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Biocatalysis has rapidly become an essential tool in the scientific and industrial communities for the development of efficient, safe, and sustainable chemical syntheses. Immobilization of the biocatalyst, typically an engineered enzyme, offers significant advantages, including increased enzyme stability and control, resistance to environmental change, and enhanced reusability. Determination and optimization of the spatial and chemical distribution of immobilized enzymes are critical for proper functionality; however, analytical methods currently employed for doing so are frequently inadequate. Machine learning, in the form of multivariate curve resolution, with Raman hyperspectral imaging is presented herein as a potential method for investigating the spatial and chemical distribution of evolved pantothenate kinase immobilized onto two diverse, microporous resins. An exhaustive analysis indicates that this method can successfully resolve, both spatially and spectrally, all chemical species involved in enzyme immobilization, including the enzyme, both resins, and other key components. Quantitation of the spatial coverage of immobilized enzymes, a key parameter used for process development, was accomplished. Optimal analytical parameters were determined by the evaluation of different excitation wavelengths. Exploratory chemometric approaches, including principal component analysis, were utilized to investigate the chemical species embedded within the data sets and their relationships. The totality of this information can be utilized for an enhanced understanding of enzyme immobilization processes and can allow for the further implementation of biocatalysis within the scientific and pharmaceutical communities.

Recent advances in biocatalysis and directed enzyme evolution has led to a variety of enzymatically-driven, elegant processes for active pharmaceutical ingredient (API) production. For biocatalytic processes, quantitation of any residual protein within a given API is of great importance to ensure process robustness and quality, pure pharmaceutical products. Typical analytical methods for analyzing residual enzymes within an API, such as enzyme-linked immunosorbent assays (ELISA), colorimetric assays, and liquid chromatographic techniques, are limited for determining only the concentration of known proteins and require harsh solvents with high API levels for analysis. For the first time, total residual protein content in a small molecule API was quantitated using image analysis applied to SDS-PAGE. Herein, a proposed methodology for residual protein detection, quantitation, and size-based speciation is presented, in which an orthogonal technique is offered to traditional analysis methods, such as ELISA. Results indicate that our application of the analytical methodology is able to reliably quantitate both protein standards and the total residual protein present within a final API, with good agreement as compared to traditional ELISA results. Further, speciation of the residual protein within the API provides key information concerning the individual residual proteins present, including their molecular weight, which can lead to improved process development efforts for residual protein rejection and control. This analytical methodology thus offers an alternative tool for easily identifying, quantitating, and speciating residual protein content in the presence of small molecule APIs, with potential for wide applicability across industry for biocatalytic or directed enzyme evolution efforts within process development.

Municipal wastewater (MWW) effluent discharges can introduce contaminants to receiving waters which may have adverse impacts on local ecosystems and human health. Conservative chemical constituents specific to the MWW effluent stream can be used to quantify and trace wastewater effluent-sourced contaminant inputs. Gadolinium (Gd), a rare earth element used as a contrasting agent in medical magnetic resonance imaging, can be found in urban MWW streams. Dissolved anthropogenic Gd has been shown to be an indicator and potential conservative tracer for MWW effluent in receiving waters. Like other known MWW tracers, it can be difficult and expensive to measure. Dissolved rubidium (Rb) to strontium (Sr) ratio enrichment in biological materials such as blood and urine can lead to enriched Rb/Sr values in MWW effluent relative to natural waters. This ratio is relatively easy and inexpensive to measure and represents a promising additional indicator for MWW effluent in receiving waters in urbanized freshwater systems. In July 2015 and 2016 surface water samples were collected from sites in the tidal-fresh Potomac River in the vicinity of the Blue Plains Advanced Wastewater Treatment Plant (BPAWWTP) outfall near Washington, DC USA along with treated MWW effluent samples from the BPAWWTP. Dissolved Rb/Sr ratios were measured in these waters and compared to dissolved Gd concentrations in order to demonstrate the potential of the dissolved Rb/Sr ratio as a conservative indicator for MWW effluent. Results suggest the dissolved Rb/Sr ratio represents a simple and cost-effective indicator and conservative tracer for MWW effluent. It can be used with, or in place of, other proven tracers to investigate wastewater impacts in highly-urbanized, anthropogenically-impacted freshwater systems like the tidal fresh Potomac River and perhaps in a wider range of geologic settings than previously thought. A case study is presented as an example to demonstrate the potential of using dissolved Rb/Sr ratios to trace MWW-sourced nutrient inputs from a major WWTP like BPAWWTP to the receiving waters of tidal-fresh Potomac River.

