Paul F. Greenwood

A possible chlorophycean affinity of some Neoproterozoic acritarchs

Abstract Two taxa of Neoproterozoic acritarchs of unknown affinity, Multifronsphaeridium pelorium and Species A, are analysed by electron microscopic (SEM, TEM) and chemical (micro-FTIR, pyrolysis GC–MS, thermal desorption–MS) methods. Both acritarch species are characterised by multi-branched processes and a remnant trilaminar sheath (TLS) structure. The TLS-bearing wall structures in these acritarchs suggest a possible biological affinity to chlorophyte algaenan. The molecular data obtained from the two acritarchs were generally similar and also consistent with a chlorophycean affinity. A significant aliphatic moiety is evident in these acritarchs as a short-chain series of n -alkene/alkane pyrolysates and prominent aliphatic IR bands. The restricted molecular-weight range ( 20 ) of the n -alkene/alkane doublets and the lack of isoprenoid and other branched alkanes in the pyrolysates suggest a low degree of branching in the aliphatic component of these acritarch macromolecules. The significant methyl (CH 3 ) IR signal was attributed to the terminal groups of short n -alkyl moieties. Alkylbenzenes, alkylphenols and alkylindoles were also significant pyrolysis products, indicating an aromatic component, although the latter two components may be attributed to artificially- and/or diagenetically-formed melanoidin moieties. The macromolecular structure of Multifronsphaeridium sp. and Species A consists of short n -alkylpolymethylenic chains, probably linked via ether/ester bonds, with possibly a small aromatic content. This study presents ultrastructural and molecular evidence of a genetic relationship between Neoproterozoic acritarchs and Chlorophyceae.

Laser Micropyrolysis GC-MS of lignin

Abstract The potential for using lasers as a highly directional thermal source in analytical pyrolysis studies is further investigated by the laser micropyrolysis GC–MS analysis of lignin moieties. Two woods representative of the main types of lignin (i.e. gymnosperm/guaiacyl producing and angiosperm/syringyl and guaiacyl producing) were separately analysed by both laser micropyrolysis GC–MS and the longer used pyroprobe pyrolysis GC–MS. High levels of correlation were observed from the laser and pyroprobe pyrograms of both lignins.

Applications of laser micropyrolysis-gas chromatography-mass spectrometry

Abstract An apparatus which couples a laser microprobe with a GC–MS has recently been constructed in our laboratories to facilitate analytical micropyrolysis studies. The utility and versatility of the technique is demonstrated through the analysis of micro-sized quantities of various organic fossils. Results are reported from a torbanite coal, Green River oil shale, Tasmanite oil shale, an isolated Tasmanites microfossil and oil-bearing fluid inclusions. A diverse range of aliphatic products including distributions of n-alkene/n-alkane pairs, isoprenoids, polycyclic biomarkers and various alkylaromatics have been detected from these materials. The analytical credibility of the laser micropyrolysis GC–MS technique is confirmed by the favourable comparison of the laser derived molecular data to corresponding data obtained from more traditional methods.

Tricyclic terpenoid composition of Tasmanites kerogen as determined by pyrolysis GC-MS

The high abundance with which tricyclic terpenoids have previously been detected in Tasmanite oil shales has led to the strong suspicion that the source of these compounds is the Tasmanites microfossil prevalent in these oil shales. In this study, the hydrocarbon composition of a Tasmanite oil shale and isolated Tasmanites were separately investigated by laser micropyrolysis gas chromatography–mass spectrometry, a recently developed technique that facilitates the analysis of small samples such as microfossils. Major products comprised C19–C28 tricyclic terpanes, including the ubiquitous 13-methyl, 14-alkylpodocarpanes, as well as a number of additional tricyclic terpane isomers, a C19 monoaromatic hydrocarbon, and several C19–C21 tricyclic terpenes (one and two orders of unsaturation). There have been few previous reports on the tricyclic terpenes and their production is likely attributable to the pyrolytic cleavage of analogous (probably saturated) tricyclic precursors within the macromolecular biopolymer. The only major difference between the tricyclic terpenoid compositions observed from these samples was the absence of the less concentrated oil shale products in the Tasmanites analyses, probably due to the lower organic content of the preextracted fossil. The very similar tricyclic content of both samples strongly supports the proposal of an inherent relationship between the Tasmanites and tricyclic terpenoid production. The integrity of the laser data was confirmed by comparison to a conventional data set obtained by the pyroprobe pyrolysis of the Tasmanite oil shale.

