History of organic pollution in montane lake Issyk-Kul, Kyrgyzstan, Central Asia, inferred from a sediment core

In arid regions, montane lakes are valuable water sources and play important ecological roles. However, recent human-induced inputs of organic pollutants are threatening lake ecology in such regions and becoming a matter of great concern. To investigate pollutant histories and sources, we measured polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in a dated sediment core that spans the last ∼350 years, from montane Lake Issyk-Kul (Kyrgyzstan, Central Asia). Results showed that organic pollutants were delivered to Lake Issyk-Kul in four stages and that their concentrations increased from Stage I (∼1670-1800 CE) to Stage IV (∼2000-2010 CE). Furthermore, we tracked the sources of sedimented PAHs using their ratios combined with n-alkanes data. Ratios of PAHs Ant/(Ant + Phe), Flt/(Flt + Pyr) and Bap/BghiP indicated that inputs during Stage II (∼1800-1970 CE) and Stage III (∼1970-2000 CE) came mainly from high-temperature combustion of coal and vehicle emissions. PAHs in Stage I and Stage IV, however, were mainly derived from low-temperature combustion and petrogenic sources. Diagnostic PAH ratios, combined with the natural n-alkane ratio (NAR＜0) and unresolved complex mixtures (UCM), showed that the sources of PAHs in Stage I were mainly from erosion of bedrock and partly influenced by forest wildfires, different from the source during Stage IV, which was mainly from refined petroleum caused by accidental spills. Our assessment of the contamination history of the lake indicates that toxicity risk to the waterbody from sediment PAHs is low, but recent discharges arising from traffic deserve attention.

Migration and distribution characteristics of typical organic pollutants in condensable particulate matter of coal-fired flue gas and by-products of wet flue gas desulfurization system

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.

Sediment geochemical records of water quality deterioration in lake Jiren, a remote alpine lake on the southeastern margin of the Tibetan Plateau

Limited human activities in catchments make remote alpine lakes valuable sites for studying the evolution of lake environments in response to climate change and atmospheric deposition; however, this issue remains rarely studied owing to the scarcity of monitoring data. In this study, water quality evolution in Lake Jiren, a remote alpine lake on the southeastern margin of the Tibetan Plateau, over the past two centuries was reconstructed through geochemical analyses of aliphatic hydrocarbons, major and trace elements, and organic matter (OM) pyrolysis products in a dated sediment core, and the associated drivers were identified by temporally comparing the geochemical results with document records. All geochemical data demonstrated that the lake water remained relatively pure until 1947, after which the n-alkane and αβ-hopane proxies indicated eutrophication and petroleum contamination. The OM pyrolysis proxy hydrocarbon index indicated more eutrophic conditions after 1957. Concurrently, hypolimnetic deoxygenation increased, as indicated by redox-sensitive proxies, such as the enrichment factors (EFs) of molybdenum (Mo). These proxies recorded further intensification of deoxygenation after 1976. The EFs for other trace elements indicated cadmium contamination after 1967. The greater anthropogenic emissions of reactive nitrogen, petroleum products, and heavy metals in East and South Asia since approximately 1950 and the subsequent atmospheric transport of these materials to the lake might be the basic driver of water quality deterioration. Eutrophication induced by nitrogen deposition was responsible for increased hypolimnetic deoxygenation by enhancing phytoplankton productivity and OM input. The further intensification of deoxygenation was attributed to climate warming since the 1970s, as prolonged water column stratification under this condition decreased oxygen input from the epilimnion to the lake bottom. These findings may be beneficial for understanding the natural and anthropogenic effects on the water quality of alpine lakes and help in the environmental management of Lake Jiren and other alpine lakes.

Geochemical records of human-induced environmental changes in two small remote lakes of Songnen Plain, Northeast China

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.

Bioremediation of n-alkanes, polycyclic aromatic hydrocarbons, and heavy metals from wastewater using seaweeds

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.

Data for crystallisation of a homologous series of single and mixed n-alkanes (C16 - C23) from representative hydrocarbon fuel solvents

The data presented in this article relates to the crystallisation of 8 single n-alkanes, C₁₆H₃₄ - C₂₃H₄₈ in representative diesel solvents dodecane and toluene, as well as a mixture of these 8-alkanes with a composition representative of real diesel fuel in the same solvents. For the single alkane systems, the data was collected over a range of 5 concentrations ranging from 0.09 - 0.311x_i, depending upon the system, and 4 concentrations for the 8-alkane mixture, 0.1 - 0.5x_i. Raw average crystallisation and dissolution points as a function of cooling rate (q) from a polythermal methodology are presented. Along with the equilibrium crystallisation and dissolution temperatures, van't Hoff fitting parameters, relative critical undercooling (u_c) values as a function of q as well as the calculated values of K_G and α_det.

Environmental and health risks assessment of n-alkanes and BTEX in Eze Iyi River at oil spill site in Isuikwuato, Abia State, Nigeria

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.

Aliphatic and polycyclic aromatic hydrocarbons in surface sediments as a tool for the assessment of the contamination status of mangrove forests in Rio de Janeiro (Brazil)

The distribution of aliphatic and polycyclic aromatic hydrocarbons (PAHs) in surface sediments from mangrove forests of the Rio de Janeiro State was investigated. Ten sampling stations were selected in the mangroves of Sepetiba Bay and the Jacarepaguá Lagoon Complex (JLC), which are areas affected by multiple human activities. The total aliphatic hydrocarbons concentrations showed marked variation between samples (27-407 μg g^-1), mostly related to the total organic carbon contents. The total PAHs concentration ranged between 38 and 792 ng g^-1. Diagnostic indices and statistical analysis showed that the mangrove forests can be divided into three groups: the western portion of Sepetiba Bay with the lowest level of contamination; the inner portion of the bay with the most intense presence of local sources of contamination, especially of pyrolytic character; and the JLC with a greater accumulation of hydrocarbons, mainly derived from petroleum combustion, resultant from the intense urbanization.

Insights into seasonal-variability of SVOCs, morpho-elemental and spectral characteristics of PM2.5 collected at a dense industrial site: Faridabad, Haryana, India

The development-oriented anthropogenic activities have led to intensive increase in emission of various organic pollutants, which contribute considerably to human health risk. In the present study, chemical, physical and spectral characterisation of fine particulate matter (PM_2.5), collected at Faridabad city, in northern India, were examined. Seasonal variation of organic compounds [n-alkanes, polyaromatic hydrocarbons (PAHs) and phthalic acid esters (PAEs)], and potential health risk of Polyaromatic hydrocarbons (PAHs) exposure using toxic equivalency potential (TEQ) approach had been assessed. These showed seasonal average values ranging from 156.4 ± 57.0 ng/m³ to 217.6 ± 72.9 ng/m³, 98.0 ± 21.4 ng/m³ to 177.8 ± 72.8 ng/m³, and 30.9 ± 11.9 ng/m³ to 82.5 ± 29.2 ng/m³, respectively, with the highest value for winter. It is noteworthy that unlike, n-alkanes and PAEs, PAHs were least during spring. The high molecular weight PAHs (BaP, BkF, DahA and IcdP) were found to exhibit higher TEQ values (ranging from 0.7 to 9.7) despite of their lower concentrations. The PAH diagnostic ratio, carbon preference index and total index revealed the enhanced impact of biogenic sources of emissions in comparison to diesel emission sources during winter.

