Assessing risks from fuel contamination in Antarctica: Dynamics of diesel ageing in soil and toxicity to an endemic nematode.

Fuel spills are a major source of contamination in terrestrial environments in Antarctica. Little is known of the effects of hydrocarbon contaminants in fuels on Antarctic terrestrial biota, and how these change as fuel ages within soil. In this study we investigate the sensitivity of juveniles of the endemic Antarctic nematode Plectus murrayi to diesel-spiked soil. Toxicity tests were conducted on soil elutriates, and changes in concentrations of hydrocarbons, polar compounds and PAHs were assessed as the spiked soil was artificially aged at 3 °C over a 45-week period, representing multiple summer seasons of fuel degradation. Nematodes were most sensitive to elutriates made from freshly spiked soils (LC50 419 µg/L TPH and 156 µg/L TPH-SG), with a subsequent decline in toxicity observed in the first 6 weeks of laboratory ageing (LC50 2945 µg/L TPH and 694 µg/L TPH-SG). Effects were still evident up to 45 weeks (lowest observed effect concentration 2123 µg/L TPH) despite hydrocarbons being depleted from soils with ageing (84 % loss) and elutriates becoming dominated by polar metabolites (95 % polar). Nematode sensitivity throughout the ageing period showed evidence of a relationship between LC50 and the proportions of the lighter carbon range fraction of TPH in elutriates, the F2 fraction (C10-14). This study is the first to estimate the sensitivity of Antarctic terrestrial fauna to diesel and provides novel data on the dynamics of fuel chemistry under Antarctic conditions and how this influences toxicity. Findings contribute to predicting ecological risk at existing diesel fuel spill sites in Antarctica, to the derivation of site-specific remediation targets, and to environmental guidelines to assess ecosystem health.

The Role of Catalyst Promotive Additives and Temperature in the Hydroisodewaxing Process.

One of the valuable fractions of paraffinic oils is the diesel fraction, which can be used as a commercial fuel. However, the high content of alkanes of normal structure (~10-40%) in the diesel fraction leads to a deterioration in the performance characteristics of the fuel and, as a result, the inability to use the diesel fraction without additional processing in the cold season at lower temperatures, which is critical for many regions with cold winters. The process of catalytic dewaxing is one of the most promising ways to improve the low-temperature characteristics of diesel fractions. This work is devoted to studying the activity of promoted Ni, Mo, and Ni-Mo catalysts based on mesoporous aluminosilicate and pre-activated bentonite in dewaxing diesel fractions. The effect of the nature and content of promoting additives on the activity of bifunctional catalysts in the process of hydroisodewaxing of diesel fraction in a flow-type reactor in the temperature range of 260-340 °C, pressure of 2 MPa and feed space velocity of 1 h-1 was studied. It is shown that the synthesized bifunctional catalysts based on mesoporous aluminosilicate and pre-activated bentonite from the Tagan field (Ni/MAS-H-bentonite, Mo/MAS-H-bentonite, and Ni-Mo/MAS-H-bentonite) have the necessary balance of Lewis and Bronsted acid centers strengths. It allows them to selectively conduct the hydroisodewaxing process. It has been established that the use of the synthesized 5% Ni-1% Mo/MAS-H-bentonite bifunctional catalyst in the diesel fractions hydroisodewaxing process under optimal process conditions makes it possible to obtain diesel fuel with low-temperature characteristics that meet the requirements for cold climate fuels: cold filter plugging point (CFPP)-minus 33 °C, flash point in a closed cup-39 °C and pour point-minus 36 °C.

A review and evaluation of nonroad diesel mobile machinery emission control in China.

