https://uhra.herts.ac.uk/bitstream/handle/2299/1986/901994.pdf?sequence=1

Atmospheric polycyclic aromatic hydrocarbons: Source attribution, emission factors and regulation

Ultrasound assisted extraction of food and natural products. Mechanisms, techniques, combinations, protocols and applications. A review.

PAH diagnostic ratios for the identification of pollution emission sources

. In this study, 121 daily PM2.5 (aerosol particle with aerodynamic diameter less than 2.5 μm) samples were collected from an urban site in Beijing in four months between April 2009 and January 2010 representing the four seasons. The samples were determined for various compositions, including elements, ions, and organic/elemental carbon. Various approaches, such as chemical mass balance, positive matrix factorization (PMF), trajectory clustering, and potential source contribution function (PSCF), were employed for characterizing aerosol speciation, identifying likely sources, and apportioning contributions from each likely source. Our results have shown distinctive seasonality for various aerosol speciations associated with PM2.5 in Beijing. Soil dust waxes in the spring and wanes in the summer. Regarding the secondary aerosol components, inorganic and organic species may behave in different manners. The former preferentially forms in the hot and humid summer via photochemical reactions, although their precursor gases, such as SO2 and NOx, are emitted much more in winter. The latter seems to favorably form in the cold and dry winter. Synoptic meteorological and climate conditions can overwhelm the emission pattern in the formation of secondary aerosols. The PMF model identified six main sources: soil dust, coal combustion, biomass burning, traffic and waste incineration emission, industrial pollution, and secondary inorganic aerosol. Each of these sources has an annual mean contribution of 16, 14, 13, 3, 28, and 26%, respectively, to PM2.5. However, the relative contributions of these identified sources significantly vary with changing seasons. The results of trajectory clustering and the PSCF method demonstrated that regional sources could be crucial contributors to PM pollution in Beijing. In conclusion, we have unraveled some complex aspects of the pollution sources and formation processes of PM2.5 in Beijing. To our knowledge, this is the first systematic study that comprehensively explores the chemical characterizations and source apportionments of PM2.5 aerosol speciation in Beijing by applying multiple approaches based on a completely seasonal perspective.

/pdf/chemical-characterization-and-source-apportionment-of-pm-2-5-3q6oghogl3.pdf

Chemical characterization and source apportionment of PM 2.5 in Beijing: seasonal perspective

Essential oils: from extraction to encapsulation.

An improved microwave Clevenger apparatus for distillation of essential oils from orange peel.

Comparison of two isolation methods for essential oil from rosemary leaves: Hydrodistillation and microwave hydrodiffusion and gravity

Traditional hydrodistillation (HD), cold pressing (CP) and innovative microwave ‘dry’ distillation or microwave-accelerated distillation (MAD) methods have been compared and evaluated for their effectiveness in the isolation of essential oil from fresh Citrus peels. The microwave method offers important advantages over traditional alternatives, viz. shorter extraction times (30 min vs. 3 h for hydrodistillation and 1 h for cold pressing); better yields (0.24% vs. 0.21% for HD and 0.05% for CP); environmental impact (energy cost is appreciably higher for performing HD and for mechanical motors (CP) than that required for rapid MAD extraction); cleaner features (as no residue generation and no water or solvent used); increases antimicrobial activities; and provides a more valuable essential oil (with high amounts of oxygenated compounds). It also offers the possibility for better reproduction of the natural aroma of the essential oil from Citrus fruit compared with CP, but more than the HD essential oil. Further, the microwave procedure yields essential oils that can be analysed or used directly without any clean-up, solvent exchange or centrifugation steps. Scanning electron microscopy provides more evidence of the cleanness of microwave extraction, in contrast to the huge perforations on the external surface of the Citrus fruit peel in the case of conventional hydrodistillation. Finally, a mechanism of microwave ‘dry’ distillation is proposed and discussed. Copyright © 2007 John Wiley & Sons, Ltd.

Brahim Youcef Meklati

Papers

An improved microwave Clevenger apparatus for distillation of essential oils from orange peel.

Comparison of two isolation methods for essential oil from rosemary leaves: Hydrodistillation and microwave hydrodiffusion and gravity

Comparison of different isolation methods of essential oil from Citrus fruits: cold pressing, hydrodistillation and microwave ‘dry’ distillation

A new process for extraction of essential oil from Citrus peels: microwave hydrodiffusion and gravity.

Particulate n-alkanes, n-alkanoic acids and polycyclic aromatic hydrocarbons in the atmosphere of Algiers City Area