Abstract  Biodegradability was conducted according to OECD guideline n°301B. Sample biodegradability was equal to 55.9% after 28 days and 66.3% after 36 days.

Abstract  Among several bacterial species belonging to the general Gordonia, Mycobacterium, Micromonospora, Pseudomonas, and Rhodococcus, only two mycobacterial isolates, Mycobacterium fortuitum strain NF4 and the new isolate Mycobacterium ratisbonense strain SD4, which was isolated from a sewage treatment plant, were capable of utilizing the multiply branched hydrocarbon squalane (2,6,10,15,19, 23-hexamethyltetracosane) and its analogous unsaturated hydrocarbon squalene as the sole carbon source for growth. Detailed degradation studies and high-pressure liquid chromatography analysis showed a clear decrease of the concentrations of squalane and squalene during biomass increase. These results were supported by resting-cell experiments using strain SD4 and squalane or squalene as the substrate. The degradation of acyclic isoprenoids and alkanes as well as of acids derived from these compounds was also investigated. Inhibition of squalane and squalene degradation by acrylic acid indicated the possible involvement of beta-oxidation in the degradation route. To our knowledge, this is the first report demonstrating the biodegradation of squalane by using defined axenic cultures.

Abstract  Production of biosurfactants by acidophilic mycobacteria was demonstrated in the course of aerobic degradation of hydrocarbons (n-tridecane, n-tricosane, n-hexacosane, model mixtures of D-14-D-17, D(12)aEuro'D-19, and D-9-D-21 n-alkanes, 2,2,4,4,6,8,8-heptamethylnonane, squalane, and butylcyclohexane) and their complex mixtures (hydrocarbon gas condensate, kerosene, black oil, and paraffin oil) under extremely acidic conditions (pH 2.5). When grown on hydrocarbons, the studied bacterial culture AG(S10) caused a decrease in the surface and interfacial tension of the solutions (to the lowest observed values of 26.0 and 1.3 mN/m, respectively) compared to the bacteria-free control. The rheological characteristics of the culture changed only when mycobacteria were grown on hydrocarbons. Neither the medium nor the cell-free culture liquid had the surfactant activity, which indicated formation of an endotype biosurfactant by mycobacteria. Biodegradation of n-alkanes was accompanied by an increase in cell numbers, surfactant production, and changes in the hydrophobicity of bacterial cell surface and in associated phenomena of adsorption and desorption to the hydrocarbon phase. Research on AGS10 culture liquids containing the raw biosurfactant demonstrated the preservation of its activity within a broad range of pH, temperature, and salinity.

Abstract  Here we report a new method for measuring the heterogeneous chemistry of sub-micron organic aerosol particles using a continuous flow stirred tank reactor. This approach is designed to quantify the real time heterogeneous kinetics, using a relative rate method, under conditions of low oxidant concentration and long reaction times that more closely mimic the real atmosphere than the conditions used in a typical flow tube reactor. A general analytical expression, which couples the aerosol chemistry with the flow dynamics in the chamber is developed and applied to the heterogeneous oxidation of squalane particles by hydroxyl radicals (OH) in the presence of O(2). The particle phase reaction is monitored via photoionization aerosol mass spectrometry and yields a reactive uptake coefficient of 0.51 +/- 0.10, using OH concentrations of 1-7 x 10(8) molecule cm(-3) and reaction times of 1.5-3 h. In general, this approach provides a new way to connect the chemical aging of organic particles measured at short reaction times and high oxidant concentrations in flow tubes with the long reaction times and low oxidant conditions in smog chambers and the real atmosphere.

Abstract  The particle/gas partition coefficient Kp is an important parameter affecting the fate and transport of indoor semivolatile organic compounds (SVOCs) and resulting human exposure. Unfortunately, experimental measurements of Kp exist almost exclusively for atmospheric polycyclic aromatic hydrocarbons, with very few studies focusing on SVOCs that occur in indoor environments. A specially designed tube chamber operating in the laminar flow regime was developed to measure Kp of the plasticizer di-2-ethylhexyl phthalate (DEHP) for one inorganic (ammonium sulfate) and two organic (oleic acid and squalane) particles. The values of Kp for the organic particles (0.23 ± 0.13 m3/μg for oleic acid and 0.11 ± 0.10 m3/μg for squalane) are an order of magnitude higher than those for the inorganic particles (0.011 ± 0.004 m3/μg), suggesting that the process by which the particles accumulate SVOCs is different. A mechanistic model based on the experimental design reveals that the presence of the particles increases the gas-phase concentration gradient in the boundary layer, resulting in enhanced mass transfer from the emission source into the air. This novel approach provides new insight into experimental designs for rapid Kp measurement and a sound basis for investigating particle-mediated mass transfer of SVOCs.

Abstract  The adsorption coefficient of Squalane (CAS 111-01-3) has been determined to be greater than 4.27 x 105, log10 Koc greater than 5.63, using the HPLC screening method, designed to be compatible with Method C19 Adsorption Coefficient of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 121 of the OECD Guidelines for Testing of Chemicals, 22 January 2001.