China's emission control for nonroad diesel mobile machinery (NDMM) must deal with a fast increase in stock as well as regulations that are two decades behind those for on-road vehicles. This study provides the first large-scale review and evaluation of China's NDMM policies, along with emission measurements and an investigation on diesel fuel quality. The sulfur contents of the investigated diesel declined from 430 ppm (median value) in 2011 to 6-8 ppm during the 2017-2018 period. The emission control of NOx and PM greatly improved with the shift from the China II to China IV standards, as demonstrated by engine tests and field NOx measurements. However, the NOx emission factors for non-type-approved engines were approximately twice the limits of the China II standards. Emission compliance based on bench tests was not sufficient to control actual emissions because the field-measured NOx emission factors of all machinery ranged from 24% to 225% greater than the respective emission limits for the engines. These circumstances adversely affected the effectiveness of the regulations and policies for China's emission control of NDMM. Nevertheless, the policies on new and in-use NDMM, as well as diesel fuel quality, prevented NOx and PM emissions amounting to 4.4 Tg and 297.8 Gg during the period 2008-2017, respectively. The emission management strategy contributed to enhancing the international competitiveness of China's NDMM industries by promoting advanced technologies. For effective NDMM emission control in the future, portable testing and noncontact remote supervision should be strengthened; also, the issue of noncompliant diesel should be addressed through rigorous control measures and financial penalties.

Adsorption of dibenzothiophene in model diesel fuel by amarula waste biomass as a low-cost adsorbent.

The effectiveness of the adsorption process is determined by the type of adsorbent used, but some adsorbents require a significant amount of processing to achieve the desired quality, and this has become a drawback economically and environmentally. This study focused on mitigating the issue of waste management and land pollution by using amarula waste biomass, which is a low-cost adsorbent that is obtained from the industrial waste by-product. The amarula shell (AmSh) waste was found to have a higher adsorption efficiency of 30 ± 3% compared to the amarula seed (AmSe) waste and the amarula fruit (AmWa) waste, which had 19 ± 5% and 9.5 ± 0.7% efficiency, respectively. It was found that the amarula waste biomass performed better at lower adsorption temperatures. The adsorption capacity was found to decrease with an increase in the quantity of the biomass. Kinetic models were applied to the experimental data. Thermodynamic parameters were also studied to determine the spontaneity of the adsorption process. The characteristics of both the fresh and used amarula waste biomass was analyzed by using Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy with Energy Dispersive Spectroscopy (FESEM-EDS), Brunauer-Emmett-Teller (BET) and Thermogravimetric Analysis (TGA). It was then concluded that cellulose and hemicellulose structures in amarula waste biomass played a major role in reducing the content of dibenzothiophene in model diesel fuel.

Diesel fuel differentially affects hyphal healing in Gigaspora sp. and Rhizophagus irregularis.

Hydrocarbon pollution is an increasing problem affecting soil ecosystems. However, some microorganisms can cope with these pollutants and even facilitate plant establishment and thus phytoremediation. Within soil, arbuscular mycorrhizal fungi (AMF) have developed several strategies to survive and flourish under adverse conditions. Among these is the hyphal healing mechanism (HHM), a process allowing hyphae to re-establish integrity after physical injury. This mechanism differs among species and genera of AMF. However, whether and to what extent hydrocarbon pollution impacts the HHM is unknown. Here, the HHM was monitored in vitro on two AMF strains, Rhizophagus irregularis MUCL 41833 and Gigaspora sp. MUCL 52331, under increasing concentrations of diesel (1, 2, and 5% v:v). The addition of diesel slowed-down the HHM in both fungi. On Gigaspora sp., this effect was limited and most hyphae were able to heal after injury. Conversely, all steps of healing were severely impaired in R. irregularis. That fungus reconnected the injured hyphae at a much lower frequency than the Gigaspora sp., instead investing its energy to link neighboring hyphae or roots, or developing new branches from uninjured hyphae.

Multispecies Diesel Fuel Biodegradation and Niche Formation Are Ignited by Pioneer Hydrocarbon-Utilizing Proteobacteria in a Soil Bacterial Consortium.

