Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 59
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Sci Total Environ ; 770: 145364, 2021 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-33736373

RESUMO

The nanosized iron oxides-based adsorbent has been widely used to alleviate water eutrophication. However, it is challenging to industrialize the application of nanosized iron oxides-based adsorbent due to their poor stability, difficult separation and recovery. Herein, hematite and tetra-n-butylammonium bromide incorporated polyacrylonitrile (PAN/Fe2O3/TBAB) composite nanofibers with a controlled diameter (i.e., 66 to 305 nm) and composition were systematically synthesized as an adsorbent for phosphate removal from water using surfactant-mediated electrospinning. During the electrospinning process, polar TBAB surfactant enhanced the migration of Fe2O3 nanoparticles toward the surface of nanofibers resulting in Fe2O3 nanoparticles/TBAB surface enriched nanofibers. The synthesized nanofiber membranes were used for phosphate removal, and their adsorption kinetics, adsorption mechanism, and reusability were investigated. Data showed that adsorption kinetic followed the pseudo-second-order model whereas the adsorption mechanism follows the Langmuir model. The phosphate removal was mainly derived from the chemisorption of surface-enriched α-Fe2O3 nanoparticles at acidic and circumneutral pH values, with a small contribution from anion exchange at TBAB sites. The maximum phosphate removal capacity was approx. 8.76 mg/g (i.e., 23.1 mg/g, P/active materials) at pH 3. Additionally, the synthesized nanofiber membrane also shows excellent reusability.

2.
Sci Total Environ ; 761: 144121, 2021 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-33360127

RESUMO

Groundwater supplies drinking water for over one-third of all Americans. However, with aquifers stressed by overdraft, contamination from land use, and the hydrologic impacts of climate change, identifying reliable sources for new wells is increasingly challenging. Well forecasting is a process in which potential groundwater resources are evaluated for a location of interest. While this process forecasts the depth of each aquifer for a given location, it takes historical groundwater well data from nearby locations into account. Conventionally, well forecasting is done by geological survey professionals by manually analyzing the well data and, that makes the process both time and resource-intensive. This study presents a novel web application that performs well forecasting for any location within the state of Iowa in a matter of seconds utilizing client-side computing instead of expensive professional labor. The web application generates well forecasts by triangulating millions of combinations of historical aquifer depth data of nearby wells stored in a state-level database. The proposed web system also provides water quality information for arsenic, nitrate, and bacteria (total c and fecal coliform) on the same interface with forecasts. The system is open to the public and is aimed to provide a go-to tool for homeowners, well drillers and, authorities to help inform decision-making regarding groundwater well development and water quality monitoring efforts.


Assuntos
Ciência de Dados , Água Subterrânea , Poluentes Químicos da Água , Monitoramento Ambiental , Humanos , Internet , Iowa , Poluentes Químicos da Água/análise , Poços de Água
3.
Water Sci Technol ; 82(12): 2725-2736, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33341765

RESUMO

Across the Midwestern United States, Public Water Systems (PWSs) struggle with high levels of nitrate in source waters from intense agricultural activity. Leveraging a sensor network deployed across Iowa surface waters, we evaluated the potential of the Hach Nitratax SC Plus, which uses UV-light absorption to quantify dissolved nitrate-nitrite (NOx-N) down to 0.1 mg-N L-1, for real-time monitoring of NOx-N in drinking water. For six different PWSs over multiple years, we compare NOx-N levels in source waters (surface and groundwater under surface influence) to those measured via traditional methods (e.g., ion chromatography (IC)) for US EPA compliance monitoring. At one large PWS, we also evaluated sensor performance when applied to near-finished drinking water (filter effluent). We find good agreement between traditional analytical methods and in situ sensors. For example, for 771 filter effluent samples from 2006-2011, IC analysis averaged NOx-N of 5.8 mg L-1 while corresponding sensor measurements averaged 5.7 mg L-1 with a mean absolute error of 0.23 (5.6%). We identify several benefits of using real-time sensors in PWSs, including improved frequency to capture elevated NOx-N levels and as decision-support tools for NOx-N management.


