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Action Potential Science Experience (APSE) is a five-day summer camp offering science opportunities for K−8 students. The focus of the APSE curriculum is to teach science concepts and methods while...

The effect of aging on pyrene transformation and pyrene association with fractions of the sedimentary organic matrix (SdOM) was evaluated using [4,9-(13)C2]pyrene. Sediments were collected from a site of previous petroleum hydrocarbon contamination (New Orleans, LA, USA). Aged sediments were autoclaved for 1 h, amended with pyrene, and then stored in the dark in a 0.05% NaN3 solution for 120 d. Both aged and nonaged sediments were incubated in aerated microcosms for 120 d. Microcosms were acidified to collect evolved carbon dioxide (CO2); sediments were fractionated and lipid extracted to quantify pyrene in SdOM fractions. Cross-polarization magic angle spinning 13C-nuclear magnetic resonance (CPMAS 13C-NMR) spectra indicated that synthetic aging techniques did alter SdOM structure to some degree, but these changes did not affect SdOM affinity for pyrene. Aging delayed pyrene mineralization and increased pyrene concentrations extracted from bulk sediment and humic fractions. Aging also reduced the toxicity of sediment humin. Pyrene-4,5-dione and pyrene cis-4,5-dihydrodiol were identified in extracts of aged sediments by 13C-NMR and gas chromatography mass spectrometry, respectively.

[1- 13 C]acenaphthene, a tracer compound with a nuclear magnetic resonance (NMR)-active nucleus at the C-1 position, has been employed in conjunction with a standard broad-band-decoupled 13 C-NMR spectroscopy technique to study the biodegradation of acenaphthene by various bacterial cultures degrading aromatic hydrocarbons of creosote. Site-specific labeling at the benzylic position of acenaphthene allows 13 C-NMR detection of chemical changes due to initial oxidations catalyzed by bacterial enzymes of aromatic hydrocarbon catabolism. Biodegradation of [1- 13 C]acenaphthene in the presence of naphthalene or creosote polycyclic aromatic compounds (PACs) was examined with an undefined mixed bacterial culture (established by enrichment on creosote PACs) and with isolates of individual naphthalene- and phenanthrene-degrading strains from this culture. From 13 C-NMR spectra of extractable materials obtained in time course biodegradation experiments under optimized conditions, a number of signals were assigned to accumulated products such as 1-acenaphthenol, 1-acenaphthenone, acenaphthene-1,2-diol and naphthalene 1,8-dicarboxylic acid, formed by benzylic oxidation of acenaphthene and subsequent reactions. Limited degradation of acenaphthene could be attributed to its oxidation by naphthalene 1,2-dioxygenase or related dioxygenases, indicative of certain limitations of the undefined mixed culture with respect to acenaphthene catabolism. Coinoculation of the mixed culture with cells of acenaphthene-grown strain Pseudomonas sp. strain A2279 mitigated the accumulation of partial transformation products and resulted in more complete degradation of acenaphthene. This study demonstrates the value of the stable isotope labeling approach and its ability to reveal incomplete mineralization even when as little as 2 to 3% of the substrate is incompletely oxidized, yielding products of partial transformation. The approach outlined may prove useful in assessing bioremediation performance.

Non-covalent interactions between 13C-labeled acenaphthenone (13C-labeled in the carbonyl position) and Suwannee River fulvic acid in a methanol/D2O solvent have been examined using 13C NMR T1 relaxation measurements. The influence of solvents upon the non-covalent interactions were assessed by examining acenaphthenone in pure solvents of varying solvation capacity (chloroform, methanol, methanol/D2O). Interactions with fulvic acid were examined as a function of acenaphthenone and fulvic acid concentrations, fulvic acid counter-cation (H+ or Na+), and pH. In the presence of fulvic acid in a methanol/D2O solvent, three non-covalent interactions were identified: a weak sorption interaction between acenaphthenone and fulvic acid, an enhanced solubilization of acenaphthenone by fulvic acid, and an interaction between just the solvent and acenaphthenone. The enhanced solubilization is hypothesized to arise from fulvic acid forming hydrophobic regions that are predominantly solvated with methanol and have excl...