A soil bacterial consortium that was grown on diesel fuel and consisted of more than 10 members from different genera was maintained through repetitive subculturing and was utilized as a practical model to investigate a bacterial community that was continuously exposed to petroleum hydrocarbons. Through metagenomics analyses, consortium member isolation, growth assays, and metabolite identification which supported the linkage of genomic data and functionality, two pioneering genera, Sphingobium and Pseudomonas, whose catabolic capabilities were differentiated, were found to be responsible for the creation of specialized ecological niches that were apparently occupied by other bacterial members for survival within the consortium. Coexisting genera Achromobacter and Cupriavidus maintained their existence in the consortium through metabolic dependencies by utilizing hydrocarbon biotransformation products of pioneer metabolism, which was confirmed through growth tests and identification of biotransformation products of the isolated strains. Pioneering Sphingobium and Pseudomonas spp. utilized relatively water-insoluble hydrocarbon parent compounds and facilitated the development of a consortium community structure that resulted in the creation of niches in response to diesel fuel exposure which were created through the production of more-water-soluble biotransformation products available to cocolonizers. That these and other organisms were still present in the consortium after multiple transfers spanning 15 years provided evidence for these ecological niches. Member survival through occupation of these niches led to robustness of each group within the multispecies bacterial community. Overall, these results contribute to our understanding of the complex ecological relationships that may evolve during prokaryotic hydrocarbon pollutant biodegradation.IMPORTANCE There are few metagenome studies that have explored soil consortia maintained on a complex hydrocarbon substrate after the community interrelationships were formed. A soil bacterial consortium maintained on diesel fuel was utilized as a practical model to investigate bacterial community relationships through metagenomics analyses, consortium member isolation, growth assays, and metabolite identification, which supported the linkage of genomic data and functionality. Two pioneering genera were responsible for the biodegradation of aromatics and alkanes by initiating biotransformation and thereby created specialized niches that were populated by other members. A model that represents these relationships was constructed, which contributes to our understanding of the complex ecological relationships that evolve during prokaryotic hydrocarbon pollutant biodegradation.

Influence of diesel fuel contamination on Xanthium strumarium L. germination and growth.

In this study, the effects of diesel fuel contamination on common cocklebur (Xanthium strumarium L.) seeds have been investigated. Five levels of contamination were used (0 g, 2.5 g, 5 g, 7.5 g, and 10 g diesel per 100 g of substrate). Germination was significantly reduced only at 7.5 g and 10 g diesel and the highest percentage germination (97%) was recorded at 5 g diesel. Diesel contamination caused a significant reduction in shoot length, but the decline began to be important at 7.5 g diesel. The root length was positively influenced by diesel fuel contamination, the shortest root (12.89 cm) was observed in the control and the longest (19.92 cm) at 5 g diesel. Xanthium strumarium seeds germinated successfully at different levels of contamination, its root length seemed to take advantage of the diesel fuel contamination and its shoot length was mostly affected by the high contamination levels. Therefore, we can propose this plant species as a potential candidate for the phytoremediation of sites contaminated with diesel. Furthermore, the results could help improve our understanding of the behavior of X. strumarium, and its ability to germinate and grow in different soil conditions.

Laser-Driven Calorimetry and Chemometric Quantification of Standard Reference Material Diesel/Biodiesel Fuel Blends.

