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First Assessment On The Air Co2 Dynamic In The Show Caves Of Tropical Karst, Vietnam, Duc A. Trinh, Quan H. Trinh, Angel Fernández-Cortés, David Mattey, Javier G. Guinea 2018 Vietnam Atomic Energy Institute

First Assessment On The Air Co2 Dynamic In The Show Caves Of Tropical Karst, Vietnam, Duc A. Trinh, Quan H. Trinh, Angel Fernández-Cortés, David Mattey, Javier G. Guinea

International Journal of Speleology

In this study, air, water, and host rock in show caves in a Vietnam’s karst region was monitored and analyzed to identify the ventilation regime and track the cave air CO2 sources. In general, the studied caves are well ventilated. In dynamic – multiple entrance caves, air ventilation is described with the use of U shape model. In static – single entrance cave, air circulation is explained by cold air trap model. Both ventilation models suggest that air is more circulated in winter than in summer. Seasonally, the cave air CO2 increases from early spring to summer. Value in ...


An Optical Method For Carbon Dioxide Isotopes And Mole Fractions In Small Gas Samples: Tracing Microbial Respiration From Soil, Litter, And Lignin, Steven J. Hall, Wenjuan Huang, Kenneth E. Hammel 2018 Iowa State University

An Optical Method For Carbon Dioxide Isotopes And Mole Fractions In Small Gas Samples: Tracing Microbial Respiration From Soil, Litter, And Lignin, Steven J. Hall, Wenjuan Huang, Kenneth E. Hammel

Steven J. Hall

Rationale

Carbon dioxide isotope (δ13C value) measurements enable quantification of the sources of soil microbial respiration, thus informing ecosystem C dynamics. Tunable diode lasers (TDLs) can precisely measure CO2 isotopes at low cost and high throughput, but are seldom used for small samples (≤5 mL). We developed a TDL method for CO2 mole fraction ([CO2]) and δ13C analysis of soil microcosms.

Methods

Peaks in infrared absorbance following constant volume sample injection to a carrier were used to independently measure [12CO2] and [13CO2] for subsequent calculation of δ13C values. Using parallel soil incubations receiving differing C substrates, we partitioned respiration from ...


Elevated Moisture Stimulates Carbon Loss From Mineral Soils By Releasing Protected Organic Matter, Wenjuan Huang, Steven J. Hall 2018 Iowa State University

Elevated Moisture Stimulates Carbon Loss From Mineral Soils By Releasing Protected Organic Matter, Wenjuan Huang, Steven J. Hall

Steven J. Hall

Moisture response functions for soil microbial carbon (C) mineralization remain a critical uncertainty for predicting ecosystem-climate feedbacks. Theory and models posit that C mineralization declines under elevated moisture and associated anaerobic conditions, leading to soil C accumulation. Yet, iron (Fe) reduction potentially releases protected C, providing an under-appreciated mechanism for C destabilization under elevated moisture. Here we incubate Mollisols from ecosystems under C3/C4 plant rotations at moisture levels at and above field capacity over 5 months. Increased moisture and anaerobiosis initially suppress soil C mineralization, consistent with theory. However, after 25 days, elevated moisture stimulates cumulative gaseous C-loss as ...


Scale-Dependent Linkages Between Nitrate Isotopes And Denitrification In Surface Soils: Implications For Isotope Measurements And Models, Steven J. Hall, Samantha R. Weintraub, David Bowling 2018 Iowa State University

Scale-Dependent Linkages Between Nitrate Isotopes And Denitrification In Surface Soils: Implications For Isotope Measurements And Models, Steven J. Hall, Samantha R. Weintraub, David Bowling

Steven J. Hall

Natural abundance nitrate (NO3−) isotopes represent a powerful tool for assessing denitrification, yet the scale and context dependence of relationships between isotopes and denitrification have received little attention, especially in surface soils. We measured the NO3−isotope compositions in soil extractions and lysimeter water from a semi-arid meadow and lawn during snowmelt, along with the denitrification potential, bulk O2, and a proxy for anaerobic microsites. Denitrification potential varied by three orders of magnitude and the slope of δ18O/δ15N in soil-extracted NO3− from all samples measured 1.04 ± 0.12 (R2 = 0.64, p < 0.0001), consistent with fractionation from denitrification. However, δ15N of extracted NO3− was often lower than bulk soil δ15N (by up to 24 ‰), indicative of fractionation during nitrification that was partially overprinted by denitrification. Mean NO3− isotopes in lysimeter water differed from soil extractions by up to 19 ‰ in δ18O and 12 ‰ in δ15N, indicating distinct biogeochemical processing in relatively mobile water versus soil microsites. This implies that NO3− isotopes in streams, which are predominantly fed by mobile water, do not fully reflect terrestrial soil N cycling. Relationships between potential denitrification and δ15N of extracted NO3− showed a strong threshold effect culminating in a null relationship at high denitrification rates. Our observations of (1) competing fractionation from nitrification and denitrification in redox-heterogeneous surface soils, (2) large NO3− isotopic differences between relatively immobile and mobile water pools, (3) and the spatial dependence of δ18O/δ15N relationships suggest caution in using NO3− isotopes to infer site or watershed-scale patterns in denitrification.