Abstract  The ready biodegradation of the squalane was determined by the carbon dioxide evolution test method (OCDE guideline 301B). Tests of ready biodegradability are stringent tests that provide limited oppotunity for acclimation and biodegradation to occur. In the CO2 test, inoculated mineral medium was dosed with a known amount of test substance as the nominal sole source of organic carbon and aerated with CO2 -free air. The CO2 produced from the mineralization of organic carbon within the test chambers was displaced by the ow of CO2 -free air and trapped as K2CO3 in KOH trapping solution. The amount of CO2 produced by the test substance is expressed as a percentage of the theoretical amount of CO2 that could have been produced if complete biodegradation of the substance occurred. The test contained a blank control, three reference groups and one treatment group. Each group contained two replicate test chambers. The blank control was used to measure the background CO2 production of the inoculum and was dosed with a carbon source. The reference chambers were dosed with either canola oil, Synuid or Ultra Low Sulfur Diesel at a concentration of 10 mg C/L. The treatment group test chambers were used to evaluate the test substance at concentration of approximately 10 mg C/L. The results indicated that the activated sludge inoculum was active, degrading the canola oil reference 99.9%. The average cumulative percent biodegradation for squalane was 64.7%. However, squalane may be considered inherently biodegradable because it reached 60% of TCO2, though not within a 10 -days window of reaching 10% TCO2.

Abstract  Absorption, distribution, and release of squalane were studied in rainbow trout fed a diet containing 0.05% of this alkane. Estimated squalane absorption was about 40% of the dose. After three months of exposure, the residues in the whole body reached a steady equilibrium value of about 16- 18 micrograms/g. The most pronounced deposition occurred in the liver (1671 micrograms/g after 10 months), while the concentration of squalane in the adipose tissue was below 2 micrograms/g. During the depuration period, half of the contaminated trout were fed a squalane-free diet, while the others were starved. After two months, the body burden amounted to 65% and 80% of the alkane previously accumulated in starved and fed trout, respectively. In the starved group, 43% of the squalane initially stored in the liver was lost, whereas the loss in the fed fish liver was 52%. These results were compared with existing data on other alkanes. (Author 's abstract)

Abstract  The heterogeneous reaction of OH radicals with sub-micron squalane particles, in the presence of O-2, is used as a model system to explore the fundamental chemical mechanisms that control the oxidative aging of organic aerosols in the atmosphere. Detailed kinetic measurements combined with elemental mass spectrometric analysis reveal that the reaction proceeds sequentially by adding an average of one oxygenated functional group per reactive loss of squalane. The reactive uptake coefficient of OH with squalane particles is determined to be 0.3 +/- 0.07 at an average OH concentration of similar to 1 x 10(10) molecules cm(-3). Based on a comparison between the measured particle mass and model predictions it appears that significant volatilization of a reduced organic particle would be extremely slow in the real atmosphere. However, as the aerosols become more oxygenated, volatilization becomes a significant loss channel for organic material in the particle-phase. Together these results provide a chemical framework in which to understand how heterogeneous chemistry transforms the physiochemical properties of particle-phase organic matter in the troposphere.

Abstract  The reactive uptake coefficients γ, for nitrate radical, NO(3), on ∼100 nm diameter squalane and squalene aerosol were measured (1 atm pressure of N(2) and 293 K). For squalane, a branched alkane, γ(NO(3)) of 2.8 × 10(-3) was estimated. For squalene which contains 6 double bonds, γ(NO(3)) was found to be a function of degree of oxidation with an initial value of 0.18 ± 0.03 on fresh particles increasing to 0.82 ± 0.11 on average of over 3 NO(3) reactions per squalene molecule in the aerosol. Synchrotron VUV-ionization aerosol mass spectrometry was used to detect the particle phase oxidation products that include as many as 3 NO(3) subunits added to the squalene backbone. The fraction of squalene remaining in the aerosol follows first order kinetics under oxidation, even at very high oxidation equivalents, which suggests that the matrix remains a liquid upon oxidation. Our calculation indicates a much shorter chemical lifetime for squalene-like particle with respect to NO(3) than its atmospheric lifetime to deposition or wet removal.

Abstract  This study was conducted to better understand the processes of carbonaceous deposits formation in the piston grooves of direct injection Diesel engines. An experimental investigation of parameters affecting the engine oil degradation in the first groove of a Diesel engine was carried out to shed light on the formation of these carbonaceous deposits. A dedicated reactor was designed to reproduce the parameters that exist in the first groove of a Diesel engine used under exhaust gas recirculation conditions, and squalane was used to model the lubricant. The relationship between oil degradation and environmental conditions (temperature, pressure, time, oxygen content and components of the gas in the groove) was clarified by characterizing the degradation levels of the squalane molecule. A general mechanism was proposed to explain the formation of carbon deposits in the first piston grooves of Diesel engines depending on the surrounding atmosphere. The influence of pressure on degradation conditions usually investigated under atmospheric conditions was proposed for the first time to understand processes responsible for carbonaceous deposit formation.

