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Over 1/3 of the Earth's human population relies on dryland ecosystems for food and water resources. While these ecosystems are highly sensitive to changes in climate, we lack observational data as to how changes in hydrology influences plant communities. Paleoecological data for southern Arabia show woodland communities transitioned to more dry-adapted herbaceous plants, which suggests rainfall decreased across the Holocene. To assess relationships between hydrology and ecology, we employed leaf wax n-alkane distributions, 513Cwax, and 5Dwax records from rock hyrax (Procavia capensis) middens in Dhofar, Oman. The biomarker properties allowed reconstruction of changes in C3/C4 vegetation and local moisture availability, in tandem with community changes represented by a published pollen record. To constrain interpretations, n-alkane analyses were conducted on herbarium specimens of leaves collected in Dhofar. For the modern specimens, xeric plants typically contained longer homologues than mesic plants. Across the fossil middens (4,038-109 cal yrs BP), the proportions of plant-wax homologues do not show major changes, and thus do not suggest a shift between xeric versus mesic plants. Similarly, 513Cwax values indicate little or no change in the distributions of C3 and C4 vegetation. Limited 5Dwax data from the middens confirm overall drying occurred into the late Holocene, punctuated by a wetter pulse at ~1.6 ka. Taken together, plant wax distributions and isotope data indicate changes in moisture availability across the late Holocene did not alter the structural composition of the plant communities and that the proportion of C3/C4 vegetation remained stable. We infer vegetation changes associated with late Holocene drying involved reshuffling of community composition and not major changes in vegetation structure. Additionally, this study demonstrates that leaf wax n-alkanes from rock hyrax middens provide a method to reconstruct changes in climate and vegetation in dryland ecosystems where other archives are scarce. [ABSTRACT FROM AUTHOR]

Oil production facilities exercise severe technogenic impact on dry-steppe chestnut soils (Kastanozems) of the Tamsagbulag oilfield. This paper estimates the degree of soil contamination with petroleum hydrocarbons and mechanical disturbance of the soil cover. It has been established that technogenic impact on chestnut soils due to oil production is manifested in a high variability of physicochemical parameters in the surface horizon: aqueous extract mineralization varies from 32.5 to 325.0 mg/L; specific electrical conductivity, from 65.4 to 647.0 μS/cm; while concentration of hydrocarbons (HCs), from 7 to 647 mg/kg. Only in a few cases, HC concentrations exceed the background level established for oil production zones (100 mg/kg) by 3.2 and 6.5 times. The HC proportion in the total organic carbon content (Corg) varies in a wide range: from 0.01 to 6.20%. Gas chromatographic analysis of the molecular-weight distribution of n‑alkanes in the HC composition showed that high molecular weight (C27–C39) homologues with high enough transformation degrees of individual odd-numbered n-alkanes prevail in the surface soil horizon. The proportion of medium molecular weight homologues (∑C22–C25) does not exceed 8% of the total content of n-alkanes. In the soil microbial community, heterotrophic bacteria (HB) predominate among ecological–trophic groups of microorganisms (unicellular bacteria, actinomycetes, and micromycetes); the proportion of oil-oxidizing bacteria in the total HB count reaches 9.1–39.3%. Degradation of petroleum HCs is accompanied by the formation of a wide range of volatile organic compounds. The quantitative and qualitative composition of oil components in the surface horizon is determined by two processes: HC vertical migration and transformation. Together, these processes offset the accumulation of oil in the surface soil horizon. [ABSTRACT FROM AUTHOR]

The current paper deals with new metabolites of different groups produced by Azotobacter chroococcum XU1. The strain's metabolic diversity is strongly altered by different factors, and some secondary metabolites are being reported for the first time for this species. As an abiotic/biotic stress response, the strain produced a broad spectrum of indole ring-containing compounds, n-alkanes (eicosane, heneicosane, docosane, tetracosane, and hexacosane), alkanes (7-hexyl eicosane and 2-methyloctacosane), saturated fatty acids (hexanoic and octanoic acids), esters (hexadecanoic acid methyl and pentadecanoic acid-14-methyl-methyl esters), and amides (9-Octadecenamide, (Z)- and 13-Docosenamide, (Z)-). Furthermore, to mitigate the abiotic stress the strain actively produced exopolysaccharide (EPS) to biosorb the Na+ ions. Apart from these metabolites, A. chroococcum XU1 synthesized lactones, namely 1,5-d-gluconolactone and d, l-mevalonic acid lactone in response to carbon source modification. [ABSTRACT FROM AUTHOR]

Many continental paleoclimate archives originate from wetland sedimentary sequences. While several studies have investigated biomarkers derived from peat-generating vegetation typical of temperate/boreal bogs (e.g., Sphagnum), only scant information is available on emergent plants predominant in temperate/subtropical coastal marshlands, peri-lacustrine and fen environments. Here, we address this gap, focusing on two wetlands in the Mediterranean (Nisí fen and Tenaghi Philippon, Greece). We examined the concentration, homologue distribution, and hydrogen stable isotopic composition (δ[sup 2]H) of leaf wax n-alkanes in 13 fen plant species, their surrounding soil, and surface water during the wet growing season (spring) and the declining water table period (summer). Our findings indicate that local graminoid species primarily contribute to the soil n-alkane signal, with a lesser influence from forbs, likely owing to differences in morphology and vegetation structure. The δ[sup 2]H values of surface and soil water align with local average annual precipitation δ[sup 2]H, reflecting winter-spring precipitation. Consistently, the average δ[sup 2]H of local surface, soil, and lower stem water showed negligible evaporative enrichment, confirming minimal [sup 2]H-fractionation during water uptake. We find that δ[sup 2]H values of source water for wax compound synthesis in local fen plants accurately mirror local annual precipitation. Furthermore, despite differences between leaves and lower stems in n-alkane production rates, their δ[sup 2]H values exhibit remarkable similarity, indicating a shared metabolic substrate, likely originating in leaves. Our net [sup 2]H-fractionation values (i.e., precipitation to leaf n-alkanes) align with those in Chinese highlands and other similar environments, suggesting consistency across diverse climatic zones. Notably, our data reveal a seasonal decrease in the carbon preference index (CPI) in plant samples, indicating wax lipid synthesis changes associated with increased aridity. Additionally, we introduce a new parity isotopic difference index (PID) based on the consistent δ[sup 2]H difference between odd and even n-alkane homologues. The PID demonstrates a strong anticorrelation with plant CPI, suggesting a potential avenue to trace long-term aridity shifts through δ[sup 2]H analysis of odd and even n-alkane homologues in sedimentary archives. While further development of the PID is necessary for broad application, these findings highlight the intricate interplay between plant physiology, environmental parameters, and sedimentary n-alkanes in unravelling past climatic conditions. [ABSTRACT FROM AUTHOR]

High-wax crude oil was treated with ultrasound (sample weight 50 g, frequency 22 kHz, field intensity 8 W/cm2) for 10 min. The ultrasonic treatment led to an increase in the crude oil viscosity, viscous flow activation energy, specific energy of the break of the disperse system, congealing point, pour point, and precipitate amount and to changes in the precipitate structure. The oil fraction of the crude oil, precipitates, and raffinates was analyzed by IR spectroscopy and chromatography–mass spectrometry. The content of high-molecular-mass n-alkanes in oils from the precipitate of the ultrasonically treated crude oil considerably decreases. [ABSTRACT FROM AUTHOR]