Methane is touted as a replacement for fossil fuels in transport applications due to its lower costs of production and cleaner combustion. Storage of methane is still a problem and different technologies have been considered, including compression and liquefaction. Adsorption in a porous material is a potential alternative for methane storage, as it can increase densities at moderate pressures and temperatures. For practical applications, in addition to the quantities stored and working capacities, it is important to equally consider aspects such as kinetics of storage and thermal management of the storage system. In this paper, the kinetics and enthalpies of adsorption of methane in activated carbons AX-21 and TE7, and metal-organic framework MIL-101 (Cr) are extracted from readily available gas sorption data. The adsorption kinetics at 300 K and 325 K are analysed and fitted with the linear driving force (LDF) model, and mass transfer coefficients (MTC) and effective diffusivities are estimated. The effective diffusivities have a range of values from 1.79 × 10−13 m2 s−1 for the MIL-101 (Cr) at 300 K to 9.36 × 10−10 m2 s−1 for the TE7 at 325 K. The activation energies for the effective diffusivities based on an Arrhenius-type temperature dependence are calculated as 7.42, 7.09 and 5.38 kJ mol−1 for the AX-21, the MIL-101 (Cr) and the TE7, respectively. The enthalpies of adsorption are calculated with the Clausius-Clapeyron equation and the differences observed when calculating these with excess and absolute amounts are presented and discussed, with the results showing that enthalpies can have up to 10% differences if using excess amounts instead of absolute quantities. The isosteric enthalpies are also compared with enthalpies at zero-coverage obtained from differential calorimetry experiments for the MIL-101 (Cr), and a ∼3.5 kJ mol−1 difference is observed, which underlines the importance of refining calculation methods and bridging the gap between direct and indirect methods for calculating enthalpies of adsorption.

Directed enzyme evolution has led to significant application of biocatalysis for improved chemical transformations throughout the scientific and industrial communities. Biocatalytic reactions utilizing evolved enzymes immobilized within microporous supports have realized unique advantages, including notably higher enzyme stability, higher enzyme load, enzyme reusability, and efficient product-enzyme separation. To date, limited analytical methodology is available to discern the spatial and chemical distribution of immobilized enzymes, in which techniques for surface visualization, enzyme stability, or activity are instead employed. New analytical tools to investigate enzyme immobilization are therefore needed. In this work, development, application, and evaluation of an analytical methodology to study enzyme immobilization is presented. Specifically, Raman hyperspectral imaging with principal component analysis, a multivariate method, is demonstrated for the first time to investigate evolved enzymes immobilized onto microporous supports for biocatalysis. Herein we demonstrate the ability to spatially and spectrally resolve evolved pantothenate kinase (PanK) immobilized onto two commercially-available, chemically-diverse porous resins. This analytical methodology is able to chemically distinguish evolved enzyme, resin, and chemical species pertinent to immobilization. As such, a new analytical approach to study immobilized biocatalysts is demonstrated, offering potential wide application for analysis of protein or biomolecule immobilization.

The use of protection groups to shield a functional group during a synthesis is employed throughout many reactions and organic syntheses. The role of a protection group can be vital to the success of a reaction, as well as increase reaction yield and selectivity. Although much work has been done to investigate the addition of a protection group, the removal of the protection group is just as important – however, there is a lack of methods employed within the literature for monitoring the removal of a protection group in real time. In this work, the process of removing, or deprotecting, a ketal protecting group is investigated. Process analytical technology tools are incorporated for in situ analysis of the deprotection reaction of a small molecule model compound. Specifically, Raman spectroscopy and Fourier transform infrared spectroscopy show that characteristic bands can be used to track the decrease of the reactant and the increase of the expected products over time. To the best of our knowledge, this is the first report of process analytical technology being used to monitor a ketal deprotection reaction in real time. This information can be capitalized on in the future for understanding and optimizing pharmaceutically-relevant deprotection processes and downstream reactions.

