Ozonation of triterpenoids: Implications for early diagenesis of biomarkers in oxic environments

This study examines the fate of commonly found organic natural products under exposure to ozone to simulate early oxic diagenesis. The model compounds β-amyrin, lupenone and friedelin have been investigated by ozonation in the presence of water. The transformation products were identified or proposed based on their fragmentation patterns in mass spectra. The double bonds located at the isopropenyl group of lupenone and ring C of β-amyrin are the main reaction sites in the ozonation reaction. The major products identified from the ozonation of β-amyrin are β-amyrone, 12,13-epoxyoleanan-3β-ol, 11-oxo-olean-12-en-3β-ol, 12-oxo-oleanan-3β-ol. In addition, 8,14-seco-12-oxo-olean-14-en-3β-ol, 8,14-seco-12-oxo-olean-13-en-3β-ol and 8,14-seco-oleana-3,12-dione, generated from the bond cleavage between C-8 to C-14 of 12-oxo-oleanan-3β-ol and 12-oxo-oleanan-3-one, respectively, have also been detected. 22,29,30-trisnorlup-18(19)-en-3-one, 22,29,30-trisnorlupan-3-one, 22,29,30-trisnorlupana-3,19-dione, 22,29,30-trisnorlupana-3,12-dione, lupeol, lup-22(29)-en-3-on-29-ol, 22,29-epoxylupan-3-one, lupan-3-on-29-al, lupan-3-on-29-ol and 19,22-epoxylupan-3-one are the major products from the ozonation of lupenone. No transformation product was detected for friedelin, probably due to its stability to ozonation.     

Occurrence of highly abundant bacterial hopanoids in Dajiuhu peatland, central China

Based on gas chromatography and gas chromatography-mass spectrometry analyses, an amazing amount of hopanoids was detected in the peat deposits in the Dajiuhu National Wetland Park in central China. The hopanoids identified included hopanes (C₂₇-C₃₁ αβ, C₂₇-C₃₂ ββ, C₂₉ βα), hopenes (hop-22(29)-ene, 22,29,30-trinorhop-17(21)-ene, hop-17(21)-ene, hop-13(18)-ene, etc.), hopanoic acids (C₃₁-C₃₄ ββ, C₃₂-C₃₃ βα, C₃₂ αβ), hopanols (C₃₂ ββ and αβ) and hopanone (22,29,30-trinorhop-21-one). C₃₁ αβ-22R hopane was found to be the dominant hopanoid, more abundant than individual nalkanes derived from higher plants. These hopanoids, exclusive of some hopenes, are proposed to be primarily from bacteria. The dominant C₃₁ αβ-22R hopane in young sediments, without any thermal maturation, might be formed through microbial epimerization under acidic conditions in the peatland as suggested before, or directly from aerobic bacteria. This finding highlights the importance of microbes in the formation of peatland as well as in the reconstruction of paleoenvironments.     

Organic Geochemistry of the Cenomanian–Turonian Bahloul Formation Petroleum Source Rock,Central and Northern Tunisia

Total organic carbon (TOC) determination, Rock‐Eval pyrolysis, extractable organic matter content (EOM) fractionation, gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS) analyses, were carried out on 79 samples from eleven outcrop cross sections of the Bahloul Formation in central and northern Tunisia. The TOC content varied between 0.23 to 35.6%, the highest average values (18.73%, 8.46% and 4.02%) being at the east of the study area (at Ain Zakkar, Oued Bahloul and Dyr Ouled Yahia localities, respectively). The Rock‐Eval maximum pyrolysis temperature (Tmax) values in the 424–453°C range delineated a general east‐west trend increase in the organic matter (OM) maturity. The disparity in hydrogen index (HI) values, in the range 114–824 mg hydrocarbons (HC) g^?1 TOC, is relevant for the discrepancy in the level of OM preservation and maturity among localities and samples. The n‐alkane distributions, maximizing in the C17 to C20 range, are typical for a marine planktonic origin, whereas pristine/phytane (Pr/Ph) average values in the 1–2 range indicate an oxic to suboxic depositional environment. Pr/n‐C17 and Ph/n‐C18 ratios in the 0.38–6.2 and 0.68–3.25 range, respectively, are consistent with other maturity indicators and the contribution of specific bacteria to phytol as a precursor of isoprenoids. The thermal maturity varies between late diagenesis to main‐stage of petroleum generation based on the optic and the cis‐trans isomerisation of the C29 sterane [20S/(20S+20R) and 14β(H),17β(H)/(14β(H),17β(H)+14α(H),17α(H)), respectively] and the terpane [18α(H)22,29,30‐Trisnorneohopane/(18α(H)22,29,30‐Trisnorneohopane+17α(H)22,29,30‐Trisnorhopane): Ts/(Ts+Tm)] ratios. The Bahloul OM is represented by an open marine to estuarine algal facies with a specific bacterial contribution as revealed by the relative abundance of the ααα‐20R C27 (33–44%), C28 (22–28%) and C29 (34–41%) steranes and by the total terpanes/total steranes ratio (1.2–5.33). These results attested that the Bahloul OM richness was controlled both by an oxygen minimum zone induced by high productivity and restricted circulation in narrow half graben structures and around diapirs of the Triassic salt.     

