Low Hydrocarbon Concentrations Research Articles

Rapid dilution effectively decreases hydrocarbons following small oil spills, but impacts on microeukaryote communities are still observed

Dilution affects the distribution and weathering of oil following a spill into coastal seawater, but including dilution in experiments is rare. In open water, dilution is expected to rapidly reduce the concentrations of hydrocarbons, and estimates of impacts and microbial responses from batch experiments may overestimate what happens during a spill event. Three experiments carried out in the southern Gulf of St. Lawrence incorporated periods of incubation of natural microbial communities with either Heidrun medium crude or Bunker C fuel oil followed by dilutions using unexposed seawater. Higher concentrations of n-alkanes (C10 – C35) in Heidrun, resulted in higher initial total hydrocarbon concentrations in incubations with Heidrun compared to Bunker C. Similar polycyclic aromatic hydrocarbon concentrations and potential toxicity were measured in the water column for both oils. Dilution effectively decreased the hydrocarbon concentrations, reducing them to background levels after two dilutions (13.8-fold). Neither the abundance nor the diversity of the prokaryote community was strongly affected by the addition of oil. The natural coastal microbiome was dominated by bacteria that may be facultative hydrocarbon degraders. The abundance of phytoplankton and the diversity of the microeukaryote community decreased during the second incubation in response to both Heidrun and Bunker C, potentially due to photooxidative byproducts produced under full sunlight. Dilution appears to limit the bacterial response to oil, but low hydrocarbon concentrations may still be linked to impacts on the microeukaryote community.

Determination of intermolecular and intramolecular isotopic compositions of low-abundance gaseous hydrocarbons using an online hydrocarbon gas concentration method

The stable isotopic composition of natural gas can be used to identify its origin and source. However, low concentrations of gaseous hydrocarbons in high-mature natural and shale gases hinder accurate determination of their compound- and position-specific isotopic compositions. In this study, an online C2+ hydrocarbon gas concentration system combined with gas chromatography–isotope ratio mass spectrometry (GC–IRMS) or gas chromatography–pyrolysis–gas chromatography–isotope ratio mass spectrometry (GC–Py–GC–IRMS) was developed to determine compound- and position-specific isotopic compositions of low-abundance gaseous hydrocarbons. The lower limit of the gas concentration required for isotope ratio determination using the online concentration system is 0.001% (0.003%) for compound-specific carbon (hydrogen) isotopes and 0.005% for position-specific carbon isotopes and is thus applicable to most natural gas samples. The online concentration technique does not cause significant isotopic fractionation effects, and the combination with GC–IRMS and GC–Py–GC–IRMS can accurately and precisely determine the compound-specific δ13C and δD values of low-content C2+ gaseous hydrocarbons and the position-specific δ13C values (δ13Ca, δ13Cb, and SP values) of propane in low-content propane samples, respectively. The application of our method to two natural gas samples from the Ordos and Sichuan basins further confirms that the online concentration method allows simple and rapid determination of the compound- and position-specific isotopic compositions of low-abundance gaseous hydrocarbons.

Response of the soil microbial community to petroleum hydrocarbon stress shows a threshold effect: research on aged realistic contaminated fields.

Microbes play key roles in maintaining soil ecological functions. Petroleum hydrocarbon contamination is expected to affect microbial ecological characteristics and the ecological services they provide. In this study, the multifunctionalities of contaminated and uncontaminated soils in an aged petroleum hydrocarbon-contaminated field and their correlation with soil microbial characteristics were analyzed to explore the effect of petroleum hydrocarbons on soil microbes. Soil physicochemical parameters were determined to calculate soil multifunctionalities. In addition, 16S high-throughput sequencing technology and bioinformation analysis were used to explore microbial characteristics. The results indicated that high concentrations of petroleum hydrocarbons (565-3,613 mg•kg-1, high contamination) reduced soil multifunctionality, while low concentrations of petroleum hydrocarbons (13-408 mg•kg-1, light contamination) might increase soil multifunctionality. In addition, light petroleum hydrocarbon contamination increased the richness and evenness of microbial community (p < 0.01), enhanced the microbial interactions and widened the niche breadth of keystone genus, while high petroleum hydrocarbon contamination reduced the richness of the microbial community (p < 0.05), simplified the microbial co-occurrence network, and increased the niche overlap of keystone genus. Our study demonstrates that light petroleum hydrocarbon contamination has a certain improvement effect on soil multifunctionalities and microbial characteristics. While high contamination shows an inhibitory effect on soil multifunctionalities and microbial characteristics, which has significance for the protection and management of petroleum hydrocarbon-contaminated soil.

