Branched-chain and cyclopropanoid acids in a recent sediment

From the recent sediments of a small productive lake in the English Lake District 10-methyl and cis-9, 10-methylene C₁₆ acids and also 10-methyl, cis-9, 10-, and cis-11, 12-methylene C₁₈ acids have been identified as constituents of the branched/cyclic acid fraction.     

Selective enrichment of steroid and triterpenoid hydrocarbons from crude oil using gel permeation chromatography for stable carbon isotope analysis

Gel permeation chromatography (GPC) using a high performance liquid chromatography (HPLC) system was studied for the separation and enrichment of steroid and hopanoid hydrocarbons from crude oil for stable carbon isotope analysis. A crude oil sample was pretreated using silica gel chromatography and 5A molecular sieve to remove polycyclic aromatic hydrocarbons and n-alkanes. The GPC behavior of both the pretreated saturated hydrocarbon fraction of the oil and standard steroid [5α(H), 14α(H), 17α(H) C₂₇–C₂₉ steranes], hopanoid [17α(H) C₂₇ trisnorhopane, 17α(H), 21β(H) C₂₉–C₃₂ hopanes] and triterpenoid [18α(H)-oleanane, gammacerane] mixtures were examined. The results indicate that 17α(H), 21β(H) hopanes as well as steranes could be enriched efficiently using GPC and that they could be obtained without removing n-alkanes from the oil saturated hydrocarbon fraction. The GPC behavior of steroid and triterpenoid hydrocarbons was controlled by molecular size and shape.     

Early chlorin diagenesis in a recent aquatic sediment

Chlorophylls a and b, pheophytins a and b, pheophorbides a and b and pyropheophorbide a were identified in a Recent sediment (Priest Pot from Cumbria, U.K.) by laboratory preparation and structure elucidation by NMR and FAB-MS, and HPLC coelution with sedimentary extracts. Quantitative depth profiles revealed a steady decrease of the ratios of chlorophylls to pheophytins, and also a different but fairly constant a to b ratio for the pheophytins and the chlorins.     

Sterol diagenesis in a recent marine intertidal sediment

The abundance of sterols in sediment depth profiles is determined by variations in input source abundances and diagenesis. Deconvolution of these variables would permit accurate estimation of degradation rates and initial input source contributions of sterols to the sediments. In this study we have demonstrated the application of a simple mathematical approach to the estimation of the relative stabilities of a range of sterols in a microbially-poor temperate intertidal sediment. The results indicate that st-5-enols and possibly 4-methyl sterols are less stable than other sterols in this environment. Since dehydration reactions of sterols would be favoured by both a 4-methyl substituent and a C5,6 double bond, whilst other processes would not be as selective, it seems probable that this abiological process predominates in the Corner Inlet sediments.     

Vertical profile of polycyclic aromatic hydrocarbons in a sediment core from a reservoir in Osaka City

Concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured in a dated sediment core from a reservoir at Osaka City, Southwest Japan. The sediment core consisted of deposits collected over a period of almost 70 years whose PAH content would serve as a historical record of atmospheric environment at Osaka City. Total PAH concentrations varied from 4.2 to 26 mg kg⁻¹ dry wt, and peaked in the 1940s, reflecting the occurrence of a large fire due to air attacks during World War II. The results indicated that warfare had the largest impact on atmospheric environment in Osaka City. Total PAH concentrations decreased in the post-war period except for a small peak. In the 1950s, there was a downward trend from the 1970s to the present. These trends can be ascribed to the growth of industrial activities and the regulation of atmospheric pollutant emissions, respectively.     

Tetra- and pentacyclic,naturally-occurring,aromatic hydrocarbons in recent sediments

Several polycyclic aromatic hydrocarbons (PAH) have been identified in recent Amazon River and Cariaco Trench sediments. The skeletal structures of these compounds suggest triterpenoid precursors. The tetracyclic compounds seem to result from A-ring cleavage and the pentacyclic compounds from aromatization which begins with ring A and proceeds through ring D. These compounds are another example of the environmental occurrence of natural PAH.     

