Ariel David Anbar - US grants

This proposal seeks funding for continued development and application of the molybdenum stable isotope system for the examination of changes in ocean redox through time. Research into ocean paleoredox is of great importance in paleoceanographic modeling, and in the coupled modeling of changes in the biogeochemical cycles through time. At present, the integration of multiple geochemical redox indicators in organic carbon-rich sediments identifies, with reasonable certainty, sediments deposited under anoxic-sulfidic (euxinic) bottom waters. However, beyond the areal distribution of such sediments, there is no means of estimating how prevalent euxinic bottom water conditions were at any particular time.
Our initial survey of Mo isotopes in sediments from the Black Sea, ferromanganese nodules, seawater and continental materials indicated that the largest fractionation of Mo isotopes in the oceans occurs during preferential uptake of light Mo isotopes to Mn-oxyhydroxide sediments, but that Mo isotopes are relatively unfractionated during removal in euxinic environments (Barling et al., 2001). Therefore, Mo in seawater is isotopically lighter than Mo in oxic sediments and continent-derived Mo entering the oceans, but is similar to that of sediments accumulating under euxinic conditions. Because both oxic and euxinic sediments are important sinks in the ocean Mo budget, these findings led us to develop the following hypothesis: The Mo isotope composition of black shales should reflect that of seawater, and should vary with the extent of global ocean anoxia. Specifically 97Mo/95Mo (and other Mo isotope ratios) should shif toward isotopically lighter values during extended periods of expanded euxinic conditions in the oceans.
We have explored key parts of this hypothesis as part of award EAR 0106712 which supported one year of further investigation of major reservoirs, and laboratory experiments designed to test the inference that Mo isotopes are fractionated during uptake by Mn-oxyhydroxides. This award will soon expire. Results to date demonstrate that Mo isotopes are fractionated during uptake by Mn-oxyhydroxides in the laboratory, in the expected direction and to the expected magnitude. In addition, we have found that the Mo isotopic compositions of euxinic sediments from the Cariaco Basin are similar to those of Black Sea sediments and seawater, consistent with the idea that such sediments provide a first order record of seawater Mo isotopes. Recent findings of other workers (e.g., Siebert et al., 2001b) also increase confidence in the paleoredox utility of Mo isotopes
To further test this hypothesis, we now propose to extend our research to examine the isotopic composition of Mo in the geologic record. Specifically, we intend to study Mo isotopes and other paleoredox indicators in three well-constrained black shale stratigraphic sequences from the Mesoproterozoic (Roper Group, McArthur Basin, N. Australia), the Paleozoic (Middle Devonian Oatka Creek Formation, northern Appalachian Basin) and the Mesozoic (Cenomanian-Turonian Boundary core, ODP Site 1138) Eras. These three sequences are selected because they may represent periods of substantial, but differing, perturbation of ocean redox conditions for periods of time comparable to, or longer than, the ocean residence time of Mo. These sequences are also attractive because they are well characterized by other geochemical techniques and have good stratigraphic and depositional context. Preliminary data obtained from the McArthur Basin, a Devonian black shale and the C-T Boundary are consistent with our hypothesis. We also propose to refine our laboratory experiments to better understand the mechanisms of Mo isotope fractionation in nature.
The proposed research will strengthen ties between groups at U. Rochester and U. Missouri, which bring complementary approaches to paleoenvironmental questions of mutual interest. Paleoenvironmental research is of increasing societal importance as a result of public interest in probable anthropogenic climate change and its consequences. The complementary resources and approaches of these two groups will enrich the training of two graduate students, one at each institution. In addition, the proposed project facilitates the participation of a member of an underrepresented group (Co-PI Barling).

Project will integrate geological, paleobiological and geochemical examination of a freshly-collected Archean sediment drill-core that will be obtained in the summer of 2004. This continuous core, ~ 1000 m in length, will sample the last ~ 250 million years of Archean stratigraphy in the Hamersley Basin of the Pilbara Craton, Western Australia. Sampled lithologies will include basalt, carbonate, chert and several kerogenous pyritic shale units.
This proposal is possible because of an unprecedented opportunity for collaboration with the Astrobiology Drilling Program (ADP) of the NASA Astrobiology Institute. The ADP will fund acquisition of this core. The NSF funds will be used for initial characterization of core materials to include a detailed study of paleoecology and paleoenvironment in kerogenous sediments. Importantly, core recovery will be over-seen by PI Buick and is geared specifically toward the proposed research.
Intellectual Merit: The general motivation of the proposed research is to characterize the nature of life and its environment in the late Archean, shortly before the rise of atmospheric oxygen. Many workers are examining the timing of this redox transition and its relationship to contemporaneous climatic oscillations that may include global ice ages. The team's interest, somewhat different but complementary, is to understand how the Archean biosphere set the stage for this singular environmental transformation. Specifically, a major goal of this project is to characterize the relative importance of different types of microbes in late Archean marine environments and, through lithofacies relationships, to study the envi-ronmental controls on their distributions. This goal will be achieved through integrated examination of hydrocarbon molecular biomarkers, redox indicators and biogeochemical cycling in kerogenous sediments.
Clean drilling methods, immediate sampling and prompt analysis will allow us to unambiguously deter-mine if taxonomically diagnostic sterane and triterpenoid hydrocarbons are indigenous to these rocks. These compounds are abundant in existing, poorly-preserved Hamersley Basin drill core and, if not contaminants, constitute the earliest biomarkers of eukaryotes and cyanobacteria. Further, analysis of the new core should permit us to examine the relative abundances and isotopic compositions of such compounds in an environmental context, yielding information about ecological relationships. Additional goals are to characterize the status of major biogeochemical cycles in the late Archean and generate a robust baseline for future investigations by conducting sedimentological and biogeochemical reconnaissance of the entire core. Collectively, this work will test the hypothesis that oxygen-generating cyanobacteria and aerobic microorganisms were present in Archean ecosystems and that the environmental imprints of these me-tabolisms remained muted for hundreds of millions of years after their origins.
Broader Impact: There are three areas of broader impact. First, ~ 6 graduate students will participate in an unusually integrative and multi-disciplinary research project spanning six major research universities. While each will be rooted in a single aspect of the program, these students will have substantive opportunities to bridge across subdisciplines and institutions. Second, because the planned drill core will ultimately be openly available in accordance with the ADP charter, this work will provide a lithological and chemostratigraphic framework of benefit to the wider research community. Third, it is hoped that this NSF-NASA collaboration will provide a positive precedent for future efforts by other investigators that might ultimately evolve into a broader inter-agency "Deep Time Drilling Program".