Assuntos
Água Potável , Água Subterrânea , Poluentes Químicos da Água , Monitoramento Ambiental , Nitratos/análise , Estados Unidos , Poluentes Químicos da Água/análise , Abastecimento de Água
4.
Environ Sci Technol ; 54(22): 14694-14705, 2020 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-33119293

RESUMO

Widespread application of neonicotinoids has led to their proliferation in waters. Despite low neonicotinoid hydrophobicity, our prior studies implicated granular activated carbon (GAC) in neonicotinoid removal. Based on known receptor binding characteristics, we hypothesized that the insecticidal pharmacophore influences neonicotinoid sorption. Our objectives were to illuminate drivers of neonicotinoid sorption for parent neonicotinoids (imidacloprid, clothianidin, thiamethoxam, and thiacloprid) and pharmacophore-altered metabolites (desnitro-imidacloprid and imidacloprid urea) to GAC, powdered activated carbon, and carbon nanotubes (CNTs). Neonicotinoid sorption to GAC was extensive and largely irreversible, with significantly greater sorption of imidacloprid than desnitro-imidacloprid. Imidacloprid and imidacloprid urea (electronegative pharmacophores) sorbed most extensively to nonfunctionalized CNTs, whereas desnitro-imidacloprid (positive pharmacophore) sorbed most to COOH-CNTs, indicating the importance of charge interactions and/or hydrogen bonding between the pharmacophore and carbon surface. Water chemistry parameters (temperature, alkalinity, ionic strength, and humic acid) inhibited overall neonicotinoid sorption, suggesting that pharmacophore-driven sorption in real waters may be diminished. Analysis of a full-scale drinking water treatment plant GAC filter influent, effluent, and spent GAC attributes neonicotinoid/metabolite removal to GAC under real-world conditions for the first time. Our results demonstrate that the neonicotinoid pharmacophore not only confers insecticide selectivity but also impacts sorption behavior, leading to less effective removal of metabolites by GAC filters in water treatment.

5.
Environ Sci Technol ; 54(19): 12181-12190, 2020 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-32910850

RESUMO

Photolysis of trenbolone acetate (TBA) metabolites in the presence of various nitrogen-, sulfur-, or oxygen-containing nucleophiles (e.g., azide, ammonia, or thiosulfate, respectively) results in rapid (half-lives ∼20-60 min), photochemically induced nucleophile incorporation across the parent steroid's trienone moiety. The formation of such nucleophile adducts limits formation of photohydrates, suggesting competition between the nucleophile and water for photochemical addition into the activated steroid structure. Analogous to previously reported photohydration outcomes, LC/MS analyses suggest that such photonucleophilic addition reactions are reversible, with more rapid elimination rates than thermal dehydration of photohydrates, and regenerate parent steroid structures. Beyond photonucleophilic addition pathways, we also found that hydroxylamine and presumed nucleophilic moieties in model dissolved organic matter (DOM; Fluka humic acid) can react via thermal substitution with TBA metabolite photohydrates, although this reaction with model DOM was only observed for photohydrates of trendione. Most nucleophile addition products [i.e., formed via (photo)reaction with thiosulfate, hydroxylamine, and ammonia] are notably more polar relative to the parent metabolite and photohydration products. Thus, if present, both nucleophilic adducts and bound residues in organic matter will facilitate transport and help mask detection of TBA metabolites in surface waters and treatment systems.