The global distribution of polycyclic aromatic hydrocarbons in recent sediments

Polycyclic aromatic hydrocarbons (PAH) and their alkyl homologs are distributed in sediments throughout the world. The qualitative PAH pattern is remarkably constant for most of the locations studied, and the quantitative PAH abundance increases with proximity to urban centers. These findings are consistent with anthropogenic combustion's being the major source of these compounds. Two non-combustion sources of PAH have also been noted: retene coming from abietic acid and perylene probably coming from various extended quinone pigments.     

Kinetics of the aromatisation of rearranged ring-C monoaromatic steroid hydrocarbons

The kinetics of the aromatisation of both rearranged and non-rearranged monoaromatics have been investigated in the laboratory under free radical conditions. These studies have indicated that the aromatisation rate constant for the non-rearranged is greater than that for the rearranged isomers at any one particular temperature. Since the members of the rearranged series coelute with their non-rearranged counterparts when both series are present in geological extracts, these results suggest that care needs to be exercised when assessing extents of maturation using monoaromatic and triaromatic steroid hydrocarbons.     

Vertical transport of steroid alcohols and ketones measured in a sediment trap experiment in the equatorial Atlantic Ocean

The vertical flux and free steroid alcohol (sterol) and ketone composition of particulate material was determined using sediment traps deployed at 389, 988, 3755 and 5068 m at a station in the equatorial North Atlantic, PARFLUX E. Cholest-5-en-3β-ol (cholesterol) was found to be the dominant sterol in all the traps. This compound had a maximum flux at 988 m, accounting for more than 90% of the sterols at this depth. Inputs from mesopelagic Zooplankton populations living in or migrating to depths between the 389 and 988 m traps appear to be responsible for this distribution. The deeper two traps exhibited an increased flux of phytosterols relative to cholesterol, probably due to (a) the incorporation of labile phytoplankton remains in fecal pellets and rapid transport into the deep sea and (b) differential dissolution of heterogeneous large particles. A maximum of 5–22% of the sterols produced in the euphotic zone were present in the 389 m trap. This value drops to less than 1% for the 5068 m trap, 200 m above the sediment surface.In general steroid ketone fluxes gradually decreased with depth. Δ4-Stenones were found in greater abundance than their saturated counterparts. Cholest-4-en-3-one was the major steroid ketone detected in all the traps. A five-fold increase with depth in the cholest-4-en-3-one to cholesterol ratio is most likely due to microbial oxidation of sterols to steroid ketones, or higher Δ4-stenone inputs relative to sterols from organisms.     

Mono- and dicyclic unsaturated triterpenoid hydrocarbons in sediments from Lake Masoko (Tanzania) widely extend the botryococcene family

A mixture of C₃₃–C₃₇ botryococcenes and partially reduced derivatives was isolated from ca. 32,000 year old sediment from Lake Masoko, a freshwater crater lake in the Rungwe Range area (Tanzania). Botryococcenes and derivatives accounted for 246 μg/g dry sediment and for >92% of the hydrocarbon fraction; 1D and 2D nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry allowed the structure of the dominant botryococcene (43% of hydrocarbon fraction) to be established, after purification using high performance liquid chromatography (HPLC). The compound is a novel tetraunsaturated dicyclic C₃₄ botryococcene and is named C₃₄ masokocene. Overall, the structures of six other novel botryococcenes and four partially reduced derivatives were tentatively assigned. The structures of the new biomarkers, three dicyclic C₃₄–C₃₆ botryococcenes (or masokocenes) and seven monocyclic C₃₄–C₃₇ analogues are discussed along with their biosynthetic relationship. The high abundance of such polyunsaturated compounds preserved in 32,000 year old sediment from the lake indicates an aquatic ecosystem dominated at the time by the green alga Botryococcus braunii, as well very good preservation of the organic matter.     

