Concentrations Of N-alkanes Research Articles

Temporal variation of seston biomarkers within the Humboldt Current System off northern Chile (21

Proportions and concentrations of seston fatty acids, n-alkanes and glycerol dialkyl glycerol tetraethers (GDGTs) were used to assess potential differences in the phytoplankton composition and food quality in the Humboldt Current System (winter 2006, summer 2007 and winter 2007) in surface, oxycline, intermediate and bottom water layers. The zone below the intermediate depth was poorer in fatty acids (minimum 15 – maximum 117mg fatty acids L

Seasonal and spatial variations of individual organic compounds of coarse particulate matter in the Los Angeles Basin

To study the organic composition of ambient coarse particulate matter (CPM; 2.5–10 μm), coarse particles were collected one day a week from April 2008 to March 2009 at 10 sampling sites in the Los Angeles Basin. Samples were compiled into summer (June 2008 to September 2008) and winter (November 2008 to February 2009) composites, and were subsequently analyzed for individual organic constituents using gas chromatography-mass spectrometry. n-alkanoic acids and medium molecular weight (MW) n-alkanes (C25 to C35) – the major constituents in the coarse size fraction – showed good associations with crustal materials. Polycyclic aromatic hydrocarbons (PAHs) and hopanes (both in low concentrations), as well as high MW n-alkanes (C37 and C38), were associated with traffic-related emissions. In the summer, when prevailing onshore winds were strong, the downwind/rural sites had higher concentrations of PAHs, n-alkanes and n-alkanoic acids. An opposite trend was observed at the urban sites, where the levels of PAHs, n-alkanes and n-alkanoic acids were higher in the winter, when the low wind speed limited long-range atmospheric transport. In general, the contribution of organic compounds to CPM mass was higher during wintertime, due to a reduction in the fraction of other CPM components (sea salt, secondary ions, etc.) and/or the increase in source strengths of organic compounds. The latter is consistent with the traffic-induced re-suspension of mineral and road dust, as previously observed in this basin. Overall, our results suggest that emissions from natural sources (soil and associated biota) constitute the majority of the organic content in coarse particles, with a more pronounced influence in the semi-rural/rural areas in Riverside/Lancaster compared with urban Los Angeles in the summer.

Last glacial vegetation reconstructions in the extreme-continental eastern Asia: Potentials of pollen and n-alkane biomarker analyses

The current study presents quantitative reconstructions of tree cover, annual precipitation and mean July temperature derived from the pollen record from Lake Billyakh (65°17′N, 126°47′E, 340 m above sea level) spanning the last ca. 50 ka (ca. 50,000 cal yrs). The reconstruction of tree cover suggests presence of woody plants through the entire analyzed time interval, although trees played only a minor role in the vegetation around Lake Billyakh prior to 14 ka BP (<5%). This result corroborates low percentages of tree pollen and low scores of the cold deciduous forest biome in the PG1755 record from Lake Billyakh. The reconstructed values of the mean temperature of the warmest month ∼8–10 °C do not support larch forest or woodland around Lake Billyakh during the coldest phase of the last glacial between ∼32 and ∼15 ka BP. However, modern cases from northern Siberia, ca. 750 km north of Lake Billyakh, demonstrate that individual larch plants can grow within shrub and grass tundra landscape in very low mean July temperatures of about 8 °C. This makes plausible the hypothesis that the western and southern foreland of the Verkhoyansk Mountains could provide enough moist and warm microhabitats and allow individual larch specimens to survive climatic extremes of the last glacial. Reconstructed mean values of annual precipitation are about 270 mm during the last glacial interval. This value is almost 100 mm higher than modern averages reported for the extreme-continental north-eastern Siberia east of Lake Billyakh, where larch-dominated cold deciduous forest grows at present. This suggests that last glacial environments around Lake Billyakh were never too dry for larch to grow and that the insufficient summer warmth was the main factor, which limited tree growth during the last glacial interval. The n-alkane analysis of the Siberian plants presented in this study demonstrates rather complex alkane distribution patterns, which challenge the interpretation of the fossil records. In particular, extremely low n-alkane concentrations in the leaves of local coniferous trees and shrubs suggest that their contribution to the litter and therefore to the fossil lake sediments might be not high enough for tracing the Quaternary history of the needleleaved taxa using the n-alkane biomarker method.

