M.I. Venkatesan

Occurrence and possible sources of perylene in marine sediments-a review☆

Abstract This report presents a review of the occurrence of perylene in the marine sedimentary environment. Surface sediment samples and sediment cores predating modern anthropogenic pollution from different marine and lacustrine locations and also peat samples from various regions of the world have been analyzed for perylene. New data gathered on perylene in the current study is compared with earlier research findings to address the question of its possible origins. Several conclusions could be drawn from this data compilation. (i) Perylene is widespread primarily in reducing marine sediments, commonly found at a background level of 10 ppb. (ii) As much as 4 ppm of perylene has been detected in some unpolluted anoxic marine sediments. (iii) Perylene originates in sediments fed by both terrestrial and aquatic organic debris. (iv) Diatoms appear to be the major potential precursors for perylene in the aquatic regime. (v) The precise role of diatoms in the adsorption, entrapment or production of perylene is currently unknown. (vi) Low levels of perylene encountered in oxic sediments could be derived from anthropogenic inputs.

Distribution and transport of hydrocarbons in surface sediments of the alaskan outer continental shelf

Abstract Surface sediments from the Outer Continental Shelf of Alaska were analyzed for hydrocarbons as part of an environmental survey sponsored by NOAA/BLM. Sediments were collected from the proposed oil lease areas of Beaufort Sea, southeastern Bering Sea, Norton Sound, Navarin Basin, Gulf of Alaska, Kodiak Shelf and lower Cook Inlet. Data on normal and branched alkanes and di- and triterpenoids from capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC/ MS) indicate that the area displays little evidence of petroleum hydrocarbons (i.e., seeps) except at a few isolated stations. Beaufort Sea sediments have the highest hydrocarbon budget, whereas Kodiak Shelf sediments have the lowest. The molecular markers of the hydrocarbons are of a mixed marine autochthonous and terrestrial allochthonous origin. Norton Sound and Cook Inlet sediments contain the highest levels of terrigenous lipids and Kodiak Shelf the lowest. The abundance of alkenes implies that relatively low oxidizing conditions exist in some of the depositional areas studied, suggesting that extraneous petroleum hydrocarbons introduced into these sediments would be expected to have a relatively long residence time. The distribution of polynuclear aromatic hydrocarbons (PAH) is complex and shows a pyrolytic origin. The data on perylene strongly favor the hypothesis that it is “performed” from terrigenous precursors and transported into the marine environment with no apparent in situ generation. Polynuclear aromatic hydrocarbons of diagenetic origin are probably dominant in Gulf of Alaska and Kodiak Shelf sediments. Two stations, north of Kalgin Island, in lower Cook Inlet and one in southeastern Bering Sea show typical weathered petroleum distribution of n-alkanes and triterpenoids. Probable pathways of transport and fate of petroleum hydrocarbons in case of an oil spill are also briefly discussed.

Organic chemical characterization of sediment-trap particulates from San Nicolas, Santa Barbara, Santa Monica and San Pedro Basins, California☆

Particulate matter was collected during September–October, 1977, in particle traps suspended 30–60 m above the floor of San Nicolas, Santa Barbara, Santa Monica and San Pedro Basins, off the coast of southern California. The trap particulates were analyzed for C15–C35 hydrocarbons using gas chromatography (GC) and GC-mass spectrometry. Kerogens and humic acids were characterized by H/C, N/C, δ13C, δ15N and δ34S ratios, and by electron-spin resonance. Hydrocarbons arising from fresh and weathered petroleum, marine autochthonous and terrestrial sources were identified. The rates of petroleum deposition during the collection period followed the order: San Nicolas Basin < Santa Barbara Basin ~ Santa Monica Basin < San Pedro Basin, with the largest amount of weathered petroleum being deposited in San Pedro Basin. The rates of petroleum deposition are correlated more strongly with human activities such as shipping, and the discharge of municipal and industrial wastes, than with natural submarine oil seepage. Analyses of kerogens and humic acids indicate that the majority of the organic matter in the trap particulates is of marine origin. The water column overlying Santa Barbara Basin appears to have the highest marine productivity of the four basins studied.

Tetrahymanol: Its widespread occurrence and geochemical significance

Abstract The occurrence of tetrahymanol (gammaceran-3β-ol) in sediments from various marine depositional environments such as the Santa Monica Basin and Palos Verdes shelf (southern California Bight), the Santa Barbara Basin (off the northern California Borderland), the Atlantic shelf, slope, and rise, and the Antarctic region, as well as in bacterial/algal mats from the Santa Barbara Basin and Baja California, together with its detection in sediments from the Peru upwelling region (ODP Leg 112) and Baffin Bay (ODP Leg 105) suggests that tetrahymanol occurs ubiquitously in marine samples. Tetrahymanol is the only known likely biological precursor of gammacerane, which is found in many petroleums and shales. The common occurrence of tetrahymanol in marine environments implies that primitive organisms similar to Tetrahymena, or organisms other than Tetrahymena (other protozoa, bacteria?), are also likely to contain this compound. Its isomer, diplopterol, has also been detected in several sediment sections.