Simultaneous electrokinetic removal of polycyclic aromatic hydrocarbons and metals from a sediment using mixed enhancing agents

The maintenance of harbor waterways generates large amounts of dredged sediments which are often rich in coexisting organic and inorganic contaminants. Electrokinetic remediation treatments have recently been developed for the simultaneous removal of heavy metals and polycyclic aromatic hydrocarbons (PAHs), using various enhancing agents generally tested sequentially. In this study, different processing fluids were tested, alone or mixed, to improve the decontamination of aged model sediment contaminated with cadmium, lead, chromium, copper, zinc, and five PAHs. Nitric acid (NA) and citric acid (CA) were tested to avoid the formation of an alkaline front into the sediment and favor the metals removal, while an anionic surfactant [sodium dodecyl sulfate (SDS)] and a nonionic surfactant (Tween 20) were tested to solubilize and mobilize PAHs. Processing fluids were circulated under a constant voltage gradient of 1 V cm^?1 for 10–14 days. NA showed an excellent potential to remove metals (76.8–99.9 % removal) and PAHs (70.3–89.7 % removal) in a single run. Besides, the mixture of Tween 20 and CA, more environmental friendly, could be considered as a relatively good processing fluid for the simultaneous removal of metals (10.3–90.8 % removal) and PAHs (53.6–61.6 % removal) from the fine-grained sediment, while SDS mixed to CA was not a good candidate for this purpose (0.1–65 % removal for metals and 34.1–41.0 % removal for PAHs).     

Polycyclic aromatic hydrocarbons in the environment: homologous series in soils and recent marine sediments

Soils and recent marine sediments contain a complex polycyclic aromatic hydrocarbon assemblage. The many series of alkylhomologs have a similar molecular weight distribution, and it varies little over a wide range of depositional environments. It is suggested that these hydrocarbons are formed in natural fires, are dispersed and mixed by air transport and eventually deposited into surface sediments. The analytical, geochemical and environmental implications of these findings are discussed.     

Microbial lipids of an intertidal sediment—I. Fatty acids and hydrocarbons

A detailed study has been made of the solvent extractable monocarboxylic, dicarboxylic and hydroxylated fatty acids and n-alkanes in a surface intertidal sediment, and the distributions compared to microorganisms cultured from the sediment. Diatoms are shown to contribute most of the monocarboxylic acids, particularly the significant amounts of polyunsaturated acids present, and a small proportion of the n-alkanes. Bacteria contribute between 11 and 14% of the monocarboxylic acids and markers for this, including trans-monounsaturated acids, are proposed. Detritus from the sea-grass Zostera muelleri is a major source of the α-hydroxy-, ω-hydroxy and α,ω-dicarboxylic acids in the sediment and a minor contributor of n-alkanes and long-chain fatty acids.     

Levels of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in sediment of bitumen deposit impacted area

Polycyclic aromatic hydrocarbons and polychlorinated biphenyls were investigated in sediment of bitumen deposit impacted area of Agbabu, Nigeria, to determine the present level of contamination with these toxic compounds prior to exploitation. Samples were collected during the dry season (March) and the wet season (August) of year 2008. Analysis was carried out with gas chromatography using mass spectrometry detector for polycyclic aromatic hydrocarbons and flame ionization detector for polychlorinated biphenyls. In the dry season sum of concentration of PAHs ranged from zero to 0.12 ± 0.06 ppm, while in the wet season the minimum was 0.18 ± 0.07 ppm and the maximum was 1.04 ± 0.16 ppm. Most of these values were higher than sum of polycyclic aromatic hydrocarbons concentrations of 1–10 μg/kg indicating that they were likely to come from anthropogenic sources. Average concentrations of PAHs such as naphthalene and benzo (a) pyrene obtained in sediment in the wet season in some of the stations were higher than recommended limits. The linear regression analysis between sum of concentrations and percentage organic carbon showed no significant correlation in sediment in the dry season (r² = 0.0025) and in the wet season (r² = 0.1345). The predominance of 4–6 ringed polycyclic aromatic hydrocarbons and the ratios between pairs of individual polycyclic aromatic hydrocarbons showed that they are likely to have come from pyrolytic sources. No polychlorinated biphenyl congener was detected in the samples.     