Petroleum Products and Phenols in Snow Cover in Khabarovsk, Southern Russian Far East

To have a better understanding of the industrial organic contamination of the city of Khabarovsk, southern Russian Far East, snow cover of the winter seasons of 2009–2010 and 2010–2011 was sampled at the end of March of 2010 and 2011 at six sites (and at eight sites in 2011) of the urban area and on the adjacent snow cover of the Amur River. The samples were analyzed by high-performance liquid chromatography and gas chromatography/mass spectrometry techniques for petroleum products and phenols. The main groups of the detected pollutants were n-alkanes, isoalkanes, paraffins, phenols, and phthalates. The total concentration of the petroleum products was 0.08–2.84 mg/L, volatile phenols 0.17–3.61 μg/L. 4-Nitrophenol has been found among the phenols (0.22–1.65 μg/L). The minimum toxicant concentrations were found in background sites (first hundred meters) off the urban highways, and the maximum, in dumps of snow from the urban highways and the vicinities of Heat Power-3. Of aromatic compounds, insignificant amounts of isopropylbenzene (0.5 μg/L) and xylenes (0.2–0.3 μg/L) and a high content of ethylbenzene (1.3 μg/L) originated from local emission were found. For the unpolluted sites, identification of n-alkanes revealed high-molecular paraffins C26–C33 (50 % of the total n-alkane content); fractions in the range of C19–C21 and C24 were found for the snow dumps, 55.0 % and 90.0 % of the total alkane content in 2010 and 2011, correspondingly. These compounds originated most probably from the wasted diesel fuel and mineral greases (derivatives). The study indicated the dangerous level of the Khabarovsk urban atmosphere deterioration with a range of organic pollutants of transport and industrial origin. The snow (and rain) urban runoff may affect the local soil and water ecosystems subsequently.

Application of urea adduction technique to polluted urban aerosols for the determination of hydrogen isotopic composition of n-alkanes

We examined an applicability of an improved urea adduction technique for the determination of hydrogen isotopic composition (δD) of homologous series of n-alkanes present in polluted urban aerosols using GC/TC/IRMS. Unresolved complex mixture (UCM) of hydrocarbons that interferes with accurate isotope measurements of n-alkanes was removed from n-alkane fraction by a urea adduction method. Recoveries of C20 to C30 n-alkanes during the urea adduction procedure were greater than 90% when the concentrations of total n-alkanes exceed 6.1 µg mL−1. Our compound-specific D/H ratios confirm the absence of significant hydrogen isotope fractionation in n-alkanes during urea adduction and recovery of the purified n-alkane fraction. We applied this technique to the urban aerosols that contain a large quantity of UCM to measure δD of C20 to C35 n-alkanes in urban aerosols from Tokyo and Sapporo with an accuracy less than 10‰. We found that the δD values widely ranged from −38 to −179‰. Based on the δD values of individual n-alkanes in aerosol samples, we can obtain further information on the sources of aerosol n-alkanes and their source regions, and the atmospheric processes such as long-range transport and atmospheric mixing of air masses of different origin.

Cuticular and internal n-alkane composition ofLucilia sericatalarvae, pupae, male and female imagines: application of HPLC-LLSD and GC/MS-SIM

