A5060402302- Seismic Waves and Analysis
- Methane Hydrates and Related Phenomena
- Seismology and Earthquake Studies
- Earthquake Detection and Analysis
- Soil Moisture and Remote Sensing
- Radioactive element chemistry and processing
- Soil Carbon and Nitrogen Dynamics
- Iron oxide chemistry and applications
- Hydrocarbon exploration and reservoir analysis
- Microbial Community Ecology and Physiology
- Clay minerals and soil interactions
- Peatlands and Wetlands Ecology
- Geology and Paleoclimatology Research
- Soil and Water Nutrient Dynamics
- Groundwater flow and contamination studies
- Atmospheric and Environmental Gas Dynamics
- Groundwater and Isotope Geochemistry
- Heavy metals in environment
- Arsenic contamination and mitigation
- Agriculture, Soil, Plant Science
- Mine drainage and remediation techniques
- Microbial metabolism and enzyme function
- Rabbits: Nutrition, Reproduction, Health
- Plant and Fungal Interactions Research
- Marine and environmental studies
University of San Francisco
2023-2024
Lawrence Berkeley National Laboratory
2017-2023
California State University, East Bay
2020-2023
Lawrence Livermore National Laboratory
2018-2022
Colorado State University
2017
Pennsylvania State University
2013
Oscillating redox conditions are a common feature of humid tropical forest soils, driven by an ample supply and dynamics reductants, high moisture, microbial oxygen consumption, finely textured clays that limit diffusion. However, the net result variable soil regimes on iron (Fe) mineral associated carbon (C) forms fluxes is poorly understood in soils. Using 44-day incubation experiment with soils from Puerto Rico, we examined patterns Fe C transformations under four regimes: static anoxic,...
Soil microorganisms help transform plant inputs into mineral-associated soil organic carbon (SOC) – the largest and slowest-cycling pool of on land. However, microbial traits that influence this process are widely debated. While current theory biogeochemical models have settled carbon-use efficiency (CUE) growth rate as positive predictors SOC, empirical tests sparse, with contradictory observations. Using 13C-labeling an annual grass (Avena barbata) under two moisture regimes, we found...
Abstract Historically, it is believed that crystalline uraninite, produced via the abiotic reduction of hexavalent uranium (U (VI) ) dominant reduced U species formed in low-temperature roll-front ore deposits. Here we show non-crystalline (IV) generated through biologically mediated predominant an undisturbed deposit Wyoming, USA. Characterization revealed majority (∼58-89%) bound as to C-containing organic functional groups or inorganic carbonate, while uraninite and represent only minor...
Organo-mineral and organo-metal associations play an important role in the retention accumulation of soil organic carbon (SOC). Recent studies have demonstrated a positive correlation between calcium (Ca) SOC content range types. However, most these focused on soils that contain carbonate (pH > 6). To assess importance Ca-SOC lower pH soils, we investigated their physical chemical interaction grassland Point Reyes National Seashore (CA, USA) at spatial scales. Multivariate analyses our bulk...
Abstract Phosphorus (P) is a key limiting nutrient in highly weathered soils of humid tropical forests. A large proportion P these bound to redox‐sensitive iron (Fe) minerals; however, little known about how Fe redox interactions affect soil cycling. In an incubation experiment, we changed bulk regimes by varying headspace conditions (air versus N 2 gas) and examined the responses species two fluctuating treatments (4‐ or 8‐day oxic followed 4‐day anoxic) static (oxic anoxic). anoxic...
Thawing permafrost forms "thaw ponds" that accumulate and transport organic carbon (OC), redox-active iron (Fe), other elements. Although Fe has been shown to act as a control on the microbial degradation of OC in soils, role cycling thaw ponds remains poorly understood. Here, we investigated Fe-OC interactions partially fully thawed soils ("bog" "fen" ponds, respectively) peatland complex Abisko, Sweden, using size separation (large particulate fraction (LPF), small (SPF), dissolved (DF)),...
Abstract Switchgrass is a deep-rooted perennial native to the US prairies and an attractive feedstock for bioenergy production; when cultivated on marginal soils it can provide potential mechanism sequester accumulate soil carbon (C). However, impacts of switchgrass establishment biotic/abiotic properties are poorly understood. Additionally, few studies have reported effects cultivation lands that low nutrient quality (N/P) or in areas experienced high rates erosion. Here, we report...
Hyporheic zones act as critical ecological links between terrestrial and aquatic systems where redox-sensitive metals of iron (Fe) manganese (Mn) significantly impact nutrient cycling water quality. However, the geochemical controls on release speciation Fe(II) Mn(II) in these biogeochemical hotspots are still poorly understood. Here we conducted batch incubation experiments analyzed Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy data using sediment samples from a...
Abstract Background Wet tropical forest soils store a vast amount of organic carbon and cycle over third terrestrial net primary production. The microbiomes these have global impact on greenhouse gases tolerate remarkably dynamic redox environment—driven by high availability reductant, soil moisture, fine-textured that limit oxygen diffusion. Yet microbiomes, particularly virus-host interactions, remain poorly characterized, we little understanding how they will shape future cycling as...
The traditionally held assumption that photo-dependent processes are the predominant source of H2O2 in natural waters has been recently questioned by an increrasing body evidence showing ubiquitiousness dark water bodies and groundwater. In this study, we conducted field measurement intra-meander hyporheic zone surface at East River, CO. On-site detection using a sensitive chemiluminescence method suggests concentrations groundwater ranging from 6 nM (at most reduced region) to ~ 80 (in...
Abstract Humid tropical forest soils experience frequent rainfall, which limits oxygen diffusion and creates redox heterogeneity in upland soils. In this study we gauged the effect of short‐term anoxic conditions on Fe mineralogy relatively Fe‐ C‐rich surface (C/Fe mole ratio ∼5) from a humid Puerto Rico. Soils subjected to 4‐d oxic/anoxic oscillation were characterized by selective chemical extractions, Mössbauer spectroscopy (MBS), X‐ray diffraction. Chemical extraction data suggested that...
ABSTRACT Oscillating redox conditions are the norm in tropical soils; driven by an ample supply of reductants, high moisture, microbial oxygen consumption, and finely textured clays that limit diffusion. Yet net result variable soil regimes on iron-organic matter (Fe-OM) associations soils owing to changing climate is poorly understood. Using a 44-day incubation experiment with humid from Puerto Rico, we examined patterns Fe C transformation under four regimes: static anoxic, flux 4-day (4d...
Abstract. Soil redox conditions exert substantial influence on biogeochemical processes in terrestrial ecosystems. Humid tropical forest soils are often characterized by fluctuating dynamics, yet how these dynamics affect patterns soil versus litter decomposition and associated CO2 fluxes is not well understood. We used a 13C-labeled addition to explicitly follow the of litter-derived vs. native soil-derived organic matter response four different regimes – static oxic or anoxic, two...
Abstract Soil redox conditions exert substantial influence on biogeochemical processes in terrestrial ecosystems. Humid tropical forest soils are often characterized by fluctuating dynamics, yet how these dynamics affect patterns soil versus litter decomposition and associated CO 2 fluxes is not well understood. We used a 13 C-labeled addition to explicitly follow the of litter-derived vs. native soil-derived organic matter response four different regimes—static oxic or anoxic, two...