Mechanical and Thermal Properties of Biocomposites Based on Polyethylene from Renewable Resources Modified with Ionic Liquids

Journal of Polymers and the Environment - Biocomposites based on polyethylene from renewable resources derived from sugar cane as raw material were modified with phosphonium ionic liquids....     

Occupational Exposure to Polycyclic Aromatic Hydrocarbons During Diesel Combustion

Identification and determination of polycyclic aromatic hydrocarbons (PAHs) in Diesel exhaust in the working environment and assessment of workers’ occupational exposure to these suspected human carcinogens were the aim of this experimental investigation.

The range of exposure factors calculated on the basis of 9 individual PAH concentrations determined in personal air samples shows that time-averaged concentration of these compounds did not exceed the Polish Maximum Admissible Concentration (MAC) value for PAHs, that is, 2 μg·m^–3. The highest concentrations of PAHs were determined in the breathing zone of forklift operators. The maximum exposure factor was 0.427 μg·m^–3 (about 1/4 of MAC).     

Spatiotemporal trends of PM2.5 and its major chemical components at urban sites in Canada

To evaluate the effectiveness of emission control regulations designed for reducing air pollution, chemically resolved PM_2.5 data have been collected across Canada through the National Air Pollution Surveillance network in the past decade. 24-hr time integrated PM_2.5 collected at seven urban and two rural sites during 2010-2016 were analyzed to characterize geographical and seasonal patterns and associated potential causes. Site-specific seven-year mean gravimetric PM_2.5 mass concentrations ranged from 5.7 to 9.6 µg/m³. Seven-year mean concentrations of SO₄^2?, NO₃^?, NH₄⁺, organic carbon (OC), and elemental carbon (EC) were in the range of 0.68 to 1.6, 0.21 to 1.5, 0.27 to 0.71, 1.1 to 1.9, and 0.37 to 0.71 µg /m³, accounting for 10.8%-18.1%, 3.7%-16.7%, 4.7%-7.4%, 18.4%-21.0%, and 6.4%-10.6%, respectively, of gravimetric PM_2.5 mass. PM_2.5 and its five major chemical components showed higher concentrations in southeastern Canada and lower values in Atlantic Canada, with the seven-year mean ratios between the two regions being on the order of 1.7 for PM_2.5 and 1.8-7.1 for its chemical components. When comparing the concentrations between urban and rural sites within the same region, those of SO₄^2? and NH₄⁺ were comparable, while those of NO₃^?, OC, and EC were around 20%, 40%-50%, and 70%-80%, respectively, higher at urban than rural sites, indicating the regional scale impacts of SO₄^2? and NH₄⁺ and effects of local sources on OC and EC. Monthly variations generally showed summertime peaks for SO₄^2? and wintertime peaks for NO₃^?, but those of NH₄⁺, OC, and EC exhibited different seasonality at different locations.     

Characterisation of particulate exposure during fireworks displays

Little is known about the level and content of exposure to fine particles (PM_2.5) among persons who attend fireworks displays and those who live nearby. An evaluation of the levels of PM_2.5 and their elemental content was carried out during the nine launches of the 2007 Montréal International Fireworks Competition. For each event, a prediction of the location of the firework plume was obtained from the Canadian Meteorological Centre (CMC) of the Meteorological Service of Canada. PM_2.5 was measured continuously with a photometer (Sidepak?, TSI) within the predicted plume location (“predicted sites”), and integrated samples were collected using portable personal samplers. An additional sampler was located on a nearby roof (“fixed site”). The elemental composition of the collected PM_2.5 samples from the “predicted sites” was determined using both a non-destructive energy dispersive ED-XRF method and an ICP-MS method with a near-total microwave-assisted acid digestion. The elemental composition of the “fixed site” samples was determined by the ICP-MS with the near-total digestion method. The highest PM_2.5 levels reached nearly 10 000 μg m^?3, roughly 1000 times background levels. Elements such as K, Cl, Al, Mg and Ti were markedly higher in plume-exposed filters. This study shows that 1) persons in the plume and in close proximity to the launch site may be exposed to extremely high levels of PM_2.5 for the duration of the display and, 2) that the plume contains specific elements for which little is known of their acute cardio-respiratory toxicity.     