The biodegradation of 13 C-labeled 2,4-dichlorophenol (DCP labeled at the C-2 and C-6 positions), in the presence and absence of natural organic matter (NOM), by the white-rot fungus Phanerochaete chrysosporium, was examined using 13 C-nuclear magnetic resonance (NMR). Using this method permitted the chemistry occurring at or near the labeled site to be followed. The formation of alkyl ethers and alkene ethers was observed. No aromatic by-products were detected. indicating that aromatic compounds are quickly degraded. Examining the reaction with time shows the exponential removal of 2,4-DCP and the consequential formation of labeled by-products, whose concentration reaches a maximum just before all 2,4-DCP is consumed. After this, the by-products degrade exponentially. The presence of NOM causes 2,4-DCP to be removed from the aqueous phase more quickly than in its absence and also causes the by-products to reach their maximum concentration much earlier. Degradation of the by-products occurs at a much greater rate in the presence of NOM. One hypothesis for this behavior is that the NOM interacts with 2,4-DCP and its by-products, allowing them to be incorporated into the fungal biomass. 13 C-nuclear magnetic resonance spectra of the fungal biomass after NaOH extraction show the presence of alkanes and a small amount of 2,4-DCP

Tetramethylammonium hydroxide (TMAH) thermochemolysis has been applied to the diagenetically resistant aliphatic biopolymer cutan derived from the leaf cuticles of Agave americana. Data obtained from the cutan sample using this new analytical method are vastly different in comparison with conventional flash pyrolysis data of the same sample. Under conventional flash pyrolysis conditions, the dominant products were alkanes, alkenes, and α, ω-alkadienes. Under thermochemolysis conditions, however, the cutan biopolymer yielded fatty acid methyl esters (FAMEs) of varying carbon chain length, along with a large number of benzenecarboxylic acid methyl esters that point to the possibility of a chemical structure containing functionalized benzene rings. This type of structure is absent from the current structural model of cutan.

Flash pyrolysis in the presence of tetramethylammonium hydroxide (TMAH) has been utilized for the characterization of lignin in a gymnosperm (pine), angiosperm (alder), and nonwoody ( Juncus effusus L.) vascular plant tissue. The gymnosperm tissue yielded primarily methylated guaiacyl derivatives resulting from cleavage of lignin β-O-4 bonds and subsequent methylation of acidic hydroxy groups. The angiosperm tissue also yielded guaiacyl-type compounds in addition to an analogous suite of methylated syringyl lignin derivatives. The nonwoody angiosperm yielded methylated cinnamyl lignin derivatives in addition to methylated guaiacyl and syringyl compounds. Analysis of alder wood with this technique at a low temperature of 310°C has demonstrated that the dominant reaction with TMAH is mainly a thermally assisted chemolytic degradation rather than degradation induced by pyrolytic bond cleavage. Accordingly, we now call the technique TMAH thermochemolysis.

13 C NMR spectroscopy along with 13 C-labeling techniques has been used in a model study examining the thermal stability of a jet fuel sample mixed with 5% benzyl alcohol to demonstrate the usefulness of the combined labeling and NMR techniques for tracing the fate of reactants. A Jet A-1 fuel laced with α- 13 C-labeled benzyl alcohol was thermally stressed in a manner similar to that reported by Coleman et al. 13 C labeling at the α position of the benzyl alcohol makes it possible to clearly follow the reaction pathway of the labeled α carbon in the presence of complex mixtures of hydrocarbons whose carbons are at natural abundance levels (1%). 13 C NMR data showed that toluene and benzene were the major reaction products with the production of benzoic acid and benzaldehyde as intermediates. This paper demonstrates the usefulness oc 13 C NMR as a method in delineating the reactions of specific compounds in complex reaction mixtures.