Predictive environmental impact assessment of total petroleum hydrocarbons in petrochemical wastewater effluent and surface sediment

The contamination level of total petroleum hydrocarbons (TPH) in wastewater and surface sediment samples from the Petrochemical Special Economic Zone (PETZONE) and adjacent coastal area in Musa Bay (in Northwest of Persian Gulf) was examined. Concentrations of TPH in the Musa Bay sediments ranged from 16.48 to 97.15 µg/g dry weight (dw) with average value of 48.98 ± 30.36 µg/g dw. The highest concentrations were estimated in stations close to the coastline, locations affected by intensive petrochemical discharges and shipping activities. The average TPH concentration in the PETZONE wastewater effluent samples was 5.22 mg/L, with a range of 0.06–35.33 mg/L. Regarding environmental impact assessment, the concentration of TPH was lower than the wastewater effluent discharge standard at most of the monitoring stations inside PETZONE companies, with the exception of stations 15, 16 (Imam Khomeini petrochemical company 1, 2) and 17 (Razi petrochemical company). These stations were considered as moderate environmental aspects, suggesting that concentration of TPH in the wastewater effluents of these petrochemical companies could be considered as contaminants of concern in the PETZONE area.     

Distribution of polycyclic aromatic hydrocarbons in recent sediments of Sundarban mangrove wetland of India and Bangladesh: a comparative approach

The present work is the first attempt to compare the data of a comprehensive study of the origin and distribution of 16 priority pollutant polycyclic aromatic hydrocarbons (PAHs) in surface sediments (<63 μm) from 18 sampling stations, 9 from Sundarban of Bangladesh and 9 from Indian counterpart. Σ19PAHs concentration in sediments showed wide variations from 208.3 to 12,993.1 ng g^?1 dry weight in Indian Sundarban, whereas 208.4 to 4,687.9 ng g^?1 in the case of Bangladesh. Fluoranthene, pyrene, benzo(b)fluoranthene, benzo(a)pyrene and dibenzo(a,h)anthracene were predominant species for both the countries. The PAH diagnostic ratios indicated that the PAHs in sediments from both the countries were of mixed source of hydrocarbons of both petrogenic and pyrolytic origin. According to the numerical effect-based sediment quality guidelines, the levels of PAHs in the Sundarban wetland of Bangladesh and India should not exert adverse biological effects. The TEQ values calculated for samples from the Bangladesh and Indian Sundarban varied from 13.68 to 1,014.75 and 1.31 to 2,451 ng g^?1 d.w. with an average of 221.02 and 358.63 ng g^?1, respectively. The overall contamination status of PAH was higher in India than Bangladesh.     

学习实践“改造成矿作用”理论——以滇中砂岩铜矿为例兼论改造作用的上、下限问题

"改造成矿作用"是涂光炽院士提出的新理论。这一理论有如下基本论点和鲜明特色:矿质来源的广泛性;成矿流体的特殊性;成矿元素的活泼性;改造作用的内生性;断裂构造的主导性;赋矿岩石的多样性;改造矿床的普遍性;成矿作用的独特性与应有地位——矿床分类的四分法。滇中大姚-牟定式砂岩铜矿是典型的沉积-成岩-后生-改造成因。其主要论据与以下要素有关:裂谷成矿背景;矿源层(K、J)、矿源岩(元谋古陆);矿体受地层层位、岩相、岩性控制,其生成与煤系(提供有机质)、盐层(提供卤素)密切相关;矿体形态产状、矿石结构构造、成矿流体性状与水的来源、有机质类型及其作用在不同成矿期、成矿阶段显著不同。从岩石学的名词概念来解读和划分"改造成矿作用"的上限与下限:上限确定在后生作用之后,下限在变生作用之末。     

Thermal alteration experiments on organic matter in recent marine sediment—II. Isoprenoids

Several isoprenoid compounds were isolated from a heat-treated marine sediment in the southern California continental shelf (from Tanner Basin) which were not present in the original sediment. Among the compounds identified were: phytol, dihydrophytol, C₁₈-isoprenoid ketone, phytanic and pristanic acids, C₁₉- and C₂₀-monoolefins, and the alkanes 2,6,10-trimethylpentadecane, pristane and phytane. The significance and possible routes leading to these compounds is discussed.