Requirements for blends of drop-in petroleum/bio-derived fuels with specific thermophysical and thermochemical properties highlights the need for chemometric models that can predict these properties. Multivariate calibration methods were evaluated using the measured thermograms (i.e., change in temperature with time) of 11 diesel/biodiesel fuel blends (including four repeated runs for each fuel blend). Two National Institute of Standards and Technology Standard Reference Material® (SRM®) pure fuels were blended by serial dilution to produce fuels having diesel/biodiesel volumetric fractions between (0 to 100) %. The fuels were evaluated for the prepared fuel-blend volume fraction and total specific energy release (heating value), using a laser-driven calorimetry technique, termed 'laser-driven thermal reactor'. The experimental apparatus consists of a copper sphere-shaped reactor (mounted at the center of a stainless-steel chamber) that is heated by a high-power continuous wave Nd:YAG laser. Prior to heating by the laser, liquid sample is injected onto a copper pan substrate that rests near the center of the reactor and is in contact with a fine-wire thermocouple. A second thermocouple is in contact with the sphere-reactor inner surface. The thermograms are then used to evaluate for the thermochemical characteristic of interest. Partial least squares (PLS) and support vector machine (SVM) models were constructed and evaluated for SRM-fuel-blend quantification, and determination of prepared fuel-blend volume fraction and heating value. Quantification of the fuel-blend thermograms by the SVM method was found to better correlate with the experimental results than PLS. The combination of laser-driven calorimetry and multivariate calibration methods has demonstrated the potential application of using thermograms for fuels quantification and analysis of fuel-blend properties.

Crystal structure of F95Q epi-isozizaene synthase, an engineered sesquiterpene cyclase that generates biofuel precursors ß- and γ-curcumene.

The saturated hydrocarbon bisabolane is a diesel fuel substitute that can be derived from sesquiterpene precursors bisabolene or curcumene. These sesquiterpenes are generated from farnesyl diphosphate in reactions catalyzed by eponymous terpenoid cyclases, but they can also be generated by engineered terpenoid cyclases in which cyclization cascades have been reprogrammed by mutagenesis. Here, we describe the X-ray crystal structure determination of F95Q epi-isozizaene synthase (EIZS), in which the new activity of curcumene biosynthesis has been introduced and the native activity of epi-isozizaene biosynthesis has been suppressed. F95Q EIZS generates ß- and γ-curcumene regioisomers with greater than 50% yield. Structural analysis of the closed active site conformation, stabilized by the binding of 3 Mg2+ ions, inorganic pyrophosphate, and the benzyltriethylammonium cation, reveals a product-like active site contour that serves as the cyclization template. Remolding the active site contour to resemble curcumene instead of epi-isozizaene is the principal determinant of the reprogrammed cyclization cascade. Intriguingly, an ordered water molecule comprises part of the active site contour. This water molecule may also serve as a final proton acceptor, along with inorganic pyrophosphate, in the generation of curcumene regioisomers; it may also contribute to the formation of sesquiterpene alcohols identified as minor side products. Thus, the substitution of polar side chains for nonpolar side chains in terpenoid cyclase active sites can result in the stabilization of bound water molecules that, in turn, can serve template functions in isoprenoid cyclization reactions.

Advances in chemometric control of commercial diesel adulteration by kerosene using IR spectroscopy.

Adulteration is a recurrent issue found in fuel screening. Commercial diesel contamination by kerosene is highly difficult to be detected via physicochemical methods applied in market. Although the contamination may affect diesel quality and storage stability, there is a lack of efficient methodologies for this evaluation. This paper assessed the use of IR spectroscopies (MIR and NIR) coupled with partial least squares (PLS) regression, support vector machine regression (SVR), and multivariate curve resolution with alternating least squares (MCR-ALS) calibration models for quantifying and identifying the presence of kerosene adulterant in commercial diesel. Moreover, principal component analysis (PCA), successive projections algorithm (SPA), and genetic algorithm (GA) tools coupled to linear discriminant analysis were used to observe the degradation behavior of 60 samples of pure and kerosene-added diesel fuel in different concentrations over 60 days of storage. Physicochemical properties of commercial diesel with 15% kerosene remained within conformity with Brazilian screening specifications; in addition, specified tests were not able to identify changes in the blends' performance over time. By using multivariate classification, the samples of pure and contaminated fuel were accurately classified by aging level into two well-defined groups, and some spectral features related to fuel degradation products were detected. PLS and SVR were accurate to quantify kerosene in the 2.5-40% (v/v) range, reaching RMSEC < 2.59% and RMSEP < 5.56%, with high correlation between real and predicted concentrations. MCR-ALS with correlation constraint was able to identify and recover the spectral profile of commercial diesel and kerosene adulterant from the IR spectra of contaminated blends.

