ABSTRACT Abiotic organic chemistry in hydrothermal systems is of interest to biologists, geochemi... more ABSTRACT Abiotic organic chemistry in hydrothermal systems is of interest to biologists, geochemists and oceanographers. This chemistry consists of thermal alteration of organic matter and minor prebiotic synthesis of organic compounds. Thermal alteration has been extensively documented to yield petroleum and heavy bitumen products from contemporary organic detritus. Carbon dioxide, carbon monoxide, ammonia and sulfur species have been used as precursors in prebiotic synthesis experiments to organic compounds. These inorganic species are common components of hot spring gases and marine hydrothermal systems. It is of interest to further test their reactivities in reductive aqueous thermolysis. We have synthesized organic compounds (lipids) in aqueous solutions of oxalic acid, and with carbon disulfide or ammonium bicarbonate at temperatures from 175-400° C. The synthetic lipids from oxalic acid solutions consisted of n-alkanols, n-alkanoic acids, n-alkyl formates, n-alkanones, n-alkenes and n-alkanes, typically to C30 with no carbon number preferences. The products from CS2 in acidic aqueous solutions yielded cyclic thioalkanes, alkyl polysulfides, and thioesters with other numerous minor compounds. The synthesis products from oxalic acid and ammonium bicarbonate solutions were homologous series of n-alkyl amides, n-alkyl amines, n-alkanes and n-alkanoic acids, also to C30 with no carbon number predominance. Condensation (dehydration) reactions also occur under elevated temperatures in aqueous medium as tested by model reactions to form amide, ester and nitrile bonds. It is concluded that the abiotic formation of aliphatic lipids, condensation products (amides, esters, nitriles, and CS2 derivatives (alkyl polysulfides, cyclic polysulfides) is possible under hydrothermal conditions and warrants further studies.
Abstract: Samples of air particulate matter (PM) were collected for the determination of chemical... more Abstract: Samples of air particulate matter (PM) were collected for the determination of chemical elements from June 2006 to May 2007. PM samples were taken in two size modes (PM2.5 and PM10) using MiniVolume air samplers on rooftops of various buildings (15-25 m above ground) in the city of Riyadh. The samples were subjected to XRF analysis to determine both
ABSTRACT Understanding the physical and chemical conditions that lead to the formation and preser... more ABSTRACT Understanding the physical and chemical conditions that lead to the formation and preservation of barite in marine environment is important to validate the application of barium/barite abundance in ocean sediments as an index of productivity. In this work we rely on time-series sediment trap results to explore: (1) barium and strontium concentration variations; (2) the changes in the degree of saturations with respect to barite and celestite; and (3) the equilibrium relationship between barite and celestite in seawater cup solutions in order to investigate the formation of "natural" marine barite as the mixed solid phase BaxSr1-xSO4. The data were collected along 170W between Subtropical Front and Ross Sea from November 1996 to January 1997, as part of the U.S. Joint Global Ocean Flux Study (USJGOFS-AESOPS) to study the Southern Ocean impact on biogeochemical processes of the oceans. High concentrations of barium and strontium were measured in the cup solutions of sediment traps during the high particle flux periods. The cup solutions of the sediment traps were estimated to be supersaturated with respect to pure barite between 100% and over 900%. They were undersaturated to slightly supersaturated with respect to celestite, ranging between 14 and 150%. The modeled equilibrium relationship of a mixed solid phase of barite and celestite in solution has indicated that barite with up to 23% mole fraction of SrSO4(s) might form in these cup solutions. The Sr/Ba ratios in the bulk solid phases collected from the same sediment trap cups were much higher (25-99%) than modeled values and are likely controlled by non-sulphate solids. These results also suggest that the precipitation of marine barite crystals is not favorable in these cup solutions due to the high solubility of high strontian barite. If the cup solutions can approximate the isolated chemical environment within particle aggregates collected by these traps, then it is unlikely that significant precipitation of marine barite occurs during their transport to the seafloor.
