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The effects of alkyl glycoside and alcohol ether glycoside alone on the interfacial tension between n-alkanes and Liaohe crude oil and on the interfacial tension in a composite system were studied by using a rotary drop interfacial tensimeter with the addition of ethylene oxide group (EO). The effects of mass fraction of surfactant, concentration of univalent and bivalent ions and EO group on dynamic interfacial tension of the system were investigated. The results show that the two glycoside surfactants can produce strong synergistic effect with sodium dodecylbenzene sulfonate, and the EO chain can adjust the hydrophilic and oleophilic balance of the surfactants, so that the surfactants are more closely arranged at the interface. The increase of salinity can compress the double electron layer, make the interfacial molecules closely arranged, and reduce the interfacial tension. Under proper salinity conditions, the mixed surfactant system can produce ultra-low interfacial tension with Liaohe viscous oil. [ABSTRACT FROM AUTHOR]

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Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The mechanism of hydroisomerization of alkanes was introduced, including the shape selectivity of zeolite and the hydroisomerization reaction process of n-alkanes on bifunctional catalysts. The effects of the characteristics such as pore size, crystal particle size, acid strength, acid type, metal type and dispersion on the isomerization of alkanes were reviewed. The results showed that the yield of isomerization products can be improved by selecting zeolite with appropriate pore size, high acid content and acid strength. The highly dispersed and evenly distributed metals on the bifunctional catalyst are beneficial to the alkane isomerization reaction. The synergistic effect between metal and acid on catalysts, including the ratio of metal center to acid center and the distance between metal center and acid center, was discussed. It was suggested that the appropriate ratio and distance between metal and acid is the key to improving the activity of bifunctional catalysts. [ABSTRACT FROM AUTHOR]

The source rock and crude oil from the Shahejie Formation in the Dongying Sag of the Bohai Bay Basin were studied. Hydrogen isotopic compositions of n-alkanes from different sedimentary environments were determined using a combination of gas chromatograph, GC/TC interface and an isotope mass spectrometer. In the upper section of the fourth member of Shahejie Formation, the hydrogen isotopic composition of source rocks was heavy, ranging from -161‰ to -111‰. While the hydrogen isotopic composition of source rocks in the lower section of the third member of Shahejie Formation was relatively lighter, ranging from -186‰ to -134‰. The results suggested that from brackish water to saline water sedimentary environment, the hydrogen isotope value shifted toward heavier composition following the increasing of salinity in water. The difference of hydrogen isotopic composition was relatively smaller for samples with large maturity differences. The results indicated that the influence of maturity on hydrogen isotopes of a single hydrocarbon was relatively smaller in the range of the normal oil generation window, which was mainly related to the source of parent material and the sedimentary environment. The characteristics of hydrogen isotopic composition of n-alkanes could provide an important scientific basis for the correlation of oil and source rock and the identification of parent material source and paleosedimentary environment.

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In response to the growing problem of soil pollution in the Bahe River basin of Xi'an, gas chromatography-mass spectrometry was used to analyze the surface of the main trunk of the Bahe River in Xi' an, the n-alkanes in soil samples were measured, and the contents, composition, distribution characteristics and sources of the n-alkanes were studied. The results show that the n-alkane carbon chain length ranged from C1~ C:31 in the soil samples from the Rahe River. The chromatograms is mostly unimodal, and a few are bimodal. In general, the peaks from C14 to C20 are higher, the peaks of C28 and C31 are the highest, and the main peak carbon is C31. The n-alkane content in the soil ranged from 3.45 µg/g to 6.35 µg/g, the average concentration is in the middle reaches of the Rahe River is the highest at 5.93 µg/g, and the lowest average concentration in the lower reaches of the Rahe River 3.92 µ/g, upstream the average concentration is centered at 4. 53 µg/g. Compared with other cities at home and a broad, there is a certain amount of soil pollution. Source analysis based on n-alkanes shows that n-alkanes in the soil are a mixed source, which has a strong input advantages of higher plants, indicating that the soil is not only affected by the type and quantity of vegetation in the area, but also interacts with human activities and petroleum hydrocarbon combustion processes. It is suggested that control of point source pollution and optimization of land use types facilitate the protection of the ecological environment of the Rahe river basin. [ABSTRACT FROM AUTHOR]