The metabolic sensitivity of hydrogen isotope fractionation differs between plant compounds

Hydrogen stable isotope analyses (δ²H) of plant derived organic compounds are a useful tool for ecological, environmental, and palaeoclimatological research. However, during organic compound synthesis, variable biosynthetic ²H-fractionation has been suggested to occur as a result of changes in plant carbon fluxes. So far, inference has been based on examining the δ²H patterns of plant compounds along environmental gradients, among plant species, and between plant organs. In an alternative approach, we used four plant species with four different types of mutations that cause impaired starch synthesis to assess whether variability in carbon metabolism affects the biosynthetic ²H-fractionation during cellulose, phytol, and acetogenic lipid synthesis. We found that mutants with impaired starch synthesis always had higher cellulose and phytol δ²H values compared to the wild type. By contrast, ²H-fractionation during acetogenic lipid biosynthesis generally did not show strong metabolic sensitivity. We rationalise these differences by considering the biosynthetic pathway of each compound and the likely source of the variable isotope fractionation. In different organic compounds, the sensitivity of variable biosynthetic ²H-fractionation to changes in C-metabolism depends on incorporation of specific H atoms from precursor molecules. As such, we determined that the similar increase in cellulose and phytol δ²H values as an effect of impaired starch synthesis most likely originates in triose-phosphates.

Source identification and ecological risks of parent and substituted polycyclic aromatic hydrocarbons in river surface sediment-pore water systems: Effects of multiple factors

Substituted polycyclic aromatic hydrocarbons (SPAHs) have shown higher health and ecological risks than the corresponding parent PAHs (PPAHs) from laboratory studies, their variations in freshwater system, especially in surface sediment and pore water, remain inadequate understanding. In this study, we revealed the coexistence, ecological risk, and multiple factors affecting variations and sources of PPAHs and SPAHs (nitrated PAHs (NPAHs), oxygenated PAHs (OPAHs)) in the surface sediment-pore water system from a typical urban river in Northern China. The concentration ranges of Σ₂₆PPAHs, Σ₁₀NPAHs, and Σ₄OPAHs in the surface sediments were 153.0-5367.4, not detected (N.D.)-105.4, and 42.2-1177.0 ng·g^-1 dry weight, and fell within 0.6-38.8, N.D.-297.9, and N.D.-212.6 ng·mL^-1 in the pore waters. The t-distributed stochastic neighbor embedding (SNE) coupled with the partitioning around medoids (PAM) elucidated spatiotemporal the variations in PAHs, emphasizing the impacts of industrial activities and sewage discharges. Besides the geochemical and hydrochemical conditions, SPAHs were affected by the potential secondary formation, especially during the wet season. The method comparisons indicated the advantages of principal component analysis-multivariate linear regression (PCA-MLR) and n-alkanes model on source identification. PAHs mainly originated from fossil fuel combustion and vehicular exhaust. The top risk quotient (RQ) values for PAHs occurred in the urban and industrial sections. A majority of the surface sediment samples emerged with low to moderate exposure risks, while all the pore water samples showed high exposure risks. The RQs of OPAHs were significantly higher (p < 0.01) than those of PPAHs. The results suggested the secondary formation of SPAHs as an important role in ecological risks of PAHs in the urban river system.

Occurrence, sources and spatial distribution of n-alkanes in surface soils from the Amu Darya Delta, Uzbekistan, arid Central Asia

Central Asia (CA) has attracted global attention because of either water scarcity or ecosystem degradation. The Amu Darya Delta (ADD), one of the most important oases in CA, is endowed with valuable wetlands and biological resources that provide good ecosystem services to inhabitants. However, the region has experienced climate warming and large-scale anthropogenic changes since the last century. To assess the influences of anthropogenic interventions on the soil environment in this area, surface soil samples collected from the ADD were analysed for aliphatic hydrocarbon fractions and five heavy metals (HMs; including Cd, Zn, Cu, Ni and V). The results indicated that the n-alkanes extracted from surface soils were composed of homologous series from C14 to C35. Relatively high abundances of short-chain n-alkanes (<n-C21) were observed in cluster 1 samples (mainly from the lakeshore of the Aral Sea), while significantly high abundances of mid-chain (n-C21 to n-C25) and long-chain (n-C26 to n-C32) n-alkanes were found in cluster 3 samples, which were distributed in urban and agricultural drainage areas. In addition, very-long-chain n-alkanes (>n-C33) occurred in most surface soils, which might be a sign of a hot and arid climatic environment. Notably, almost all samples presented a clear even carbon dominance of short-chain n-alkanes, especially for cluster 1, which possibly represented the influence of hydrocarbon contamination and highly saline carbonate environments in addition to bacterial degradation. The biomarker indices and HM enrichment index indicated greater effects of crude oil pollution on cluster 1 (specifically samples 2, 4, 5, 6, 13, 16 and 34) and anthropogenic activities such as traffic emissions and agricultural drainage on cluster 3 samples. The results of this study provide evidence that the n-alkane composition and abundance in surface soils respond sensitively to anthropogenic interventions, arid climate and petroleum hydrocarbon pollution.

Geochemical records of Lake Erhai (South-Western China) reveal the anthropogenically-induced intensification of hypolimnetic anoxia in monomictic lakes

In monomictic lakes, hypolimnetic anoxia is becoming severe in extent and duration over the past few decades. Understanding historical trends in hypolimnetic dissolved oxygen (DO) levels and the factors controlling them is crucial for effective protection and management of monomictic lakes everywhere, but the issue remains little studied in China. Here, our study elucidated the variation of hypolimnion DO and organic matter (OM) input in Lake Erhai (a typical monomictic lake in South-Western China) during the past 200 years, by using the geochemical profiles of elements (C, N, P, S, Mo, Ca, and Al) and aliphatic hydrocarbons in a dated sediment core. The values of element proxies (S concentrations, S/Al ratios, Mo enrichment factor, and total organic carbon/total P ratios) and pristane/phytane (Pr/Ph) ratios reflect relatively limited development of anoxia in the lake hypolimnion before 1990. Meanwhile, the n-alkane proxies (short-chain, middle-chain, and long-chain n-alkane abundances, n-C₁₇/n-C₁₆ alkane ratios, and Paq) indicate relatively scant inputs of OM from phytoplankton and relatively high inputs of OM from terrestrial plants or from submerged macrophytes. Taken together the results show that OM supplied in this period did not deteriorate hypolimnion DO in Lake Erhai. The element proxies and Pr/Ph ratios point to that the lake had experienced a pronounced intensification of hypolimnetic anoxia after 1990, and the n-alkane proxies indicate that the lake was susceptible to severe eutrophication and phytoplankton blooms in this period. The synchronous sharp variation implies the decay of massive phytoplankton OM had severely consumed oxygen in the lake hypolimnion. The large surface area/depth ratio in Lake Erhai is conducive for an overturn of the water column during wind disturbance, which allowed the water column stratification and relating effects (e.g., hypolimnetic anoxia) less vulnerable to some aspects of climate change.

Lipid biomarkers and metal pollution in the Holocene record of Cartagena Bay (SE Spain): Coupled natural and human induced environmental history in Punic and Roman times

We reconstructed the palaeoenvironmental conditions of Cartagena Bay during the Holocene after a multidisciplinary study to identify natural variations and the anthropic processes of this coastal area. A total of 119 samples were recovered for amino acid racemization dating, 3 for radiocarbon dating (¹⁴C), and four sets of 80 samples for sedimentological and palaeontological determination, mineralogical content, biomarker and trace elements quantification. Two natural scenarios were identified from the variations of n-alkane indices and palaeobiological content. The first period (6650-5750 yr cal BP) was marked by the development of euhaline marine conditions with strong inputs from aquatic macrophytes and high biodiversity. After a hiatus, the area underwent a profound change, becoming a paucispecific brackish marsh environment with increasing inputs from land plants, with possible episodes of emersion with a greater presence from terrestrial gastropods (3600-300 cal yr BP). By combining trace element abundance and stanol distributions, our study also provides a novel approach to identify the predominant influence of anthropogenic factors in the last three millennia in the coastal record of Cartagena Bay. Findings confirmed that Pb mining and metallurgy began during the Bronze Age, with considerable inputs of this heavy metal into the atmosphere during Phoenician, Punic and particularly Roman times compared to the Middle Ages. Pollution by Cu and Zn was also observed during Punic and Roman times, and was first documented in the Middle Ages. In addition, faecal stanols, such as coprostanol, derived mainly from humans, and 24-ethylcoprostanol from herbivores were present, thereby indicating for the first time a continuous presence of human populations and significant pollution input since 3600 yr cal BP, this being greater in the late Bronze Age and Phoenician, Punic and Roman times than during Late Antiquity and the Middle Ages, when the city was in decline.

