Concentrations Of N-alkanes Research Articles

Hydrocarbon composition and concentrations in the Gulf of Mexico sediments in the 3 years following the Macondo well blowout

In April of 2010, the Macondo well blowout in the northern Gulf of Mexico resulted in an unprecedented release of oil into the water column at a depth of approximately 1500 m. A time series of surface and subsurface sediment samples were collected to the northwest of the well from 2010 to 2013 for molecular biomarker and bulk carbon isotopic analyses. While no clear trend was observed in subsurface sediments, surface sediments (0–3 cm) showed a clear pattern with total concentrations of n-alkanes, unresolved complex mixture (UCM), and petroleum biomarkers (terpanes, hopanes, steranes) increasing from May to September 2010, peaking in late November 2010, and strongly decreasing in the subsequent years. The peak in hydrocarbon concentrations were corroborated by higher organic carbon contents, more depleted Δ14C values and biomarker ratios similar to those of the initial MC252 crude oil reported in the literature. These results indicate that at least part of oil discharged from the accident sedimented to the seafloor in subsequent months, resulting in an apparent accumulation of hydrocarbons on the seabed by the end of 2010. Sediment resuspension and transport or biodegradation may account for the decrease in sedimented oil quantities in the years following the Macondo well spill.

Assessment of Aliphatic Hydrocarbons in Sediments of Shatt Al-Arab River, Southern Iraq, North East Arabian Gulf

Shatt Al-Arab River is one of the important rivers for water supply, industry and irrigation in Basrah City, south of Iraq. It's also supply drinking water to users in the region. Despite the significance of this river, there is a lack of previous studies dealing with petroleum pollution especially for geochemical studies of organic matter in the river sediments using molecular tracer methods. Therefore, the identification and quantification of petroleum hydrocarbons in this river at the elemental and molecular levels will be of the utmost interest. Sediments were analyzed in nine Shatt Al-Arab River stations. Texture was silty clay or silty sand. TOC and TN ranged from 0.39-0.90 and 0.02-0.16%. OM varied from 17.43-34.36 µg g-1 dw, representing 0.27-0.87% of TOC. AHs ranged from 3.19-10.27 µg g-1 dw and constituted 16.07-29.88% of OM. Total n-alkanes concentrations ranged from 0.08-42.58 µg g-1 dw with carbon numbers from C11-C34 were identified. N-alkanes content was relatively moderate compared to sites contaminated with oil worldwide. Dominance of even carbon number n-alkanes (C11-C20) with CPI and LMW/HMW values close to unity, indicated to oil-related n-alkanes. This was verified by the values of U/R (1.27-2.45), pri/phy (0.82-1.00), C17/pri (0.70-1.94) and C18/phy (0.95-1.56) ratios and the presence of UCM. Biogenic contributions were detected within the n-alkanes distribution of C17-C31 and CPI and LMW/HMW values of <1 that mainly related to terrestrial plants, phytoplankton, algae and bacteria sources, confirmed by TAR (0.79-2.15) and C31/C19 ratio (0.28-1.62) values. However, the contribution from biogenic hydrocarbons is overshadowed by petroleum origin n-alkanes. This was obvious by the presence of UCM. PCA showed concordant results with n-alkanes ratios indicating mixed n-alkanes sources in sediments. Hopanes and steranes in sediments displayed similar signatures that were characteristic of mature organic matter contribution from oil contaminations.

Multi-proxy evidence for decreased terrestrial contribution to sedimentary organic matter in coastal areas of the East China Sea during the past 100 years

