Degradation of Adsorbed Bisphenol A by Soluble Mn(III).

Bisphenol A (BPA), a high production volume chemical and potential endocrine disruptor, is found to be associated with sediments and soils due to its hydrophobicity (log KOW of 3.42). We used superfine powdered activated carbon (SPAC) with a particle size of 1.38 ± 0.03 µm as a BPA sorbent and assessed degradation of BPA by oxidized manganese (Mn) species. SPAC strongly sorbed BPA, and desorption required organic solvents. No degradation of adsorbed BPA (278.7 ± 0.6 mg BPA g-1 SPAC) was observed with synthetic, solid α-MnO2 with a particle size of 15.41 ± 1.35 µm; however, 89% mass reduction occurred following the addition of 0.5 mM soluble Mn(III). Small-angle neutron scattering data suggested that both adsorption and degradation of BPA occurred in SPAC pores. The findings demonstrate that Mn(III) mediates oxidative transformation of dissolved and adsorbed BPA, the latter observation challenging the paradigm that contaminant desorption and diffusion out of pore structures are required steps for degradation. Soluble Mn(III) is abundant near oxic-anoxic interfaces, and the observation that adsorbed BPA is susceptible to degradation has implications for predicting, and possibly managing, the fate and longevity of BPA in environmental systems.

Dissolved Organic Matter Singlet Oxygen Quantum Yields: Evaluation Using Time-Resolved Singlet Oxygen Phosphorescence.

Singlet oxygen (1O2) generation quantum yields from chromophoric dissolved organic matter (CDOM) have been reported for many samples over the past 4 decades. Yet even for standardized isolates such as those from the International Humic Substance Society (IHSS), wide-ranging values exist in the literature. In this manuscript, time-resolved 1O2 phosphorescence was used to determine the 1O2 quantum yields (ΦΔ) of a variety of dissolved organic matter (DOM) isolates and natural waters. In general, the 1O2 quantum yield values in this study are in the middle, although below the median of the range of past reported values (e.g., for Suwannee River Natural Organic Matter IHSS isolate: 1.8% vs 0.23-2.89%). Notably, hydrophobic neutral fractions of DOM isolates were found to possess the highest 1O2 quantum yields, an interesting result given that these fractions are not retained in typical humic and fulvic acid isolation procedures that use XAD resins. The excitation wavelength dependence of 1O2 generation from CDOM was also examined, and an approximate linear decrease with longer excitation wavelength was observed. This work advances the understanding of CDOM photoprocesses, especially in relation to wavelength-dependent 1O2 production, which is valuable for assessing real-world environmental behavior.

Sorbic Acid as a Triplet Probe: Reactivity of Oxidizing Triplets in Dissolved Organic Matter by Direct Observation of Aromatic Amine Oxidation.

Sorbic acid (2,4-hexadienoic acid; HDA) isomerization is frequently used to probe triplet-state dissolved organic matter (3CDOM*) reactivity, but there remain open questions about the reaction kinetics of 3CDOM* with HDA due to the difficulties of directly measuring 3CDOM* quenching rate constants. Using our recently developed approach based on observing the radical cation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) formed through oxidation of TMPD by 3CDOM*, we studied 3CDOM* quenching kinetics with HDA monitored via transient absorption spectroscopy. A competition kinetics-based approach utilizing formation yields of TMPD•+ was developed, validated with model sensitizers, and used to determine bimolecular rate constants between 3CDOM* oxidants and HDA for diverse DOM isolates and natural waters samples, yielding values in the range of (2.4-7.7) × 108 M-1 s-1. The unquenchable fraction of TMPD-oxidizing triplets showed that, on average, 41% of 3CDOM* oxidants cannot be quenched by HDA. Conversely, cycloheptatriene quenched nearly all TMPD•+-forming triplets in CDOM, suggesting that most 3CDOM* oxidants possess energies greater than 150 kJ mol-1. Comparing results with our companion study, we found slight, but noticeable differences in the 3CDOM* quenching rate constants by HDA and unquenchable triplet fractions determined by oxidation of TMPD and energy transfer to O2 (1O2 formation) methods.

Sorbic Acid as a Triplet Probe: Triplet Energy and Reactivity with Triplet-State Dissolved Organic Matter via 1O2 Phosphorescence.