Soil and sand fine particles, which may be resuspended as fine dust in the atmosphere, contain a ... more Soil and sand fine particles, which may be resuspended as fine dust in the atmosphere, contain a variety of anthropogenic and natural organic components. Samples of fine soil and sand particles (sieved to <125 lM) were collected from the Riyadh area in the summer of 2003 and extracted with a mixture of dichloromethane and methanol (3:1, v:v). The derivatized total extracts were analyzed by gas chromatography-mass spectrometry in order to characterize the composition and sources of the organic components. Both anthropogenic and natural biogenic inputs were the major sources of the organic compounds in these extracts. Discarded plastics and vehicular emission products were the major anthropogenic sources in the fine particles from populated areas of the city. Their tracers were plasticizers, UCM, n-alkanes, hopanes and traces of steranes. Vegetation was the major natural source of organic compounds in samples from outside Riyadh and included n-alkanols, n-alkanoic acids, nalkanes, methyl alkanoates, sterols and triterpenoids. Carbohydrates had high concentrations (42-54%) in all samples and indicate sources from decomposition of cellulose and/or the presence of viable microbiota such as bacteria and fungi. The results were also compared with the data obtained in winter 2002 and showed that anthropogenic inputs were higher in summer than in winter, whereas the opposite trend was observed for natural inputs.
Ecology, Environment and Conservation, May 31, 2022
Aliphatic hydrocarbon n-alkanes, pristane (Pr), and phytane (Ph) were determined in the tissues o... more Aliphatic hydrocarbon n-alkanes, pristane (Pr), and phytane (Ph) were determined in the tissues of six economic freshwater fish species (Luciobarbus xanthopterus, Ctenophyngodon idella, Cyprinus carpio, Tilapia zillii, Palaniza abu, and Leuciscus vorax) collected from the Shatt Al-Arab river. They were analyzed by capillary gas chromatography-flame ionization detector (GC-FID). The carbon chain lengths of n-alkanes in the fish tissue samples ranged from nC 13 to nC 36. The highest concentration of the total n-alkanes was detected in the filter feeder P. abu tissue (23.14µg/g dry weight) and the lowest concentration was in the omnivorous C. carpio tissue (3.76 µg/g dry weight). The major sources of the n-alkanes, pristanes, and phytanes were from petroleum hydrocarbons based on the results of the molecular biomarker indices and the ratios of CPI (carbon preference index), Pr/Ph, LMW/HMW (total nC 13-C 24 /total nC 25-nC 36), nC 17 /Pr, and nC 18 /Ph. The percentage of n-alkanes from petroleum related-products ranged from 83.2% to 94.8%, whereas the natural biogenic sources were in the order of bacterial (3.7-11.7%) > higher plant wax (0.0-9.1%) > algal (0.1-1.2%) sources. The occasion of high fractions of n-alkanes and isoprenoids from petroleum hydrocarbons in these fish tissues indicated that the foster habitats were highly contaminated by crude oil. Further studies are required to investigate the bioaccumulation of other anthropogenic contaminants such as plasticizers, pesticides, and polycyclic aromatic hydrocarbons freshwater organisms.
Surface sediment samples from Obhur Lagoon on the Red Sea coast of Saudi Arabia were collected an... more Surface sediment samples from Obhur Lagoon on the Red Sea coast of Saudi Arabia were collected and analyzed to determine the levels, distribution and sources of hydrocarbon compounds. The sediments were collected using a Van Veen grab sampler, dried, extracted with a mixture of dichloromethane/methanol, and analyzed by gas chromatography-mass spectrometry. The major hydrocarbons of these lipid extracts included n-alkanes (6–645 ng g−1), methyl n-alkanoates (1–311 ng g−1), hopanes (3–219 ng g−1), steranes (5–258 ng g−1), phthalates (4–201 ng g−1), and an unresolved complex mixture (UCM) (0–4571 μg g−1). Anthropogenic petroleum products and plasticizers were the main sources of these hydrocarbons, with lesser amounts from biogenic sources, including natural waxes of terrestrial higher plants and marine microbial detritus. The estimated anthropogenic inputs of the total lipid hydrocarbons for all sediments ranged from 14 to 98% for petroleum products and from 2 to 18% for plasticizers, whereas biogenic inputs ranged from 0 to 10.7% for terrestrial higher plant waxes and from 0 to 68.5% for marine microbial detritus. The presence and inputs of petroleum residues and plasticizers to the coastal sediments of the lagoon likely affect the marine ecosystems and associated species groups that use the lagoon as a coastal nursery and spawning area.
