Christopher H. Vane

Organic and metal contamination in surface mangrove sediments of South China

Mangrove forests, the intertidal wetlands of the tropics and subtropics, are key ecological habitats that link terrestrial and marine environments. Mangrove forests and adjacent mudflats are increasingly impacted by urban/industrial development in the tropical coastal zone, suffering pollution from multiple sources including but not limited to municipal waste, aquaculture, mariculture and shipping as well as onshore industries and run-off from urban centres (Cuong et al. 2005; Huang et al. 2003; Zheng et al. 2000). Sediments that accumulate in mangroves are potential repositories of anthropogenic pollution because of high total organic carbon content, anaerobic properties and rapid turnover and burial (Marchand et al. 2005; Tam and Yao, 2002). The world wide denigration and loss of mangrove habitats is of global concern given they account for an estimated 11 % of the input of terrestrially-derived carbon into the ocean and about 10 % dissolved organic carbon (DOC) sourced from land; the long term effect of altering the carbon cycle is uncertain (Dittmar et al. 2006; Jennerjahn and Ittekkot, 2002). It has been widely postulated that mangroves afford physical protection against catastrophic storm events such as hurricanes and tsunamis (Alongi, 2007). Recent post-impact surveys along the Tamil Nadu coast follwing the 2004 Indian Ocean tsunami confirmed this notion and demonstrated that man-made structures built behind mangroves were significantly less damaged than their unprotected counterparts (Alongi, 2007).

Chemical signatures of the Anthropocene in the Clyde estuary, UK: sediment-hosted Pb, 207/206Pb, total petroleum hydrocarbon, polyaromatic hydrocarbon and polychlorinated biphenyl pollution records

The sediment concentrations of total petroleum hydrocarbons (TPHs), polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), Pb and 207/206Pb isotope ratios were measured in seven cores from the middle Clyde estuary (Scotland, UK) with an aim of tracking the late Anthropocene. Concentrations of TPHs ranged from 34 to 4386 mg kg−1, total PAHs from 19 to 16 163 μg kg−1 and total PCBs between less than 4.3 to 1217 μg kg−1. Inventories, distributions and isomeric ratios of the organic pollutants were used to reconstruct pollutant histories. Pre-Industrial Revolution and modern non-polluted sediments were characterized by low TPH and PAH values as well as high relative abundance of biogenic-sourced phenanthrene and naphthalene. The increasing industrialization of the Clyde gave rise to elevated PAH concentrations and PAH isomeric ratios characteristic of both grass/wood/coal and petroleum and combustion (specifically petroleum combustion). Overall, PAHs had the longest history of any of the organic contaminants. Increasing TPH concentrations and a concomitant decline in PAHs mirrored the lessening of coal use and increasing reliance on petroleum fuels from about the 1950s. Thereafter, declining hydrocarbon pollution was followed by the onset (1950s), peak (1965–1977) and decline (post-1980s) in total PCB concentrations. Lead concentrations ranged from 6 to 631 mg kg−1, while 207/206Pb isotope ratios spanned 0.838–0.876, indicative of various proportions of ‘background’, British ore/coal and Broken Hill type petrol/industrial lead. A chronology was established using published Pb isotope data for aerosol-derived Pb and applied to the cores.

The molecular composition of lignin in spruce decayed by white-rot fungi (Phanerochaete chrysosporium and Trametes versicolor) using pyrolysis-GC-MS and thermochemolysis with tetramethylammonium hydroxide

Pyrolysis-gas chromatography-mass spectrometry (Py-GC–MS) and off-line thermochemolysis with tetramethylammonium hydroxide followed by GC–MS were used in the molecular characterisation of lignin in spruce wood decayed by Phanerochaete chrysosporium and Trametes versicolor. Mono-methoxyphenols were the main pyrolysis products from the undegraded lignin. Py-GC–MS provided qualitative evidence that 2-methoxy-4-(prop-2-enal)phenol and trans-2-methoxy-4-(1-hydroxy-prop-2-enyl)phenol content decreased whereas 1,2-dihydroxybenzene increased in intensity relative to other products upon fungal decay. Comparison of methylated phenols from thermochemolysis revealed that ratio of methyl 3,4-dimethoxybenzoate to 3,4-dimethoxybenzaldehyde increased from 0.69 in control spruce to 2.3 after decay by P. chrysosporium and 3.7 following growth of T. versicolor. The results indicate that white-rot fungi cleave alkyl side chains of β-O-4 linked mono-methoxyphenylpropane structures between the α–β carbon atoms to give lignin residues enriched in carboxylic acids as well as demethylating methoxy groups attached to aromatic nuclei to give dihydroxybenzene products. Py-GC–MS and thermochemolysis are complementary methods for tracking demethylation of aromatic nuclei and oxidation of alkyl side chains caused by white-rot fungi.