Organic geochemistry of sediments from the continental margin off southern New England, U.S.A.--Part II. Lipids

Organic geochemical measurements of the lipid fraction, comparing saturated and aromatic hydrocarbons, fatty acids, alcohols and sterols, have been carried out on six sediments cores collected from the Atlantic shelf, slope and the rise areas to evaluate the cross-shelf transport of the organic carbon. The concentration of most of the organic compound classes studied is correlated with the total organic carbon, which decreases from the shelf through slope to the rise. Terrigenous carbon is recognizable even in the slope and rise sediments, but terrestrial influx decreases relative to marine generated lipids in the slope and rise organic matter. We estimate that approximately 50% of the shelf organic matter is exported to the slope. Data of sediment trap material collected at 1200 m from 1250 m water depth are discussed and compared with that of surface sediment from 1280 m water depth (slope). Fluxes for specific organic compound classes have been computed. The fluxes are of the same magnitude as for equatorial North Atlantic trap particulates at comparable water depth, studied by other investigations.

Coprostanols in Antarctic marine sediments: A biomarker for marine mammals and not human pollution☆

Abstract The first analysis of sterols in Antarctic marine sediment cores (Bransfield Strait and McMurdo Sound) is reported here. The isolated sterols in the sediments from Bransfield Strait are comprised mainly of dinosterol (4α,23,24-trimethyl-5αcholest-22-en-3β-ol), coprostanol (5β-cholestan-3β-ol) and epicoprostanol (5β-cholestan-3α-ol) and trace amounts of cholesterol (cholest-5-en-3β-ol). The sediment cores of McMurdo Sound also contain small quantities of coprostanols in addition to large amounts of marine sterols. Dinosterol is a known dinoflagellate chemical marker, whereas coprostanols are currently being used as tracers for sewage contamination. However, sterol composition in Antarctic sediments is expected to be atypical of sewage input and probably different from those of temperate and tropical zones. The coprostanols must therefore arise from the feces of marine mammals, most probably whales which use the region for feeding and spawning. Based on the results of this study, caution should be exercised in the use of coprostanol to estimate the amount of sewage-derived organic matter transported away from impacted coastal areas.

Diploptene in Antarctic sediments

Abstract The presence of diploptene [17β(H),21β(H)-hop-22(29)-ene]in sediment cores from Bransfield Strait and McMurdo Sound, Antarctica, is reported. The organic geochemical data for these sediments provide evidence for the authigenic marine origin of this hopene.

Coprostanol as sewage tracer in McMurdo Sound, Antarctica

Abstract Sediment cores from the vicinity of sewage outfalls off McMurdo Station as well as surface grab samples from different locations in the McMurdo Sound, Antarctica were analysed for coprostanol (5β-cholestan-3β-ol) and epicoprostanol (5β-cholestan-3α-ol) to assess the degree of sewage addition to the Sound. Sediment samples close to the point source contain as much as 3 mg g−1 dry sediment of coprostanol, whereas samples farther from the source, for example from New Harbour and Granite Harbour, contain only trace levels to 40 ng g−1. Coprostanol in the sediments of latter locations most likely originates from seals rather than from sewage outfalls. It appears that sewage particles are very quickly incorporated into the sediment layers close to the discharge point in the eastern Sound. However, significant levels (930 ng g−1) of fecal sterols were detected in Cape Armitage surface sediments, indicating that the sewage plume could also have reached the seawater intake station, situated in between the outfall and Cape Armitage sampling site. These results suggest the need for a sound environmental monitoring and assessment of the existing wastewater practices in the region.

Distribution of surfactant markers in sediments from Santa Monica basin, southern California

Abstract The effluent from the Joint Water Pollution Control Plant (Los Angeles, California) and sediment cores collected in a transect from the Los Angeles sewage treatment plants (i.e. Hyperion) to 50–60 km offshore in the Santa Monica Basin, were analysed for fossil hydrocarbons (UCM) and markers of major surfactant classes, namely, linear alkylbenzenes (LAB) (anionic), trialkylamines (TAM) (cationic), and nonylphenols (NP) (non-ionic). Relative concentrations of these markers vary from sewage effluents to sediments according to their stability and hydrophobicity. In this regard, NP were detected only in the sewage effluent, but the more hydrophobic components (e.g. UCM, LAB, and TAM) were abundant even in 900 m water depth samples, with a stratigraphic distribution reflecting variations in their temporal use.

Terpenoid hydrocarbons in Hula peat: Structure and origins☆

Abstract Tri- and tetracyclic diterpenoid and pentacyclic triterpenoid hydrocarbons have been identified in the lipid extracts of three peat samples from the Hula Basin, Israel. Tentative structures for the diterpenoids have been proposed based on mass spectral studies and on extrapolation of known mass spectral fragmentation patterns of most probable biological precursors. The identification of ent-kaurenes in one peat sample appears to be a unique observation. Kaurenes most likely originated from higher plant resins. The triterpenoids in the three samples consist mainly of 17β-hopanes and hopenes, derived from recent biogenic activity. The preponderance of the 17β(H)-hopanes indicates the geological immaturity of the samples and implies that they have undergone only a mild thermal history.