Over 1/3 of the Earth’s human population relies on dryland ecosystems for food and water resources. While these ecosystems are highly sensitive to changes in climate, we lack observational data as to how changes in hydrology influences plant communities. Paleoecological data for southern Arabia show woodland communities transitioned to more dry-adapted herbaceous plants, which suggests rainfall decreased across the Holocene. To assess relationships between hydrology and ecology, we employed leaf wax n-alkane distributions, δ13Cwax, and δDwax records from rock hyrax (Procavia capensis) middens in Dhofar, Oman. The biomarker properties allowed reconstruction of changes in C3/C4 vegetation and local moisture availability, in tandem with community changes represented by a published pollen record. To constrain interpretations, n-alkane analyses were conducted on herbarium specimens of leaves collected in Dhofar. For the modern specimens, xeric plants typically contained longer homologues than mesic plants. Across the fossil middens (4,038–109 cal yrs BP), the proportions of plant-wax homologues do not show major changes, and thus do not suggest a shift between xeric versus mesic plants. Similarly, δ13Cwax values indicate little or no change in the distributions of C3 and C4 vegetation. Limited δDwax data from the middens confirm overall drying occurred into the late Holocene, punctuated by a wetter pulse at ∼1.6 ka. Taken together, plant wax distributions and isotope data indicate changes in moisture availability across the late Holocene did not alter the structural composition of the plant communities and that the proportion of C3/C4 vegetation remained stable. We infer vegetation changes associated with late Holocene drying involved reshuffling of community composition and not major changes in vegetation structure. Additionally, this study demonstrates that leaf wax n-alkanes from rock hyrax middens provide a method to reconstruct changes in climate and vegetation in dryland ecosystems where other archives are scarce.

Abstract The aim of this work is to examine the levels, distribution, bases, and hazards of n-alkanes (n-C9 to n-C20) and PAHs in the seawater and sediments around oil production locations in the whole delta region. The variations in the levels of PAHs and n-alkanes in seawater and sediment of the Nile delta coast of the Mediterranean were investigated using GC–MS/MS. The Σn-alkanes residues ranged between 12.05 and 93.51 mg/L (mean: 50.45 ± 17.49 mg/L) and 4.70 to 84.03 µg/g (mean: 31.02 ± 27.995 µg/g) in seawater and sediments, respectively. Total PAHs concentrations ranged between 4.485 and 16.337 μg/L (average: 9.47 ± 3.69 μg/L) and 1.32 to 28.38 ng/g (average 8.61 ± 7.57 ng/g) in seawater and sediment samples, respectively. The CPI (carbon preference index) values fluctuated between 0.62 and 1.72 (seawater) and from 0.234 to 2.175 (sediment), proposing the variation sources of n-alkane in the studied area. PAHs concentrations were lower than the Effective Range Low (ERL) and Effective Range Median (ERM) levels. The Toxic Equivalent Quotient (TEQ) values oscillated between 0.002 and 6.84 ng/L and from 3.72 to 13.48 ng/g for the seawater and sediment samples, respectively. The Ant/(Ant + Phe) ratio in sediment and seawater samples indicated a pyrolytic source while the BaA/(BaA + Chry) ratio indicates petrogenic sources in most of the studied stations.

Previous multi-proxy records have revealed the advantages of well-preserved and long-scale geological archives from the lake sediments of Barkol Lake, which is located at northeast Xinjiang in northwest China. However, the exact organic matter (OM) sources in the sediments and their response to climatic variability still remain unclear in this area. In this study, we present an 8.8 kyr n-alkane record extracted from the sediments in Barkol Lake to explore the OM sources and the relationship between n-alkanes and climatic changes. The results indicate that the n-alkane composition was dominated by long-chain n-alkanes(C27–C31), implying a dominant origination of OM from the terrestrial higher plants and emergent aquatic plants. The n-alkane data further revealed that changes in OM sources were related to the surface erosion-transportation-deposition processes controlled by climatic changes. Lake level changes, which are also regulated by climate conditions, played an important role in impacting OM accumulation. Relatively wetter conditions would result in a rising lake level that favored more aquatic OM and less terrestrial OM input, and vice versa. The regional climate patterns have been generally dominated by alternations of cold-wet and warm-dry episodes over the past ~8.8 kyr. We preliminarily concluded the dynamic changes of OM input and the hydrological changes in Barkol Lake was mainly controlled by SSTs in the North Atlantic region and melting water supply modulated by Eurasian ice sheet. [ABSTRACT FROM AUTHOR]

The upper layer of bottom sediments in the northeastern Kara Sea is studied. It is shown that the sediment composition is dominated by silt, while the percentage of sand increases towards the coast. The organic carbon content (average value 1.1 wt %) is close to the average content in Kara Sea sediments, increasing at deep-sea stations. The linear correlation found between the organic carbon content and surface area of sediments shows adsorption on particle surfaces and is the predominant form of organic matter (OM) accumulation in the sediments. The average n-alkane concentration in the analyzed samples is 1.1 μg/g of sediment; the distribution spectrum is dominated by odd high-molecular homologues of terrigenous origin. [ABSTRACT FROM AUTHOR]

The sources of supply and transformation of organic matter (OM) as it transitions from dissolved form to particulate matter, fluffy layer, and bottom sediments were investigated along a meridional transect from the Lena River delta to the continental slope (in the depth range of 10 to 2390 meters, cruise 63 of the R/V Akademik Mstislav Keldysh, September 2015). The study of OM molecular markers showed that dissolved and particulate organic matter of marine and terrigenous origin biodegrades in the water column and accumulates insignificantly in bottom sediments. Thus, OM from Lena River runoff does not contribute to the formation of OM in bottom sediments in summer. An area of influence of under-ice blooms on the sedimentation process was identified on the outer shelf. [ABSTRACT FROM AUTHOR]

The wet flue gas desulfurization (WFGD) system of coal-fired power plants shows a good removal effect on condensable particulate matter (CPM), reducing the dust removal pressure for the downstream flue gas purification devices. In this work, the removal effect of a WFGD system on CPM and its organic pollutants from a coal-fired power plant was studied. By analyzing the organic components of the by-products emitted from the desulfurization tower, the migration characteristics of organic pollutants in gas, liquid, and solid phases, as well as the impact of desulfurization towers on organic pollutants in CPM, were discussed. Results show that more CPM in the flue gas was generated by coal-fired units at ultra-low load, and the WFGD system had a removal efficiency nearly 8% higher than that at full load. The WFGD system had significant removal effect on two typical esters, especially phthalate esters (PAEs), with the highest removal efficiency of 49.56%. In addition, the WFGD system was better at removing these two esters when the unit was operating at full load. However, it had a negative effect on n-alkanes, which increased the concentration of n-alkanes by 8.91 to 19.72%. Furthermore, it is concluded that the concentration distribution of the same type of organic pollutants in desulfurization wastewater was similar to that in desulfurization slurry, but quite different from that in coal-fired flue gas. The exchange of three organic pollutants between flue gas and desulfurization slurry was not significant, while the concentration distribution of organic matters in gypsum was affected by coal-fired flue gas. [ABSTRACT FROM AUTHOR]

Analysis of plant‐wax biomarkers from sedimentary sequences can enable past environmental and hydrological reconstruction and provide insights into past hominin adaptations. However, biomarker preservation in desert contexts has been considered unlikely given the sparse nature of the vegetation within the landscape. Here we evaluate the preservation of n‐alkanes and fatty acids collected from four depositional sequences associated with archaeological contexts in the Nefud Desert, Saudi Arabia, and the Thar Desert, India. Pleistocene and Holocene samples were selected to understand the effects of age on preservation. The results of molecular distribution patterns and indices, particularly the high carbon preference index and average chain length, show the preservation of plant‐wax biomarkers in both the Holocene and Pleistocene desert sequences, while δ13C values and organic content provide insights into the vegetation contributing to the plant‐wax organic pool. This study provides a baseline for understanding human–environment interactions and for reconstructing changes in arid land habitats of relevance to hominins during the Quaternary. [ABSTRACT FROM AUTHOR]