Long-term exposure to low concentrations of polycyclic aromatic hydrocarbons and alterations in platelet indices: A longitudinal study in China.

Long-term exposure to low polycyclic aromatic hydrocarbon (PAH) concentration may ave detrimental effects, including changing platelet indices. Effects of chronic exposure to low PAH concentrations have been evaluated in cross-sectional, but not in longitudinal studies, to date. We aimed to assess the effects of long-term exposure to the low-concentration PAHs on alterations in platelet indices in the Chinese population. During 2014-2017, we enrolled 222 participants who had lived in a village in northern China, 1-2 km downwind from a coal plant, for more than 25 years, but who were not employed by the plant or related businesses. During three follow-ups, annually in June, demographic information and urine and blood samples were collected. Eight PAHs were tested: namely 2-hydroxynaphthalene, 1-hydroxynaphthalene, 2-hydroxyfluorene, 9-hydroxyfluorene (9-OHFlu), 2-hydroxyphenanthrene (2-OHPh), 1-hydroxyphenanthrene (1-OHPh), 1-hydroxypyrene (1-OHP), and 3-hydroxybenzo [a] pyrene. Five platelet indices were measured: platelet count (PLT), platelet distribution width (PDW), mean platelet volume (MPV), platelet crit, and the platelet-large cell ratio. Generalized mixed and generalized linear mixed models were used to estimate correlations between eight urinary PAH metabolites and platelet indices. Model 1 assessed whether these correlations varied over time. Models 2 and 3 adjusted for additional personal information and personal habits. We found the following significant correlations: 2-OHPh (Model1 β1 = 18.06, Model2 β2 = 18.54, Model β3 = 18.54), 1-OHPh (β1 = 16.43, β2 = 17.42, β3 = 17.42), 1-OHP(β1 = 13.93, β2 = 14.03, β3 = 14.03) with PLT, as well as 9-OHFlu with PDW and MPV (odds ratio or Model3 ORPDW[95%CI] = 1.64[1.3-2.06], ORMPV[95%CI] = 1.33[1.19-1.48]). Long-term exposure to low concentrations of PAHs, indicated by2-OHPh, 1-OHPh, 1-OHP, and 9-OHFlu, as urinary biomarkers, affects PLT, PDW, and MPV. 9-OHFlu increased both PDW and MPV after elimination of the effects of other PAH exposure modes.

Valorization of coffee industry wastes: Comprehensive physicochemical characterization of coffee silverskin and multipurpose recycling applications

