Emission characteristics of refractory black carbon aerosols from fresh biomass burning: A perspective from laboratory experiments

TY - JOUR

T1 - Emission characteristics of refractory black carbon aerosols from fresh biomass burning

T2 - A perspective from laboratory experiments

AU - Pan, Xiaole

AU - Kanaya, Yugo

AU - Taketani, Fumikazu

AU - Miyakawa, Takuma

AU - Inomata, Satoshi

AU - Komazaki, Yuichi

AU - Tanimoto, Hiroshi

AU - Wang, Zhe

AU - Uno, Itsushi

AU - Wang, Zifa

PY - 2017/11/6

Y1 - 2017/11/6

N2 - The emission characteristics of refractory black carbon (rBC) from biomass burning are essential information for numerical simulations of regional pollution and climate effects.We conducted combustion experiments in the laboratory to investigate the emission ratio and mixing state of rBC from the burning of wheat straw and rapeseed plants, which are the main crops cultivated in the Yangtze River Delta region of China. A single particle soot photometer (SP2) was used to measure rBC-containing particles at high temporal resolution and with high accuracy. The combustion state of each burning case was indicated by the modified combustion efficiency (MCE), which is calculated using the integrated enhancement of carbon dioxide and carbon monoxide concentrations relative to their background values. The mass size distribution of the rBC particles showed a lognormal shape with a mode mass equivalent diameter (MED) of 189 nm (ranging from 152 to 215 nm), assuming an rBC density of 1.8 g cm-3. rBC particles less than 80 nm in size (the lower detection limit of the SP2) accounted for ∼5% of the total rBC mass, on average. The emission ratios, which are expressed as ΔrBC =ΔCO (Δ indicates the difference between the observed and background values), displayed a significant positive correlation with the MCE values and varied between 1.8 and 34 ngm-3 ppbv-1. Multi-peak fitting analysis of the delay time (Δt, or the time of occurrence of the scattering peak minus that of the incandescence peak) distribution showed that rBC-containing particles with rBC MED = 200±10 nm displayed two peaks at Δt = 1.7 μs and Δt = 3.2 μs, which could be attributed to the contributions from both flaming and smoldering combustion in each burning case. Both the Δt values and the shell / core ratios of the rBC-containing particles clearly increased as the MCE decreased from 0.98 (smoldering-dominant combustion) to 0.86 (flaming-dominant combustion), implying the great importance of the rapid condensation of semi-volatile organics. This laboratory study found that the mixing state of rBC particles from biomass burning strongly depends on its combustion processes, and overall MCE should be taken carefully into consideration while the climate effect of rBC particles from open biomass burning is simulated.

AB - The emission characteristics of refractory black carbon (rBC) from biomass burning are essential information for numerical simulations of regional pollution and climate effects.We conducted combustion experiments in the laboratory to investigate the emission ratio and mixing state of rBC from the burning of wheat straw and rapeseed plants, which are the main crops cultivated in the Yangtze River Delta region of China. A single particle soot photometer (SP2) was used to measure rBC-containing particles at high temporal resolution and with high accuracy. The combustion state of each burning case was indicated by the modified combustion efficiency (MCE), which is calculated using the integrated enhancement of carbon dioxide and carbon monoxide concentrations relative to their background values. The mass size distribution of the rBC particles showed a lognormal shape with a mode mass equivalent diameter (MED) of 189 nm (ranging from 152 to 215 nm), assuming an rBC density of 1.8 g cm-3. rBC particles less than 80 nm in size (the lower detection limit of the SP2) accounted for ∼5% of the total rBC mass, on average. The emission ratios, which are expressed as ΔrBC =ΔCO (Δ indicates the difference between the observed and background values), displayed a significant positive correlation with the MCE values and varied between 1.8 and 34 ngm-3 ppbv-1. Multi-peak fitting analysis of the delay time (Δt, or the time of occurrence of the scattering peak minus that of the incandescence peak) distribution showed that rBC-containing particles with rBC MED = 200±10 nm displayed two peaks at Δt = 1.7 μs and Δt = 3.2 μs, which could be attributed to the contributions from both flaming and smoldering combustion in each burning case. Both the Δt values and the shell / core ratios of the rBC-containing particles clearly increased as the MCE decreased from 0.98 (smoldering-dominant combustion) to 0.86 (flaming-dominant combustion), implying the great importance of the rapid condensation of semi-volatile organics. This laboratory study found that the mixing state of rBC particles from biomass burning strongly depends on its combustion processes, and overall MCE should be taken carefully into consideration while the climate effect of rBC particles from open biomass burning is simulated.

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U2 - 10.5194/acp-17-13001-2017

DO - 10.5194/acp-17-13001-2017

M3 - Article

AN - SCOPUS:85032953521

VL - 17

SP - 13001

EP - 13016

JO - Atmospheric Chemistry and Physics

JF - Atmospheric Chemistry and Physics

SN - 1680-7316

IS - 21

ER -