The aim of this work is to examine the levels, distribution, bases, and hazards of n-alkanes (n-C9 to n-C20) and PAHs in the seawater and sediments around oil production locations in the whole delta region. The variations in the levels of PAHs and n-alkanes in seawater and sediment of the Nile delta coast of the Mediterranean were investigated using GC–MS/MS. The Σn-alkanes residues ranged between 12.05 and 93.51 mg/L (mean: 50.45 ± 17.49 mg/L) and 4.70 to 84.03 µg/g (mean: 31.02 ± 27.995 µg/g) in seawater and sediments, respectively. Total PAHs concentrations ranged between 4.485 and 16.337 μg/L (average: 9.47 ± 3.69 μg/L) and 1.32 to 28.38 ng/g (average 8.61 ± 7.57 ng/g) in seawater and sediment samples, respectively. The CPI (carbon preference index) values fluctuated between 0.62 and 1.72 (seawater) and from 0.234 to 2.175 (sediment), proposing the variation sources of n-alkane in the studied area. PAHs concentrations were lower than the Effective Range Low (ERL) and Effective Range Median (ERM) levels. The Toxic Equivalent Quotient (TEQ) values oscillated between 0.002 and 6.84 ng/L and from 3.72 to 13.48 ng/g for the seawater and sediment samples, respectively. The Ant/(Ant + Phe) ratio in sediment and seawater samples indicated a pyrolytic source while the BaA/(BaA + Chry) ratio indicates petrogenic sources in most of the studied stations. [ABSTRACT FROM AUTHOR]

Simple Summary: Near-infrared spectroscopy (NIRS) has emerged as an accurate and promising alternative to traditional wet chemistry methods in feed and food science. Its applicability extends to estimating concentrations of compounds such as n-alkanes, based on their chemical properties, in various materials, including feed and feces. Analysis of excreta n-alkane patterns can provide insight into the dietary behavior of laying hens, particularly in scenarios where they have access to free-range areas and potentially consume plants from outside sources. Our study attempts to explore extreme cases, such as hens consuming only commercial feed, which result in lower concentrations of n-alkanes in excreta, thus challenging NIRS as a replacement for wet chemistry. Evaluating the accuracy of NIRS in predicting n-alkanes in excreta is critical because of its potential for substantial time and cost savings. Furthermore, it contributes to a deeper understanding of future nutritional strategies for laying hens, particularly in light of external nutritional contributions. N-alkanes offer a promising approach for assessing the nutritional contribution of external sources to the diets of laying hens in free-range production systems. However, traditional laboratory methods, involving extraction, purification and gas chromatographic analysis, are both economically burdensome and time-consuming. Near-infrared spectroscopy (NIRS) is emerging as a viable alternative, with varying degrees of accuracy depending on the chemical nature and concentration of the component of interest. In our research, we focus on the accuracy of NIRS in predicting the concentrations of n-alkanes (C25–C33) in excreta under simulated free-range conditions with two different diets: one containing a commercial feed with minimal n-alkane content and another containing 1% alfalfa on top of the commercial feed. Spectra processing and calibration were tailored for each n-alkane, with NIRS performance influenced by diet type. Notably, plant predictions using NIR-generated data were consistent with laboratory results, despite a slight tendency toward overestimation (3.40% using the NIRS-generated C25-C29-C33 combination versus 2.80% using laboratory analysis). This indicates the potential of NIRS as an efficient tool to assess n-alkanes in excreta of laying hens and, consequently, the nutritional contribution of the free-range environment, providing rapid and cost-effective results. [ABSTRACT FROM AUTHOR]

The associative behavior of n-alkanes in petroleum dispersed systems and its changes under different temperature conditions were studied using dynamic light scattering, as well as optical, electron, and atomic force microscopy. Within the framework of the previously proposed hypothesis about the presence of associates (coacervates) of n-alkanes in crude oil systems, i.e., microparticles with a shell and a specific internal composition and structure, studies of the sizes of the existing structures were carried out at two different temperatures. It was shown that in the studied paraffinic oil system the associates remained even at elevated temperatures. [ABSTRACT FROM AUTHOR]

Simple Summary: Providing better living conditions for laying hens by promoting free-range systems has sparked curiosity about potential alterations in their dietary habits. Understanding these changes can lead to new feeding strategies to meet their nutritional needs. However, this task is challenging due to the inherent complexities of the outdoor environments and variations in plant material breakdown. Our research marks a pioneering step in exploring both qualitative and quantitative methods for assessing plant intake in laying hens using n-alkanes as markers, and demonstrates their viability even at levels of plant material in the diet as low as 1%. It also highlights the need for further research on different sources of n-alkanes, especially in real case studies with different plant and insect species under outdoor conditions. Such studies are essential to provide a deeper understanding of the dietary factors affecting the performance of laying hens in free-range systems. The shift in animal welfare standards towards free-range housing for laying hens in the EU has raised questions about changes in dietary composition. Accurate assessment of outdoor plant material intake is crucial for effective feeding strategies. This study introduces an approach using n-alkanes as markers to determine plant intake in laying hens, involving n-alkane recovery rate assessment, discriminant analysis and linear equation-solving for both qualitative and quantitative assessment, respectively, considering systematic n-alkane combinations. Two diets: a standard commercial diet and a diet incorporating 1% alfalfa were tested. Chemical analyses showed an altered n-alkane profile due to alfalfa inclusion, resulting a recovery rates ranging from 30–44% depending on the n-alkane type and diet. Statistical analysis revealed significant differences in recovery rates among the different alkanes for the same diets and between the diets for the same alkane, together with an interaction between n-alkane carbon chain length and initial concentration in the diet. The method accurately predicted plant inclusion, with a slight overestimation (2.80%) using the combination C25-C29-C33. Accurate qualitative classification of the animals based on fecal n-alkanes profiles was observed. The study successfully demonstrated the utility of n-alkanes for estimating dietary composition, providing a non-invasive approach for future free-range studies. [ABSTRACT FROM AUTHOR]

Many continental paleoclimate archives originate from wetland sedimentary sequences. While several studies have investigated biomarkers derived from peat-generating vegetation typical of temperate/boreal bogs (e.g., Sphagnum), only scant information is available on emergent plants predominant in temperate/subtropical coastal marshlands, peri-lacustrine and fen environments. Here, we address this gap, focusing on two wetlands in the Mediterranean (Nisí fen and Tenaghi Philippon, Greece). We examined the concentration, homologue distribution, and hydrogen stable isotopic composition (δ2H) of leaf wax n-alkanes in 13 fen plant species, their surrounding soil, and surface water during the wet growing season (spring) and the declining water table period (summer). Our findings indicate that local graminoid species primarily contribute to the soil n-alkane signal, with a lesser influence from forbs, likely owing to differences in morphology and vegetation structure. The δ2H values of surface and soil water align with local average annual precipitation δ2H, reflecting winter-spring precipitation. Consistently, the average δ2H of local surface, soil, and lower stem water showed negligible evaporative enrichment, confirming minimal 2H-fractionation during water uptake. We find that δ2H values of source water for wax compound synthesis in local fen plants accurately mirror local annual precipitation. Furthermore, despite differences between leaves and lower stems in n-alkane production rates, their δ2H values exhibit remarkable similarity, indicating a shared metabolic substrate, likely originating in leaves. Our net 2H-fractionation values (i.e., precipitation to leaf n-alkanes) align with those in Chinese highlands and other similar environments, suggesting consistency across diverse climatic zones. Notably, our data reveal a seasonal decrease in the carbon preference index (CPI) in plant samples, indicating wax lipid synthesis changes associated with increased aridity. Additionally, we introduce a new parity isotopic difference index (PID) based on the consistent δ2H difference between odd and even n-alkane homologues. The PID demonstrates a strong anticorrelation with plant CPI, suggesting a potential avenue to trace long-term aridity shifts through δ2H analysis of odd and even n-alkane homologues in sedimentary archives. While further development of the PID is necessary for broad application, these findings highlight the intricate interplay between plant physiology, environmental parameters, and sedimentary n-alkanes in unravelling past climatic conditions.