Sorbic acid (2,4-hexadienoic acid; HDA) is commonly used as a probe and quencher for triplet-excited chromophoric dissolved organic matter (3CDOM*), an important transient species in natural waters, yet much remains unknown about its reactivity with 3CDOM* and its triplet energy. To better understand the quenching behavior of HDA, we measured HDA quenching rate constants for various humic substance isolates and whole waters with singlet oxygen (1O2) phosphorescence and determined the triplet energy of HDA. Low-temperature phosphorescence measurements determined the triplet energy of HDA to be 217 kJ mol-1, whereas a complementary method based on triplet quenching kinetics found a triplet energy of 184 ± 7 kJ mol-1. Time-resolved 1O2 phosphorescence measurements yielded different HDA quenching rate constants depending on the fitting method. Using an approach that considered the reactivity of the entire triplet pool produced values of (∼1-10) × 108 M-1 s-1, while an approach that considered only the reactivity of the high-energy triplets output higher rate constants ((∼7-30) × 108 M-1 s-1). In addition, the model based on high-energy triplet reactivity found that ∼30-60% of 3CDOM* is not quenched by HDA. Findings from this study provide a more comprehensive view on the use of HDA as a probe for 3CDOM*.

Furan Carboxamides as Model Compounds To Study the Competition between Two Modes of Indirect Photochemistry.

Singlet oxygen (1O2) and triplet chromophoric dissolved organic matter (3CDOM*) are photochemically produced reactive intermediates responsible for the photodegradation of several micropollutants in the sunlit surface waters. However, elucidating the mechanism of reactions involving both 1O2 and 3CDOM* can be complicated by the deeply interconnected nature of these two reactive species. In this work, we synthesized a series of model compounds inspired by the chemical structure of fenfuram, a fungicide used in the 1980s, and used them to investigate structure-reactivity relationships in photodegradation reactions involving 1O2 and 3CDOM*. A combination of steady-state and time-resolved approaches was employed to successfully predict the extent of 1O2-induced degradation. Conversely, the prediction of triplet-induced reactivity was complicated by the presence of repair mechanisms whose extent and relative importance were difficult to predict. The results of our work indicate that bimolecular rate constants measured via time-resolved techniques alone are not sufficient to accurately predict environmental half-lives, as intrinsic differences in the reaction mechanism can amplify the importance of secondary degradation pathways.

Photochemical Production of Sulfate and Methanesulfonic Acid from Dissolved Organic Sulfur.

Photodegradation processes play an important role in releasing elements tied up in biologically refractory forms in the environment, and are increasingly being recognized as important contributors to biogeochemical cycles. While complete photo-oxidation of dissolved organic carbon (to CO2) and dissolved organic phosphorous (to PO43-) has been documented, the analogous photoproduction of sulfate from dissolved organic sulfur (DOS) has not yet been reported. Recent high-resolution mass spectrometry studies showed a selective loss of organic sulfur during photodegradation of dissolved organic matter, which was hypothesized to result in the production of sulfate. Here, we provide evidence of ubiquitous production of sulfate, methanesulfonic acid (MSA), and methanesulfinic acid (MSIA) during photodegradation of DOM samples from a wide range of natural terrestrial environments. We show that photochemical production of sulfate is generally more efficient than the production of MSA and MSIA, as well as volatile S-containing compounds such as CS2 and COS. We also identify possible molecular precursors for sulfate and MSA, and we demonstrate that a wide range of relevant classes of DOS compounds (in terms of S oxidation state and molecular structure) can liberate sulfate upon photosensitized degradation. This work suggests that photochemistry may play a more significant role in the aquatic and atmospheric fate of DOS than currently believed.

Singlet Oxygen Phosphorescence as a Probe for Triplet-State Dissolved Organic Matter Reactivity.