6.
Chem Biol Interact ; 330: 109247, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32866466

RESUMO

This study investigated the enantioselective metabolism of benoxacor, an ingredient of herbicide formulations, in microsomes or cytosol prepared from female or male rat livers. Benoxacor was incubated for ≤30 min with microsomes or cytosol, and its enantioselective depletion was measured using gas chromatographic methods. Benoxacor was depleted in incubations with active microsomes in the presence and absence of NADPH, suggesting its metabolism by hepatic cytochrome P450 enzymes (CYPs) and microsomal carboxylesterases (CESs). Benoxacor was depleted in cytosolic incubations in the presence of glutathione, consistent with its metabolism by glutathione S-transferases (GSTs). The depletion of benoxacor was faster in incubations with cytosol from male than female rats, whereas no statistically significant sex differences were observed in microsomal incubations. The consumption of benoxacor was inhibited by the CYP inhibitor 1-aminobenzotriazole, the CES inhibitor benzil, and the GST inhibitor ethacrynic acid. Estimates of the intrinsic clearance of benoxacor suggest that CYPs are the primary metabolic enzyme responsible for benoxacor metabolism in rats. Microsomal incubations showed an enrichment of the first eluting benoxacor enantiomer (E1-benoxacor). A greater enrichment occurred in incubations with microsomes from female (EF = 0.67 ± 0.01) than male rats (EF = 0.60 ± 0.01). Cytosolic incubations from female rats resulted in enrichment of E1-benoxacor (EF = 0.54 ± 0.01), while cytosolic incubations from male rats displayed enrichment of the second eluting enantiomer (E2-benoxacor; EF = 0.43 ± 0.01). Sex-dependent differences in the metabolism of benoxacor in rats could significantly impact ecological risks and mammalian toxicity. Moreover, changes in the enantiomeric enrichment of benoxacor may be a powerful tool for environmental fate and transport studies.


Assuntos
Fígado/metabolismo , Oxazinas/metabolismo , Frações Subcelulares/metabolismo , Animais , Sistema Enzimático do Citocromo P-450/metabolismo , Citosol/enzimologia , Citosol/metabolismo , Feminino , Herbicidas/química , Masculino , Microssomos Hepáticos/enzimologia , Microssomos Hepáticos/metabolismo , Ratos , Fatores Sexuais , Estereoisomerismo
7.
Environ Sci Technol ; 54(17): 10668-10677, 2020 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-32786552

RESUMO

Per and polyfluoroalkyl substances (PFAS), legacy chemicals used in firefighting and the manufacturing of many industrial and consumer goods, are widely found in groundwater resources, along with other regulated compounds, such as chlorinated solvents. Due to their strong C-F bonds, these molecules are extremely recalcitrant, requiring advanced treatment methods for effective remediation, with hydrated electrons shown to be able to defluorinated these compounds. A combined photo/electrochemical method has been demonstrated to dramatically increase defluorination rates, where PFAS molecules sorbed onto appropriately functionalized cathodes charged to low cell potentials (-0.58 V vs Ag/AgCl) undergo a transient electron transfer event from the electrode, which "primes" the molecule by reducing the C-F bond strength and enables the bond's dissociation upon the absorption of a hydrated electron. In this work, we explore the impact of headgroup and chain length on the performance of this two-electron process and extend this technique to chlorinated solvents. We use isotopically labeled PFAS molecules to take advantage of the kinetic isotope effect and demonstrate that indeed PFAS defluorination is likely driven by a two-electron process. We also present density functional theory calculations to illustrate that the externally applied potential resulted in an increased rate of electron transfer, which ultimately increased the measured defluorination rate.

8.
AWWA Water Sci ; : e1186, 2020 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-32838226

RESUMO

The unprecedented number of building closures related to the coronavirus disease (COVID-19) pandemic is concerning because water stagnation will occur in many buildings that do not have water management plans in place. Stagnant water can have chemical and microbiological contaminants that pose potential health risks for occupants. Health officials, building owners, utilities, and other entities are rapidly developing guidance to address this issue, but the scope, applicability, and details included in the guidance vary widely. To provide a primer of large building water system preventative and remedial strategies, peer-reviewed, government, industry, and nonprofit literature relevant to water stagnation and decontamination practices for plumbing was synthesized. Preventative practices to help avoid the need for recommissioning (e.g., routine flushing) and specific actions, challenges, and limitations associated with recommissioning were identified and characterized. Considerations for worker and occupant safety were also indicated. The intended audience of this work includes organizations developing guidance.