Every year, the coffee supply chain produces tons of waste materials from the processing of the coffee bean. Coffee silverskin (CS) is the only waste product from the coffee bean roasting phases but as roasting is a key step in obtaining the coffee beverage, there are tons of CS collected and thrown away by coffee roasting industries. This study is based on the characterization of this integument, with a view to its use in nutritional, nutraceutical and industrial fields. From the results obtained, silverskin can be used in the food sector for its nutritional profile with a good amount of protein (18.9%) and total dietary fiber (34.7%) andits low-fat content (3.0%). Food safety was also determined by evaluating the low levels of contaminants such as ochratoxin A (OTA) and acrylamide (AA), with values < 0.1 mg/kg and <0.02 mg/kg respectively. Low concentrations of heavy metals and polycyclic aromatic hydrocarbons (PAHs) completed the safety-related overview in terms of CS contamination. For the nutraceutical aspect, an in-silico analysis of the peptide fraction was proper to evaluate the presence of angiotensin-converting enzyme (ACE) inhibitory peptides, antioxidants and dipeptidyl peptidase (DPP) IV inhibitors with promising uses for the treatment of diabetes and its side effects. Finally, through morphological-structural characterization of CS, the main constituents such as lignin, cellulose and hemicellulose were identified spectrally by Fourier transform infrared spectroscopy (FT-IR) and solid-state CP/MAS 13C NMR spectroscopy. The CS thermostability was monitored by thermogravimetric (TG) analysis, and the tegument surface was evaluated by Scanning Electron Microscopy (SEM) and volumetric nitrogen adsorption analysis. This information provides a broader view of the possible uses of CS as a filler for biocomposite materials. Therefore, from the perspective of recovering waste materials from food supply chains, coffee silverskin could be a good product to focus on.

Marine Sponges in a Snowstorm - Extreme Sensitivity of a Sponge Holobiont to Marine Oil Snow and Chemically Dispersed Oil Pollution.

Holobionts formed by a host organism and associated symbionts are key biological units in marine ecosystems where they are responsible for fundamental ecosystem services. Therefore, understanding anthropogenic impacts on holobionts is essential. Sponges (Phylum Porifera) are ideal holobiont models. They host a complex microbial community and provide ecosystem services including nutrient cycling. At bathyal depths, sponges can accumulate forming dense sponge ground habitats supporting biodiverse associated communities. However, the impacts of spilled oil and dispersants on sponge grounds cannot be understood without considering exposures mediated through sponge filtration of marine snow particles. To examine this, we exposed the model sponge Halichondria panicea to oil, dispersant and “marine oil snow” contaminated seawater and elucidate the complex molecular response of the holobiont through metatranscriptomics. While the host response included detoxification and immune response pathways, the bacterial symbiotic response differed and was at least partially the result of a change in the host environment rather than a direct response to hydrocarbon exposure. As the sponge host reduced its pumping activity and internal tissue oxygen levels declined, the symbionts changed their metabolism from aerobic to anaerobic pathways possibly via quorum sensing. Furthermore, we found evidence of hydrocarbon degradation by sponge symbionts, but sponge mortality (even when exposed to low concentrations of hydrocarbons) implied this may not provide the holobiont with sufficient resilience against contaminants. Given the continued proposed expansion of hydrocarbon production into deep continental shelf and slope settings where sponge grounds form significant habitats it is important that dispersant use is minimised and that environmental impact assessments carefully consider the vulnerability of sponge holobionts.

Microbial community response to simulated diluted bitumen spills in coastal seawater and implications for oil spill response.

Oil spills in coastal waters can have devastating impacts on local ecosystems, from the microscopic base through to mammals and seabirds. Increasing transport of diluted bitumen has led to concerns about how this novel product might impact coastal ecosystems. A mesocosm study determined that the type of diluent and the season can affect the concentrations of hydrocarbons entering the water column from a surface spill. Those same mesocosms were sampled to determine whether diluent type and season also affected the microbial response to a surface spill. Overall, there were no differences in impacts among the three types of diluted bitumen, but there were consistent responses to all products within each season. Although microbial abundances with diluted bitumen rarely differed from unoiled controls, community structure in these organisms shifted in response to hydrocarbons, with hydrocarbon-degrading bacteria becoming more abundant. The relative abundance of heterotrophic eukaryotes also increased with diluted bitumen, with few photosynthetic organisms responding positively to oil. Overall shifts in the microbial communities were minimal relative to spills of conventional oil products, with low concentrations of hydrocarbons in the water column. Oil spill response should focus on addressing the surface slick to prevent sinking or stranding to minimize ecosystem impacts.