ABSTRACT Hydrothermal simulation experiments were performed with contemporary sediments from Lake... more ABSTRACT Hydrothermal simulation experiments were performed with contemporary sediments from Lake Chapala to assess the source of the lake tars. The precursor-product relationships of the organic compounds were determined for the source sediments and their hydrous pyrolysis products. The pyrolysis products contained major unresolved complex mixtures of branched and cyclic hydrocarbons, low amounts of n-alkanes, dinosterane, gammacerane, and immature and mature hopane biomarkers derived from lacustrine biomass sources. The results support the proposal that the tar manifestations in the lake are not biodegraded petroleum, but were hydrothermally generated from lacustrine organic matter at temperatures not exceeding about 250 °C over brief geological times.
h i g h l i g h t s " We used hydrous pyrolysis to study alteration products of sewage sludge (SS... more h i g h l i g h t s " We used hydrous pyrolysis to study alteration products of sewage sludge (SS) OM. " Two sets of experiments were conducted at T = 200-350°C for 48 h. " The first set included only SS and water and the second with oxalic acid (OA). " The yields and alteration products increased with temperature and presence of OA. " The results show that the yields are higher under reductive hydrous pyrolysis.
... 2006, 2008) or mid-ocean spreading centers (Holm and Charlou 2001; Kelley and Früh-Green 1999... more ... 2006, 2008) or mid-ocean spreading centers (Holm and Charlou 2001; Kelley and Früh-Green 1999) also appear to have formed in the absence ... These temperatures are commonly encountered in seafloor hydrothermal systems or during low grade metamorphism (Lindsay et al ...
Sediment samples from the coastal zone of the Gulf of Suez contain a variety of organic compounds... more Sediment samples from the coastal zone of the Gulf of Suez contain a variety of organic compounds from anthropogenic and natural sources. A total of 12 surface samples of bottom sediments were collected with an Ekman grab sampler along an offshore transect south of Ras Abu el-Darag. The samples were extracted with a mixture of dichloromethane and methanol (3:1 v/v) after drying and sieving through 250 lm mesh. The extracts were derivatized and analyzed by gas chromatographymass spectrometry in order to characterize the chemical composition and sources of the organic components. Marine with minor terrestrial biota were the major natural sources of organic tracers and included n-alkanoic acids, sterols and saccharides (5.7-76.7%). Anthropogenic sources, from petroleum related activities, detergent usage for spill cleaning and littering, are indicated by the presence of n-alkanes with carbon preference index B1.0, hopanes, steranes, unresolved complex mixture of branched and cyclic hydrocarbons, alkyl nitriles, alkamides and plasticizers. Their total relative concentrations ranged from 23.3 to 97.3% of the total extracts. Petroleum residues from natural seepage may also be part of these hydrocarbons. The levels of anthropogenic inputs decrease from about 94% in coastal zone sediments to about 20% in sediments from the reef front.
This chapter discusses the various input sources of extractable organic matter (EOM) compounds to... more This chapter discusses the various input sources of extractable organic matter (EOM) compounds to the Red Sea. These are based on geochemical analyses of atmospheric dust, surface seawater particulate matter and sediment samples collected from the Gulf of Aqaba and the coasts of the Gulf of Suez, Saudi Arabia and Yemen. The samples were extracted with a dichloromethane/methanol mixture and analyzed by gas chromatography-mass spectrometry (GC-MS). The EOM compounds (lipids) in the samples are diverse and include n-alkanes, n-alkanoic acids, n-alkanols, methyl n-alkanoates, steroids, petroleum hydrocarbons and plasticizers. The steroids and n-alkanoic acids were major components of the surface seawater particulate matter samples, whereas petroleum hydrocarbons were major compounds in coastal sediments. Based on the results of the different samples, the main input sources of these lipids were from: (1) natural autochthonous microbiota (plankton and bacteria) as indicated by the presence of cholesterol and brassicasterol in the different surface seawater particulate matter and sediment samples; (2) natural allochthonous material origins from terrestrial plant detritus transported by dust as shown by the distributions of n-alkanoic acids, n-alkanols and phytosterols; and (3) anthropogenic sources (mainly petroleum) from regional oil production activities, oil tankers or shipping activities as revealed by the n-alkane distribution pattern and the presence of an unresolved complex mixture (UCM) of branched and cyclic hydrocarbons, with hopane and sterane biomarkers. Future studies of the organic and inorganic biogeochemistry on the water column, coastal areas and dust transported to the Red Sea are needed to characterize the various regional sources, transformation, and diagenetic processes of the organic matter en route to this marine environment.
