The Subduction Margin Carbon Cycle: A Preliminary Assessment of the Distribution Patterns of Multicycle Carbon (NSF, OCE-1144483)
The accretionary wedge portion of a subducting margin creates an intersection of multiple C-cycles that operate on vastly different timescales. This is largely unexplored aspect of the global C-cycle. Ancient (fossil rock) C is liberated via uplift and mass wasting, and mixed with more contemporary forms of organic C in surface environments. As the multicycle C mixtures are dispersed throughout the sedimentary system their components will express different behaviors reflecting their respective compositions and reactivities. The presence of the fossil C component has not been considered in most studies of active margin. We propose exploratory studies of the three GeoPRISMS Subduction Cycles and Deformation (SCD) primary focus sites, the Alaskan, Cascadia, and Hikurangi Margins, with the specific objective of developing a preliminary assessment of the distribution of multicycle C at the sites. Samples will come primarily from archives held by the National Institute of Water and Atmospheric Research of New Zealand and the Ocean Drilling Program repository in the US. In addition, sample collection and analysis is proposed for the planned Integrated Ocean Drilling Program Expedition 341. Analyses of samples will include Raman and FTIR microscopy, stable carbon and radiocarbon isotopic measurements, and elemental (H/C) determinations.
Critical Zone Observatory (CZO)
Critical Zone Observatory for Intensively Managed Landscapes, with U. Illinois Urbana Champaign, University of Iowa, Purdue, and other institutions (NSF, CZO Program, #EAR-1331906)
This project establishes a CZO for quantifying the fluxes and transformations, as well as interactions, thresholds, and dynamic feedbacks of water, nutrients, and sediment in IMLs and to characterize how rapid land use changes have altered the vulnerability and resilience of these systems. The observatory will consist of a network of sites (3,690 km2 Upper Sangamon River Basin in Illinois and 270 km2 Clear Creek Watershed in Iowa), and a third participating site (44,000 km2 Minnisota River Basin) already supported by NSF’s Water Sustainability and Climate (WSC) program to study human and climate dynamics as amplifiers of change.
Pathway-specific isotopic approach to assess biostimulation in coalbeds (ISEN)
The objective of this research is to develop and validate a new isotopic tool to identify and trace specific pathways of methanogenesis within coalbeds, yielding essential information to guide engineered efforts to biostimulate sustainable in situ microbial gas productionfrom subsurface carbon sources such as coal. Carbon isotopes are useful for understanding methanogenesis because it is a highly-frationating process causing distinctive enrichment of the lighter isotope 12-C in methane and the heavier isotope 13-C in the residual carbon source. Because of the highly-fractionating nature of methanogenesis compared to other steps such as the release of easily metabolized organic intermediates from coal, carbon isotopes provide a powerful tool for examining methanogenesis and acetate utilization, using field-collected water samples that represent actual conditions of the subsurface. Specifically, variation in the carbon isotope ratio of acetate provide direct, unequivocal evidence that methane is derived by acetate fermentation rather than CO2 reduction, in contrast to other techniques that can be ambiguous due to their lack of process-specificity or the addition of laboratory artifacts.
A Potential Fungal Contribution to the Selective Preservation of Long-chain Hydrocarbon Functionality in Soils and Sediments (ACS-PRF, #52142-ND2)
An oft-studied problem in organic geochemistry concerns the mechanisms by which long-chain aliphatic functional groups are seemingly selectively preserved or enriched in soils and sediments. It is proposed that fungi have the potential to contribute to both the general sequestration of organic C and specific lipids, such as fatty acids. Degradation experiments are being performed to study the recalcitrant biopolymeric material that remains in fungal necromass.
INDEPENDENT STUDENT & POST-DOC FUNDING
Schlanger Scientific Ocean Drilling Fellowship (2012 – 2013), Laurel Childress: Mass wasting of sedimentary rock from uplifted accretionary wedges injects recycled organic carbon, along with modern material into the marine environment. In an active margin system this recycled pool represents a significant portion of the organic carbon that becomes buried. The behavior of recycled carbon as it moves towards subduction zones remains poorly understood beyond the shelf and upper slope of active margins. Recycled carbon (e.g. kerogen) is more inert that younger forms derived from plants and soils, and this recalcitrance should lead to persistence, even through burial and incorporation into the accretionary wedge. To assess the validity of this hypothesis, sediments from the Cascadia subduction margin are analyzed for the presence and persistence of recycled carbon.
IODP (COL) Post-Expedition Activity Award (2014 – 2015), Laurel Childress: The Southern Alaska Margin (IODP Expedition 341) represents an ideal active margin system in which to study the relationship between tectonic and glacial changes and ancient carbon export through time. As a preliminary study of these processes, material from Site U1417 will be used to investigate variation in sedimentary provenance to the distal Surveyor Fan. The investigation of organic geochemical changes through time relates directly to two primary scientific objectives of this expedition. The determination of changes in the relative input and nature (soil, kerogen, etc.) of terrestrial organic carbon to the Surveyor Fan will aid in documenting the tectonic response to climate change (Scientific Objective 1). Furthermore, interpretation of organic carbon sources downcore and into the Miocene will be an important component in the source-to-sink study of interactions between glaciation, climate change, and tectonic uplift (Scientific Objective 3).
