Use of high resolution mass spectrometry to assess the role of molecular structure in organic matter phase partitioning during basalt weathering
EMSL Project ID
49725
Abstract
This project proposes to evaluate the development of spatial and temporal heterogeneity as a result of biogeochemical weathering and microbial colonization in granular basalt. The goal is to assess the couplings between microbially-mediated rock weathering and C sequestration that occur under controlled-environment hydrologic forcing of the initial stages of soil formation from rock. We hypothesize the observation of “hotspots” where particularly steep gradients in weathering will occur as a result of water movement and flow path development in initially homogeneous, isotropic hillslopes. Our research approach is to simulate rainfall on new model landscapes of the University of Arizona’s (UA) Biosphere 2 (B2) Landscape Evolution Observatory (LEO); a large-scale, climate-controlled research facility comprising three replicated 30 x 12 m convergent hillslopes. Soil solution and seepage samples will be collected during and after rainfall events and analyzed to quantify changes in the solution phase composition and mineral saturation states as a result of biotic and abiotic weathering. Solid samples will be collected to determine changes in physical, chemical and mineralogical properties of the granular basalt (with microbial analyses being conducted under a separate project), as influenced by landscape position and time. Obtained measurements will be integrated using a coupled hydrological-geochemical model (CrunchFlow + CATHY-NoahMP) now under development. We request limited-scale rapid access to EMSL facilities to characterize organic matter composition in solution and in the solid phase on LEO slopes in these initial stages of soil formation. We will compare solid phase organic matter composition to one in the original basalt, as well as evaluate effect of hillslope locations on organic matter in both solution and soil. This will allow us to gain preliminary understanding of the processes that are driving accumulation of C and its fractionation due to interactions with the newly forming minerals as soil develops. Previous experiments with the same material in the smaller-scale systems demonstrated that 1) significant increase in C concentrations is occurring over short time periods even in the systems without higher plants; 2) and abiotic reactions of basalt with the soil solution results in the change in composition of dissolved organic matter. The results will be used to guide our sampling approach for the future rainfall events allowing to generate the dataset that gives the best opportunity to observe C-sequestration in the soil as it forms under influence of abiotic and biological drivers. We request access to the Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) at EMSL for organic matter characterization in solution and soil extracts to support a large suite of analyses done at Biosphere 2 and University of Arizona to characterize the interactions between newly formed amorphous and crystalline minerals and organic compounds and their role in C stabilization on the landscapes.
Combining molecular scale measurements made at EMSL with information on hydrologic fluxes, water residence times and saturation states of different mineral phases derived from solution composition will allow us to observe, in real-time, the co-evolution of biological and geochemical structure during initial stages of basalt weathering and formation of pre-soil and to link small-scale biogeochemical processes to landscape-scale manifestations. The proposed project would generate quantitative data on relations among basalt weathering rates and C sequestration under controlled conditions. Inorganic and organic C sequestration during basalt weathering represents an important sink for atmospheric CO2 on a global scale. Information regarding the mechanisms and rates of this process, generated here by conjunctive measurement and modeling, is essential for understanding earth evolution as well as for predicting future C sequestration.
Project Details
Project type
Limited Scope
Start Date
2017-02-20
End Date
2017-04-22
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)