Bulk chemical characteristics of dissolved organic matter in the ocean.

Dissolved organic matter (DOM) is the largest reservoir of reduced carbon in the oceans. The nature of DOM is poorly understood, in part, because it has been difficult to isolate sufficient amounts of representative material for analysis. Tangential-flow ultrafiltration was shown to recover milligram amounts of >1000 daltons of DOM from seawater collected at three depths in the North Pacific Ocean. These isolates represented 22 to 33 percent of the total DOM and included essentially all colloidal material. The elemental, carbohydrate, and carbon-type (by (13)C nuclear magnetic resonance) compositions of the isolates indicated that the relative abundance of polysaccharides was high ( approximately 50 percent) in surface water and decreased to approximately 25 percent in deeper samples. Polysaccharides thus appear to be more abundant and reactive components of seawater DOM than has been recognized.

Organic matter in a coal ball: peat or coal?

Chemical analyses of morphologically preserved organic matter in a Carboniferous coal ball reveal that the material is coalified to a rank approximately equal to that of the surrounding coal. Hence, the plant tissues in the coal ball were chemically altered by coalification processes and were not preserved as peat.

Characterization of organic matter in pristine and contaminated coastal marine sediments using solid-state 13C NMR, pyrolytic and thermochemolytic methods: a case study in the San Diego harbor area.

Chemical composition of coastal marine sedimentary organic matter (SDOM) is a function of natural and anthropogenic inputs to the system. In this study a combination of analytical techniques: 13C nuclear magnetic resonance (NMR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and tetramethylammonium hydroxide thermochemolysis-gas chromatography/mass spectrometry (TMAH thermochemolysis-GC/MS) were used to study the contribution of hydrophobic organic contaminants and terrestrial OM to the SDOM. Sediments were collected from two sites in the San Diego Bay: Paleta Creek, which is contaminated, and Coronado Cayes, which is relatively pristine. Concentrations of polycyclic aromatic hydrocarbons (PAHs) at both sites, as determined by ultrasonically assisted lipid extraction are found to be higher in the surface layer, to generally decrease with depth, and to be present at about two orders of magnitude higher concentration at the contaminated site as compared to the pristine site. The sediment samples were partially deashed with HF/HCI treatment before further analysis. 13C-NMR spectra of the Paleta Creek samples show a higher aromatic carbon content and a distinct phenolic carbon peak. This suggests a large input from terrestrial carbon (lignin). Data from both Py-GC/MS and TMAH thermochemolysis-GC/MS support this and indicate the presence of lignin-derived residues, primarily of the guaiacyl type at the contaminated site. In contrast, SDOM at the Coronado Cayes site exhibits less terrestrial input. In general, the SDOM resembles soil OM rather than typical marine SDOM. Chemical analyses of the lipid-extracted, partially deashed sediments, does not reveal the presence of any PAHs.

Formation of heteroaromatic nitrogen after prolonged humification of vascular plant remains as revealed by nuclear magnetic resonance spectroscopy.

In the search for the mechanisms involved in the immobilization of organic nitrogen in humified remains of vascular plants, the efforts of the present investigation were directed toward the examination of the transformation of nitrogenous compounds during the peat and coal stage by means of solid-state nuclear magnetic resonance (NMR) spectroscopy. While accumulation of heteroaromatic-N is not detected in most of the studied peat layers, a clear shoulder in the chemical shift region of pyrrole- or indole-N is observed in the solid-state 15N NMR spectrum of material from the deepest (and thus oldest) peat layer underlying the sapropel from Mangrove Lake, Bermuda (10000 years). This points to the assumption that transformation of nitrogen occurs between an advanced stage of peatification and an early stage of coalification. The observed sudden alteration in nitrogen functionality indicates that continuous accumulation of newly synthesized or selectively preserved biogenic structures is not responsible for the presence of heteroaromatic-N in these fossilized deposits. It seems rather likely that abiotic conditions, occurring during advanced sediment maturation, have an effect on the observed N transformation. With increasing coalification, pyrrole-type-N becomes the dominant form in the macromolecular coal network. Pyridine-type-N was only detected in a coal of anthracite rank.

Metabolie and Cardiorespiratory Responses of Young Women to Skipping and Jogging.