Graphenic sponges have created tantamount interest due to their special affinity for absorbing a broad range of petroleum oils and solvents resulting from controllable surface wettability. A major challenge is to fabricate such materials with surface hydrophilicity coexisting with hydrophobicity. Herein, we report a scalable self-assembly of randomly oriented improved graphene oxide (IGO) sheets into a graphene oxide sponge (GOS-H) with uniform cylindrical shape via a hydrothermal method. Extensive characterization of GOS-H using Raman microspectroscopy, Raman imaging, X-ray photoelectron spectroscopy (XPS), and electron microscopic (SEM and HRTEM) techniques suggests the sponge surface is hydrophobic with some hydrophilic oxygen content and has defect sites and roughness associated with voids formation. These features and conformal C–O coating on the basal plans result in high-diesel-range alkanes absorption from pure alkanes as well as from alkane–water mixture, which could enable as-synthesized GOS-H a...

Analysis of the spatial distribution of metals, metalloids, and non-metals in biological tissues is of significant interest in the life sciences, helping to illuminate the function and roles these elements play within various biological pathways. Chemical imaging methods are commonly employed to address biological questions and reveal individual spatial distributions of analytes of interest. Elucidation of these spatial distributions can help determine key elemental and molecular information within the respective biological specimens. However, traditionally utilized imaging methods prove challenging for certain biological tissue analysis, especially with respect to applications that require high spatial resolution or depth profiling. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has been shown to be effective for direct elemental analysis of solid materials with high levels of precision. In this work, chemical imaging using LA-ICP-MS has been applied as a powerful analytical methodology for the analysis of liver tissue samples. The proposed analytical methodology successfully produced both qualitative and quantitative information regarding specific elemental distributions within images of thin tissue sections with high levels of sensitivity and spatial resolution. The spatial resolution of the analytical methodology was innovatively enhanced, helping to broaden applicability of this technique to applications requiring significantly high spatial resolutions. This information can be used to further understand the role these elements play within biological systems and impacts dysregulation may have.

The recent identification of the high-pressure, α-PbO 2 -structured polymorph of titanium dioxide, TiO 2 -II, in grains recovered from four Neoarchean spherule layers has provided physical evidence to further support an impact origin of these layers. Smith et al. (2017) investigated these TiO 2 -II-bearing grains using Raman microspectroscopic mapping with multivariate curve resolution-alternating least squares (MCR-ALS) to spatially and spectrally resolve the individual chemical species within the grains. Here we provide the Raman microspectroscopic mapping data collected on the TiO 2 -II-bearing grains. We further provide chemical maps, chemical images and Raman spectra of rutile, TiO 2 -II, anatase, quartz, and substrate-adhesive epoxy that were resolved using MCR-ALS applied to the Raman microspectroscopic mapping data. The Raman microspectroscopic mapping data in this work—collected using both high spectral resolution and high spatial resolution—provides a myriad of opportunities for the scientific community in wide ranging applications, including the chemical imaging and chemometric disciplines.