The composition of cuticular and internal n-alkanes in Lucilia sericata larvae, pupae, and male and female imagines were studied. The cuticular and internal lipid extracts were separated by HPLC-LLSD, after which the hydrocarbon fraction was identified by GC/MS in selected ion monitoring (SIM) and total ion current (TIC) modes. The cuticular lipids of the larvae contained seven n-alkanes from C23 to C31. The major n-alkane in L. sericata larvae was C29 (42.1%). The total cuticular n-alkane content in the cuticular lipids was 31.46 μg g-1 of the insect body. The internal lipids of L. sericata larvae contained five n-alkanes ranged from C25 to C31. The most abundant compound was C27 (61.71 μg g-1 of the insect body). Eighteen n-alkanes from C14 to C31 were identified in the cuticular lipids of the pupae. The most abundant n-alkanes ranged from C25 to C31; those with odd-numbered carbon chains were particularly abundant, the major one being C29:0 (59.5%). Traces of eight cuticular n-alkanes were present. The internal lipids of L. sericata pupae contained five n-alkanes, ranging from C25 to C31. The cuticular lipids of female imagines contained 17 n-alkanes from C12 to C30. Among the cuticular n-alkanes of females, C27 (47.5%) was the most abundant compound. Four n-alkanes, with only odd-numbered carbon chains, were identified in the internal lipids of females. The lipids from both sexes of L. sericata had similar n-alkane profiles. The cuticular lipids of adult males contained 16 n-alkanes ranging from C13 to C31. C27 (47.9%) was the most abundant cuticular n-alkanes in males. The same n-alkanes only with odd-numbered carbon chains and in smaller quantities of C27 (0.1%) were also identified in the internal lipids of males. The highest amounts of total cuticular n-alkanes were detected in males and females of L. sericata (330.4 and 158.93 μg g-1 of the insect body, respectively). The quantities of total cuticular alcohols in larvae and pupae were smaller (31.46 μg g-1 and 42.08 μg g-1, respectively). The internal n-alkane contents of larvae, pupae, and male and female imagines were significantly higher than the cuticular n-alkane contents (153.53, 99.60, 360.06 and 838.76 μg g-1 of the insect body, respectively).

Incorrect when uncorrected: Reconstructing vegetation history using n-alkane biomarkers in loess-paleosol sequences – A case study from the Saxonian loess region, Germany

This study aims at contributing to the reconstruction of the paleoenvironment of the Saxonian loess region by investigating sedimentary n-alkanes as plant leaf-wax derived biomarkers in two loess-paleosol sequences (LPSs), namely the Gleina and the Rottewitz LPSs.The Weichselian paleosols are characterised by n-alkane concentration maxima when compared to the loess layers. When this coincides with high odd-over-even predominances (OEPs), this points not only to increased n-alkane input and/or production but also to increased n-alkane preservation in the soils, namely in gleysols with water-logged edaphic conditions. By contrast, the buried cambisols reveal low OEPs, indicating accelerated degradation under aerobic edaphic conditions. The n-alkane concentrations in the truncated Eemian Interglacial paleosol are very low. This reflects the removal of the formerly n-alkane-enriched Eemian topsoil, low n-alkane input into the Bt-Sd-horizon (subsoil horizon of the Eemian luvisol) and/or strong soil organic matter mineralization. Four investigated n-alkane ratios show distinct variations during the Weichselian, tempting inferences of vegetation changes in terms of varying contributions of tree/shrub-derived (dominated by nC27 or nC29) versus grass-derived (dominated by nC31 or nC33) n-alkanes. However, using the OEP as a proxy for degradation and considering that n-alkane ratios are prone to degradation effects, the above interpretation is very likely incorrect. Degradation can account for most variability of the n-alkane ratios.Applying an endmember model based on a modern n-alkane reference dataset allows estimating the contribution of tree/shrub- versus grass-derived n-alkanes semi-quantitatively. These modelling results suggest that both the Gleina and the Rottewitz LPSs were formed under prevailing grassland. Minor contributions of trees/shrubs are only likely for the Gleinaer Soil Complex in Rottewitz LPS, for the top of a Brown Gleysol in Gleina LPS and the Holocene soil. The Weichselian vegetation changes as inferred from the uncorrected n-alkane ratios are not confirmed. Overall, the n-alkane results support the idea that the Gleinaer Soil Complex in Gleina and Rottewitz LPS, respectively, are not identical but rather are chronostratigraphic equivalents. More favourable regional climatic conditions presumably occurred in the southwesterly exposed Rottewitz locality and allowed tree/shrub vegetation to grow during favourable periods of the Weichselian. A major shortcoming of the n-alkane biomarker method is that only vegetation changes of deciduous woodland to grassland and vice versa can be reconstructed, because coniferous trees exhibit, by two to three orders of magnitude, lower n-alkane concentrations.