Triplet-state chromophoric dissolved organic matter (3CDOM*) plays an important role in aquatic photochemistry, yet much remains unknown about the reactivity of these intermediates. To better understand the kinetic behavior and reactivity of 3CDOM*, we have developed an indirect observation method based on monitoring time-resolved singlet oxygen (1O2) phosphorescence kinetics. The underpinning principle of our approach relies on the fact that O2 quenches almost all triplets with near diffusion limited rate constants, resulting in the formation of 1O2, which is kinetically linked to the precursors. A kinetic model relating 1O2 phosphorescence kinetics to triplet excited states produced from isolated humic substances and in whole natural-water samples (hereafter referred to as 3CDOM*) was developed and used to determine rate constants governing 3CDOM* natural lifetimes and quenching by oxygen and 2,4,6-trimethylphenol (TMP), a common triplet probe molecule. 3CDOM* was found to exhibit smaller O2 and TMP quenching rate constants, ∼9 × 108 and ∼8 × 108 M-1 s-1, respectively, compared with model sensitizers, such as aromatic ketones. Findings from this report shed light on the fundamental photochemical properties of CDOM in organic matter isolates and whole waters and will help refine photochemical models to more accurately predict pollutant fate in the environment.

The Case Against Charge Transfer Interactions in Dissolved Organic Matter Photophysics.

The optical properties of dissolved organic matter influence chemical and biological processes in all aquatic ecosystems. Dissolved organic matter optical properties have been attributed to a charge-transfer model in which donor-acceptor complexes play a primary role. This model was evaluated by measuring the absorbance and fluorescence response of organic matter isolates to changes in solvent temperature, viscosity, and polarity, which affect the position and intensity of spectra for known donor-acceptor complexes of organic molecules. Absorbance and fluorescence spectral shape were largely unaffected by these changes, indicating that the distribution of absorbing and emitting species was unchanged. Overall, these results call into question the wide applicability of the charge-transfer model for explaining organic matter optical properties and suggest that future research should explore other models for dissolved organic matter photophysics.

De novo generation of adipocytes from circulating progenitor cells in mouse and human adipose tissue.

White adipocytes in adults are typically derived from tissue resident mesenchymal progenitors. The recent identification of de novo production of adipocytes from bone marrow progenitor-derived cells in mice challenges this paradigm and indicates an alternative lineage specification that adipocytes exist. We hypothesized that alternative lineage specification of white adipocytes is also present in human adipose tissue. Bone marrow from transgenic mice in which luciferase expression is governed by the adipocyte-restricted adiponectin gene promoter was adoptively transferred to wild-type recipient mice. Light emission was quantitated in recipients by in vivo imaging and direct enzyme assay. Adipocytes were also obtained from human recipients of hematopoietic stem cell transplantation. DNA was isolated, and microsatellite polymorphisms were exploited to quantify donor/recipient chimerism. Luciferase emission was detected from major fat depots of transplanted mice. No light emission was observed from intestines, liver, or lungs. Up to 35% of adipocytes in humans were generated from donor marrow cells in the absence of cell fusion. Nontransplanted mice and stromal-vascular fraction samples were used as negative and positive controls for the mouse and human experiments, respectively. This study provides evidence for a nontissue resident origin of an adipocyte subpopulation in both mice and humans.

Triplet-State Dissolved Organic Matter Quantum Yields and Lifetimes from Direct Observation of Aromatic Amine Oxidation.

Excited triplet state chromophoric dissolved organic matter (3CDOM*) is a short-lived mixture of excited-state species that plays important roles in aquatic photochemical processes. Unlike the study of the triplet states of well-defined molecules, which are amenable to transient absorbance spectroscopy, the study of 3CDOM* is hampered by it being a complex mixture and its low average intersystem crossing quantum yield (ΦISC). This study is an alternative approach to investigating 3CDOM* using transient absorption laser spectroscopy. The radical cation of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD), formed through oxidation by 3CDOM*, was directly observable by transient absorption spectroscopy and was used to probe basic photophysical properties of 3CDOM*. Quenching and control experiments verified that TMPD•+ was formed from 3CDOM* under anoxic conditions. Model triplet sensitizers with a wide range of excited triplet state reduction potentials and CDOM oxidized TMPD at near diffusion-controlled rates. This gives support to the idea that a large cross-section of 3CDOM* moieties are able to oxidize TMPD and that the complex mixture of 3CDOM* can be simplified to a single signal. Using the TMPD•+ transient, the natural triplet lifetime and ΦISC for different DOM isolates and natural waters were quantified; values ranged from 12 to 26 µs and 4.1-7.8%, respectively.