The effect of alkyl chain length on the degradation of alkylimidazolium- and pyridinium-type ionic liquids in a Fenton-like system

Background, aim, and scope  Ionic liquids are regarded as essentially “green” chemicals because of their insignificant vapor pressure and, hence, are a good alternative to the emissions of toxic conventional volatile solvents. Not only because of their attractive industrial applications, but also due to their very high stability, ionic liquids could soon become persistent contaminants of technological wastewaters and, moreover, break through into natural waters following classical treatment systems. The removal of harmful organic pollutants has forced the development of new methodologies known as advanced oxidation processes (AOPs). Among them, the Fenton and Fenton-like reactions are usually modified by the use of a higher hydrogen peroxide concentration and through different catalysts. The aim of this study was to assess the effect of hydrogen peroxide concentration on degradation rates in a Fenton-like system of alkylimidazolium ionic liquids with alkyl chains of varying length and 3-methyl-N-butylpyridinium chloride. Materials and methods  The ionic liquids were oxidized in dilute aqueous solution in the presence of two different concentrations of hydrogen peroxide. All reactions were performed in the dark to prevent photoreduction of Fe(III). The concentrations of ionic liquids during the process were monitored with high-performance liquid chromatography. Preliminary degradation pathways were studied with the aid of ¹H NMR. Results  Degradation of ionic liquids in this system was quite effective. Increasing the H₂O₂ concentration from 100 to 400 mM improved ionic liquid degradation from 57–84% to 87–100% after 60 min reaction time. Resistance to degradation was weaker, the shorter the alkyl chain. Discussion  The compound omimCl was more resistant to oxidation then other compounds, which suggests that the oxidation rates of imidazolium ionic liquids by OH· are structure-dependent and are correlated with the n-alkyl chain length substituted at the N-1-position. The level of degradation was dependent on the type of head group. Replacing the imidazolium head group with pyridinium increased resistance to degradation. Nonetheless, lengthening the alkyl chain from four to eight carbons lowered the rate of ionic liquid degradation to a greater extent than changing the head group from imidazolium to pyridinium. 1H-NMR spectra show, in the first stage of degradation, that it is likely that radical attack is nonspecific, with any one of the carbon atoms in the ring and the n-alkyl chain being susceptible to attack. Conclusions  The proposed method has proven to be an efficient and reliable method for the degradation of imidazolium ionic liquids by a Fenton-like reagent deteriorated with lengthening n-alkyl substituents and by replacing the imidazolium head group with pyridinium. The enhanced resistance of 1-butyl-3-methylpyridinium chloride when the resistance of imidazolium ionic liquids decreases with increasing H₂O₂ concentration is probably indicative of a change in the degradation mechanism in a vigorous Fenton-like system. H-NMR spectra showed, in the first stage of degradation, that radical attack is nonspecific, with any one of the carbon atoms in the ring and the n-alkyl chain being susceptible to attack. Recommendations and perspectives  Since ionic liquids are now one of the most promising alternative chemicals of the future, the degradation and waste management studies should be integrated into a general development research of these chemicals. In the case of imidazolium and pyridinium ionic liquids that are known to be resistant to bio- or thermal degradation, studies in the field of AOPs should assist the future structural design as well as tailor the technological process of these chemicals     

Adaptive alterations in the fatty acids composition under induced oxidative stress in heavy metal-tolerant filamentous fungus Paecilomyces marquandii cultured in ascorbic acid presence

The ability of the heavy metal-tolerant fungus Paecilomyces marquandii to modulate whole cells fatty acid composition and saturation in response to IC₅₀ of Cd, Pb, Zn, Ni, and Cu was studied. Cadmium and nickel caused the most significant growth reduction. In the mycelia cultured with all tested metals, with the exception of nickel, a rise in the fatty acid unsaturation was noted. The fungus exposure to Pb, Cu, and Ni led to significantly higher lipid peroxidation. P. marquandii incubated in the presence of the tested metals responded with an increase in the level of linoleic acid and escalation of electrolyte leakage. The highest efflux of electrolytes was caused by lead. In these conditions, the fungus was able to bind up to 100 mg?g^?1 of lead, whereas the content of the other metals in the mycelium was significantly lower and reached from 3.18 mg?g^?1 (Cu) to 15.21 mg?g^?1 (Zn). Additionally, it was shown that ascorbic acid at the concentration of 1 mM protected fungal growth and prevented the changes in the fatty acid composition and saturation but did not alleviate lipid peroxidation or affect the increased permeability of membranes after lead exposure. Pro-oxidant properties of ascorbic acid in the copper-stressed cells manifested strong growth inhibition and enhanced metal accumulation as a result of membrane damage. Toxic metals action caused cellular modulations, which might contributed to P. marquandii tolerance to the studied metals. Moreover, these changes can enhance metal removal from contaminated environment.     