Hartnett
0525569
Arid desert environments are home to a unique microbe-mineral system in which cyanobacteria and microalgae form biological soil crusts. These systems are important because they significantly impact the carbon cycle and nutrient budgets in arid regions, and because they may be representative of early terrestrial biota before the rise of land plants. Biological soil crusts exist in an environment profoundly limited by the lack of water and nutrients, especially bioessential trace metals. We hypothesize that biological soil crusts maximize their retention of water and nutrients through the production of organic compounds. The soil crust community's mediation of organic compounds and the bioessential metals in the soil provides a fundamental biogeochemical link between microbes and earth-materials. Our experimental studies focus on the interactions of soil crust microbes with mineral substrates, and the nature and effects of the organic compounds produced and/or lost to the soil porewater on metabolically relevant metals. Our specific objectives are: 1) To characterize desert soil crust and the underlying soil mineralogy and geochemistry; 2) To compare crusted and uncrusted soil systems with respect to carbon and trace element composition; 3) To simulate rain events and assess changes in biological soil crust organic carbon production and metal distributions before, during and after water exposure. Electrospray ionization tandem mass spectrometry will be used to identify specific organic compounds directly from water samples, and ICP-mass spectrometry will be used to determine trace metal concentrations and distributions. This integration of organic biogeochemistry, trace element biogeochemistry, and geomicrobiology is quite unusual and our graduate and undergraduate students will gain unique trans-disciplinary research experience.

EAR-0520648
Anbar

This proposal will fund an ICP-MS technical specialist to support innovative research in the newly renovated and equipped W.M. Keck Foundation Laboratory for Environmental Biogeochemistry at Arizona State University (ASU). The goal of this laboratory is to promote research at the intersection of the geosciences, the life sciences and chemistry by capitalizing on recent advances in mass spectrometry. The new position will therefore support the development and application of novel analytical methods. A special focus of this position will be new types of isotopic analyses made possible by the development of multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Examples of planned work include: the use of Mo isotope measurements in ancient sediments to reconstruct changes in the amount of oxygen in the atmosphere and oceans; the measurement of Fe isotopes to better understand the environmental chemistry of this biologically essential element, and exploration of Cr isotopes to trace toxic pollutants. In addition to supporting specific research projects, this award will enhance the development of a vibrant new program in isotope biogeochemistry at ASU that brings together researchers in several departments, schools, centers and institutes spanning a number of disciplines. The award will make it possible for us to effectively fold our new instruments into integrative graduate and undergraduate training as part of this program. It will also enhance the ability of ASU faculty to mentor post-Ph.D., non-tenure-track staff scientists, several of whom are involved in the planned research efforts.

ABSTRACT

OCE-0526618
OCE-0526495

Isotope fractionation during adsorption to authigenic oxide minerals is emerging as an important process for paleoproxy applications of many metals. Adsorptive isotope effects have been demonstrated for Mo and Fe, are strongly suspected for Tl, and are at least likely for Cr and Cd. Such fractionation may affect the ocean isotope budgets of these elements and also have important implications for reconstruction of metal isotope paleorecords from isotopic measurements in authigenic oxides such as marine ferromanganese crusts. To realize this potential, it is essential to quantitatively understand the controls on isotopic fractionation and focus on the experiments and theoretical calculations of the natural samples, which have not been the focus of the community's most current work.

In this study, researchers at Arizona State University and Princeton University will carry out a laboratory investigation and quantum chemical modeling to attain the following objectives: (1) quantify the magnitude of isotope fractionation of Cr, Fe, Mo, Cd and Tl during adsorption onto various manganese and iron oxides; (2) assess the sensitivity of these effects to intensive variables such as temperature, pH and salinity; and (3) elucidate the reaction mechanisms causing observed fractionations, including definitive determination of whether they arise from equilibrium isotope exchange or kinetics effects. This information is needed to assess whether these new isotopic tools can be used to understand marine geochemical cycles, reconstruct the chemical evolution of the marine environment or determine the ocean redox history.

In terms of broader impacts, the project will support not only the early career development of the Co-PI, but also the training of a graduate student, an undergraduate student, and a post-doc in state-of-the-art analytical geochemistry and theoretical chemistry. It will also enhance the infrastructure for research and education by supporting a partnership between geologists, geochemists, and chemists at four different academic institutions, including two outside the United States, who will integrate experiments, state-of-the-art analytical geochemistry and modern theoretical chemistry.

Collaborative Research Towards a Weathering System Science Consortium: Two
Workshops on Biogeochemistry of the Critical Zone


The world's soil resource is probably second only to water in terms of its importance to human society. The rates and mechanisms of processes within the soil zone have a significant impact on events throughout Earth's systems; for example, these processes contribute to nutrient cycling and neutralize acidic precipitation in watersheds. Despite the importance of the soil resource, estimates of soil formation rates are based upon unproven assumptions of steady state and vary widely. However, all estimates agree on a common point: the current estimates of soil erosion rates are one to three orders of magnitude greater than estimates of average soil formation rates, a disturbing conclusion considering the importance of soils to society.

The scientific merit of this proposal lies in addressing a clear need for a better system tracking and disseminating information regarding weathering and soil formation. Our proposed initiative will investigate the following question: How does Earth's weathering engine transform rock into soil to nourish ecosystems, shape terrestrial landscapes, and control atmospheric carbon dioxide? The answer requires coupling physical, chemical, and biological processes over a range of spatial and temporal scales and involves a variety of scientific and engineering disciplines.

