In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 20, No. 8 ( 2020-04-21), p. 4593-4605
Abstract:
Abstract. Biomass burning (BB) emits large amounts of brown carbon (BrC); however, the
evolutionary behavior of BrC in BB emissions (BB BrC) resulting from complex
atmospheric processes is poorly understood. In this study, the
transformation of contents and the chromophoric characteristics of BrC in
smoke particles emitted by the burning of rice straw (RS), corn straw (CS), and pinewood (PW) under O3 aging are investigated. The O3 aging
induced the reduction of light absorption and fluorescence for the BB BrC,
suggesting the decomposition of chromophores and fluorophores. These changes
were accompanied by a decrease in aromaticity, average molecular weight, and
the light absorption capacity for the chromophores, as well as an increase in humification for the fluorophores. The excitation emission matrix combined
with a parallel factor analysis revealed that protein-like components (C3)
were predominantly decomposed by O3 aging, while the relative
distribution of a humic-like component with highly oxygenated chromophores
(C4) gradually increased. In general, the humic-like substances
(C1 + C2 + C4) were transformed to be the most abundant fluorophores for all
the BB BrC samples, which accounted for 84 %–87 % of the total
fluorophores in final O3-aged BB BrC. Two-dimensional correlation
spectroscopy (2D-COS) was performed on the synchronous fluorescence, which
suggested that the RS and CS BrC exhibits the same susceptible
fluorophores changes upon O3 aging. It showed that O3 firstly
reacted with protein-like fractions (263–289 nm) and then with fulvic-like
fractions (333–340 nm). In comparison, the changing sequence of susceptible
fluorophores in the PW BrC to O3 was in the order of fulvic-like fluorophores with
shorter wavelengths (309 nm), protein-like fluorophores (276 nm), and fulvic-like fluorophores with longer wavelengths (358 nm). The
2D-FTIR-COS (2D-COS combined with FTIR) analysis showed conjugated C=O and aromatic C=C and C=O
groups were the most susceptible functional groups to O3 aging for all
BB BrC. Moreover, it also revealed a consistent sequential change, which is in the order of aromatic OH; conjugated C=O groups and aromatic C=O;
aromatic COO−; and finally lignin-derived C–C, C–H, and C–O groups. Our
results provide new insights into the evolutionary behavior of the
chromophoric and fluorescent properties of BB BrC during O3 aging,
which are of great significance for better understanding the heterogeneous
oxidation pathways of BB-derived BrC in the atmospheric environment.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-20-4593-2020
DOI:
10.5194/acp-20-4593-2020-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2020
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1
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