The pathways of the phthalic anhydride selectivity and yield increase at C4-C5-hydrocarbons oxidation

The investigation of n-butane and n-pentane oxidation in system with two consecutive reactors confirmed the mechanism of phthalic anhydride formation by Diels-Alder reaction between maleic anhydride and C4 unsaturated hydrocarbons. The process is limited by low stationary concentration of C4 unsaturated hydrocarbons in reaction mixture which is connected with high rate of their oxidation to maleic anhydride. It was shown that n-butane oxidation leads to formation of maleic anhydride only but the introduction of unsaturated C4-hydrocarbons on inlet of the second catalytic reactor accompanied by phthalic anhydride appearance on outlet of these two consecutive reactors system. It was established that in case of 1,3-butene introduction in the second reactor the quantity of phthalic anhydride formed is more than in case of 2-butene addition. It was predicted that a decrease of the temperature in the second reactor can leads to an increase the phthalic anhydride selectivity and its yield as result of Diels-Alder reaction effectiveness. This assumption was confirmed by experimental results. In results the method of phthalic anhydride production by the use of two consecutive reactors was proposed. The summary yield of this product on this new process can reach up to 35 mol. %. In the case of n-pentane oxidation the formation of maleic and phthalic anhydrides was observed with excess of first product but the introduction of unsaturated C4-hydrocarbons in the inlet of second reactor leads to an increase of the phthalic anhydride concentration and its selectivity and yield. In result the yield of phthalic anhydride equal to 35 mol. % can be obtained. So, the proposed by us mechanism of phthalic anhydride was confirmed by new experimental results and other pathways for the selectivity and yield of this product can be predicted.

Anthropogenic effects on the marine environment adjacent to Palmer Station, Antarctica

AbstractLocalized contamination from research-related activities and its effects on macrofauna communities in the marine environment were investigated at Palmer Station, a medium-sized Antarctic research station. Relatively low concentrations of polycyclic aromatic hydrocarbons (PAHs; 32–302 ng g-1) and total petroleum hydrocarbons (TPHs; 0.9–8.9 μg g-1) were detected in sediments adjacent to the sewage outfall and pier, where most human activities were expected to have occurred, and at even lower concentrations at two seemingly reference areas (PAHs 6–30 ng g-1, TPHs 0.03–5.1 μg g-1). Elevated concentrations of PAHs in one sample taken in one reference area (816 ng g-1) and polychlorinated biphenyls (353 ng g-1) and dichloro-diphenyl-trichloroethane (3.2 and 25.3 ng g-1) in two samples taken adjacent to the sewage outfall indicate spatial heterogeneity of localized sediment contamination. Limpet (Nacella concinna) tissues collected adjacent to Palmer Station had high concentrations of PAHs, copper, lead, zinc and several other metals relative to outlying islands. Sediment and limpet tissue contaminant concentrations have decreased since the early 1990s following theBahía Paraísospill. Natural sediment characteristics affected macrofaunal community composition more than contamination adjacent to Palmer Station, presumably because of the low overall contamination levels.

Исследование компонентного состава органического вещества отложений Восточно-Предкавказской нефтегазоносной области по результатам литолого-петрофизических и геохимических исследований

This study introduces results of lithological, petrophysical and geochemical investigation of Lower Cretaceous (K1) and Middle Jurassic (J2a-b) rocks of East Pre-Caucasian basin. According to pyrolytic and bituminological studies method of separate determination of kerogen and bitumen concentration been developed. In accordance with this method differentiation of organic matter components in different lithotypes of rocks been described. Also relationship between bitumen and kerogen concentrations been revealed. The majority of samples have poor to fair organic richness and poor source potential. Kerogen type is commonly presented by type III and stages of maturity characterized by stages PC3 to MC3. Bitumen compounds have low concentrations of asphaltenes and aromatic hydrocarbons and mainly contains light and heavy resins. Based on petrophysical and geochemical studies a close relationship between the concentration of organic carbon and the weight concentration of potassium nuclides was obtained. This relationship indicates that kerogen in the sediments under consideration is associated with clay minerals, which is also confirmed by the mineral composition of the rocks.