Traditionally, terrestrial low-temperature geochemists and soil chemists have worked in small, single or double PI projects. Very few large, multi-PI projects that cross scales and disciplines have developed from within this community. In contrast, among other scientific communities, large programs have developed to organize scientists into coordinated multi-university teams. For example, IRIS and COSEE have been extremely successful in generating enthusiasm and interest in the seismology and oceanography communities. We propose a new paradigm, a Weathering System Science Consortium (WSSC), to forge this type of multi-PI approach to weathering science and environmental biogeochemistry among terrestrial low-temperature geochemists and soil chemists/biologists.

To lay the groundwork for the proposed WSSC, we are requesting funding for two workshops, a symposium at the 18th World Congress of Soil Science in 2006 in Philadelphia that will feature leading scientists who will discuss research frontiers and needs concerning the critical zone, and a database specialist. The current vision for WSSC incorporates four components: 1) a set of "node" sites for data collection; 2) a network of "backbone" soil sites that will be investigated for a standard set of weathering parameters over a range of depths; 3) technical support for instrument and sample node sites and backbone sites and coordinated data management and sample storage systems; and 4) the integration of these efforts through a variety of community-building approaches.

The broader impacts of this funding request include the following: 1) improved understanding of the current diversity of questions within the fields of weathering science and environmental biogeochemistry; 2) improved understanding by US scientists of weathering initiatives occurring abroad; 3) development of a coordinated plan to quantify weathering rates in diverse settings; 4) development of a plan to standardize data gathering in the field of weathering science; 5) development of a plan to store and disseminate data from weathering sites worldwide for use by the entire natural sciences community; and 6) organization of the scientific community to investigate fundamental questions in weathering science with great relevance to human society and natural ecosystems.

ABSTRACT Severmann, Anbar, McManus (0551716, 0551732, 0551605)
Intellectual merit: The biogeochemical cycles of iron and sulfur are closely coupled, and their combined influence impacts the evolution of the global carbon and oxygen cycles as well as the ocean's proton balance over geologic time. Our preliminary data show that Fe isotope compositions of dissolved and particulate species unambiguously reflect their depositional conditions in modern aqueous environments. This research determines the isotopic expressions of these cycles as specifically linked to the primary sources and sinks of Fe and S in oxygen-deficient aqueous settings. Specific questions to be addressed are: (1) how does the relative availability of Fe and S influence the isotopic expression of their cycling and (2) does benthic Fe recycling on oxic continental shelves influence the Fe isotope composition within anoxic basin sediments. Samples from two modern anoxic lake environments with contrasting sulfate levels will be analyzed (the Black Sea sulfate enriched, and Lake Tanganyika sulfate poor). This work leverages off on-going NSF-funded studies and all samples come with rich ancillary data sets, providing essential information regarding S isotope compositions, Fe speciation and general sediment diagenetic parameters. The proposed work will provide information essential to our interpretation of the Fe cycle in both the modern and ancient ocean as well as the evolution of the Earth's atmosphere and the redox balance of the modern atmosphere-ocean system. Fe and S will be extracted from sediment samples by sequential leaching. Fe and S isotopes will be measured using a multi-collector ICP-MS or isotope ratio mass spectrometry. Standard wet chemistry will be used to determine Fe and S speciation in the associated pore waters and mineral leachates.

Broader impacts: This work funds investigators at institutions in three states: California, Oregon, and Arizona and involved international collaborations with scientists in Germany and Turkey. The research supports a young, female principal investigator and a graduate student, the latter who will spend time learning analytical techniques in the collaborating institutions. It will also allow participation of the lead PI and her student to participate in the field program in Africa. US, as well as African undergraduates will be involved and mentored in paleoclimate research.

Middle and Upper Devonian Black Shales: Testing the Productivity-Anoxia Feedback and Land Plant-Weathering Rate Hypotheses


Thomas Algeo (University of Cincinnati), Ariel Anbar (Arizona State University), Robert Creaser (University of Alberta), Peter Sauer (Indiana University), and Lorenz Schwark (University of Cologne)
EAR-0618003
ABSTRACT
The Middle to Late Devonian was characterized by profound changes in marine and terrestrial biotas (including the "Frasnian/Famennian mass extinction"), weathering processes and soil development, global climate, and the exogenic C-S cycle. Inconclusive evidence for major bolide impacts and a wealth of data documenting long-term changes in marine nutrient cycles favor intrinsic processes based on oceanographic and/or weathering rate controls. Two important hypotheses based on such mechanisms are the productivity-anoxia feedback (Ingall et al., 1993) and land-plant weathering rate (Algeo et al., 1995, 2001) models. These models envision similar environmental conditions in Devonian epicratonic seas (eutrophic surface waters, elevated primary productivity, and benthic oxygen depletion) yet different, but not mutually exclusive, controls thereon. The productivity-anoxia feedback model invokes enhanced microbial recycling of nutrients within the water column in combination with hypolimnial denitrification, seasonal water-column overturn, and N limitation of primary productivity, whereas the land plant-weathering rate model invokes elevated fluxes of weathering-derived nutrients as a consequence of the spread of land plants and intensified pedogenesis. PIs propose to test these models within key horizons (the North American equivalents of the Kellwasser and Hangenberg events) in drillcores from the Appalachian, Illinois, and Alberta basins using integrated chemostratigraphic datasets that will include elemental concentration data, TOC-TIC, organic d13C and d15N, whole-rock 187Os/188Os and d97/95Mo, HI-OI, and biomarkers. PIs will make their data available to the larger scientific community by importing them into the CHRONOS System and PaleoStrat. The broader impacts of this project are varied and include public outreach, mentoring of undergraduate and graduate students, development of research synergies among a diverse group of geoscience professionals, and the potential for results of broad scientific significance. The PIs are committed to advancing science education in the public schools, to building "bridges" (especially for women and underrepresented minorities) to college-level science programs, and to training the next generation of scientists.

