Thomas Borch - Academia.edu (original) (raw)

Papers by Thomas Borch

Geochimica et Cosmochimica Acta, May 1, 2012

Microbial reduction of Fe(III) minerals at neutral pH is faced by the problem of electron transfe... more Microbial reduction of Fe(III) minerals at neutral pH is faced by the problem of electron transfer from the cells to the solid-phase electron acceptor and is thought to require either direct cell-mineral contact, the presence of Fe(III)-chelators or the presence of electron shuttles, e.g. dissolved or solid-phase humic substances (HS). In this study we investigated to which extent the ratio of Pahokee Peat Humic Acids (HA) to ferrihydrite in the presence and absence of phosphate influences rates of Fe(III) reduction by Shewanella oneidensis MR-1 and the identity of the minerals formed. We found that phosphate generally decreased reduction rates by sorption to the ferrihydrite and surface site blocking. In the presence of low ferrihydrite concentrations (5 mM), the addition of HA helped to overcome this inhibiting effect by functioning as electron shuttle between cells and the ferrihydrite. In contrast, at high ferrihydrite concentrations (30 mM), the addition of HA did not lead to an increase but rather to a decrease in reduction rates. Confocal laser scanning microscopy images and ferrihydrite sedimentation behaviour suggest that the extent of ferrihydrite surface coating by HA influences the aggregation of the ferrihydrite particles and thereby their accessibility for Fe(III)-reducing bacteria. We further conclude that in presence of dissolved HA, iron reduction is stimulated through electron shuttling while in the presence of only sorbed HA, no stimulation by electron shuttling takes place. In presence of phosphate the stimulation effect did not occur until a minimum concentration of 10 mg/l of dissolved HA was reached followed by increasing Fe(III) reduction rates up to dissolved HA concentrations of approximately 240 mg/l above which the electron shuttling effect ceased. Not only Fe(III) reduction rates but also the mineral products changed in the presence of HA. Sequential extraction, XRD and 57 Fe-Mö ssbauer spectroscopy showed that crystallinity and grain size of the magnetite produced by Fe(III) reduction in the presence of HA is lower than the magnetite produced in the absence of HA. In summary, this study shows that both the concentration of HA and Fe(III) minerals strongly influence microbial Fe(III) reduction rates and the mineralogy of the reduction products. Thus, deviations in iron (hydr)oxide reactivity with changes in aggregation state, such as HA induced ferrihydrite aggregation, need to be considered within natural environments.

Goldschmidt Abstracts, 2020

EarthArXiv (California Digital Library), Feb 6, 2020

It has been shown that reactive soil minerals, specifically iron(III) (oxyhydr)oxides, can trap o... more It has been shown that reactive soil minerals, specifically iron(III) (oxyhydr)oxides, can trap organic carbon in soils overlying intact permafrost, and may limit carbon mobilization and degradation as it is observed in other environments. However, the use of iron(III)-bearing minerals as terminal electron acceptors in permafrost environments, and thus their stability and capacity to prevent carbon mobilization during permafrost thaw, is poorly understood. We have followed the dynamic interactions between iron and carbon using a space-for-time approach across a thaw gradient in Abisko (Sweden), where wetlands are expanding rapidly due to permafrost thaw. We show through bulk (selective extractions, EXAFS) and nanoscale analysis (correlative SEM and nanoSIMS) that organic carbon is bound to reactive Fe primarily in the transition between organic and mineral horizons in palsa underlain by intact permafrost (41.8 ± 10.8 mg carbon per g soil, 9.9 to 14.8% of total soil organic carbon). During permafrost thaw, water-logging and O 2 limitation lead to reducing conditions and an increase in abundance of Fe(III)-reducing bacteria which favor mineral dissolution and drive mobilization of both iron and carbon along the thaw gradient. By providing a terminal electron acceptor, this rusty carbon sink is effectively destroyed along the thaw gradient and cannot prevent carbon release with thaw.