Little is known about temporal changes in sedimentary organic matter (OM) in the East China Sea (ECS) due to the lack of continuous high-resolution records. In this study, we used a multi-proxy approach to reconstruct sedimentary OM variations over the past 100years from three sediment cores collected from the coastal areas of the ECS. For the three cores, total organic carbon (TOC) normalized concentrations of phytoplankton biomarkers (brassicasterol+dinosterol+alkenones) and a marine archaea biomarker (crenarchaeol) showed gradual increases over the past 100years with a greater increase after the 1980s. These increases are attributed to eutrophic conditions caused by monsoonal variation and intensified human activities in the Yangtze River Basin (YRB) over the past century. Conversely, TOC-normalized concentrations of higher plant biomarker long-chain n-alkanes (∑(C27+C29+C31n-alkanes)) showed no obvious trend over the past 100years. The δ13C values of TOC (δ13CTOC), the terrestrial and marine biomarker ratio (TMBR) index, and the branched and isoprenoid tetraether (BIT) index for the three cores record a gradual decrease in the contribution of terrestrial organic matter (TOM) since the 1960s. This decrease is likely linked to enhanced dam construction in the YRB from the 1960s onwards, leading to a reduction in TOM input to the ECS. A three end-member mixing model based on δ13CTOC values and the TMBR index was used to further divide sedimentary OM into three factions: marine organic matter (MOM), plant OM, and soil OM. The MOM contribution gradually increased over the past 100years, while the contribution of soil OM gradually decreased over the past 100years with a significant decline during the past 50years. This trend can also be related to intensify dam construction in the middle and upper reaches of the YR since the 1960s.

Urban Stream Vulnerability Toward PAHs and n-Alkanes and Their Source Identification

ABSTRACTMonjolinho River is an important water body located in the central urban region of São Paulo State in southeast Brazil. The present work reports a 4-year study related to spatio-temporal distribution and source identification of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in surface water and sediment samples of Monjolinho River. A total of 25 sampling campaigns for water, and 10 sampling campaigns for sediment collection, were performed from 2011 to 2014. In sediment samples, total PAHs were found in the range of 2.25 µg kg−1–26,253.87 µg kg−1, while n-alkane concentrations ranged from 0.01 to 165.64 µg kg−1. Total PAHs' concentration in surface water was in the range of 0.17–1,348.35 ng L−1, while n-alkanes were detected in the range of 6.17–316.15 µg L−1. Principal component analysis was used as a statistical tool for summarizing and interpreting a huge quantity of data. It was observed that concentrations of contaminants increased along the river course in urban zone. Distribution indexes were calculated to identify possible sources of carbon pool that pointed towards petrogenic, pyrogenic, and biogenic sources. The overall concentrations of PAHs and n-alkanes were low compared to many previous studies done elsewhere and were mostly below the threshold effects level except in very few occasional cases, while probable effect level was violated in 1 sample during 4 years. Although adverse impacts are unexpected due to overall low contaminant concentrations, unexpected industrial, and sewage discharges make it risky for safer use as a drinking water resource, especially in dry conditions.

Evaluation of sedimentary processes of plant particles by gravity flow using biomarkers in plant fragment-concentrated sediments of a turbiditic sequence in the Miocene Kawabata Formation distributed along the Higashiyama-gawa River, Yubari, Hokkaido, Japan

Distinctive plant fragment-concentrated sandstones are found in a turbiditic sequence deposited under deep sea environment in the Miocene Kawabata Formation distributed along the Higashiyama-gawa River, Yubari, central Hokkaido, Japan. We observed microscopically the plant fragments and analyzed terrestrial higher plant biomarkers in the sediments to evaluate sedimentological and hydrodynamic behaviors of plant particles by gravity flow depositional processes. Biomarker compositions such as pristane / phytane and regular sterane ratios indicate a large contribution of terrestrial organic matter, especially woody fragments, in the sandstone layer. The relative abundances of terrestrial higher plant terpenoids (pentacyclic triterpenoids, des-A-triterpenoids and diterpenoids) are high in all parts of the sandstone layer, while long-chain n-alkane concentrations are remarkably higher only at the uppermost part. Also, leaf cuticle fragments are mainly found in the uppermost part. These results suggest that plant leaves are mainly deposited in the uppermost part of the sandstone layer. Thus, it is concluded that the variations in plant fragment types (tissues) deposited are thought to be resulted from various hydrodynamic behavior in gravity flow.

Effects of Cerium Oxide and Ferrocene Nanoparticles Addition As Fuel-Borne Catalysts on Diesel Engine Particulate Emissions: Environmental and Health Implications.