The Paleozoic record is punctuated by multiple, large positive carbon isotope excursions that are expressed regionally if not globally. In younger records, similar excursions are often linked through direct observation to ocean-scale events of enhanced organic carbon burial--typically under well-characterized anoxic conditions. In older sequences, lacking preserved deep seafloor, the nature of oceanic redox on the broad scale can only be surmised through use of geochemical proxies that are typically ground-truthed in younger settings. In particular, our work and that of other researchers has illuminated the great potential of the molybdenum isotope proxy for quantifying global deep-ocean redox, when applied with careful consideration to local oxygen conditions and the basinal Mo inventory.

In this study we expand the concept of an Oceanic Anoxic Event--first defined for episodes of pervasive deep-ocean and epicontinental black shale deposition during the Mesozoic--to address the nature of ocean-scale redox in the Paleozoic. We focus on the Late Cambrian SPICE event (Steptoean Positive Carbon Isotope Excursion), suggested by our preliminary C and S isotope data from shelf carbonates and our geochemical box model to be a prime candidate for an early Paleozoic OAE. The Alum black shale in Sweden shows clear signs of the SPICE excursion in the organic C fraction and evidence for at least local euxinia before, during, and after the event--making it an ideal candidate for Mo isotope analysis. A central goal, then, is to extrapolate the OAE concept to the Paleozoic, which has numerous positive C isotope excursions of varying global expression but little physical evidence for conditions in the deep ocean. We will specifically test whether the SPICE is an OAE. Strongly analogous patterns of C and S isotope behavior, black shale geochemistry, and biotic extinction have been described from the better-known Toarcian event. We therefore seek to compare the shale geochemistry and supporting carbonate proxies for seawater composition for these two intervals to ask: 1) Do Mo isotope records from the Upper Cambrian Alum Shale in Sweden point to the globally expanded anoxia inferred from our high-resolution delta13C and delta34S carbonate data from the United States? 2) Do the SPICE and Toarcian C isotope excursions show analogous Mo isotope and C-S-Fe-trace metal behavior, such that significant new light is shed on the nature of the Cambrian event? 3) Do organic biomarker patterns associated with the SPICE match those observed from the Toarcian OAE, suggesting that euxinia shallowed as its areal extent increased? 4)By analogy, can we extrapolate models for the Toarcian to understand invertebrate extinction patterns in the early Paleozoic, including problematic trilobite extinctions? 5)Using our integrated data for the SPICE as a template, are Paleozoic intervals of pronounced positive delta13C and epicontinental black shale deposition analogous to the OAEs of the Mesozoic?
All of these questions will be addressed through collaboration with experts on each time interval and through use of the geochemical proxies that are staples in our combined research groups--specifically Fe speciation, trace metal chemistry (emphasizing Mo), and novel isotope approaches for S, Fe, and Mo.

Broader Impacts. In a sincere effort to extend the impact of this study beyond the Lyons/Anbar research groups, we have designed a two-pronged approach for outreach in the greater Riverside-LA area. First, Lyons/Anbar/Gill will participate during each of the project years in the UCR Mentoring Summer Research Internship Program, whereby students from ethnic groups historically underrepresented in the sciences (particularly the earth sciences) will receive hands-on experience in the two labs. Second, Lyons/Anbar/Gill will work with the Aquarium of the Pacific in Long Beach, CA, to design an exhibit centered on the global epidemic of anthropogenic coastal hypoxia. Happily, the LA area has seen an improvement in its coastal water quality in recent years. Building from this success and lessons learned from the past--including the very deep past--we expect to reach out to the public about the health of coastal environments in an informative, optimistic, and hopefully entertaining way. Given the 1.3 million annual visitors to the aquarium, we are certain our message will spread widely.

EAR 0745825
COLLABORATIVE RESEARCH: Ocean Redox Evolution at the Dawn of Animal Life: An Integrated Geological and Geochemical Study of the Ediacaran Yangtze Platform in South China
ABSTRACT
Recent studies suggested that major oxidation events during the Ediacaran Period (ca. 635 Ma to 542 Ma) triggered the first appearance and evolution of the Earth?s earliest animal life, but critical evaluation of the proposed linkages is limited by the lack of a detailed documentation on spatial and temporal redox changes of Ediacaran oceans and the responses of Ediacaran organisms to such redox changes. An integrated geological, geochemical, and paleobiological study of the Ediacaran Yangtze platform is aimed at improving our understanding of the interplay between ocean redox changes, geochemical anomalies, and early animal evolution in a rarely preserved, fossiliferous sedimentary archive. The proposed research is designed to test the following hypotheses: (1) the deep ocean was anoxic/euxinic until ca. 551 Ma; (2) episodic oxidation of a large oceanic dissolved organic carbon (DOC) reservoir led to the formation of geochemical anomalies including unusually negative carbon isotope excursions; and (3) the spatial and temporal distribution of Ediacaran organisms was coupled with ocean redox conditions. Objectives of the research are to determine: (1) carbonate and organic carbon isotope variability across the basin to test a potential surface-to-deep ocean carbon isotope gradient that may have been much greater than in the modern ocean; (2) spatial and temporal sulfur isotope variability to test the persistence and/or fluctuation of sulfate reduction and sulfur disproportionation across the basin; (3) spatial and temporal changes of molybdenum (Mo) concentrations and Mo isotopes, iron (Fe) speciation and Fe isotopes to determine the secular redox evolution and potential redox fluctuation associated with stable isotope excursions; and (4) spatial and temporal occurrences of Ediacaran fossils and their relationships with geochemical boundaries/anomalies. The ultimate goal of the research is to integrate paleontological and geochemical data to test the coupling between redox conditions and spatial/temporal patterns of Ediacaran organisms. Anticipated data would provide important information for our understanding of the environmental forces related to a significant biological innovation in Earth history.
The project will partially support four PhD students from University of Nevada Las Vegas, Virginia Polytechnic Institute, University of California at Riverside, and Arizona State University. The project develops new collaborations between researchers at four different institutions and provides a broad training opportunity for interactions among students with different research foci. Research results will be integrated with courses taught at four institutions and will enhance undergraduate involvement in the research project at four institutions. The project will also promote international collaborations with scientists from institutions in China and Canada.

