Hydropyrolysis of algae, bacteria, archaea and lake sediments; insights into the origin of nitrogen compounds in petroleum     

Barry Bennett  Arnaud Lager  Christopher A. Russell  Gordon D. Love  Stephen R. Larter 《Organic Geochemistry》2004,35(11-12):1427

Nitrogen compounds are ubiquitous in fossil fuels and yet our understanding of their origins in the geosphere is limited. In this study, high hydrogen pressure pyrolysis was performed on sample material representing potential contributors to sedimentary organic matter (algae, bacteria and archaea) and sediments representing early diagenetic accumulations from Lake Pollen (Norway) and Priest Pot (UK). Previous workers demonstrated the structurally conservative nature of high hydrogen pressure pyrolysis in that the technique maximizes the yields of covalently bound hydrocarbon biomarkers from organic matter without adversely affecting their stereochemistry (Love et al., 1995). Release of covalently bound biomarkers in high yields from kerogen via catalytic hydropyrolysis. In this study, the types and distributions of organic nitrogen compounds in the hydropyrolysates were characterised under similar conditions to such experiments where biomarker hydrocarbons undergo minimal rearrangement. Compounds identified by gas chromatography–mass spectrometry included alkyl-substituted indoles, carbazoles, benzocarbazoles, quinolines and benzoquinolines.Indoles are present in all hydropyrolysates, suggesting a common origin. A potential source of indoles is represented by tryptophan which was shown to degrade through a series of alkylated intermediates to indole. Carbazole, quinoline and benzoquinoline were also found in the hydropyrolysates of algae, bacteria and archaea. The presence of these petroleum-related nitrogen compounds in hydropyrolysates generated from biomass suggests an early origin for petroleum nitrogen compounds. A potential source of naturally occurring nitrogen compounds such as that in the alkaloids has yet to be realised.Benzocarbazoles were absent from hydropyrolysates of algae, bacteria and archeae, but present in those from recent sediments, suggesting their presence may be related to processes occurring during early diagenesis at, or immediately below, the sediment–water interface. In sediments from Lake Pollen, changes in the benzocarbazole ratio [a]/([a] + [c]) ratio coincides with the interval described as a transition from fjord to lake environment, suggesting that benzocarbazoles are sensitive to changes in depositional environment and may have potential to act as a marker for environmental conditions.  相似文献   

The mechanism of Re enrichment in arc magmas: evidence from Lau Basin basaltic glasses and primitive melt inclusions   总被引：2，自引：0，他引：2  

Weidong Sun  Victoria C Bennett 《Earth and Planetary Science Letters》2004,222(1):101-114

Rhenium and other trace element data were obtained in situ by laser ablation ICP-MS analysis of submarine-erupted volcanic glasses and olivine-hosted melt inclusions from the Valu Fa Ridge, the south tip of the Lau Basin, in the southwestern Pacific Ocean. The chemistry of the Lau Basin basaltic glasses changes systematically from compositions similar to MORB in the Lau Spreading Centers, to more arc-like compositions in the Valu Fa Ridge, providing geochemical profiles both along the Lau Spreading Centers (ridges) and across the Valu Fa Ridge. The east seamount samples of the Valu Fa Ridge have diagnostic trace element ratios (Ba/Nb, Nb/U, Ce/Pb) close to global arc averages, with high Ba/La, indicating addition of considerable amounts of subduction-released fluids. In contrast, samples from the west seamount and the Lau Spreading Centers show a smaller influence from subduction fluids. The variable degrees of subduction influences apparent in the chemistry of these suites provide an ideal means to explore the mechanisms of Re enrichment in undegassed arc magmas. All of the analyzed arc melts have significantly higher Re concentrations than previously published, largely subaerially erupted samples, confirming that high Re is a characteristic of undegassed arc magmas. The east seamount samples are characterized by higher Re and lower Yb/Re than the more MORB-like Lau Spreading Center lavas. The lack of correlation between Yb/Re and Fo of host olivine suggests that low Yb/Re is not due to magmatic differentiation. When the Lau Basin sample suite is plotted together with MORB data, Yb/Re is positively correlated with Ce/Pb and Nb/U, and negatively correlated with Ba/Nb, indicating that Re is much more mobile than Yb during dehydration of subducted slabs. Thus, Re enrichment in arc magmas is likely due to addition of Re via fluids released from subducted slabs; the recognition of high Re in arcs favors arguments for a slab origin of radiogenic ¹⁸⁷Os/¹⁸⁸Os components in arc rocks.  相似文献   