The extraction procedure using solvent mixtures has been used to elute n-alkanes adsorped by 5Å molecular sieve and subsequent stable carbon isotope ratio analysis of individual n-alkanes. However, a 5Å molecular sieve may catalyze the hydrogen exchange of organic molecules during long-term heating. Therefore, the usage of this method for hydrogen isotopic analysis needs to be evaluated. Two different types of crude oil saturated hydrocarbon and n-alkanes mixed standard samples were used as the object for this study. The extraction method using cyclohexane and n--heptane solvent mixtures and another method evolving the digestion with hydrofluoric-acid and solvent extraction were both used to elute adsorbed n-alkanes by the 5Å molecular sieve. The separation efficiency of the two methods was compared, and both carbon and hydrogen isotopes of obtained n-alkanes have been analyzed. Results show that the two methods enable excellent separations of n-alkanes, and yield variations of the hydrogen isotope ratios smaller than 4‰, within uncertainty. The average recovery of n-alkanes obtained by three-time solvent extraction was 58%, whereas that obtained by hydrofluoric acid dissolution and solvent extraction was 68%. Although cyclohexane and n-heptane solvent mixture has lower extraction efficiency and involves multiple heating processes, these two factors do not result in significant fractionation or exchange of hydrogen isotopes, indicating that this method can be applied to the separation and purifying of n-alkanes and subsequent compound-specific hydrogen isotopic analysis.

The extraction procedure using solvent mixtures has been used to elute n-alkanes adsorped by 5Å molecular sieve and subsequent stable carbon isotope ratio analysis of individual n-alkanes. However, a 5Å molecular sieve may catalyze the hydrogen exchange of organic molecules during long-term heating. Therefore, the usage of this method for hydrogen isotopic analysis needs to be evaluated. Two different types of crude oil saturated hydrocarbon and n-alkanes mixed standard samples were used as the object for this study. The extraction method using cyclohexane and n-heptane solvent mixtures and another method evolving the digestion with hydrofluoric-acid and solvent extraction were both used to elute adsorbed n-alkanes by the 5Å molecular sieve. The separation efficiency of the two methods was compared, and both carbon and hydrogen isotopes of obtained n-alkanes have been analyzed. Results show that the two methods enable excellent separations of n-alkanes, and yield variations of the hydrogen isotope ratios smaller than 4‰, within uncertainty. The average recovery of n-alkanes obtained by three-time solvent extraction was 58%, whereas that obtained by hydrofluoric acid dissolution and solvent extraction was 68%. Although cyclohexane and n-heptane solvent mixture has lower extraction efficiency and involves multiple heating processes, these two factors do not result in significant fractionation or exchange of hydrogen isotopes, indicating that this method can be applied to the separation and purifying of n-alkanes and subsequent compound-specific hydrogen isotopic analysis. [ABSTRACT FROM AUTHOR]

In order to accurately identify sediment sources in the gully and hilly zones of the Loess Plateau, this study was used a composite fingerprinting method that was based on two types of fingerprint factors (14 physicochemical properties and 23 biomarker properties (n-alkanes)) with source samples and sediments derived from check dam. The results showed that, neither the individual physicochemical properties nor biomarker properties cannot effectively identify sediment sources. The physicochemical properties were showing the limitation in identifying forest and cropland, and the n-alkanes were showing the limitation in identifying the gully. However, the optimum composite fingerprint consisted of three physicochemical properties and three biomarker properties (CPI, Ca, TP, C20, C29 and Fe) could correctly distinguish 90.5% of the samples. The results showed that in the study area, gully was the main sediment source in this catchment, reaching 60.8%, while the cropland contributed 20.7% of the sediment, and forest and grassland contributed 11.3% and 7.1%, respectively. This research demonstrates that using the composite fingerprint consists of traditional fingerprint properties and biomarkers to identify the sediment source are more accurate, it would be suitable for the area where the geologic variations of a study area are small. The study is meaningful for designing sediment management and soil erosion control strategies in Loess Plateau. [ABSTRACT FROM AUTHOR]