This study systematically examined the potential impacts of doping CeO2 and Fe(C5H5)2 nanoparticles as fuel-borne catalysts (FBCs) to ultralow sulfur diesel (ULSD) fuel on the physical, chemical and toxicological characteristics of diesel particulate matter (DPM). The FBCs-doped fuels are effective in promoting soot oxidation and reducing the DPM mass emissions, but lead to a significant increase in the total particle counts due to the formation of self-nucleated metallic nanoparticles. Compared to undoped ULSD, the FBCs-doped fuels result in higher concentrations of particle-phase polycyclic aromatic hydrocarbons (PAHs) and n-alkanes, higher fractions of organic carbon (OC) and water-soluble organic carbon (WSOC) in particles, show slight alterations in soot nanostructure, reduce soot ignition temperature and activation energy. Exposure of the human-type II cell alveolar epithelial cells (A549) to DPM derived from FBCs-doped fuels shows a decrease in cell viability and alterations in the global gene expression with a broad range of biochemical pathways. The overall variations in DPM characteristics are mainly caused by the catalytic combustion process, and are related to the type, properties and contents of FBCs used in diesel fuel as well as the engine operating conditions. Environmental and health implications of the study are highlighted.

Source apportionment of polycyclic aromatic hydrocarbons and n-alkanes in the soil-sediment profile of Jianghan Oil Field, China.

Surface soil in oil exploration area always contains high contents of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes. To investigate the migration possibility of PAHs and n-alkanes from surface through aquitard and aquiclude to aquifer, the distribution, together with the source apportionment using several indicators, such as composition pattern, fluoranthene/(fluoranthene+pyrene) (Flt/(Flt+Pyr)), anthracene/(anthracene+phenanthrene) (Ant/(Ant+PA)), and the carbon preference index (CPI) of n-alkanes, in a 30-m-deep soil-sediment profile were studied. Results showed that there were considerable PAHs and n-alkanes not only in surface soil but also in aquitard, aquiclude, and aquifer sediments. The PAHs and n-alkanes in surface soil strongly suggested petroleum pollution. The high molecular weight PAHs and the n-alkanes with both long and short chains could not migrate into deep sediments as their sources in surface soil and deep sediment were different. Whereas the aquitard and aquiclude had significant input of low molecular weight PAHs (LMWPAHs) from petroleum sources, the LMWPAHs in confined aquifer suggested pyrogenic sources. Therefore, LMWPAHs migrated from surface to aquitard and aquiclude, but did not cause aquifer pollution in Jianghan Oil Field. However, the high mobility of LMWPAHs from surface to aquitard and aquiclude suggested that the long-term risk of groundwater pollution from oil exploration should be concerned.

Aliphatic and polycyclic aromatic hydrocarbons in surface sediments collected from mangroves with different levels of urbanization in southern Brazil

Three mangroves located in southern Brazil, Carijós (CA), Rio Tavares (RT) and Itacorubi (ITA), with distinct anthropogenic influences, were assessed with regard to the presence of aliphatic and polycyclic aromatic hydrocarbons (PAH). In this study, the n-alkane concentrations ranged from 1.9μg g−1 (CA) to 55.6μg g−1 (ITA) (dry weight). The carbon preference index (CPI) ranged from 2.1 to 7.9 and values for the terrestrial/aquatic ratio (TAR) were >1. Thus, both indexes indicated the predominance of sediment of terrestrial origin, mainly comprised of higher plants. Concentrations of total PAH ranged from 6.8ng g−1 (RT) to 437.3ng g−1 (ITA). The PAH isomeric ratios indicated that these compounds originated mainly from pyrogenic sources. Nevertheless, levels of n-alkanes in the three mangroves were relatively low and they are considered typical of uncontaminated surface sediments, while the level of contamination with PAH was classified as low to moderate.