Although many trace metals, such as zinc (Zn), act as vital nutrients for marine microorganisms, their oceanic biogeochemical cycles are poorly understood. In this research, chemists from Arizona State University and the University of Washington would use a suite of experimental, analytical, and computational research to quantitatively understand the fractionation of stable Zn isotopes that takes place on mineral surfaces in the ocean. Through advancing our understanding of the reactions involved in Zn isotope fractionation in the ocean, future scientists would be able to successfully apply isotopic zinc cycling to questions of greater oceanographic interest.

In terms of broader impacts, this study would provide new insights into the biogeochemical cycling of the micronutrient zinc. One graduate student and one undergraduate student at Arizona State University would be supported and trained as part of this project.

This work tests the application of Uranium (U) isotopes preserved in carbonate sediments as a paleo-redox proxy. Significant variability exists in U isotope composition, due largely to isotope fractionation during redox transformations of U in solution. This suggests that the U isotope composition of seawater may be determined by the redox state of the global ocean. This research will involve laboratory experiments to determine whether U isotopes fractionate during abiotic precipitation of calcite and aragonite, which will serve as a baseline against which to compare any biogenic fractionation. A field component will investigate fractionation of U isotopes in natural carbonates, both biogenic and abiotic. This will include study of how low temperature alteration during deposition and burial might affect the preservation of the primary U isotope signal. Funding provides research opportunities for undergraduates from the Arizona State University Honors College, and supports a PhD thesis.

This project will examine the influence of particle size on atmospheric reactions of iron and, in turn, the influence of particle size on iron solubility. In particular, how particle size affects iron solubility during atmospheric processing by two different mechanisms will be investigated. First, the effect of particle size on iron solubility during photoreduction of iron in cloud waters will be determined. Photochemical reduction of aqueous iron has been well studied in authentic and simulated cloud waters, however, particle size has never been considered as a variable but may be important because only a restricted aerosol size fraction can form cloud condensation nuclei (CCN). Previous laboratory studies focusing on particles too big or too small to act as CCN may under- or overestimate the soluble iron resulting from photochemistry in real atmospheric systems. Second, the influence of particle size on iron solubility during reaction with gaseous sulfur dioxide will be investigated. Exposure of iron phases mixed with sodium chloride will be studied at two relative humidities (20% and 80%) representative of dry continental and wet marine environments, respectively. This will allow determination of whether gas-particle or liquid-particle reactions are more important during iron-sulfur interactions. Following exposure to sulfur dioxide, the iron isotope composition of the dissolved iron fraction will be determined and used to elucidate mechanisms.

This research will be a valuable contribution to understanding iron solubility in continental and marine aerosols. The results will be relevant to the broader question of how atmospheric iron affects ocean productivity and, hence, its relation to the global carbon cycle. Iron is a limiting nutrient in many parts of the open ocean and substantial effort has been put forth to determine the availability of iron in atmospheric particulate matter to marine life. This study will also advance the training of the next generation of atmospheric scientists. The project will fund one Ph.D. student at Arizona State University (ASU), with this research being the core of his/her thesis work. In addition, one undergraduate student each year from Northern Arizona University (NAU) will work with the principal investigators and the Ph.D. student at ASU. The Department of Chemistry at NAU is a non-Ph.D. granting department. Therefore, collaboration with ASU researchers will provide undergraduate students at NAU training in research approaches and techniques that are not normally possible at NAU. Furthermore, NAU is among the national leaders in granting degrees to Native American students. These unique demographics will be drawn upon to recruit environmentally-focused Native American undergraduates through the Institute for Tribal Environmental Professionals at NAU.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

With this award from the Major Research and Instrumentation (MRI) program, Peter Williams, Ariel D. Anbar, James R. Anderson, Richard L. Hervig and Willem F. Vermaas will acquire an imaging secondary ion mass spectrometer (SIMS) instrument. This novel and powerful instrument will be used to support an extended group of researchers working on diverse topics involving both soft (biological) materials and hard materials (minerals), and at the interface between the two (biosensors, antibiotic clays, nanoparticle toxicity). The projects have in common the need for chemical, and in particular isotopic, analysis at length scales below conventional SIMS instrumentation. The research will impact fundamental research and underpin applied research widely. It will yield insights in a number of areas including studies of the early stages of life on earth, and fundamental studies of metabolism in photosynthetic organisms and biosynthetic pathways for lipid formation. Studies to improve the efficiency for biofuel production in a process that recycles waste carbon dioxide from power stations will be investigated. The chemistry and origins of aerosols will be undertaken and thus contribute to the understanding of atmospheric chemistry and global warming. The study of volcanic magma may yield time-resolved information about magma conditions in the hours and days before eruption, aiding prediction of these cataclysmic events.

An Imaging Secondary Ion Mass Spectrometer probes the chemical composition of surfaces and thin films. A surface is bombarded with ions prepared in an ion source. This dislodges material from the surface which is analyzed by the mass spectrometer. The ion beam will also scan over the material giving an image of the surface. This allows researchers to correlate the chemical composition with the properties of hard materials (e.g. minerals) and soft (e.g. cells) at the nano scale level. The interdisciplinary studies that will be carried out using this instrument will have an impact in materials research, chemistry, biology, geology and atmospheric science. The undergraduate and graduate students who will use the equipment in their research projects will be trained in imaging science with state of the art instrumentation.