ACS earth and space chemistry, Feb 25, 2019

Organic matter complexation promotes Fe(II) oxidation by the photoautotrophic Fe(II)-oxidizer Rho... more Organic matter complexation promotes Fe(II) oxidation by the photoautotrophic Fe(II)-oxidizer Rhodopseudomonas palustris TIE-1

Environmental Science & Technology, Dec 14, 2009

Life and element cycling on Earth is directly related to electron transfer (or redox) reactions. ... more Life and element cycling on Earth is directly related to electron transfer (or redox) reactions. An understanding of biogeochemical redox processes is crucial for predicting and protecting environmental health and can provide new opportunities for engineered remediation strategies. Energy can be released and stored by means of redox reactions via the oxidation of labile organic carbon or inorganic compounds (electron donors) by microorganisms coupled to the reduction of electron acceptors including humic substances, iron-bearing minerals, transition metals, metalloids, and actinides. Environmental redox processes play key roles in the formation and dissolution of mineral phases. Redox cycling of naturally occurring trace elements and their host minerals often controls the release or sequestration of inorganic contaminants. Redox processes control the chemical speciation, bioavailability, toxicity, and mobility of many major and trace elements including Fe,

Environmental Science & Technology, Apr 19, 2018

Fe(II)-organic-matter (Fe(II)-OM) complexes are abundant in the environment and may play a key ro... more Fe(II)-organic-matter (Fe(II)-OM) complexes are abundant in the environment and may play a key role for the behavior of Fe and pollutants. Mixotrophic nitrate-reducing Fe(II)-oxidizing bacteria (NRFeOx) reduce nitrate coupled to the oxidation of organic compounds and Fe(II). Fe(II) oxidation may occur enzymatically or abiotically by reaction with nitrite that forms during heterotrophic denitrification. However, it is unknown whether Fe(II)-OM complexes can be oxidized by NRFeOx. We used cellsuspension experiments with the mixotrophic nitrate-reducing Fe(II)-oxidizing bacterium Acidovorax sp. strain BoFeN1 to reveal the role of non-organically-bound Fe(II) (aqueous Fe(II)) and nitrite for the rates and extent of oxidation of Fe(II)-OM-complexes (Fe(II)-citrate, Fe(II)-EDTA, Fe(II)-humic-acid, and Fe(II)fulvic-acid). We found that Fe(II)-OM complexation inhibited microbial nitrate-reducing Fe(II) oxidation; large colloidal and negatively charged complexes showed lower oxidation rates than aqueous Fe(II). Accumulation of nitrite and fast abiotic oxidation of Fe(II)-OM complexes only happened in the presence of aqueous Fe(II) that probably interacted with (nitrite-reducing) enzymes in the periplasm causing nitrite accumulation in the periplasm and outside of the cells, whereas Fe(II)-OM complexes probably could not enter the periplasm and cause nitrite accumulation. These results suggest that Fe(II) oxidation by mixotrophic nitrate-reducers in the environment depends on Fe(II) speciation, and that aqueous Fe(II) potentially plays a critical role in regulating microbial denitrification processes.

EGU General Assembly Conference Abstracts, Apr 1, 2017

Communications Earth & Environment, 2022

Reductive dissolution during permafrost thaw releases iron-bound organic carbon to porewaters, re... more Reductive dissolution during permafrost thaw releases iron-bound organic carbon to porewaters, rendering previously stable carbon vulnerable to microbial decomposition and subsequent release to the atmosphere. How mineral iron stability and the microbial processes influencing mineral dissolution vary during transitional permafrost thaw are poorly understood, yet have important implications for carbon cycling and emissions. Here we determine the reactive mineral iron and associated organic carbon content of core extracts and porewaters along thaw gradients in a permafrost peatland in Abisko, Sweden. We find that iron mineral dissolution by fermentative and dissimilatory iron(III) reduction releases aqueous Fe2+ and aliphatic organic compounds along collapsing palsa hillslopes. Microbial community analysis and carbon emission measurements indicate that this release is accompanied by an increase in hydrogenotrophic methanogen abundance and methane emissions at the collapsing front. Our...

