Identification of some diterpenoid hydrocarbons in petroleum

19-Norisopimarane and isopimarane have been synthesized from isopimara-9(11), 15-diene-3β, 19-diol. Analysis of the alkane fractions of an Australian crude oil by GC-MS showed the presence of nine diterpenoid hydrocarbons (diterpanes), of which one was bicyclic two were tricyclic and six were tetracyclic.19-Norisopimarane and isopimarane were identified by comparison of their mass spectra and GC retention times with those of the synthetic standards. ent-Beyerane, 16a(H)-phyllocladane, 16)β(H)-phyllocladane, ent-16α(H)-kaurane and labdane were also identified by comparison with authentic reference compounds. The remaining two compounds were tentatively identified as rimuane and as a 17-nortetracyclic diterpane on the basis of mass spectral evidence. The diterpanes are probably derived from conifer resins.     

Schwertmannite stability in acidified coastal environments

A combination of analytical and field measurements has been used to probe the speciation and cycling of iron in coastal lowland acid sulfate soils. Iron K-edge EXAFS spectroscopy demonstrated that schwertmannite dominated (43-77%) secondary iron mineralization throughout the oxidized and acidified soil profile, while pyrite and illite were the major iron-bearing minerals in the reduced potential acid sulfate soil layers. Analyses of contemporary precipitates from shallow acid sulfate soil groundwaters indicated that 2-line ferrihydrite, in addition to schwertmannite, is presently controlling secondary Fe(III) mineralization. Although aqueous pH values and concentrations of Fe(II) were seasonally high, no evidence was obtained for the Fe(II)-catalyzed crystallization of either mineral to goethite. The results of this study indicate that: (a) schwertmannite is likely to persist in coastal lowland acid sulfate soils on a much longer time-scale than predicted by laboratory experiments; (b) this mineral is less reactive in these types of soils due to surface-site coverage by components such as silicate and possibly, to a lesser extent, natural organic matter and phosphate and; (c) active water table management to promote oxic/anoxic cycles around the Fe(II)-Fe(III) redox couple, or reflooding of these soils, will be ineffective in promoting the Fe(II)-catalyzed transformation of either schwertmannite or 2-line ferrihydrite to crystalline iron oxyhydroxides.     

Habitat use by small mammals in coastal marshes of Southwestern Louisiana

A short-term study based on snap-trap capture rates of small mammals in the marsh and levee system in southwestern Louisiana was conducted in the winter-spring period. Marsh rice rats (Oryzomys palustris) dominated marsh habitats and rice rats and fulvous harvest mice (Reithrodontomys fulvescens) were co-dominants on levees. Least shrews (Cryptotis parva) and house mice (Mus musculus) were also taken. Although rice rat capture rate in marshes was twice that from levees, the difference was not significant (p=0.1428). When found on levees, rice rats preferred portions of levees adjacent to marshes and canals (p<0.0001). We found few differences in rice rat capture rates from marsh and levee habitats, although capture rates from fresh marsh and adjacent levees were select levee ridges over the marsh and canal edges (0.1≥p≥0.05). The abundance of harvest mice on levees adjacent to intermediate marshes exceeded all other levee habitats. For reasons as yet unexplained, intermediate marshes and adjacent levees had the highest small mammal abundance and species richness. Conversely, fresh marshes and their adjacent levees had the lowest abundance and variety of small mammals.     

Classification of clastic coastal depositional environments

This paper proposes a new classification for clastic coastal environments which includes the full range of major depositional settings including deltas, strand plains, tidal flats, estuaries and lagoons. This classification includes both morphologic and evolutionary components and is based on dominant coastal processes. It has the potential to predict responses in geomorphology, facies and stratigraphy. The significance of this classification is its evolutionary capability, and its inclusion of all major clastic coastal depositional environments, making it more comprehensive than previous classifications.