Abstract  The reaction of Cl atoms, in the presence of Cl(2) and O(2), with sub-micron squalane particles is used as a model system to explore how surface hydrogen abstraction reactions initiate chain reactions that rapidly transform the chemical composition of an organic particle. The heterogeneous reaction is measured in a photochemical flow tube reactor in which chlorine atoms are produced by the photolysis of Cl(2) at 365 nm. By monitoring the heterogeneous reaction, using a vacuum ultraviolet photoionization aerosol mass spectrometer, the effective reactive uptake coefficient and the distributions of both oxygenated and chlorinated reaction products are measured and found to depend sensitively upon O(2), Cl(2), and Cl concentrations in the flow reactor. In the absence of O(2), the effective reactive uptake coefficient monotonically increases with Cl(2) concentration to a value of ∼3, clearly indicating the presence of secondary chain chemistry occurring in the condensed phase. The effective uptake coefficient decreases with increasing O(2) approaching a diffusion corrected value of 0.65 ± 0.07, when 20% of the total nitrogen flow rate in the reactor is replaced with O(2). Using a kinetic model it is found that the amount of secondary chemistry and the product distributions in the aerosol phase are controlled by the competitive reaction rates of O(2) and Cl(2) with alkyl radicals. The role that a heterogeneous pathway might play in the reaction of alkyl radicals with O(2) and Cl(2) is investigated within a reasonable range of reaction parameters. These results show, more generally, that for heterogeneous reactions involving secondary chain chemistry, time and radical concentration are not interchangeable kinetic quantities, but rather the observed reaction rate and product formation chemistry depends sensitively upon the concentrations and time evolution of radical initiators and those species that propagate or terminate free radical chain reactions.

Abstract  Biological oil hydrocarbons degradation is a complicated process, influenced by hydrocarbons properties, microorganisms and environmental conditions. The aim of this work was to select microbial strain, capable of degrading heavy branched hydrocarbons for further application in environment remediation and bio-cracking. Also, it was necessary to select optimal conditions (temperature, pH, concentration and etc.) for selected microbial strain degrading heavy branched hydrocarbons. Since crude oil and its products are mixtures of various hydrocarbons, at the first step of selection the ability of the strains to degrade individual hydrocarbons was investigated. Squalane was used as a test substrate. 10 microbial cultures belonging to genus Arthrobacter and obtained from culture collection of JSC "Biocentras" were used for the investigations. Gas chromatography analysis revealed that Arthrobacter sp NJ5 strain had the highest effectiveness (67%) in degradation of heavy branched oil hydrocarbon (Squalane) to shorter chain intermediates. So, Arthrobacter sp NJ5 could be applied in bio-cracking. For the application in industry, more detailed analyses are needed.

Abstract  Insights into the influence of molecular structure and thermodynamic phase on the chemical mechanisms of hydroxyl radical-initiated heterogeneous oxidation are obtained by identifying reaction products of submicrometer particles composed of either n-octacosane (C28H58, a linear alkane) or squalane (C30H62, a highly branched alkane) and OH. A common pattern is observed in the positional isomers of octacosanone and octacosanol, with functionalization enhanced toward the end of the molecule. This suggests that relatively large linear alkanes are structured in submicrometer particles such that their ends are oriented toward the surface. For squalane, positional isomers of first-generation ketones and alcohols also form in distinct patterns. Ketones are favored on carbons adjacent to tertiary carbons, while hydroxyl groups are primarily found on tertiary carbons but also tend to form toward the end of the molecule. Some first-generation products, viz., hydroxycarbonyls and diols, contain two oxygen atoms. These results suggest that alkoxy radicals are important intermediates and undergo both intramolecular and intermolecular (chain propagation) hydrogen abstraction reactions. Oxidation products with carbon number less than the parent alkane's are observed to a much greater extent for squalane than for n-octacosane oxidation and can be explained by the preferential cleavage of bonds involving tertiary carbons.

Abstract  Recent work has established that secondary organic aerosol (SOA) can exist as an amorphous solid, leading to various suggestions that the addition of SOA coatings to existing particles will decrease the reactivity of those particles toward common atmospheric oxidants. Experimental evidence suggests that O3 is unable to physically diffuse through an exterior semisolid or solid layer thus inhibiting reaction with the core. The extent to which this suppression in reactivity occurs for OH has not been established, nor has this been demonstrated specifically for SOA. Here, measurements of the influence of adding a coating of α-pinene+O3 SOA onto squalane particles on the OH-initiated heterogeneous oxidation rate are reported. The chemical composition of the oxidized internally mixed particles was monitored online using a vacuum ultraviolet-aerosol mass spectrometer. Variations in the squalane oxidation rate with particle composition were quantified by measurement of the effective uptake coefficient, γeff, which is the loss rate of a species relative to the oxidant-particle collision rate. Instead of decreasing, the measured γeff increased continuously as the SOA coating thickness increased, by a factor of ∼2 for a SOA coating thickness of 42 nm (corresponding to ca. two-thirds of the particle mass). These results indicate that heterogeneous oxidation of ambient aerosol by OH radicals is not inhibited by SOA coatings, and further that condensed phase chemical pathways and rates in organic particles depend importantly on composition.