Biomarkers reveal the role of photic zone euxinia in exceptional fossil preservation: An organic geochemical perspective

Photic zone euxinia (PZE) has proven important for elucidating biogeochemical changes that occur during oceanic anoxic events, including mass extinction and conditions associated with unique fossil preservation. Organic geochemical analyses of a 380 Ma invertebrate fossil, which included well-preserved soft tissues, from the Gogo Formation (Canning Basin, Western Australia) showed biomarkers and stable isotopic values characteristic of PZE and a consortium of sulfate-reducing bacteria, which lead to exceptional fossil and biomarker preservation. The carbonate concretion contained phytoplankton, green sulfur bacteria (Chlorobi), and sulfate-reducing bacteria biomarkers with an increasing concentration toward the nucleus where the fossil is preserved. The spatial distribution of cholestane unequivocally associated with the fossilized tissue and its high relative abundance to the total steranes suggest that the fossil is a crustacean. The presence of an active sulfur cycle in this Devonian system, including sulfate reduction and the resulting PZE, played a pivotal role in the preservation of soft tissue from the fossil and its associated low-maturity biomarker ratios.

Microbial Community Analysis of Human Decomposition on Soil

Human decomposition is a complex process, involving a multitude of microbial species. Currently, little is known about the microbial species and processes that occur as cadavers decompose, particularly in outdoor environments. With the development of molecular ecology tools that allow the study of complex microbial communities, the ‘black box’ of the microbiology associated with decomposition is being opened. A preliminary study was performed to evaluate the changes in the soil bacterial and fungal communities that occur in response to human cadaver decomposition, and to assess the potential for using such changes in either of these two microbial communities for forensic time-since-death estimation. Terminal restriction fragment length polymorphism (T-RFLP) and phospholipid fatty acid (PLFA) analyses were performed on soil samples collected from beneath decomposing human cadavers at the University of Tennessees Forensic Anthropology Centre. The soil fungal and bacterial communities showed significant changes in response to decomposition events, with some succession patterns emerging as decomposition progressed. Evidence of sequential changes occurring in the soil microbial community provides support for the idea that specific microbes could be used as time-since-death biomarkers, although major differences in the way replicate cadavers decomposed in this study suggested that both the bacterial and fungal communities may need to be considered to ensure such a method is forensically useful. Some difficulties were also encountered with the polymerase chain reaction (PCR) step in the T-RFLP method being inhibited by soil or decomposition compounds, which suggest that while DNA-based ‘profiling’ methods may be useful for studying the effects of decomposition on soil, other more specific techniques are likely to be most useful in a forensic post-mortem interval context.

Composition of size exclusion fractions of swamp water humic and fulvic acids as measured by solid state NMR and pyrolysis-gas chromatography-mass spectrometry

Abstract Organics from Neranie swamp water, collected from the Myall Lakes district, New South Wales, Australia, have been fractionated by gel permeation chromatography and analysed by 13C nuclear magnetic resonance (NMR) spectroscopy and pyrolysis-gas chromatography-mass spectrometry (py-GC-MS). The results from these techniques demonstrate that: (1) low ( M w daltons ) and high ( M w > 74,830 daltons ) weight average molecular weight humic acid fractions have aliphatic chains which are relatively unbranched compared to those humic acids fractions of intermediate molecular weight. (2) Alcoholic carbon, mainly as carbohydrates, is more predominant in the highest weight average molecular weight material, and carboxylic carbon is more predominant in molecules with M w 2800–8270 daltons. (3) If it is assumed that CP/MAS NMR data are at least semi-quantitative, polyoxyethers or unsaturated ethers account for as much as one half of the oxygen in humic low molecular weight ( M w daltons ) materials. (4) Lignin related components of the fractions concentrate in the region M w = 74,830−27,930 daltons . If there are not multiple lignin sources, these data indicate that lignin degradation is somewhat selective about weak links. (5) The fulvic acids are more homogeneous, with different molecular weight fractions having similar structures.