Occurrence characteristics and source appointment of polycyclic aromatic hydrocarbons and n-alkanes over the past 100 years in southwest China

The extensive anthropogenic activities and their potential impacts during the Anthropocene have led to a research focus on the sedimentary record. In the present study, the occurrence and temporal variations in the fluxes and compositions of n-alkanes and polycyclic aromatic hydrocarbon (PAHs) were investigated in ²¹⁰Pb-dated sediment cores from a small catchment near the outflow Tanglangchuan in the western Dianchi Lake, China. The continuing organic contamination (i.e. PAHs and n-alkanes) from inputs to outputs has been of concern. To trace the sources and driving forces, multi indicators were applied. Results showed that the total organic carbon (TOC) contents and C/N ratios varied in the range of 4.20-12.30 mg g^-1 dw and 8.64-15.65, respectively, indicating algae- and terrestrial plant-derived organic matter (OM). The flux of Σn-alkanes ranged from 0.67 to 38.86 μg cm^-2 a^-1 with a peak in 2013. The long-chain n-alkanes (Σn-alk_26-35) and short-chain n-alkanes (Σn-alk_12-20) accounted for 44.02%-49.38% and 35.32%-41.49% of the Σn-alkanes, respectively. A bimodal distribution of n-alkanes was displayed in the sediments implying the sedimentary OM may be derived from a mixed source of endogenous and exogenous origin. The posterior peak (≥n-C₂₆) compounds in the highest abundance were n-C₃₁ or n-C₃₃ with a significant odd-numbered C predominance, representing terrestrial plant-derived OM. Whereas n-C₁₆ was rich in all sediment profiles reflecting crude oil or incompletely combusted fossil fuel-derived source. The indicators analysis showed an increasing trend of the contribution from terrestrial plants and wet to drought climate during 1873-2019. The sedimentary flux of ΣPAHs ranged between 11.71 and 1231.54 ng cm^-2 a^-1 and the percent of high-ring PAHs rose annually indicating enhanced anthropogenic activities. In the past 147 years, the results of present study highlight the influence of the agricultural and industrial economy on the catchment outlets.

Size-fractionated nonpolar organic compounds of traffic aerosol emissions in a highway tunnel

Size-fractionated aerosol samples (PM_0.25, PM_0.25-1, PM_1-2.5, and PM_2.5-10) were collected in a highway tunnel in Shanghai, China. The concentrations of nonpolar organic compounds (NPOCs), i.e., n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and hopanes in the aerosol samples at the tunnel inlet and outlet, emission factors (EFs) of individual NPOCs in PM₁₀, and EFs of size-fractionated individual NPOCs were analyzed comprehensively. NPOC concentrations in this tunnel were lower than the earlier tunnel results, which might be attributed to the tunnel configuration effect on the pollution dilution along the tunnel, in addition to the improvement of engine technology and fuel quality during past decades. n-Alkane homologs for C₁₄-C₃₅ exhibited a smooth hump-like distribution pattern with the most abundance at C₂₂ and 1-2 carbon number shifts of C_max in comparison to those in other tunnels due to different fleet and fuel compositions. The most abundant PAHs from diesel (e.g., Nap, Phe, Flu and Pyr) and gasoline (e.g., BghiF, BbkF, BeP, DBA and BghiP) vehicle emissions presented concentration increases of 1.8-5.8 times from the tunnel inlet to outlet. The individual n-alkane and PAH distributions exhibited obvious size dependence, while it was expected that the relative abundances and homolog distributions of hopanes were very similar for different size stages. Several diagnostic ratios, e.g., fossil/plant n-alkanes and LMW/HMW PAHs, were evidently size dependent, indicating different sources of size-fractionated n-alkanes and PAHs.

Sources and depositional changes of aliphatic hydrocarbons recorded in sedimentary cores from Admiralty Bay, South Shetland Archipelago, Antarctica during last decades

Organic biomarkers, as aliphatic hydrocarbons, are present in sedimentary organic matter and have been largely applied to the evaluation of recent environmental changes in the marine environment around the globe, including the Antarctic continent. Five sediment cores were taken in the Admiralty Bay, South Shetland Archipelago, Antarctica to evaluate changes in the signature of aliphatic hydrocarbons such as n-alkanes (n-C₁₀ to n-C₄₀) and isoprenoids as pristane and phytane, over the last decades. The total n-alkanes concentration ranged from 0.17 to 1.67 μg g^-1 (mean = 0.74 ± 0.42) which is considered low and similar to pristine sediments. Aliphatic hydrocarbons present in the sedimentary pool came mostly from terrestrial sources as Antarctic lichens and mosses, and from marine sources as the macroalgae forest debris and emergent macrophytes. Anthropogenic inputs of aliphatic hydrocarbons (e.g., petroleum and their by-products) may be neglected based on the multi-proxy approach used to distinct sources of these organic compounds. In general, no significant changes in the sources of aliphatic hydrocarbons were observed along the sediment cores; however, an increased aliphatic hydrocarbons input registered between 1975 and 1992 may be related to the increase in meltwater runoff and the relatively high abundance of marine producers more adapted to increased sea temperatures.

Key periods of peatland development and environmental changes in the middle taiga zone of Western Siberia during the Holocene

The response of peatlands to climate change can be highly variable. Through understanding past changes we can better predict the response of peatlands to future climate change. We use a multi-proxy approach to reconstruct the surface wetness and carbon accumulation of the Mukhrino mire (Western Siberia), describing the development of the mire since peat formation in the early Holocene, around 9360 cal. year BP. The mire started as a rich fen which initiated after paludification of a spruce forest (probably in response to a wetter climate), while the Mukhrino mire progressed to ombrotrophic bog conditions (8760 cal. year BP). This transition coincided with the intensive development of mires in Western Siberia and was associated with active carbon accumulation (31 g m-2 year-1). The ecosystem underwent a change to a tree-covered state around 5860 cal. year BP, likely in response to warming and possible droughts and this accompanied low carbon accumulation (12 g m2 year-1). If the future climate will be warmer and wetter, then regional mires are likely to remain a carbon sink, alternatively, a reversion to the wooded state with reduced carbon sink strength is possible.

Source identification of n-alkanes and isoprenoids using diagnostic ratios and carbon isotopic composition on crude oils and surface waters from the Gulf of Mexico

Diagnostic ratios and compound-specific isotopic analysis (CSIA) are two tools that can help identify and differentiate the petrogenic and biogenic sources of hydrocarbons found in environmental samples. The present study aims to evaluate the concentration and type of n-alkanes and isoprenoids found in the oligotrophic waters of the Gulf of Mexico (n = 14), and through the typical diagnostic ratios reported for n-alkanes and its carbon isotopic composition (δ¹³C) to establish and differentiate the possible source of the hydrocarbons. Additionally, crude oil samples (n = 10) extracted in the Gulf of Mexico were evaluated by CSIA as a possible source of hydrocarbons to the study area. We found that the CSIA of δ¹³C for n-alkanes (n-C₁₁ to n-C₃₀) and isoprenoids (pristane and phytane) found in the surface water samples varied from - 25.55 to - 37.59‰ and from - 23.78 to - 33.97‰ in the crude oil samples, values which are more related to petrogenic sources. An analysis of the δ¹³C for pristane vs. phytane suggests that only three surface water samples show an origin in common that those observed in crude oils of the Gulf of Mexico. A low incidence of odd- and even-numbered n-alkanes higher than n-C₂₅ in the water samples indicate low to negligible presence of terrigenous sources into the area, which was supported by the carbon isotopic composition of the individual n-alkanes.