Environmental Monitoring and Assessment, Jun 7, 2006
Fine particles in the atmosphere from soil and sand resuspension contain a variety of organic com... more Fine particles in the atmosphere from soil and sand resuspension contain a variety of organic compounds from natural biogenic and anthropogenic matter. Soil and sand samples from various sites near Kuwait city were collected, sieved to retain the fine particles, and extracted with a mixture of dichloromethane and methanol. The extracts were derivatized and analyzed by gas chromatography-mass spectrometry in order to characterize the chemical compositions and sources of the organic components. The major inputs of organic compounds were from both natural biogenic and anthropogenic sources in these samples. Vegetation was the major natural source of organic compounds and included n-alkanols, n-alkanoic acids, n-alkanes, sterols and triterpenoids. Saccharides had high concentrations (31-43%) in the sand dune and seafront samples, indicating sources from decomposed vegation materials and/or the presence of viable microbiota such as bacteria and fungi. Vehicular emission products, leakage of lubricating oils, discarded plastics and emissions from cooking operations were the major anthropogenic inputs in the samples from the urban areas. This input was mainly UCM, n-alkanes, hopanes, plasticizers and cholesterol, respectively.
ABSTRACT Abiotic organic chemistry in hydrothermal systems is of interest to biologists, geochemi... more ABSTRACT Abiotic organic chemistry in hydrothermal systems is of interest to biologists, geochemists and oceanographers. This chemistry consists of thermal alteration of organic matter and minor prebiotic synthesis of organic compounds. Thermal alteration has been extensively documented to yield petroleum and heavy bitumen products from contemporary organic detritus. Carbon dioxide, carbon monoxide, ammonia and sulfur species have been used as precursors in prebiotic synthesis experiments to organic compounds. These inorganic species are common components of hot spring gases and marine hydrothermal systems. It is of interest to further test their reactivities in reductive aqueous thermolysis. We have synthesized organic compounds (lipids) in aqueous solutions of oxalic acid, and with carbon disulfide or ammonium bicarbonate at temperatures from 175-400° C. The synthetic lipids from oxalic acid solutions consisted of n-alkanols, n-alkanoic acids, n-alkyl formates, n-alkanones, n-alkenes and n-alkanes, typically to C30 with no carbon number preferences. The products from CS2 in acidic aqueous solutions yielded cyclic thioalkanes, alkyl polysulfides, and thioesters with other numerous minor compounds. The synthesis products from oxalic acid and ammonium bicarbonate solutions were homologous series of n-alkyl amides, n-alkyl amines, n-alkanes and n-alkanoic acids, also to C30 with no carbon number predominance. Condensation (dehydration) reactions also occur under elevated temperatures in aqueous medium as tested by model reactions to form amide, ester and nitrile bonds. It is concluded that the abiotic formation of aliphatic lipids, condensation products (amides, esters, nitriles, and CS2 derivatives (alkyl polysulfides, cyclic polysulfides) is possible under hydrothermal conditions and warrants further studies.