In brief: To compare jogging and skipping with respect to metabolic demand, musculoskeletal stress, and perceived exertion, nine women (aged 18 to 29) were studied while jogging and skipping at treadmill speeds of 4.0, 4.8, and 5.4 mph. Data for V O2, heart rate, and perceived exertion were collected, and the subjects provided subjective ratings of musculoskeletal stress. The results showed that skipping imposed significantly greater metabolic demands and caused higher heart rates than jogging at each speed. In additon, skipping was rated as more stressful to the legs and ankles and less enjoyable. Thus skipping appears to be a stronger cardiorespiratory training stimulus than jogging for a given pace, but a less enjoyable activity.

Effect of Michael adduction on peptide preservation in natural waters.

The reaction of peptides with chemicals already present in natural waters (such as polycyclic aromatic hydrocarbons) is one method that has been suggested to preserve peptides for the longer term. In this study we test whether the reaction of tetrapeptides with a model quinone can help stabilise the peptide in one polluted riverine system, Elizabeth River in Virginia, USA. We found that there is almost no difference in rate constants between the peptide and its quinone adduct (e.g. 6.62 versus 6.86 per day for AVFA and its respective adduct). However, when monitoring the removal of the adduct from natural water, we identified two new compounds that are formed as a result of its decomposition. Using tandem mass spectrometry we identified potential structures and mechanisms for the formation of these new compounds. These new compounds are more recalcitrant than their parent peptide-quinone adduct, since they remain in solution for 3-10 times longer. Based on our findings we postulate that the reaction of peptides with quinones can help preserve sections of the original peptide following an initial rearrangement of the original adduct, potentially explaining why seemingly labile peptides are observed in most natural waters.

Evolution of organic matter during composting of different organic wastes assessed by CPMAS 13C NMR spectroscopy.

In this paper, the evolution of organic matter (OM) during composting of different mixtures of various organic wastes was assessed by means of chemical analyses and CPMAS (13)C NMR spectroscopy measured during composting. The trends of temperatures and C/N ratios supported the correct evolution of the processes. The CPMAS (13)C NMR spectra of all composting substrates indicated a reduction in carbohydrates and an increase in aromatic, phenolic, carboxylic and carbonylic C which suggested a preference by microorganisms for easily degradable C molecules. The presence of hardly degradable pine needles in one of the substrates accounted for the lowest increase in alkyl C and the lowest reduction in carbohydrates and carboxyl C as opposite to another substrate characterized by the presence of a highly degradable material such as spent yeast from beer production, which showed the highest increase of the alkyl C/O-alkyl C ratio. The highest increase of COOH deriving by the oxidative degradation of cellulose was shown by a substrate composed by about 50% of plant residues. The smallest increases in alkyl C/O-alkyl C ratio and in polysaccharides were associated to the degradation of proteins and lipids which are major components of sewage sludge. Results obtained were related to the different composition of fresh organic substrates and provided evidence of different OM evolution patterns as a function of the initial substrate composition.

Chemical characteristics of dissolved organic matter during composting of different organic wastes assessed by (13)C CPMAS NMR spectroscopy.

This research aimed at assessing the chemical changes occurring in DOM extracted from different composting substrates by means of (13)C CPMAS NMR spectroscopy. During composting a reduction of carbohydrates and an increase of aromatic, phenolic, carboxylic and carbonylic C were observed. The highest increase in alkyl C and the lowest increase in aromatic C were explained by the presence of hardly degradable pine needles in the substrate, whereas the highest reduction in carbohydrates and the highest increase of the alkyl C/O-alkyl C ratio were attributed to the presence of highly degradable materials such as spent yeast from beer production.

Colloidal cutin-like substances cross-linked to siderophore decomposition products mobilizing plutonium from contaminated soils.

Relatively recently, inorganic colloids have been invoked to reconcile the apparent contradictions between expectations based on classical dissolved-phase Pu transport and field observations of "enhanced" Pu mobility (Kersting et al. Nature 1999, 397, 56-59). A new paradigm for Pu transport is mobilization and transport via biologically produced ligands. This study for the first time reports a new finding of Pu being transported, at sub-pM concentrations, by a cutin-like natural substance containing siderophore-like moieties and virtually all mobile Pu. Most likely, Pu is complexed by chelating groups derived from siderophores that are covalently bound to a backbone of cutin-derived soil degradation products, thus revealing the history of initial exposure to Pu. Features such as amphiphilicity and small size make this macromolecule an ideal collector for actinides and other metals and a vector for their dispersal. Cross-linking to the hydrophobic domains (e.g., by polysaccharides) gives this macromolecule high mobility and a means of enhancing Pu transport. This finding provides a new mechanism for Pu transport through environmental systems that would not have been predicted by Pu transport models.