Changes in hydrocarbon maturity indices with coal rank and type,Buller Coalfield,New Zealand

The Buller Coalfield (South Island, New Zealand) is an inverted late Paleogene Basin that contains middle Eocene bituminous coals which exhibit considerable variation in both coal rank (across-basin), and coal type (in-seam). Twenty-two fractionated bitumen extracts of Brunner Coal Measures coal samples from 12 drillholes were analyzed by GC and GC–MS to characterize the effect of coal rank and type on conventional hydrocarbon maturity indices at the beginning and end of the oil window (0.56–1.26% Ro_max).The Carbon Preference Index, pristane/phytane and isoprenoid/n-alkane ratios evolve throughout the high volatile bituminous B rank stage, while other biomarker ratios [18α(H)-22,29,30-trisnorneohopane/17α(H)-22,29,30-trisnorhopane (Ts/Tm), 18α(H),21β(H)-30-norneohopane (C₂₉ Ts)/17α(H),21β(H)-30-norhopane and C₃₀ diahopane/hopane] do not show appreciable change in value until medium volatile bituminous rank. Various aromatic based ratios appear to be more effective in delineating rank throughout the entire oil window; in particular the Methylphenanthrene Index and vitrinite reflectance are positively correlated over the entire bituminous rank range. However, subtle changes in depositional conditions (variable coal type) complicate these rank estimates. Within a given coal seam, variation in CPI, isoprenoid/n-alkane and hopane/sterane ratios appear to be related to the hydrogen content of the coal, while the homohopane index and the oleanane/hopane ratio covary with sulfur content. As with depressed vitrinite reflectance values, MPI is similarly lowered in the perhydrous samples. The mechanisms that control these hydrocarbon parameters during deposition and diagenesis are complex and convoluted, however, changes in bacterial activity and community (with marine incursion) appear to play an important role. Due to these anomalies, none of the hydrocarbon maturity indices calculated can be singularly used to constrain coal rank.     

The geochemistry of aliphatic and polar organic tracers in sediments from Lake Bera, Malaysia

The molecular distributions of homologous aliphatic lipid compounds (n-alkanes, n-alkanoic acids, n-alkanols, n-alkanals and n-alkan-2-ones) were investigated in sediments of Lake Bera, Malaysia as well as in plant waxes from the vicinity using gas chromatography-mass spectrometry. In addition, triterpenoids of the oleanane, ursane, lupane and friedelane series, and their diagenetic products were also identified. Using the aquatic proxy P_aq, it was found that the n-alkanes present in surface sediments S1, S5 and S6 correspond to an input from emergent macrophytes, whereas in sediments collected from open water (S2, S3 and S4) they correspond to input from submerged/floating macrophytes. The presence of n-alkan-2-ols, a commonly found homologous series in the sediments as well as in the plant wax, is novel here. In addition, the presence of 24-methylcycloart-22-enol and 24-ethylcycloart-22-enol in sediments as well as the plant wax of Pandanus helicopus, a dominant reed around the lake, also supports the input of plant biomarkers to the sediments. The occurrence of 5-membered ring triterpenoid derivatives as major diagenetic products of the triterpenoids identified (e.g. friedelan-2,3-dione) shows that the degradation of the organic matter in the sediments occurs mainly under oxic conditions. Also, the presence of ring-A degraded triterpenoids (dihydroputranjivic acid, 3-nor-2,4-seco-friedelane, 4α- and 4β-3-norfriedelanes, A-norfriedel-10-one, and A-norfriedel-8-en-10-one) and the aromatized triterpenoid hydrocarbons (mono- and triaromatic derivatives) as minor diagenetic products indicates photochemical and microorganism-mediated alteration reactions of natural products in the sediments. Additional novel polyfunctional friedelane derivatives, namely friedelane-2,3-dione, friedelane-1,3-diol-2-one and friedel-1(10)-ene-1,3-diol-2-one were identified for the first time in this study. These novel polyfunctional triterpenoids were inferred to derive from the oxidation of the triterpenoids from higher plants in this oxic tropical environment. For future reference purposes, the mass spectra of the identified polar triterpenoids are also presented here. This study provides important data on the biogeochemistry of organic matter in a tropical lake of SE Asia.     

