The n-alkylcyclohexanes are poorly evaluated in biodegradation studies of Brazilian petroleum sam... more The n-alkylcyclohexanes are poorly evaluated in biodegradation studies of Brazilian petroleum samples. In this context, this work aimed to use the homologue series of alkylcyclohexanes to assess extend of biodegradation of 26 petroleum samples from five Brazilian sedimentary basins, analyzed by gas chromatography coupled to mass spectrometry. The n-alkylcyclohexanes compounds were detected in all samples, with a distribution similar to the n-alkane profile, in which their abundance decreasing with increasing of the biodegradation extent. Based on this, it was suggested the use of the new parameter H30/DC together with the H30/AC already proposed, calculated by the ratio between C30 hopane to the dodecyl-cyclohexane, to assess biodegradation level according Peter and Moldowan scale (PM scale). In addition, it was observed an increasing in the relative abundance of DBE 2 from class O-2, analyzed by ESI(-) FT-ICR MS, mainly due to the formation of monocyclic acids with biodegradation, ...
The Ocean decade (2021–2030) for sustainable development proclaimed in 2017 by the UN, seeks to p... more The Ocean decade (2021–2030) for sustainable development proclaimed in 2017 by the UN, seeks to promote and conserve the sustainable use of oceans, seas, and marine resources. For this, the distribution of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and biomarkers, in sediments from the Fortaleza coastal zone (Mucuripe harbor (MH) e Inner shelf (ICS)) were used to assess the impacts of anthropogenic activities in the area. The concentrations of total n-alkanes (Σ16 n-alkanes) in MH and ICS sediments varied from 35.9 to 94.9 and 17.9 to 197.3 µg g− 1, respectively, while the isoprenoids phytane and pristane in MH and ICS sediments ranged from 0.1 to 1.69 ug g− 1 and from 0.14 and 1.20 µg g− 1, respectively. Most of the sediment samples presented carbon preference index (CPI) values close to unity, indicating that the area is submitted to petroleum-related sources. The concentrations of Σ16 PHAs in MH and ICS sediments varied from 87.0 to 562.0 and 98 to 288.0 ng g− 1. This w...
Abstract Physicochemical changes that occurred during deposition of Irati black shales were inves... more Abstract Physicochemical changes that occurred during deposition of Irati black shales were investigated via outcrop samples collected in the northeastern and central-eastern Parana Basin. Various traditional geochemical indicators were used, in addition to newly detected biomarkers: C32 lanostane, simonellite, sempervirane, and C32–C35 benzohopanes. Bulk geochemistry parameters, mineralogy, and conventional saturated biomarkers, such as tetracyclic polyprenoids (TPPs), reflect restricted and hypersaline marine deposition with freshwater input and increased terrigenous contribution toward the top of the studied outcrops. This led to stratification of the water column, establishing euxinic conditions in the photic zone and reducing conditions at the bottom of the water column, which enhanced preservation of organic matter. Principal component and hierarchical cluster analyses were performed to group the samples according to their similar geochemical characteristics: prevailing marine environment (basal outcrop samples) and higher freshwater inflow with greater terrigenous contribution (top outcrop samples). These geochemical observations were corroborated by aromatic biomarkers such as triaromatic steroids, trimethylnaphthalenes, simonellite, and sempervirane. The aryl isoprenoid ratio (AIR) indicates persistence of photic zone euxinia (PZE) during Irati black shale deposition. The presence of C32 lanostane and C32–C35 benzohopanes is directly related to the hypersaline depositional environment of the analyzed samples. Finally, the C32-33/C32-35 benzohopane ratio is proposed as a thermal maturity proxy because variations in the ratio can be linked to the presence of a diabase sill and temperature catalyst minerals near one of the outcrops.
