Terms like "elemental carbon" (EC), "soot", "black carbon" (BC), "graphitic" or "graphitic-like carbon", "light-absorbing", or "visible-absorbing" particles are typically used interchangeably by researchers in the fields of atmospheric and combustion science, industrial hygiene and public/environmental health sciences to distinguish between carbonaceous particles that have a continuous absorption spectra throughout the UV-visible-IR wavelength ranges from Organic Carbon (OC), which absorbs mostly in the UV and are virtually transparent to visible radiation. Flames and combustion devices operated in rich hydrocarbon conditions produce a large variety of carbonaceous compounds spanning from low and high molecular weight gas-phase polycyclic aromatic hydrocarbons (PAHs) to solid particles. In addition to soot or EC nanoparticles, recent works (Bockhorn et al, 2009) have demonstrated that nanoparticles with a more OC structure are formed in flames and combustion conditions near the onset of particle formation and are emitted to the atmosphere as primary emissions. The smallest particles formed in flames is about 2 nm, as determined by in situ extinction and scattering measurements, on-line Differential Mobility Analysis measurements of the size distribution, and Atomic Force Microscopy (AFM) measurements on particles deposited on substrates. In this work, we investigate carbon aerosols produced in various flame conditions by Thermo-optical-transmission (TOT), UV-vis and Raman spectroscopy in order to measure their OC and EC content in addition to their structural composition. The goal of the present work was to determine if and how combined TOT and optical/spectroscopic measurements allows distinguishing between flame-generated OC and EC nanoparticles. measured the OC-EC content, see Fig. 1, together with particle size distribution (PSD) and Raman spectra, see Fig. 2 of aerosols sampled from laboratory premixed flames operating in conditions near the onset of particles (namely non-sooting flame) and more fuel-rich flame condition (namely sooting flame). All of the samples have a significant amount of PC. The sample collected from the non-sooting flame is mostly OC with minor amounts of PC and EC. Instead, the sample collected early in the soot-forming flame is mostly PC with minor amounts of OC and EC. Late in the sooting flame after a significant amounts of soot is formed, TOT measurements found nearly equal fractions of PC and EC and extremely low amounts of OC. The analysis of the results allow to understand the chemical transformation as well as the aerosol partitioning between nucleation OC nanoparticles and EC/soot particles.
OC/EC analysis and Raman spectroscopy of flame-generated carbonaceous nanoparticles
M Commodo;P Minutolo
2015
Abstract
Terms like "elemental carbon" (EC), "soot", "black carbon" (BC), "graphitic" or "graphitic-like carbon", "light-absorbing", or "visible-absorbing" particles are typically used interchangeably by researchers in the fields of atmospheric and combustion science, industrial hygiene and public/environmental health sciences to distinguish between carbonaceous particles that have a continuous absorption spectra throughout the UV-visible-IR wavelength ranges from Organic Carbon (OC), which absorbs mostly in the UV and are virtually transparent to visible radiation. Flames and combustion devices operated in rich hydrocarbon conditions produce a large variety of carbonaceous compounds spanning from low and high molecular weight gas-phase polycyclic aromatic hydrocarbons (PAHs) to solid particles. In addition to soot or EC nanoparticles, recent works (Bockhorn et al, 2009) have demonstrated that nanoparticles with a more OC structure are formed in flames and combustion conditions near the onset of particle formation and are emitted to the atmosphere as primary emissions. The smallest particles formed in flames is about 2 nm, as determined by in situ extinction and scattering measurements, on-line Differential Mobility Analysis measurements of the size distribution, and Atomic Force Microscopy (AFM) measurements on particles deposited on substrates. In this work, we investigate carbon aerosols produced in various flame conditions by Thermo-optical-transmission (TOT), UV-vis and Raman spectroscopy in order to measure their OC and EC content in addition to their structural composition. The goal of the present work was to determine if and how combined TOT and optical/spectroscopic measurements allows distinguishing between flame-generated OC and EC nanoparticles. measured the OC-EC content, see Fig. 1, together with particle size distribution (PSD) and Raman spectra, see Fig. 2 of aerosols sampled from laboratory premixed flames operating in conditions near the onset of particles (namely non-sooting flame) and more fuel-rich flame condition (namely sooting flame). All of the samples have a significant amount of PC. The sample collected from the non-sooting flame is mostly OC with minor amounts of PC and EC. Instead, the sample collected early in the soot-forming flame is mostly PC with minor amounts of OC and EC. Late in the sooting flame after a significant amounts of soot is formed, TOT measurements found nearly equal fractions of PC and EC and extremely low amounts of OC. The analysis of the results allow to understand the chemical transformation as well as the aerosol partitioning between nucleation OC nanoparticles and EC/soot particles.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