Trichlorofluoroethene: A reactive tracer for evaluating reductive dechlorination in large-diameter permeable columns     

Jennifer A. Field  Ralph L. Reed  Jonathan D. Istok  Lewis Semprini  Peter Bennett  Timothy E. Buscheck 《Ground Water Monitoring & Remediation》2005,25(2):68-77

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Nd, Sr and Os isotope systematics in young, fertile spinel peridotite xenoliths from northern Queensland, Australia: A unique view of depleted MORB mantle?     

M.R. Handler  V.C. Bennett 《Geochimica et cosmochimica acta》2005,69(24):5747-5763

Northeastern Queensland, a part of the Phanerozoic composite Tasman Fold Belt of eastern Australia, has a Paleozoic to Mesozoic history dominated by subduction zone processes. A suite of 13 peridotite xenoliths from the <3 Ma Atherton Tablelands Volcanic Province, predominantly from Mount Quincan, comprise fertile (1.8-3.4 wt.% Al₂O₃ and 38.7-41.9 wt.% MgO) spinel lherzolites free from secondary volatile-bearing phases and with only weak metasomatic enrichment of incompatible trace elements (Sm_N/Yb_N = 0.23-1.1; La_N/Yb_N = 0.11-4.9). The suite is isotopically heterogeneous, with measured Sr (⁸⁷Sr/⁸⁶Sr = 0.7027-07047), Nd (¹⁴³Nd/¹⁴⁴Nd = 0.51249-0.51362), and to a lesser extent, Os (¹⁸⁷Os/¹⁸⁸Os = 0.1228-0.1292) compositions broadly overlapping MORB source mantle (DMM) and extending to more depleted compositions, reflecting evolution in a time-integrated depleted reservoir. Major and rare earth element systematics are consistent with mantle that is residual after low to moderate degrees of melt extraction predominantly in the spinel facies, but with a few samples requiring partial melting at greater pressures in the garnet field or near the garnet-spinel transition. In contrast to most previously studied suites of continental lithospheric mantle samples, the incompatible trace element contents and Sr and Nd isotopic systematics of these samples suggest only minimal modification of the sampled lithosphere by metasomatic processes.Five of six Mount Quincan xenoliths preserving depleted middle to heavy REE patterns form a whole rock Sm-Nd isochron with an age of ∼275 Ma (ε_Ndi = +9), coincident with widespread granitoid emplacement in the overlying region. This isochron is interpreted to indicate the timing of partial melting of a DMM-like source. Xenoliths from other Atherton localities scatter about the isochron, suggesting that the sampled mantle represents addition of DMM mantle to the lithosphere in the Permian, when the region may have broadly been within a subduction zone setting. A sixth middle to heavy REE-depleted Mount Quincan xenolith has a distinct Nd and Os isotopic composition consistent either with an earlier, possibly Precambrian melt extraction event, or with Permian derivation from a mantle source with a less depleted (time-averaged lower Sm/Nd) Nd isotopic composition, but a more depleted (low Re/Os) Os isotopic composition.The range in measured whole rock Os isotopic compositions cannot solely be the result of time-integrated effects of variable melt extraction, especially considering the coherent Sm-Nd systematics of the suite. The Os heterogeneity more likely reflects either a heterogeneous ∼275 Ma DMM source that would have a present-day Os composition (¹⁸⁷Os/¹⁸⁸Os ∼ 0.1265-0.1287) overlapping both abyssal peridotites and chondrites, or significant and variable enrichment within the lithospheric mantle by secondary sulfides carrying radiogenic Os in a cryptic chalcophile enrichment event. Regardless of the origin of the Os isotopic variability, these data highlight the mantle Re-Os isotopic heterogeneity that may be present over small length scales where the lithophile Sm-Nd system may be relatively homogeneous.  相似文献   