Cu-exchanged small-pore zeolites (CHA and AEI) form methanol from methane (>95% selectivity) using a 3-step cyclic procedure (Wulfers et al. Chem. Commun. 2015, 51, 4447−4450) with methanol amounts higher than Cu-ZSM-5 and Cu-mordenite on a per gram and per Cu basis. Here, the CuxOy species formed on Cu-SSZ-13 and Cu-SSZ-39 following O2 or He activation at 450 °C are identified as trans-μ-1,2-peroxo dicopper(II) ([Cu2O2]2+) and mono-(μ-oxo) dicopper(II) ([Cu2O]2+) using synchrotron X-ray diffraction, in situ UV–vis, and Raman spectroscopy and theory. [Cu2O2]2+ and [Cu2O]2+ formed on Cu-SSZ-13 showed ligand-to-metal charge transfer (LMCT) energies between 22,200 and 35,000 cm–1, Cu–O vibrations at 360, 510, 580, and 617 cm–1 and an O–O vibration at 837 cm–1. The vibrations at 360, 510, 580, and 837 cm–1 are assigned to the trans-μ-1,2-peroxo dicopper(II) species, whereas the Cu–O vibration at 617 cm–1 (Δ18O = 24 cm–1) is assigned to a stretching vibration of a thermodynamically favored mono-(μ-oxo) dicoppe...

The high-pressure, α-PbO2-structured polymorph of titanium dioxide (TiO2-II) was recently identified in micrometer-sized grains recovered from four Neoarchean spherule layers deposited between ∼2.65 and ∼2.54 billion years ago. Several lines of evidence support the interpretation that these layers represent distal impact ejecta layers. The presence of shock-induced TiO2-II provides physical evidence to further support an impact origin for these spherule layers. Detailed characterization of the distribution of TiO2-II in these grains may be useful for correlating the layers, estimating the paleodistances of the layers from their source craters, and providing insight into the formation of the TiO2-II. Here we report the investigation of TiO2-II-bearing grains from these four spherule layers using multivariate curve resolution–alternating least squares (MCR-ALS) applied to Raman microspectroscopic mapping. Raman spectra provide evidence of grains consisting primarily of rutile (TiO2) and TiO2-II, as shown by Raman bands at 174 cm–1 (TiO2-II), 426 cm–1 (TiO2-II), 443 cm–1 (rutile), and 610 cm–1 (rutile). Principal component analysis (PCA) yielded a predominantly three-phase system comprised of rutile, TiO2-II, and substrate-adhesive epoxy. Scanning electron microscopy (SEM) suggests heterogeneous grains containing polydispersed micrometer- and submicrometer-sized particles. Multivariate curve resolution–alternating least squares applied to the Raman microspectroscopic mapping yielded up to five distinct chemical components: three phases of TiO2 (rutile, TiO2-II, and anatase), quartz (SiO2), and substrate-adhesive epoxy. Spectral profiles and spatially resolved chemical maps of the pure chemical components were generated using MCR-ALS applied to the Raman microspectroscopic maps. The spatial resolution of the Raman microspectroscopic maps was enhanced in comparable, cost-effective analysis times by limiting spectral resolution and optimizing spectral acquisition parameters. Using the resolved spectra of TiO2-II generated from MCR-ALS analysis, a Raman spectrum for pure TiO2-II was estimated to further facilitate its identification.

The emergence of stretchable electronic devices has attracted intensive attention. However, most of the existing stretchable electronic devices can generally be stretched only in one specific direction and show limited specific capacitance and energy density. Here, we report a stretchable isotropic buckled carbon nanotube (CNT) film, which is used as electrodes for supercapacitors with low sheet resistance, high omnidirectional stretchability, and electro-mechanical stability under repeated stretching. After acid treatment of the CNT film followed by electrochemical deposition of polyaniline (PANI), the resulting isotropic buckled acid treated CNT@PANI electrode exhibits high specific capacitance of 1147.12 mF cm(-2) at 10 mV s(-1). The supercapacitor possesses high energy density from 31.56 to 50.98 μWh cm(-2) and corresponding power density changing from 2.294 to 28.404 mW cm(-2) at the scan rate from 10 to 200 mV s(-1). Also, the supercapacitor can sustain an omnidirectional strain of 200%, which is twice the maximum strain of biaxially stretchable supercapacitors based on CNT assemblies reported in the literature. Moreover, the capacitive performance is even enhanced to 1160.43-1230.61 mF cm(-2) during uniaxial, biaxial, and omnidirectional elongations.