Integrating physical, chemical and biological data to understand fate, behaviour and effects of diluted bitumen in coastal waters

ABSTRACT: 1141488 Production of bitumen from oil sands is predicted to rise over the next decade. Some of this increased production will be transported to coastal areas for export. While some product will be transported via rail, the majority is likely to be transported through pipelines as diluted bitumen. This unconventional oil product is a mixture of the highly viscous bitumen with differing amounts of diluent, which can include condensates, synthetic crudes or conventional crudes. As a mixture of products, the behaviour of diluted bitumen may differ from conventional heavy crude oils following a spill. This is of concern in Canada as the main transportation route for exporting diluted bitumen will go through the Salish Sea, home to endangered southern resident killer whales, economically important commercial and traditional fisheries including Pacific salmon, and millions of people. Knowing how diluted bitumen products will behave and their potential impacts if a spill occurs in these coastal waters is important in developing an effective response plan. The Centre for Offshore Oil, Gas and Energy Research (COOGER) within Fisheries and Oceans Canada (DFO) has been carrying out research to characterize and predict the fate and behaviour of diluted bitumen products in marine environments over the last seven years. Using a combination of small-scale microcosms, medium-scale mesocosms, large-scale weathering and wave tank studies as well as field experiments, we have collected a broad range of data providing insights into how diluted bitumen might behave following a spill. Our research suggests that diluted bitumen will weather rapidly, with density and viscosity increasing significantly over the first 48 h. Low concentrations of hydrocarbons are typically detected in the water column, even in the presence of high energy breaking waves. The amount of weathering and water column hydrocarbons vary with season, but overall the microbial community shows a small response to the presence of diluted bitumen. Conventional spill response technologies may be used within the first 48 h of a spill, but extensive weathering will further limit their effectiveness. While the studies provide a more complete understanding of the fate and behaviour of diluted bitumen in coastal waters, there are important questions yet to be answered, some of which are presented here.

Analysis of Spatial Variability of Water Chemistry Indicators of the Rivers within Oilfields of Khanty-Mansi Autonomous Okrug – Ugra

An increase of technogenic load on the catchment area with a decrease of the volume of water protection measures leads to spread of surface water pollution. The paper considers the chemical composition of surface waters in Khanty-Mansi autonomous okrug – Ugra. The technique for analyzing the chemical composition of surface waters based on the combined application of the method of cluster analysis is presented. In this work, the concentration of metal ions in the rivers under study was determined. It was found that concentrations of iron and zinc ions exceeded the maximum permitted concentrations for fishery rivers (MPC) in 100% of samples, as for copper concentration an excess of MPC was noted in some cases. The spatial dynamics of the distribution of chlorides and oil hydrocarbons in surface waters is considered. According to the monitoring data, the analyzed surface water samples had very low concentrations of chlorides and oil hydrocarbons.

Trace metals as indicators of tree rooting in bituminous soils

AbstractIn some reclamation practices, following bitumen mining in the Canadian Boreal forest, overburden containing low concentrations of hydrocarbons (&lt;8% of bulk soil volume) is buried under suitable soils. Residual hydrocarbons may influence the growth of trees used in afforestation of reclaimed sites, thus determining whether roots interact with buried bitumen is a key to predicting reclamation success. As the organic fraction of bitumen is enriched in vanadium, nickel, molybdenum, and rhenium, dendrochemistry may be a method to determine whether tree roots are interacting with bitumen without disturbing soils. We analyzed trace concentrations of these metals in soil, soil pore water, and tree cores of Pinus banksiana growing on natural bitumen deposits and sites free of bitumen. If roots are present within bitumen and passively uptake trace metals during water transport and wood growth, metals enriched in bitumen should be present in higher concentrations in the woody tissue of trees growing in bituminous soils compared to trees growing in bitumen‐free soils. Concentrations of nickel in trees growing on shallow bitumen deposits were approximately 3× higher than those growing in bitumen‐free soils. The concentration of vanadium (1.33 μg kg−1 in younger wood and 3.21 μg kg−1 in older wood) was also elevated in trees on bituminous sites, though not significantly. Molybdenum concentrations decreased by ~25% in trees growing on bituminous sites, likely an outcome of soil pH. This research supports the use of dendrochemistry to investigate, and potentially monitor, tree rooting at depth in substrates with signature metals.