Wetlands cover less than 10% of Earth’s land surface area, but contain about one third of the pla... more Wetlands cover less than 10% of Earth’s land surface area, but contain about one third of the planet’s soil carbon (C). The residence times of water through wetlands influence their redox conditions and thus biogeochemical reaction rates and the supply and removal of C and nutrients. In these environments, transformation and movement of C and iron (Fe) are closely linked due to the sequestration of organic C by solid Fe(III) phases. We investigated how temperature influences microbial Fe(III) reduction kinetics and the consequences on the mobilization and retention of dissolved organic carbon (DOC) in subalpine wetland soils. We studied a slope wetland and a depressional wetland (USDA Fraser Experimental Forest, CO, USA) that each provides a redox gradient from constantly reducing soils to soils undergoing redox fluctuations. We investigated the effects of temperature on potential Fe(III) reduction rates and DOC release rates, as well as on the kinetics of Fe(III) reduction (maximum...

Cost metrics can include levelized costs of water treatment as well as individual cost components... more Cost metrics can include levelized costs of water treatment as well as individual cost components, such capital or operations and maintenance (O&M) costs. Energy Performance Energy performance metrics can include the total energy requirements of the water treatment process, the type of energy required (e.g., thermal vs. electricity), embedded energy in chemicals and materials, and the degree to which alternative energy resources are utilized. Water Treatment Performance Water treatment performance metrics can include the percent removal of various contaminants of concern and the percent recovery of water from the treatment train. Human Health and Environment Externalities Externality metrics can include air emissions, greenhouse gas emissions, waste streams, societal and health impacts, land-use impacts. Process Adaptability Process adaptability metrics can include the ability to incorporate variable input water qualities, the ability to incorporate variable input water quantity flows, the ability to produce variable output water quality, and the ability to operate flexibly in response to variable energy inputs.

Irrigation accounts for 42% of the total freshwater withdrawals in the United States. Climate cha... more Irrigation accounts for 42% of the total freshwater withdrawals in the United States. Climate change, the pressure of a growing population, degrading water quality, and increased competition from other sectors could constrain continuous supply to meet future agricultural water demand. This study presents an evaluation framework to assess the potential reuse of agricultural drainage water for crop irrigation. Using a regional approach, we review the current state of agricultural drainage treatment and reuse and the institutional, economic, and other barriers that can influence the reuse decision. In the 31 eastern states, agricultural drainage contains valuable nutrients that can be reused for irrigation with minimal treatment, while the 17 western states struggle with large volumes of saline drainage that can contain constituents of concern (e.g., selenium), preventing reuse without treatment. Using a new decision-support tool called WaterTAP3, a potential treatment train for saline agricultural drainage was analyzed to identify treatment challenges, research needs, and the potential implementation at a larger scale. As demonstrated by our case study, desalination of agricultural drainage is costly and energy intensive and will require sizable investments to fully develop and optimize technologies as well as manage the generated waste and brine.