Characteristic of quaternary sedimentation on a shelf of the Laptev Sea according to the molecular composition of n-alkanes

The molecular composition and distribution of the concentration of n-alkanes are considered for sediments of boreholes drilled in the shallow part of the Laptev Sea, in the area of Buor Khaya Gulf. The diverse molecular composition of n-alkanes is dominated by long-chain odd homologs, which indicate terrigenous organic matter (OM). Heterogeneous distribution and burial of OM are shown under conditions of pulsating contribution of river and thermoabrasive material and multiple changes in them up to hiatuses in sedimentation.

Distribution of n-alkanes in Miocene loess in Qinan, western Chinese Loess Plateau, and its palaeoenvironmental implications

Neogene eolian successions are one of the most important terrestrial palaeoenvironmental archives in East Asia. However, they have received far less attention than Quaternary loess deposits, especially in the case of lipid biomarker analysis. In order to obtain a better insight into the early-middle Miocene palaeoenvironment, we conducted a study of n-alkane biomarkers from sediments of the QA-I section (Qinan) in the western Chinese Loess Plateau, and compared the results with those of previous n-alkane analyses of eolian and aquatic sediments of varying age. Our principal results are as follows: (1) All QA-I samples contain n-alkanes ranging from C14 to C35, among which the relative content of short-chain n-alkanes (C14–C20) from microorganisms is significantly greater than that of long-chain n-alkanes (C26–C35) from the waxes of terrestrial higher plants; the main peak is at C16–C18. All samples have a relatively lower abundance of medium-chain n-alkanes (C21–C25) than that of long- and short-chain n-alkanes, similar to strongly weathered palaeosols in Quaternary loess and Late Miocene-Pliocene Hipparion Red-Earth; however, this distribution is significantly different from that in weakly-weathered loess of Quaternary loess and Late Miocene-Pliocene Hipparion Red-Earth, as well as from aquatic sediments. (2) Despite some odd-over-even carbon predominance of long-chain n-alkanes in the QA-I samples, the carbon preference index (CPI) values are significantly lower than those of most of the weakly-weathered sediments. Our results show that strong weathering and microbial processes have significantly altered the n-alkanes in the Miocene eolian deposits in Qinan, and led to a significant oxidation and degradation of long-chain n-alkanes and the predominance of short-chain n-alkanes from bacteria. Therefore, the contribution of microorganism to total organic carbon (TOC) and its resulting in carbon isotopic composition should be carefully assessed in future studies.

Altitude effect on leaf wax carbon isotopic composition in humid tropical forests

The carbon isotopic composition of plant leaf wax biomarkers is commonly used to reconstruct paleoenvironmental conditions. Adding to the limited calibration information available for modern tropical forests, we analyzed plant leaf and leaf wax carbon isotopic compositions in forest canopy trees across a highly biodiverse, 3.3km elevation gradient on the eastern flank of the Andes Mountains. We sampled the dominant tree species and assessed their relative abundance in each tree community. In total, 405 sunlit canopy leaves were sampled across 129 species and nine forest plots along the elevation profile for bulk leaf and leaf wax n-alkane (C27–C33) concentration and carbon isotopic analyses (δ13C); a subset (76 individuals, 29 species, five forest plots) were additionally analyzed for n-alkanoic acid (C22–C32) concentrations and δ13C. δ13C values display trends of +0.87±0.16‰km−1 (95% CI, r2=0.96, p<0.01) for bulk leaves and +1.45±0.33‰km−1 (95% CI, r2=0.94, p<0.01) for C29n-alkane, the dominant chain length. These carbon isotopic gradients are defined in multi-species sample sets and corroborated in a widespread genus and several families, suggesting the biochemical response to environment is robust to taxonomic turnover. We calculate fractionations and compare to adiabatic gradients, environmental variables, leaf wax n-alkane concentrations, and sun/shade position to assess factors influencing foliar chemical response. For the 4km forested elevation range of the Andes, 4–6‰ higher δ13C values are expected for upland versus lowland C3 plant bulk leaves and their n-alkyl lipids, and we expect this pattern to be a systematic feature of very wet tropical montane environments. This elevation dependency of δ13C values should inform interpretations of sedimentary archives, as 13C-enriched values may derive from C4 grasses, petrogenic inputs or upland C3 plants. Finally, we outline the potential for leaf wax carbon isotopes to trace biomarker sourcing within catchments and for paleoaltimetry.