Microbial alteration of natural gas in Xinglongtai field of the Bohai Bay Basin, China

Xinglongtai field has been an important petroleum-producing area of Liaohe Depression for 30 years. Oil exploration and production were the focus of this field, but the gas was ignored. This study examined twenty five gas samples with the purpose of determining the gas genetic types and their geochemical characteristics. Molecular components, stable carbon isotopic compositions and light hydrocarbons were also measured, and they proved that microbial activity has attacked some of the gas components which resulted in unusual carbon isotopic distributions. Propane seems to be selectively attacked during the initial stage of microbial alteration, with abnormally lower content compared to that of butane as well as anomalously heavy carbon isotope. As a consequence, the carbon isotopic distribution among the gas components is partially reverse, as δ13C1 δ13C4. Besides, n-alkanes of C3+ gas components are preferentially attacked during the process of microbial alteration. This is manifested that n-alkanes are more enriched in 13C than corresponding iso-alkanes. As a result, the concentrations of n-alkanes become very low, which may be misleading in indentifying the gas genetic types. As to four gas samples, light hydrocarbon compositions display evidence for microbial alteration. The sequence of hexane isomers varies obviously with high content of 2,3-DMC4, which indicates that they have been in the fourth level of extensively bacterial alteration. So the geochemical characteristics can be affected by microbial alteration, and recognition of microbial alteration in gas accumulations is very important for interpreting the natural gas genetic types.

The Distribution of n-alkanes and polycyclic aromatic hydrocarbons in Water of Taihu Lake

The water samples were collected from different regions in a shallow eutrophic lake, Taihu Lake, China. The distribution and the possible pollution sources of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) in Taihu water were analyzed. The results showed that the concentrations ranged between 0.045 and 0.281 mg/L for n-alkanes which were dominated by C8-C33 with no odd–even carbon number predominance, 0.011-0.034 mg/L for total PAHs which were predominated by two- and three-ring PAHs. The concentrations of n-alkanes and PAHs were higher in those samples collected near industrial locations than those from few or no industrial areas. Relatively high concentrations in water were measured from sampling sites S10 (Dapu in Yixing) and S16 (Zhu Shan Bay). The contamination of n-alkanes in Taihu water mainly derived from petroleum pollution caused by human activities, while the PAHs contamination was the result of both petroleum pollution source and combustion source according to the sources apportionment of n-alkanes and PAHs pollution.

Epicuticular-wax removal influences gas exchange and water relations in the leaves of an exotic and native species from a Brazilian semiarid region under induced drought stress

The primary physiological function of the leaf cuticle is to limit water loss. Thus, in the present study, we examined the hypothesis that variation in the quality and content of the epicuticular wax between different species influences leaf gas exchange. Plants of Jatropha mollissima (Pohl) Bailon, a Brazilian semiarid native, and Jatropha curcas L. (Euphorbiaceae), an exotic species, were subjected to a water deficit in the presence or absence of epicuticular wax. Plants were grown in 10-L pots under greenhouse conditions. The relative water content, gas-exchange parameters and primary carbon metabolism were measured at 21 days after the irrigation was reduced to induce a water deficit. The well-watered plants of both species showed recovery of gas exchange days after the removal of epicuticular wax. Furthermore, under drought, a gradual increase in transpiration rates was observed only in the leaves of native species without wax, although the stomatal conductance did not differ between the species. High relative water content was maintained, except in the leaves under drought and without wax from Day 13 onward, when compared with all other treatments. The wax production was induced in both species under water shortage. Nevertheless, the native species showed a higher content of long-chain n-alkanes. In fact, the barrier to water vapour under reduced stomatal conductance was highest in the native species.

