Distribution Of Hydrocarbons In Sediments Research Articles

Distribution of petroleum hydrocarbons in sediments from Dianchi Lake, China

Thirteen Dianchi Lake sediments were analyzed for parent and alkylated polycyclic aromatic hydrocarbons (PAHs), hopanes, and steranes by gas chromatography-mass spectrometry. Total PAH concentrations in the sediment ranged from 590 to 23,250 ng/g. The alkylated phenanthrene/phenanthrene and alkylated pyrene/pyrene ratios displayed a strong correlation with the total PAH concentrations, suggesting that the sediments were heavily impacted by petrogenic PAHs. This finding was consistent with the ratios and compositional features of hopanes and steranes, and confirmed the presence of mature petroleum in the sediments. The sedimentary total organic carbon contents were correlated with the organic pollutant concentrations (R2 = 0.81–0.88), suggesting that the distribution was controlled by an extensive point source and/or transport and sedimentation processes. Principal component analysis results indicated two major sources of inputs to the aquatic environment in the area: (1) discharge from the Daguanhe River, and (2) leakage of oil from motor boats in nearby harbors. A gradient of increasing parent PAH (relative to alkylated PAHs) concentrations toward the lower section of Dianchi Lake, as compared to those in the upper section, reflected the resistance of the parent PAHs to degradation and bioavailability during pollutant diffusion. The uniform composition between sedimentary steranes and hopanes was explained not by one diffuse single source but, rather, by the lack of change in the composition of oil residues after natural transport and sedimentation processes.

Hydrocarbon Distribution in Sediments from the Southeast Coastal Region of Bangladesh

Hydrocarbon Distribution in Sediments from the Southeast Coastal Region of Bangladesh

Polycyclic aromatic hydrocarbon distributions in sediments from the Mar Piccolo, Ionian Sea, Italy.

Polycyclic aromatic hydrocarbon distributions in sediments from the Mar Piccolo, Ionian Sea, Italy.

Hydrocarbon distributions in sediments of the open area of the Arabian Gulf following the 1991 Gulf War oil spill

Surface sediments collected from the open area of the Arabian Gulf were analysed for total petroleum hydrocarbons and specific aliphatic hydrocarbon components in order to provide information on the extent of oil contamination and the degree of weathering of the spilled oil following the Gulf War. The concentration of petroleum hydrocarbons in the sediments ranged from 5.4–92.0 μg g −1 (dry wt) with an average of 32.6 μg g −1. The surface distribution of the petroleum hydrocarbons showed an increasing trend towards the north-east, and among the individual transects there was a pronounced increasing trend towards the north-west direction. Despite off-shore oil-related activities as well as a potential impact from the 1991 oil spill, the concentrations of petroleum hydrocarbons in the study area were relatively low. This finding may be attributed to the effectiveness of weathering processes. The distribution of the saturated hydrocarbon fractions exhibited, principally, the following: 1. the presence of n-alkanes between C 15 and C 33 in nearly all samples with a lack of predominance of odd/even carbon numbers; 2. the presence of an Unresolved Complex Mixture (UCM) in most of the samples; 3. the n-C 18/phytane ratios reflect the limited influence of microbial degradation; 4. a relative distribution of the saturated hydrocarbons indicating weathering classification equivalent to stage I.

Hydrocarbon influence on denitrification in bioturbated Mediterranean coastal sediments

An in situ experiment has been carried out inbioturbated Mediterranean coastal marine sediments (Gulfof Fos) in order to study the influence of hydrocarbons ondenitrification after 1, 4 and 6 months. In theabsence of hydrocarbons in the control sediments, the presenceof macrofauna stimulated denitrificationby 160%. This stimulation is induced by sediment reworkingthat favours both direct NO-3 supply fromthe water column and the penetration of O{2}, which in turnstimulated nitrification, the other source ofNO-3 in sediment. The presence of hydrocarbons in theexperimental sediments either stimulated orinhibited the denitrification. The denitrification response tothe presence of hydrocarbon is dependent onthe quantity of matter buried by the macrofauna activity. Insmall quantities, the organic matter relatedto hydrocarbons 120% enhanced the denitrification compared tothe controls. On the other hand, whenburied hydrocarbon concentrations were higher (>100 mgsaturated hydrocarbon fraction kg-1 drysediment), the denitrification was inhibited.On the basis of the results obtained, a descriptive model ofthe patterns of denitrification in relation to the presence ofmacrofauna and the distribution of hydrocarbons in sediments is proposed.

Petroleum hydrocarbon pollution: the distribution in sediment and water of the New Calabar River, Port Harcourt, Nigeria

The hydrocarbon distribution in sediments and water samples of the Port Harcourt segment of the New Calabar River, Nigeria was sampled during the wet and dry seasons of 1990 and 1991. The results demonstrate that a very heterogenous distribution of petroleum hydrocarbon exists in this segment of the river and that the life-style and feeding habits of the organisms in this environment will have a dramatic effect on their hydrocarbon exposure. Site variability indicates that most of the hydrocarbons in sediment and water of the New Calabar River are of anthropogenic origin. The baseline station, BLF, is the least exposed to petroleum hydrocarbon pollution. Seasonal variation gave a high hydrocarbon level during the rainy season which resulted from slow rate of volatilization during this season. Contamination factor, measured as the ratio of the median concentration in the monitoring zones and the median concentration of the baseline values ranged from 1.73 to 8.47 in sediments and 2.02 to 2.62 in water.