Challenges in Norwegian coastal zone planning     

Roger G. Bennett 《GeoJournal》1996,39(2):153-165

The article identifies some of the challenges facing local structure planing of sea areas since the mid-1980s, and asks what has been achieved. This question concerns the quality of plans as tools for spatial ordering and development. On the basis of theories of communicative and strategic planning, a framework of assessment is evolved round two main concepts: the legitimacy and the flexibility of plans. These are supplemented with a conformance concept applicable to project planning. The article then examines specific planning problems and assesses processes and achievements in selected fish-farming communes on the coast of West and North Norway.  相似文献   

Global Warming and Water Management: Water Allocation and Project Evaluation     

Robert Mendelsohn  Lynne L. Bennett 《Climatic change》1997,37(1):271-290

This paper explores the sensitivity of the benefits of alternative water allocation schemes and of project evaluation to global warming. If global warming shifts the mean of annual water supplies, there could be large impacts on the expected values of alternative water allocation schemes. The first section of the paper explores how well alternative schemes (such as market mechanisms, prior rights, or percentage flows) perform if the distribution of flows changes. In a case study of the Colorado River, market mechanisms and flow guarantees result in smaller impacts than rules which allocate inefficient percentages of flows to heterogeneous users. The second part of the paper explores the effect of a gradually changing distribution of flows on project evaluations. Project evaluation is sensitive to predicted future changes in mean flows. Project evaluation is not sensitive to changes in the variance of future flows unless the variance increase is large and the benefit measure is highly curvilinear. Because basin-specific changes in runoff from global warming are currently uncertain and much delayed, most project analyses will be unaffected by global warming. The most important response by water managers to climate change may simply be to closely monitor runoff and incorporate flexible rules in order to adapt their behavior to observed changes.  相似文献   

The use of multiobjective analysis for comparing and evaluating environmental and economic goals in wetlands managements     

Prof.  Dr. J. Bennett  Prof.  Dr. I. Goulter 《GeoJournal》1989,18(2):213-220

The application of multi-objective analysis to wetlands management is examined in two stages. Initially generalized multi-objective techniques are reviewed briefly. The objectives and conflicts generally present in wetlands management are then discussed within the context of these techniques. Noting that conflicts among environmental and economic objectives may exist independently or in unison it is shown how multi-objective approaches can be used to resolve such conflicts to obtain best compromise solutions. Use of noninferior sets to define and intrepret the various objectives appears most suitable for such analyses. The proposed framework for use of multi-objective analysis corresponds to earlier work on how multi-objective techniques should be used in general public sector decision making.  相似文献   

Mixing and cycling of uranium,thorium and ²¹⁰Pb in Puget Sound sediments     

R. Carpenter  M.L. Peterson  J.T. Bennett  B.L.K. Somayajulu 《Geochimica et cosmochimica acta》1984,48(10):1949-1963

Activity profiles of excess ²³⁴Th, excess ²¹⁰Pb, ²³²Th, ²³⁰Th, ²³⁴U and ²³⁸U, and ^228/232Th ratios determined in eight box cores of sediment from six sites in central Puget Sound provide new insights into the dynamic nature of solid phase mixing in surface sediments, the exchange of ²²⁸Ra and other soluble species across the sediment-water interface, and the cycling of U, Th and ²¹⁰Pb in this coastal zone.Comparison of excess ²³⁴Th inventories in sediments with its production rate in the overlying water column indicates a mean residence time of at most 14 days for particles in the central Puget Sound water column.Surface sediment horizons with excess ²³⁴Th have no excess ²²⁸Th which might be used to ascertain sediment accumulation rates over the past decade. Instead, deficiencies of ²²⁸Th due to loss of soluble ²²⁸Ra from pore water to the overlying water persist to 20–30 cm, revealing that exchange of soluble chemicals between pore and overlying waters reaches these depths in the extensively bioturbated sediments of Puget Sound.Solid phase U isotope concentrations tend to increase by up to a factor of two with depth in sediments, as a result of dissolved U being biologically pumped down into sediments where it is partially removed when conditions become mildly reducing. ²³²Th and ²³⁰Th activities and ^230/232Th ratios are constant with depth in sediments, indicating constant detrital phase compositions and essentially no authigenic ²³⁰Th. Steady state ²¹⁰Pb depositional activities in and fluxes to Puget Sound sediments average only about onehalf those for sediments of the open Washington coast north of the Columbia River mouth, primarily because of a much lower supply of dissolved ²¹⁰Pb in sea waters adverting into Puget Sound.Excess ²³⁴Th profiles in sediments reveal much more detail about the depth dependency, dynamic nature and recent history of solid phase mixing processes than excess ²¹⁰Pb profiles. At least six of eight ²³⁴Th profiles show that mixing within the ²¹⁰Pb-defined surface mixed layer is depth dependent. In three profiles, ²³⁴Th-derived mixing rates are fastest several centimeters below the sediment-water interface, indicating greater macro-benthic activity at these depths. Depth dependent mixing coefficients derived from the best fit of a four layer, advection-diffusion-decay model to the ²³⁴Th data are consistent with ²¹⁰Pb profiles determined for the same sediments, strongly suggesting that ²³⁴Th and ²¹⁰Pb are mixed equivalently and in a multilayered manner.  相似文献   

