Chemical characterization of laboratory-generated tar ball particles

Abstract

Abstract. The chemical properties of laboratory-generated tar ball (Lab-TB) particles produced from dry distillate (wood tars) of three different wood species in the laboratory were investigated by analytical techniques that had never been used before for their characterization. The elemental compositions of laboratory-generated tar balls (LabTBs) from three tree species were very similar to one another and to those characteristic of atmospheric tar balls (TBs) collected from the savanna fire during the SAFARI 2000 sampling campaign. The O / C and H / C molar ratios of the generated Lab-TBs were at the upper limit characteristic of soot particles. The Fourier transform infrared spectroscopy (FT-IR) spectra of the generated Lab-TBs were very similar to one another as well and also showed some similarity with those of atmospheric humic-like substances (HULIS). The FT-IR measurements indicated that Lab-TBs have a higher proportion of aromatic structure than HULIS and the oxygen atoms of Lab-TBs are mainly found in hydroxyl and keto functional groups. Whereas Raman activity was detected in the starting materials of the Lab-TBs (wood tars) in the range of 1000-1800 cm −1 , the Raman spectra of TBs were dominated by two pronounced bands with intensity maxima near 1580 (G band) and 1350 cm −1 (D band), indicating the presence of sp 2 -hybridized carbon structures and disorder in them, respectively. In the Py-GC-MS chromatograms of the Lab-TBs mostly aromatic compounds (aromatic hydrocarbons, oxygenated aromatics and heterocyclic aromatics) were identified in accordance with the results of Raman and FT-IR spectroscopy. According to organic carbon / elemental carbon (OC / EC) analysis using EUSAAR_2 thermal protocol, 22 % of the total carbon content of Lab-TBs was identified as EC, contrary to expectations based on the current understanding that negligible if any EC is present in this subfraction of the brown carbon family. Our results suggest that spherical atmospheric TBs with high C / O molar ratios are closer to BC in many of their properties than to weakly absorbing HULIS.

Mechanisms of lung toxicity induced by biomass burning aerosols

“…Based on our previous and current studies, wood tar aerosols generated by nebulizing the water-soluble extract from pyrolyzed wood are good proxies for atmospheric wood tar particles [19,20,[38][39][40]. In this study, the water-soluble wood tar extracts were used in two different concentrations for the in vivo experiments.…”

Gasification of wastes: The impact of the feedstock type and co‐gasification on the formation of volatiles and char

“…Furthermore, the band at 1600 cm −1 was related to the CC stretching of aromatic rings. Furthermore, the band at 1450 cm −1 was assigned to CH 3 . All the char samples produced in this study were quite aliphatic, showing a strong absorption of CO functionality at 1200 cm −1 .…”

“…CO functionality was also observed at 1250 cm −1 for the tar produced from the gasification of the plastic and mixture feedstock, showing that their tars were also aliphatic. A sharp peak was also recorded at 1050 cm −1 for all the tar samples, which is probably related to alcohols . At 700 cm −1 , aromatic bands were seen for all the tar samples with almost similar abundance.…”

“…A sharp peak was also recorded at 1050 cm −1 for all the tar samples, which is probably related to alcohols. 32,46,47 At 700 cm −1 , aromatic bands 32 were seen for all the tar samples with almost similar abundance. By comparing the IR spectra of different tar samples, it can be concluded that tars from single feedstock showed different distribution and intensities of the functionalities.…”

“…Furthermore, the band at 1450 cm −1 was assigned to CH 3 . 32,46,47 All the char samples produced in this study were quite aliphatic, showing a strong absorption of C O functionality at 1200 cm −1 . 46,47 Comparing Figures 1 and 6 shows that through the gasification process, the functionalities can be changed, particularly their abundance in the char can be altered due to cracking, pyrolysis, oxidation, polymerization, and other possible reactions.…”