Investigating the dependence of light-absorption properties of combustion carbonaceous aerosols on combustion conditions

Characteristics of BrC and BC emissions from controlled diffusion flame and diesel engine combustion

“…For soot exposed to higher temperatures the carbon nanostructure evolves by growth of aromatic clusters, which can be monitored on-line using the refractory analysis. Our data, in line with the literature (Minutolo et al 1996, Bond 2001, Cheng et al 2019, shows that this growth of aromatic clusters results in a lower optical band gap and consequently a lower AAE. Our results therefore strongly support the hypothesis of a brown-black absorption continuum posited by Saleh et al (2018), in which BrC characteristics in combustion emissions can be attributed to refractory and non-refractory A c c e p t e d M a n u s c r i p t carbonaceous material that formed in the flame environment but did not fully mature to BC.…”

“…The data presented in Figure 5 thus suggest that refractory OC components were responsible for the BrC absorption characteristics. However, refractory OC components can have a wide spread in both absorption wavelength dependence and absorption efficiency (or mass specific absorption cross section), and these are inversely related to each other (Saleh et al 2018, Cheng et al 2019. Bescond et al (2016), while using different operating settings, showed that light absorption of miniCAST soot increased at short wavelengths, and decreased at longer wavelengths with an increasing OC fraction.…”

“…The absorption wavelength dependence decreases when the soot matures and typically approaches AAEs close to 1 for mature soot (refractory BC materials) (Simonsson et al 2015, Wang et al 2016. For real-world combustion emissions, the maturity level of soot and composition of combustion generated PM emissions have a strong dependence on combustion temperature (Bond et al 2006, Saleh et al 2018, Cheng et al 2019. Generalizing, BC is emitted from combustion sources where the soot has evolved in high temperature combustion environments, for example in combustion engines (Maricq 2014, Malmborg et al 2017.…”

A dominant contribution to light absorption by methanol-insoluble brown carbon produced in the combustion of biomass fuels typically consumed in wildland fires in the United States

“…In reality, it is possible that some strongly absorbing, refractory BrC is mistakenly classied as EC by thermal-optical measurements. 18,22,38 Thus, OC MIBrC could be underestimated and EC overestimated in the analysis.…”

“…[13][14][15][16][17][18] At the same time, the wavelength dependence of BrC absorption is also highly variable, with stronger wavelength dependence exhibited by the less absorbing BrC. 13,14,[19][20][21][22][23] While BrC was originally thought to be solely produced by low-temperature, smoldering biomass combustion, more recent works have identied BrC species emitted from higher-temperature biomass combustion 13,[19][20][21]24 as well as the combustion of liquid fossil fuels. 18,22,25 In addition, the operational denitions of BrC have expanded to include strongly absorbing, non-volatile, and refractory species.…”