Capillary Sensor with Disposable Optrode for Diesel Fuel Quality Testing.

Diesel fuel quality can be considered from many different points of view. Fuel producers, fuel consumers, and ecologists have their own ideas. In this paper, a sensor of diesel fuel quality type, and fuel condition that is oriented to the fuel's consumers, is presented. The fuel quality types include premium, standard, and full bio-diesel classes. The fuel conditions include fuel fit for use and fuel degraded classes. The classes of fuel are connected with characteristics of engine operation. The presented sensor uses signal processing of an optoelectronic device monitoring fuel samples that are locally heated to the first step of boiling. Compared to previous works which consider diesel fuel quality sensing with disposable optrodes which use a more complex construction, the sensor now consists only of a capillary probe and advanced signal processing. The signal processing addresses automatic conversion of the data series to form a data pattern, estimates the measurement uncertainty, eliminates outlier data, and determines the fuel quality with an intelligent artificial neural network classifier. The sensor allows the quality classification of different unknown diesel fuel samples in less than a few minutes with the measurement costs of a single disposable capillary probe and two plugs.

Mitigation of soil contaminated with diesel fuel using bioelectrokinetics.

This study investigated the effectiveness of bioelectrokinetics in rehabilitating a silty clayey sand contaminated with diesel fuel using three novel bacterial strains; Acinetobacter calcoaceticus, Sphingobacterium multivorum, and Sinorhizobium, isolated form agriculture land. Three electrokinetic bioremediation cells were used to conduct the tests and a novel electrode configuration technique was used to stabilize pH and water content in the soil specimen. Solar photovoltaic panels were used to generate sustainable energy for the process. The tests were carried out in outdoors for 55 days. Applied voltage, current passing through the electrokinetic cell, and the temperature of the soil specimen were recorded periodically during the test. The pH, water content, and diesel concentration were determined at the end of the tests. Over the test period, the voltage typically increased from zero before sunrise, remained relatively stabilized for about 4 h, and then started to decrease and dropped to zero by sunset. The temperatures in the cells were found to be 5-7 °C higher than the ambient temperature. The innovative electrode configuration succeeded in keeping the pH of soil to remain the same and thereby prevented the development of a pH gradient in the soil, an important development for survival of the bacteria. The diesel degradation in the soil after bioelectrokinetics were 20-30%, compared to 10-12% in the control test. The study was successful in developing environmentally friendly technology employing novel bacterial strains to degrade diesel fuel and utilizing solar panel to produce renewable energy for bioelectrokinetic during the winter season.

Evaluation of conventional and response surface level optimisation of n-dodecane (n-C12) mineralisation by psychrotolerant strains isolated from pristine soil at Southern Victoria Island, Antarctica.

BACKGROUND: Biodegradation of hydrocarbons in Antarctic soil has been reported to be achieved through the utilisation of indigenous cold-adapted microorganisms. Although numerous bacteria isolated from hydrocarbon-contaminated sites in Antarctica were able to demonstrate promising outcomes in utilising hydrocarbon components as their energy source, reports on the utilisation of hydrocarbons by strains isolated from pristine Antarctic soil are scarce. In the present work, two psychrotolerant strains isolated from Antarctic pristine soil with the competency to utilise diesel fuel as the sole carbon source were identified and optimised through conventional and response surface method. RESULTS: Two potent hydrocarbon-degraders (ADL15 and ADL36) were identified via partial 16S rRNA gene sequence analysis, and revealed to be closely related to the genus Pseudomonas and Rhodococcus sp., respectively. Factors affecting diesel degradation such as temperature, hydrocarbon concentration, pH and salt tolerance were studied. Although strain ADL36 was able to withstand a higher concentration of diesel than strain ADL15, both strains showed similar optimal condition for the cell's growth at pH 7.0 and 1.0% (w/v) NaCl at the conventional 'one-factor-at-a-time' level. Both strains were observed to be psychrotrophs with optimal temperatures of 20 °C. Qualitative and quantitative analysis were performed with a gas chromatograph equipped with a flame ionisation detector to measure the reduction of n-alkane components in diesel. In the pre-screening medium, strain ADL36 showed 83.75% of n-dodecane mineralisation while the reduction of n-dodecane by strain ADL15 was merely at 22.39%. The optimised condition for n-dodecane mineralisation predicted through response surface methodology enhanced the reduction of n-dodecane to 99.89 and 38.32% for strain ADL36 and strain ADL15, respectively. CONCLUSIONS: Strain ADL36 proves to be a better candidate for bioaugmentation operations on sites contaminated with aliphatic hydrocarbons especially in the Antarctic and other cold regions. The results obtained throughout strongly supports the use of RSM for medium optimisation.