Photochemical and Nonphotochemical Transformations of Cysteine with Dissolved Organic Matter.

Cysteine (Cys) plays numerous key roles in the biogeochemistry of natural waters. Despite its importance, a full assessment of Cys abiotic transformation kinetics, products and pathways under environmental conditions has not been conducted. This study is a mechanistic evaluation of the photochemical and nonphotochemical (dark) transformations of Cys in solutions containing chromophoric dissolved organic matter (CDOM). The results show that Cys underwent abiotic transformations under both dark and irradiated conditions. Under dark conditions, the transformation rates of Cys were moderate and were highly pH- and temperature-dependent. Under UVA or natural sunlight irradiations, Cys transformation rates were enhanced by up to two orders of magnitude compared to rates under dark conditions. Product analysis indicated cystine and cysteine sulfinic acid were the major photooxidation products. In addition, this study provides an assessment of the contributions of singlet oxygen, hydroxyl radical, hydrogen peroxide, and triplet dissolved organic matter to the CDOM-sensitized photochemical oxidation of Cys. The results suggest that another unknown pathway was dominant in the CDOM-sensitized photodegradation of Cys, which will require further study to identify.

Environmental Photochemistry of Altrenogest: Photoisomerization to a Bioactive Product with Increased Environmental Persistence via Reversible Photohydration.

Despite its wide use as a veterinary pharmaceutical, environmental fate data is lacking for altrenogest, a potent synthetic progestin. Here, it is reported that direct photolysis of altrenogest under environmentally relevant conditions was extremely efficient and rapid (half-life ∼25 s). Photolysis rates (observed rate constant kobs = 2.7 ± 0.2 × 10(-2) s(-1)) were unaffected by changes in pH or temperature but were sensitive to oxygen concentrations (N2-saturated kobs = 9.10 ± 0.32 × 10(-2) s(-1); O2-saturated kobs = 1.38 ± 0.11 × 10(-2) s(-1)). The primary photoproduct was identified as an isomer formed via an internal 2 + 2 cycloaddition reaction; the triplet lifetime (8.4 ± 0.2 µs) and rate constant (8 × 10(4) s(-1)) of this reaction were measured using transient absorption spectroscopy. Subsequent characterization determined that this primary cycloaddition photoproduct undergoes photohydration. The resultant photostable secondary photoproducts are subject to thermal dehydration in dark conditions, leading to reversion to the primary cycloaddition photoproduct on a time scale of hours to days, with the photohydration and dehydration repeatable over several light/dark cycles. This dehydration reaction occurs more rapidly at higher temperatures and is also accelerated at both high and low pH values. In vitro androgen receptor (AR)-dependent gene transcriptional activation cell assays and in silico nuclear hormone receptor screening revealed that certain photoproducts retain significant androgenic activity, which has implications for exposure risks associated with the presence and cycling of altrenogest and its photoproducts in the environment.

Isotope fractionation associated with the direct photolysis of 4-chloroaniline.

Compound-specific isotope analysis is a useful approach to track transformations of many organic soil and water pollutants. Applications of CSIA to characterize photochemical processes, however, have hardly been explored. In this work, we systematically studied C and N isotope fractionation associated with the direct photolysis of 4-Cl-aniline used as a model compound for organic micropollutants that are known to degrade via photochemical processes. Laboratory experiments were carried out at an irradiation wavelength of 254 nm over the pH range 2.0 to 9.0 as well as in the presence of Cs(+) as a quencher of excited singlet 4-Cl-aniline at pH 7.0 and 9.0. We observed considerable variation of C and N isotope enrichment factors, ϵC and ϵN, between -1.2 ± 0.2‰ to -2.7 ± 0.2‰ for C and -0.6 ± 0.2‰ to -9.1 ± 1.6‰ for N, respectively, which could not be explained by the speciation of 4-Cl-aniline alone. In the presence of 1 M Cs(+), we found a marked increase of apparent (13)C-kinetic isotope effects ((13)C-AKIE) and decrease of 4-Cl-aniline fluorescence lifetimes. Our data suggest that variations of C and N isotope fractionation originate from heterolytic dechlorination of excited triplet and singlet states of 4-Cl-aniline. Linear correlations of (13)C-AKIE vs (15)N-AKIE were distinctly different for these two reaction pathways and may be explored further for the identification of photolytic aromatic dechlorination reactions.