9.
Inorg Chem ; 59(12): 8134-8145, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32437172

RESUMO

Naturally occurring uranium is a widespread contaminant present in the water resources around the abandoned uranium mines in the southwest United States. A novel method for rapid uranium detection has been recently developed that relies on the sequestering of uranium by amidoximated polyacrylonitrile (AO-PAN) polymer mats and uses the Raman-active (ν1) symmetric stretch as the signal. The Raman signals obtained from uranium bearing AO-PAN were challenging to interpret due to an unknown uranyl speciation on the surface of the mats. Herein, we provide the synthesis and structural characterization of six model coordination compounds that contain acetamidoxime/benzamidoxime (AAO/BAO) coordinated to the uranyl cation: [UO2(η1-AAO)(NO3)2(H2O)] (1), [UO2(η1-AAO)2(NO3)2] (2), [UO2(η2-BAO)2(CH3OH)2] (3), [(UO2)3(η2-BAO)3(µ2-NO3)3] (4), [(UO2)4(µ3-O)2(µ2-BAO)4(η1-BAO)4(H2O)2](NO3)4 (5), and [(UO2)4(µ3-O)2(µ2-BAO)4(η1-BAO)6Na(NO3)2](NO3)3 (6). Solid-state Raman spectra of 1-6 showed dramatic differences in the uranyl ν1 symmetric stretch depending on the coordination of the amidoxime functional group. The assignments made from the solid-state Raman spectra were used to deconvolute the solution-state Raman spectra of uranyl-acetamidoxime/benzamidoxime methanol solutions at different metal to ligand molar ratios. At low molar ratios (1 U:1 AAO/BAO and 1 U:2 AAO/BAO) the dominant species is the uranyl coordinated via the η1-oxygen atom of the oxime group, while at high molar ratios (1 U:3 AAO/BAO and 1 U:4 AAO/BAO) the dominant species are a tetrameric uranyl-µ3-O-η1-amidoxime complex similar to compounds 5 and 6 and a uranyl-η2-amidoxime complex similar to compounds 3 and 4. Solid-state Raman spectra showed good agreement with Raman signals obtained from the uranyl-AO-PAN mats, demonstrating that binding motifs between uranyl and amidoxime in compounds 5 and 6 are the most representative of the uranyl species on the surface of the AO-PAN mats.

10.
Environ Sci Technol ; 54(11): 6703-6712, 2020 06 02.
Artigo em Inglês | MEDLINE | ID: mdl-32343558

RESUMO

To improve the performance of polymeric electrospun nanofiber mats (ENMs) for equilibrium passive sampling applications in water, we integrated two types of multiwalled carbon nanotubes (CNTs; with and without surface carboxyl groups) into polyacrylonitrile (PAN) and polystyrene (PS) ENMs. For 11 polar and moderately hydrophobic compounds (-0.07 ≤ logKOW ≤ 3.13), 90% of equilibrium uptake was achieved in under 0.8 days (t90% values) in nonmixed ENM-CNT systems. Sorption capacity of ENM-CNTs was between 2- and 50-fold greater than pure polymer ENMs, with equilibrium partition coefficients (KENM-W values) ranging from 1.4 to 3.1 log units (L/kg) depending on polymer type (hydrophilic PAN or hydrophobic PS), CNT loading (i.e., values increased with weight percent (wt %) of CNTs), and CNT type (i.e., greater uptake with carboxylated CNTs composites). During field deployment at Muddy Creek in North Liberty, Iowa, optimal ENM-CNTs (PAN with 20 wt % carboxylated CNTs) yielded atrazine concentrations in surface water with a 40% difference relative to analysis of a same-day grab sample. We also observed a mean percent difference of 30 (±20)% when comparing ENM-CNT sampler results to grab sample data collected within 1 week of deployment. With their rapid, high capacity uptake and small material footprint, ENM-CNT equilibrium passive samplers represent a promising alternative to complement traditional integrative passive samplers while offering convenience over large volume grab sampling.