NORTHWESTERN UNDERGRADUATE RESEARCH GRANTS (URG):
The Impact of Agriculture on Carbon (2017), Nina Zhou: Globally, an estimated 16.7 million reservoirs have been rapidly accumulating organic carbon (OC). Research has linked OC accumulation in reservoirs with the emission of methane. Despite the potential importance to the global C-cycle and climate, little research has been done on the nature of the OC in reservoir sediments. This project seeks to better understand this cycle better by studying lake sediment samples from an Illinois reservoir impacted by agriculture. By studying the import of OC, it will be possible to better understand the transport and erosion of carbon due to farming, and how it may contribute to methane production. The sedimentary organic carbon is expected to be a mixture of vascular plant inputs from land (including crops), and algal inputs supported by agricultural nutrients delivered to the lake. One experimental parameter that will be used to identify OC components in mixtures is the 13C/12C stable isotopic ratio, which is reported as the δ 13C value. This project seeks to isolate the signals from the different organic sources by performing a density separation and studying low density plant fragments in Lake Decatur sediments. Specifically, the plant debris will be analyzed for the carbon isotope values. After separating and analyzing the plant debris, I predict that the isotope value of the plant fraction should parallel the known changes in the crop input. The findings of this study will have implications for how agricultural practices impact not only the local environment but also how they impact the global carbon cycle.
Biomarker analyses in Lake Decatur sediments (2017), John M. Hayes: Increasingly industrial agriculture and food processing practices have created greater demand for water resources. In an attempt to meet this demand, many rivers have been dammed, however the resulting effects of the carbon cycle via carbon sequestration and prolific methane production are not well understood. The organic geochemistry of sediment cores from Lake Decatur, IL, a 95-year-old impoundment on the Sangamon River in the Intensively Managed Landscape – Critical Zone Observatory (IML-CZO), was studied to assess the sources of organic matter to the lake. Online tetramethylammonium hydroxide (TMAH) thermochemolysis GC-MS was used to provide a broad-spectrum analysis using small samples with a minimum of preparation. This work was generously supported by NSF award 1331906 (Critical Zone Observatory for Intensively Managed Landscapes) as well as the Lane Fund for Environmental Studies Research in the Weinberg College of Arts and Sciences at Northwestern University.
Carbonate measurements using DRIFT (2017), Rachel So: My project focuses on quantifying carbonate found in sediment and soil samples using diffused reflectance infrared Fourier-Transform (DRIFT) spectroscopy. Particulate carbonate is rarely found in freshwater environments. More commonly, it remains dissolved until it reaches a marine environment (e.g. a river empties into the ocean) where it then precipitates out. A possible reason for the presence of carbonate is the application of agricultural lime in surrounding farmlands. Agricultural lime, made from calcium carbonate, is commonly used to increase the pH of soil. Runoff from these farms would wash lime into nearby rivers. Of course, there are numerous other ways particulate carbonate can end up in rivers (e.g. erosion of carbonate rocks) and it is unlikely that there is only a single source. Currently, I have two project goals: 1) refine my calibration curve used for quantifying carbonate to account for multiple carbonate types, and 2) investigate sources of carbonate found in the Sangamon-Saybrook system.
Biodiesel from Chitinolytic Fungi (2014), Aarohi Shah: Chitin is the second most abundant natural biopolymer in the world. The motivation behind this research project is to discover chitinolytic fungal species that can rapidly utilize chitin as their primary food source, and produce a high percentage of fatty acids. This way, a waste source can be exploited to produce useful bioenergy.
Matrix Effects in Analysis of Lignin (2014), Rachel Bergman: The production of lignin phenol monomers via the oxidation of lignin using alkaline cupric oxide (NaOH/CuO) followed by gas chromatographic analysis of the derivatized products is the most widely accepted method for lignin studies. A newer method using the methylating reagent, tetramethylammonium hydroxide (TMAH), can utilize smaller soil sample sizes and requires only minutes to prepare. One potential disadvantage of the TMAH is the presence of a matrix effect created by inorganic minerals in soils and sediments. The objective of this experiment is to investigate the nature of these matrix effects, and how they might affect the results of the TMAH reaction.
Biodiesel from Spent Coffee Grounds (2013-2014), Elizabeth Conger: Through this research, the goal is to improve the viability of producing bioenergy such as biodiesel and biogas from spent coffee grounds (SCG), a waste product that may contain a significant amount of useful biomass for fuel production. The focus is specifically on the conversion of SCG fatty acids into fatty acid methyl esters (FAMEs), the chemical components of biodiesel.
Purification of Shrimp Shell Chitin (2013-2014), Fatty Acids in Chitin (2014), Jessie Moravek: Most fatty acids can be extracted from sediments using organic solvents. However, a significant fraction cannot be extracted in this way and must first be liberated by hydrolysis of ester or amide bonds. The understanding of the sources of these bound lipids is limited, but multiple studies have speculated about a relationship between fatty acids and chitin, a biopolymer found in arthropods and fungi. The purpose of this study is to attempt a new method for the isolation of chitin in order to determine if fatty acids are naturally associated with it.