The analysis of forensic samples using laser micro-pyrolysis gas chromatography mass spectrometry.

Laser micropyrolysis gas chromatography-mass spectrometry is used for the analysis of paint, photocopier toner, and synthetic fiber materials to test the forensic potential of this emerging technology. It uses a laser microprobe to selectively target very small parts of the materials for GC-MS analysis. Whereas the paint and the toner samples were amenable to direct laser pyrolysis, the synthetic fibers proved transparent to the 1064 nm laser radiation. The difficulty with the fibers demonstrates that a specific laser wavelength may not be appropriate for all types of materials. Nevertheless, the fibers were able to be indirectly pyrolyzed by impregnation in a strongly absorbing graphite matrix. A vast array of hydrocarbon pyrolysates was detected from the different materials studied. Unique product distributions were detected from each sample and in sufficient detail to facilitate individual molecular characterization (i.e., molecular fingerprinting). The integrity of the laser data were confirmed by comparison to data obtained from the same samples by the more conventional pyroprobe pyrolysis GC-MS method. The high spatial resolution and selectivity of the laser method may be advantageous for specific forensic applications, however, further work may be required to improve the reproducibility of the data.

Vertical fluxes of hydrocarbons on the Northwest Shelf of Australia as estimated by a sediment trap study

Abstract Sediment traps were deployed on the Northwest Shelf (NWS) of Australia in November 1996, to determine fluxes of organic matter and inorganic elements from the photic zone to deeper waters transecting the Exmouth Shelf to Exmouth Plateau. Dry weight fluxes from the traps ranged from 124 to 616 mg m −2 day −1 and POC fluxes ranged from 22.8 to 43.9. The biogenic hydrocarbons consisted of biomarkers indicative of marine zooplankton, phytoplankton and bacteria. GC analyses also revealed a significant component of petroleum-derived hydrocarbons through the presence of an unresolved complex mixture (UCM) that was approximately 4 times the biogenic hydrocarbon flux at shallow stations and up to 7 times at the most offshore station. The molecular characteristics of these hydrocarbons were investigated using GC-MS and GC-MS-MS and compared with local and regional petroleum accumulations. GC-MS analysis showed the hydrocarbons included n -alkanes, alkylated aromatics plus hopane and sterane biomarkers indicating a mature and moderately degraded crude oil. The sterane and triterpane signatures also indicated that the source rock of this oil was marine sediment with a calcareous lithology and of probable Mesozoic age. Commercially exploited oils of similar composition are mostly not known on the NWS. However, there are indications that there is an active petroleum system with some similar characteristics in the southern Carnarvon Basin as shown by oils of anomalous composition to the Chervil, North Herald and South Pepper fields. These results indicate that exploration strategies in the region should not be confined to oil reserves based on the Upper Jurassic Dingo claystone source.

Chemical fingerprinting of adhesive tapes by GCMS detection of petroleum hydrocarbon products.

Abstract:  Pressure‐sensitive adhesive tapes often represent key evidence of crimes such as assault, rape or homicide; thus, the development of analytical techniques able to contribute to a detailed characterization of these materials is of forensic importance. The gas chromatography‐mass spectrometry (GCMS) analysis of the solvent extractable fractions of a suite of electrical and gaffer adhesive tapes spanning a range of colors and manufacturers identified a number of petroleum‐derived hydrocarbons. Molecular and isotopic analyses of hydrocarbon constituents of complex materials have found wide analytical utility including the forensic investigation of oil spills and arson. Here, we investigate the utility of these techniques for characterizing the hydrocarbon composition of pressure‐sensitive adhesive tapes for forensic correlation purposes. Subtle distinction of tape samples was evident in the GCMS distribution of several hydrocarbon groups including alkyl‐naphthalenes, hopane and sterane biomarkers. Linear discriminant analysis of the abundances of these products provided high level differentiation of tape manufacturer. The distinction of different adhesive tape samples was further extended by measurement of their stable carbon isotopic values. The molecular and isotopic differences of the petroleum content of tapes are consistent with the use of different petroleum materials used in the manufacturing process and demonstrate the benefits of the combined use of complementary oil hydrocarbon characterization approaches. This study reveals the forensic potential of using established petroleum characterization methods for characterizing materials with a petroleum‐derived hydrocarbon element.