Effect of housing geometry on the performance of Chemcatcher passive sampler for the monitoring of hydrophobic organic pollutants in water

Passive sampling of pollutants in water has been gaining acceptance for environmental monitoring. Previously, an integrative passive sampler (the Chemcatcher) was developed and calibrated for the measurement of time weighted average concentrations of hydrophobic pollutants in water. Effects of physicochemical properties and environmental variables (water temperature and turbulence) on kinetic and thermodynamic parameters characterising the exchange of analytes between the sampler and water have been published. In this study, the effect of modification in sampler housing geometry on these calibration parameters was studied. The results obtained for polycyclic aromatic hydrocarbons show that reducing the depth of the cavity in the sampler body geometry increased the exchange kinetics by approximately twofold, whilst having no effect on the correlation between the uptake and offload kinetics of analytes. The use of performance reference compounds thus avoids the need for extensive re-calibration when the sampler body geometry is modified.     

Novel Tough Crystalline Blends of Polylactide with Ethylene Glycol Derivative of POSS

Blending of polylactide (PLA) with low stereoregularity and polyhedral oligomeric silsesquioxane grafted with arms of poly(ethylene glycol) methyl ether, acting as a plasticizer, allowed us previously to obtain a novel stable elastomeric-like material. The present contribution focuses on the properties of semi-crystalline PLA plasticized with this compound. Melt blends of PLA with 5–15 wt% of the plasticizer, were compression molded, quenched and annealed, which enabled cold-crystallization. The glass transition temperature of the blends and their drawability depended on their crystallinity and plasticizer content. The best ductility was reached at the plasticizer content of 15 wt%; the achieved strain at break was 6.5 (650%) and 1.3 (130%), for the quenched and annealed material, respectively. The latter value exceeded 20 times the strain at break of neat crystalline PLA. The tensile toughness of the annealed 15 wt% blend was 12 times larger than that of crystalline PLA. Moreover, annealing of 15 wt% blend improved its yield strength by 40%. Despite the two peaks of the loss modulus, indicating the two glass transitions in this blend, no heterogeneities were found by scanning electron microscopy, indicating that the plasticizer enriched phase formed instead of distinct inclusions of the plasticizer.     

Air toxics in Canada measured by the National Air Pollution Surveillance (NAPS) program and their relation to ambient air quality guidelines

This study reports ambient concentrations of 63 air toxics that were measured in Canada by the National Air Pollution Surveillance (NAPS) program over the period 2009–2013. Measured concentrations are compared with ambient air quality guidelines from Canadian jurisdictions, and compounds that exceeded guidelines are identified and discussed. Although this study does not assess risk or cumulative effects, air toxics that approached guidelines are also identified so that their potential contribution to ambient air toxics pollution can be considered. Eleven air toxics exceeded at least one guideline, and an additional 16 approached guidelines during the study period. Four compounds were measured using methods whose detection limits exceeded a guideline value, three of which could not be compared with guidelines, since they were not detected in any samples. The assessment of several metal(loid) concentrations is tentative, since they were measured only in fine particulate matter (PM) but compared with guidelines based on coarse or total PM. Improvements to sampling and analysis techniques for the latter compounds as well as for those whose methods are subject to known uncertainties would improve confidence in reported concentrations and their relation to applicable guidelines. Analysis of sampling strategies for all compounds found to exceed or approach guidelines would contribute to ensuring that their spatiotemporal coverage is adequate. Examination of the air toxics not measured by NAPS but having guidelines in Canadian jurisdictions or being included in other programs such as the U.S. National-Scale Air Toxics Assessment (NATA) would contribute to ensuring that the full suite of pollutants relevant to ambient air quality in Canada is subject to adequate study. The results of this study can be applied to evaluating the effectiveness of toxic substances management in Canada.

Implications: Recent measurements of 63 air toxics in Canada by the National Air Pollution Surveillance (NAPS) program showed that 11 compounds exceeded daily or annual ambient air quality guidelines and that an additional 16 compounds approached such guidelines within an order of magnitude. The results of this study can be applied to evaluating the effectiveness of toxic substances management in Canada and to identifying compounds that merit further investigation.