The Early Career Research Program supports the development of individual research programs of outstanding scientists early in their careers and stimulates research careers in the disciplines supported by the U.S. Department of Energy (DOE) Office of Science. Opportunities exist in the following program areas: Advanced Scientific Computing Research, Biological and Environmental Research (BER), Basic Energy Sciences, Fusion Energy Sciences, High Energy Physics, and Nuclear Physics.
For more specific information, see the DOE Office of Science Early Career Research Program website.
Early Career Awards funded by BER’s Subsurface Biogeochemical Research program are described below.
Isaac J. Larsen—University of Massachusetts-Amherst
Precipitation falling on mountainous watersheds is exposed to surface and subsurface processing, such as chemical weathering, before eventually leaving as streamflow. In turn, this processing is governed by a variety of abiotic and biotic interactions involving, e.g., the type of rock that governs geomorphology and mineralization and the type of vegetation that can generate acidity. The proposed work will focus on the role of vegetation as a means to influence water chemistry and quality. By employing a multi-scale approach, the project will address the following questions: 1) Does landscape-scale heterogeneity in vegetation, climate, and geology impart unique, spatially-variable signatures on soil production and chemical weathering rates? 2) What roles do the legacies of Pleistocene glaciation and Holocene geomorphic processes play in determining modern-day solute concentrations in surface waters? 3) Are physical erosion and chemical weathering rates linked at the watershed scale, and can these rates be predicted from watershed characteristics? These questions will be addressed in the physical and ecological setting of the East River watershed near Crested Butte, Colorado. The proposed technical approach will assess controls on weathering and solute generation at the soil profile, landform, and watershed scales. At the soil profile scale, soil production and chemical weathering rates will be quantified with cosmogenic nuclides and geochemical mass balance at sites that span biotic, climatic, and geologic gradients in order to isolate the key drivers of chemical weathering. At the landform scale, solute concentrations in surface waters will be used to assess whether surficial deposits generated by different geomorphic processes impart unique weathering signatures. At the watershed-scale, cosmogenic nuclides will be used to measure erosion rates. A series of reactive transport models will be constructed to place the field-based findings into a framework for making predictions regarding the roles that vegetation, climate, and geomorphology play in solute generation. The proposed research complements ongoing BER investments at the LBNL Watershed Science SFA Science Focus Area.
James Stegen—Pacific Northwest National Laboratory
A major challenge for prediction of watershed systems is understanding how perturbations (e.g., hydrologic disturbances) influence intense biogeochemical activity in space (hot spots) or time (hot moments). Most studies of hot spot/moments have focused on single sites, which leads to scientific discovery that is not necessarily transferrable across watersheds. To address this limitation, this study will use field infrastructure in >60 watershed field sites across the United States and analyses provided by the Environmental Molecular Sciences Laboratory user facility. Resulting data will be used to test numerical modeling predictions of mechanistic connections between dissolved organic matter (DOM) chemistry and biogeochemical control point influence (CPI). The CPI is the contribution of elevated biogeochemical rates in space or time to the net aggregated biogeochemical rate within a defined system. CPI quantification will be combined with an innovative application of ecological theory to highly-resolved molecular characterization of DOM that allows DOM chemistry to be summarized as a biogeochemically-relevant trait. Experimentation across broadly distributed watersheds combined with detailed molecular analysis will reveal general, transferrable principles that will be used to create a trait-based framework capable of predicting impacts of perturbations on biogeochemical CPIs across watersheds. This trait-based framework can be further integrated with advanced numerical models to link dynamic watershed processes to DOM chemistry and CPIs. Ultimately, the science conducted by this project will improve predictive capabilities from local to watershed to Earth-system scales.
Charuleka Varadharajan—Lawrence Berkeley National Laboratory
The frequency of occurrence, intensity, and extent of floods and droughts are projected to increase over the next decades due to climate change. Because these changes are likely to dramatically influence processes governing watershed functioning, there is a pressing need to understand and predict how water quality in streams and rivers will respond to new flow disturbance regimes. This study will determine how future changes in streamflow-disturbance events, ranging from floods to low-flow conditions, will change water quality over time. In addition, the research will explore how water quality further downstream of disturbance locations will change. The analysis will account for differences in disturbance types and watershed characteristics, including geomorphology, geology, climate, vegetation, and land use. The approach will be based on further development and application of a new framework comprising a novel data-integration tool, i.e., BASIN-3D, and sophisticated analytical methods including, e.g., wavelet and statistical time-series analyses and machine-learning techniques. This framework will be able to predict the resistance and resilience of water quality to different types of disturbance events, and will be applied to the Colorado, Columbia, and Delaware River watersheds. The outcome of this work will yield new predictions of watershed water quality responses to extreme perturbations. The same framework will also serve as a hub to enable the generation and analysis of integrated interagency watershed datasets in real-time that are transferable to many stakeholders.