We employ a ternary process classification with two axes. The first (horizontal axis) is defined as the relative power of wave versus tidal processes. The second (vertical) axis represents relative fluvial power (increasing upward). A ternary diagram defined by these axes can be used to illustrate the genetic process-response relationships between major coastal environments. The evolutionary classification combines the concept of two sediment sources (river and marine) with a relative sea-level parameter to classify embayed as well as linear and elongate/lobate shorelines. This approach identifies the evolutionary relationships between coastal sedimentary environments.

The new ternary approach to process classification can be applied to estuaries and lagoons to define wave and tide end-member facies models, each consisting of a tripartite facies zonation. The evolutionary classification is compatible with sequence stratigraphy because sediment supply and relative sea level are included, and serves as a starting point for more refined coastal stratigraphic analyses.     

Dinosterane and other steroidal hydrocarbons of dinoflagellate origin in sediments and petroleum

The steroidal alkanes of a selection of sediments and oils have been examined by GC-MS with multiple metastable reaction monitoring. Specific 4-methyl sterane isomers have been identified by comparison with isomers synthesized from sterols isolated from dinoflagellates. An immature marine oil shale and two mature marine oils of Triassic to early Cretaceous age contained high concentrations of C₃₀ steranes comprising desmethyl, 24-ethyl-4α-methylcholestane and 4α,23,24-trimethylcholestane (dinosterane) isomers. An immature non-marine oil shale and two non-marine oils of Cretaceous to Eocene age contained stereoisomers of 24-ethyl-4α-methylcholestane as the dominant C₃₀ steranes. Reaction monitoring analyses in GC-MS are particularly suited to unravelling complex distributions of homologous and stereoisomeric steroids encountered in oils and their source rocks.     

Classification and thermal history of petroleum based on light hydrocarbons

Classifications of oils and kerogens are described. Two indices are employed, termed the Heptane and IsoheptaneValues, based on analyses of gasoline-range hydrocarbons. The indices assess degree of paraffinicity. and allow the definition of four types of oil: normal, mature, supermature, and biodegraded. The values of these indices measured in sediment extracts are a function of maximum attained temperature and of kerogen type. Aliphatic and aromatic kerogens are definable. Only the extracts of sediments bearing aliphatic kerogens having a specific thermal history are identical to the normal oils which form the largest group (41%) in the sample set. This group was evidently generated at subsurface temperatures of the order of 138°–149°C, (280°–300°F) defined under specific conditions of burial history. It is suggested that all other petroleums are transformation products of normal oils.     

Effect of hydrologic management on marsh surface sediment deposition in coastal Louisiana

High rates of coastal land loss in Louisiana have prompted efforts to maintain or restore coastal wetland habitats, and structural management of marsh hydrology is one of a number of approaches that has been adopted. The aim of this study was to determine the effect of hydrologic management measures on marsh-surface sediment deposition in the Mississippi deltaic plain. Four impoundments, ranging in size from 50 ha to 177 ha and similarly sized control sites were included in the study. At each site, marsh-surface sediment traps were collected approximately biweekly for 3.5 yr to measure changes in sediment deposition. There was no significant difference in sediment deposition between any of the impoundment and control sites during the premanagement period. The results show no significant difference in marsh-surface sediment deposition between management year 1992–1993 and management year 1994–1995, but management year 1993–1994 had significantly lower sediment deposition than either the first or the last year of the study. Management year 1992–1993 showed the highest sediment deposition when it was assessed across all basins, areas, and sites, and this high rate of deposition is accounted for by the impact of Hurricane Andrew. For all management years there were significant differences between impoundment and control sites, with control sites showing higher rates of marsh surface sediment deposition than impoundments. No clear pattern was identified concerning the influence of various types of hydrologic management on rates of sediment deposition. This reduction in sediment deposition indicated that the areas under management in this study are receiving insufficient inorganic sediment deposition to keep pace with sea-level rise.     