Evaluation of Aliphatic Hydrocarbons in Surface Sediments of Lagoa Mirim (RS, Brazil)

In this study, the hydrocarbons (HCs) levels in sediments from Lagoa Mirim, situated in the south of Brazil, were verified. The methodology brought together stages of pre-sonification, soxhlet extraction, and determination by gas chromatography coupled with mass spectrometry (GC/MS). Ten sample points were evaluated where ∑n-alkanes varied between 1.46 µg kg^-1 ± 4.0% and 10.10 µg kg^-1 ± 17.6%. Diagnostic indexes were calculated, being: Carbon Preferential Index (CPI), terrestrial/aquatic ratio (TAR), unresolved complex mixture (UCM), UCM/∑n-alkanes ratio, and n-alkane ratio with Low molecular weight hydrocarbon and High molecular weight hydrocarbons (HMW/LMW). In general, the results of this study indicate a low anthropogenic impact in the environment.

Long-term environmental changes in the Geum Estuary (South Korea): Implications of river impoundments

We investigated a sediment core collected from the Geum Estuary through sedimentological and geochemical analyses. Three lithological units were classified based on sedimentological characteristics. Unit 1 and Unit 3 were geochemically distinct, while Unit 2 was the transitional phase between them. The geochemical results suggest that the contribution of terrestrial organic carbon (OC) to the sedimentary OC pool in the coarse-grained Unit 1 was lesser than that of fine-grained Unit 3. The excess activity (²¹⁰Pb_ex) and the sedimentation rate indicate that Unit 1 corresponded to 1977 Common Era (CE). Since the first dam construction on the Geum River began in 1975 CE, the deposition of Unit 1 in the Geum Estuary is likely associated with river impoundments, which reduce the delivery of fine-grained sediment and terrestrial OC to the estuary. This study highlights the role of river impoundments in altering the sedimentary OC and thus the sedimentary environment in the estuary.

Disturbance mechanisms of lacustrine organic carbon burial: Case study of Cuopu Lake, Southwest China

Lakes are important organic carbon (OC) traps in the global carbon cycle. Recent studies have shown that the rate of OC burial in lacustrine sediments is influenced by factors such as climate change, land-use change, and eutrophication. In this study, we use multiproxy methods to reveal the mechanisms of lacustrine sediment OC burial in an alpine lake (Cuopu Lake), in southwest China. Combined with the dating from ²¹⁰Pb_ex and n-alkanes distribution analysis using the Positive Matrix Factorization model, the sedimentary history was divided into five stages: religious activity (the 1840s-1880s), earthquake (the 1880s-1910s), garrison (the 1910s-1960s), transition (the 1960s-1990s), and ecotourism (the 1990s-2010s). During the earthquake stage, OC burial was dominated by terrestrial solids (>40%) and co-precipitated algae (>30%), with a rapid deposition rate (>4 mm a^-1) and low OC concentration (<4 mg g^-1). During the other stages, when the level of disturbance was relatively low, a change in nutrient conditions either promoted or inhibited plant growth, which influenced the type of buried OC. The contribution of OC derived from combustion sources varied from stage to stage. Severe anthropogenic disturbances have led to a significant increase in nutritional levels in the lake water, leading to an increase in the OC burial rate. Climate change, which leads to changes in temperature and rainfall, did not significantly influence OC burial, whereas nitrogen deposition (and associated ecological changes) was a significant determinant. When the general mechanism is dominant, the total nitrogen to inorganic phosphorus ratio is an effective indicator of OC burial due to its selective promotion of different plant types. In conclusion, our results suggest that lacustrine sediment OC burial is closely linked to physical and anthropogenic factors in Cuopu Lake, as well as similar montane lakes.

Occurrence, distribution, spatio-temporal variability and source identification of n-alkanes and polycyclic aromatic hydrocarbons in water and sediment from Loskop dam, South Africa

In this study, the spatial and temporal variations in the levels of C8-C40 n-alkanes and 18 polycyclic aromatic hydrocarbons (PAHs) in water and sediment from Loskop Dam (Mpumalanga Province South Africa), were investigated between 2015 and 2017. In addition, their sources, which have not been well defined, were also studied over the period. This water body is sourced from a historically contaminated water body, the Olifants River, which flows through areas where a range of industrial and agricultural activities take place. Mass crocodile and fish mortalities have been recorded in this aquatic system, and contamination by organic pollutants were highlighted as a contributing factor. The total average n-alkane concentrations in water and sediments ranged from 0.574±00811 to 18.8±1.39 µg/L and 4760±243 to 30700±906 µg/kg, respectively. Similarly, PAHs were detected at total average concentrations of between 0.150±00494 and 49.8±6.86 µg/L in water and 61.6±5.95 to 2618±300 µg/kg. n-Alkane and PAH diagnostic ratios indicated a mixture of sources of these compounds, attributed to terrestrial, submerged and floating plant material, as well as petrogenic and pyrogenic combustion. Inlet, middle and upper segment site clustering was observed with non-metric multidimensional scaling (NMDS) and hierarchical cluster analysis (HCA), mainly driven by the prevalence of PAHs at the inlet sites and n-alkanes in the upper reaches. By using indicator compounds, the sources of contamination could be predicted. The strategy described here can be applied to any water body for continuous long-term monitoring of pollutant levels and to identify sources attributing to water pollution.

Non-polar organic compounds, volatility and oxidation reactivity of particulate matter emitted from diesel engine fueled with ternary fuels in blended and fumigation modes

The present experimental study aims to examine the impacts of various fueling modes of operation on the particle-phase polycyclic aromatic hydrocarbons (PAHs) and n-alkanes (C16-C30), and volatility and oxidation reactivity of particulate matter (PM) emitted from a diesel engine fueled with a ternary fuel (80% diesel, 5% biodiesel and 15% ethanol (D80B5E15, volume %)) under four engine operating conditions. Four fueling modes, including diesel, blended, fumigation and combined fumigation + blended (F + B) modes were tested using pure diesel fuel for diesel mode and a constant fuel content of D80B5E15 for the blended, fumigation and F + B modes to create the same condition for comparing their impacts on the parameters investigated. The average results illustrate that both blended and fumigation modes can reduce the PAHs (-78.4% and -31.3%), benzo[a]pyrene equivalent (-81.7% and -38.9%), n-alkanes (-46.5% and -21.5%) and non-volatile substance fraction (-25.1% and -11.1%), but increase the high-volatile substance fraction (12.8% and 6.9%) and oxidation reactivity rate (34.0% and 4.9%), respectively compared to those of the diesel mode. While the effect of the blended mode on the parameters investigated is stronger than the fumigation mode. And the F + B mode has the effects in between the results of the blended and fumigation modes.

High daytime abundance of primary organic aerosols over Mt. Emei, Southwest China in summer

Organic molecular composition of fine aerosols in the free troposphere is poorly understood. Here, PM_2.5 (particles with aerodynamic diameters ≤ 2.5 μm) samples were collected at the summit of Mt. Emei (3080 m a.s.l.) in the Southwestern China on a daytime and nighttime basis during summer 2016 (June-July). The samples were analyzed by solvent-extraction followed by derivatization and gas chromatography/mass spectrometry (GC/MS). Four classes of organic compounds, i.e. n-alkanes, fatty acids, saccharides and lignin/resin acids were measured quantitatively. Fatty acids were found to be the most abundant species with an average concentration of 401 ± 419 ng m^-3 (range 25.7-1490 ng m^-3) in the daytime, similar to the average concentration at night (399 ± 447 ng m^-3, 19.6-1970 ng m^-3). However, the concentrations of biomass burning tracers (e.g., levoglucosan), primary biological aerosol tracers (e.g., mannitol and arabitol) and low molecular weight n-alkanes derived from fossil fuel combustion in daytime samples were obviously higher than those in nighttime samples. The results suggest that valley breezes transported a large number of aerosols and their precursors from the ground surface to the summit of Mt. Emei in the daytime. Estimated with tracer-based methods, the contributions of biogenic primary sources (plant debris, fungal spore, and biomass burning) to organic carbon was in the range of 3.28-83.5% (22.0 ± 17.5%) in the daytime and 3.45-37.4% (10.9 ± 8.97%) at night. As the largest contributor, biomass burning was an important anthropogenic/natural source of aerosol particles in the free troposphere over Mt. Emei. CAPSULE: Valley/mountain breeze is an important constraint to the temporal variations in organic aerosols over Mt. Emei.