Blends of butanol and hydrotreated vegetable oils as drop-in replacement for diesel engines: Effects on combustion and emissions

This work investigates the performance of a mix of two emerging biofuels, butanol and hydrotreated vegetable oil (HVO), in an Iveco Tector diesel engine with no aftertreatment. HVO, a possible drop-in fuel for diesel engines, features excellent combustion and emissions characteristics yet is relatively expensive, while two isomers of butanol, n-butanol and isobutanol, are less expensive oxygenated fuels with a drawback to their use in diesel engines in the form of their increased ignition delay and, on some engines, higher emissions of nitrogen oxides.Blends of 30% of either n-butanol or isobutanol into HVO had, compared to diesel fuel, resulted in a 70–80% decrease in the emissions of elemental carbon and carcinogenic polycyclic aromatic hydrocarbons (cPAHs) and a moderate decrease in the emissions of nitrogen oxides, without showing an adverse effect on combustion timing, heat release rates, engine maximum torque, thermal efficiency, and other measured pollutants.Particulate matter from biodiesel, HVO, their blends with diesel fuel, and the above mentioned blends was also analysed for elemental carbon (EC) and organic carbon (OC), polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs, n-alkanes and organic tracer compounds, including hopanes, steranes, and isoprenoids. n-Alkanes were the most abundant class among the analysed particulate organic compounds in emissions of all fuels. All biofuels exhibited, relative to diesel fuel, a decrease in the concentration of particulate PAHs and n-alkanes in emissions, while the concentrations of hopanes and steranes originated from lubricating oil were comparable across all fuels. Cold starts yielded about 15% higher concentrations of both particulate matter and particulate organic compounds in emissions than hot starts. The vast majority of EC and OC, studied organic compounds, and mass of PM2.5 was included in the size fraction PM1.

Spatial distribution and composition of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons and hopanes in superficial sediments of the coral reefs of the Persian Gulf, Iran

This study is the first quantitative report on petroleum biomarkers from the coral reefs systems of the Persian Gulf. 120 reef surface sediment samples from ten fragile coral reef ecosystems were collected and analyzed for grain size, biogenic elements, elemental ratios, and petroleum biomarkers (n-alkanes, PAHs1 and Hopanes) to assess the sources and early diagenesis of sedimentary organic matter. The mean grain size of the reef sediments ranged from 13.56 to 37.11% (Clay), 26.92 to 51.73% (Sand) and 35.97 to 43.85% (Silt). TOC2 (3.35–9.72 mg.g−1) and TON3 (0.4–1.10 mg.g−1) were identified as influencing factors on the accumulation of petroleum hydrocarbons, whilst BC4 (1.08–3.28 mg.g−1) and TIN5 (0.13–0.86) did not exhibit any determining effect. Although BC and TIN demonstrated heterogeneous spatial distribution, TOC and TON indicated homogenous distribution with continually upward trend in concentration from the east to west ward of the Gulf. The mean calculated TOC/TN ratios vacillated according to the stations (p < 0.05) from 2.96 at Shidvar Island to 8.64 at Hengam Island. The high TOC/TN ratios were observed in the Hengam (8.64), Kharg (8.04) and Siri (6.29), respectively, suggesting a predominant marine origin. The mean concentrations of ∑C11–35n-alkanes, ∑30 PAHs and ∑9Hopanes were found in the ranges of 385–937 μg.g−1dw, (overall mean:590 μg.g−1dw), 326–793 ng.g−1dw (499 ng.g−1dw), 88 to 568 ng.g−1 d (258 ng.g−1dw), respectively. Higher concentrations of detected petroleum biomarkers in reef sediments were chiefly distributed near main industrial areas, Kharg, Lavan and Siri, whilst the lower concentrations were in Hormoz and Qeshm. In addition, one-way ANOVA6 analysis demonstrated considerably significant differences (p < 0.05) among concentration of detected total petroleum hydrocarbons between most sampling locations. Some sampling sites especially Kharg, Lavan, Siri and Lark indicated higher concentration of n-alkanes due to the higher maintenance of organic matter by high clay content in the sediments. Furthermore, most sediment samples, except for Hormoz, Qeshm and Hengam showed an even carbon preference for n-alkanes which could be correlated to bacterial input. NPMDS7 analysis also demonstrated that among the congeners of petroleum biomarkers, n-C12,n-C14, n-C16,n-C18 and n-C20 for n-alkanes, Phe8 and Naph9 along with their Alkyl homologues for PAHs (2–3 rings accounted for 60%) and C30αβ and C29αβ for Hopanes were discriminated from their other congeners in the whole study area. Our results based on the PCA10 analysis and diagnostic indices of AHs11 and PAHs along with ring classification of PAHs, in addition, the ubiquitous presence of UCM,12 and Hopanes revealed that the main sources of the pollution were petroleum and petroleum combustion mainly from offshore oil exploration and extraction, discharge of pollutants from shipping activities.