J. D. Raff—Indiana University
Our current understanding of Earth’s climate is based on predictive atmospheric models that have become necessarily complex as they are extended to answer global–scale questions. Unfortunately, current models are unable to accurately represent all of the important chemical components due to challenges in identifying details of biogeochemical processes occurring within the terrestrial environment that have a significant impact on the atmosphere above. This is especially true for soil microbial emissions of reactive nitrogen (e.g., nitrous acid, nitric oxide, and nitrogen dioxide), which directly and indirectly affect climate by controlling the oxidative capacity of the atmosphere, lifetime of greenhouse gases, and formation rate of aerosols. This project will provide an improved mechanistic understanding of the fate of reactive nitrogen in soil that will enable these processes to be more accurately scaled from the laboratory to the ecosystem and global scales. A unique multidisciplinary approach will be taken to examine how variability in land surfaces and soil properties impact reactive nitrogen emissions, and to link soil fluxes of these gases to their microbial sources using a combination of laboratory and field studies, isotopic analysis, and genomic techniques. In addition, this research will leverage DOE investments in instrumentation at the Environmental Molecular Sciences Laboratory (EMSL) to study the effect of biogenic emissions of reactive nitrogen on the oxidative capacity of the soil environment and to understand how this is then coupled to the combined land–atmosphere carbon cycle. Results will be parameterized and included in the Community Earth System Model (CESM), with the goal of improving representation of the land–atmosphere exchange of reactive nitrogen in global climate models. These outcomes will support the Biological & Environmental Research Program’s goal of “discovering the physical, chemical, and biological drivers and environmental impacts of climate change.” This research was selected for funding by the Office of Biological & Environmental Research.
J. C. Rowland—Los Alamos National Laboratory
Floodplains are a critical missing component of Earth System Models (ESMs). Seasonally inundated regions are the dominant natural source of global methane (CH4) emissions, and floodplains comprise the single largest terrestrial sink for carbon shed from the land to terrestrial waters. The annual burial of carbon in continental sediments exceeds that buried in ocean sediments by an order of magnitude. To close the terrestrial carbon budget and accurately predict land fluxes to oceans, the lateral exchange of carbon between rivers and floodplain systems must be incorporated into ESM representations of the land surface. This research will develop a new representation of the physical dynamics of floodplains within the vegetated land unit of the Community Land Model (CLM). Unique to this land representation will be the capability to model the exchange of sediment, carbon, and other particulate constituents, between floodplains and rivers. River and floodplain physical dynamics will be directly coupled, allowing for the eventual modeling of biogeochemical (BGC) feedbacks between floodplains and rivers. The development of this model will use geomorphic scaling laws to correlate dynamic landscape processes to measurable and/or predictable land surface properties. In the second half of this project, field work and high resolution process–resolving models will be used to quantify sensitivities of floodplain BGC cycling to both scaling simplifications used to parameterize floodplains in ESMs and to system heterogeneities not resolvable in global–scale ESMs. This research was selected for funding by the Office of Biological & Environmental Research.