Chemical Speciation and Source Assignment of Particulate (PM10) Phase Molecular Markers in Mumbai

Particulate matter (PM10) has emerged as the single most important pollutant across Indian cities, as its levels exceed the regulated standards at most places. PM10 was collected and analyzed at seven sites representing different land use patterns in Mumbai during 2007–08 for organic carbon (OC) and elemental carbon (EC). OC was further speciated for organic markers, which are useful for identifying sources. Average PAH concentration ranged from 47.84 ± 14.07 to 247.70 ± 163.19 ng/m3. n-alkanes concentration varied from 157.20 ± 35.28 to 759.13 ± 451.65 ng/m3. Hopanes and steranes showed the highest concentrations of 94.14 ± 28.66 and 32.64 ± 11.79 ng/m3 and lowest concentrations of 7.81 ± 2.00 ng/m3 and 2.83 ± 0.73 ng/m3, respectively. The values for levoglucosan varied from 0.69 ± 0.46 to 3.23 ± 2.07 µg/m3. The percentage contribution of the sum of the concentrations of these compounds to the total organic carbon varied from 1.7–5.1%. The sources contributing to particulate PAHs were identified using diagnostic ratios. Indicators like the Carbon Preference Index (CPI), Cmax and Plant Wax Number (%WNA) were used to identify the relative contributions to n-alkanes from anthropogenic and biogenic emissions. The source apportionment results and also the concentration trends for these molecular markers indicate that anthropogenic sources, especially vehicular exhaust, wood combustion and coal combustion, are mainly responsible for the organic fraction of particulate matter in Mumbai city. The sources identified qualitatively in this work can help in selecting the appropriate source profiles for estimating the quantitative contribution of these sources.

Airborne particulate organics at the summit (2060 m, a.s.l.) of Mt. Hua in central China during winter: Implications for biofuel and coal combustion

Sugars, n-alkanes and PAHs in PM 10 and size-segregated samples collected from the summit (2060 m, altitude) of Mt. Hua in Guanzhong Plain, central China during the winter of 2009 were characterized using a GC/MS technique. Concentrations of sugars, n-alkanes and PAHs in PM 10 are 107 ± 52, 121 ± 63, 7.3 ± 3.4 ng m − 3 , respectively. Levoglucosan and fossil fuel derived n-alkanes are more abundant in the air masses transported from southern China than in those from northern China with no spatial difference found for PAHs, suggesting that emissions from biomass burning and vehicle exhausts are more significant in southern part of the country. Dehydrated sugars, fossil fuel derived n-alkanes and PAHs presented a unimode size distribution, peaking at the size of 0.7–1.1 μm, whereas non-dehydrated sugars and plant wax derived n-alkanes showed a bimodal pattern, peaking at 0.7–2.1 and 5.8–9.0 μm, respectively. Principal component analysis showed that biofuel combustion plus plant emission is the most important source in Mt. Hua, being different from the cases in Chinese urban areas where fossil fuel combustion is the major source. By comparison with previous mountain and lowland observations and aircraft measurements we found that wintertime PAHs in China are still characterized by coal burning emissions especially in the inland regions, although in the country increasing rate of SO 2 emission from coal combustion has decreased and emissions of vehicle exhaust has sharply increased.

Fluid circulation and formation of minerals and bitumens in the sedimentary rocks of the Outer Carpathians – Based on studies on the quartz–calcite–organic matter association