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]

As the main global terrestrial ecosystem component, grasslands are extremely sensitive to global climate change. With increasing human activities over the last century, grassland ecosystems have been degraded to different degrees. However, the evolution of lake-grassland ecosystems in recent centuries remains unclear due to the dearth of high-resolution records. Here, we present high-resolution lacustrine sediment grain size, pollen (Artemisia , Myriophyllum), Pediastrum , and n-alkane records from Ganggeng Nur Lake to investigate vegetation, lake evolution, and human effects in semiarid northern China. Four stages were identified from the last ca. 150 years: (1) the natural evolution stage (AD 1870–1945), in which there was a wet climate around Ganggeng Nur and the lake level rose from increased runoff; (2) the human disturbance stage (AD 1945–1967), in which the regional climate got drier and human activities began having a detectable effect on the grassland ecosystem; (3) the human transformation stage (AD 1967–2005), in which a completely arid climate coupled with the implementation of a series of land reclamation policies resulted in a large reduction in grassland areas, extensive soil erosion, exacerbated climate change, and shrinking lake areas; and (4) the posttreatment stage (AD 2005–2018), in which soil erosion was alleviated by policy implementation and a favorable humid climate. [ABSTRACT FROM AUTHOR]

Data on the contents of inorganic (IC) and organic carbon (OC), the genesis of organic matter (OM) and its digenetic transformation in bottom sediments of the Il'd River and bordering areas of the river-reservoir contact zone were obtained. The concentrations of IC and OC along the longitudinal profile of the studied water area varied over a wide range. The maximum concentration of IC was confined to the zone of free flow of the river (0.8–1.0% DW), and for OM it was confined to the zone of the receiver (~10% DW). Based on an analysis of n-alkanes in bottom sediments, three types of OM have been identified: autochthonous, mixed, and predominantly terrigenous, which successively change in the longitudinal profile of the Il'd River and areas of bordering systems. All types of OM are closely related to the specifics of sedimentation and hydrodynamics of the waters of a given water area. The contributions of different groups of aquatic and near-aquatic photoautotrophs to the formation of the autochthonous component of OM in bottom sediments are discussed. The geochemical indices (Pr/Ph, OEP17–19, CPI) reflect the influence of oxidative conditions on the formation of OM and the active microbiological transformation of its autochthonous part. [ABSTRACT FROM AUTHOR]

Long-chain n-alkanes are one of the most common organic compounds in terrestrial plants and they are well-preserved in various geological archives. nalkanes are relatively resistant to degradation and thus they can provide high-fidelity records of past vegetation and climate changes. Nevertheless, previous studies have shown that the interpretation of n-alkane proxies, such as the average chain length (ACL), is often ambiguous since this proxy depends on more than one variable. Both vegetation and climate could exert controls on the n-alkane ACL, and hence its interpretation requires careful consideration, especially in regions like the Qinghai-Tibet Plateau (QTP) where topography, biome type and moisture source are highly variable. To further evaluate the influences of vegetation and climate on the ACL in highelevation lakes, we examined the n-alkane distributions of the surface sediments of 55 lakes across the QTP. Our results show that the ACL across a climatic gradient is significantly affected by precipitation, rather than by temperature. The positive correlation between ACL and precipitation may be because of the effect of microbial degradation during deposition. Finally, we suggest that more caution is needed in the interpretation of ACL data in different regions. [ABSTRACT FROM AUTHOR]

Stable carbon isotopes of long-chain n-alkanes in lake sediments have been used for reconstructing past environmental changes. Gas chromatography isotope ratio mass spectrometry coupled to a combustion unit is the commonly applied technique for compound-specific carbon isotope analysis. This paper shows that sulfur in the lacustrine sediment can cause severe interference during the mass spectrometric measurement, leading to significant biases in δ13C of n-alkane. The δ13C deviation could be resulted from additional 12C33S+, 13C32S+ at mass-to-charge ratio (m/z) 45, and 12C34S+, H2C32S+at m/z 46, respectively. Such elemental sulphur interference can be eliminated by the activated copper in the pretreatment procedure. [ABSTRACT FROM AUTHOR]

The indigenous populations of La Palma (Canary Islands), who arrived on the island from Northwest Africa ca. 2000 years B.P., were predominantly pastoralists. Yet, many aspects of their subsistence economy such as the procurement, management, and use of wild plant resources remain largely unknown. To explore this, we studied the 600–1100‐year‐old archaeological site of Belmaco Cave, which comprises a stratified sedimentary deposit representative of a fumier. Here, we present a high‐resolution, multiproxy geoarchaeological study combining soil micromorphology, lipid biomarker analysis, X‐ray diffraction, μ‐X‐ray diffraction, μ‐X‐ray fluorescence, Fourier transform infrared spectroscopy, and μ‐Fourier transform infrared spectroscopy, to characterize formation processes and explore plant sources. Recurrent goat/sheep habitation and maintenance activities are represented by interstratified layers of unburned dung, charcoal‐rich sediment, and dung ash. Lipid biomarker data show a herd diet mainly composed of herbaceous plants, which is key to understanding the mobility of indigenous shepherds. Our results also revealed an unusual suite of authigenic minerals including hazenite, aragonite, and sylvite, possibly formed through diagenetic processes involving interaction between ash, dung, urine, volcanogenic components, and bacterial activity, coupled with arid and alkaline conditions. Our study shows the potential of a multiproxy approach to a fumier deposit in a volcanogenic sedimentary context. [ABSTRACT FROM AUTHOR]

Recent experiments show that the diffusivities of C8 and C10 n‐alkanes in ZIF‐8 are higher than those of C7 and C9, respectively. We investigated this unusual 'odd‐even' effect by simulating the adsorption of C7‐C14 n‐alkanes in ZIF‐8 using hybrid Monte Carlo molecular simulations. The resultant adsorption isotherms, guest‐host energies, isosteric heats, and chain length distributions are analyzed for trends among the n‐alkanes. ZIF‐8 cages filled with n‐alkanes are characterized using a combination of image processing and data science to quantify the differences in packing that occur with chain length. Results indicate that packing changes drastically from C7 to C8 and from C9 to C10, which is consistent with the diffusion trends previously reported in experiments. [ABSTRACT FROM AUTHOR]

This study analyzed total organic carbon (TOC), petroleum products (PP), suspended materials (SM), volatile aromatic hydrocarbons (toluene, o-xylene, etc.) and n-alkanes in the snow cover of Bol'shekhekhtsirsky, Zeysky state natural reserves and Khabarovsk, on 4, 5 and 9 stations in the south of the Russian Far East in March 2020. In Bol'shekhekhtsirsky reserve, the concentrations of TOC, PP, and SM in snow samples were in the range of 1.5–2.4, 0.06–0.11, and 11.4–1.9 mg/L, 1.4–1.9, 0.02–0.05, and 11–23 mg/L in Zeysky reserve, while in Khabarovsk were 1.7–23.7, 0.12–1.26, and 25–294 mg/L, respectively. In addition, the benzene, toluene, and o-xylene concentrations of snow samples ranges from not detected (ND) to 2.4, ND–3.1, and 1.1–2.7 µg/L in Khabarovsk, ND–1.3, ND–2.1, and ND–2.7 µg/L, respectively in Bol'shekhekhtsirsky reserve. Carbon preference index values of n-alkanes were consistent with anthropogenic sources for stations 7, 8 and 2 in Khabarovsk (Heat Power Plants 1, 2 and city roads). The snow of the Zeysky Reserve is not contaminated with organic pollutants, and can be used as a conditional background for the south of the Russian Far East. [ABSTRACT FROM AUTHOR]

