Atmospheric tar balls: aged primary droplets from biomass burning?

Tóth, Ágnes; Hoffer, András; Nyírő-Kósa, Ilona; Pósfai, Mihály; Gelencsér, András

doi:10.5194/acp-14-6669-2014

Cited by 70 publications

(84 citation statements)

References 23 publications

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“…Briefly, liquid tar was produced from dry distillation of 2 different wood types (Robinia pseudoacacia (black locust) and Picea abies (Norway spruce)) similar to that described in Tóth et al (2014). The obtained liquid distillate consisted of an aqueous phase and an oily 20 phase.…”

Section: Methodsmentioning

confidence: 99%

“…Recently Tóth et al (2014) have demonstrated that tar balls very similar to those observed in the atmosphere can be directly produced in the laboratory from liquid tar obtained by the dry 5 distillation of wood. This lab experiment postulates that during biomass combustion direct ejection of liquid tar droplets from the pores followed by atmospheric aging generates tar ball particles in biomass smoke plumes.…”

Section: Introductionmentioning

confidence: 99%

“…Hoffer et al (2016) measured the optical properties of tar balls generated with the above procedure, but they investigated the 10 absorption parameters only up to 652 nm wavelength. In this study, similarly to the study by Tóth et al (2014) and Hoffer et al (2016) we generated tar balls in a laboratory from the dry distillate of hardwood (black locust) and softwood (Norway spruce) and measured the absorption properties up to 950 nm.…”

Section: Introductionmentioning

confidence: 99%

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Brown carbon absorption in the red and near infrared spectral region

Hoffer

Tóth

Pósfai

et al. 2016

Preprint

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Black carbon aerosols have been conventionally assumed to be the only light-absorbing carbonaceous particles in the red and near-infrared spectral regions of solar radiation in the atmosphere. Here we report that contrary to the conventional belief tar balls (a specific type of 5 organic aerosol particles from biomass burning) do absorb red and near infrared radiation significantly. Tar balls were produced in a laboratory experiment and their chemical and optical properties were measured. The absorption of these particles in the range between 470 and 950 nm was measured with an aethalometer, which is widely used to measure aerosol absorption in the field. We find that the absorption coefficient of tar balls at 880 nm exceeds 10% of that at 10 470 nm. This substantial absorption of red and infrared light is also evident from a relatively low Ångström coefficient (and a significant mass absorption coefficient) of tar balls between 470 and 950 nm. Retrievals of aerosol column optical properties from a global network of surface stations over vast tropical areas dominated by biomass burning suggest that tar balls are the predominant light-absorbing species of organic aerosols over acetone/methanol-soluble BrC or HULIS. Our 15 results also infer that the role of BC (including Diesel soot) in global climate forcing has likely been overestimated at the expense of brown carbon (BrC) from biomass burning.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Brown carbon absorption in the red and near infrared spectral region

Hoffer

Tóth

Pósfai

et al. 2016

Preprint

Self Cite

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“…In our previous works (Tóth et al, 2014;Hoffer et al, 2016) an experimental setup has been developed for the generation of TB particles in the laboratory without the concurrent emission of other combustion products. The morphological and structural characteristics and the elemental composition of the TB particles generated by this experimental system were highly similar to those of atmospheric TBs.…”

Section: Introductionmentioning

confidence: 99%

Chemical characterization of laboratory-generated tar ball particles

Tóth¹,

Hoffer²,

Pósfai³

et al. 2018

Preprint

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Abstract. The chemical properties of tar ball (TB) particles generated 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 composition of TB particles from three tree species were very similar to one another and to those characteristic for atmospheric tar balls (TBs) collected from savanna fire during the SAFARI 2000 sampling campaign. The O/C and H/C molar ratios of the generated TBs were at the upper limit characteristic for soot particles. The FT-IR spectra of the generated TBs were 15 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 laboratory-generated TBs have a higher proportion of aromatic structure than HULIS and the oxygen atoms of TBs are mainly found in hydroxyl and keto functional groups. Whereas the starting materials of the TBs (wood tars) were Raman inactive in the range of 1000-1800 cm structures and disorder in them, respectively. In the Py-GC-MS chromatograms of the laboratory-generated 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 OC/EC analysis using EUSAAR_2 long thermal protocol, 22% of the total carbon content of laboratory-generated TBs was identified as elemental carbon (EC), contrary to expectations based on the current understanding that negligible if any EC is present in this sub-fraction of the brown carbon family. Our results suggest that 25 spherical atmospheric TBs with high C/O molar ratios are closer to BC in many of their properties than to weakly absorbing HULIS.

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“…Thus, the chemical properties of TBs can only be studied by single-particle analytical techniques such as TEM-EDS or SEM-EDS Pósfai et al, 2003Pósfai et al, , 2004Hand et al, 2005;Niemi et al, 2006;Adachi and Buseck, 2011;Chakrabarty et al, 2016;Adachi et al, 2017;Cong et al, 2009Cong et al, , 2010China et al, 2013;Chakrabarty et al, 2006Chakrabarty et al, , 2010Semeniuk et al, 2007), TEM with electron energy-loss spectroscopy (TEM-EELS) (Hand et al, 2005, Adachi andBuseck, 2011), and near-edge X-ray absorption fine-structure spectroscopy (NEXAFS) using a synchrotron source (Tivanski et al, 2007). In our previous works (Tóth et al, 2014;Hoffer et al, 2016) an experimental setup had been developed for the generation of TB particles in the laboratory without the concurrent emission of other combustion products. The structural characteristics (homogeneity) and the elemental composition of the TB particles generated by this experimental system were highly similar to those of atmospheric TBs published by Pósfai et al (2004) and Adachi and Buseck et al (2011) as the Lab-TBs have homogenous internal structure without core and concentrically wrapped graphitic layers.…”

Section: Introductionmentioning

confidence: 99%

Chemical characterization of laboratory-generated tar ball particles

Tóth

Hoffer²,

Pósfai

et al. 2018

Atmos. Chem. Phys.

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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.

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Atmospheric tar balls: aged primary droplets from biomass burning?

Cited by 70 publications

References 23 publications

Brown carbon absorption in the red and near infrared spectral region

Brown carbon absorption in the red and near infrared spectral region

Chemical characterization of laboratory-generated tar ball particles

Chemical characterization of laboratory-generated tar ball particles

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