Different methods have been used to examine minerals and/or solid bitumens in three adjacent Carpathian regions of Poland, Ukraine and Slovakia. The minerals fill smaller and larger veins and cavities, where they occur either together or separately. They usually co-occur with the solid bitumens. All δ13CPDB values measured for calcite lie in a relatively wide interval between −6.25‰ and +1.54‰, while most values fall into the narrower interval from below 0 to about −3‰. The general range of calcite δ18O results for the whole studied region is between +17.13‰ and +25.23‰ VSMOW or from about −11 to −5‰ VPDB, while the majority of these values are between +20.0 and 23.5‰ VSMOW (−10.53 and −8.00‰ PDB, respectively). δ18OVSMOW results for quartz vary between +23.2 and 27.6. The carbonate percentage determined in some samples falls between from <2% CaCO3 to >90% CaCO3, while the TOC values changes from 0.09% to over 70%.The aliphatic fraction predominates in all studied samples, mainly in bitumens and oils. The composition of the aliphatic fraction is relatively homogeneous and points to a strong aliphatic, oil-like paraffin character of the bitumens. Such a composition is characteristic of the Carpathian oils and different from the rocks studied that contain the higher percentage of a polar fraction. The content of the aliphatic fraction in bitumens is only slightly higher than that in two oils used for comparison. The distribution of n-alkanes is variable in rocks, solid bitumens as well as inclusions in quartz and calcite. Two groups of bitumens may be distinguished. Those with a predominance of long-chain n-alkanes in the C25–C27 interval (in some cases from C23–C25 and without or with a very low concentration of short-chain n-alkanes in the interval of C14–C21) show also a high content of isoprenoids i.e. of pristane (Pr) and phytane (Ph). In all but one bitumen samples, Pr predominates over Ph. The second group comprises oils and rock samples with a characteristic predominance of short-chain n-alkanes in the interval from C13–C19 and a low percentage of the long-chain n-alkanes from the n-C27–n-C33 interval. Pristane and phytane exhibit a concentration comparable to that of C17 and C18n-alkanes with a Pr predominance over Ph. Due to high maturity, only small amounts of the most stable compounds from the hopane group have been observed in the samples, also oleanane in one case. Among the aromatic hydrocarbons, phenanthrene and its methyl- and dimethyl-derivatives are dominant in bitumens, source rocks and inclusions in calcite and quartz. Occurrence of cyclohexylbenzene and its alkyl-derivatives as well as cyclohexylfluorenes in solid bitumens suggest that they formed from oil accumulations under the influence of relatively high temperatures in oxidizing conditions.Homogenization temperatures for aqueous/brine inclusions in quartz within the Dukla and Silesian units (Polish and Ukrainian segments) are between 125 and 183.9 °C, while salinities are low in the interval of 0.2–5.5 wt% NaCl eq. The inclusions in calcite homogenize at higher temperatures of almost 200 °C and the brine displays higher salinity than the fluid in the quartz. Two quartz generations may be distinguished by inclusion and isotope characteristics and the macroscopic diversity. Oil inclusions homogenize at 95 °C. One phase inclusions in quartz contain methane, CO2 and nitrogen in variable proportions.

Ecological development of Lake Donggi Cona, north-eastern Tibetan Plateau, since the late glacial on basis of organic geochemical proxies and non-pollen palynomorphs

Organic geochemical proxy data from surface sediment samples and a sediment core from Lake Donggi Cona were used to infer environmental changes on the northeastern Tibetan Plateau spanning the last 18.4 kyr. Long-chain n-alkanes dominate the aliphatic hydrocarbon fraction of the sediment extract from most surface sediment samples and the sediment core. Unsaturated mid-chain n-alkanes ( nC 23:1 and nC 25:1) have high abundances in some samples, especially in core samples from the late glacial and early Holocene. TOC contents, organic biomarker and non-pollen-palynomorph concentrations and results from organic petrologic analysis on selected samples suggest three major episodes in the history of Lake Donggi Cona. Before ca. 12.6 cal ka BP samples contain low amounts of organic matter due to cold and arid conditions during the late glacial. After 12.6 cal ka BP, relatively high contents of TOC and concentrations of Botryococcus fossils, as well as enhanced concentrations of mid-chain n-alkanes and n-alkenes suggest a higher primary and macrophyte productivity than at present. This is supported by high contents of palynomorphs derived from higher plants and algae and was possibly triggered by a decrease of salinity and amelioration of climate during the early Holocene. Since 6.8 cal ka BP Lake Donggi Cona has been an oligotrophic freshwater lake. Proxy data suggest that variations in insolation drive ecological changes in the lake, with increased aquatic productivity during the early Holocene summer insolation maximum. Short-term drops of TOC contents or biomarker concentrations (at 9.9 cal ka BP, after 8.0 and between 3.5 and 1.7 cal ka BP) can possibly be related to relatively cool and dry episodes reported from other sites on the north-eastern Tibetan Plateau, which are hypothesized to occur in phase with Northern Hemisphere cooling events.