Decomposition of saltmeadow cordgrass (Spartina patens) in Louisiana coastal marshes

In Louisiana, plant production rates and associated decomposition rates may be important in offsetting high rates of land loss and subsidence in organic marsh soils. Decomposition ofSpartina patens shoot and leaf material was studied by using litter bags in mesohaline marshes in the Barataria and Terrebonne basins of coastal Louisiana.Spartina patens decomposed very slowly with an average decay constant of 0.0007, and approximately 50% of the material remained after 2 years in the field. Material at the Barataria site decomposed faster than did Terrebonne material with trend differences apparent during the first 150 days. This difference might be explained by the higher content of phosphorus in the Barataria material or a flooding period experienced by the Barataria bags during their first 10 days of deployment. Nitrogen and carbon content of the plant material studied did not differ between the two basins. We detected no consistent significant differences in decomposition above, at, or below sediment/water level. BecauseS. patens is the dominant plant in these marshes, and because it is so slow to decompose, we believe thatS. patens shoots are an important addition to vertical accretion and, therefore, marsh elevation.     

Potential impacts of long-term subsidence on the wetlands and evacuation routes in coastal Louisiana

A steady-state subsidence forecast model was developed as a proof of concept to estimate changes in surface elevations of the wetlands and evacuation routes across coastal Louisiana for the years 2015, 2025, 2050, and 2100. Subsidence estimates were derived from an empirical study published by the National Geodetic Survey. Forecasted vertical change was subtracted from current surface elevations. Land and evacuation routes estimated to have surfaces at or below 0 m in elevation, NAVD88, were quantified and classified as vulnerable to inundation hazards. The extent of the coastal zone susceptible to hurricane induced storm surge was also evaluated relative to surge models published by the National Weather Service. The results indicate spatially heterogeneous rates of subsidence that are forecasted to consume nearly 50 % of the existing coastal margin wetlands by 2100. The most significant rate increases are anticipated between 2015 and 2050. Relative to the impact on evacuation routes, subsidence occurring between the 2015 and 2025 forecast years expanded at slower rates when compared to the latter half of the century. Subsidence adjusted storm surge forecasts reveal similar patterns. The methods employed and findings produced demonstrate forecasting capabilities that provide emergency managers and transportation engineers with resources applicable to evacuation modeling, hazard mitigation, environmental sustainability research, costal restoration efforts, and more.     

Urban and suburban storm water runoff as a source of polycyclic aromatic hydrocarbons (PAHs) to Massachusetts estuarine and coastal environments

Urban and suburban storm water runoff from ten locations in eastern Massachusetts was analyzed for 39 polycyclic aromatic hydrocarbons (PAHs) compounds. Similar profiles in PAH composition were observed for groups of samples and appear to reflect land use. The largest group includes, urban storm water from areas with a mix of industrial, commercial, and residential use. Fluoranthene, phenanthrene, pyrene, chrysene, and benzo (b) fluoranthene were the predominant compounds in this group, but lighter molecular weight PAHs were also present. Sources of PAHs to storm water include a combination of petroleum and combustion. The profile of PAH compounds in local atmospheric deposition was similar to urban storm water, but differed in several of the predominant compounds. PAHs in storm water could increase the levels of these compounds in nearshore sediments and may be the most important source of high molecular weight PAHs to these environments.     

Records of nutrient-enhanced coastal ocean productivity in sediments from the Louisiana continental shelf

Shelf sediments from near the mouth of the Mississippi River were collected and analyzed to examine whether records of the consequences of anthropogenic nutrient loading are preserved. Cores representing approximately 100 yr of accumulation have increasing concentrations of organic matter over this period, indicating increased accumulation of organic carbon, rapid early diagenesis, or a combination of these processes. Stable carbon isotopes and organic tracers show that virtually all of this increase is of marine origin. Evidence from two cores near the river mouth, one within the region of chronic seasonal hypoxia and one nearby but outside the hypoxic region, indicate that changes consistent with increased productivity began by approximately the mid-1950s when the inorganic carbon in benthic forams rapidly became isotopically lighter at both stations. Beginning in the mid-1960s, the accumulation of organic matter, organic δ¹³C, and δ¹⁵N all show large changes in a direction consistent with increased productivity. This last period coincides with a doubling of the load of nutrients from the Mississippi River, which levelled off in the mid-1980s. These data support the hypothesis that anthropogenic nutrient loading has had a significant impact on the Louisiana shelf.     