Intellectual merit: The PIs propose to obtain high-resolution trace metal geochemical profiles from organic-rich sedimentary rocks to examine the evolution of climate and biospheric oxygenation in the Late Archean to Middle Proterozoic. The connections between climate and oxygenation are manifold. Oxygen levels in the deep sea are affected by the rate at which organic carbon is exported from productive surface waters, and hence ultimately from atmospheric CO2. In turn, enhanced burial of organic carbon in marine sediments can increase the O2 content of the atmosphere, with climatic consequences on an Archean Earth dependent on CH4 as a greenhouse gas. Oxygen levels also affect the ocean concentrations of trace nutrients such as Fe and Mo, potentially altering the vigor of marine surface biota and the efficiency of surface-to-deep carbon pumping. Earlier work by the PIs discovered traces of oxygenic photosynthesis and surface ocean oxygenation at least 50-100 M.y. before the first major rise of atmospheric O2 (2.45-2.32 Ga Great Oxidation Event; GOE). Their chemostratigraphic approach revealed an otherwise unrecognized history of biospheric oxygenation that is more complex than previously realized. Therefore, detailed investigation of this history allows them to test fundamental concepts that relate O2, carbon, micronutrients and climate. For example, can the same basic concepts developed to explain Holocene climate and carbon cycling explain conditions in the Archean and Proterozoic? The PIs propose to refine the timeline of biospheric oxygenation by developing an extensive compilation of trace metal concentrations for Late Archean to Middle Proterozoic rocks emphasizing key intervals straddling the GOE: the 2.7 Ga Joy Lake Sequence (Minnesota, U.S.A.), the 2.3 Ga Rooihoogte and Timeball Hill Formations (South Africa), and the 1.8-1.7 Ga Chuanlinggou Formation (North China). Trace metal geochemical profiles, when combined with sedimentary Fe geochemistry, can constrain the nature of local sedimentary conditions (e.g., bottom water redox state and basin restriction). Bottom water Mo concentrations in ancient oceans can be estimated by comparing Mo/TOC of these rock samples with sediment Mo/TOC and seawater concentrations in modern anoxic basins. For other trace metals whose marine geochemistry is less well understood, broad differences in metal marine budgets between time intervals can be made by comparison with Mo. The Mo isotope paleoredox proxy will be used to procure independent constraints on the extent of regional/global water column euxinia and assess the impact on trace metal abundances in seawater. Re-Os geochronology may provide precise depositional ages.

The PIs will address four main questions:
1. How long is the time lag between the development of pervasive surface ocean oxygenation (and by inference oxygenic photosynthesis) and the GOE?
2. What is the response of early Paleoproterozoic metal marine budgets to the GOE?
3. Do metal marine budgets show temporal trends in the Middle Proterozoic related to increasing biospheric O2 and/or expansion of ocean euxinia?
4. What implications do such trends have for climate during the early Earth and how was microbial and eukaryotic ecology and evolution affected?


Broader Impact: This proposal promotes the early career development of Co-PI Kendall. Additionally, as a component of their project activities, the PIs plan to establish a pilot project that will provide laboratory research experience for ASU undergraduates with physical disabilities (i.e., vision, hearing, speech, or motor impairments). The ultimate goal of the pilot is to increase access to science laboratories for postsecondary students with disabilities. It will also leverage the experiences of Kendall as a successful young laboratory scientist with severe hearing and mild speech impairments. Specific programs will be crafted for each student in collaboration with the ASU Disability Resource Center (DRC). The DRC will provide classroom aids and assistive technologies to facilitate direct student participation in laboratory research activities, including sample preparation, analysis, data reduction, and preparation of undergraduate theses.

In many regions of the world's ocean, primary productivity is not limited by the major nutrients (nitrogen, phosphorous and silica) but by the micronutrient iron (Fe). One major source of Fe is the atmospheric transport and deposition of aerosols to the open ocean. The aerosols come from natural sources, such as soils and dust and biomass burning, and from anthropogenic emissions related to industrial processes and energy generation. Our understanding of the sources is limited by our ability to identify the origin of the Fe. Mechanisms of tracing the sources of aerosols include the use of the elemental ratios as specific sources have specific elemental signals. Fe isotopic variation has recently been demonstrated to be a potentially important tracer of Fe sources.

This project, a collaboration between investigators at Arizona State University and Northern Arizona University, will explore the use of Fe isotopes as a tracer of natural and anthropogenic sources of aerosols to assess their importance as a source of Fe to the open ocean. Fe is known to limit primary production in many high nutrient, low chlorophyll areas, so it is important to understand the origin of the Fe that is delivered to the oceans and its availability to marine microorganisms. Additionally, aerosols from different sources have variable size and solubility in seawater and therefore this also impacts Fe bioavailability. Examination of the isotopes of Fe in aerosols could help address these questions as the investigators' prior research has demonstrated distinct variations in the isotopic composition of aerosol Fe that arise from natural and anthropogenic sources.

The study will measure the Fe isotopic compositions of aerosol particles collected on Bermuda over a period of one year. Bermuda was chosen as seasonal differences lead to different aerosol types being deposited - summer winds flow from the east and carry Saharan soil dust and other aerosols, while winter winds originate from over North America. The project will compare the Bermuda results with that of key anthropogenic and natural aerosol materials that could be a source of Fe to the Atlantic Ocean. In addition, elemental analyses of these aerosols will provide an independent confirmation of the Fe isotopes results. Analysis of size-segregated samples will provide additional information and will be coupled with solubility experiments designed to assess the soluble Fe fraction.

Broader Impacts: The scientific impact of this work relates to obtaining a better understanding of the factors that impact the sources and availability of Fe, an important limiting micronutrient, to the ocean, and to marine microorganisms. As a part of the proposed project, the investigators will develop interactive educational activities to teach the major concepts of ocean nutrient availability and limitation to non-science students, which will be part of a new course "Habitable Worlds". Additionally, the proposed project will support graduate student training, and benefit under-represented groups.

Intellectual merit: This project will develop a new interdisciplinary partnership between connectivity ecology (Levin at SIO), metal isotope geochemistry (Anbar and Gordon at ASU), and paleoclimatology (Herrmann at ASU) to identify new proxies for ocean acidification that can be used to assess pH exposures in living organisms and, potentially to interpret the geologic record. The investigators hypothesize that the isotopic composition of larval calcium carbonates reflects changes in seawater chemistry driven by ocean acidification and, in some instances, with associated decline in oxygen levels. The large extent to which these two parameters vary in concert in the modern and past ocean (and thus have joint influence), and the extent to which they may be uncoupled by anthropogenic CO2 inputs, merits considerable attention. Thus, the integration of pH and oxygen in proxy development would be an important advance.