Application of porous materials in oil substances separation from water

The aim of the study was to determine the ability of the four porous materials: birch bark, cork, glass wool, and polyurethane foam to reduce the mineral oil index and the concentration of n-alkanes C 7 H 16 -C 38 H 78 as well as to select the most efficient materials. Model solutions of gasoline, diesel oil, and distilled water with the following values of mineral oil index were prepared to tests: 52 μg/dm 3 , 68 μg/dm 3 and 73 μg/dm 3 . Then, studies were carried out using a dynamic method, wherein the columns were filled with adsorbents tested, and in each of three testing series, 500 mL of the model solution at constant bed load of 1,0551 m3/m2h was filtered through the column. After filtration, the collected sample had volume of 250 mL. The collected samples were subject to determination of mineral oil index and concentrations of n-alkanes from C 7 H 16 to C 38 H 78 . Studies have shown that the most effective materials to lower the mineral oil index and the concentrations of n-alkanes in water are birch bark and glass wool.

First Investigation of Seasonal Concentration Behaviors and Sources Assessment of Aliphatic Hydrocarbon in Wastewater and Sediment from Wadi El Bey, Tunisia

The contents, composition profiles and sources of aliphatic hydrocarbons were examined in surface sediment and water samples collected from Wadi el Bey watershed, Tunisia, during different year seasons in 14 sites receiving domestic effluent, industrial discharge and agricultural drainage wastes. The target substances were analyzed by gas chromatography coupled with mass spectrometric detection (GC/MSD). Total concentrations of n-alkanes (C14-C38) ranged from 0.08 ± 0.01 to 18.14 ± 0.1 μg/L in waters and 0.22 ± 0.04 to 31.9 ± 24.6 μg/g in sediments, while total aliphatic fraction ranged from 0.08 ± 0.01 up to 196 ± 140 μg/L in waters and 0.22 ± 0.04-1977 ± 1219 μg/g in sediments, which means that almost all sites were affected by hydrocarbon contents in sediments exceeding the recommended limit (100 μg/g). Various diagnostic indices (ADIs) were used to identify the hydrocarbon sources, namely the concentration ratios of individual compounds as well as cumulative quantities. These indexes indicated that the origin of aliphatic hydrocarbons affecting sediments and waters of Wadi el Bey were linked to both biogenic and petrogenic inputs, attesting the impact of plankton and terrestrial plants and of oil contamination, respectively. The average carbon chain length computation (ACL), used to further index the chemical environment, ranged from 25.5-31.1 in sediments and 47.9-116 in waters; this finding could depend on the severe disturbances suffered by the ecosystem as a consequence of heavy anthropogenic inputs. In conclusion, petroleum contamination associated with high eutrophication rates in the Wadi el Bey Watershed must be strictly controlled, due to possible harmful effects induced on ecosystem and humans.

