Organic geochemistry of Cuban oils—I. The northern geological province

The isoprenoid, hopanoid and steroid compositions of 15 oils from the most productive oil fields in Cuba were studied to determine source-rock depositional environments and organic matter sources. The oils, which are from the northern geological province of Cuba and can be defined by the position with respect to the overthrust belt, can be grouped into two families: those from the Remedios (1) and those from the Placetas (2) tectonostratigraphic units.Remedios oils contain 17α(H)-diahopane, high relative amounts of 18α(H)-22,29,30-trisnorneohopane and diasteranes, which is indicative of generation from clay-rich source rocks. The crude oils of the Placetas Unit exhibit a sterane/hopane composition consistent with a carbonate origin. Nevertheless, these polycyclic hydrocarbons exhibit significant changes in composition, indicating that several organic matter sources, e.g. a carbonate/evaporitic origin of Varadero and Varadero Sur oils, have contributed to the oils from this Unit. The Remedios oils are more mature [evaluated from the and sterane indices] than the Placetas oils.A wide range of biodegradation levels are encountered in these oils (from 0 to 7–8 using the scale derived by Volkman et al. (1983). The high relative abundance of 25-norhopanes is a distinctive feature of Remedios oils. The presence of these compounds in lightly biodegraded or nondegraded oils corresponds to a mixing of paleobiodegraded oil with more recently sourced nondegraded oil in the reservoir. The most biodegraded oil, Cantel, exhibits and sterane ratios, and hopane ratios that have been altered by microbial attack.     

Hydrocarbons in Washington coastal sediments

The sources and distributions of polycyclic aromatic hydrocarbons (PAH) and aliphatic hydrocarbons are characterized in seventeen sediments from a highly river-influenced sedimentary environment off the southwestern coast of Washington. The major hydrocarbons are land-derived, introduced as preformed compounds and display long-term stability in sediment cores. A series of PAH of anthropogenic origin and two naturally derived compounds, retene and perylene, dominate the PAH composition in these sediments. Plantwax n-alkanes are the major aliphatic hydrocarbon constituents. Aliphatic hydrocarbons of marine origin, pristane and a series of four acyclic, multibranched C₂₅ polyolefins, are also observed in many sediments. The concentrations of these marine-derived hydrocarbons decrease to negligible levels rapidly with sediment depth from the sea-sediment interface, suggesting degradation.In general, the major land-derived hydrocarbons are concentrated in the midshelf silt deposit which extends northwestward along the continental shelf from the Columbia River mouth. A quantitatively more minor, natural series of phenanthrene homologs, also of terrestrial origin, is preferentially advected further offshore and deposited in continental slope sediments. These distributions are consistent with recognized particle associations for these compounds and sediment dispersal processes in this coastal environment. Sediment core records suggest the present pattern of dispersal has persisted for at least the past century and possibly since the Late Pleistocene.     

厦门西海域表层水中PAHs污染与PAHs降解菌分布的关系

在厦门西海域设置6个站位，于2001年7月和10月两个航次对各站位表层水中多环芳烃(polycyclic aromatic hydrocarbons，PAHs)的含量及几种常见PAHs的降解菌的数量进行调查，结果表明：表层水中PAHs的含量很不稳定，存在明显的时间变化。在7月的调查中，表层水中能检测到的PAHs以2—3环的为主，而在10月以46环的为主。低分子量的PAHs——芴和菲的含量与其降解菌的数量之间具有明显的正相关，而高分子量的PAHs—荧蒽和芘的含量与其降解菌的数量之间没有表现出相关性。     