Use of n-alkanes to trace erosion and main sources of sediments in a watershed in southern Brazil

Erosive processes can transport sediments containing nutrients, heavy metals and contaminants of organic and inorganic origin into bodies of water, therefore affecting the local ecosystem and the population that benefits from the water sources. In order to better understand the origin of sediment sources and establish mitigation measures, the use of the sediment fingerprinting technique has been highlighted. Thus, the present work had as objective to apply n-alkanes in order to trace and understand the main sources of organic matter in sediments and associate the results with land and soil occupation. The study area is located in the municipality of Rio Negrinho - Brazil, in the Saci river basin. Soil samples were collected and classified according to their use and occupation, as well as and samples of local vegetation to be used as reference. The distribution of n-alkanes in the sediments was compared with the distribution found in the vegetation and soil. Previously, a distribution pattern of n-alkanes had been identified in all major vegetation used to trace the source of organic matter and hence the soil. The concentrations of total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) and granulometry were also analyzed in the soil and sediment samples. Indexes between n-alkanes were used and applied to assess the source together with statistical analysis (PCA). In sum, the results showed that the sediments are mainly composed of Pinus taeda reforestation soils, as well as soil from the abandoned roads used to transport the cut trees, while the contribution of autochthonous sediments was found to be minimal. In this way, the fingerprint technique served as an auxiliary tool in order to establish measures for the good management of a river basin, bringing important information about the contributing sources of sediment to water bodies.

Diversity and degradative capabilities of bacteria and fungi isolated from oil-contaminated and hydrocarbon-polluted soils in Kazakhstan

Bacteria and fungi were isolated from eight different soil samples from different regions in Kazakhstan contaminated with oil or salt or aromatic compounds. For the isolation of the organisms, we used, on the one hand, typical hydrocarbons such as the well utilizable aliphatic alkane tetradecane, the hardly degradable multiple-branched alkane pristane, and the biaromatic compound biphenyl as enrichment substrates. On the other hand, we also used oxygenated derivatives of alicyclic and monoaromatic hydrocarbons, such as cyclohexanone and p-tert-amylphenol, which are known as problematic pollutants. Seventy-nine bacterial and fungal strains were isolated, and 32 of them that were clearly able to metabolize some of these substrates, as tested by HPLC-UV/Vis and GC-MS analyses, were characterized taxonomically by DNA sequencing. Sixty-two percent of the 32 isolated strains from 14 different genera belong to well-described hydrocarbon degraders like some Rhodococci as well as Acinetobacter, Pseudomonas, Fusarium, Candida, and Yarrowia species. However, species of the bacterial genus Curtobacterium, the yeast genera Lodderomyces and Pseudozyma, as well as the filamentous fungal genera Purpureocillium and Sarocladium, which have rarely been described as hydrocarbon degrading, were isolated and shown to be efficient tetradecane degraders, mostly via monoterminal oxidation. Pristane was exclusively degraded by Rhodococcus isolates. Candida parapsilosis, Fusarium oxysporum, Fusarium solani, and Rhodotorula mucilaginosa degraded cyclohexanone, and in doing so accumulate ε-caprolactone or hexanedioic acid as metabolites. Biphenyl was transformed by Pseudomonas/Stenotrophomonas isolates. When p-tert-amylphenol was used as growth substrate, none of the isolated strains were able to use it.

Organic molecular markers in marine aerosols over the Western Mediterranean Sea

A scientific campaign was undertaken along the Western sector of the Mediterranean Sea in the summer 2015 (26th Jun to 13th Jul), with the goal of gathering information about organic contaminants affecting marine aerosol over the Italian seas and with a special focus on changes in composition due to sources. 24 PM₁₀ atmospheric samples in total were chemically characterized, including polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (n-alkanes) and phthalate esters. Contemporarily, regulated gaseous toxicants (i.e. ozone, nitrogen oxides and sulfur dioxide) and meteorological parameters were recorded. Samplings were carried out inshore in front of harbors (N = 7) and along the cruise, both during the vessel shipping (N = 11, transects) and at its stops offshore (N = 6). Total PAH concentrations ranged from 0.03 to 1.94 ng/m³ and raised close to harbors and coastal sites, confirming that continental sources were responsible for the strong increase of pollution levels there compared to offshore. The percent composition and diagnostic ratio rates of PAHs were different for harbors, while transects were in agreement with offshore stops, possibly due to the different impact of pollution sources. n-Alkanes (C₂₁C₃₈) and the corresponding carbon preference index rates (CPI) were assessed; their values ranged 8.7-90 ng/m³ and 1.1-2.9 respectively, which suggested that fossil fuel combustion was the dominant source, though biogenic emission could contribute. Alkyl phthalates revealed wide variability in concentrations among aerosol samples. Moreover, long-range atmospheric transport and particle ageing effect induced by photo-oxidants were important factors controlling the composition of organic aerosols in the Mediterranean Sea air.

Primary biogenic and anthropogenic sources of organic aerosols in Beijing, China: Insights from saccharides and n-alkanes

Sugars and n-alkanes are important organic constituents of atmospheric fine particulate matter (PM_2.5). For better understanding their sources and seasonal variations in urban atmosphere, sugar compounds (anhydrosugars, sugars and sugar alcohols) and homologue n-alkanes (C₁₈-C₃₇) were studied in PM_2.5 samples collected from September 2013 to July 2014 in Beijing, China. In general, all measured compounds showed the lowest levels in summer. Higher concentrations of sugar compounds and n-alkanes were observed in winter, probably due to elevated combustion emissions (e.g., coal, biofuel and agricultural residue burning) and stable meteorological conditions during heating season. Levoglucosan was the major sugar species in all seasons particularly in autumn and winter, highlighting the significant contribution of biomass burning to fine organic aerosols throughout the whole year especially in cold seasons. Plant waxes contributed to n-alkanes the most in late spring (54.5%) and the least in winter (11.6%); while fossil fuel combustion had the largest contribution in winter (385 ng m^-3). The weak odd-carbon predominance of n-alkanes in wintertime aerosols also suggests fossil fuel combustion as the important source of organic aerosols in the heating season. Soil resuspension, fossil fuel combustion and biomass burning, and secondary sources are the main sources of OC in PM_2.5 at Beijing. The seasonal variation in source contributions indicates that meteorological condition is a key factor in controlling PM_2.5 levels. Furthermore, dust storms in spring can strongly enhance the atmospheric level of fine organic matter in Beijing.

Levels and sources of organic compounds in fine ambient aerosols over National Capital Region of India

The study presents the spatial and temporal variation of fine ambient aerosols (PM_2.5) over National Capital Region (NCR), India, during January to June 2016. The investigation includes three sampling sites, one in Delhi and two in the adjoining states of Delhi (Uttar Pradesh and Haryana), across NCR, India. The average PM_2.5 concentration was highest for Delhi (128.5 ± 51.5 μg m^-3) and lowest for Mahendragarh, Haryana (74.5 ± 28.7 μg m^-3), during the study period. Seasonal variation was similar for all the sites with highest concentration during winter and lowest in summer. PM_2.5 samples were analysed for organic compounds using gas chromatograph (GC). The concentration of three organic compound classes, n-alkanes (C11-C35), polycyclic aromatic hydrocarbons (PAHs), and phthalates, present in PM_2.5 samples has been reported. Diagnostic ratios for n-alkanes demonstrated that biogenic emissions were dominant over Mahendragarh while major contributions were observed from petrogenic emissions over Delhi and Modinagar, Uttar Pradesh. Molecular diagnostic ratios were calculated to distinguish between different sources of PAHs, which revealed that the fossil fuel combustion (diesel and gasoline emissions), traffic emissions, and biomass burning are the major source contributors. Health risk associated with human exposure of phthalates and PAHs was also assessed as daily intake (DI, ng kg^-1 day^-1) and lung cancer risk, respectively. Backward trajectory analysis explained the local, regional, and long-range transport routes of PM_2.5 for all sites. Principal component analysis (PCA) results summarized that the vehicular emissions, biomass burning, and plastic burning were the major sources of the PAHs and phthalates over the sampling sites.