A novel application of a standard NMR technique has been employed to characterize the enzymatic coupling of a pollutant (2,4-dichlorophenol, 2,4-DCP) to humic material. The application involves the use of 2,4-DCP labeled with 13 C at specific molecular sites in combination with broad-band decoupled 13 C NMR to determine the nature of bonding interactions with Minnesota peat humic acid. Any alteration in the chemical structure of the 2,4-DCP due to coupling with the humic acid results in changes in the 13 C chemical shifts of the labeled carbons which are indicative of the site and type of bonding interaction. These data provide direct evidence for the formation of covalent bonds between the pollutant and a humic acid via enzymatic coupling

Modern agricultural practices have contributed to the accumulation of herbicides, pesticides and their decomposition products in the soil. These pollutants are known to interact with soil organic matter to form covalent and/or noncovalent bonding associations. The covalent bonds are thought to result from addition or oxidative coupling reactions, some of which may be catalyzed by oxidoreductive enzymes. Noncovalent associations include such interactions as ion exchange, hydrogen bonding, protonation, charge transfer, ligand exchange, coordination through metal ions, van der Waals forces, and hydrophobic bonding. The association of pollutants with soil organic matter is an area of study that is of extreme interest for two reasons. First, dissolved organic matter present in lakes and streams is known to enhance the solubility of pollutants, which poses a real threat to the quality of fresh water supplies. Therefore, if we are to predict the movement of pollutants in the water table we need to have a mechanistic understanding of their interactions with dissolved humic materials. Second, early studies had indicated that some pollutants chemically bind to humic materials, thus reducing the risk of further transport and dispersion. If this chemical binding of the pollutants is irreversible, then this process may serve as a natural means for their detoxification. Regardless of the type of association, the first task in any mechanistic study is to characterize the reaction products structurally. In the case of noncovalent binding mechanisms, studies have focused on the physical characteristics of the process and not on the structure of the associated pollutant. Association studies are used to determine the sorption kinetics and transport of pollutants as well as their association constants. These types of studies utilize various techniques such as batch sorption, gas-purge desorption, column adsorption, and miscible displacement. All of these techniques are only capable of providing quantitative information on the amount of pollutant sorbed by a substrate. The study of the covalent binding of pollutants to humic substances has utilized 14C labeling in addition to various spectrometric techniques such as ultraviolet (UV) difference, fluorescence polarization and infrared (IR) spectroscopy.

Este trabajo constituye el Capítulo 5 del libro.-- El DOI del volumen 651 es: 10.1021/bk-1996-0651., Nuclear magnetic resonance (NMR) spectroscopy has been used to characterize soil organic matter and study soil humification processes for nearly two decades, but only recently it has been considered a valuable analytical method in modern soil science. Technological and theoretical advances in the early development of NMR resulted in increased sensitivity and resolution of the NMR spectra of humic materials in soils. In turn, the increased utility of NMR led to the widespread initial use of this technique which is documented in the scientific literature by numerous NMR studies to obtain structural information on soil organic matter. Since those early applications spanning the 1970's and 1980's, a general hiatus has limited new developments in the field of soil science and the technique became routine in its application. Recently, some new applications involving isotope labeling combined with both 13C and 15N NMR has renewed interest in NMR as the premier technique for modern soil science research. This article reviews these recent developments.

A one-semester laboratory has been developed in which principles of general chemistry (aqueous acid–base equilibria, kinetics, thermodynamics, chromatographic separations, spectroscopy) are presented in the context of environmental aquatic chemistry. Some of the experiments in the sequence are modified slightly from standard experiments, but new experiments have been added to teach kinetics and separations in the context of halocarbon removal from water. A final capstone project on wastewater treatment reinforces and integrates concepts taught in the earlier experiments. Survey data confirm that the contextual format is stimulating for students because of added relevance to real-world environmental issues.