Purpose. The purpose of the study is to identify the features of spatial and vertical distribution of hydrocarbons in the bottom sediments and to assess the likely sources of their ingoing to the port coastal water area (at the example of the Streletskaya Bay). Methods and Results. The samples of the bottom sediments surface layer (5 sampling stations) and the columns of marine sediments (2 columns) were taken during the joint expedition of the Department of Marine Sanitary Hydrobiology (FRC IBSS) and the Department of Marine Biogeochemistry (FRC MHI) in July 2021 as a part of a long-term monitoring of the Sevastopol bays. The features of spatial distribution in the sediment surface layer (0–5 cm), the profiles of vertical distribution of the geochemical characteristics of bottom sediments, hydrocarbons and n-alkanes, and the individual diagnostic indices (markers) were analyzed. The history of hydrocarbon accumulation resulted from the 50-year long human activity was considered, and the anthropogenic load on the bay water area was assessed. Conclusions. The bottom sediments composition of the Streletskaya Bay promotes the accumulation of hydrocarbons: the aleurite-pelitic silts of high natural humidity are ubiquitous, and the organic carbon average contents in the surface layer (5.1%) and in the bottom sediments thickness (5.3%) significantly exceed the values typical of the other water areas in the Sevastopol region (1.2–3.7%). The hydrocarbon concentrations in bottom sediments ranged from 328 to 2175 mg/kg (the average value is 1160 mg/kg), that exceeds the pollution levels in many port areas of the Black Sea. The concentrations of the studied substances increase from the top of the bay to its apex. The composition of n-alkanes and the nature of chromatograms indicate a mixed origin of hydrocarbons at the dominating allochthonous (incoming from land) compounds, and also the presence of n-alkanes of the autochthonous and petroleum origin. Based on the data resulted from the chronology of hydrocarbon accumulation, the maximum anthropogenic loads on the bay fell on the periods 1967–1973 and 1985–1991. These were the years of intensive economic development of the city and the population growth in the sub-district adjacent to the studied water area in the Streletskaya Bay. In recent years, the intensity of hydrocarbon accumulation has been decreasing, but the signs of oil pollution are still present.

In Southern Brazil, exotic species as Acacia (A) and Eucalyptus (E) are often planted over native pasturelands and may change bulk soil organic matter (SOM) composition as verified in our previous study with Cambisols (0–5 cm). Here we aimed to follow the impact of seven-year A and E plantation on the composition of the free light- (FLF), occluded light- (OLF) and heavy fraction (HF) of SOM along the soil profile. We hypothesized that A and E may have shifted the molecular composition and carbon (C) stocks (Cs) of SOM fractions, at least at 0–5 cm; with stronger shifts caused by A due to greater E litter recalcitrance. Litter and soil samples (0–20 cm) were collected at A and E and neighboring native pasturelands without A (WA) and without E (WE). Litter, FLF, OLF and HF samples were subjected to C, nitrogen (N), pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) and lipid biomarkers analysis. In E soil, the Cs of FLF at 0–5 cm (0.5 Mg ha−1) and OLF at 5–10 cm (1.7 Mg ha−1) were 194 and 70 % greater than in WE, whereas in A soil the Cs of OLF at 0–5 cm (0.2 Mg ha−1) was 44 % lower than in WA. Nevertheless, A changed more remarkably the composition of SOM fractions, confirming our hypothesis partially, likely due to greater A litter biodegradability (polysaccharides abundance) compared to E. The contribution of A litter to FLF (0–10 cm) was evidenced by abundance of long chain and the predominance of odd-over-even n-alkanes (particularly >C29), and to OLF (0–20 cm) by the greatest abundance of n-alkanes at C31, resembling A litter. Loss of C and N of OLF in A compared to WA (0–5 cm) was compensated by fresh A litter additions to FLF and OLF and microbial-derived compounds association to soil minerals, equaling soil Cs in A and WA. The lower soil N stock in A compared to WA likely resulted from depletion of occluded microbial-derived N-compounds, supposedly reflecting the breakdown of soil aggregates at forest plantation. The increase of Cs in FLF and OLF of E compared to WE soil was associated with increased abundance of aromatics and n-alkane/alkenes and decrease of fatty acids. Similar patterns of n-alkanes observed for OLF of E and WE soil confirmed the incipient contribution of E litter to OLF. Conversion of these pastures to A and E modifies SOM composition and protection, requiring policies in view of the highly invasive potential and possible negative implications of A and E to native pasture regeneration.

Afforestation has been the dominant land-use change in the Swiss Alps during the last decades which has not only the potential to increase soil organic carbon sequestration, but it has also the potential to alter soil organic matter (SOM) dynamics through the vegetation shift and change in organic matter (OM) input into soils. The effects of afforestation on SOM dynamics, however, are still not fully understood as specific sources of OM and modifications of soil processes influencing decomposition and preservation remain largely unknown on alpine to subalpine slopes. Within this study we aimed to identify the potential sources and the decomposition of OM in a subalpine afforestation chrono-sequence (0–130 years) with Norway spruce (Picea abies L.) on a former pasture by using a multi-proxy molecular marker approach. We observed that leaf-derived OM plays an essential role in the pasture areas, while root-derived OM only plays a minor role in pasture and forest areas. Needle-derived OM represents the dominant source of SOM with increasing forest age, while understory shrubs and moss also contribute to the OM input in younger forest stand ages. However, needle litter and buildup of organic layers and subsequently less input of fresh OM from organic horizons to mineral soil can result in increased OM decomposition in mineral soils rather than contributing to additional SOM stabilization in mineral soils. This was most pronounced in the oldest forest stand (130-year-old) in the investigated afforestation sequence, particularly in deeper soil horizons (10–45 cm). Thereby, our study provides new insights into SOM dynamics following afforestation, especially with respect to the long-term SOM sequestration potential of afforestation of subalpine pasture soils.

The abundance and composition of aliphatic hydrocarbon biomarkers were determined in dated sediment cores from Lakes Qijiapao (QJP) and Huoshaoheipao (HSH) in the Songnen Plain, Northeast China, to investigate historical environmental changes in these lakes and identify likely controlling factors. Based on these results, the recent environmental history of the two lakes can be divided into three periods. Before 1950, low Paq values (avg. 0.23 and 0.27, respectively) and middle-chain n-alkane abundances (normalized to total organic carbon, avg. 14.82 and 16.01 µg g−1 TOC, respectively) in both lakes suggested low aquatic productivity and the limited input of submerged macrophyte organic matter (OM). However, the significant increase in the abundance of short-chain n-alkanes in Lake HSH (from 8.34 to 16.68 µg g−1 TOC) indicated the emergence of early nutrient enrichment in the lake. From 1950 to 2000, marked increase in the abundance of middle-chain n-alkanes (avg. 21.72 and 22.62 µg g−1 TOC in Lakes QJP and HSH, respectively) and Paq values indicated that both lakes had undergone eutrophication because of the population explosion and agricultural intensification. From 2000 to 2013, the abundance of short- and middle-chain n-alkanes in Lake QJP markedly exceeded those in Lake HSH and indicated a larger eutrophication in Lake QJP, which could be caused by the development of ecotourism in Lake HSH and the concomitant increase in aquaculture in Lake QJP in recent years. The highest abundance of C30 αβ-hopane (~ 10.24 µg g−1 TOC) and the lowest CPIH values in Lake QJP revealed a possible petroleum pollution since 2008. Taken together, lake eutrophication in the Songnen Plain accelerated after 1950 and was influenced primarily by agriculture and aquaculture. This is in contrast to lakes in other regions of China (such as the Yangtze River Basin and Yunnan Province), where urbanization and industrialization have exerted a dominant influence on the lake environment. [ABSTRACT FROM AUTHOR]