Aerobic bacteria degrading both n-alkanes and aromatic hydrocarbons: an undervalued strategy for metabolic diversity and flexibility

Environmental pollution with petroleum toxic products has afflicted various ecosystems, causing devastating damage to natural habitats with serious economic implications. Some crude oil components may serve as growth substrates for microorganisms. A number of bacterial strains reveal metabolic capacities to biotransform various organic compounds. Some of the hydrocarbon degraders are highly biochemically specialized, while the others display a versatile metabolism and can utilize both saturated aliphatic and aromatic hydrocarbons. The extended catabolic profiles of the latter group have been subjected to systematic and complex studies relatively rarely thus far. Growing evidence shows that numerous bacteria produce broad biochemical activities towards different hydrocarbon types and such an enhanced metabolic potential can be found in many more species than the already well-known oil-degraders. These strains may play an important role in the removal of heterogeneous contamination. They are thus considered to be a promising solution in bioremediation applications. The main purpose of this article is to provide an overview of the current knowledge on aerobic bacteria involved in the mineralization or transformation of both n-alkanes and aromatic hydrocarbons. Variant scientific approaches enabling to evaluate these features on biochemical as well as genetic levels are presented. The distribution of multidegradative capabilities between bacterial taxa is systematically shown and the possibility of simultaneous transformation of complex hydrocarbon mixtures is discussed. Bioinformatic analysis of the currently available genetic data is employed to enable generation of phylogenetic relationships between environmental strain isolates belonging to the phyla Actinobacteria, Proteobacteria, and Firmicutes. The study proves that the co-occurrence of genes responsible for concomitant metabolic bioconversion reactions of structurally-diverse hydrocarbons is not unique among various systematic groups.

The discrimination of geoforensic trace material from close proximity locations by organic profiling using HPLC and plant wax marker analysis by GC

There is a need to develop a wider empirical research base to expand the scope for utilising the organic fraction of soil in forensic geoscience, and to demonstrate the capability of the analytical techniques used in forensic geoscience to discriminate samples at close proximity locations. The determination of wax markers from soil samples by GC analysis has been used extensively in court and is known to be effective in discriminating samples from different land use types. A new HPLC method for the analysis of the organic fraction of forensic sediment samples has also been shown recently to add value in conjunction with existing inorganic techniques for the discrimination of samples derived from close proximity locations. This study compares the ability of these two organic techniques to discriminate samples derived from close proximity locations and finds the GC technique to provide good discrimination at this scale, providing quantification of known compounds, whilst the HPLC technique offered a shorter and simpler sample preparation method and provided very good discrimination between groups of samples of different provenance in most cases. The use of both data sets together gave further improved accuracy rates in some cases, suggesting that a combined organic approach can provide added benefits in certain case scenarios and crime reconstruction contexts.

Apportioning source of erosion-induced organic matter in the hilly-gully region of loess plateau in China: Insight from lipid biomarker and isotopic signature analysis

Understanding the dynamics of organic matter (OM) at global and local scales is one of the challenges in the environmental sciences and i.e. terrestrial biogeochemistry. The accurate identification of OM is an essential element to achieve this goal. In our study, a novel application for quantitatively apportioning sources of eroded sedimentary OM from an eco-geomorphologic perspective was shown successfully via a coupled molecular n-alkane biomarkers and stable isotopic signatures (¹³C and ¹⁵N) along with elemental compositions (TOC and TN) using a Bayesian mixing model (SIAR). Soil source samples were collected from different land use types (i.e., forests, grassland, cropland, and fallow) and gully, which were probably transported downstream along the steep terrain. Meanwhile, three soil profiles with a total of 90 sediment samples were also sampled in check dam. The results indicated that cropland was the main sedimentary OM source in this catchment, contributing 29.5%, whereas the forests, grassland, fallow and gully contributed 12.17%, 15.39%, 21.53% and 21.85%, respectively. Although the molecular biomarker as a tracer was not valid solely, the combined approaches of n-alkanes biomarker and bulk parameters were efficient complements in tracing OM source in a hilly-gully region on the Loess Plateau of China.

n-Alkanes in sediments from the Yellow River Estuary, China: Occurrence, sources and historical sedimentary record

A total of 21 surface sediments from the Yellow River Estuary (YRE) and a sediment core from the abandoned Old Yellow River Estuary (OYRE) were analyzed for n-alkanes using gas chromatography-mass spectrometry (GC-MS). n-Alkanes in the range C₁₂-C₃₃ and C₁₃-C₃₄ were identified in the surface sediments and the core, respectively. The homologous series were mainly bimodal distribution pattern without odd/even predominance in the YRE and OYRE. The total n-alkanes concentrations in the surface sediments ranged from 0.356 to 0.572mg/kg, with a mean of 0.434mg/kg on dry wt.

BASIS

Evaluation of n-alkanes proxies indicated that the aliphatic hydrocarbons in the surface sediments were derived mainly from a petrogenic source with a relatively low contribution of submerged/floating macrophytes, terrestrial and emergent plants. The dated core covered the time period 1925-2012 and the mean sedimentation rate was ca. 0.5cm/yr. The total n-alkanes concentrations in the core ranged from 0.0394 to 0.941mg/kg, with a mean of 0.180mg/kg. The temporal evolution of n-alkanes reflected the historical input of aliphatic hydrocarbons and was consistent with local and regional anthropogenic activity. In general, the investigation on the sediment core revealed a trend of regional environmental change and the role of anthropogenic activity in environmental change.

Tracing of particulate organic C sources across the terrestrial-aquatic continuum, a case study at the catchment scale (Carminowe Creek, southwest England)

Soils deliver crucial ecosystem services, such as climate regulation through carbon (C) storage and food security, both of which are threatened by climate and land use change. While soils are important stores of terrestrial C, anthropogenic impact on the lateral fluxes of C from land to water remains poorly quantified and not well represented in Earth system models. In this study, we tested a novel framework for tracing and quantifying lateral C fluxes from the terrestrial to the aquatic environment at a catchment scale. The combined use of conservative plant-derived geochemical biomarkers n-alkanes and bulk stable δ¹³C and δ¹⁵N isotopes of soils and sediments allowed us to distinguish between particulate organic C sources from different land uses (i.e. arable and temporary grassland vs. permanent grassland vs. riparian woodland vs. river bed sediments) (p<0.001), showing an enhanced ability to distinguish between land use sources as compared to using just n-alkanes alone. The terrestrial-aquatic proxy (TAR) ratio derived from n-alkane signatures indicated an increased input of terrestrial-derived organic matter (OM) to lake sediments over the past 60years, with an increasing contribution of woody vegetation shown by the C₂₇/C₃₁ ratio. This may be related to agricultural intensification, leading to enhanced soil erosion, but also an increase in riparian woodland that may disconnect OM inputs from arable land uses in the upper parts of the study catchment. Spatial variability of geochemical proxies showed a close coupling between OM provenance and riparian land use, supporting the new conceptualization of river corridors (active river channel and riparian zone) as critical zones linking the terrestrial and aquatic C fluxes. Further testing of this novel tracing technique shows promise in terms of quantification of lateral C fluxes as well as targeting of effective land management measures to reduce soil erosion and promote OM conservation in river catchments.