Abstract: Samples of air particulate matter (PM) were collected for the determination of chemical... more Abstract: Samples of air particulate matter (PM) were collected for the determination of chemical elements from June 2006 to May 2007. PM samples were taken in two size modes (PM2.5 and PM10) using MiniVolume air samplers on rooftops of various buildings (15-25 m above ground) in the city of Riyadh. The samples were subjected to XRF analysis to determine both
ABSTRACT Understanding the physical and chemical conditions that lead to the formation and preser... more ABSTRACT Understanding the physical and chemical conditions that lead to the formation and preservation of barite in marine environment is important to validate the application of barium/barite abundance in ocean sediments as an index of productivity. In this work we rely on time-series sediment trap results to explore: (1) barium and strontium concentration variations; (2) the changes in the degree of saturations with respect to barite and celestite; and (3) the equilibrium relationship between barite and celestite in seawater cup solutions in order to investigate the formation of &quot;natural&quot; marine barite as the mixed solid phase BaxSr1-xSO4. The data were collected along 170W between Subtropical Front and Ross Sea from November 1996 to January 1997, as part of the U.S. Joint Global Ocean Flux Study (USJGOFS-AESOPS) to study the Southern Ocean impact on biogeochemical processes of the oceans. High concentrations of barium and strontium were measured in the cup solutions of sediment traps during the high particle flux periods. The cup solutions of the sediment traps were estimated to be supersaturated with respect to pure barite between 100% and over 900%. They were undersaturated to slightly supersaturated with respect to celestite, ranging between 14 and 150%. The modeled equilibrium relationship of a mixed solid phase of barite and celestite in solution has indicated that barite with up to 23% mole fraction of SrSO4(s) might form in these cup solutions. The Sr/Ba ratios in the bulk solid phases collected from the same sediment trap cups were much higher (25-99%) than modeled values and are likely controlled by non-sulphate solids. These results also suggest that the precipitation of marine barite crystals is not favorable in these cup solutions due to the high solubility of high strontian barite. If the cup solutions can approximate the isolated chemical environment within particle aggregates collected by these traps, then it is unlikely that significant precipitation of marine barite occurs during their transport to the seafloor.
Soil and sand fine particles, which may be resuspended as fine dust in the atmosphere, contain a ... more Soil and sand fine particles, which may be resuspended as fine dust in the atmosphere, contain a variety of anthropogenic and natural organic components. Samples of fine soil and sand particles (sieved to <125 lM) were collected from the Riyadh area in the summer of 2003 and extracted with a mixture of dichloromethane and methanol (3:1, v:v). The derivatized total extracts were analyzed by gas chromatography-mass spectrometry in order to characterize the composition and sources of the organic components. Both anthropogenic and natural biogenic inputs were the major sources of the organic compounds in these extracts. Discarded plastics and vehicular emission products were the major anthropogenic sources in the fine particles from populated areas of the city. Their tracers were plasticizers, UCM, n-alkanes, hopanes and traces of steranes. Vegetation was the major natural source of organic compounds in samples from outside Riyadh and included n-alkanols, n-alkanoic acids, nalkanes, methyl alkanoates, sterols and triterpenoids. Carbohydrates had high concentrations (42-54%) in all samples and indicate sources from decomposition of cellulose and/or the presence of viable microbiota such as bacteria and fungi. The results were also compared with the data obtained in winter 2002 and showed that anthropogenic inputs were higher in summer than in winter, whereas the opposite trend was observed for natural inputs.