The section of 1 420 cm lake sediment from Xianghai in the western of Songnen Plain was investigated. According to the AMS 14C dating, the chronology of lake sediment since Last Deglaciation was established; combined with the types of sediment and the abundance of organic matter, molecular organic geochemical characteristics including carbon isotopic compositions of n-alkanes and long-chain n-alkanes in the samples were analyzed; compared with the climatic indicators of sediment core, the changes of paleovegetation and paleoclimate since Last Deglaciation were evaluated. The results show that the organic matters in lake sediment are mainly derived from algae and higher plant according to the distribution of n-alkanes from lake sediment in Xianghai; the n-alkanes exhibit strong odd-carbon number predominance, and the main peak of high carbon number of n-alkanes is nC31, so that the organic matters are mainly derived from terrestrial higher plants, especially herbaceous higher plants; the carbon isotopic compositions of long-chain n-alkanes (nC27, nC29 and nC31) are positive in whole, and the main higher vegetation type in the lake is C3 plant dominantly by the means of binary pattern, and the relative biomass of C4 plant increases from Last Deglaciation to the megathermal of Holocene; the change of climate fluctuates since Last Deglaciation, and the climatic and environmental changes in the study area can be divided into five stages including cold and dry in Last Deglaciation, cold and wet in Early Holocene, warm and dry in the early megathermal of Holocene, warm and wet in the late megathermal of Holocene, and warm-cool and drying in Late Holocene. [ABSTRACT FROM AUTHOR]

Non-road diesel vehicle exhaust is an important emission source that affects air quality in China, yet knowledge regarding its chemical composition and potential influence factors remains limited. Six typical forklifts were selected to study the effect of diesel particulate filters (DPF) on the emission characteristics of volatile organic compounds (VOCs) and n -alkanes using online monitoring of gaseous components combined with offline analysis. The results showed that oxygenated volatile organic compounds (OVOCs), olefins, alkanes, aromatic hydrocarbons, and halogenated hydrocarbons accounted for 26%-37%, 16%-36%, 19%-22%, 13%-21%, and 4%-7% of the measured VOCs in forklift exhaust, respectively. The VOCs emission factors of low-power and high-power forklifts were(2.47±0.33)g·kg -1 and (1.48±0.24)g·kg -1 , respectively. The forklift exhaust emission factors of total VOCs without and with DPF were(1.94±0.58)g·kg -1 and (2.08±0.79)g·kg -1 , respectively. Our results showed that DDF exerted minor impact on VOCs emission. However, it is worth noting that DPF can efficiently remove some types of OVOCs components. For example, the emission factors of acetaldehyde and acetone of the forklifts with DPF were reduced by 19% and 26%, respectively, compared to that of those without DPF. The carbon numbers of n -alkane fractions showed a bimodal distribution of C 7 -C 17 and C 24 -C 31 , respectively, with C 15 being the dominant peak carbon. The average emission factors of n -alkanes were (115±34) mg·kg -1 (without DPF) and (53.7±19)mg·kg -1 (with DPF), respectively, with a decrease of 53%, indicating that DPF can effectively reduce the emission of n-alkane in the exhaust of forklifts. Our results can provide scientific support for the precise control of non-road construction machinery exhaust emissions and the further improvement of regional air quality.

To investigate the variations and sources of n -alkanes and sugars in Taian City during summer, PM 2.5 samples were collected from July 22 to August 19, 2016. The identified n -alkane and sugar sources were investigated using a principal component analysis (PCA) multiple linear regression (MLR) model and a backward trajectory model. The results showed that the mass concentrations of PM 2.5 during summer were (37.2±11.5) μg·m -3 . The mass concentrations of n -alkanes were (83.3±34.7) ng·m -3 , the carbon preference index (CPI) was 1.83, and the relative contribution of wax n -alkanes was 34.7%-69.4%, suggesting that contributions from terrestrial plants were more significant in Taian City. The results showed that the mass concentrations of sugars in Taian City during summer were (73.4±46.6) ng·m -3 . Levoglucan, galactosan, and mannosan were the main saccharides, accounting for 64.0%, 7.1%, and 6.3% of the total concentrations of sugars, respectively, indicating that biomass burning is much more significant in Taian City. The results of the PCA-MLR model suggested that n -alkanes and sugars in Taian City during summer were mostly from terrestrial plants, coal burning and biomass burning. The backward trajectory model showed that the pollution mostly came from the native sources of Shandong province and the inland cities in the south.