Estimating diesel fuel exposure for a plumber repairing an underground pipe.

We estimated the diesel fuel exposure of a plumber repairing an underground water line leak at a truck stop. The repair work was performed over three days during which the plumber spent most of his time in a pit filled with a mixture of water and diesel fuel. Thus, the plumber was exposed via both the inhalation and dermal routes. While previously asymptomatic, he was diagnosed with acute renal failure 35 days after working at this site. No measurements were available for estimating either inhalation or dermal exposures or the cumulative dose and, therefore, two different approaches were used that were based on simple models of the exposure scenario. The first approach used the ideal gas law with the vapor pressure of the diesel fuel mixture to estimate a saturation vapor concentration, while the second one used a mass balance of the petroleum hydrocarbon component of diesel fuel in conjunction with the Henry's Law constant for this mixture. These inhalation exposure estimates were then adjusted to account for the limited ventilation in a confined space. The inhalation exposure concentrations predicted when handling the water layer alone is much lower than that expected from the organic layer. This case study illustrates the large differences in inhalation exposure associated with volatile organic layers and aqueous solution containing these chemicals. The estimate of dermal exposure was negligible compared to the inhalation exposure because the skin presents a much smaller surface area of exposure to the contaminant compared to the lungs. The methodology presented here is useful for situations where little information is available for more formal mathematical exposure modeling, but where adjustments to the worst-case exposures, estimated simply, can provide reasonable exposure estimates.

Oyster's cells regulatory volume decrease: A new tool for evaluating the toxicity of low concentration hydrocarbons in marine waters.

Human activities require fossil fuels for transport and energy, a substantial part of which can accidentally or voluntarily (oil spillage) flow to the marine environment and cause adverse effects in human and ecosystems' health. This experiment was designed to estimate the suitability of an original cellular biomarker to early quantify the biological risk associated to hydrocarbons pollutants in seawater. Oocytes and hepatopancreas cells, isolated from oyster (Crassostrea gigas), were tested for their capacity to regulate their volume following a hypo-osmotic challenge. Cell volumes were estimated from cell images recorded at regular time intervals during a 90min-period. When exposed to diluted seawater (osmolalities from 895 to 712mosmkg(-1)), both cell types first swell and then undergo a shrinkage known as Regulatory Volume Decrease (RVD). This process is inversely proportional to the magnitude of the osmotic shock and is best fitted using a first-order exponential decay model. The Recovered Volume Factor (RVF) calculated from this model appears to be an accurate tool to compare cells responses. As shown by an about 50% decrease in RVF, the RVD process was significantly inhibited in cells sampled from oysters previously exposed to a low concentration of diesel oil (8.4mgL(-1) during 24h). This toxic effect was interpreted as a decreased permeability of the cell membranes resulting from an alteration of their lipidic structure by diesel oil compounds. In contrast, the previous contact of oysters with diesel did not induce any rise in the gills glutathione S-transferase specific activity. Therefore, this work demonstrates that the study of the RVD process of cells selected from sentinel animal species could be an alternative bioassay for the monitoring of hydrocarbons and probably, of various chemicals in the environment liable to alter the cellular regulations. Especially, given the high sensitivity of this biomarker compared with a proven one, it could become a relevant and accurate tool to estimate the biological hazards of micropollutants in the water.