Assuntos
Nanofibras , Nanotubos de Carbono , Poluentes Químicos da Água , Monitoramento Ambiental , Iowa , Polímeros , Poluentes Químicos da Água/análise
11.
Environ Sci Process Impacts ; 22(6): 1315-1346, 2020 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-32267911

RESUMO

Neonicotinoid insecticides are widely used in both urban and agricultural settings around the world. Historically, neonicotinoid insecticides have been viewed as ideal replacements for more toxic compounds, like organophosphates, due in part to their perceived limited potential to affect the environment and human health. This critical review investigates the environmental fate and toxicity of neonicotinoids and their metabolites and the potential risks associated with exposure. Neonicotinoids are found to be ubiquitous in the environment, drinking water, and food, with low-level exposure commonly documented below acceptable daily intake standards. Available toxicological data from animal studies indicate possible genotoxicity, cytotoxicity, impaired immune function, and reduced growth and reproductive success at low concentrations, while limited data from ecological or cross-sectional epidemiological studies have identified acute and chronic health effects ranging from acute respiratory, cardiovascular, and neurological symptoms to oxidative genetic damage and birth defects. Due to the heavy use of neonicotinoids and potential for cumulative chronic exposure, these insecticides represent novel risks and necessitate further study to fully understand their risks to humans.


Assuntos
Inseticidas , Neonicotinoides , Agricultura , Animais , Anormalidades Congênitas , Estudos Transversais , Exposição Ambiental , Saúde Ambiental , Humanos , Inseticidas/toxicidade , Neonicotinoides/toxicidade
12.
Environ Sci Process Impacts ; 21(10): 1650-1663, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31490490

RESUMO

This study evaluated the sorption and transport potential of seven phototransformation products of 17α-trenbolone, 17ß-trenbolone, trendione, and altrenogest, along with the parent trienone steroids in batch and column soil-water systems. In batch systems, the target solutes exhibited linear isotherms, with values for sorption coefficients (log Koc) of parent steroids (2.46-2.76) higher than those for photoproducts (1.92-2.57). In column systems, the estimated retardation factors (Rsol) for parents (2.7-5.1) were ∼2-5 times higher than those for photoproducts (0.84-1.7). The log Koc (R2 = 0.75) and Rsol (R2 = 0.89-0.98) were well correlated with measured log Kow values, indicating that hydrophobic partitioning governed the soil-solute interaction of these biologically potent compounds in soil-water systems. These data indicated that photoproducts exhibited reduced sorption affinity and increased transport potential relative to more hydrophobic parent structures. In agroecosystems, traditional runoff management practices would be expected to exhibit reduced treatment effectiveness for photoproducts relative to the parent compounds of commonly used trienone steroids.


Assuntos
Poluentes Ambientais/análise , Estrenos/análise , Acetato de Trembolona/análogos & derivados , Acetato de Trembolona/análise , Adsorção , Agricultura , Poluentes Ambientais/química , Estrenos/química , Modelos Químicos , Solo/química , Acetato de Trembolona/química , Água/química
13.
J Org Chem ; 84(17): 11366-11371, 2019 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-31381858

RESUMO

While studying the environmental fate of potent endocrine-active steroid hormones, we observed the formation of an intramolecular [2 + 2] photocycloaddition product (2) with a novel hexacyclic ring system following the photolysis of altrenogest (1). The structure and absolute configuration were established by X-ray diffraction analysis. Theoretical computations identified a barrierless two-step cyclization mechanism for the formation of 2 upon photoexcitation. 2 exhibited progesterone, estrogen, androgen, and pregnane X receptor activity, albeit generally with reduced potency relative to 1.