To investigate the pollution characteristics and sources of organic aerosols at a background site of the Yangtze River Delta, day- and night- PM 2.5 samples were collected from May 30 th to August 15 th , 2018 in Chongming Island, China and measured for their normal alkanes ( n -alkanes) and polycyclic aromatic hydrocarbons (PAHs) content employing a GC-MS technique. Concentrations of PM 2.5 , n -alkanes, and PAHs during the entire sampling period were (33±21) μg·m -3 , (26±44) ng·m -3 , and (0.76±1.0) ng·m -3 , respectively. During the entire campaign, 35% of the collected PM 2.5 samples were of a particle loading larger than the first grade of the China National Air Quality Standard (35 μg·m -3 ), suggesting that further mitigation with respect to air pollution in Chongming Island remains imperative. In the period with a PM 2.5 concentration higher than 35 μg·m -3 , which was classified as the pollution period, concentrations of n -alkanes and PAHs were one order of magnitude higher than those in the period with PM 2.5 less than 15 μg·m -3 , which was classified as the clean period. During the entire campaign, OC was higher in the daytime than in the nighttime, mainly due to the daytime photooxidation that enhanced the formation of secondary organic aerosols. During the pollution period, concentrations of EC and other pollutants were higher in the nighttime than in daytime, mainly due to the transport of the inland pollutants by the nighttime land breeze. Such a diurnal difference was not observed for the pollutants in clean periods, mainly due to the relatively clean breeze from East China Sea that diluted the air pollution. Diagnostic ratios showed that 67% of n -alkanes in PM 2.5 was derived from fossil fuel combustion. PMF analysis further showed that during the pollution period, vehicle exhausts and industrial emissions were the largest sources of PAHs, both accounting for 51% of the total in PM 2.5 . In contrast, during the clean periods ship emissions were the largest source, contributing about 45% of the total PAHs, exceeding the sum (38%) of vehicle and industrial emissions.

To investigate molecular composition, mass concentrations, and sources of n -alkanes and sugars which are adsorbed in ambient particulate matters in Liaocheng City during winter, PM 2.5 samples were collected from January 17 to February 15, 2017 at Liaocheng University. 19 kinds (C 18 -C 36 ) of n -alkanes and 10 kinds of sugars were determined using GC-MS. The identification of n -alkane and sugar sources were investigated using principal component analysis (PCA). The results showed that the mass concentrations of total n -alkanes in PM 2.5 during the winter were (456.9±252.5) ng·m -3 . During the haze period, the concentrations of n -alkanes were two times higher than those on clear days. Additionally, the concentrations of n -alkanes during fireworks event I and fireworks event Ⅱ were 0.9 times and 1.2 times higher than those on clear days. During the sampling period, the Carbon preference index (CPI) was 1.2±0.1, and the contribution from plant wax concentrations for n -alkanes (% Wax C n ) was between 3.1%~36.0%, indicating that fossil fuels were the major source of n -alkanes in Liaocheng City during the winter. The mass concentrations of saccharides in PM 2.5 during the winter were (415.5±213.8) ng·m -3 . Levoglucosan was the most abundant species, followed by galactosan and mannosan, which accounted for more than 91.6% of total saccharides, indicating that biomass burning was much more significant in Liaocheng City. PCA further suggested that n -alkane and saccharide compounds in atmospheric aerosol during the winter in Liaocheng City were primarily derived from fossil fuel and biomass burning.

The on-road emissions of typical alkanes from 11 heavy-duty diesel vehicles with different emission standards (from China Ⅰ to China Ⅳ) were tested using a portable emission measurement system(PEMS) and quantified by gas chromatography-mass spectrometry (GC-MS). Our aim was to analyze the emission characteristics of typical alkanes in heavy-duty diesel vehicle exhaust. The results show that the emission standard significantly affected the emission factors (EFs) of n -alkanes and hopanes. Vehicles with higher emission standards had lower EFs. Compared with China Ⅰ vehicles, the total EFs of n -alkanes, 17 α (H),21 β (H)-C30 hopane (C30-hopane), and 22S- and 22R-17 α (H),21 β (H)-homohopane (22S-C31 and 22R-C31 homohopane) from China Ⅳ vehicles were significantly reduced by 72.23%, 64.95%, 70.78%, and 74.68%, respectively. The peak carbon numbers of gaseous n -alkanes were 17 to 18, while they were 18 to 21 in particulate n -alkanes. The 22S-C31 homohopane/(22S-C31 homohopane + 22R-C31 homohopane) ratios ranged from 0.46 to 0.56, with an average of 0.50, which conform to the characteristics of hopanes in petroleum. The total EFs of n -alkanes had a good linear relationship with the total EFs of C30-hopane, and the R 2 was 0.9268. Furthermore, the driving conditions had a great influence on the emissions of n -alkanes and hopanes. Specifically, the EFs of n -alkanes and hopanes on non-highway roads were 1.69 to 2.42 times greater than those on highways.