Controlling factors in the rates of oxidation of anilines and phenols by triplet methylene blue in aqueous solution.

Anilines and phenols are structurally similar compound classes that both are susceptible to oxidation by excited state triplet sensitizers but undergo oxidation by different mechanisms. To gain an understanding of the factors that control the rate of oxidation of anilines and phenols by triplet excited states, a kinetic study was performed on the oxidation of substituted anilines and phenols by methylene blue. The rate constants of one-electron transfer from anilines to triplet state methylene blue and their dependence on the reaction free energy are well fit to a Sandros-Boltzmann model. The observed rate constants are also well modeled when aniline oxidation potentials derived computationally are used. For phenols, the proton-coupled electron transfer rate constants were found to correlate primarily with O-H bond dissociation free energy and secondarily with phenol pKa. Rate constants for phenols could be modeled using computed bond dissociation free energies. These results provide a basis for predicting aniline and phenol oxidation rates, which could be valuable, for example, in assessing the likely persistence and fate of aniline- and phenol-based aqueous environmental pollutants.

Dual roles of dissolved organic matter as sensitizer and quencher in the photooxidation of tryptophan.

The photooxidation processes of tryptophan (Trp) in the presence of dissolved organic matter (DOM) were identified and quantified by steady-state photolysis experiments, laser spectroscopy and kinetic modeling. In sunlight, Trp photooxidation is dominated by the reaction with excited triplet DOM ((3)DOM), accounting for approximately 50-70% of the total degradation, depending on the DOM concentration and source. Reaction with singlet oxygen and direct photolysis are secondary processes that are both still more important than the reaction with hydroxyl radical. Both direct photolysis and reaction with (3)DOM form Trp radical cation (Trp(•+)) via Trp photoionization and direct oxidation, respectively. The Trp(•+) can be converted back to Trp by suitable electron or hydrogen atom donors. Transient absorption spectroscopy shows that DOM itself and low-molecular-weight analogues of redox-active moieties can reduce the lifetime of photochemically produced Trp(•+) and thus quench Trp degradation. This study demonstrates that DOM plays dual roles in the photodegradation of Trp acting as a sensitizer and quencher. The photochemistry of Trp and the participation of DOM have direct implications for photochemical reactions in extracellular proteins as well as for organic compounds in aquatic systems with similar photoionization processes.

Review of Cold war social science: Knowledge production, liberal democracy, and human nature, and Working knowledge: Making the human sciences from Parsons to Kuhn.

Reviews the books, Cold War Social Science: Knowledge Production, Liberal Democracy, and Human Nature by Mark Solovey and Hamilton Cravens (2012) and Working Knowledge: Making the Human Sciences From Parsons to Kuhn by Joel Isaac (see record 2012-13212-000). Taken together, these two important books make intriguing statements about the way to write the histories of fields like psychology, sociology, anthropology, and economics in the Anglo American world during the 20th century. To date, histories of these fields have drawn on a number of fairly well-established punctuation marks to assist in periodization: the shift from interwar institutionalism in economics to postwar neoclassicism, with its physics-like emphasis on mathematical theory-building; the transition from the regnant prewar behaviorism through a postwar "cognitive revolution" in American psychology; and the move in fields like sociology and anthropology away from positivism and the pursuit of what has sometimes been called "grand theory" in the early postwar era toward a period defined by intellectual and political fragmentation, the reemergence of interpretive approaches and a reaction to the scientistic pretensions of the earlier period. These books, by contrast, provide perspectives orthogonal to such existing narrative frameworks by adopting cross-cutting lenses like the "Cold War" and the working practices of researchers in the social and behavioral sciences. As a result, they do much to indicate the value of casting a historiographical net beyond individual disciplines, or even beyond the "social sciences" or the "human sciences" sensu stricto, in the search for deeper patterns of historical development in these fields. (PsycINFO Database Record (c) 2013 APA, all rights reserved).

mHealth Intervention for Promoting Hypertension Self-management Among African American Patients Receiving Care at a Community Health Center: Formative Evaluation of the FAITH! Hypertension App.