The bioavailability of oil droplets trapped in river gravel by hyporheic flows.

Little is known about the fate of oil spills in rivers. Hyporheic flows of water through river sediments exchange surface and groundwater and create upwelling and downwelling zones that are important for fish spawning and embryo development. Risk assessments of oil spills to rivers do not consider the potential for hyporheic flows to carry oil droplets into sediments and the potential for prolonged exposure of fish to trapped oil. This project assessed whether oil droplets in water flowing through gravel will be trapped and whether hydrocarbons partitioning from trapped oil droplets are bioavailable to fish. Columns packed with gravel were injected with oil-in-water dispersions prepared with light crude, medium crude, diluted bitumens, and heavy fuel oil to generate a series of oil droplet loadings. The concentrations of oil trapped in the gravel increased with oil loading and viscosity. When the columns were perfused with clean water, oil concentrations in column effluents decreased to the detection limit within the first week of water flow, with sporadically higher concentrations associated with oil droplet release. Despite the low concentrations of hydrocarbons measured in column effluent, hydrocarbons were bioavailable to juvenile rainbow trout (Oncorhynchus mykiss) for more than three weeks of water flow, as indicated by strong induction of liver ethoxyresorufin-o-deethylase activity. These findings indicate that ecological risk assessments and spill response should identify and protect areas in rivers sensitive to contaminant trapping.

Technologies for remote lidar sensing of the surface to detect low concentrations of hydrocarbons in Siberia and the far north

The results of research in the field of remote sensing using the technologies of radar and laser detection of hydrocarbons raw materials aimed at the search, localization and topographic location of discovered oil and gas field, the determination of leaks and atmospheric pollution by hydrocarbon gases (e.g. methane) are presented. The main problems with sounding are revealed. To determine the extremely low concentrations of methane in the atmosphere, the main constraining factors were determined and the need to suppress side interference arising on the probing path of the laser beam was shown. To formulate requirements for the sensitivity of equipment and the accuracy of software calculations, the choice of a mathematical model of the path of the laser beam is justified. A modification of the known model is proposed to represent the lidar path based on the differential absorption method taking into account correction coefficients of molecular and aerosol absorption and scattering. Thus, the presented model is a set of methods for providing more accurate and localized data for the implementation of a hardware-software complex.

QuEChERS applicability to measure land snail polycyclic aromatic hydrocarbons for risk assessment

The methods conventionally used for the extraction of organic pollutants in different environmental matrices are not suitable for measuring low concentrations of polycyclic aromatic hydrocarbons bioaccumulated in terrestrial snails that are both indicator of soil quality and a food item of various consumers including human being. A protocol, adapted from the QuEChERS method, originally designed for the extraction of pesticides in fruits and vegetables, in combination with gas chromatography-triple quadrupole mass spectrometry was developed to assess the bioavailability of polycyclic aromatic hydrocarbon extraction at low levels in soils to the soil quality bioindicator Cantareus aspersus. Bioaccumulation was measured in snails exposed ex situ for 28 days under controlled conditions to soils lightly or highly contaminated (sum of 16 molecules in the range 3.32–140 mg kg−1 dry weight). The method was validated (low limits of detection, linear calibration curves, good precision and trueness) and found to be efficient to show that strongly contaminated soils were not necessarily those that presented the highest bioavailable organics concentrations. This methodology offers a tool to assess the environmental risk of contaminated soils and to prioritize the management of polycyclic aromatic hydrocarbons-contaminated soils.