Hydrocarbons emitted by human activities probably constitute the largest class of contaminants that are present in coastal areas, because of widespread use of fossil fuels for power generation and logistics, and accidental spillages. The chemical composition of hydrocarbon mixtures found in the marine environment allowed the identification of relative contributions of different natural and anthropogenic sources. Identification of these hydrocarbons, especially n -alkanes, could act as tracers for the possible sources. To evaluate n -alkanes concentrations with emphasis on source analysis, surface water without visible oil was collected from the cruise in April 2016. Determination and quantification were performed by solvent extraction and gas chromatography-mass spectrometry. Various molecular diagnostic parameters were used to assess the contribution of different sources and origin of n -alkanes in surface seawater of Jiaozhou Bay. Concentrations of total dissolved n -alkanes(C 11 -C 37 ) were between 1.756-39.09 μg·L -1 with a high carbon number predominance profile without odd-even carbon number preference. The n -alkane concentrations varied spatially depending on the distance away from main input sources and the ability of water exchange. It was at a higher concentration in the northeast and west coastal areas, as well as the mouth of Jiaozhou Bay. And concentrations were relatively lower in the inner area and outside of Jiaozhou Bay. In the sea area with strong water exchange, concentrations of total n -alkanes were around 2.196 μg·L -1 , which could be considered as the environmental background level of n -alkanes in Jiaozhou Bay. Those n -alkanes were dominated with C 24 , with a slightly odd carbon number preference in low carbon n -alkanes and an even carbon number preference in high carbon n -alkanes. The values of CPI for the whole range of n -alkanes series, low carbon n -alkanes, and high carbon n -alkanes were 0.949, 1.026, and 0.980, respectively. Diagnostic indices and curves indicated that the dominant inputs of those n -alkanes were from marine biogenic input such as algae and marine bacteria. The concentration profiles of n -alkanes in other areas were characterized by no odd-even predominance in the range of C 21 -C 33 with peaks center at C 24 which were indicative of anthropic contributions as emission sources. N -alkanes dominating with anthropic sources comprised a high proportion(83.7%) of total n -alkanes. Activities of harbors and ships were the main contributors of Jiaozhou Bay n -alkanes. Physical processes, such as evaporation and dilution, were the principal weathering mechanisms. Because of its sufficient environmental capacity, Jiaozhou Bay was still moderately contaminated with petroleum.

Sediment columns in the southeast and east of Dianchi Lake were taken as the object of the study to determine ages by 210 Pb dating method.The contents and sediment fluxes of total organic carbon (TOC) and n -alkanes of the sediments were investigated,and organic sources were tracked according to the relevant indexes of n -alkanes.The results indicated that TOC contents and sediment fluxes of two sampling sediments both presented an increasing trend on the whole;Sediment fluxes of n -alkanes varied as three stages:increasing period,decreasing period and re-increasing period.When the sediment fluxes of n -alkanes and TOC both went up,it showed that they had the same sources:sediments in the lake and carried by the rivers;From 1980s to the end of 20 th century,sediment fluxes of n -alkanes were going down while those of TOC were going up.This result means there was a big difference in the sources of n -alkanes and TOC.The bacteria and algae in the lake made a great contribution to n -alkanes while TOC was mainly influenced by sediments in the lake and carried by the rivers. n -alkanes of the two sampling sites both ranged from C 12 to C 35 .Based on the basic features and relevant indexes of n -alkanes,we proposed that emergent plants made big contributions to the sources of organic matter in the sediments of Dianchi Lake,simultaneously,bacteria and algae had significant contributions to the sources of organic matter in shallow depth of Dianchi Lake.

In order to study the composition and environment significance of the organic matter in Lake Dianchi, samples from two sediment cores from the northern and southern parts of the lake were collected in July, 2014. Meanwhile, the vertical distributions of total organiccarbon (TOC), total nitrogen (TN), n -alkanes fractions were investigated. The results showed that ① the concentrations of TOC and TN had been clearly increasing since the 1970s, which implied that the primary productivity of Lake Dianchi was continuously enhanced; ② The values of the parameter n -C 27 / n -C 31 , P aq and CPI indicated the alternation between herbs and woody plants from the bottom up in Lake Dianchi sediments. Besides, the high carbon number of organic matter in sediments mainly originated from endogenous submerged floating and large plants; ③ The index of C/N and distribution characteristics of n -alkanes suggested differences in the various sources of organic matter in different lakes. In detail, organic matter came from terrigenous organic matter of anthropogenic sources and endogenous bacteria in the sediments of northern Dianchi, while organic matter was derived from endogenous aquatic and terrestrial higher plants mixed source in the sediments of southern Dianchi. Finally, it is worthwhile to emphasize further research on organic matter in different lakes of Lake Dianchi.