies, using elemental, molecular and/or spectroscopic techniques, allowing the identification and/or quantification of TE species (2) in our mechanistic understanding of the biotic and/or abiotic transformations affecting TE species (e.g., alkylation/dealkylation, oxidation/reduction, colloid formation and sorption/desorption) and (3) in assessing fluxes of TE among aquatic, terrestrial and atmospheric (eco)systems. Contributions to the session may include fundamental and applied research based on laboratory work, field experiments and/or modeling approaches. Studies looking at the potential effects of on-going and future global changes, such as climate change and eutrophication, on the fate of TE and their species are also strongly encouraged.

13e: Radionuclides in the Environment: Modeling, Experimental, Scaling, Controlling Chemical/Microbial/Hydrological Processes

Conveners: Peter H. Santschi, Daniel Kaplan

Since the onset of the Manhattan project, fluxes of anthropogenic radionuclides through the environment increased. This has resulted in increased concentrations of a number of anthropogenic radionuclides in the various environmental reservoirs. Consequently, there is a growing need to understand and predict the consequences of increased fluxes of anthropogenic radionuclide, in relation to those of natural radionuclides. At the same time, the input of both anthropogenic and natural radionuclides can provide us, due to their radioactive decay, with the ability to get insights into time and spatial scales of key chemical/microbial/hydrological processes. The objective of this session is increased understanding of biogeochemical processes that control radionuclide cycling and their consequences in natural and anthropogenic systems. The emphasis is on modeling, experimental, scaling, controlling chemical/microbial/hydrological processes. Themes can include: 1) Radionuclide speciation in aquatic, terrestrial and atmospheric compartments, including particulate and colloidal phases, and the role biological processes play in determining radionuclide mobility, oxidation state and degree of organic complexation/chelation. 2) Radionuclides in environments that provide sinks of radionuclides in the geosphere, including wetlands, lake sediments and soils. 3) Controlling chemical/microbial/hydrological processes, including dissolution from primary mineral or organic phases, sorption and incorporation into secondary phases.