BACKGROUND: African American individuals are at a higher risk of premature death from cardiovascular diseases than White American individuals, with disproportionate attributable risk from uncontrolled hypertension. Given their high use among African American individuals, mobile technologies, including smartphones, show promise in increasing reliable health information access. Culturally tailored mobile health (mHealth) interventions may promote hypertension self-management among this population. OBJECTIVE: This formative study aimed to assess the feasibility of integrating an innovative mHealth intervention into clinical and community settings to improve blood pressure (BP) control among African American patients. METHODS: A mixed methods study of African American patients with uncontrolled hypertension was conducted over 2 consecutive phases. In phase 1, patients and clinicians from 2 federally qualified health centers (FQHCs) in the Minneapolis-St Paul, Minnesota area, provided input through focus groups to refine an existing culturally tailored mHealth app (Fostering African-American Improvement in Total Health! [FAITH!] App) for promoting hypertension self-management among African American patients with uncontrolled hypertension (renamed as FAITH! Hypertension App). Phase 2 was a single-arm pre-post intervention pilot study assessing feasibility and patient satisfaction. Patients receiving care at an FQHC participated in a 10-week intervention using the FAITH! Hypertension App synchronized with a wireless BP monitor and community health worker (CHW) support to address social determinants of health-related social needs. The multimedia app consisted of a 10-module educational series focused on hypertension and cardiovascular risk factors with interactive self-assessments, medication and BP self-monitoring, and social networking. Primary outcomes were feasibility (app engagement and satisfaction) and preliminary efficacy (change in BP) at an immediate postintervention assessment. RESULTS: In phase 1, thirteen African American patients (n=9, 69% aged ≥50 years and n=10, 77% women) and 16 clinicians (n=11, 69% aged ≥50 years; n=14, 88% women; and n=10, 63% African American) participated in focus groups. Their feedback informed app modifications, including the addition of BP and medication tracking, BP self-care task reminders, and culturally sensitive contexts. In phase 2, sixteen African American patients were enrolled (mean age 52.6, SD 12.3 years; 12/16, 75% women). Overall, 38% (6/16) completed ≥50% of the 10 education modules, and 44% (7/16) completed the postintervention assessment. These patients rated the intervention a 9 (out of 10) on its helpfulness in hypertension self-management. Qualitative data revealed that they viewed the app as user-friendly, engaging, and informative, and CHWs were perceived as providing accountability and support. The mean systolic and diastolic BPs of the 7 patients decreased by 6.5 mm Hg (P=.15) and 2.8 mm Hg (P=.78), respectively, at the immediate postintervention assessment. CONCLUSIONS: A culturally tailored mHealth app reinforced by CHW support may improve hypertension self-management among underresourced African American individuals receiving care at FQHCs. A future randomized efficacy trial of this intervention is warranted. TRIAL REGISTRATION: ClinicalTrials.gov NCT04554147; https://clinicaltrials.gov/ct2/show/NCT04554147.

Photochemical formation of brominated dioxins and other products of concern from hydroxylated polybrominated diphenyl ethers (OH-PBDEs).

The photochemical conversion of selected hydroxylated polybrominated diphenyl ethers (OH-PBDEs) to dioxins and other products was investigated. OH-PBDEs, which are both transformation products of polybrominated diphenyl ethers and naturally occurring compounds, undergo direct photolysis to yield a number of products that may have a higher toxicity than their parent. The compounds investigated were 6-OH-PBDE 99, 6'-OH-PBDE 100, and 6'-OH-PBDE 118. Of special interest was 6'-OH-PBDE 118, a potential transformation product of PBDE 153 that is capable of photochemically generating 2,3,7,8-tetrabromodibenzo-p-dioxin, the most toxic brominated dioxin congener. Photolysis experiments were conducted at two different pH values to assess the photochemical behavior of both the phenol and phenolate form of the compounds. The percent conversion to dioxin and other photoproducts was determined and the natural product, 6-OH-PBDE 99, was found to have the highest conversion to dioxin (7%). The reaction quantum yields ranged from 0.027 to 0.16 across all photolysis conditions. In addition, it is shown that all three compounds are capable of photochemically generating other compounds of concern, including brominated phenols and a dibenzofuran.