Influence of continental organic aerosols to the marine atmosphere over the East China Sea: Insights from lipids, PAHs and phthalates

Total suspended particle (TSP) samples were collected during a marine cruise in the East China Sea from May 18 to June 12, 2014. They were analyzed for solvent extractable organic compounds (lipid compounds, PAHs and phthalates) using gas chromatography/mass spectrometry (GC/MS) to better understand the sources and source apportionment of aerosol pollution in the western North Pacific. Higher concentrations were observed in the terrestrially influenced aerosol samples on the basis of five-day backward air mass trajectories, especially for aerosols collected near coastal areas. Phthalates were found to be the dominant species among these measured compound classes (707±401ngm^-3 for daytime and 313±155ngm^-3 for nighttime), followed by fatty acids, fatty alcohols, n-alkanes and PAHs. In general, the daytime abundances for these compounds are higher than nighttime, possibly attributable to more intensive anthropogenic activities during the daytime. The factor analysis indicates that biomass burning, fungal activities and fossil fuel combustion maybe the main emission sources for organic aerosols over the East China Sea. This study demonstrates that the East Asian continent can be a natural emitter of biogenic and anthropogenic organics to the marine atmosphere through long-range transport, which controls the chemical composition and concentration of organic aerosols over the East China Sea.

Microextraction of polycyclic aromatic hydrocarbons by using a stainless steel fiber coated with nanoparticles made from a porous aromatic framework

A porous aromatic framework of type PAF-6 was synthesized and explored as a coating onto a steel wire for using in solid-phase microextraction of polycyclic aromatic hydrocarbons (PAHs), phthalate plasticizers, and n-alkanes. The extraction temperature, extraction time, salt concentration, agitation speed, desorption temperature, and desorption time were optimized. This method for SPME resulted in the enrichment factors ranging from 122 to 1090 for PAHs (naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene), from 122 to 271 for plasticizers (diisobutyl phthalate, dibutyl phthalate, benzyl butyl phthalate, dicyclohexyl phthalate), and from 9 to 113 for n-alkanes (n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane, n-hexadecane, n-octadecane and n-eicosane). The good extraction of the PAHs is assumed to be due to their π-stacking interaction and hydrophobic effect. The PAF-6 coated fibers are durable and can be reused more than 100 times without significant loss of extraction performance. In combination with GC-MS detection, the method has limits of detection in the range from 0.8 to 4.2 ng L^-1 in case of PAHs. The relative standard deviations for five replicate determinations of the PAHs by using one fiber are in the range from 5.2 to 8.5%. When using different fibers, they range from 7.1 to 9.6%. The recoveries of PAHs from water samples at a spiking level of 20 ng L^-1 are in the range from 89.5 to 103.1%, with relative standard deviations ranging from 4.0 to 9.3%. Graphical abstract A porous aromatic framework of type PAF-6 was synthesized and used as a novel coating for the solid-phase microextraction of polycyclic aromatic hydrocarbons prior to their determination by gas chromatography with mass spectrometric detection.

Distribution and controls of heavy metals and organic matter in the surface sediments of the Southern Yellow Sea, China

Accurate and effective determination of the source of heavy metals is essential for the treatment of marine ecological environments. This article attempts to combine geochemical composition data and hydrocarbon composition data to achieve this purpose. The concentrations of six heavy metals (Cu, Pb, Zn, Cr, Ni, and Co), grain size, total organic carbon (TOC) content, Al₂O₃ content, and aliphatic hydrocarbons (AHs) in 501 surface samples from the Southern Yellow Sea (SYS) were analyzed. The results showed that most sample sites ranged from not polluted to moderately polluted. However, Cu, Pb, Cr, and Ni may represent potential hazards, and the toxic probability for the combination of five metals (Cr, Cu, Ni, Zn, and Pb) was 21% for all sampling sites. The highest heavy metal concentrations were associated with the fine-grained sediments in the eastern area, especially in the northeastern muddy area. However, high concentrations of Pb and Cu were also found in some sites with coarse sediment in the western region. The lipid biomarkers showed that the n-alkanes were dominated by large odd-numbered carbon molecules, indicating that the organic matter in the sediments originated mainly from terrestrial plants. Principal component analysis (PCA) results, AH data, and the sediment distributions indicated that the organic matter and heavy metals in the SYS were mainly sourced from the Old Yellow River Delta, transported by ocean currents and deposited in the central SYS. In addition, a small proportion of the heavy metals originated from airborne dust. The spatial distribution pattern of the heavy metals in the surface sediments provides a basis for the protection of the marine ecological environments.

Cuticular Hydrocarbon Profiles Differentiate Tropical Fire Ant Populations (Solenopsis geminata, Hymenoptera: Formicidae)

The cuticular hydrocarbons (CHCs) from hexane rinses of workers from two Florida populations (dark and red forms) of the tropical fire ant, Solenopsis geminata, were separated by silica gel chromatography and identified by GC/MS analysis. Both the dark form and the red form produce similar CHCs with carbon chain lengths ranging from 17 to 35. However, the relative percentages of these CHCs were consistently different between the two color forms. The largest CHC component in the dark form is tricosane, and (Z)-9-tricosene for the red form. There were several significant differences in percent composition. For example, the dark form was characterized by a low tricosene:tricosane ratio (ca. 0.25), whereas this ratio was > 2.5 for the red form. The ratio of tricosene:tricosane can be used as a diagnostic biomarker to delimit the dark and red forms. Cluster analysis showed that the CHCs patterns of dark form colonies are completely separated from the CHC pattern of red form colonies. Differences in social behaviors like nestmate recognition and polygyny between workers from this dark form and the red form await further investigation.

Geochemical markers of sedimentary organic matter in Todos os Santos Bay, Bahia - Brazil. Indicators of sources and preservation

Natural stable isotopes, such as carbon (C) and nitrogen (N), are modern tools to assess geochemical processes. C and N in organic matter can carry fingerprints of their hydrologic flows and sedimentary processes, including any anthropogenic modification on the natural system. This study focuses on the determination of aliphatic and polycyclic aromatic hydrocarbons and isotopic ratio in the sediment of Todos os Santos Bay (TSB). The isotopic results of the total organic matter indicate varied contribution marine and terrigenous. Typical rates of PAHs mainly indicate a pyrogenic source and mixture between pyrogenic and petrogenic sources. Typical ratios for the n-alkanes indicate the presence of petroleum hydrocarbons. The isotopic composition of n-alkanes suggests a mixture of sources, with the possible contribution of petrogenic.

Effects of short-term weathering on the stable carbon isotope compositions of crude oils and fuel oils

A short-term simulated weathering experiment was performed on two crude oils and two heavy fuel oils under natural conditions to evaluate the effects of natural weathering processes by using gas chromatography-mass spectrometry combined with gas chromatography-isotopic ratio mass spectrometry. The results of diagnostic ratios of n-alkanes show that only odd to even predominance (OEP1, OPE2) and carbon preference index (CPI) remain stabilized during the 28 d weathering process, but they cannot effectively distinguish the four types of oils. Statistical analyses based on paired sample t-test and principal component analysis (PCA) revealed that stable carbon isotope compositions of n-alkanes in the four studied oils have no significant changes over the weathering time, and that the carbon isotope discrimination (Δδ¹³C) of n-alkanes is <3‰. We have provided evidence that the stable carbon isotope compositions of n-alkanes compared to n-alkanes diagnostic ratios significantly improve the efficiency and fidelity of the oil fingerprint identification.

Enzyme-mediated biodegradation of long-chain n-alkanes (C32 and C40) by thermophilic bacteria

Removal of long-chain hydrocarbons and n-alkanes from oil-contaminated environments are mere important to reduce the ecological damages, while bio-augmentation is a very promising technology that requires highly efficient microbes. In present study, the efficiency of pure isolates, i.e., Geobacillus thermoparaffinivorans IR2, Geobacillus stearothermophillus IR4 and Bacillus licheniformis MN6 and mixed consortium on degradation of long-chain n-alkanes C₃₂ and C₄₀ was investigated by batch cultivation test. Biodegradation efficiencies were found high for C₃₂ by mixed consortium (90%) than pure strains, while the pure strains were better in degradation of C₄₀ than mixed consortium (87%). In contrast, the maximum alkane hydroxylase activities (161 µmol mg^-1 protein) were recorded in mixed consortium system that had supplied with C₄₀ as sole carbon source. Also, the alcohol dehydrogenase (71 µmol mg^-1 protein) and lipase activity (57 µmol mg^-1 protein) were found high. Along with the enzyme activities, the hydrophobicity natures of the bacterial strains were found to determine the degradation efficiency of the hydrocarbons. Thus, the study suggested that the hydrophobicity of the bacteria is a critical parameter to understand the biodegradation of n-alkanes.