The nature and origin of sesquiterpenoids in some tertiary fossil resins

Analyses of two Tertiary fossil resins and a Tertiary montan wax have revealed the presence of a number of sesquiterpenoids. Using gas chromatographic retention data obtained on both polar and non-polar stationary phases and mass spectral comparisons with authentic compounds, the sesquiterpenoids α-cedrene, cedrane, cuparene, cedren-10-one, 8βH cedran-9-one and cuparenic acid have been identified in the fossil resin retinellite and a montain wax (both Oligocene) from lignite beds in the Bovey basin of Devon, England, and in the Pliocene fossil resin ionite from the lone valley of California. U.S.A.The sesquiterpenoids α-cedrene, cuparene and cuparenic acid are characteristic constituents of the essential oils of the Cupressaceae, a family of trees and shrubs of the order Coniferales, and it is argued that these fossil resins, and the montan wax, were derived from older forms of this family of plants. The ketones cedren-10-one and 8βH cedran-9-one, and the saturated hydrocarbon cedrane, are not reported to be constituents of modern genera of Cupressaceae and may have been formed during diagenesis. The cedrane occurring in these deposits appears to be a chemical hydrogenation product of α-cedrene. The ketones, on the other hand, may have resulted from the oxidation of α-cedrene although the mechanism of these reactions is not clear. If the ketones are not undetected constituents of these plants, then the presence in these deposits of both oxidised and fully-reduced α-cedrene products infers that separate phases of oxidation and reduction occurred during the diagenesis of the fossil resins and the montan wax.     

用储层岩石抽提物的饱和烃色谱指纹识别油气层

利用储层岩石抽提物的饱和烃色 质总离子图的指纹特征判识储层的流体（油、气）类型。油层或油饱和的储层,饱和烃色 质总离子流图的特征是正构烷烃碳数分布宽,碳数分布在C₁₅～C₃₈之间,与原油样品的正构烷烃碳数分布相似;凝析气层的正构烷烃碳数分布略窄一些,碳数分布在C₁₅～C₃₅之间,低碳数（小于C₂₁）的正构烷烃相对于油层富集,高碳数（大于C₂₁）的正构烷烃丰度明显低于油层;干气层的正构烷烃碳数分布最窄,碳数分布在C₁₅～ C₂₈之间,只有低碳数的正构烷烃,高碳数的正构烷烃丰度极低。据此可用来识别油层、凝析气层和干气层,也可用于一些测井资料不全或测井质量差的老井的油气层复查、测井难以识别的火成岩油气层的识别,还可用于地层评价,为油气酸化层位的优选提供科学依据。     

Organic geochemical investigation of far-field tsunami deposits of the Kahana Valley,O‘ahu,Hawai‘i

Far-field tsunami deposits observed in the Kahana Valley, O‘ahu, Hawai‘i (USA), were investigated for their organic-geochemical content. During short high-energy events, (tsunamis and storms) organic and chemical components are transported with sediment from marine to terrestrial areas. This study investigates the use of anthropogenic based organic geochemical compounds (such as polycyclic aromatic hydrocarbons, pesticides and organochlorides) as a means to identify tsunami deposits. Samples were processed by solid–liquid extraction and analyzed using gas chromatography–mass spectrometry. A total of 21 anthropogenic marker compounds were identified, of which 11 compounds were selected for detailed analysis. Although the tsunami deposits pre-date industrial activity in Hawai‘i by several hundred years, distinct changes were found in the concentrations of anthropogenic marker compounds between sandy tsunami deposits and the surrounding mud/peat layers, which may help in identifying tsunami deposits within cores. As expected, low overall concentrations of anthropogenic markers and pollutants were observed due to the lack of industrial input-sources and little anthropogenic environmental impact at the study site. This geochemical characterization of tsunami deposits shows that anthropogenic markers have significant potential as another high-resolution, multi-proxy method for identifying tsunamis in the sedimentary record.     