Changes in organic matter of selected Miocene lignites and embedded sediments caused by microbial desulphurisation

Changes caused by microbial desulphurisation of low-maturity organic matter were investigated. Lignites and embedded sediments (Rr ca. 0.20–0.30%) with high organic matter content from the Bełchatów, Turów and Kazimierz open cast mines (Poland) with variable mineral content and belonging to various lithotypes were desulphurised using Thiobacillus ferrooxidans and Thiobacillus thiooxidans. Extracts of crude (i.e. not desulphurised) and desulphurisated samples were separated into fractions of aliphatic, aromatic and polar compounds by preparative layer chromatography. Aromatic and aliphatic compound fractions were analysed by gas chromatography–mass spectrometry (GC–MS). There are several trends in changes in the composition of extracts that roughly correspond to results of biodegradation described for other types of organic matter like crude oils or bituminous coals such as significant decrease in the extract yields of desulphurised coals and a partial or total removal of several compound groups. Distributions and concentrations of n-alkanes are particularly changed, with short-chain compounds n-C13–n-C22 affected to the highest extent. Cyclic terpenoids, such as sesquiterpanes and diterpanes, were also removed, even from the xylithe extract composed in 90% of 16α(H)-phyllocladane. Pentacyclic triterpanes distributions were not affected significantly, however their concentrations are lower in most of desulphurised samples than in the crude ones. Biodegradation accompanying desulphurisation shows much lower selectivity than that taking place in the nature. Despite the fact that aliphatic hydrocarbons were not removed from the extracts, aromatic hydrocarbons distributions are strongly affected, with total or partial naphthalene and phenanthrene derivatives removal. The values of geochemical indices are also affected by desulphurisation. The results indicate that microbial desulphurisation can significantly influence organic matter of lower maturity. Thus such changes should be taken into account when the process is considered to be applied in industry.

Stable hydrogen isotope ratios of n-alkanes in atmospheric aerosols from Okinawa, Japan

Molecular compositions of n-alkanes and their stable hydrogen isotope ratios (δD) were studied in atmospheric aerosols collected from Cape Hedo, Okinawa, Japan, to better understand the long-range atmospheric transport of organic aerosols from the Asian continent. The δD values of the C22– C33 n-alkanes range from –201 to –115‰, being similar to those of typical fossil fuels and contemporary higher plant leaf waxes in Far East Asia. A correlation between the δD values and the carbon preference index (CPI) suggests that these n-alkanes originated from fossil fuel combustion residues and/or terrestrial higher plant waxes. The concentrations of fossil fuel-derived n-alkanes increased from mid-November 2009 to February 2010, which is consistent with the enhanced emission of coalburning aerosols during the winter in China. δD values of the fossil fuel-derived n-alkanes (–174 ± 7‰) in the atmospheric aerosols from Okinawa are much lower (by up to 95‰) than those from Tokyo and Sapporo, Japan, suggesting that they are derived from multiple sources in East Asia and are delivered by complex transport processes.

Characterisation and accumulation of squalene and n-alkanes in developing Tunisian Olea europaea L. fruits

Summary The present investigation was carried out for the analysis of hydrocarbon compounds of Tunisian Meski olives. The hydrocarbon fraction of the oils was found to contain twelve n-alkanes (C22–C36) and squalene. Results from the quantitative characterisation of the oils revealed that squalene was the most abundant hydrocarbon compound, at all development stages of Meski olive, accounting for more 92% of total hydrocarbons. Pentacosane (C25), heptacosane (C27) and tricosane (C23) represented the major compounds of n-alkanes. The highest accumulation of n-alkanes and squalene was observed at early stages of olive development [before 21st week after the flowering date (WAFD)]. The greatest decrease of these components occurred between 21st and 26th WAFD of the olives. At complete maturity of the fruit, the level of squalene and total n-alkanes was 126.52 and 9.13 mg per 100 g oil, respectively. Hence, the content of n-alkanes and squalene was remarkably influenced by the ripeness process of olive.