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

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

Source apportionment of PAHs and n-alkanes bound to PM1 collected near the Venice highway

n-Alkanes and polycyclic aromatic hydrocarbons (PAHs) bound to atmospheric particulate matter (PM₁) were investigated in a traffic site located in an urban area of Venice Province (Eastern Po Valley, Italy) during the cold season. Considering the critical situation affecting the Veneto Region concerning the atmospheric pollution and the general lack of information on PM₁ composition and emission in this area, this experimental study aims at determining the source profile, their relative contributions and the dispersion of finer particles. Four sources were identified and quantified using the Positive Matrix Factorization receptor model: (1) mixed combustions related to the residential activities, (2) agricultural biomass burning in addition to the resuspension of anthropogenic and natural debris carried by the wind, (3) gasoline and (4) diesel traffic-related combustions. The role of local atmospheric circulation was also investigated to identify the pollutant sources.

Mineral oil saturated hydrocarbons (MOSH) in female Fischer 344 rats; accumulation of wax components; implications for risk assessment

Female Fischer 344 rats were exposed to three MOSH mixtures: oils largely below and above C₂₅ (S-C25 and L-C25) and a 1:1 mixture of L-C25 with a wax; doses of 400, 1000 and 4000mg/kg feed were administered during 120days. MOSH were determined by on-line HPLC-GC-FID in liver, spleen, adipose tissue and the carcass. The composition of the hydrocarbons accumulated in the tissues was further analyzed by comprehensive two-dimensional GC (GC×GC). MOSH in the mass range of C_26-30 were more strongly accumulated than those between C_20-25, which does not support the present classification of MOSH differentiating at n-C₂₅ for risk assessment. Compared to the total of the MOSH, n-alkanes and n-alkyl monocyclic naphthenes were generally enriched in adipose tissue. In liver and spleen, n-alkanes up to C₂₅ were eliminated, but strongly accumulated at around C₃₀. Based on this profile, poor solubility and the melting points, it is hypothesized that crystallization protects these wax components against metabolism and elimination. In the liver, relative retention of n-alkanes decreased again beyond C₃₀, accentuated at high exposure, suggesting reduced absorption. Compared to the animal data, accumulation of n-alkanes from food sources, such as apples, into human tissues seems low, perhaps because of low absorption due to their presence in crystalline form. A series of dominant isoalkanes, accumulated in all tissues analyzed, was characterized, though without proposing a structure. Implications on present regulation of white mineral oil products are discussed.

Origin, toxicological and narcotic potential of sedimentary PAHs and remarkable even/odd n-alkane predominance in Bushehr Peninsula, the Persian Gulf

Surface sediments (n=17) were collected from 6 sites located in the coasts of the Bushehr Peninsula. ∑₁₆PAH concentrations were in the range of 285.9-1288ngg^-1 dw and the sediments were moderately polluted. Py, Ph, B(a)A and Flu showed >70% of the detected values in order of the mentioned rank. 4-ring PAHs were the dominant compounds and the molecular ratios presented the dominant pyrolytic source. The toxicity of PAHs for sediment dwelling life was averagely equivalent to occurrence of 0.08ngg^-1 of Dioxin in dw of the examined sediments. The evaluated narcotic potential (confidence level of 99%) was 0.027-3.04 and upper part of the Bushehr Peninsula, where the human population is more concentrated, showed more narcotic potential. ∑n-alkane concentrations (n-C₁₅-n-C₃₂) were in the range of 3.10-35.6μgg^-1 dw. The dominant distribution of even carbon number n-alkanes was traced back to a possibly autochthonous source.

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

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

Size distributions of n-alkanes, fatty acids and fatty alcohols in springtime aerosols from New Delhi, India

Size-segregated aerosol samples were collected in New Delhi, India from March 6 to April 6, 2012. Homologous series of n-alkanes (C₁₉C₃₃), n-fatty acids (C₁₂C₃₀) and n-alcohols (C₁₆C₃₂) were measured using gas chromatography/mass spectrometry. Results showed a high-variation in the concentrations and size distributions of these chemicals during non-haze, haze, and dust storm days. In general, n-alkanes, n-fatty acids and n-alcohols presented a bimodal distribution, peaking at 0.7-1.1 μm and 4.7-5.8 μm for fine modes and coarse modes, respectively. Overall, the particulate matter mainly existed in the coarse mode (≥2.1 μm), accounting for 64.8-68.5% of total aerosol mass. During the haze period, large-scale biomass burning emitted substantial fine hydrophilic smoke particles into the atmosphere, which leads to relatively larger GMDs (geometric mean diameter) of n-alkanes in the fine mode than those during the dust storms and non-haze periods. Additionally, the springtime dust storms transported a large quantity of coarse particles from surrounding or local areas into the atmosphere, enhancing organic aerosol concentration and inducing a remarkable size shift towards the coarse mode, which are consistent with the larger GMDs of most organic compounds especially in total and coarse modes. Our results suggest that fossil fuel combustion (e.g., vehicular and industrial exhaust), biomass burning, residential cooking, and microbial activities could be the major sources of lipid compounds in the urban atmosphere in New Delhi.

In situ detection of alkB2 gene involved in Alcanivorax borkumensis SK2(T) hydrocarbon biodegradation

This study aimed to develop a new assay based on the whole cell hybridization in order to monitor alkane hydroxylase genes (alkB system) of the marine bacterium Alcanivorax borkumensis SK2(T) commonly reported as the predominant microorganism responsible for the biodegradation of n-alkanes which are the major fraction of petroleum hydrocarbons. The assay based on the whole cell hybridization targeting alkB2 gene was successfully developed and calibrated on a pure culture of Alcanivorax borkumensis SK2(T) with a detection efficiency up to 80%. The approach was further successfully validated on hydrocarbon-contaminated seawater and provided cells abundance (6.74E+04alkB2-carryingcellsmL(-1)) higher of about one order of magnitude than those obtained by qPCR (4.96E+03alkB2genecopiesmL(-1)). This study highlights the validity of the assay for the detection at single cell level of key-functional genes involved in the biodegradation of n-alkanes.

along Dinaric Alps - Ecological and Taxonomic Aspects

Morphological characters and the composition of epicuticular leaf n-alkanes of two Satureja subspicata Bartl. ex Vis. subspecies (subsp. liburnica Šilić and subsp. subspicata) from nine natural populations along Dinaric Alps range were studied. Morphological characters were chosen based on Šilić's subspecies separation. Seventeen n-alkane homologues (C₁₉ - C₃₅ ) were identified using gas chromatography/mass spectrometry (GC/MS) and GC/flame ionisation detector (FID). The most abundant n-alkane in all populations was n-nonacosane (C₂₉ ), followed by n-hentriacontane (C₃₁ ), with the exception of Divača population where these two alkanes were co-dominant. Diversity and variability of n-alkane patterns and morphological characters and their relation to different geographic and bioclimatic parameters, including exposure, were analysed by several statistical multivariate methods (PCA, HCA, Discriminant Analysis, Mantel test). These tests showed clear separation of subsp. liburnica from subsp. subspicata, even though population Velebit showed separation from other subsp. liburnica populations based on phytochemical characters. Mantel test showed high correlation with geographical distribution in both investigated data sets. High correlation between morphological and phytochemical characters was also established. However, exposure can influence n-alkane profile, suggesting precaution while taking samples from natural habitats.