On time dynamics of the complex refractive index and particle microstructure according to data of spectronephelometer measurements in mixed-composition smokes

Abstract

The specific features in the dynamics of the complex refractive index (CRI) are studied for three particle fractions during aging of mixed composition wood smokes, generated due to simultaneous particle emission from two sources in the regimes of pyrolysis and flaming combustion, for two days. The initial stage is characterized by the generation of smoke in which the imaginary part of the particle refractive index χ decreases, on average, by a factor of 600 with the growth of particle size. When smoke is aged for a long time, χ decreases (by a factor of 1.2) for ultrafine black carbon particles, simultaneously increasing for moderately (by a factor of 1.5) and coarsely (by a factor of 4.7) dispersed particles. This suggests that the dynamics of microphysical smoke composition, at all stages of its existence, is mainly determined by the coagulation driven penetration of black carbon from the nanometer size range toward the region of larger particle sizes. Numerical experiment showed that the inverse problem during aging of mixed composition smokes can be solved correctly only using CRI values strictly corresponding to a given time instant. Attempts to solve the inverse problem using some time invariable CRI values lead to a several fold increase in the discrepancy between the measured and retrieved optical characteristics versus the 6-10% discrepancy for the actual CRI values. Test ing of the three fraction method for solving the inverse problem with the help of modeled aerosol with a known CRI (ethylene glycol) showed that our approach ensured high accuracy retrieval of the true CRI for the optically active particles in a moderately dispersed size range. Using the three fraction method decreases the discrepancy, on average, by a factor of two versus the traditional one fraction method (assuming that par ticles are homogeneous in the nature).

Optical-microphysical and physical-chemical characteristics of Siberian biomass burning: small-scale fires in an aerosol chamber

“… ðåaeèìå ñìåøàííîãî ãîðåíèÿ îäèíàêîâûå ìàññû ìàòåðèàëà îäíîâðåìåííî ñaeèãàëèñü ïðè ðàçíûõ òåìïåðàòóðíûõ óñëîâèÿõ îòêðûòîãî ãîðåíèÿ è òëåíèÿ. Ñ ìîìåíòà íà÷àëà ãîðåíèÿ íåïðåðûâíî ðåãèñòðèðîâàëèñü óãëîâûå êîýôôèöèåíòû àýðîçîëüíîãî ðàññåÿíèÿ íà ÷åòûðåõ äëèíàõ âîëí, ïÿòè óãëàõ ðàññåÿíèÿ è ïðè äâóõ ñîñòîÿíèÿõ ïîëÿðèçàöèè ñ ïîìîùüþ ñïåêòðîíåôåëîìåòðà [23]. Ðåøàëàñü îáðàòíàÿ çàäà÷à äëÿ îïðåäåëåíèÿ ðàñïðåäåëåíèÿ ïî ðàçìåðàì îáúåìà äûìîâûõ ÷àñòèö è êîìïëåêñíîãî ïîêàçàòåëÿ ïðåëîìëåíèÿ â òðåõ èíòåðâàëàõ äèñïåðñíîñòè ïî ìåòîäèêå [24].…”

“…Âñëåäñòâèå ýòîãî äëÿ ñðåäíåäèñïåðñíûõ è êðóïíûõ ÷àñòèö äîñòèãàþòñÿ äîñòàòî÷íî âûñîêèå çíà÷åíèÿ óìåðåííîãî ïîãëîùåíèÿ ∼ 0,16-0,07, è ïîãëîùàòåëüíàÿ ñïîñîáíîñòü ÷àñòèö îáíàðóaeèâàåò òåíäåíöèþ óìåíüøåíèÿ ñ ðîñòîì ðàçìåðà ÷àñòèö [23]. Ñìåøàííûå äûìû ÿâëÿþòñÿ ñèëüíîïîãëîùàþùèìè, äëÿ íèõ çíà÷åíèÿ ÀÎÐ äîñòèãàþò 0,60-0,45, óìåíüøàÿñü ïðè ñòàðåíèè äûìà.…”

Russian National Report: Meteorology and Atmospheric Sciences

“…Laboratory studies of aerosol characteristics under the artificial moistening (from 1998) and optical and radiative smoke parameters have been conducted [Rakhimov et al, 2012[Rakhimov et al, , 2014 at the IAO SB RAS. Results of multi-year studies of the aerosol condensation activity in Tomsk are integrated [Panchenko et al, 2012a;Terpugova et al, 2012].…”

“…Spatiotemporal aerosol characteristics (aerosol optical thickness, AOT; microphysical properties) have been investigated for different regions of Russia and other countries [128][129][130][131][132][133][134][135][136][137][138][139][140][141][142][143][144][145], including polar regions [146][147][148][149][150][151][152][153][154][155], and sea regions [156][157][158][159][160]. In papers [161][162][163][164][165], chemical aerosol properties, including ion composition, have been studied.…”

Small-Scale Study of Siberian Biomass Burning: II. Smoke Hygroscopicity

“…Optical and microphysical properties of aerosols from small-scale fires of Siberian biomass were investigated in a Large Aerosol Chamber (LAC) of the IAO, Tomsk (Rakhimov et al, 2012). Individual particle analysis in terms of smoke morphology and elemental composition revealed a strong dependence on combustion temperature, i.e., a dominant abundance of soot agglomerates versus roughly spherical organic particles in the flaming and smoldering phase, respectively (Popovicheva et al, 2015b).…”