Organic compounds in produced waters from coalbed natural gas wells in the Powder River Basin,Wyoming, USA

The organic composition of produced water samples from coalbed natural gas (CBNG) wells in the Powder River Basin, WY, sampled in 2001 and 2002 are reported as part of a larger study of the potential health and environmental effects of organic compounds derived from coal. The quality of CBNG produced waters is a potential environmental concern and disposal problem for CBNG producers, and no previous studies of organic compounds in CBNG produced water have been published. Organic compounds identified in the produced water samples included: phenols, biphenyls, N-, O-, and S-containing heterocyclic compounds, polycyclic aromatic hydrocarbons (PAHs), aromatic amines, various non-aromatic compounds, and phthalates. Many of the identified organic compounds (phenols, heterocyclic compounds, PAHs) are probably coal-derived. PAHs represented the group of organic compounds most commonly observed. Concentrations of total PAHs ranged up to 23 μg/L. Concentrations of individual compounds ranged from about 18 to <0.01 μg/L. Temporal variability of organic compound concentrations was documented, as two wells with relatively high organic compound contents in produced water in 2001 had much lower concentrations in 2002.     

Identification and geochemical significance of some aromatic components of coal

The aromatic fraction of a Homestead, Kentucky, coal extract was analyzed by combined gas chromatography-mass spectrometry using glass capillary columns. The aromatic fraction was further analyzed by gas chromatography using sulfur specific flame photometric detection. Seventy-eight compounds were identified, some of which have been traced to their possible biological origins. Sulfur-containing aromatic compounds are thought to originate from reaction of elemental sulfur or pyrite with hydrocarbons.     

干旱-半干旱区兰州兴隆山现代森林典型植被和土壤中类脂物分子特征及其意义

利用GC－MS对西北干旱区-半干旱区兰州兴隆山森林区典型植被与现代土壤样品中可抽提的类脂物进行了系统分析,检测出包括正构烷烃和α正构脂肪酮等一系列类脂物分子化石。在未进行族分离的情况下,检出兴隆山现代森林木本植物的正构烷烃以C₂₇或C₂₉为主峰,草本植物则以C₃₁为主峰;  土壤样品中均保留有很强的、几乎均势的C₂₇,C₂₉和C₃₁信号; α正构脂肪酮具有明显的奇碳优势,植物中以C₂₃,C₂₅或C₂₉为主峰,土壤样品以C₂₇或C₂₉为主峰;  其反映的信息是植被与微生物共同作用的结果。本研究为理解现代土壤和古土壤中类脂物所指示的植被信息、进一步探讨类脂物分子在植被(有机质)-微生物-土壤-湖泊沉积体系中存在与相互转换关系这一基础理论问题提供了科学资料。同时,为分子化石分析方法的改进和不同处理过程所得数据之间的对比和科学解释提供资料。     

Isoprenoids in a Costa Rican seep oil

The isoprenoid alkanes present in a seep oil from Costa Rica have been examined using gas chromatography and mass spectrometry. In addition to the predominance of the C₁₆ and C₁₈-C₂₀ regular isoprenoid alkanes, the C₂₁ and C₂₃-C₂₅ regular isoprenoid alkanes were identified. The C₂₆, C₂₈ and C₃₀ regular isoprenoid alkanes were tentatively identified. No evidence for the regular C₁₇, C₂₂ or C₂₇ isoprenoid alkanes was found. The compounds 3,7,11- trimethyltetradecane and 3,7,11-trimethylhexadecane were tentatively identified. It is suggested that a higher regular isoprenoid structure (or structures) is required in addition to phytol to account for the distribution of isoprenoid alkanes.     

Basic nitrogen-heterocyclic compounds in the Murchison meteorite

A fragment of the Murchison (C2) carbonaceous meteorite was analyzed for basic, $\text{N-}\text{heterocyclic}$ compounds, by dual detector capillary gas chromatography as well as capillary gas chromatography/mass spectrometry, using two columns of different polarity. In the formic acid extract 2,4,6-trimethylpyridine, quinoline, isoquinoline, 2-methylquinoline and 4-methylquinoline were positively identified. In addition, a suite of alkylpyridines and quinolines and/or isoquinolines was tentatively identified from their mass spectra. The (iso)quinolines were found to contain methyl substituents exclusively. The distribution of the pyridines observed reveals a similarity to that observed from catalytic reactions of ammonia and simple aldehydes under conditions similar to those applied in Fischer-Tropsch type reactions.     