Particulate Size Distribution and Sources Evaluation of n-Alkanes during Long-Term Haze Episode around Chaohu Lake, Eastern China

ABSTRACTn-Alkanes (from nC16 to nC32) associated with particulate matters were determined in the ambient air around Chaohu Lake, Eastern China, from October to December in 2014 during a long-term haze episode. The total concentrations of particle bounded n-alkanes varied from 332 to 2500 ng m–3, with the homologues of nC24–nC30 the most abundant species. Spatial analysis revealed that low concentrations of n-alkanes existed at the sites close to Chaohu Lake, while high concentrations were generally at locations distant from the lake. For all aggregated fractions, most n-alkanes were distributed in fine particles with the mean geometric mean diameter (GMD) varying from 3.0 ± 0.6 µm for nC16 to 2.1 ± 0.6 µm for nC32. Short chain n-alkanes were accumulated in coarse particles with a unimodal distribution, but long chain aliphatic hydrocarbons appeared to have a biomodal distribution in fine and coarse particles. The mass size distribution of individual n-alkane homologue was predominantly influenced by its volatility; thus GMDs were well correlated with the logarithmically transformed subcooled liquid vapor pressures (PLo, Pa) of n-alkanes at each sampling site, following the equation: GMDs = mgLogPLo + bg. Furthermore, mg and bg obtained from all locations tended to exhibit a significant linear correlation. This suggests that all saturated aliphatic hydrocarbons follow a similar accumulation mode during a haze episode, which allows us to predict the size distribution and GMD of a compound based on its PLo.

Pollution Characteristics and Source Apportionment of PM2.5-Bound n-Alkanes in the Yangtze River Delta, China

ABSTRACTPM2.5-bound n-alkanes in Shanghai (SH), Nanjing (NJ) and Ningbo (NB) cities from November 2014 to August 2015 were investigated. Averaged concentrations of the total 25 n-alkanes (∑n-alkanes, C16–C40) in SH, NJ and NB were 97.4 ± 73.9, 83.8 ± 57.1 and 187.1 ± 87.1 ng m–3, respectively. Obvious spatial and seasonal variations were attributed to the differences of emission sources and meteorological conditions. Analysis of the diagnostic ratios and specific molecular markers of n-alkanes suggested that high plant wax and vehicle emissions were the major sources of n-alkanes in the YRD region. Strong inputs of microbial components in summer were found and attributed to the emission from plankton in the ocean. The annual average contributions of higher plant wax to n-alkanes (%wax) in SH, NJ and NB were estimated to be 47.5%, 50.1% and 34.5%, respectively. Anthropogenic sources were responsible for the n-alkanes in NB, while biogenic sources contributed much more n-alkanes in NJ and SH. Based on the result of backward analysis, the emissions of n-alkanes in NB and NJ were mainly from local sources when the air masses came from the sea and south China with low n-alkanes concentrations. When the air masses originated from north China, the transport of contaminant aggravated the pollution of n-alkanes in SH.

Palaeoenvironmental control on primary fluids characteristics of lacustrine source rocks in the Autun Permian Basin (France)