Assuntos
Processos Fotoquímicos , Acetato de Trembolona/análogos & derivados , Reação de Cicloadição , Teoria da Densidade Funcional , Humanos , Receptores Citoplasmáticos e Nucleares/metabolismo , Acetato de Trembolona/síntese química , Acetato de Trembolona/química , Acetato de Trembolona/metabolismo
14.
ACS Appl Mater Interfaces ; 11(37): 33913-33922, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31436952

RESUMO

The widespread environmental occurrence of per- and polyfluoroalkyl substances (PFAS) has attracted significant regulatory, research, and media attention because of their toxicity, recalcitrance, and ability to bioaccumulate. Perfluorooctane sulfonate (PFOS) is a particularly troublesome member of the PFAS family due to its immunity to biological remediation and radical-based oxidation. In the present study, we present a heterogeneous reductive degradation process that couples direct electron transfer (ET) from surface-modified carbon nanotube electrodes (under low potential conditions) to sorbed PFOS molecules using UV-generated hydrated electrons without any further chemical addition. We demonstrate that the ET process dramatically increases the PFOS defluorination rate while yielding shorter chain (C3-C7) perfluorinated acids and present both experimental and ab initio evidence of the synergistic relationship between electron addition to sorbed molecules and their ability to react with reductive hydrated electrons. Because of the low energy consumption associated with the ET process, the use of standard medium-pressure UV lamps and no further chemical addition, this reductive degradation process is a promising method for the destruction of persistent organic pollutants, including PFAS and other recalcitrant halogenated organic compounds.

15.
J Chromatogr A ; 1603: 150-159, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31227361

RESUMO

Here, we developed a novel and sensitive method for the detection and quantification of metastable trenbolone and altrenogest photoproducts in agricultural receiving waters based on solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Primary method analytes were seven cycloaddition or photohydration transformation products of 17α-trenbolone (17α-TBOH), 17ß-trenbolone (17ß-TBOH), trendione (TBO), and altrenogest (ALT), which are key contributors to the fate and environmental risks of these steroidal pharmaceuticals. Because commercial analytical standards are not available, reference standards for photoproducts were generated from trenbolone or ALT with a solar simulator (˜6 h, >10 half-lives). Efficient detection of metastable photoproducts required cold and pH neutral conditions, rapid sample processing, minimal sample storage, and consideration of cationic artifacts. Method detection limits (MDLs) were 0.034-0.40 ng L-1 for parent compounds and 0.16-2.1 ng L-1 for photoproducts, sufficient for their detection in agroecosystems. Matrix suppression was observed and corrected by internal standards, and relative recovery rates were near 100% for all analytes except for 12-OH-17α-TBOH (˜75% recovery). Intra-day variation was <20% and inter-day variation <25% for all the analytes. The developed method is capable of the analysis of trenbolone, altrenogest, and their key bioactive photoproducts in agricultural receiving waters.


Assuntos
Cromatografia Líquida/métodos , Espectrometria de Massas em Tandem/métodos , Acetato de Trembolona/análogos & derivados , Acetato de Trembolona/análise , Cátions , Luz , Limite de Detecção , Reprodutibilidade dos Testes
16.
Environ Sci Technol ; 53(12): 6738-6746, 2019 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-31117539