To comprehensively understand the chemical changes over time of spilled oils subject to tropical ... more To comprehensively understand the chemical changes over time of spilled oils subject to tropical climate conditions and the active weathering processes, a spill simulation experiment was conducted along 210 days with two distinct Brazilian oils (19 and 24 API) under irradiation and non-irradiation of sunlight. Isoprenoids and n-alkanes showed a great loss after 40 days for both oils under the two conditions due to evaporation. Diagnostic ratios of saturated biomarkers showed no changes, whereas the polycyclic aromatic hydrocarbons had a decreasing concentration under both conditions mainly due to evaporation. Furthermore, oxygenated polar compounds produced by photooxidation were investigated by ESI(-) FT-ICR MS and showed changes only for the oils exposed to sunlight irradiation. Based on the observed polar compositional changes, new parameters are suggested using heteroatom classes to estimate oil spill time under tropical conditions: NO3/NO2; NO3/(NO + NO2); ∑NOx/N1; (O4 + O3)/(O2 + O1); O4/(O2 + O1); and O3/O2.
Bitumen accumulations were identified within eolic sedimentary facies of Piramboia Formation, in ... more Bitumen accumulations were identified within eolic sedimentary facies of Piramboia Formation, in the eastern margin of Parana Basin in Brazil. This basin is known to have great mineable oil sand accumulations (tar sands), with one of the 19 occurrences with amount of oil in place estimated in 6 million barrels. The compositional variability in a series of this tar sand bitumens taken from four identified eolic sedimentary facies (foreset and bottomset of dunes, dry and wet interdune) was determined by different techniques to characterize and evaluate biodegradation. Results obtained suggest that bitumens from dry interdune facies have suffered the most severe biodegradation and the bottomset facies contains the least biodegraded oil. Furthermore, some compounds (C 23 tricyclic terpane, C 29 hopane, gammacerane and C 27 diasteranes) show high resistance to microbial degradation, proving that these biomarkers can be useful to biodegradation analysis in highly biodegraded oils, such a...
Os arenitos asfalticos (tar sands) da Formacao Piramboia afloram na borda leste da Bacia do Paran... more Os arenitos asfalticos (tar sands) da Formacao Piramboia afloram na borda leste da Bacia do Parana, no centro leste do estado de Sao Paulo. Tais arenitos sao caracterizados como reservatorios exumados, os quais foram submetidos a severas condicoes que proporcionaram a aceleracao da biodegradacao do oleo e processos diageneticos. Em pesquisas de Martins, 2013 e Garcia, 2010, foram descritas respectivamente a relacao Facies x Biodegradacao e Facies x Composicao do oleo destes afloramentos. Tais parâmetros necessitam de complementos a partir de analises quimicas e petrograficas dos constituintes mineralogicos. O objetivo geral deste trabalho e realizar estudos da sedimentacao (faceis sedimentares), petrografia (mineralogia e diagenese) e petrofisica (permoporosidade), dos arenitos asfalticos da Formacao Piramboia e suas interferencias nos processos diageneticos e de biodegradacao, com intuito de auxiliar na caracterizacao de reservatorios produtores de oleos degradados. Pesquisadores d...
Abstract The Piramboia Formation tar sands constitute one remarkable occurrence of heavy oil in t... more Abstract The Piramboia Formation tar sands constitute one remarkable occurrence of heavy oil in the eastern border of the Parana Basin, Sao Paulo State, Brazil, being characterized as highly degraded oils related to the Irati-Piramboia oil system. In this context, the aim of the present work was to investigate biomarkers that are more resistant to degradation and use them to establish a more reliable geochemical correlation between the tar sand oils of the Piramboia Formation (collected from the Fazenda Betumita and Guarei I outcrops) and the organic extracts of black shales of the Irati Formation (facies Irati A and B, collected in the Amaral Machado Quarry, Sao Paulo State). For this purpose, analysis of stable carbon isotopes and diagnostic ratios of saturated and aromatic biomarkers were investigated, and the most reliable diagnostic ratios were selected based on the principal component statistical analysis. The results pointed to different degradation extent between the tar sand outcrops, being higher for the Guarei I samples. In this scenario, it was verified that most of the diagnostic ratios commonly used in oil-source rock correlation studies were susceptible to degradation processes. It was also observed that samples from Piramboia and Irati formations are at the beginning of the oil generation window, with the C29 ββ/(αα + ββ) ratio as the most suitable to assess thermal maturity of extremely degraded oils. The multivariate statistical analysis of the results, based on ten more resistant diagnostic ratios, allowed to select six main variables responsible for the similarity between the samples from the Irati and Piramboia formations: δ13C (‰), TPP ratio (C30 tetracyclic polyprenoids over diasteranes), %C28 and %C29 monoaromatic steranes, (C20 + C21)/(C23 + C24) tricyclic terpanes, and C23 tricyclic terpane/(C23 tricyclic terpane + C29 hopane). These geochemical parameters showed greater reliability in the correlation between the Piramboia Formation tar sand oils and the Irati samples of the facies A, deposited in a restricted marine environment under anoxic-euxinic conditions.