Drivers And Patterns Of Iron Redox Cycling From Surface To Bedrock In A Deep Tropical Forest 1 Soil: A New Conceptual Model, Steven J. Hall, Daniel Liptzin, Heather L. Buss, Kristen DeAngelis, Whendee L. Silver 2018 Iowa State University

Drivers And Patterns Of Iron Redox Cycling From Surface To Bedrock In A Deep Tropical Forest 1 Soil: A New Conceptual Model, Steven J. Hall, Daniel Liptzin, Heather L. Buss, Kristen Deangelis, Whendee L. Silver

Steven J. Hall

Iron (Fe) reduction and oxidation are important biogeochemical processes coupled to decomposition, nutrient cycling, and mineral weathering, but factors controlling their rates and spatial distribution with depth are poorly understood in terrestrial soils. In aquatic ecosystems, Fe reduction often occurs below a zone of oxic sediments. We tested an alternative conceptual model for Fe redox cycling in terrestrial soils using a deep humid tropical forest soil profile. We hypothesized that Fe reduction in anaerobic microsites scales with depth variation in labile C and Fe availability, as opposed to bulk oxygen (O2). We measured bulk O2 at multiple depths from 0 ...


Iron Isotope Fractionation During Fe(Ii) Oxidation Mediated By The Oxygen-Producing Marine Cyanobacterium Synechococcus Pcc 7002, Elizabeth S. Swanner, Timm Bayer, Wenfang Wu, Likai Hao, Martin Obst, Anneli Sundman, James Martin Byrne, F. M. Michel, I. C. Kleinhanns, A. Klapper, R. Schoenberg 2017 Iowa State University

Iron Isotope Fractionation During Fe(Ii) Oxidation Mediated By The Oxygen-Producing Marine Cyanobacterium Synechococcus Pcc 7002, Elizabeth S. Swanner, Timm Bayer, Wenfang Wu, Likai Hao, Martin Obst, Anneli Sundman, James Martin Byrne, F. M. Michel, I. C. Kleinhanns, A. Klapper, R. Schoenberg

Elizabeth D. Swanner

In this study, we couple iron isotope analysis to microscopic and mineralogical investigation of iron speciation during circumneutral Fe(II) oxidation and Fe(III) precipitation with photosynthetically produced oxygen. In the presence of the cyanobacterium Synechococcus PCC 7002, aqueous Fe(II) (Fe(II)aq) is oxidized and precipitated as amorphous Fe(III) oxyhydroxide minerals (iron precipitates, Feppt), with distinct isotopic fractionation (ε56Fe) values determined from fitting the δ56Fe(II)aq (1.79‰ and 2.15‰) and the δ56Feppt (2.44‰ and 2.98‰) data trends from two replicate experiments. Additional Fe(II) and Fe(III) phases were detected using microscopy ...


Phosphate Speleothems In Caves Developed In Iron Ores And Laterites Of The Carajás Mineral Province (Brazil) And A New Occurrence Of Spheniscidite, Alan R.L. Albuquerque, Rômulo S. Angélica, Daniele F. Gonçalves, Simone P.A. Paz 2017 Universidade Federal do Pará

Phosphate Speleothems In Caves Developed In Iron Ores And Laterites Of The Carajás Mineral Province (Brazil) And A New Occurrence Of Spheniscidite, Alan R.L. Albuquerque, Rômulo S. Angélica, Daniele F. Gonçalves, Simone P.A. Paz

International Journal of Speleology

The Carajás Mineral Province has one of the largest concentrations of caves in Brazil, and its iron ore is among the country’s main exports. As a result of iron ore intense extraction, new environmental policies have been implemented. In an attempt to balance economic activity and environmental conservation, an inventory and a relevance-based classification of caves were implemented in 2008 as criteria for environmental licensing of mining ventures. This implementation motivated the present study of phosphate speleothems in Carajás’ caves developed in ferriferous rocks. The objectives of this study are to describe the phosphate minerals and their formation processes ...