Graphene films fabricated by chemical vapor deposition are promising electrode materials for stretchable energy storage devices. The buckled four-layer graphene on a polydimethylsiloxane film substrate subject to various applied tensile strains has been characterized by atomic force microscopy and micro-Raman mapping. The small redshift of 2D band and the indiscernible D band demonstrated that the tensile strains of up to 40% only induced a strain variation of less than 0.2% and did not cause any observable damage in the graphene film. This study has confirmed that the graphene film in the buckled state is suitable for its application as a stretchable electrode.

Medically derived (131)I (t1/2 = 8.04 d) is discharged from water pollution control plants (WPCPs) in sewage effluent. Iodine's nutrient-like behavior and the source-specificity of (131)I make this radionuclide a potentially valuable tracer in wastewater nitrogen studies. Iodine-131 was measured in Potomac River water and sediments in the vicinity of the Blue Plains WPCP, Washington, DC, USA. Dissolved (131)I showed a strong, positive correlation with δ(15)N values of nitrate (δ(15)NO3(-)) in the river, the latter being a traditional indicator of nutrient inputs and recycling. Surface water δ(15)NO3(-) values ranged from 8.7 to 33.4‰; NO3(-) + NO2(-) concentrations were 0.39-2.79 mg N L(-1) (26-186 μM). Sediment profiles of particulate (131)I and δ(15)N indicate rapid mixing or sedimentation and in many cases remineralization of a heavy nitrogen source consistent with wastewater nitrogen. Values of δ(15)N in sediments ranged from 4.7 to 9.3‰. This work introduces (131)I as a tool to investigate the short-term fate of wastewater nitrogen in the Potomac River and demonstrates the general utility of (131)I in aquatic research.

In September 2009, a series of sediment cores were collected across the Alaskan Beaufort Sea shelf-slope. Sediment and porewater organic carbon (OC) concentrations and stable carbon isotope ratios (δ13C) were measured to investigate spatial variations in sediment organic matter (OM) sources and distribution of these materials across the shelf. Cores were collected along three main nearshore (shelf) to offshore (slope) sampling lines (transects) from east-to-west along the North Slope of Alaska: Hammerhead (near Camden Bay), Thetis Island (near Prudhoe Bay), and Cape Halkett (towards Point Barrow). Measured sediment organic carbon (TOC) and porewater dissolved organic carbon (DOC) concentrations and their respective δ13C values were used to investigate the relative contribution of different OM sources to sediment OC pool cycled at each location. Sources of OM considered included: water column-sourced phytodetritus, deep sediment methane (CH4), and terrestrial, tundra/river-sourced OM. Results of these measurements, when coupled with results from previous research and additional analyses of sediment and porewater composition, show a pattern of spatial variation in sediment OC concentrations, OM source contributions, and OM cycled along the Alaskan Beaufort Sea shelf. In general, measured sediment total organic carbon (TOC) concentrations, δ13CTOC values, porewater DOC concentrations, and δ13CDOC values are consistent with an east-to-west transport of modern Holocene sediments with higher OC concentrations primarily sourced from relatively labile terrestrial, tundra OM sources and phytodetritus along the Alaskan Beaufort shelf. Sediment transport along the shelf results in the medium-to-long term accumulation and burial of sediment OM focused to the west which in turn results in higher biogenic CH4 production rates and higher upward CH4 diffusion through the sediments resulting in CH4−AMO-sourced contribution to sediment OC westward along the shelf. Understanding current OM sources and distributions along the Alaskan Beaufort shelf is important for enhancing models of carbon cycling in Arctic coastal shelf systems. This will help support the prediction of the climate response of the Arctic created in the face of future warming scenarios.