Lab-scale investigation on remediation of diesel-contaminated aquifer using microwave energy.

Aquifer contamination with diesel fuel is a worldwide environmental problem, and related available remediation technologies may not be adequately efficient, especially for the simultaneous treatment of both solid and water phases. In this paper, a lab-scale 2.45 GHz microwave (MW) treatment of an artificially diesel-contaminated aquifer was applied to investigate the effects of operating power (160, 350 and 500 W) and time on temperature profiles and contaminant removal from both solid and water phases. Results suggest that in diesel-contaminated aquifer MW remediation, power significantly influences the final reachable temperature and, consequently, contaminant removal kinetics. A maximum temperature of about 120 °C was reached at 500 W. Observed temperature values depended on the simultaneous irradiation of both aquifer grains and groundwater. In this case, solid phase heating is limited by the maximum temperature that interstitial water can reach before evaporation. A minimal residual diesel concentration of about 100 mg kg(-1) or 100 mg L(-1) was achieved by applying a power of 500 W for a time of 60 min for the solid or water phase, respectively. Measured residual TPH fractions showed that MW heating resulted in preferential effects of the removal of different TPH molecular weight fractions and that the evaporation-stripping phenomena plays a major role in final contaminant removal processes. The power low kinetic equation shows an excellent fit (r(2) > 0.993) with the solid phase residual concentration observed for all the powers investigated. A maximum diesel removal of 88 or 80% was observed for the MW treatment of the solid or water phase, respectively, highlighting the possibility to successfully and simultaneously remediate both the aquifer phases. Consequently, MW, compared to other biological or chemical-physical treatments, appears to be a better choice for the fast remediation of diesel-contaminated aquifers.

Quantification of nitrogen compounds in diesel fuel samples by comprehensive two-dimensional gas chromatography coupled with quadrupole mass spectrometry.

Although several methods for the analysis of nitrogen compounds in diesel fuel have been described in the literature, the demand for rapid, sensitive, and robust analyses has increased in recent years. In this study, a comprehensive two-dimensional gas chromatographic method was developed for the identification and quantification of nitrogen compounds in diesel fuel samples. The quantification was performed using the standard addition method and the analysis was conducted using comprehensive two-dimensional gas chromatography coupled with fast quadrupole mass spectrometry. This study is the first to report quantification of nitrogen compounds in diesel fuel samples using the standard addition method without fractionation. This type of analysis was previously performed using many laborious separation steps, which can lead to errors and losses. The proposed method shows good linearity for target nitrogen compounds evaluated (m-toluidine, 4-ethylaniline, indole, 7-methylindole, 7-ethylindole, carbazole, isoquinoline, 4-methylquinoline, benzo[h]quinolone, and acridine) over a range from 0.05 to 2.0 mg/L, and limits of detection and quantification of <0.06 and 0.16 mg/L, respectively, for all nitrogen compounds studied.

Characterization of the noncancer hazards of gas oils.