The removal of n-alkanes, polycyclic aromatic hydrocarbons, and heavy metals from wastewater using three dried seaweeds Ulva intestinalis Linnaeus (green alga), Sargassum latifolium (Turner) C.Agardh (brown alga), and Corallina officinalis Kützing (red alga) has been shown to evaluate their potential usage as inexpensive adsorbents. Under natural environmental conditions, numerous analytical methods, including zeta potential, energy dispersive X-ray spectroscopy (EDX), SEM, and FT-IR, are used in this study. The results showed that n-alkanes and polycyclic aromatic hydrocarbons adsorption increased with increasing contact time for all three selected algae, with a large removal observed after 15 days, while the optimal contact time for heavy metal removal was 3 h. S. latifolium dry biomass had more potential as bioadsorbent, followed by C. officinalis and then U. intestinalis. S. latifolium attained removal percentages of 65.14%, 72.50%, and 78.92% for light n-alkanes, heavy n-alkanes, and polycyclic aromatic hydrocarbons (PAHs), respectively, after 15 days. Furthermore, it achieved removal percentages of 94.14, 92.62, 89.54, 87.54, 82.76, 80.95, 77.78, 73.02, and 71.62% for Mg, Zn, Cu, Fe, Cr, Pb, Cd, Mn, and Ni, respectively, after 3 h. Carboxyl and hydroxyl from FTIR analysis took part in wastewater treatment. The zeta potentials revealed that algal cells have a negatively charged surface, and the cell surface of S. latifolium has a more negative surface charge than U. intestinalis and C. officinalis. Our study suggests that seaweeds could play an important role in wastewater treatment and thus help as an economical, effective, and ecofriendly bioremediation system for ecological health and life protection. [ABSTRACT FROM AUTHOR]

The climatic and environmental characteristics of the Holocene are much debated, especially the occurrence of a climatic optimum in the mid-Holocene and the interactions between human civilization and the environment. Knowledge of the Holocene climatic evolution of the Mu Us Sandy Land in North China is important for understanding the cultural development of northern Shaanxi. However, few continuous and high-resolution lake sedimentary records are available from the region. We selected Lake Gouchi, a climatically sensitive site in the Mu Us Sandy Land, for a study of sedimentary organic indicators such as n -alkanes, with the objective of reconstructing the regional climatic history since the mid-Holocene. Our results indicate that during 8130–4500 BP, the regional climate was relatively warm and humid, the terrestrial vegetation was dominated by woody plants, and the nutrient level of the lake was relatively stable. Then the climate gradually became arid. However, at the beginning of 2500 BP, there was an 800-year period of warm and humid conditions. Entering the historical period there was an increase in the environmental impacts of human activities. Overall, the climate of the Gouchi area was influenced by the response of the East Asian summer monsoon to changes in Northern Hemisphere summer insolation, which were responsible for the mid-Holocene Maximum. Comparison of the climatic record of Lake Gouchi with the sequence of cultural evolution in northern Shaanxi reveals a distinct relationship. Favorable climatic conditions were associated with technological development, an increasing population, and a flourishing civilization; whereas less favorable climatic conditions were associated with cultural stagnation or decline. [ABSTRACT FROM AUTHOR]

We study the global phase behaviour of n-alkanes applying Wertheim's first order thermodynamic perturbation theory (TPT1). The molecules are modelled as homonuclear chains comprised of m freely jointed spherical segments interacting via the Lennard-Jones potential. Vega et al. [J. Chem. Phys. 116, 17 (2002)] have shown that the TPT1 is suitable to treat solid phases as well as fluid phases when model chains are considered, but that the adoption of a fully flexible chain model leads to the under-prediction of triple point temperatures and overestimation of the fluid ranges in comparison to experiment. Here, we propose a model in which a different number of segments are used to treat the fluid and the solid phase. The number of segments used to model the molecules in the fluid phase m f , and the LJ monomer potential parameters σ and ε are taken from published soft-SAFT values, whereas in the case of the solid phase a reduced temperature-dependent effective chain length m s (T ∗) is determined through a minimisation between theoretical and experimental liquid-solid phase equilibrium data. We refer to this model as effective-solid TPT1 (es-TPT1). We use the model proposed to calculate the solid–liquid–vapour phase diagrams of several n-alkanes and compare with experimental data. In the approach proposed, the conformation of chains in the solid phase is decoupled from the fluid phase, and an excellent description of the melting properties, as well as accurate predictions of the triple point temperatures for the n-alkanes examined is obtained. This simple solution provides an avenue to model the solid–liquid–vapour phase behaviour of other real substances in a TPT1 framework, and hence within the SAFT family of equations. [ABSTRACT FROM AUTHOR]

The article deals with the integrated and comprehensive study of the coal-bearing horizons from the South Karanpura Basin to delineate the biostratigraphy, palaeovegetation, palaeodepositional settings, and palaeoclimate in and around the investigated area during the deposition of Permian sediments. Highly diversified megafloral assemblages consist 13 genera and 72 species of order Glossopteridales, Cordaitales and Equisetales are documented among which 37 taxa are newly reported from Barakar and Raniganj formations of the area. Palynoassemblages-I and -II are recovered, which demonstrate the biostratigraphic age as Kungurian and Wordian–Capitanian, respectively. Overall the vegetation represents a luxuriant forest subjugated by arborescent deciduous trees bearing Glossopteris foliage with some conifers, cordaites, filicales, and peltaspermales. The biomarker study of the basin illustrates the unimodal distribution of n-alkanes in the sample set ranges from C14 to C29 which suggests major input from a single source of organic matter. The involvement of microbial activity and algal input is suggested for the basin. A relatively moderate-to-high water level condition can be inferred from elevated n-C25. The high CIA, PIA values and A–CN–K plot suggest intense weathering conditions in the source area. The source rocks are characterized by mature clayey type with abundant clay mineral, i.e., kaolinite. The current study portrays that the Permian climate was cooler in initial phase, which later on became warm temperate with high humidity. The palaeofloral entities and geochemical parameters suggest absolute diversification of Permian flora, the existence of continental freshwater setting in the vicinity and oxic to anoxic environment with fluctuating ground water conditions during the deposition of sediments. [ABSTRACT FROM AUTHOR]

Identification and quantification of allochthonous and autochthonous organic carbon (OC) are crucial for the interpretation of burial behaviors of sedimentary OC of shallow lakes under anthropogenic interferences. In this study, we analyzed distribution patterns and δ13C signatures of mid-and long-chain n-alkanes on various types of surface samples from a typically large and shallow Lake Wuliangsu in the Hetao Irrigation District. The results indicate that n-alkanes among submerged macrophytes, emergent plants, and riverine soil show unique distribution patterns and δ13C signatures, supporting the practicability of quantification on OC of these sources by end-member mixing models. Introducing the δ13C values of n-alkanes into the endmember mixing models could effectively reduce the potential error derived from end-member determination on n-alkane distribution patterns and OC degradation. The model results suggest that the riverine sourced OC from the main channel to Lake Wuliangsu has settled down during the southward migration process. Therefore, Lake Wuliangsu serves as an important trap and sink for the allochthonous OC from the Upper Yellow River Reaches. The model results also show a predominate contribution from the autochthonous OC to Lake Wuliangsu (mostly >85%), with open-water areas dominated by submerged macrophytes and the rest of areas by emergent plants, largely modulated by water transparency, water depth, and nutrient concentrations. Together with previously published tetraether results, we further proposed that areas dominated by submerged macrophytes might be more favorable for heterotrophic anaerobic bacteria and methanogenic archaea, largely due to active recycling processes for the labile OC derived from submerged macrophytes. [ABSTRACT FROM AUTHOR]