Rigorous evaluation of ballast water management systems (BMWSs) at land-based test facilities requires that water used in testing meets minimum concentrations of dissolved and particulate material, for example, using the criteria in the U.S Environmental Technology Verification (ETV) Program's protocol for testing of BWMSs. Here, uptake water ("challenge water") can be augmented with compounds to meet these benchmarks. In this study, we evaluated materials used to supplement dissolved organic matter (DOM), particulate organic matter (POM), and mineral matter (MM) used to achieve challenge water criteria. To determine the additives' contributions to DOM and POM pools, the mass yields of Camellia sinesis (decaffeinated iced tea) extract and humic matter were calculated at different temperature and salinities. Additionally, the response of ambient organisms to these additives was measured in mesocosm experiments, in which changes in organism concentrations were measured after a 5-d holding time. Living organisms were grouped into three size classes: ≥50 µm (nominally zooplankton), ≥10 to

Moderate elevated vertical methane (CH 4 ) flux is associated with sediment accretion and raised fluid expulsion at the Hikurangi subduction margin, located along the northeast coast of New Zealand. This focused CH 4 flux contributes to the cycling of inorganic and organic carbon in solid phase sediment and pore water. Along a 7 km offshore transect across the Porangahau Ridge, vertical CH 4 flux rates range from 11.4 mmol·m −2 ·a −1 off the ridge to 82.6 mmol·m −2 ·a −1 at the ridge base. Stable carbon isotope ratios (δ 13 C) in pore water and sediment were variable across the ridge suggesting close proximity of heterogeneous carbon sources. Methane stable carbon isotope ratios ranging from −107.9‰ to −60.5‰ and a C1:C2 of 3000 indicate a microbial, or biogenic, source. Near ridge, average δ 13 C for pore water and sediment inorganic carbon were 13 C-depleted (−28.7‰ and −7.9‰, respectively) relative to all core subsamples (−19.9‰ and −2.4‰, respectively) suggesting localized anaerobic CH 4 oxidation and precipitation of authigenic carbonates. Through the transect there was low contribution from anaerobic oxidation of CH 4 to organic carbon pools; for all cores δ 13 C values of pore water dissolved organic carbon and sediment organic carbon averaged −24.4‰ and −22.1‰, respectively. Anaerobic oxidation of CH 4 contributed to pore water and sediment organic carbon near the ridge as evidenced by carbon isotope values as low as to −42.8‰ and −24.7‰, respectively. Carbon concentration and isotope analyses distinguished contributions from CH 4 and phytodetrital carbon sources across the ridge and show a low methane contribution to organic carbon.

In June 2007 sediment cores were collected in Alaminos Canyon, Gulf of Mexico across a series of seismic data profiles indicating rapid transitions between the presence of methane hydrates and vertical gas flux. Vertical profiles of dissolved sulfate, chloride, calcium, magnesium, and dissolved inorganic carbon (DIC) concentrations in porewaters, headspace methane, and solid phase carbonate concentrations were measured at each core location to investigate the cycling of methane-derived carbon in shallow sediments overlying the hydrate bearing strata. When integrated with stable carbon isotope ratios of DIC, geochemical results suggest a significant fraction of the methane flux at this site is cycled into the inorganic carbon pool. The incorporation of methane-derived carbon into dissolved and solid inorganic carbon phases represents a significant sink in local carbon cycling and plays a role in regulating the flux of methane to the overlying water column at Alaminos Canyon. Targeted, high-resolution geochemical characterization of the biogeochemical cycling of methane-derived carbon in shallow sediments overlying hydrate bearing strata like those in Alaminos Canyon is critical to quantifying methane flux and estimating methane hydrate distributions in gas hydrate bearing marine sediments.

The MITAS (Methane in the Arctic Shelf/Slope) expedition was conducted during September, 2009 onboard the U.S. Coast Guard Cutter (USCGC) Polar Sea (WAGB-11), on the Alaskan Shelf/Slope of the Beaufort Sea. Expedition goals were to investigate spatial variations in methane source(s), vertical methane flux in shallow sediments ( δ 13 C CH 4 values ranged from −138 to −48‰, suggesting strong differences in shallow sediment CH4 cycling within and among sample locations. Measured porewater DIC concentrations ranged from 2.53 mM to 79.39 mM with δ13CDIC values ranging from −36.4‰ to 5.1‰. Higher down-core DIC concentrations were observed to occur with lower δ13C where an increase in δ 13 C CH 4 was measured, indicating locations with active anaerobic oxidation of methane. Shallow core CH4 production was inferred at the two western most transects (i.e. Thetis Island and Halkett) through observations of low δ 13 C CH 4 coupled with elevated DIC concentrations. At the easternmost Hammerhead transect and offshore locations, δ 13 C CH 4 and DIC concentrations were not coupled suggesting less rapid methane cycling. Results from the MITAS expedition represent one of the most comprehensive studies of methane source(s) and vertical methane flux in shallow sediments of the U.S. Alaskan Beaufort Shelf to date and show geospatially variable sediment methane flux that is highly influenced by the local geophysical environment.