Abstract The Lower Permian Irati Formation in the northeastern and central eastern Parana Basin (... more Abstract The Lower Permian Irati Formation in the northeastern and central eastern Parana Basin (southern Brazil) was investigated in terms of bulk and molecular organic geochemistry in order to enlighten the complex depositional paleoenvironment during deposition of Irati black shales. The geochemical data reflect temporal and spatial variations of freshwater incursions promoting salinity stratification and high primary productivity in surface waters with the establishment of photic zone euxinia. Overall, highly concentrated C17 long-chain alkylnaphthalenes point to algal blooms as a result of freshwater inflows into the Irati Sea, mostly in the central eastern basin segment, and resemble concentration variations of pristane, phytane and nC17. The freshwater inflows were also retraced by increasing chroman ratios toward the top of the investigated units along with the general decrease of further palaeosalinity indicators, e.g., gammacerane, tetracyclic (C24), β-carotane, and the herein suggested γ-carotane and lexane indexes. The existence of a water column stratification promoting organic matter preservation is supported by the detection of tetrahydrophenanthrene at high concentrations, in addition to the known prominent occurrence of gammacerane. The detection of C10 to C31 aryl isoprenoids in addition to C16 and C18 pseudohomologue aryl isoprenoids points to the presence of photic zone euxinia. In general, samples from the central eastern basin were deposited in a deeper marine setting with lower salinity than samples from the northeastern basin, which displays signals of a shallower marine environment with reducing bottom water conditions, both deposited under freshwater influxes.
The n-alkylcyclohexanes are poorly evaluated in biodegradation studies of Brazilian petroleum sam... more The n-alkylcyclohexanes are poorly evaluated in biodegradation studies of Brazilian petroleum samples. In this context, this work aimed to use the homologue series of alkylcyclohexanes to assess extend of biodegradation of 26 petroleum samples from five Brazilian sedimentary basins, analyzed by gas chromatography coupled to mass spectrometry. The n-alkylcyclohexanes compounds were detected in all samples, with a distribution similar to the n-alkane profile, in which their abundance decreasing with increasing of the biodegradation extent. Based on this, it was suggested the use of the new parameter H30/DC together with the H30/AC already proposed, calculated by the ratio between C30 hopane to the dodecyl-cyclohexane, to assess biodegradation level according Peter and Moldowan scale (PM scale). In addition, it was observed an increasing in the relative abundance of DBE 2 from class O-2, analyzed by ESI(-) FT-ICR MS, mainly due to the formation of monocyclic acids with biodegradation, ...
The Ocean decade (2021–2030) for sustainable development proclaimed in 2017 by the UN, seeks to p... more The Ocean decade (2021–2030) for sustainable development proclaimed in 2017 by the UN, seeks to promote and conserve the sustainable use of oceans, seas, and marine resources. For this, the distribution of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and biomarkers, in sediments from the Fortaleza coastal zone (Mucuripe harbor (MH) e Inner shelf (ICS)) were used to assess the impacts of anthropogenic activities in the area. The concentrations of total n-alkanes (Σ16 n-alkanes) in MH and ICS sediments varied from 35.9 to 94.9 and 17.9 to 197.3 µg g− 1, respectively, while the isoprenoids phytane and pristane in MH and ICS sediments ranged from 0.1 to 1.69 ug g− 1 and from 0.14 and 1.20 µg g− 1, respectively. Most of the sediment samples presented carbon preference index (CPI) values close to unity, indicating that the area is submitted to petroleum-related sources. The concentrations of Σ16 PHAs in MH and ICS sediments varied from 87.0 to 562.0 and 98 to 288.0 ng g− 1. This w...