An Optical Method For Carbon Dioxide Isotopes And Mole Fractions In Small Gas Samples: Tracing Microbial Respiration From Soil, Litter, And Lignin, Steven J. Hall, Wenjuan Huang, Kenneth E. Hammel 2017 Iowa State University

An Optical Method For Carbon Dioxide Isotopes And Mole Fractions In Small Gas Samples: Tracing Microbial Respiration From Soil, Litter, And Lignin, Steven J. Hall, Wenjuan Huang, Kenneth E. Hammel

Ecology, Evolution and Organismal Biology Publications

Rationale

Carbon dioxide isotope (δ13C value) measurements enable quantification of the sources of soil microbial respiration, thus informing ecosystem C dynamics. Tunable diode lasers (TDLs) can precisely measure CO2 isotopes at low cost and high throughput, but are seldom used for small samples (≤5 mL). We developed a TDL method for CO2 mole fraction ([CO2]) and δ13C analysis of soil microcosms.

Methods

Peaks in infrared absorbance following constant volume sample injection to a carrier were used to independently measure [12CO2] and [13CO2] for subsequent calculation of δ13C values. Using parallel soil incubations receiving differing C substrates, we partitioned respiration from ...


Assessing The Periodic Groundwater Flow Conditions Of A Perched Aquifer System In The Daniel Boone National Forest, Ethan Sweet 2017 Murray State University

Assessing The Periodic Groundwater Flow Conditions Of A Perched Aquifer System In The Daniel Boone National Forest, Ethan Sweet

Posters-at-the-Capitol

Assessing the Periodic Groundwater Flow Conditions of a Perched Aquifer System in the Daniel Boone National Forest

Ethan Sweet and Jonathan Malzone

Eastern Kentucky University, Department of Geosciences

Natural ephemeral wetlands situated among the ridge-tops in the Daniel Boone National Forest serve as reservoirs that recharge a shallow groundwater system. Unique interactions between surface and groundwater in these isolated systems provide substantial support for the native ecosystem, serving as a breeding ground for amphibians and as source water for vegetation—especially in periods of drought. Currently it is not understood how groundwater could provide regional biodiversity, a drought buffer, or ...


The Effects Of Environment On Arctica Islandica Shell Formation And Architecture, Stefania Milano, Gernot Nehrke, Alan D. Wanamaker Jr, Irene Ballesta-Artero, Thomas Brey, Bernd R. Schöne 2017 University of Mainz

The Effects Of Environment On Arctica Islandica Shell Formation And Architecture, Stefania Milano, Gernot Nehrke, Alan D. Wanamaker Jr, Irene Ballesta-Artero, Thomas Brey, Bernd R. Schöne

Alan Wanamaker

Mollusks record valuable information in their hard parts that reflect ambient environmental conditions. For this reason, shells can serve as excellent archives to reconstruct past climate and environmental variability. However, animal physiology and biomineralization, which are often poorly understood, can make the decoding of environmental signals a challenging task. Many of the routinely used shell-based proxies are sensitive to multiple different environmental and physiological variables. Therefore, the identification and interpretation of individual environmental signals (e.g., water temperature) often is particularly difficult. Additional proxies not influenced by multiple environmental variables or animal physiology would be a great asset in the ...


The Influence Of Temperature And Seawater Carbonate Saturation State On 13c–18o Bond Ordering In Bivalve Mollusks, R. A. Eagle, J. M. Eiler, A. K. Tripati, J. B. Ries, P. S. Freitas, C. Hiebenthal, Alan D. Wanamaker, M. Taviani, M. Elliot, S. Marenssi, K. Nakamura, P. Ramirez, K. Roy 2017 University of California, Los Angeles

The Influence Of Temperature And Seawater Carbonate Saturation State On 13c–18o Bond Ordering In Bivalve Mollusks, R. A. Eagle, J. M. Eiler, A. K. Tripati, J. B. Ries, P. S. Freitas, C. Hiebenthal, Alan D. Wanamaker, M. Taviani, M. Elliot, S. Marenssi, K. Nakamura, P. Ramirez, K. Roy

Alan Wanamaker

The shells of marine mollusks are widely used archives of past climate and ocean chemistry. Whilst the measurement of mollusk δ18O to develop records of past climate change is a commonly used approach, it has proven challenging to develop reliable independent paleothermometers that can be used to deconvolve the contributions of temperature and fluid composition on molluscan oxygen isotope compositions. Here we investigate the temperature dependence of 13C–18O bond abundance, denoted by the measured parameter Δ47, in shell carbonates of bivalve mollusks and assess its potential to be a useful paleothermometer. We report measurements on cultured specimens spanning a ...