Coastal methane hydrate deposits are globally abundant. There is a need to understand the deep sediment sourced methane energy contribution to shallow sediment carbon relative to terrestrial sources and phytoplankton. Shallow sediment and porewater samples were collected from Atwater Valley, Texas-Louisiana Shelf, Gulf of Mexico near a seafloor mound feature identified in geophysical surveys as an elevated bottom seismic reflection. Geochemical data revealed off-mound methane diffusion and active fluid advection on-mound. Gas composition (average methane/ethane ratio ~11,000) and isotope ratios of methane on the mound (average δ13CCH4(g) = −71.2‰, D14CCH4(g) = −961‰) indicate a deep sediment, microbial source. Depleted sediment organic carbon values on mound (δ13CSOC = −25.8‰, D14CSOC = −930‰) relative to off-mound (δ13CSOC = −22.5‰, D14CSOC = −629‰) suggest deep sourced ancient carbon is incorporated into shallow sediment organic matter. Porewater and sediment data indicate inorganic carbon fixed during anaerobic oxidation of methane is a dominant contributor to on-mound shallow sediment organic carbon cycling. A simple stable carbon isotope mass balance suggests carbon fixation of dissolved inorganic carbon (DIC) associated with anaerobic oxidation of hydrate-sourced CH4 contributes up to 85% of shallow sediment organic carbon.

Triclosan is an antimicrobial agent added to a wide array of consumer goods and personal care products. Through its use, it is introduced into municipal sewer systems where it is only partially removed during wastewater treatment. In this study, triclosan was measured in dated sediment cores from four urbanized estuaries in order to reconstruct temporal and spatial trends of accumulation. Measurable concentrations of triclosan first appeared in each of the sediment cores near 1964, which corresponds with the US patent issuance date of triclosan. The presence of triclosan at each of the study sites at or near the patent date indicates that long-term preservation is occurring in estuarine sediments. Temporal trends of triclosan at each location are unique, reflecting between site variability. Concentrations at one site climbed to as high as 400 ng g−1, due in part, to local commercial production of triclosan. At two locations, levels of triclosan rise towards the surface of each core, suggesting increasing usage in recent years. One location adjacent to a major combined sewer overflow had high sediment concentrations of triclosan, confirming their potential as a source of triclosan to estuaries.

This paper reviews scientific information on chemical forms and fate in the marine environment of mercury associated with drilling fluid barite. Overall, the available evidence supports the conclusions that mercury associated with drilling-fluid barite: (1) is mainly present in metal sulfides with very low solubility, (2) is not detectably leached into seawater, and (3) has limited availability to marine organisms. Reported mercury concentrations in barite from diverse sources range from

The effect of aromatic solute deuteration on the time dependence of fluorescence detected magnetic resonance (FDMR) of radical ion paris produced in cyclohexane solutions by pulse radiolysis shows that the rate of hyperfine induced S-To mixing influences the FDMR intensity up to 100 ns after application of a microwave pulse.

Time-resolved fluorescence-detected EPR studies of electron-irradiated solutions of 2,5-diphenyloxazole (PPO) in alkane solvents have shown that there are two distinct germinate radical ion pairs, distinguished by their lifetimes and EPR spectra. While the central EPR peak belongs to the aromatic radical ions, the broader components are assigned to the parent radical cation of the alkane solvent. Analysis of the resolved hyperfine structure indicates the presence of a trapped solvent hole in cyclohexane, which does not undergo unusually rapid charge exchange. The kinetic analyses of the EPR spectra show that scavenging events preserve the relative orientation of the unpaired electron spins in these geminate ion pairs.