Comparison of Batch Mode and Dynamic Physiologically Based Bioaccessibility Tests for PAHs in Soil Samples

A fed state in vitro methodology capable of use in commercial testing laboratories has been developed for measuring the human ingestion bioaccessibility of polyaromatic hydrocarbons (PAHs) in soil (Fed ORganic Estimation human Simulation Test- FOREhST). The protocol for measuring PAHs in the simulated gastro-intestinal fluids used methanolic KOH saponification followed by a combination of polymeric sorbent solid phase extraction and silica sorbent cartridges for sample cleanup and preconcentration. The analysis was carried out using high pressure liquid chromatography with fluorescence detection. The repeatability of the method, assessed by the measurement of the bioaccessibility of 6 PAHs (benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[ah]anthracene, and indeno[1,2,3-c,d]pyrene) in eleven gas works soils, was approximately 10% RSD. The method compared well with the results from an independent dynamic human simulation reactor comprising of the stomach, duodenal and colon compartments tested on the same soils. The measured bioaccessible fraction of the soils varied from 10-60% for soils containing 10-300 mg kg(-1) PAH (the sum of the six studied) with total organic carbon concentrations in the soils ranging from 1-13%. A multiple regression model showed that the PAH bioaccessible fraction could be explained using the PAH compound, the soil type and the total PAH to soil organic carbon content. The method described here has potential for site specific detailed quantitative risk assessment either to modify the risk estimation or to contribute to the risk evaluation.

Stable carbon isotopes as potential sea-level indicators in salt marshes, North Carolina, USA

We compared the use of δ13C values and C:N ratios from salt-marsh sediments to reconstruct relative sea level (RSL) with an established approach using foraminifera. Analysis of bulk-organic sediment and plant samples collected along transects at two sites in North Carolina, USA demonstrates that sediment δ13C values can be used to distinguish between Spartina alterniflora-dominated low marsh (C photosynthetic pathway, δ13C values from —17.6‰ to 16.1‰) and Juncus roemerianus-dominated high marsh (C 3 photosynthetic pathway, δ13C values from —28.2‰ to —21.8‰) environments. Juncus roemerianus plants undergo little decompositional change in δ13C (average 0.8‰), although there is a clear difference between Spartina alterniflora tissue and bulk-organic sediments (approximately 4‰). C:N ratios on bulk-organic sediment from freshwater upland and salt-marsh environments converge during early diagenesis, rendering them of little use in reconstructing RSL. The utility of δ13C values as a sea-level indicator is limited by the elevational range of C4 plants, making it difficult to recognize salt-marsh subenvironments and improve the precision of RSL reconstructions. Furthermore, Juncus roemerianus-dominated high marsh and freshwater upland sediments cannot be adequately distinguished with δ13C values.

Potential and pitfalls in establishing the provenance of earth-related samples in forensic investigations

ABSTRACT: Earth scientists are often asked to establish or constrain the likely provenance of very small quantities of earth‐related material as part of a forensic investigation. We tested the independent and collective interpretations of four experts with differing analytical skills in the prediction of sample provenance for three samples from different environmental settings. The methods used were X‐ray diffraction, scanning electron microscopy, the assessment of pollen assemblages, and structural characterization of organic matter at the molecular level. Independent interpretations were less accurate than those where multiple techniques were combined. Collective interpretation was very effective in the assessment of provenance for two of the three sites where the mineralogy and plant communities were distinctive. At the other site, although the mineralogical analysis correctly identified the Triassic mudstone soil parent material, Carboniferous spores from domestic coal were initially interpreted as deriving directly from bedrock. Such an interpretation could be a common pitfall owing to anthropogenic redistribution of material such as coal.