Sources and Transport of Particulate Hydrocarbons in the Meso-tidal Changjiang Estuary

n-Alkanes and polyaromatic hydrocarbons (PAHs) were analysed on suspended particles from surface waters of the Changjiang Estuary to assess the sources and fate of river-borne material in a meso-tidal riverine system. The n -alkane and PAH assemblages indicated prevailing terrestrial and anthropogenic inputs. Measurements performed at several stations within the estuary showed lower concentrations in the North than in the South Channel. These observations were in agreement with the dynamics and flow pattern of the Changjiang in this part of the estuary. Concentrations measured at a tidal series station over two tidal cycles exhibited a significant increase in flooding of more saline waters. Total suspended particles were also higher, reaching their maximum value (1·9 g l^-1) at high tide during the first flood. These findings were attributed to the landwards transport of the turbidity maximum zone from the outer estuary, as the Taiwan Warm Current funnels into the Changjiang River mouth. Saltier and less turbid waters with a more pronounced marine character could reach the tidal series site at the final stage of the second flood. During the ebb, suspended n-alkane and PAH concentrations were lower but their compositional features remained similar to those during the flood. A high total suspended particle concentration was observed during the ebb, presumably due to the Huang Pu waters flushing. The n -alkane and PAH content of the particles during such an event pointed out stronger contamination of the waters after crossing the highly populated and industrialized area of Shanghai. Flux calculations based on current meter data indicated significant differences between flood and ebb transports.     

Retrospective analysis: bile hydrocarbons and histopathology of demersal rockfish in Prince William Sound,Alaska, after the Exxon Valdez oil spill

Demersal rockfish are the only fish species that have been found dead in significant numbers after major oil spills, but the link between oil exposure and effect has not been well established. After the 1989 Exxon Valdez oil spill in Prince William Sound, Alaska, several species of rockfish (Sebastes spp.) from oiled and reference sites were analyzed for hydrocarbon metabolites in bile (1989-1991) and for microscopic lesions (1990 and 1991). Biliary hydrocarbons consistent with exposure to Exxon Valdez oil were elevated in 1989, but not in 1990 or 1991. Significant microscopic findings included pigmented macrophage aggregates and hepatic megalocytosis, fibrosis, and lipid accumulation. Site differences in microscopic findings were significant with respect to previous oil exposure in 1991 (P=0.038), but not in 1990. However, differences in microscopic findings were highly significant with respect to age and species in both years (P<0.001). We conclude that demersal rockfish were exposed to Exxon Valdez oil in 1989, but differences in microscopic changes in 1990 and 1991 were related more to age and species differences than to previous oil exposure.     

The North Cape oil spill: hydrocarbons in Rhode Island coastal waters and Point Judith Pond.

On 19 January 1996, the North Cape oil barge ran aground near Moonstone Beach, RI, and spilled over 2700 metric tons of No. 2 fuel oil during a severe winter storm. High winds and rough seas drove the oil into the water column, and the oil spread throughout Block Island Sound and into several coastal salt ponds. Over 50 water samples were collected from Point Judith Pond (PJP) and the southern coast of Rhode Island for four months after the spill and analyzed for polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPHs). These analyses revealed that at least 60 km2 of coastal waters were impacted from the spill. Maximum concentrations of sigmaPAHs and TPHs were 115 and 3940 microg l(-1), respectively. The percentage of sigmaPAHs relative to the TPHs for all samples varied from 0.2 to 43%, showing that there was no clear relationship between sigmaPAHs and TPHs for the whole dataset and likely resulting from spatial and temporal partitioning over the course of the spill. However, within the dataset, there were stronger correlations for distinct samples collected at similar locations and times. In PJP, water column concentrations of individual PAHs decreased at rates of 0.08-0.24 day(-1) and lower-molecular weight PAHs were removed faster than higher-molecular weight PAHs.     

Hydrocarbon evolution for a north-south section of the South Caspian Basin

A 150 km length, 6-second deep, seismic line across the west central and north parts of the South Caspian Basin was used to construct quantitative dynamical, thermal and hydrocarbon evolution patterns. The depth of the west part of the 2-D section of the South Caspian Basin is almost 30 km. The computer program GEOPETII was used to provide quantitative evolution models. The procedure provided an opportunity to investigate the development dynamics of: excess fluid pressure, porosity retention, rock fracturing, compaction, heat transfer, maturity, generation pressure, kinetic hydrocarbon generation, migration and accumulation, together with solubility effects on hydrocarbon transport. The results suggest that: (i) Temperature is 350–400°C in the deepest part of the section at a depth of 26–29 km; (ii) The highest values of excess pressure nearly twice hydrostatic fluid pressure are in Jurassic and Cretaceous formations in the west part of the section, which has now subsided to a depth of about 20–27 km; (iii) Major oil and gas generation began in the last 10-5 MYBP, the migration in free-phase and in water solution occurring dominantly in the last few million years; (iv) Trapping of hydrocarbons took place mainly, but not exclusively, in the 3–9 km depth interval in the sands of the Productive Series of the Pilocene, embedded in a shale sequence; (v) Oil and gas filling of the shallow reservoirs by oil and gas is on-going today, indicating an extremely high productivity for any reservoir found in the offshore area; (vi) There is overlap with depth of oil and gas reservoirs, and the total amount of hydrocarbons estimated to be trapped is considerable; (vii) The high overpressure expected makes for a drilling hazard, but one which it is worthwhile to overcome if the anticipated oil and gas accumulations are encountered.     