Pollution characteristics of aromatic hydrocarbons in the groundwater of China

Much of the world's groundwater supply has been contaminated by aromatic hydrocarbons originating from anthropogenic sources. To study the occurrence and distribution characteristics of aromatic hydrocarbons in groundwater, 24 aromatic hydrocarbon compounds were selected: Five BTEX compounds (benzene, toluene, ethylbenzene, o-xylene, m-xylene, and p-xylene), 10 alkyl-substituted benzene, and 9 halogenated aromatics. These aromatic hydrocarbons were then analyzed from 355 samples collected from across China. Results indicated that aromatic hydrocarbons were detected in 59 out of 355 samples. Of the selected aromatic hydrocarbons, BTEX compounds were detected with high frequency and at low concentrations; comparatively, halogenated aromatics were detected with low frequency and at high concentrations. The aromatic hydrocarbon characteristics found in both karst and pore groundwater samples were then determined using their respective hydrogeological conditions and corresponding human activities. In karst groundwater, BTEX compounds were the most frequently detected aromatic hydrocarbon. The high detection frequencies of aromatic hydrocarbons were caused by their rapid migration, owing to the developed conduit system in the sampled karst area. The low concentrations of aromatic hydrocarbons in karst groundwater samples were caused by low-intensity human activity along with special hydrogeological conditions with higher redox potential and the unique compositions of aromatic hydrocarbons. Alkyl-substituted aromatics and halogenated aromatics were detected at higher concentrations in pore groundwater, owing to high-intensity human activity. Aromatic hydrocarbon pollution was gradually decreased along piedmont-alluvial plain-coast line, owing to a decrease in aquifer vulnerability. These were positively correlated with the size of the aquifer's particles. Samples with a high accumulative concentration of these aromatic hydrocarbons tended to occur in pore groundwater with a high concentration of either SO42− or Cl−.

Volcanic gas emissions from Taftan and Damavand, the Iranian volcanoes

Volcanic gas sampling and SO2 flux measurements were performed on Taftan volcano (3920 m height, SE Iran, Makran volcanic arc) and Damavand volcano (5610 m height, Northern Iran, Alborz Mountains). Both volcanoes possess near-summit fumarolic fields with moderately intensive gas jets and temperatures up to 160 °C (Taftan) and 175 °C (Damavand). Gases of both volcanoes contain (mmol/mol): H2O (910–930), CO2 (50–80), SO2 (3–7), H2S (2–5.5), HCl (5–8.2) and HF (0.1–0.13). Both volcanoes are also similar in terms of minor gas species (mmol/mol): He (0.0005–0.0011), H2 (0.00077–0.0046), N2(ex) (0.15–0.30) and Ar(ex) (0.0006–0.0012), where subscript “ex” denotes non-atmospheric fraction. δD–δ18O systematics has shown that Damavand fumarolic gases contain 60–65% of magmatic fraction whereas the Taftan emissions correspond to almost pure magmatic (“andesitic”) vapor. Low amount of nitrogen in Taftan gases and its isotopic composition may be explained by low input of nitrogen-containing organic matter with the subducting slab due to specific geometry of the Makran subduction zone, namely, by the presence of an accretionary prism of a considerable size. The origin of high CH4 content in Damavand gases and very low concentrations of C2H6 and higher hydrocarbons (0.65 mmol/mol; CO2/CH4 ~ 80; CH4/C2H6 ~ 104) is unclear. Fumaroles of Taftan volcano are poor in CH4, similar to many other arc volcanoes (CO2/CH4 ~ 105). 3He/4He isotopic composition expressed as R/Ra was measured at 7.0–7.5 for Taftan and 6.65 for Damavand, corresponding to the CO2/3He ratio of ~1.0E+10. The δ34S of the total sulfur is +7.6 ± 2‰ (2σ) for Taftan fumaroles and + 8.1 ± 2‰ (2σ) for Damavand fumaroles; δ13C (CO2) is −5.9 ± 2.0‰ (Damavand) and − 4.3 ± 0.15‰ (Taftan). Concentrations of major gas species (H2O/CO2/S/HCl ratios) and isotopic data (R/Ra, CO2/3He, δ34S) show that the volcanic gas composition on both volcanoes have a distinct arc signature. This conclusion is especially important for the intraplate Damavand volcano, which has an uncertain tectonic affinity but according to the latest geochemical studies was considered having hotspot/rift origin. Mini-DOAS measurements of the SO2 fluxes showed 20 ± 12 t/d SO2 at Taftan and 43 ± 20 t/d SO2 at Damavand, which places both volcanoes as small SO2 emitters.