Excited-state production and radical ion recombination kinetics in pulse-irradiated solutions of aromatic solutes in cyclohexane were studied by a new method of optical detection of time-resolved electron paramagnetic resonance (EPR) spectra. The EPR spectra of radical ion pairs which recombine to yield excited solute singlets were detected by the resonant decrease in fluorescence intensity occurring after application of a single (30 to 500 ns) microwave pulse. Fluorescence detection of magnetic resonance (FDMR) was used to obtain EPR spectra of radical ion pairs with lifetimes between 0.02 and 1.4 ..mu..s at solute concentrations of 10/sup -5/ to 10/sup -1/M. The decay rate of the FDMR intensity observed for 10/sup -3/ M solutions of 2,5-diphenyloxazole (PPO) was independent of radiation dose over a wide range of low doses but increased at high radiation doses. Analysis of the FDMR decay kinetics showed that the FDMR effect is a resonant modulation of the singlet yield of geminate ion recombination and suggested that a dose-dependent relaxation process contributes to the decay at high radiation doses. A short-lived component with a broad EPR line width was detected at PPO concentrations below 10/sup -3/ M. This finding suggested that the FDMR method could be used to distinguishmore » between excited states produced by solute anion-solute cation and solute anion-solvent cation recombination reactions. The resolution of hyperfine components in the FDMR spectrum of 10/sup -3/ M biphenyl solutions was strongly dependent on microwave magnetic field and pulse length. The best resolution was obtained with microwave magnetic fields below 0.4 G and pulse widths in excess of 300 ns. The hyperfine structure of the EPR spectra of radical ions involved in excited-state production could be thus obtained by sacrificing some of the time resolution and sensitivity of the FDMR method.« less

Time resolved EPR spectra of aromatic radical ion pairs are measured by optical detection of microwave modulation (ODMR) of the fluorescence of excited aromatics from recombination of radical ion paris produced by pulse radiolysis ODMR data in solutions of pyrene in decalin indicate that geminate recombination processes are the major source of the excited states.

Excited state production and radical ion recombination kinetics in pulse irradiated solutions of aromatic solutes in cyclohexane are studied by a new method of optical detection of time-resolved electron paramagnetic resonance (EPR) spectra.

Excited-state production and radical ion recombination kinetics in pulse-irradiated solutions of aromatic solutes in cyclohexane were studied by a new method of optical detection of time-resolved electron paramagnetic resonance (EPR) spectra. The EPR spectra of radical ion pairs which recombine to yield excited solute singlets were detected by the resonant decrease in fluorescence intensity occurring after application of a single (30 to 500 ns) microwave pulse. Fluorescence detection of magnetic resonance (FDMR) was used to obtain EPR spectra of radical ion pairs with lifetimes between 0.02 and 1.4 ..mu..s at solute concentrations of 10/sup -5/ to 10/sup -1/M. The decay rate of the FDMR intensity observed for 10/sup -3/ M solutions of 2,5-diphenyloxazole (PPO) was independent of radiation dose over a wide range of low doses but increased at high radiation doses. Analysis of the FDMR decay kinetics showed that the FDMR effect is a resonant modulation of the singlet yield of geminate ion recombination and suggested that a dose-dependent relaxation process contributes to the decay at high radiation doses. A short-lived component with a broad EPR line width was detected at PPO concentrations below 10/sup -3/ M. This finding suggested that the FDMR method could be used to distinguishmore » between excited states produced by solute anion-solute cation and solute anion-solvent cation recombination reactions. The resolution of hyperfine components in the FDMR spectrum of 10/sup -3/ M biphenyl solutions was strongly dependent on microwave magnetic field and pulse length. The best resolution was obtained with microwave magnetic fields below 0.4 G and pulse widths in excess of 300 ns. The hyperfine structure of the EPR spectra of radical ions involved in excited-state production could be thus obtained by sacrificing some of the time resolution and sensitivity of the FDMR method.« less