Restoration of oiled mussel beds in Prince William Sound, Alaska

Natural loss of hydrocarbons was often low from mussel (Mytilus trossulus) beds (which were typically not cleaned after the Exxon Valdez oil spill), thus this habitat remained a long-term source of oil. Consequently, experimental restoration of nine contaminated beds was attempted in 1994; mussels were removed, contaminated surface sediment was replaced (33 metric tons), and original mussels were returned. Hydrocarbon concentrations and mussel populations were monitored for 5 years thereafter. Post-restoration mussel population fluctuations were indistinguishable from regional changes. Increased short-term oil loss was apparent, but long-term (5 year) improvement was equivocal and difficult to distinguish from natural losses. By 1999, oil concentrations in mussels were typically at baseline levels in restored and oiled reference beds; concentrations in replaced sediment were elevated in one third of restored beds, indicating recontamination from underlying or surrounding sediment. Our results suggest mussel relocation is feasible but suggest oil might more effectively be removed from sediment mechanically or chemically than manually.     

Thermogenic organic matter dissolved in the abyssal ocean

Formation and decay of thermogenic organic matter are important processes in the geological carbon cycle, but little is known about the fate of combustion-derived and petrogenic compounds in the ocean. We explored the molecular structure of marine dissolved organic matter (DOM) for thermogenic signatures in different water masses of the Southern Ocean. Ultrahigh-resolution mass spectrometry via the Fourier transform-ion cyclotron resonance technique (FT-ICR-MS) revealed the presence of polyaromatic hydrocarbons (PAHs) dissolved in the abyssal ocean. More than 200 different PAHs were discerned, most of them consisting of seven condensed rings with varying numbers of carboxyl, hydroxyl, and aliphatic functional groups. These unambiguously thermogenic compounds were homogenously distributed in the deep sea, but depleted at the sea surface. Based on the structural information alone, petrogenic and pyrogenic compounds cannot be distinguished. Surface depletion of the PAHs and first estimates for their turnover rate (> 1.2 · 10¹² mol C per year) point toward a primarily petrogenic source, possibly deep-sea hydrothermal vents, which is thus far speculative because the fluxes of combustion-derived and petrogenic matter to the ocean are not well constrained. We estimate that > 2.4% of DOM are thermogenic compounds, and their global inventory in the oceans is > 1.4 · 10¹⁵ mol C, significantly impacting global biogeochemical cycles.     

A computational model of the digestive gland epithelial cell of marine mussels and its simulated responses to oil-derived aromatic hydrocarbons

This paper describes a computational model of digestive gland epithelial cells (digestive cells) of marine mussels. These cells are the major environmental interface for uptake of contaminants, particularly those associated with natural particulates that are filtered from seawater by mussels. Digestive cells show well characterised reactions to exposure to lipophilic xenobiotics, such as oil-derived aromatic hydrocarbons (AHs), which accumulate in these cells with minimal biotransformation. The simulation model is based on processes associated with the flux of carbon through the cell. Physiological parameters such as fluctuating food concentration, cell volume, respiration, secretion/excretion, storage of glycogen and lipid, protein/organelle turnover (autophagy/resynthesis) and export of carbon to other tissues of the mussel are all included in the model. The major response to AHs is induction of increased autophagy in these cells. Simulations indicate that the reactions to AHs and food deprivation correspond well with responses measured in vivo.