Oxygen Isotope Ratios In The Shell Of Mytilus Edulis: Archives Of Glacier Meltwater In Greenland?, E. A. A. Verteegh, M. E. Blicher, J. Mortensen, S. Rysgaard, T. D. Als, Alan D. Wanamaker 2017 University of Reading

Oxygen Isotope Ratios In The Shell Of Mytilus Edulis: Archives Of Glacier Meltwater In Greenland?, E. A. A. Verteegh, M. E. Blicher, J. Mortensen, S. Rysgaard, T. D. Als, Alan D. Wanamaker

Alan Wanamaker

Melting of the Greenland Ice Sheet (GrIS) is accelerating and will contribute significantly to global sea level rise during the 21st century. Instrumental data on GrIS melting only cover the last few decades, and proxy data extending our knowledge into the past are vital for validating models predicting the influence of ongoing climate change. We investigated a potential meltwater proxy in Godthåbsfjord (West Greenland), where glacier meltwater causes seasonal excursions with lower oxygen isotope water (δ18Ow) values and salinity. The blue mussel (Mytilus edulis) potentially records these variations, because it precipitates its shell calcite in oxygen isotopic equilibrium with ambient ...


Annually Resolved North Atlantic Marine Climate Over The Last Millennium, D. J. Reynolds, J. D. Scourse, P. R. Halloran, A. J. Nederbragt, Alan D. Wanamaker, P. G. Butler, C. A. Richardson, J. Heinemeier, J. Eiriksson, K. L. Knudsen, I. R. Hall 2017 Cardiff University

Annually Resolved North Atlantic Marine Climate Over The Last Millennium, D. J. Reynolds, J. D. Scourse, P. R. Halloran, A. J. Nederbragt, Alan D. Wanamaker, P. G. Butler, C. A. Richardson, J. Heinemeier, J. Eiriksson, K. L. Knudsen, I. R. Hall

Alan Wanamaker

Owing to the lack of absolutely dated oceanographic information before the modern instrumental period, there is currently significant debate as to the role played by North Atlantic Ocean dynamics in previous climate transitions (for example, Medieval Climate Anomaly-Little Ice Age, MCA-LIA). Here we present analyses of a millennial-length, annually resolved and absolutely dated marine δ18O archive. We interpret our record of oxygen isotope ratios from the shells of the long-lived marine bivalve Arctica islandica (δ18O-shell), from the North Icelandic shelf, in relation to seawater density variability and demonstrate that solar and volcanic forcing coupled with ocean circulation dynamics are key ...


Facilitate Visualization And Distribution Of Nasa's Environmental Science Data Through Open Standards And Open Source Software For Geospatial, Yaxing Wei, Zhaoying (Angie) Wei, Suresh SanthanaVannan 2017 Oak Ridge National Laboratory

Facilitate Visualization And Distribution Of Nasa's Environmental Science Data Through Open Standards And Open Source Software For Geospatial, Yaxing Wei, Zhaoying (Angie) Wei, Suresh Santhanavannan

Free and Open Source Software for Geospatial (FOSS4G) Conference Proceedings

This paper introduces the utilization of open standards and open source software for visualization and distribution of geospatial environmental science data at the Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC). The ORNL DAAC is one of the NASA Earth Observing System Data and Information System (EOSDIS) data centers. A big challenge for the ORNL DAAC (https://daac.ornl.gov) is to efficiently manage over a thousand heterogeneous environmental data, collected through field campaigns, aircraft/satellite observations, and model simulations. ORNL DAAC also has to provide tools to easily find, visualize, and access the heterogeneous data. To address ...


Nitrogen And Carbon Isotopic Dynamics Of Subarctic Soils And Plants In Southern Yukon Territory And Its Implications For Paleoecological And Paleodietary Studies, Farnoush Tahmesabi, Fred J. Longstaffe, Grant Zazula, Bruce Bennett 2017 The University of Western Ontario

Nitrogen And Carbon Isotopic Dynamics Of Subarctic Soils And Plants In Southern Yukon Territory And Its Implications For Paleoecological And Paleodietary Studies, Farnoush Tahmesabi, Fred J. Longstaffe, Grant Zazula, Bruce Bennett

Earth Sciences Publications

We examine here the carbon and nitrogen isotopic compositions of bulk soils (8 topsoil and 7 subsoils, including two soil profiles) and five different plant parts of 79 C3 plants from two main functional groups: herbs and shrubs/subshrubs, from 18 different locations in grasslands of southern Yukon Territory, Canada (eastern shoreline of Kluane Lake and Whitehorse area). The Kluane Lake region in particular has been identified previously as an analogue for Late Pleistocene eastern Beringia. All topsoils have higher average total nitrogen δ15N and organic carbon δ13C than plants from the same sites with ...