The Autunian (Late Gzhelian-Sakmarian, ∼295 Ma) of the Autun Basin (Saône-et-Loire, France) is well known for its lacustrine oil-shales and boghead that were exploited during the 19th and 20th centuries. A study of the kerogen geochemistry, palynofacies, hydrocarbon (HC) distribution of pyrolysates and kinetics on these organic-rich sediments gave indications on the control of lacustrine primary fluid characteristics by palaeoenvironmental settings. Palynofacies results have shown a Botryococcus algae dominance in the boghead, whereas the oil-shales were dominated either by a mixing of terrestrial particles and lacustrine phytoplanktonic/bacterial organic matter (OM), or by a lacustrine OM that suffered biodegradation within the water column. During the Autunian, an increasing trend of degraded lacustrine OM concentration is observed in the successive oil-shales. Geochemical and kinetics analyses showed that, except for the boghead, hydrogen index values were &lt; 700 mg/g TOC and activation energies diagram showed multi-energetic profiles, unexpected for such a lacustrine OM. Along with pyrolysates primary fluids ones, these results unraveled two groups of oil-shale samples. On the one hand, samples dominated by well-preserved lacustrine and terrestrial OM produced primary fluids dominated by n-alkanes with (n-C6-n-C14) /n-C14+ n-alkanes ratio depending on the proportion of terrestrial OM. They were only encountered in the three oldest oil-shales. On the other hand, the HC profile of fluids originating from samples dominated by degraded lacustrine OM, which was obtained for the first time in this study, show low n-alkanes concentrations and a relatively prominent hump. These samples were only present in the three youngest oil-shale levels. Finally, the boghead showed a link between strong concentration of the Pila genus of Botryococcus algae and a primary fluid dominated by n-C6-n-C14 n-alkanes. By comparing these data with published palaeoenvironmental studies, it appears that the kind of dominant OM, and thus the HC distribution of primary fluids, is controlled by the lake level: a lower depth preventing the settlement of anoxic conditions in the bottom waters, and the subsequent good preservation of the OM. During the Autunian, the lake level decreased, consequence of a reduced tectonic activity and of the beginning of a dryer period. Finally, these changes will have caused a strong decrease of the nutrient influx to the lake, favoring the bloom of Botryococcus algae that accumulated to form the boghead.

Seasonal variations and source profile of n-alkanes in particulate matter (PM10) at a heavy traffic site, Delhi.

Delhi is one of the most polluted cities in the world. The generation of aerosols in the lower atmosphere of the city is mainly due to a large amount of natural dust advection and sizable anthropogenic activities. The compositions of organic compounds in aerosols are highly variable in this region and need to be investigated thoroughly. Twenty-four-hour sampling to assess concentrations of n-alkanes (ng/m3) in PM10 was carried out during January 2015 to June 2015 at Indira Gandhi Delhi Technical University for Women (IGDTUW) Campus, Delhi, India. The total average concentration of n-alkanes, 243.7±5.5ng/m3, along with the diagnostic tools has been calculated. The values of CPI1, CPI2, and CPI3 for the whole range of n-alkanes series, petrogenic n-alkanes, and biogenic n-alkanes were 1.00, 1.02, and 1.04, respectively, and C max were at C25 and C27. Diagnostic indices and curves indicated that the dominant inputs of n-alkanes are from petrogenic emissions, with lower contribution from biogenic emissions. Significant seasonal variations were observed in average concentrations of n-alkanes, which is comparatively higher in winter (187.4±4.3ng/m3) than during the summer season (56.3±1.1ng/m3).

Modern n-alkane abundances and isotopic composition of vegetation in a gymnosperm-dominated ecosystem of the southeastern U.S. coastal plain

Prior analyses of n-alkyl lipids in vegetation indicate low concentrations of n-alkanes in gymnosperm leaves and significant offsets in lipid carbon isotope values of angiosperms and gymnosperms. This finding has implications for paleoenvironmental studies utilizing n-alkyl lipid proxies in gymnosperm-dominated ecosystems, such as the pine ecosystems of the U.S. southeastern coastal plain. I provide here the n-alkane abundances and distributions for 19 of the most dominant taxa in the longleaf pine ecosystem along with n-C29 alkane δ13C values (δ13Cn-c29). Additionally, I assess modern relationships between stable hydrogen isotope values of n-C29 alkanes (δ2Hn-c29) and mean annual precipitation to constrain apparent fractionations (ε2Hn-C29/MAP) necessary to conduct regional paleoclimate reconstructions. Gymnosperms of the coastal plain have extremely low n-alkane abundances relative to angiosperms and are unlikely to contribute significantly to sedimentary archives. Lake surface sediment n-alkane distributions, δ2Hn-c29, and δ13Cn-c29 values indicate that they are primarily sourced from less-dominant angiosperms. The ε2Hn-C29/MAP values are ∼10.0‰ VSMOW more positive for gymnosperms relative to angiosperms and ε13Calkane/leaf values are ∼1.5‰ VPDB more positive for gymnosperms relative to angiosperms, but with overlap.