B. Powell, Clemson University
The study of the chemical and physical properties of actinide bonding and reactivity is essential for the development of an improved nuclear fuel cycle and to understand how the actinides move through the environment. This work will examine the fundamental chemical properties of actinide elements in aqueous solutions and at solid–water interfaces. Sorption of actinides to solid surfaces such as minerals and soils can limit the movement of actinides in the environment and sorption to engineered solids can facilitate separation of actinides from other waste materials within the nuclear fuel cycle. Understanding and quantifying actinide bonding and reactivity at solid–water interfaces is needed for a wide range of applications such as advanced actinide separation schemes, waste treatment and disposal, understanding actinide behavior under geologic repository conditions, and determining the performance of actinide bearing wastes and waste facilities. A novel aspect of this work will be to examine sorption processes on a mechanistic basis and quantify the data using a standard thermochemical construct as opposed to the empirical methods commonly employed. The overarching objectives of this work are to provide a mechanistic conceptual model and a quantitative sorption model describing actinide behavior at solid–water interfaces based on a molecular level understanding of the chemical processes involved. Particular attention will be focused on understanding underlying mechanisms of actinide sorption to differing solid phases, understanding underlying mechanisms behind frequent observations of hysteretic sorption and understanding the potential formation of ternary actinide–ligand–surface complexes. The ability to predict distribution of the actinides between aqueous and solid phases in the presence of various organic ligands represents a step towards the development of unique, organic solvent free separation systems based on solid–liquid partitioning and will also improve models of actinide behavior in natural systems containing naturally occurring organic ligands. This research was selected for funding by the Office of Basic Energy Sciences and the DOE Experimental Program to Stimulate Competitive Research.
M.J. Marshall—Pacific Northwest National Laboratory
Microbial biofilms impact many biogeochemical processes including the fate and transport of contaminants in the subsurface. The present research will employ state–of–the–art technologies to determine the chemical composition of biofilms in relation to their highly hydrated native–state structure/architecture. The research will extend the mechanistic understanding of extracellular polymeric substance (EPS)–metal ion interactions using high–resolution cryogenic imaging and analysis techniques at the Environmental Molecular Sciences Laboratory (EMSL) and will develop new spectroscopy methods for obtaining spatially resolved chemical information. Synchrotron X–ray–based analyses will be used to obtain high–sensitivity, element–specific chemical distributions within biofilms that have been imaged using EMSL microscopies and spectroscopies. These integrated technologies will characterize the chemical and physical interactions of hydrated biofilms and catalytic components of EPS as they interact with redox–transformable metal ions and influence biogeochemical reactions. Determining the chemical composition and spatial coordination of biofilm–associated EPS will significantly advance understanding of how molecular–scale biogeochemical reactions can influence subsurface contaminant fate and transport at larger scales. This research was selected for funding by the Office of Biological and Environmental Research (BER)
M. Ye, Florida State University
Subsurface environmental systems, in which intricate biogeochemical processes interact across multiple spatial and temporal scales, are open and complex. Understanding and predicting system responses to natural forces and human activities is indispensable for environmental management and protection. However, predictions of the subsurface system are inherently uncertain, and uncertainty is one of the greatest obstacles in groundwater reactive transport modeling. The goals of this project are to (1) develop new computational and mathematical methods for quantification of predictive uncertainty and (2) use the developed methods as the basis to develop new methods of experimental design and data collection for reduction of predictive uncertainty. The proposed computational Bayesian framework is general and compatible with other widely used reactive transport models and numerical codes, so the advances can be easily applied to gain insights into subsurface biogeochemical processes that occur across a wide range of field sites and environmental conditions. This research was selected for funding by the Office of Biological and Environmental Research.
2011 PECASE Award
Heileen Hsu-Kim (Duke Univ.) recipient of the Presidential Early Career Award for Scientists and Engineers (PECASE) for leading nanogeochemistry research to understand toxin subsurface transport establishing a new geochemical framework for predicting mercury methylation potential in contaminated sediments and for leadership in publishing and collaboration with synchrotron scientists in the United States and Europe.
H. Hsu-Kim—Duke University
Effective solutions for remediation of mercury contamination remain elusive because of our poor understanding of biogeochemical processes that control mobilization of mercury and biomethylation in sediments. This research seeks to characterize the geochemical forms of mercury that persist in polluted sediments and link this knowledge to their bioavailability toward microbes. The fate of mercury in these settings involves a complex series of transformations including HgS mineral dissolution, colloid formation and transport, oxidation/reduction, and methylation by anaerobic sediment bacteria. In all of these steps, natural organic matter (NOM) plays a critical role for reaction rates. This research aims to elucidate the nanoscale interactions between mercury, sulfide, and NOM that are critical drivers of mercury geochemistry. This information will ultimately be used to establish a new geochemical framework for predicting mercury methylation potential in contaminated sediments. This research was selected for funding by the Office of Biological and Environmental Research (BER).
November 2019 [PDF]