RESUMO

Dichloroacetamide safeners are commonly added to commercial chloroacetamide herbicide formulations and widely used worldwide, but their environmental fate has garnered little scrutiny as a result of their classification as "inert" ingredients. Here, we investigated the photolysis of dichloroacetamide safeners to better understand their persistence and the nature of their transformation products in surface waters. High-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy were used to characterize photoproducts. Of the four commonly used dichloroacetamide safeners, only benoxacor undergoes direct photolysis under simulated natural sunlight ( t1/2 ∼ 10 min). Via a photoinitiated ring closure, benoxacor initially yields a monochlorinated intermediate that degrades over longer irradiation time scales to produce two fully dechlorinated diastereomers and a tautomer, which further photodegrade over several days to a structurally related aldehyde confirmed via NMR. Dichlormid, AD-67, and furilazole were more slowly degraded by indirect photolysis in the presence of the photosensitizers nitrate, nitrite, and humic acid. Reactive entities involved in these reactions are likely hydroxyl radical and singlet oxygen based on the use of selective quenchers. These safeners also directly photolyzed under higher energy ultraviolet (UV) light, suggesting their potential transformation in engineered systems using UV for disinfection. The finding that dichloroacetamide safeners can undergo photolysis in environmental systems over relevant time scales demonstrates the importance of evaluating the fate of this class of "inert" agrochemicals.


Assuntos
Herbicidas , Poluentes Químicos da Água , Acetamidas , Substâncias Húmicas , Cinética , Fotólise , Luz Solar
17.
Org Lett ; 21(10): 3568-3571, 2019 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-31021644

RESUMO

In an ongoing effort to study the environmental fate of endocrine-active steroid hormones, we report the formation of phenolic rearrangement products (3 and 4) with a novel 6,5,8,5-ring system following aqueous photolysis of dienogest (1) and methyldienolone (2). The structures were established by analysis of 2D NMR and HRMS data, and that of 3 was confirmed by X-ray diffraction analysis. These photoproducts exhibit progestogenic and androgenic activity, albeit with less potency than their parent compounds.


Assuntos
Nandrolona/análogos & derivados , Esteroides/química , Estrutura Molecular , Nandrolona/química , Preparações Farmacêuticas , Fotólise
18.
Water Res ; 148: 492-503, 2019 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-30408735

RESUMO

Point-of-use water treatment technologies can help mitigate risks from drinking water contamination, particularly for metals (and metalloids) that originate in distribution systems (e.g., chromium, lead, copper) or are naturally occurring in private groundwater wells (e.g., arsenic). Here, composite nanofibers of polyacrylonitrile (PAN) with embedded hematite (α-Fe2O3) nanoparticles were synthesized via a single-pot electrospinning synthesis. A core-shell nanofiber composite was also prepared through the subsequent hydrothermal growth of α-Fe2O3 nanostructures on embedded hematite composites. Properties of embedded hematite composites were controlled using electrospinning synthesis variables (e.g., size and loading of embedded α-Fe2O3 nanoparticles), whereas core-shell composites were also tailored via hydrothermal treatment conditions (e.g., soluble iron concentration and duration). Although uptake of Cu(II), Pb(II), Cr(VI), and As(V) was largely independent of the core-shell variables explored, metal uptake on embedded nanofibers increased with α-Fe2O3 loading. Both materials exhibited maximum surface-area-normalized sorption capacities that were comparable to α-Fe2O3 nanoparticle dispersions and exceeded that of a commercial iron oxide based sorbent. Further, both types of composite exhibited strong performance across a range of environmentally relevant pH values (6.0-8.0). Notably, core-shell structures, with a majority of surface accessible α-Fe2O3, performed far better than embedded composites in kinetically limited flow through systems than was anticipated from their relative performance in equilibrium batch systems. Core-shell nanofiber filters also retained much of the durability and flexibility exhibited by embedded nanofibers. Additional tests with authentic groundwater samples demonstrated the ability of the core-shell nanofiber filters to remove simultaneously both As and suspended solids, illustrating their promise as a nano-enabled technology for point-of-use water treatment.