Screening of human enteric microorganisms for potential biotransformation of polycyclic aromatic hydrocarbons.

This study examined the potential for metabolism of select polycyclic aromatic hydrocarbons (PAH) by human enteric microorganisms. Experiments were performed under anaerobic conditions with various combinations of enteric microbial suspensions, PAH concentrations, nutrient mixtures, and time courses. No PAH metabolites were detected upon GC-TOF-MS analysis of samples digested by tetramethylammonium hydroxide thermochemolysis. No mineralization of (14)C-labeled phenanthrene was observed. These results suggest the lack of partial or complete metabolism of PAHs by enteric microorganisms and therefore the absence of major bioactivation pathways that would expose intestinal lining to potentially carcinogenic PAH metabolites.

Steroids as Sewage Specific Indicators in New York Bight sediments.

Sediments of the New York Bight were examined for steroidal compounds and found to contain relatively large amounts of coprostanol and 24 beta-ethyl coprostanol. These steroids were found to be derived from sewage, and it is suggested that they be used as sewage tracers in marine sediments.

Comparative analysis of the chemical composition of mixed and pure cultures of green algae and their decomposed residues by C nuclear magnetic resonance spectroscopy.

It is known that macromolecular organic matter in aquatic environments, i.e., humic substances, is highly aliphatic. These aliphatic macromolecules, predominantly paraffinic in structure, are prevalent in marine and lacustrine sediments and are believed to originate from algae or bacteria. A comparative study of mixed and pure cultures of green algae and their decomposed residues was performed by using solid-state C nuclear magnetic resonance spectroscopy as the primary analytical method. Results obtained in this study confirm the presence of components that are chemically refractory and that are defined as alghumin and hydrolyzed alghumin. These were detected in heterogeneous, homogeneous, and axenic biomasses composed of several genera of Chlorophyta. Although the chemical composition of algal biomass varied with culture conditions, the chemical structure of the alghumin and hydrolyzed alghumin, demonstrated by C nuclear magnetic resonance spectroscopy appeared to be constant for members of the Chlorophyta examined in this study. The alghumin was dominated by carbohydrate-carbon, with minor amounts of amide or carboxyl carbon and paraffinic carbon, the latter surviving strong hydrolysis by 6 N HCI (hydrolyzed alghumin). Bacterial decomposition of heterogeneous algal biomass labeled with C was conducted under both aerobic and anaerobic conditions to determine chemical structure and stability of the refractory material. The refractory fraction ranged from 33% in aerobic to 44% in anaerobic cultures. The refractory fraction recovered from either aerobic or anaerobic degradation comprised 40% alghumin, which represented an enrichment by 10% relative to the proportion of alghumin derived from whole cells of algae. The paraffinic component in the hydrolyzed alghumin of whole algal cells was found to be 1.8% and increased to 5.1 and 6.9% after aerobic and anaerobic bacterial degradation, respectively. It is concluded that members of the Chlorophyta contain a common insoluble structure composed of paraffinic carbon that is resistant to chemical and bacterial degradation under conditions used in this study. The paraffinic structure is identical to those constituting humin of aquatic origin. Thus, alga-derived macromolecular compounds deposited in aquatic environments (alghumin) probably contribute to sedimentary humic substances.

Structural investigations of hydrogen cyanide polymers: new insights using TMAH thermochemolysis/GC-MS.

Hydrogen cyanide polymers form spontaneously from HCN and traces of base catalysts. It is probable that these polymers played an important role in the early stages of chemical evolution. Nevertheless, their full structural characterization has still not been accomplished. A number of mass spectrometric methods have now been applied to this structural problem including FAB-MS, thermal desorption EI-MS, ESI-MS, APCI-MS and off-line TMAH thermochemolysis/GC-MS. This latter method causes bond cleaveage and in situ methylation producing a suite of products which provides valuable insight into the substructural features of HCN polymers and also promises to serve as a sensitive diagnostic tool for detecting the presence of HCN polymers in samples from diverse sources.

Use of 13C nuclear magnetic resonance to assess fossil fuel biodegradation: fate of [1-13C]acenaphthene in creosote polycyclic aromatic compound mixtures degraded by bacteria.

[1-13C]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 13C-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 13C-NMR detection of chemical changes due to initial oxidations catalyzed by bacterial enzymes of aromatic hydrocarbon catabolism. Biodegradation of [1-13C]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 13C-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.