The importance of plant cuticular waxes in plant–herbivore interactions has become an area of increasing interest, but it has been poorly explored in chrysomelid beetles, one of the most important groups of insect pests. In this study, we investigated the effects of cuticular wax on feeding behaviors of Aulacophora femoralis (Chyrosomelidae), a pest of Cucurbitaceae crops. We analyzed chemical compositions of leaf cuticular waxes using gas chromatography–mass spectrometry. The compositions were significantly different among plant species; in particular, host (Cucumis maxima, C. pepo, C. sativus, Cucurbitaceae) and non-host (Pueraria lobata, Fabaceae) leaves had distinctive compositions of cuticular waxes. We examined if the cuticular wax induces feeding behaviors based on a bioassay using filter papers treated with cuticular wax extract from host or non-host leaves, or a synthetic mixture of straight-chain alkanes (n-alkanes), major components of the host cuticular waxes shared among different host species. We found that the beetles frequently left bite marks on the filter papers treated with n-alkanes but less frequently on those treated with cuticular wax extracts of host leaves. These results indicate that leaf cuticular wax n-alkanes stimulate feeding behavior, but are not cues for host selection. [ABSTRACT FROM AUTHOR]

The “river-sea” geochemical barrier is studied slightly in terms of the variety of pollutants, sedimentation, and degradation. At the same time, problems related to oil pollution, in particular the genesis of hydrocarbons, are almost never covered. This study was dedicated to the origin, concentration, and composition of hydrocarbons in the bottom sediments of the Chernaya River (Black Sea, Crimea) estuarine zone. The features of the marginal filter zone of the river were considered. N-alkanes in the range of C11-C36 were identified in the bottom sediments of the studied water area. It was noted that there was persistent oil pollution (degraded hydrocarbons) in the water area of Sevastopol Bay, adjacent to the confluence of the river. The accumulation of terrestrial material increased as it moved from the river to the sea. The application of various molecular markers displayed the predominately allochthonous origin of the hydrocarbons in the bottom sediments. As a result of the study of molecular markers by using principal component analysis (PCA) and analysis of variance (ANOVA) analysis, three leading factors responsible for hydrocarbon input to the bottom sediments water area were identified. The first one (36.53 % of the total variation) was associated with n-alkanes of natural and anthropogenic input. The second factor (19.52 % variation) was associated with allochthonous organic matter, including petroleum and bacterial destruction. The third factor (10.74 %) was associated with mainly allochthonous routes of organic substances entering the bottom sediments of the water area.

N-alkanes offer a promising approach for assessing the nutritional contribution of external sources to the diets of laying hens in free-range production systems. However, traditional laboratory methods, involving extraction, purification and gas chromatographic analysis, are both economically burdensome and time-consuming. Near-infrared spectroscopy (NIRS) is emerging as a viable alternative, with varying degrees of accuracy depending on the chemical nature and concentration of the component of interest. In our research, we focus on the accuracy of NIRS in predicting the concentrations of n-alkanes (C25–C33) in excreta under simulated free-range conditions with two different diets: one containing a commercial feed with minimal n-alkane content and another containing 1% alfalfa on top of the commercial feed. Spectra processing and calibration were tailored for each n-alkane, with NIRS performance influenced by diet type. Notably, plant predictions using NIR-generated data were consistent with laboratory results, despite a slight tendency toward overestimation (3.40% using the NIRS-generated C25-C29-C33 combination versus 2.80% using laboratory analysis). This indicates the potential of NIRS as an efficient tool to assess n-alkanes in excreta of laying hens and, consequently, the nutritional contribution of the free-range environment, providing rapid and cost-effective results.

The Neogene fluvial–lacustrine sediments of the Tianshui Basin provide records of the interactions among tectonic activity, and climatic and ecological changes on the northeastern Tibetan Plateau (NE TP), from ∼12.4 to 2.6 Ma. We investigated the n-alkane record of a sedimentary sequence from the Tianshui Basin, which reveals shifts in the productivity and sources of n-alkanes. The productivity of n-alkanes doubled many times during ∼4.2–3.2 Ma, accompanied by the increased contribution from aquatic plants; in addition, non-emergent macrophytes occurred sporadically after ∼4.2 Ma but became a significant n-alkane source after ∼3.2 Ma. Changes in the inferred Late Miocene ecology of the region are consistent with the major climate transition in response to global cooling. The oscillations of the types and concentrations of n-alkanes during 4.2–3.2 Ma were likely related to the evolution of the East Asian monsoon (EAM), driven by the tectonic uplift of NE TP and global cooling. The major increase in aquatic plants and biological productivity of this region at ∼3.2 Ma may have been caused by the strengthening of the East Asian summer monsoon (EASM) and the regional tectonic uplift.

• Historical occurrence of PAHs in lake Taihu were reconstructed from a sediment core. • High-ring PAHs posed relatively higher fractions and concentrations in recent decades. • Different components of SOM were identified by n -alkane markers. • Sedimentary PAHs were associated with both anthropogenic and biogenic SOM. • The toxicity of PAHs rapidly increased in recent sediments. Sediment core is the recorder of polycyclic aromatic hydrocarbon (PAH) pollutions and the associated sedimentary organic matter (SOM), acting as crucial supports for pollution control and environmental management. Here, the sedimentary records of PAHs and SOM in the past century in Lake Taihu, China, were reconstructed from a 50-cm sediment core. On the one hand, the presence of PAHs ranged from 8.99 to 199.2 ng/g. Vertically, PAHs declined with the depth increased, and the sedimentation history of PAHs was divided into two stages with a discontinuity at 20 cm depth. In composition, PAHs in the sediment core were dominated by three-ring PAHs (44.6% ± 9.1%, mean ± standard deviation), and were followed by four-ring (27.0% ± 3.3%), and five-ring (12.1% ± 4.0%) PAHs. In toxicity assessment, the sedimentary records of benzo[ a ]pyrene-based toxic equivalency were well described by an exponential model with R -square of 0.95, and the environmental background toxic value was identified as 1.62 ng/g. On the other hand, different components of SOM were successfully identified by n -alkane markers (p < 0.01) and the variations of SOM were well explained (84.6%). A discontinuity of SOM was recognized at 22 cm depth. Association study showed that the sedimentary PAHs were associated with both anthropogenic and biogenic SOM (p < 0.05) with explained variances for most individual PAHs of 60%. It indicated the vertical distributions of PAHs were driven by sedimentary SOM. Therefore, environmental processes such as biogenic factors should attract more attentions as well as PAH emissions to reduce the impacts of PAHs. [Display omitted] [ABSTRACT FROM AUTHOR]

Strong variation in plant organic compound δ2H and δ18O values such as leaf waxes or cellulose among species is commonly observed; however, the extent to which this isotopic variation is driven by leaf water or biochemical isotope effects is relatively unknown. Therefore, we compared variation in leaf water and organic compound δ2H and δ18O values (cellulose - δ2H and δ18O, and n -alkanes – δ2H) across 192 species grown in a botanical garden to assess covariation of isotope values (1) between elements in a given compound, (2) between different (organic) compounds of a given element, and (3) across different growing seasons. Our results suggest that variation in leaf water δ2H values are likely not a strong driver for the observed variation in organic compound δ2H values across species, and that this may also be true for δ18O values. Furthermore, even though correlation between leaf water δ2H and δ18O values appears to be transferred to organic compounds, the explanatory power of this correlation is strongly diminished (R2 < 0.04). This indicates that additional biochemical isotope fractionation leads to substantial variation in organic compound δ2H and possibly also δ18O values across species. Moreover, the low explanatory power of the correlation between cellulose and n -alkane δ2H values (R2 = 0.06) suggests that the biochemical pathways associated with the different compounds are accompanied by different isotope effects. Lastly, cellulose δ2H and δ18O values appeared sensitive to environmental differences between growing seasons, while differences in model-predicted source water δ18O and δ2H values and also climate were negligible between years. By contrast, the species pattern in n -alkane δ2H values was highly conserved between the two years. This indicates that the environmental forcing effects on isotope values were not equal between compounds. Therefore, we conclude that variation in organic compound δ2H (and possibly also δ18O) values among species and growing seasons was more strongly driven by biochemical isotope fractionation rather than by isotope values of plant water. This should be considered in the application of organic compound δ2H and δ18O values to reconstruct past climate, where invariable biochemical isotope fractionation is often assumed. Alternatively, organic compound δ2H and δ18O values could be further developed into a tool to extract plant metabolic information. [ABSTRACT FROM AUTHOR]