Facies architecture within a regional glaciolacustrine basin: Copper River, Alaska     

Matthew R. Bennett  David Huddart  Geoffrey S.P. Thomas 《Quaternary Science Reviews》2002,21(20-22)

This paper defines the principal architectural elements present within the Pleistocene, glaciolacustrine basin-fill of the Copper River Basin in Alaska. The Copper River drains an intermontane basin via a single deeply incised trench through the Chugach Mountains to the Gulf of Alaska. This trench was blocked by ice during the last glacial cycle and a large ice-dammed lake, referred to as Lake Atna, filled much of the Copper Basin. Facies analysis within the basin floor allows a series of associations to be defined consistent with the basinward transport of sediment deposited along calving ice margins and at the basin edge. Basinward transport involves a continuum of gravity driven processes, including slumping, cohesive debris flow, hyperconcentrated/concentrated density flows, and turbidity currents. This basinward transport results in the deposition of a series of subaqueous fans, of which two main types are recognised. (1) Large, stratified, basin floor fans, which extend over at least 5 km and are exposed in the basin centre. These fans are composed of multiple lobes, incised by large mega-channels, giving fan architectures that are dominated by horizontal strata and large, cross-cutting channel-fills. Individual lobes and channel-fills consist of combinations of: diamict derived from iceberg rainout and the ice-marginal release of subglacial sediment; multiple units of fining upward gravels which grade vertically into parallel laminated and rippled fine sands and silts, deposited by a range of density flows and currents derived from the subaqueous discharge of meltwater; and rhythmites grading vertically into diamicts deposited from a range of sediment-density flows re-mobilising sediment deposited by either iceberg rainout or the ice-marginal release of sediment. (2) Small, complex, proximal fans, which extend over less than 2 km, and are exposed in the southern part of the basin. These fans are composed of coalescing and prograding lobes of diamict and gravel deposited both directly by subaqueous meltwater and from sediment-density flows. These lobes are cross-cut by a range of sand and gravel-filled troughs and channels cut by subaqueous outwash, and either overlie or are overlain by horizontal sheets of gravel and diamict deposited from a range of sediment-density flows. The fans are, therefore, characterised by a complex, and laterally variable facies, architecture. Water depth, proglacial topography, stability of meltwater portals and sediment supply may all be important in determining the type of subaqueous fan present at any one location. We suggest that the Copper River basin-fill is dominated by packages of sediment containing multiple subaqueous fans with individual fans separated by units of diamict. Each sediment package is in turn separated from the next by a palaeo-landsurface shaped by interstadial/interglacial fluvial processes and by volcanic debris flows.  相似文献   

A provisional map of forest types for the British Isles 5000 years ago     

Keith David Bennett 《第四纪科学杂志》1989,4(2):141-144

The distributions of seven woodland types, plus unforested areas, are mapped for the British Isles at 5000 BP. The map was compiled using data of modern soil distribution, present-day ecological preferences of the tree taxa present, and the pollen record.  相似文献