Estimating persistent oil contamination in tropical region using vegetation indices and random forest regression

The persistence of soil contamination after cessation of oil activities remains a major environmental issue in tropical regions. The assessment of the contamination is particularly difficult on vegetated sites, but promising advances in reflectance spectroscopy have recently emerged for this purpose. This study aimed to exploit vegetation reflectance for estimating low concentrations of Total Petroleum Hydrocarbons (TPH) in soils. A greenhouse experiment was carried out for 42 days on Cenchrus alopecuroides (L.) under realistic tropical conditions. The species was grown on oil-contaminated mud pit soils from industrial sites, with various concentrations of TPH. After 42 days, a significant decrease in plant growth and leaf chlorophyll and carotenoid contents was observed for plants exposed to 5–19 g kg−1 TPH in comparison to the controls (p < 0.05). Conversely, pigment contents were higher for plants exposed to 1 g kg−1 TPH (hormesis phenomenon). These modifications proportionally affected the reflectance of C. alopecuroides at leaf and plant scales, especially in the visible region around 550 and 700 nm. 33 vegetation indices were used for linking the biochemical and spectral responses of the species to oil using elastic net regressions. The established models indicated that chlorophylls a and b and β-carotene were the main pigments involved in the modifications of reflectance (R2 > 0.7). The same indices also succeeded in estimating the concentrations of TPH using random forest regression, at leaf and plant scales (RMSE = 1.46 and 1.63 g kg−1 and RPD = 5.09 and 4.44, respectively). Four out of the 33 indices contributed the most to the models (>75%). This study opens up encouraging perspectives for monitoring the cessation of oil activities in tropical regions. Further researches will focus on the application of our approach at larger scale, on airborne and satellite imagery.

A Global Proteomic Change in Petroleum Hydrocarbon-Degrading Pseudomonas aeruginosa in Response to High and Low Concentrations of Petroleum Hydrocarbons.

In this study, iTRAQ analysis and bioinformatics analysis were used to reveal the changes in key proteins induced by different concentrations of petroleum hydrocarbons during the biodegradation of petroleum hydrocarbons in Pseudomonas aeruginosa P6. Sixty-three proteins were identified as differentially expressed proteins, and all of them were strongly associated with the cellular processes related to the biodegradation of petroleum hydrocarbons. The results further showed that among the differentially expressed proteins, 3 chemotaxis-related proteins, 10 terminal oxidation of short-chain alkane-related proteins, and 13 transmembrane transport-related proteins were down regulated, while 1 uptake of petroleum hydrocarbon-related protein, 3 terminal oxidation of long-chain alkane-related proteins, 4 dehydrogenation-related proteins, 12 β-oxidation-related proteins, and 2 metabolisms of acyl-CoA-related proteins were up regulated. These results indicated that during the biodegradation of petroleum hydrocarbons in P. aeruginosa P6, the activity of chemotaxis, the terminal oxidation of short-chain alkanes, and transmembrane transport decreased, while the activity of the uptake of petroleum hydrocarbons, the terminal oxidation of long-chain alkanes, dehydrogenation, β-oxidation, and the metabolism of acyl-CoA increased under the 20,000mg/L petroleum hydrocarbon condition compared with the 500mg/L petroleum hydrocarbon condition. The findings revealed changes in the key proteins and the corresponding cellular process of the biodegradation of petroleum hydrocarbons in P. aeruginosa P6 under high and low concentrations of petroleum hydrocarbons and provided references for future studies.