The focus of this project is on proxy development to determine pH exposure history for living organisms in their larval state, and will center on calcium, boron, and uranium isotopes as well as multi-elemental fingerprints. For this project, the investigators will target open coast, front bay and backbay mytilid mussel species, each living naturally under a different pH regime, and statoliths of encapsulated market squid larvae from the open shelf. Larvae with known pH, oxygen and temperature exposure histories will be obtained from (1) laboratory larval rearing experiments that manipulate pH and oxygen and (2) in situ out planting of lab-spawned larvae in larval homes onto existing moorings where pH, T and oxygen are being monitored. Analyses will employ SIMS (for del 11B), multicollector (for del 44Ca, del 238 U), and laser ablation ICP-MS (targeting B, Cu, U, Pb, Mo, and a suite of additional pH- and redox-sensitive trace elements). Multivariate statistical tools will define ability to detect pH-induced signatures and to determine species or taxon-specific vital effects. The investigators are exploring proxies for invertebrate larvae that are untested in the context of acidification geochemistry. Targeting larvae is critical as many marine organisms produce larval carbonate structures and these stages may be most affected by ocean acidification. The retention of larval shell and statoliths after recruitment may ultimately allow us to test the importance of larval pH and O2 exposure to survival and population persistence. An ability to assess past exposures through geochemical proxies will provide information about relative pH tolerances and ecosystem-level change in response to changes in the ocean¡¦s carbonate chemistry.

Broader impacts: This project will: (1) engaging young scientists in new collaborations (2) involving underrepresented students through UC summer diversity programs and (3) conveying the science to students via UCSD IGERT courses in the program Global Change, Marine Science and Society, as well as via courses taught by Levin, Anbar and Herrmann. Translation of ecological results to the fields of marine geochemistry and paleoclimatology (and back) will provide the seed for future collaboration and advances.

COLLABORATIVE RESEARCH: Integrated Paleoceanographic Analysis of the Late Paleozoic Midcontinent Sea

Achim Herrmann, Arizona State University. EAR-1052988
Thomas Algeo, Univ. Cincinnatti, EAR-1053449
James Barrick, Texas Tech University, EAR-1053042
Bernd Haupt, Penn State University, EAR-1052998

ABSTRACT
Due to different environmental conditions and paleogeographic settings of ancient times, some past sedimentary environments have no good modern analogues. For instance, previous interpretations of environmental conditions of black shale deposition centered on applying modern analogs of coastal upwelling or ?Black-Sea type? silled basin topographies. However, a superestuarine circulation model has been proposed recently to explain the abundant and widespread Paleozoic black shale deposits of Midcontinent North America. It is the purpose of this research project to use an interdisciplinary approach to investigate paleoceanographic conditions during the deposition of Pennsylvanian cyclothems of Midcontinent North America and to test the ?superestuarine circulation hypothesis?. This work is a comprehensive data-model synthesis study and geochemical proxies (strontium and oxygen isotopes of biogenic apatite; bulk major- and trace-element abundance data, TOC-TIC-S concentrations, and petrographic data) will be compared to biofacies distribution patterns and to results of numerical ocean circulation models.

Funding provides research opportunities for undergraduates at several universities and will support one PhD thesis.

Oxygen, in the form of the molecule O2, is abundant in the Earth's atmosphere and oceans, where it is vital for all multi-cellular life, including humans. However, O2 was nearly absent from the atmosphere and oceans during the first half of Earth's history. In the past decade, we solidified our understanding of when the prolonged and complex transition to the modern, O2-rich environment began. However, the cause of this so-called "Great Oxidation Event" (GOE) and later changes in O2 remains one of the major mysteries in Earth System Science. Solving it is of more than academic interest because it will help us understand how the Earth supports life, and provide insights and perspective on some of the environmental challenges posed by human activity. This project will tackle this challenge by combining new data and calculations that reach from the Earth's core to the top of the atmosphere to develop a comprehensive model of the geochemical cycle of O2 that can explain the GOE.

The specific research program is motivated by an emerging consensus that biological O2 production began long before the GOE. If so, then the GOE was most likely triggered by a change in O2 consumption. Various lines of reasoning point to changes in the flux of O2-reactive material from the Earth's mantle, perhaps driven by the gradual but inexorable cooling of the planet's interior. However, the specific changes and their causes are unclear and debated. The project team will refine and test a number of hypotheses proposed in the past decade. To do so it necessarily integrates: models of atmospheric chemistry; records of Earth's surface O2 history developed from inorganic and organic geochemical proxies; laboratory calibrations of these proxies; geochemical analyses of samples from the lithosphere and mantle; seismic reconstructions of Earth's interior structure; geodynamic models of mantle mixing and evolution; thermodynamic calculations; and findings from mineral physics experiments. Researchers in these disciplinary communities rarely collaborate. Therefore, the work will be scientifically transformative.

The project team aims to extend this transformation beyond its members and even beyond the geosciences. In addition to the typical training and dissemination activities, we will foster communication and integration across disciplinary boundaries by: conducting open, online "workshops without walls" on the O2 puzzle; perform scholarly research into our collaborative research challenges and practices to identify and disseminate best practices for transdisciplinary team science; and develop, deploy, and assess a teacher professional development (PD) program centered on how scientists communicate across diverse disciplinary divides to answer complex questions. These broader activities, together with the science research program, will advance a holistic vision of the Earth System that, while of broad societal importance, is often discussed but rarely realized.

Society's response to climate change and many other challenges hinges on public understanding that science is not a body of facts and certainties in tidy disciplines, but rather a process of reasoning which often crosses disciplines and which narrows the uncertainties of knowledge. Unfortunately, the way science is taught to non-science students at most large universities tends to reinforce misconceptions. For example, many students satisfy their general science requirement in very large introductory lecture courses based on traditional disciplines. While some of these courses are excellent, they often emphasize facts rather than scientific reasoning. Lectures are often supplemented by laboratories to address this gap. However, when class sizes reach the hundreds, laboratories often feature scripted "cookbook" activities that do not teach students to reason scientifically.