Tri- and tetraterpenoid hydrocarbons in the Messel oil shale

The high molecular weight constituents of the branched and cyclic hydrocarbon fraction of the Messel oil shale (Eocene) have been examined by high resolution gas chromatography and combined gas chromatography-mass spectrometry. The following compounds are present: perhydrolycopene (1; lycopane), together with one or more unsaturated analogues with the same skeleton; a series of 4-methylsteranes (2c) in higher abundance than their 4-desmethyl analogues; two series of pentacyclic triterpanes, one series (C₂₇-C₃₂) based on the hopane structure (3a-e), and the other (C₂₇-C₃₁) based on the 17α-H hopane structure (3a-d, 17αH); and an intact triterpene hop-17 (21)-ene [3c, Δ 17(21)]. Only two additional triterpanes were detected in minor concentrations, viz. 30-normoretane (3b, 21αH) and a C₃₁ triterpane based on the hopane/lupane-type skeleton. The presence of these compounds suggests a significant microbial contribution to the forming sediment. Comparison of the tri- and tetraterpenoid hydrocarbons with those of the Green River Shale indicates differences in the organisms contributing to the two sediments.     

Nitrogen-heterocyclic compounds in meteorites: significance and mechanisms of formation

Samples of the Murchison (C2), Murray (C2) and Orgueil (C1) carbonaceous meteorites were analyzed for nitrogen-heterocyclic compounds using gas chromatography, cation and anion exclusion liquid chromatography and mass spectrometry. The purines adenine, guanine, hypoxanthine and xanthine were identified in formic acid extracts of all samples, in concentrations ranging from 114–655 ppb. Purines have not previously been found in the Murray meteorite and adenine. hypoxanthine and xanthine have never simultaneously been detected in meteorite extracts. All four biologically significant purines, as well as the pyrimidine uracil have now been identified in these meteorites. A number of other, previously reported N-heterocyclic compounds such as certain hydroxypyrimidines and s-triazines could not be detected in any of the extracts. Laboratory data indicated that both these classes of compounds may be formed from structurally simple precursors (such as guanylurea in the case of s-triazines) during the extraction and analysis of meteorite extracts.We find that the suite of N-heterocyclic compounds identified in meteorites do not, at present, permit a clear distinction to be made between mechanisms of synthesis such as the Fischer-Tropsch type and other candidates. Secondary reactions and conversions in meteorite parent bodies, of HCN and other nitriles produced by Miller-Urey type reactions as well as by Fischer-Tropsch type reactions, must also be considered.     

Low-temperature, polysulfide reactions of conjugated ene carbonyls: A reaction model for the geologic origin of S-heterocycles

The theoretical basis for a type of reaction of sulfur-acceptor carbon molecules with donor catenated forms of sulfur is presented. The reactions between conjugated ene carbonyls as sulfur-acceptors and polysulfide as a sulfur donor are described. The scope of this reaction is broadened by demonstrating that the room-temperature action of polysulfide on dienones produces thiophenes. Evidence is given for the structure of 2-benzoyl-5-phenylthiophene, resulting from 1,5-diphenyl-2,4-pentadien-1-one, and 2-acetyl-5-phenylthiophene, resulting from 6-phenyl-3,5-hexadien-2-one. Evidence is also presented for the structure of 2,4-dibenzoyl-3,5-diphenylthiolane, the product resulting from the action of polysulfide on the mixture of benzaldehyde and acetophenone. The same thiolane is shown to result as the minor thiolane component when chalcone reacts with polysulfide in 80% water/20% ethanol. The major component is a known rearranged thiolane identified by its physical properties. The reactiol of chalcone and polysulfide in ethanol at 0 or 25°C results in thiolane formation as evidenced by the isolation of 2,4-dibenzoyl-3,5-diphenylthiolane. However, the reaction of the same two compounds in boiling methanol (65°C) results in a competitive hydrogenation of chalcone giving dihydrochalcone in addition to the formation of thiolane. The demonstration of the low-temperature reaction of polysulfide with conjugated ene carbonyls in the present work adds an additional pathway for possible formation of S-heterocycles in the geosphere.     