Distribution of total petroleum hydrocarbons in Dezful aquifer,Southwest of Iran

Determination of total petroleum hydrocarbon distribution (TPH) in groundwater of Dezful aquifer was the main purpose of this study. The study area, which is located between latitudes 32°00′ and 32°35′?N and longitudes 48°10′ and 49°35′?E, covers about 1,920 km² in the north of Khuzestan Province, Iran. Hydrocarbon pollutants in the area were being released into the aquifer, from a variety of sources. An oil pipe crash accident, which occurred on 19 Feb. 2009 in the vicinity of the northern part of the study area, released about 6,000 barrels of crude oil to the Karkhe River. Other possible sources of TPH in the region are asphalt factories, gas stations, and the Sabzab oil pump station. Since the main source of drinking water in the Dezful area is groundwater reservoirs, this study would be very crucial, especially when there is considerable agricultural activity in the area as well. In order to determine the presence of TPH and heavy metals in the groundwater, samples were taken from wells with different usage within two periods, i.e., in Nov. 2008 and May 2009. The second sampling operation was carried out to determine the effect of the accident in the water resources. In situ groundwater parameter measurements including pH, dissolved oxygen, temperature, and electrical conductivity were also carried out in the field. Based on the results, there are four zones in the study area which were contaminated with TPH from different origins: (1) southeast of Dezful City, which was contaminated by Shokati gas station; (2) southeast of Shush City, which was contaminated by an asphalt factory; (3) southwest of Dezful City, which was contaminated by Sabzab oil pump station; and (4) the shores of Karkhe River which were contaminated due to the pipeline crash accident. This could be a serious threat to the environment and human health because TPH concentration was higher than the EPA standard in the study area. Heavy metals were not distributed in a uniform pattern in the aquifer. The concentrations were lower than the contamination level based on the EPA drinking standard, and there was no meaningful relation between concentrations of TPH and the heavy metals. It was recommended that a monitoring network should be designed to monitor oil contaminants in the ground and surface water monthly because of importance of the water resources and presence of potential oil contaminant sources.     

成油环境中的流体包裹体：分析步骤与PTX重建

摘要石油盆地内的古流体以流体包裹体的形式保存在成岩矿物中,它们代表了初始石油或气相的组成并记录了流体捕获时的温度和压力条件。在储集层中卤水通常以不混溶相的形式与石油共存。一般利用单个包裹体分析法对水溶液和石油包裹体进行研究,利用显微测温法来确定相转变的温度,利用拉曼光谱定量来分析水溶液包裹体中溶解甲烷的含量,石油包裹体中CH4和CO2的含量可以利用傅立叶变换红外光谱分析来估算,通过共聚焦扫描激光显微镜来重建石油包裹体的体积。利用Duan和Peng-Robinson方程可进行热力学模拟,并分别应用于水溶液和石油包裹体体系。两类流体体系等容线的交点可用来确定流体捕获时的实际温度和压力条件,从而利用流体压力对具有不同地球动力学背景的源区流体动力学演化进行重建。     

Hydrogen isotopic fractionation of petroleum hydrocarbons during vaporization: implications for assessing artificial and natural remediation of petroleum contamination

Compound-specific H isotope analysis has been used to monitor bioremediation of petroleum hydrocarbons. However, the success of this approach requires a full evaluation of the isotopic effects resulting from evaporation, because light petroleum hydrocarbons undergo both biodegradation and evaporation under natural conditions. The authors determined the H isotope fractionation of common volatile petroleum hydrocarbons, including the C₁₀–C₁₄ n-alkanes, MTBE (tert-butyl methyl ether), and BTEX (benzene, toluene, ethylbenzene, p-xylene and o-xylene) during progressive vaporization under simulated experimental conditions. A decrease in δD values for n-alkanes of up to 33.3‰ and up to 44.5‰ for BTEX compounds when 99% of these substances had evaporated was observed. The results also show that H isotope fractionation increases with n-alkane chain length. Such fractionation patterns are interpreted in terms of competition between the decreased intermolecular binding energy in D-enriched species, and the isotope effect due to the mass difference. In contrast to hydrocarbons, methanol and ethanol show H isotopic enrichment during vaporization, indicating that H-bonding, when present in organic molecules, plays a controlling role on the vapor pressure of different isotope species.     