Assuntos
Nanofibras , Compostos Férricos , Metais , Polímeros
19.
Anal Chem ; 90(11): 6766-6772, 2018 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-29741873

RESUMO

Reproducible detection of uranyl, an important biological and environmental contaminant, from complex matrixes by surface-enhanced Raman scattering (SERS) is successfully achieved using amidoximated-polyacrylonitrile (AO-PAN) mats and carboxylated gold (Au) nanostars. SERS detection of small molecules from a sample mixture is traditionally limited by nonspecific adsorption of nontarget species to the metal nanostructures and subsequent variations in both the vibrational frequencies and intensities. Herein, this challenge is overcome using AO-PAN mats to extract uranyl from matrixes ranging in complexity including HEPES buffer, Ca(NO3)2 and NaHCO3 solutions, and synthetic urine. Subsequently, Au nanostars functionalized with carboxyl-terminated alkanethiols are used to enhance the uranyl signal. The detected SERS signals scale with uranyl uptake as confirmed using liquid scintillation counting. SERS vibrational frequencies of uranyl on both hydrated and lyophilized polymer mats are largely independent of sample matrix, indicating less complexity in the uranyl species bound to the surface of the mats vs in solution. These results suggest that matrix effects, which commonly limit the use of SERS for complex sample analysis, are minimized for uranyl detection. The presented synergistic approach for isolating uranyl from complex sample matrixes and enhancing the signal using SERS is promising for real-world sample detection and eliminates the need of radioactive tracers and extensive sample pretreatment steps.


Assuntos
Resinas Acrílicas/química , Ouro/química , Nanopartículas Metálicas/química , Urânio/análise , Análise Espectral Raman , Propriedades de Superfície
20.
Environ Sci Process Impacts ; 19(11): 1445-1456, 2017 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29086783

RESUMO

We fabricated a suite of polymeric electrospun nanofiber mats (ENMs) and investigated their performance as next-generation passive sampler media for environmental monitoring of organic compounds. Electrospinning of common polymers [e.g., polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polystyrene (PS), among others] yielded ENMs with reproducible control of nanofiber diameters (from 50 to 340 nm). The ENM performance was investigated initially with model hydrophilic (aniline and nitrobenzene) and hydrophobic (selected PCB congeners and dioxin) compounds, generally revealing fast chemical uptake into all of these ENMs, which was well described by a one compartment, first-order kinetic model. Typical times to reach 90% equilibrium (t90%) were ≤7 days under mixing conditions for all the ENMs and <0.5 days for the best performing materials under static (i.e., no mixing) conditions. Collectively, these short equilibrium timescales suggest that ENMs may be used in the field as an equilibrium-passive sampler, at least for our model compounds. Equilibrium partitioning coefficients (KENM-W, L kg-1) averaged 2 and 4.7 log units for the hydrophilic and hydrophobic analytes, respectively. PAN, PMMA and PS were prioritized for additional studies because they exhibited not only the greatest capacity for simultaneous uptake of the entire model suite (log KENM-W ∼1.5-6.2), but also fast uptake. For these optimized ENMs, the rates of uptake into PAN and PMMA were limited by aqueous phase diffusion to the nanofiber surface, and the rate-determining step for PS was analyte specific. Sorption isotherms also revealed that the environmental application of these optimized ENMs would occur within the linear uptake regime. We examined the ENM performance for the measurement of pore water concentrations from spiked soil and freshwater sediments. Soil and sediment studies not only yielded reproducible pore water concentrations and comparable values to other passive sampler materials, but also provided practical insights into ENM stability and fouling in such systems. Furthermore, fast uptake for a suite of structurally diverse hydrophilic and moderately hydrophobic compounds was obtained for PAN and PS, with t90% ranging from 0.01 to 4 days with mixing and KENM-W values ranging from 1.3 to 3.2 log units. Our findings show promise for the development and use of ENMs as equilibrium-passive samplers for a range of organic pollutants across soil/sediment and water systems.


Assuntos
Monitoramento Ambiental/métodos , Modelos Teóricos , Nanofibras/química , Compostos Orgânicos/análise , Polímeros/química , Poluentes Químicos da Água/análise , Adsorção , Monitoramento Ambiental/instrumentação , Água Doce/química , Sedimentos Geológicos/química , Interações Hidrofóbicas e Hidrofílicas , Polímeros/síntese química , Propriedades de Superfície
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...