Gas oils, used to manufacture diesel fuel and residential heating oil, are complex hydrocarbon substances with carbon numbers of C9-C30 and boiling ranges of approximately 150 °C to 450 °C. Target organ (liver enlargement, reduced thymus weights, and reductions in hematological parameters) and developmental (reduced fetal viability, increased resorption frequency, and reduced fetal weights) effects are associated with aromatic constituents present in some gas oils. Two types of gas oils were tested for repeated-dose and developmental toxicity following repeated dermal administration. A blend of commercial diesel fuels containing 26% aromatics, primarily single-ring compounds, did not cause either target organ or developmental effects at levels up to 600 mg/kg/d. "Cracked" gas oils containing higher levels of aromatic constituents were also tested. Because of limited sample availability, 2 cracked gas oil samples were tested, one for systemic effects and the other for developmental toxicity. The sample tested in the repeated-dose toxicity study (81% aromatics including approximately 10% 3-ring compounds) produced increased liver weights, reduced thymus weights, and reductions in hematological parameters. The overall no observed adverse effect level (NOAEL) was 100 mg/kg/d. The sample tested for developmental toxicity (65% aromatics including approximately 5% 3-ring compounds) resulted in significant reductions in fetal survival, significant increases in resorption frequency, and significant reductions in fetal weights with an overall NOAEL of 100 mg/kg/d. In summary, gas oils may or may not cause target organ and/or developmental effects depending on the levels and types of aromatic constituents that they contain.

Assessment of diesel fuel quality.

Diesel is an essential energy source in the transportation and industrial sectors worldwide; hence, the quality of this commodity is crucial. This study compares various fuel samples to understand the quality of the fuels in terms of sulphur content, density, surface tension, viscosity, and calorific value. The properties of diesel fuel samples from eight (8) Filling Stations (Marketing Companies (MC)) were examined and compared with GSA 141:2022 and ISO 8217:2017 standards. Fuel from two companies, MC-A and MC-G had slightly lower densities than the standard, indicative of a possible contamination with lower-density fuels such as kerosene. The surface tension of all samples, except one was within the standard range. The only sample with the lower than the standard value also displayed high sulphur content. Although all the fuel samples met the minimum requirement for calorific value, the viscosities of the fuels from three companies were slightly higher than the specified standard value which can potentially result in higher emissions. In the case of sulphur content, fuel samples from only three companies were in compliance with the maximum 50 ppm standard. This means 62.5 % of the diesel fuel within the study area at the time contained more than the acceptable amount of sulphur. The findings in this research highlight the need to re-examine the quality of fuels along the distribution chain.

Radon deficit technique applied to the study of the ageing of a spilled LNAPL in a shallow aquifer.

A recent diesel spill (dated January 2019 ± 1 month) in a refilling station is investigated by the Radon deficit technique. The primary focus was on quantifying the LNAPL pore saturation as a function of duration of ageing, and on proposing a predictive model for on-site natural attenuation. A biennial monitoring of the local fluctuating shallow aquifer has involved the saturated zone nine times, and the vadose zone only once. Rn background generally measured in external and upstream wells is elaborated further due to the site characteristics, using drilling logs and phreatic oscillations. Notably, this study marks the first application of the Rn deficit method to produce a detailed Rn background mapping throughout the soil depth. Simultaneously, tests are performed on LNAPL surnatant samples to study diesel ageing. In particular, they are focused on temporal variations of LNAPL viscosity (from an initial 3.90 cP to 8.99 cP, measured at 25 °C, after 34 months), and Rn partition coefficient between the pollutant and water (from 47.7 to 80.2, measured at 25 °C, after 14 months). Rn diffusion is also measured in different fluids (0.092 cm2 s-1, 1.14 × 10-5 cm2 s-1, and 2.53 × 10-6 cm2 s-1 at 25 °C for air, water and LNAPL, respectively) directly. All parameters and equations utilized during this study are introduced, discussing their influence on Radon deficit technique from a theoretical point of view. Experimental findings are used to mitigate the effect of LNAPL ageing and of phreatic oscillations on determination of LNAPL saturation index (S.I.LNAPL). Finally, S.I.LNAPL dataset is discussed and elaborated to show the pollutant attenuation across subsurface over time, induced by natural processes primarily. The proposed predictive model for on-site natural attenuation suggests a half-removal time of one year and six months. The significance of such models lies in their capability to assess site-specific reactions to pollutants, thereby enhancing the effectiveness of remediation efforts over time. These experimental findings may offer a novel approach to application of Rn deficit technique and to environmental remediation of persistent organic compounds.