Generation of isoprenoid compounds,notably prist-1-ene,via photo- and autoxidative degradation of vitamin E

In order to mimic the photodegradation of vitamin E during phytoplankton senescence and study the behaviour of the resulting photoproducts during cell lysis, vitamin E dispersed in seawater was irradiated with solar light in the presence of hematoporphyrin as sensitizer. Under these conditions, singlet oxygen-mediated photooxidation and free radical oxidation (autoxidation) acted simultaneously on the substrate, affording 4,8,12-trimethyltridecanal, 4,8,12-trimethyltridecanoic acid, 6,10,14-trimethylpentadecan-2-one, α-tocopherylquinone, 4,8,12,16-tetramethylheptadecan-4-olide, 2,3-epoxy-α-tocopherylquinone and 5,6-epoxy-α-tocopherylquinone as minor products. Different mechanisms were proposed to explain the formation of these different isoprenoids. The main products (85% of the degraded substrate) appeared to be previously described diastereoisomeric trimeric oxidation products of vitamin E, whose pyrolysis during gas chromatography–mass spectrometry (GC–MS) afforded 2,6,10,14-tetramethylpentadec-1-ene (prist-1-ene). On the basis of their greater ability to produce prist-1-ene during pyrolysis than intact vitamin E and their highly favoured production in phytoplanktonic cells, these trimers are proposed as likely sources of this isoprenoid alkene, previously identified in many pyrolysates from immature kerogens.     

褐煤高温水萃物生物产气及化学组成变化

微生物与煤的相互作用过程复杂，为了深入分析煤中有机物在生物产气过程中的作用及变化规律，选取义马褐煤和实验室保存的产甲烷菌群作为研究对象，研究褐煤水溶性有机物产气特征及其产气前后化学组成变化。利用去离子水在70℃下萃取褐煤得到水溶性有机物、水萃余煤，分别以其作为底物开展生物产气实验，并利用甲醇对产气后的残煤进行有机萃取，采用GC、HPLC-MS和GC-MS方法分析产气量变化及发酵液和煤甲醇萃取物的化学组成。结果表明，褐煤原煤、水溶性有机物和水萃余煤的产气量分别为0.46、0.45和0.15 mmol/g。产气初期水溶性有机物化学组成复杂，分子量主要集中在200~300 Da，生物产气后化合物种类减少，分子量降至150~200 Da，并且产气后发酵液中检测到一些分子中具有苯环结构的含氮和氧杂原子的化合物。水萃余煤生物产气后的甲醇萃取物中出现少量水溶性化合物如甲酰胺、乙酰胺、亚硫酸二甲酯等。70℃萃取得到的义马褐煤水溶性有机质能被产甲烷微生物利用产气，经过生物产气后煤中非水溶性有机物会转变成水溶性有机物。本研究探索了褐煤中水溶性有机物在生物产气过程中的潜在作用，为阐明煤生物产气的物质基础提供了实验依据。      

氨化学电离色谱-质谱法分析原油及岩石抽提物中的咔唑类含氮化合物

利用色谱氨化学电离质谱(GC-NH3CIMS)法分析了原油及烃源岩中的咔唑类含氮化合物,分析结果与普通色谱质谱(GC-MS)进行了对比与评价.结果表明,氨化学电离质谱法对含氮化合物具有较高的灵敏度和选择性,在氮化物含量较低或有芳烃共逸出的情况下,可以进行定量分析.氨化学电离质谱没有碎片离子产生,质量色谱图上同系物间没有碎片离子产生的相互干扰,定量结果比较准确.     

Volatile organic compounds in open ocean and coastal surface waters

Volatile organic compounds with volatilities ranging between those of n-hexane and n-pentadecane were identified in open ocean and coastal marine surface water samples taken in the north central part of the Gulf of Mexico. Approximately 40 organic compounds were found. The types and concentrations of the compounds found depended upon the extent of anthropogenic and terrestrial influences. Open ocean samples consisted mostly of aromatic hydrocarbons, whereas coastal samples included alkanes, cycloalkanes, cycloalkenes, aromatic hydrocarbons, aldehydes and chlorinated hydrocarbons. Unpolluted open ocean and coastal water samples had individual concentrations rarely exceeding 5 ng/kg; some aromatic hydrocarbons approached 15 ng/kg. n-Pentadecane dominated the hydrocarbons in these samples (50–100 ng/kg). The most polluted coastal water samples had individual volatile organic concentrations as great as 150 ng/kg with total concentrations approaching 1000 ng/kg. The terpene, limonene, was found extensively in the coastal samples (up to 40 ng/kg). Photooxidization of hydrocarbons in industrial/urban atmospheres was considered as a possible source of aldehydes present in coastal water. The dynamic headspace stripping/Tenax-GC adsorption method coupled with packed column gas chromatography, and gas chromatography-mass spectrometry were used for volatile organic analysis.