As small-bodied terrestrial organisms, insects face severe desiccation risks in arid environments, and these risks are increasing under climate change. Here, we investigate the physiological, chemical, and behavioral mechanisms by which harvester ants, one of the most abundant arid-adapted insect groups, cope with desiccating environmental conditions. We aimed to understand how body size, cuticular hydrocarbon profiles, and queen number impact worker desiccation resistance in the facultatively polygynous harvester ant, Pogonomyrmex californicus. We measured survival at 0% humidity of field-collected worker ants sourced from three closely situated populations within a semi-arid region of southern California. These populations vary in queen number, with one population dominated by multi-queen colonies (primary polygyny), one population dominated by single-queen colonies, and one containing an even mix of single- and multi-queen colonies. We found no effect of population on worker survival in desiccation assays, suggesting that queen number does not influence colony desiccation resistance. Across populations, however, body mass and cuticular hydrocarbon profiles significantly predicted desiccation resistance. Larger-bodied workers survived longer in desiccation assays, emphasizing the importance of reduced surface area-to-volume ratios in maintaining water balance. Additionally, we observed a positive relationship between desiccation resistance and the abundance of n-alkanes, supporting previous work that has linked these high-melting point compounds to improved body water conservation. Together, these results contribute to an emerging model explaining the physiological mechanisms of desiccation resistance in insects. [ABSTRACT FROM AUTHOR]

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The environmental and health risks of n-alkanes and benzene, toluene, ethylbenzene, and xylene (BTEX) in Eze-Iyi River at Isuikwuato oil spill site were evaluated. The water samples (60) were collected from upstream and downstream during the dry and rainy seasons. Concentrations of n-alkanes and BTEX were determined using a gas chromatograph coupled with a flame ionization detector. The percentage recovery of 87.3% and 92.0% was obtained for n-alkanes and BTEX in the water sample. The environmental risk analysis for n-alkanes and BTEX showed 80% of the water samples had a ratio greater than 1 indicating environmental risk in the area. Hydrocarbon source identification using biomarkers indicates that the n-alkane (nC16) dominant during the dry and rainy seasons was from anthropogenic/biogenic source, while nC14 and nC17 were from microbial and marine algae biogenic sources, respectively. The benzene levels in 100% (downstream) and 80% (upstream) of samples in the dry season and 40% (upstream) and 100% (downstream) of samples in the rainy season were above the WHO permissible limit of 0.01 mg/L for drinking water. The health risk index of n-alkanes during the dry season for children (upstream) was greater than 1 signifying adverse health risk. Therefore, consumption of water from the river should be discouraged and routine monitoring by regulatory authorities maintained to checkmate the build-up of BTEX and n-alkanes. [ABSTRACT FROM AUTHOR]

Earlier studies on the Mahadeo-Cherrapunji road (MCR) section have documented the Cretaceous-Palaeogene Boundary (KPB ca. ~ 66 Ma), but rare data exist on the Deccan volcanism induced KPB transition and related faunal crises. The environmental stress on biota has been postulated as the main cause of mass extinction. Thus, the study of organic matter (OM) entrapped in the Maastrichtian-Danian shelf sediments has attained importance, although the existing data is inadequate. In this situation, layer-wise n-alkanes and n -fatty acids analyses were carried out using GC-MS. Obtained data show sudden increase in the short chain n -alkane (SCA ~ 6-fold), n-fatty acid (FA) and hopane (> sterane) concentrations. This suggests enhanced continental runoff and soil bacteria biomass passage into the marine realm. Comparing the MCR to the published KPB bearing shallow-marine facies of the Um-Sohryngkew River (USR) section data, we document high SCA and FA contents together with the abundance of the even carbon numbered SCA (n-C16 and n-C18). This suggests thermal degradation and partial combustion of non-woody biomass. The presence of C17n-alkane and hopane is indicative of their derivation from the algae, fungi and bacteria. A sudden SCA concentration increase coincides with the reported major foraminifers' extinction between the CF1 and P0 biozones of the MCR section. Further, a similar anomaly exists in the lower part of the CF3 biozone of the USR section and precedes extinction of the main foraminifers' assemblages. The excursions in SCA content along with hopane and FA are matching well with the major incidences of the Deccan volcanic episodes and convergence of the Indian-plate with the Eurasian plate occurred at 66 Ma (Beck et al. 1995) and with the Burmese-plate during Maastrichtian (Wakita and Metcalfe 2005). These events were responsible for the sea-water disturbances, eustatic and depositional changes, including the retreat of the Tethys. Thus, a combination of extra-basinal and tectono-thermal events together with the greenhouse effects led to unexpected temperature rise and recurrent local sea-level changes that may have resulted in stress and faunal crisis. [ABSTRACT FROM AUTHOR]

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Adsorption of methane, ethane, and butane on two microporous carbon adsorbents was studied at T = 303, 313, 323, and 333 K. Measurements were carried out on a gravimetric-volumetric setup in a pressure range of 0.001–40 MPa. The adsorption volumes were determined using the theory of volume filling of micropores. The excess adsorption isotherms and the total content adsorption isotherms were calculated using the experimental data. The total content adsorption isotherms were used to plot the adsorption isosteres and to evaluate the initial and isosteric heats of adsorption. It was found that the heats of adsorption of ethane and butane on both adsorbents are higher than those of methane. It follows that the adsorbents under study can be used in adsorption-based systems for ethane and butane extraction from the natural gas streams. It was established that the ratios of the initial heat of adsorption of both ethane and butane to that of methane are in good agreement with the corresponding molecular polarizability ratios, which can be used to calculate the heats of adsorption. Namely, the initial heat of adsorption of a hydrocarbon can be evaluated using the experimentally determined initial heat of adsorption of the other hydrocarbon and the known molecular polarizabilities of both hydrocarbons without performing additional adsorption measurements. [ABSTRACT FROM AUTHOR]

Abstract In this study, major chemical components of PM2.5 including nitrate, sulfate, organic carbon (OC), and elemental carbon (EC) were measured in Chuncheon, South Korea in May–June, 2021. Average PM2.5 concentration was 16.4±9.7 µg m−3, and OC was the largest contributor of PM2.5 mass concentration. High concentration episodes (HCEs), defined when PM2.5 concentration exceeded 30 µg m−3, were caused by Asian dust, secondary inorganic aerosol (SIA) formation, and primary OC emission. NH4+ was determined to be a limiting factor for SIA formation based on neutralization ratio. There was statistically significant correlation between n-alkanes and PM2.5, and odd alkanes including C27, C29, and C31, which are generally emitted from biogenic sources, were abundant species, suggesting the importance of natural sources over fossil fuel combustion. Polycyclic aromatic hydrocarbons (PAHs) concentrations were significantly lower than those measured at the same sampling site in 2014–2015. Based on the diagnostic ratios of PAHs, vehicular emission, rather than solid fuel emission, were significant for PAHs. Detailed characterization of chemical composition of PM2.5 reported in this study can be of great help in establishing an appropriate abatement policy to reduce PM2.5 concentrations.