Review of Microbial Processes in the Near-Surface Environment and Their Implications for the Chemical Fingerprinting of Hydrocarbon Fuels

The chemical composition of middle-distillate fuels released in the subsurface environment is predominantly affected by biochemical processes resulting in selective degradation of hydrocarbons by indigenous microorganisms. The resulting progression in pattern recognition-based fingerprints depends on the composition of the hydrocarbon product, parameters of the product release (e.g., quantity and rate of release) and environmental conditions. The changes for saturated hydrocarbons follow a common sequence of removal of different compound classes: n-alkanes > isoalkanes > alkylcyclohexanes, with a systematic relationship between decreasing relative degradation rates and increasing chain length. However the timescale of these transformations is defined by the subsurface redox condition. Aerobic biodegradation of saturated hydrocarbons can be observed on a relatively short timescale of years to decades, whereas anaerobic degradation is a much slower process. The fact that aerobic biodegradation produces measurable changes in n-alkane concentrations within this timescale makes it a logical option for evaluating time elapsed since a fuel release into the subsurface environment. This paper provides the synopsis of major modes and pathways of biodegradation processes in the near-surface environment and their effect on the temporal changes in the fingerprints of middle-distillate fuels. In particular, a linear decrease in n-alkane concentrations with time allows for the time of fuel release estimates, utilizing the zero-order kinetics model for the Christensen and Larsen method. This model also allows for establishing applicability limits of this approach. The model is relevant only for hydrocarbon contamination in unsaturated (vadose) zone soil where the availability of sufficient concentration of molecular oxygen favors aerobic biodegradation.

Hydrochemical and Sediment Biomarker Evidence of the Impact of Organic Matter Biodegradation on Arsenic Mobilization in Shallow Aquifers of Datong Basin, China

Biomarker and hydrochemical characteristics of geogenic arsenic-contaminated aquifers at Datong Basin, northern China, were analyzed to better understand the impact of organic matter (OM) biodegradation on arsenic enrichment in groundwater. The hydrochemical characteristics of high arsenic groundwater from the Datong Basin indicate that arsenic mobilization and iron and manganese oxide/hydroxide reduction were controlled by biodegradation of OM. The elevated value of alkalinity produced by microbial oxidation of OM is another important factor for arsenic mobilization via competitive sorption. Bulk geochemistry of the sediments shows that arsenic has close correlation with iron and manganese, indicating iron- and manganese-bearing minerals could be the major pools for arsenic. Results of biomarker analysis reveal that all the sediments contained natural petroleum-sourced hydrocarbons which may have undergone biodegradation, as suggested by the carbon preference index, C29 sterane, and the distribution pattern of hopanes. The presence of unresolved complex mixtures in all samples also indicates the natural petroleum origin of hydrocarbons and the effect of biodegradation. At some depths (5.4–11.8, 31–33.2, and 40–48.4 m below the land surface), the samples have low n-alkane content and no odd-over-even predominance, suggesting that indigenous microbes within the aquifer can preferentially remove the petroleum-sourced n-alkanes. The bioavailability of organic carbon is very important to promote the microbially mediated reductive dissolution of iron oxides/hydroxides and subsequent arsenic release from aquifer sediment into groundwater.

The impact of short rotation coppice on the concentrations of aliphatic soil lipids

The aim was to investigate how short rotation coppice (SRC) on arable soil in Northern Germany altered the concentrations of soil lipids, and thus, soil organic matter (SOM) quality. The concentrations of organic C and aliphatic lipids were determined in the litter and underlying soil layers under two willow (Salix caprea × viminalis clone 6, S. viminalis clone 78–183) and two poplar (Populus trichocarpa × deltoides cv. Beaupre, P. nigra × maximowiczii cv. Max 4) clones at a 14-year-old SRC and a permanent arable reference site. High organic C concentrations in the topsoil under S. viminalis and P. trichocarpa × deltoides agreed with high concentrations of long C-chain saturated n-alkanoic acids, n-alkanols and n-alkanes. These disproportionally higher concentrations of long C-chain saturated n-alkanoic acids (factor 3.6) and n-alkanols (factor 3.8) under S. viminalis and of n-alkanols (factor 3.9) under P. trichocarpa × deltoides than in an arable reference treatment indicated a lower microbial decomposability and, thus, a clone-specific accumulation of these SOM constituents. The clone-specific enrichments in long C-chain saturated n-alkanoic acids, n-alkanols and n-alkanes indicate that clone selection may be an approach to additional long-term storage of atmosphere CO2 in the form of stable SOM under SRC.