Methylmercury Production In Two Northern Fen Peatlands, Mikhail J. Mack 2017 The University of Western Ontario

Methylmercury Production In Two Northern Fen Peatlands, Mikhail J. Mack

Electronic Thesis and Dissertation Repository

Northern peatlands provide conditions favourable for sulphate reducing bacteria, microorganisms responsible for producing methylmercury, an aquatic pollutant. An expected climate driven shift from moss- to sedge-dominance may alter mercury biogeochemistry. Observations from a moss-dominated poor fen and sedge-dominated intermediate fen were used to compare methylmercury to assess if contrasting plant communities, nutrients status and/or hydrologic regime control production. Chapter 2 compared porewater methylmercury and ancillary chemistry across two Northern Ontario fens. The lower water table, greater dissolved organic carbon, and lower pH in the poor fen resulted in 3.1 times greater methylmercury. Chapter 3, riparian zones in intermediate ...


Xzlamalraab_Clorg (2017).Pdf, Jaime Zlamal, Ted K. Raab, Robert A. Edwards, Mark Little, David A. Lipson 2017 San Diego State University

Xzlamalraab_Clorg (2017).Pdf, Jaime Zlamal, Ted K. Raab, Robert A. Edwards, Mark Little, David A. Lipson

Ted K. Raab

This   study   explores   biological  chlorine cycling in coastal Arctic wet tundra soils. While many previous chlorine-cycling studies have focused on contaminated environments, it is now recognized that chlorine can cycle naturally between inorganic and organic forms in soils. However, these pathways have not previously been
described for an Arctic ecosystem. We measured soil organic and inorganic Cl pools, characterized soils and plant tissues with chlorine K-edge X-ray absorption near-edge spectroscopy (Cl- XANES), measured dechlorination rates in laboratory incubations, and analyzed metagenomes and 16S rRNA genes along a chronosequence of revegetated drained lake basins. Concentrations of soil organic chlorinated compounds (Cl ...


Linking Organic Matter Dynamics To Management, Restoration, And Climate In The Florida Everglades, Peter Regier 2017 Florida International University

Linking Organic Matter Dynamics To Management, Restoration, And Climate In The Florida Everglades, Peter Regier

FIU Electronic Theses and Dissertations

The Florida Everglades is a massive and highly managed subtropical wetland ecosystem, strongly influenced by anthropogenic control of freshwater distribution and highly susceptible to a changing climate, including rising sea-level and changes in temperature and rainfall. Shifting hydrologic regimes impact ecosystem function and biogeochemistry, which in turn control the sources, fate, and transport of organic matter. As a master environmental variable, it is essential to understand how organic matter dynamics will respond to changes in the balance between freshwater and saltwater associated with landscape-scale Everglades restoration efforts and climate change. The research comprising this dissertation improves current understanding of the ...


Influence Of Common Bean (Phaseolus Vulgaris) Grown In Elevated Co2 On Apatite Dissolution, Brian Matthew Morra 2017 University of Maine

Influence Of Common Bean (Phaseolus Vulgaris) Grown In Elevated Co2 On Apatite Dissolution, Brian Matthew Morra

Electronic Theses and Dissertations

Elevated concentrations of atmospheric CO2 brought about by human activity creates changes in plant morphology, growth rate and exudate production. Our study sought to understand the effect of these changes on soil mineral weathering using plants grown under two conditions, ambient CO2 (400ppm) and elevated CO2 (1000ppm). Phaseolus vulgaris (common beans) were grown in flow-through microcosms consisting of a mixture of quartz and apatite sands. Plant growth was sustained by a nutrient solution devoid of calcium (Ca) and phosphorous (P). Using Atomic Adsorption Spectroscopy and colorimetry, Ca and P content of the leachate and plant tissue served ...


Summer Precipitation Occurrence Effect On Two Passerine Species In Thule, Greenland, Sara E. Baugh 2017 Augustana College, Rock Island Illinois

Summer Precipitation Occurrence Effect On Two Passerine Species In Thule, Greenland, Sara E. Baugh

Celebration of Learning

Climate change is occurring at a faster rate in the Arctic than the rest of the globe, causing temperature rises at twice the rate of the global average and increased summer precipitation in the form of rain. These precipitation events are predicted to affect migratory bird species that breed throughout the Arctic. Increased occurrence of heavy rainstorms indirectly affect bird populations by impacting distribution and abundance of food supply, and directly by increasing mortality rates of juveniles. Studies conducted on bird species throughout the low Arctic regions; have shown that it is not the total precipitation of a breeding season ...


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