Status of organic pollutants in surface sediments of Barnegat Bay-Little Egg Harbor Estuary, New Jersey, USA

Numerous surveys have demonstrated that diffuse pollution from urban-residential run-off and industrial discharges can adversely impact salt marsh and tidal creek sediment quality (Barrett & McBrien, 2006; Fox et al., 2001; Iannuzzi et al., 1995; Long et al., 1995; Sanger et al., 2004; White et al., 2005). The impact of shipping activities, including major discharge of fuel oil onto salt marshes, has also been reported (White et al., 2005). However, few studies have assessed organic pollution accumulating in salt marshes with watersheds that are mainly comprised of forests and wetlands but which have major residential areas located off-shore of the mainland. The salt marshes of Barnegat Bay-Little Egg Harbor Estuary, southeast New Jersey represent one such geographical setting (Fig .1). The shallow (17 m), narrow (3-9 mile) bay is separated from the Atlantic Ocean by a back barrier island complex (Long Beach Island) which is heavily developed and a major area of tourism (Fig. 1). The salt marshes are protected and managed as part of the Edwin B. Forsythe National Wildlife Refuge, this comprises 186 km of wetlands and 145 km of salt marshes and has a mixed pattern of watershed land use such as forestry (45.9 %), wetlands (25.2 %), urban/residential (19.5 %) and agricultural (6.6 %).

Palaeoecological and possible evolutionary effects of early Namurian (Serpukhovian, Carboniferous) glacioeustatic cyclicity

Early Namurian (Serpukhovian, Carboniferous), sedimentary cycles in the Throckley and Rowlands Gill boreholes, near Newcastle upon Tyne, UK, consist of fossiliferous limestones overlain by (usually unfossiliferous) black mudstone, followed by sandstones and often by thin coal seams. Sedimentological and regional geological evidence suggests that the largest are high-amplitude cycles, probably of glacioeustatic origin. δ13C (bulk organic matter) delineates marine and non-marine conditions because of the large difference between terrestrial and marine δ13C, and indicates that full marine salinity was only intermittent and resulted from glacioeustatic marine transgression superimposed on a background of inundation by freshwater from large rivers, which killed off the marine biota. Palynology suggests that plant groups, including ferns and putative pteridosperms, were affected by changing sea level, and that there is a theoretical possibility of connection between cyclicity and the first appearance of walchiacean conifer-like monosaccate pollen such as Potonieisporites. Long-term terrestrial and marine increasing δ13C (organic) may reflect the onset of major glaciation in Gondwana, as there is evidence to suggest that the two are coeval, but no specific mechanism can be suggested to link the trends.

Proxies for land plant biomass: closed system pyrolysis of some methoxyphenols

Methoxyphenols can be used as proxies for terrestrial biomass when investigating the chemical changes in lignin during hydrothermal alteration. The closed system microscale pyrolysis of 2-methoxyphenol (2-MOP) and 2,6-dimethoxyphenol (2,6-DMP), in the presence of water vapour, has been studied in borosilicate glass vessels. 2-MOP was heated isothermally at temperatures of 330°C for 96 h and 2,6-DMP was heated isothermally at 300°C for 118 h. Pyrolysis of the model compound 2-MOP gave a simple product distribution which was composed mainly of 1,2-dihydroxybenzene with lower amounts of 2-methylphenol and phenol. The prominent reaction products from heating 2,6-DMP were 1,2-dihydroxy-6-methoxybenzene and 2-methoxy-6-methylphenol, with minor amounts of 2-MOP, 1,2-dihydroxybenzene and 2-methylphenol. The decreasing amounts of 2,6-DMP with heating time and the concomitant increase in the amounts of 1,2-dihydroxy-6-methoxybenzene suggested that demethylation had occurred.

Investigating the record of Permian climate change from argillaceous sedimentary rocks, Oman

A standard method for the analysis of carbon isotope composition of bulk organic matter (δ13Cbulk) in palaeoenvironmental and stratigraphic studies of sedimentary basins associated with hydrocarbons is suggested. This method includes the removal of interstitial hydrocarbon within the sediments, which is shown to have a negative effect on δ13C. Using the method, a δ13Cbulk trend (c. −21 to −24‰) was found within the Lower Permian Al Khlata and lower Gharif formations of Thuleilat-16 and -42 well sections, south Oman. Palaeontological and sedimentological evidence indicates considerable palaeoenvironmental change, from a cold climate lowland fern flora and upland primitive conifer flora low in the sequence, to a lowland cycad-like and upland glossopterid or other gymnospermous flora higher in the sequence. The lithologies range from glacial diamictite at the base to calcrete horizons and redbeds at the top. It is therefore likely that the δ13Cbulk trend is related to palaeoenvironmental change.