Polyaromatic Hydrocarbon Distributions in Sediments of an Urban Catchment

Abstract The levels of six selected polyaromatic hydrocarbons (PAHs), anthracene, fluoranthrene, pyrene benzo(b)and(k)fluoranthenes, benza(a)pyrene and benzo(ghi)perylene, within the sediments of a 5.3 km2 urban catchment in N.W. London have been investigated over a 12 month period. The variations in levels throughout the catchment are discussed in terms of the influence of established hydrocarbon-sediment associations on both the contributions of different source inputs and on the controlling effects of on-line sedimentation ponds and the terminal receiving basin. These factors cause local variations within the overall pattern which demonstrates an increase in sedimentary PAH concentrations downstream as the percentage urban surface area increases. The PAH distribution is essentially hydrauli-cally controlled through discontinuous resuspension of the mobile surface sediment layer during turbulent storm flow conditions.

Distribution of poycyclic aromatic hydrocarbons in sediments from estuaries of south-eastern Australia

Concentrations (�g/kg dried sediment) of the polycyclic aromatic hydrocarbons (PAH) benzo[a]pyrene (B[a]P) and perylene have been measured in sediments taken from three locations in south-eastern Australia: a highly urbanized estuary (Yarra River), a marine bay (Corio Bay), and an estuary remote from urban activity (Mallacoota Inlet). Most concentrations of B[a]P lay in the range 200-800 �g/kg and these values are comparable to values found in similar situations in other parts of the world. The minimum concentration of B[a]P observed was 20�g/kg in Mallacoota Inlet; the maximum concentration was 6800 �g/kg at one location in a tributary of the Yarra River where the sediment was visibly contaminated with oil. The ratio of B[a]P:perylene was 1.0-2.0 in all three areas and this ratio is significantly lower than for aerosols in the Melbourne atmosphere, suggesting that deposition of aerosol is not the major contributor to PAH in sediments.

Geochemical distribution of hydrocarbons in sediments from mid-Narragansett Bay, Rhode Island

The concentration of hydrocarbons (saturated and aromatic) and synthetic chlorinated compounds (Chlordane, DDT, and PCBs) decreased with depth in sediment cores from mid-Narragansett Bay and reached background levels at different depths. These depths were in general agreement with those expected based on the chronological inputs of these materials to the Bay. Although the total hydrocarbons concentration decreased with depth, the biogenic n-alkanes ( n-C 25,27,29,31,33) showed a fairly constant concentration with depth as did the organic carbon content of these sediments. The n-alkane odd/even ratio increased with depth in the cores. Size fractionation (> 45 μm and < 45 to > 0.3 μm) of two core sections showed more hydrocarbons associated with the smaller size fraction in the surface section, while the lower section had approximately equal concentrations in both fractions. These trends suggest that over the time period covered by these cores the inputs of biogenic materials has remained relatively constant, while the input of anthropogenic hydrocarbons has increased dramatically during the last 100 yr. This increase is probably due to the expanded use of petroleum over this time period and subsequent chronic inputs to this estuarine environment.

A comparative survey of petroleum hydrocarbons in lake sediments

Hydrocarbon distribution in sediments from three lakes are related to the level of human activity in the respective drainage basins. Petroleum hydrocarbon contamination is found in surface sediments of a lake surrounded by a major city, compared to no detectable contamination in a lake located in a National Park.

Accumulation of Polychlorinated Biphenyls in Ecosystems

Accumulation of Polychlorinated Biphenyls in Ecosystems

Accumulation of Polychlorinated Biphenyls in Ecosystems

Accumulation of Polychlorinated Biphenyls in Ecosystems

Geochemical Exploration Techniques in U.S.S.R.: ABSTRACT

Geochemistry is widely used in field operations, and represents about 25 per cent of the petroleum exploration research in the U.S.S.R. Three approaches are used: (1) subsurface prospecting which included mudlogging, End_Page 381------------------------------ hydrocarbon distributions in sediments, and geochemical criteria for indicating oil such as the presence of organic compounds in waters; (2) surface prospecting which is concerned with rates of diffusion and filtration of hydrocarbons through sedimentary rocks, micro-biological detection of hydrocarbons, and the evaluation of radiometric, organic, and inorganic anomalies of the surface; (3) studies on the origin of petroleum and the recognition of favorable oil forming environments. About 90 per cent of the 300 geochemical field parties are doing subsurface prospecting. The other 10 per cent are engaged in surface surveys, and these are on a research basis. They are limited to arid areas of shallow young sediments such as around Volgograd, Baku, and Turkmenia. In contrast, about half of the geochemical research at 30 institutes or more in the U.S.S.R. involves surface prospecting techniques. The Soviets hope to develop a practical surface method that can be combined with geology for use in stratigraphic prospecting. In general, the Soviet scientists seem to be using more manpower and developing more geochemical parameters for field use than U. S. oil companies. The established facts of petroleum geochemistry, such as the organic nature of source beds and the detection of hydrocarbons in sediments and subsurface waters, are understood and taken into account in exploration programs. Thus the practical application of geochemistry in exploration is more widespread than in the U. S. End_of_Article - Last_Page 382------------