In this project, the investigators are deploying and assessing a large-enrollment undergraduate general education science course that places scientific reasoning and multidisciplinary perspectives at the heart of the experience. This model is possible because of developments in online, computer-assisted education (cyberlearning). The project builds on Arizona State University's semester-long "Habitable Worlds" course, which is organized around the search for intelligent life beyond Earth. Motivated by the question "Are we alone?" students explore key science concepts from astronomy to sustainability using online tutorials that employ interactive simulations and immersive, media-rich "virtual field trips" (VFTs). Video lectures are embedded in the tutorials, but as scaffolding rather than as centerpieces. The tutorials utilize an intelligent software platform that responds adaptively to student input--essentially, a virtual tutor--and collects data on students' actions and inputs useful for learning research and course development. Such platforms that can be programmed by the instructor are now becoming commercially available. The investigators' thesis is that for large student populations this model is superior to conventional lecture-based online and face-to-face courses.

"Habitable Worlds" was piloted in Fall 2011 and will have been offered to about 800 ASU students online by the end of Fall 2012. In this project, the investigators, in collaboration with Maricopa Community College District (MCCD) faculty, are deploying and assessing a new version, "Habitable Worlds 2.0," which is optimized to scale to even larger and more diverse student populations. In this revised course, tutorials follow a learning progression from less to more mathematically involved, and are better aligned with K-12 education standards for pre-service teachers enrolled in ASU's Mary Lou Fulton Teachers College (MLFTC). Data collected by the tutoring platform is being used for research on student problem-solving. The investigators are also comparing the effectiveness of VFTs to physical field trips and are rigorously evaluating course effectiveness using both formative and summative methods.

Because of the size of ASU and MCCD, this project could have far-reaching effects on undergraduate science education nationwide. Because "Habitable Worlds 2.0" is part of the redesigned teacher preparation program at MLFTC, which is one of the largest teacher preparation programs in the United States, the project is also likely to have a broad impact on K-12 education.

This request is for partial support of a workshop that be held in Phoenix, Arizona, during May 17-19, 2015. The workshop will bring together an international group of about 50 isotope geochemists and biomedical researchers to explore the use of high precision isotope analysis, particularly of the heavy metals or metallomics, as disease biomarkers.

It is known that disruptions in the metabolism of inorganic elements can be the cause or result from some diseases, such as Alzheimer, osteoporosis, and cancer. The aim of the workshop is to identify medical questions where sophisticated technologies, methodologies, and concepts that have been used in the geological and environmental sciences can be applied to combat disease. Results of the workshop will be published in a report that will serve as the founding document of the new field of isotope metallomic biomarkers and will be available to researchers and the public.

The project will study the response of marine animal ecosystems to environmental change using three mass extinction events from the geological record as study systems. Specifically, the project will test the hypothesis that a large proportion of extinction during these events can be explained by the stresses that elevated temperatures and reduced oxygen availability place on animal respiration. Geochemical data will be used to constrain computer simulations of changing ocean conditions during these mass extinction events. Results from laboratory studies on animal respiration will then be paired with fossil data to assess whether differences in extinction intensity in space and across taxonomic groups can be explained by spatial variation in environmental change or differences among taxonomic groups in their ability to withstand environmental change. The project will provide interdisciplinary training to a group of graduate students and post-docs. It will further impact STEM education through the creation of a website that will allow access to model results so that students can visualize and explore model output to understand cause-effect relationships between continental configuration, ocean conditions, and biological diversity. The investigators will also offer short-courses on Earth system modeling and data interpretation at major conferences that will be recorded for asynchronous use. The project will also involve the development of a podcast series addressing how we reconstruct the ancient Earth system and use these reconstructions to better understand the present and predict the future.

In this project, the hypothesis will be tested that the loss of habitat through constraints on aerobic respiration under climate change and ocean deoxygenation can explain the magnitude, taxonomic selectivity, and latitude variation in intensity for the Late Devonian (Frasnian-Fammenian), end-Permian, and end-Triassic mass extinction events. Paleoredox and paleoclimate proxy data and geochemical indicators of diagenetic alteration will be used for both global average and local conditions before and after each major event combined with predictions from Earth system models and occurrence data from the fossil record of marine animals to separate aspects of extinction than can be explained by physiological stress from those that require other explanations.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

This project aims to serve the national interest by developing a scalable model for bringing research into online undergraduate programs. There has been a tremendous shift towards online learning in the past two decades. At the core of this initiative is the desire to make participation in research accessible to a diverse population of learners who may not be able to accommodate the standard model of full-time education on a physical campus. Participation in research is a critical component of any STEM degree, as it involves learners in the process of scientific inquiry, while improving students’ data literacy and critical thinking skills. Although participation in research is a common component of in-person STEM degrees, fewer opportunities exist for online students. This project will broaden student participation in research through the implementation of a course-based undergraduate research experience (CURE) geared towards students enrolled in online astronomy degree programs. This CURE will take the form of an upper-level research course that focuses on computational literacy and data replication. The emphasis on renewed analysis of existing data is an innovative and significant divergence from the way CUREs are typically conducted. Since multiple students can engage in analysis of the same dataset, this design will highlight the under-discussed role of result replication. As a result, this scalable replication-based model will be transferable to other institutions while simultaneously laying the groundwork for developing online CUREs for students across a variety of scientific disciplines.

The goal of this project is to address a common disparity between online and in-person STEM degree programs by providing students in the Astronomical and Planetary Sciences program with an upper-level research course that focuses predominantly on research literacy and data replication. This research course will emphasize the importance of repeated analysis as it pertains to exoplanet observational characteristics. Future space-based observations of exoplanets require ongoing maintenance of their predicted celestial position, also known as ephemerides. Replication-driven research of this kind will provide updated ephemerides, making meaningful contributions to current exoplanet research. Using established measures from prior work analyzing undergraduate research experiences, the project team will study the effectiveness of this course to determine the impact of an online CURE designed around the use of data analysis and reproducibility on student learning, research literacy, and student self-efficacy. The goal of this research is to advance understanding of the design components that are required in an effective CURE, knowledge that will inform the development of both online and in-person undergraduate research courses in the future. The NSF IUSE: EHR Program supports research and development projects to improve the effectiveness of STEM education for all students. Through the Engaged Student Learning track, the program supports the creation, exploration, and implementation of promising practices and tools.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.