Ecology, Environment and Conservation, May 31, 2022
Aliphatic hydrocarbon n-alkanes, pristane (Pr), and phytane (Ph) were determined in the tissues o... more Aliphatic hydrocarbon n-alkanes, pristane (Pr), and phytane (Ph) were determined in the tissues of six economic freshwater fish species (Luciobarbus xanthopterus, Ctenophyngodon idella, Cyprinus carpio, Tilapia zillii, Palaniza abu, and Leuciscus vorax) collected from the Shatt Al-Arab river. They were analyzed by capillary gas chromatography-flame ionization detector (GC-FID). The carbon chain lengths of n-alkanes in the fish tissue samples ranged from nC 13 to nC 36. The highest concentration of the total n-alkanes was detected in the filter feeder P. abu tissue (23.14µg/g dry weight) and the lowest concentration was in the omnivorous C. carpio tissue (3.76 µg/g dry weight). The major sources of the n-alkanes, pristanes, and phytanes were from petroleum hydrocarbons based on the results of the molecular biomarker indices and the ratios of CPI (carbon preference index), Pr/Ph, LMW/HMW (total nC 13-C 24 /total nC 25-nC 36), nC 17 /Pr, and nC 18 /Ph. The percentage of n-alkanes from petroleum related-products ranged from 83.2% to 94.8%, whereas the natural biogenic sources were in the order of bacterial (3.7-11.7%) > higher plant wax (0.0-9.1%) > algal (0.1-1.2%) sources. The occasion of high fractions of n-alkanes and isoprenoids from petroleum hydrocarbons in these fish tissues indicated that the foster habitats were highly contaminated by crude oil. Further studies are required to investigate the bioaccumulation of other anthropogenic contaminants such as plasticizers, pesticides, and polycyclic aromatic hydrocarbons freshwater organisms.
Surface sediment samples from Obhur Lagoon on the Red Sea coast of Saudi Arabia were collected an... more Surface sediment samples from Obhur Lagoon on the Red Sea coast of Saudi Arabia were collected and analyzed to determine the levels, distribution and sources of hydrocarbon compounds. The sediments were collected using a Van Veen grab sampler, dried, extracted with a mixture of dichloromethane/methanol, and analyzed by gas chromatography-mass spectrometry. The major hydrocarbons of these lipid extracts included n-alkanes (6–645 ng g−1), methyl n-alkanoates (1–311 ng g−1), hopanes (3–219 ng g−1), steranes (5–258 ng g−1), phthalates (4–201 ng g−1), and an unresolved complex mixture (UCM) (0–4571 μg g−1). Anthropogenic petroleum products and plasticizers were the main sources of these hydrocarbons, with lesser amounts from biogenic sources, including natural waxes of terrestrial higher plants and marine microbial detritus. The estimated anthropogenic inputs of the total lipid hydrocarbons for all sediments ranged from 14 to 98% for petroleum products and from 2 to 18% for plasticizers, whereas biogenic inputs ranged from 0 to 10.7% for terrestrial higher plant waxes and from 0 to 68.5% for marine microbial detritus. The presence and inputs of petroleum residues and plasticizers to the coastal sediments of the lagoon likely affect the marine ecosystems and associated species groups that use the lagoon as a coastal nursery and spawning area.
ABSTRACT Hydrothermal simulation experiments were performed with contemporary sediments from Lake... more ABSTRACT Hydrothermal simulation experiments were performed with contemporary sediments from Lake Chapala to assess the source of the lake tars. The precursor-product relationships of the organic compounds were determined for the source sediments and their hydrous pyrolysis products. The pyrolysis products contained major unresolved complex mixtures of branched and cyclic hydrocarbons, low amounts of n-alkanes, dinosterane, gammacerane, and immature and mature hopane biomarkers derived from lacustrine biomass sources. The results support the proposal that the tar manifestations in the lake are not biodegraded petroleum, but were hydrothermally generated from lacustrine organic matter at temperatures not exceeding about 250 °C over brief geological times.
h i g h l i g h t s " We used hydrous pyrolysis to study alteration products of sewage sludge (SS... more h i g h l i g h t s " We used hydrous pyrolysis to study alteration products of sewage sludge (SS) OM. " Two sets of experiments were conducted at T = 200-350°C for 48 h. " The first set included only SS and water and the second with oxalic acid (OA). " The yields and alteration products increased with temperature and presence of OA. " The results show that the yields are higher under reductive hydrous pyrolysis.
... 2006, 2008) or mid-ocean spreading centers (Holm and Charlou 2001; Kelley and Früh-Green 1999... more ... 2006, 2008) or mid-ocean spreading centers (Holm and Charlou 2001; Kelley and Früh-Green 1999) also appear to have formed in the absence ... These temperatures are commonly encountered in seafloor hydrothermal systems or during low grade metamorphism (Lindsay et al ...