Depositional environments of coastal sediments of Calangute,Goa

The grain-size statistics and environmental conditions of deposition of the beach and dune sediments from the Calangute region, Goa, have been studied. The results of Student's t test and bivariate plots reveal that there exist distinct differences in grain-size parameters of the sediments from different environments and that these differences are highly significant. The study shows that the variations in mean grain size (Mz), graphic standard deviation (O₁), graphic skewness (Sk₁), simple sorting measure (So_s) and simple skewness measure (O_s) are significant in identifying the sediments from different environments. Further, the study reveals the usefulness of grain-size parameters not only in differentiating beach and dune sediments, but also in delineating the beach into foreshore and backshore. The differences in grain-size characteristics of the sediments between the environments reflect the transport, erosional and depositional mechanisms (active hydrodynamic processes in the beach foreshore and aerodynamic processes in the backshore and dune environments) prevailing in the area of study.     

Evaluation of the use of legumes for biodegradation of petroleum hydrocarbons in soil

The aim of this research was to evaluate the potential of six legumes: Medicago sativa L., Glycine max, Arachis hypogea, Lablab purpureus, Pheseolus vulgaris and Cajanus cajan to restore within a short period of time soil contaminated with 3% crude oil. The legumes in five replications were grown in crude oil-contaminated and crude oil-uncontaminated soil in a completely randomized design. Plants were assessed for seedling emergence, plant height and leaf number. GC–MS was used to analyze the residual crude oil from the rhizosphere of the legumes. Plant growth parameters were reduced significantly (P < 0.05) for legumes in contaminated soil compared to their controls. In the 4th week after planting (WAP), shoot height increased across the species up to the 8th WAP. However, in the 12 WAP no significant increase in the shoot of all species was observed. Two WAP legumes planted in contaminated soil had significantly (P < 0.05) higher leaf number than these planted in uncontaminated soil with the exception of M. sativa. In the 4th WAP, only A. hypogea and P. vulgaris had increased leaf number, while in the 6th WAP, only L. purpureus had increased leaf number and survived up to the 12th WAP while most of the legumes species died. Chromatographic profiles indicated 100% degradation of the oil fractions in C. cajan and L. purpureus after 90 days. For other legumes however, greater losses of crude oil fractions C₁–C₁₀ and C₁₀–C₂₀ were indicated in rhizosphere soil of P. vulgaris and G. max, respectively. The most effective removal (93.66%) of C₂₁–C₃₀ components was observed in G. max-planted soil even though vegetation was not established. The legumes especially C. cajan, L. purpureus and A. hypogea are promising candidates for phytoremediation of petroleum hydrocarbon-impacted soil.     

Experimental study of the reaction of methane with petroleum hydrocarbons in geological conditions

In order to assess the possible role of methane in petroleum formation, we studied the reaction of methane with liquid hydrocarbons representing the three main classes of compounds dominant in crude oil. The experimental reaction conditions simulated those of a geological setting for petroleum formations, at 1000 atm and 150–250°C in the presence of montmorillonite, a natural clay catalyst. Since we expected very slow reaction rates and thus low yields, we used ¹⁴C labeled methane to trace the reaction products. We report here the detection of ethylbenzene and ethyltoluene formed by the interaction of methane with benzene and toluene, respectively. Instead of methylation of benzene, predominantly C₂ addition occurred, although very small amounts of products corresponding to C₁ addition were also detected. We propose that catalytic dissociation of methane occurred, forming ethylene which participated in a Friedel-Crafts type alkylation process of the aromatic ring on the catalyst surface. In addition to ring alkylation, side reactions such as polymerization of unsaturates (ethylene, acetylene) appeared to have occurred on the catalyst surface. The nature of these polymers is yet to be determined.