Abstract Physicochemical changes that occurred during deposition of Irati black shales were inves... more Abstract Physicochemical changes that occurred during deposition of Irati black shales were investigated via outcrop samples collected in the northeastern and central-eastern Parana Basin. Various traditional geochemical indicators were used, in addition to newly detected biomarkers: C32 lanostane, simonellite, sempervirane, and C32–C35 benzohopanes. Bulk geochemistry parameters, mineralogy, and conventional saturated biomarkers, such as tetracyclic polyprenoids (TPPs), reflect restricted and hypersaline marine deposition with freshwater input and increased terrigenous contribution toward the top of the studied outcrops. This led to stratification of the water column, establishing euxinic conditions in the photic zone and reducing conditions at the bottom of the water column, which enhanced preservation of organic matter. Principal component and hierarchical cluster analyses were performed to group the samples according to their similar geochemical characteristics: prevailing marine environment (basal outcrop samples) and higher freshwater inflow with greater terrigenous contribution (top outcrop samples). These geochemical observations were corroborated by aromatic biomarkers such as triaromatic steroids, trimethylnaphthalenes, simonellite, and sempervirane. The aryl isoprenoid ratio (AIR) indicates persistence of photic zone euxinia (PZE) during Irati black shale deposition. The presence of C32 lanostane and C32–C35 benzohopanes is directly related to the hypersaline depositional environment of the analyzed samples. Finally, the C32-33/C32-35 benzohopane ratio is proposed as a thermal maturity proxy because variations in the ratio can be linked to the presence of a diabase sill and temperature catalyst minerals near one of the outcrops.
To comprehensively understand the chemical changes over time of spilled oils subject to tropical ... more To comprehensively understand the chemical changes over time of spilled oils subject to tropical climate conditions and the active weathering processes, a spill simulation experiment was conducted along 210 days with two distinct Brazilian oils (19 and 24 API) under irradiation and non-irradiation of sunlight. Isoprenoids and n-alkanes showed a great loss after 40 days for both oils under the two conditions due to evaporation. Diagnostic ratios of saturated biomarkers showed no changes, whereas the polycyclic aromatic hydrocarbons had a decreasing concentration under both conditions mainly due to evaporation. Furthermore, oxygenated polar compounds produced by photooxidation were investigated by ESI(-) FT-ICR MS and showed changes only for the oils exposed to sunlight irradiation. Based on the observed polar compositional changes, new parameters are suggested using heteroatom classes to estimate oil spill time under tropical conditions: NO3/NO2; NO3/(NO + NO2); ∑NOx/N1; (O4 + O3)/(O2 + O1); O4/(O2 + O1); and O3/O2.
Bitumen accumulations were identified within eolic sedimentary facies of Piramboia Formation, in ... more Bitumen accumulations were identified within eolic sedimentary facies of Piramboia Formation, in the eastern margin of Parana Basin in Brazil. This basin is known to have great mineable oil sand accumulations (tar sands), with one of the 19 occurrences with amount of oil in place estimated in 6 million barrels. The compositional variability in a series of this tar sand bitumens taken from four identified eolic sedimentary facies (foreset and bottomset of dunes, dry and wet interdune) was determined by different techniques to characterize and evaluate biodegradation. Results obtained suggest that bitumens from dry interdune facies have suffered the most severe biodegradation and the bottomset facies contains the least biodegraded oil. Furthermore, some compounds (C 23 tricyclic terpane, C 29 hopane, gammacerane and C 27 diasteranes) show high resistance to microbial degradation, proving that these biomarkers can be useful to biodegradation analysis in highly biodegraded oils, such a...