Sediment samples from the coastal zone of the Gulf of Suez contain a variety of organic compounds... more Sediment samples from the coastal zone of the Gulf of Suez contain a variety of organic compounds from anthropogenic and natural sources. A total of 12 surface samples of bottom sediments were collected with an Ekman grab sampler along an offshore transect south of Ras Abu el-Darag. The samples were extracted with a mixture of dichloromethane and methanol (3:1 v/v) after drying and sieving through 250 lm mesh. The extracts were derivatized and analyzed by gas chromatographymass spectrometry in order to characterize the chemical composition and sources of the organic components. Marine with minor terrestrial biota were the major natural sources of organic tracers and included n-alkanoic acids, sterols and saccharides (5.7-76.7%). Anthropogenic sources, from petroleum related activities, detergent usage for spill cleaning and littering, are indicated by the presence of n-alkanes with carbon preference index B1.0, hopanes, steranes, unresolved complex mixture of branched and cyclic hydrocarbons, alkyl nitriles, alkamides and plasticizers. Their total relative concentrations ranged from 23.3 to 97.3% of the total extracts. Petroleum residues from natural seepage may also be part of these hydrocarbons. The levels of anthropogenic inputs decrease from about 94% in coastal zone sediments to about 20% in sediments from the reef front.
This chapter discusses the various input sources of extractable organic matter (EOM) compounds to... more This chapter discusses the various input sources of extractable organic matter (EOM) compounds to the Red Sea. These are based on geochemical analyses of atmospheric dust, surface seawater particulate matter and sediment samples collected from the Gulf of Aqaba and the coasts of the Gulf of Suez, Saudi Arabia and Yemen. The samples were extracted with a dichloromethane/methanol mixture and analyzed by gas chromatography-mass spectrometry (GC-MS). The EOM compounds (lipids) in the samples are diverse and include n-alkanes, n-alkanoic acids, n-alkanols, methyl n-alkanoates, steroids, petroleum hydrocarbons and plasticizers. The steroids and n-alkanoic acids were major components of the surface seawater particulate matter samples, whereas petroleum hydrocarbons were major compounds in coastal sediments. Based on the results of the different samples, the main input sources of these lipids were from: (1) natural autochthonous microbiota (plankton and bacteria) as indicated by the presence of cholesterol and brassicasterol in the different surface seawater particulate matter and sediment samples; (2) natural allochthonous material origins from terrestrial plant detritus transported by dust as shown by the distributions of n-alkanoic acids, n-alkanols and phytosterols; and (3) anthropogenic sources (mainly petroleum) from regional oil production activities, oil tankers or shipping activities as revealed by the n-alkane distribution pattern and the presence of an unresolved complex mixture (UCM) of branched and cyclic hydrocarbons, with hopane and sterane biomarkers. Future studies of the organic and inorganic biogeochemistry on the water column, coastal areas and dust transported to the Red Sea are needed to characterize the various regional sources, transformation, and diagenetic processes of the organic matter en route to this marine environment.
Environmental Monitoring and Assessment, Jun 7, 2006
Fine particles in the atmosphere from soil and sand resuspension contain a variety of organic com... more Fine particles in the atmosphere from soil and sand resuspension contain a variety of organic compounds from natural biogenic and anthropogenic matter. Soil and sand samples from various sites near Kuwait city were collected, sieved to retain the fine particles, and extracted with a mixture of dichloromethane and methanol. The extracts were derivatized and analyzed by gas chromatography-mass spectrometry in order to characterize the chemical compositions and sources of the organic components. The major inputs of organic compounds were from both natural biogenic and anthropogenic sources in these samples. Vegetation was the major natural source of organic compounds and included n-alkanols, n-alkanoic acids, n-alkanes, sterols and triterpenoids. Saccharides had high concentrations (31-43%) in the sand dune and seafront samples, indicating sources from decomposed vegation materials and/or the presence of viable microbiota such as bacteria and fungi. Vehicular emission products, leakage of lubricating oils, discarded plastics and emissions from cooking operations were the major anthropogenic inputs in the samples from the urban areas. This input was mainly UCM, n-alkanes, hopanes, plasticizers and cholesterol, respectively.
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