I n t r o d u c t I o n Clean water is critical to ensure good health, strong communities, vibran... more I n t r o d u c t I o n Clean water is critical to ensure good health, strong communities, vibrant ecosystems, and a functional economy for manufacturing, farming, tourism, recreation, energy production, and other sectors' needs. Research to improve desalination technologies can make nontraditional sources of water (i.e., brackish water; seawater; produced and extracted water; and power sector, industrial, municipal, and agricultural wastewaters) a cost-effective alternative. These nontraditional sources can then be applied to a variety of beneficial end uses, such as drinking water, industrial process water, and irrigation, expanding the circular water economy by reusing water supplies and valorizing constituents we currently consider to be waste. As an added benefit, these water supplies could contain valuable constituents that could be reclaimed to further a circular economy. I n t r o d u c t I o n 1.2. Pipe-Parity and Baseline Definitions A core part of NAWI's vision of a circular water economy is reducing the cost of treating nontraditional source waters to the same range as the portfolio of accessing new traditional water sources, essentially achieving pipe-parity. The costs considered are not just economic but include consideration of energy consumption, system reliability, water recovery, and other qualitative factors that affect the selection of a new water source. To effectively assess R&D opportunities, pipeparity metrics are utilized; they encompass a variety of information that is useful to decision makers regarding investments related to different source water types. Pipe-parity is defined as technological and non-technological solutions and capabilities that make marginal water sources viable for end-use applications. Like the concept of grid parity (where an alternative energy source generates power at a levelized cost of electricity [LCOE] that is less than or equal to the price of power from the electricity grid), a nontraditional water source achieves pipe-parity when a decision maker chooses it as their best option for extending its water supply. Specific pipe-parity metrics of relevance can include: Cost Cost metrics can include levelized costs of water treatment as well as individual cost components, such as capital or operational and maintenance (O&M) costs. Energy Performance Energy performance metrics can include the total energy requirements of the water treatment process, the type of energy required (e.g., thermal vs. electricity), embedded energy in chemicals and materials, and the degree to which alternative energy resources are utilized. Water Treatment Performance Water treatment performance metrics can include the percent removal of various constituents of concern and the percent recovery of water from the treatment train. Human Health and Environment Externalities Externality metrics can include air emissions, greenhouse gas emissions, waste streams, societal and health impacts, and land-use impacts. Process Adaptability Process adaptability metrics can include the ability to incorporate variable input water qualities, incorporate variable input water quantity flows, produce variable output water quality, and operate flexibly in response to variable energy inputs. I n t r o d u c t I o n Seawater and Ocean Water Water from the ocean or from bodies strongly influenced by ocean water, including bays and estuaries, with a typical total dissolved solids (TDS) between 30,000 and 35,000 milligrams per liter (mg/L). Brackish Groundwater Water pumped from brackish aquifers, with particular focus on inland areas where brine disposal is limiting. Brackish water generally is defined as water with 1-10 grams per liter (g/L) of total dissolved solids (TDS). Industrial Wastewater Water from various industrial processes that can be treated for reused Municipal Wastewater Wastewater treated for reuse through municipal resource recovery treatment plants utilizing advanced treatment processes or decentralized treatment systems Agricultural Wastewater Wastewater from tile drainage, tailwater, and other water produced on irrigated croplands, as well as wastewater generated during livestock management, that can be treated for reuse or disposal Mining Wastewater Wastewater from mining operations that can be reused or prepared for disposal Produced Water Water used for or produced by oil and gas exploration activities (including fracking) that can be reused or prepared for disposal Power and Cooling Wastewater Water used for cooling or as a byproduct of treatment (e.g., flue gas desulfurization) that can be reused or prepared for disposal These nontraditional water sources range widely in TDS (100 milligrams per liter [mg/L]-800,000 mg/L total) as well as the type and concentrations of contaminants (e.g., nutrients, hydrocarbons, organic compounds, metals). These different water supplies require varying degrees of treatment to reach reusable quality.

Chemical Engineering Journal, 2021

Abstract Per- and polyfluoroalkyl substances (PFAS) are a class of compounds that have become env... more Abstract Per- and polyfluoroalkyl substances (PFAS) are a class of compounds that have become environmental contaminants of emerging concern. They are highly persistent, toxic, bioaccumulative, and ubiquitous which makes them important to detect to ensure environmental and human health. Multiple instrument-based methods exist for sensitive and selective detection of PFAS in a variety of matrices, but these methods suffer from expensive costs and the need for a laboratory and highly trained personnel. There is a big need for fast, inexpensive, robust, and portable methods to detect PFAS in the field. This would allow environmental laboratories and other agencies to perform more frequent testing to comply with regulations. In addition, the general public would benefit from a fast method to evaluate the drinking water in their homes for PFAS contamination. A PFAS sensor would provide almost real-time data on PFAS concentrations that can also provide actionable information for water quality managers and consumers around the planet. In this review, we discuss the sensors that have been developed up to this point for PFAS detection by their molecular detection mechanism as well as the goals that should be considered during sensor development. Future research needs and commercialization challenges are also highlighted.

Science of The Total Environment, 2020

Produced water is the largest waste stream associated with oil and gas operations. This complex f... more Produced water is the largest waste stream associated with oil and gas operations. This complex fluid contains petroleum hydrocarbons, heavy metals, salts, naturally occurring radioactive materials and any remaining chemical additives. In the United States, west of the 98th meridian, the federal National Pollutant Discharge Elimination System (NPDES) exemption allows release of produced water for agricultural beneficial reuse. The goal of this study was to quantify mutagenicity of a produced water NPDES release and discharge stream. We used four mutation assays in budding yeast cells that provide rate estimates for copy number variation (CNV) duplications and deletions, as well as forward and reversion point mutations. Higher mutation rates were observed at the discharge and decreased with distance downstream, which correlated with the concentrations of known carcinogens detected in the stream (e.g., benzene, radium), described in a companion study. Mutation rate increases were most prominent for CNV duplications and were *