Os arenitos asfalticos (tar sands) da Formacao Piramboia afloram na borda leste da Bacia do Paran... more Os arenitos asfalticos (tar sands) da Formacao Piramboia afloram na borda leste da Bacia do Parana, no centro leste do estado de Sao Paulo. Tais arenitos sao caracterizados como reservatorios exumados, os quais foram submetidos a severas condicoes que proporcionaram a aceleracao da biodegradacao do oleo e processos diageneticos. Em pesquisas de Martins, 2013 e Garcia, 2010, foram descritas respectivamente a relacao Facies x Biodegradacao e Facies x Composicao do oleo destes afloramentos. Tais parâmetros necessitam de complementos a partir de analises quimicas e petrograficas dos constituintes mineralogicos. O objetivo geral deste trabalho e realizar estudos da sedimentacao (faceis sedimentares), petrografia (mineralogia e diagenese) e petrofisica (permoporosidade), dos arenitos asfalticos da Formacao Piramboia e suas interferencias nos processos diageneticos e de biodegradacao, com intuito de auxiliar na caracterizacao de reservatorios produtores de oleos degradados. Pesquisadores d...
Abstract The Piramboia Formation tar sands constitute one remarkable occurrence of heavy oil in t... more Abstract The Piramboia Formation tar sands constitute one remarkable occurrence of heavy oil in the eastern border of the Parana Basin, Sao Paulo State, Brazil, being characterized as highly degraded oils related to the Irati-Piramboia oil system. In this context, the aim of the present work was to investigate biomarkers that are more resistant to degradation and use them to establish a more reliable geochemical correlation between the tar sand oils of the Piramboia Formation (collected from the Fazenda Betumita and Guarei I outcrops) and the organic extracts of black shales of the Irati Formation (facies Irati A and B, collected in the Amaral Machado Quarry, Sao Paulo State). For this purpose, analysis of stable carbon isotopes and diagnostic ratios of saturated and aromatic biomarkers were investigated, and the most reliable diagnostic ratios were selected based on the principal component statistical analysis. The results pointed to different degradation extent between the tar sand outcrops, being higher for the Guarei I samples. In this scenario, it was verified that most of the diagnostic ratios commonly used in oil-source rock correlation studies were susceptible to degradation processes. It was also observed that samples from Piramboia and Irati formations are at the beginning of the oil generation window, with the C29 ββ/(αα + ββ) ratio as the most suitable to assess thermal maturity of extremely degraded oils. The multivariate statistical analysis of the results, based on ten more resistant diagnostic ratios, allowed to select six main variables responsible for the similarity between the samples from the Irati and Piramboia formations: δ13C (‰), TPP ratio (C30 tetracyclic polyprenoids over diasteranes), %C28 and %C29 monoaromatic steranes, (C20 + C21)/(C23 + C24) tricyclic terpanes, and C23 tricyclic terpane/(C23 tricyclic terpane + C29 hopane). These geochemical parameters showed greater reliability in the correlation between the Piramboia Formation tar sand oils and the Irati samples of the facies A, deposited in a restricted marine environment under anoxic-euxinic conditions.
Abstract The Lower Permian Irati Formation in the northeastern and central eastern Parana Basin (... more Abstract The Lower Permian Irati Formation in the northeastern and central eastern Parana Basin (southern Brazil) was investigated in terms of bulk and molecular organic geochemistry in order to enlighten the complex depositional paleoenvironment during deposition of Irati black shales. The geochemical data reflect temporal and spatial variations of freshwater incursions promoting salinity stratification and high primary productivity in surface waters with the establishment of photic zone euxinia. Overall, highly concentrated C17 long-chain alkylnaphthalenes point to algal blooms as a result of freshwater inflows into the Irati Sea, mostly in the central eastern basin segment, and resemble concentration variations of pristane, phytane and nC17. The freshwater inflows were also retraced by increasing chroman ratios toward the top of the investigated units along with the general decrease of further palaeosalinity indicators, e.g., gammacerane, tetracyclic (C24), β-carotane, and the herein suggested γ-carotane and lexane indexes. The existence of a water column stratification promoting organic matter preservation is supported by the detection of tetrahydrophenanthrene at high concentrations, in addition to the known prominent occurrence of gammacerane. The detection of C10 to C31 aryl isoprenoids in addition to C16 and C18 pseudohomologue aryl isoprenoids points to the presence of photic zone euxinia. In general, samples from the central eastern basin were deposited in a deeper marine setting with lower salinity than samples from the northeastern basin, which displays signals of a shallower marine environment with reducing bottom water conditions, both deposited under freshwater influxes.
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