Seasonal variability of nitroaromatic compounds in ambient aerosols: Mass size distribution, possible sources and contribution to water-soluble brown carbon light absorption

(Marie Curie FP7-PEOPLE-2011-COFUND, project NEWFELPRO) Frka, Sanja; Šala, Martin; Brodnik, Helena; Štefane, Bogdan; Kroflič, Ana; Grgić, Irena (2022) Seasonal variability of nitroaromatic compounds in ambient aerosols: Mass size distribution, possible sources and contribution to water-soluble brown carbon light absorption. Chemosphere, 299 . ISSN 0045-6535

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Abstract

Nitroaromatic compounds (NACs) as important constituents of atmospheric humic like substances (HULIS) and brown carbon (BrC) affect the Earth’s climate and pose a serious environmental hazard. We investigated seasonal size-segregated NACs in aerosol samples from the urban background environment in Ljubljana, Slovenia. Total concentrations of twenty NACs in PM15.6 were on average from 0.51 ng m-3 (summer) to 109 ng m-3 (winter), and contributed the most to submicron aerosols (more than 74%). Besides 4-nitrocatechol (4NC) as the prevailing species, methylnitrocatechols (MNCs) and nitrophenols (NPs), we reported on some very rarely mentioned, but also on five novel NACs (i.e., 3-hydroxy-4-nitrobenzoic acid: 3H4NBA, 3MeO4NP: 3-metoxy-4-nitrophenol, 4Et5NC: 4-ethyl-5-nitrocatechol, 3Et5NC: 3-ethyl-5-nitrocatechol and 3MeO5NC. 3-methoxy-5-nitrocatechol). Concentrations of 3MeO5NC, 4Et5NC and 3Et5NC were enhanced during cold seasons, contributing up to 11% to total NAC in winter. In cold season, NAC size distributions were characterized with the peaks in the broader size range of 0.305–1.01 μm (accumulation mode), with 4NC and alkyl-nitrocatechols (∑(M/Et)NC) as the most abundant, followed by 4-nitrosyringol, nitrophenols and nitroguaiacols. In spring, the pronounced peak of ∑(M/Et)NC was observed in the accumulation mode (0.305–0.56 μm) as well as in the coarse one. A strong correlation of all NACs with ∑(M/Et)NC and levoglucosan indicates that primary emissions of wood burning were the most important source of NACs, but their secondary formation (e.g., aqueous-phase at higher ambient RH) in cold season could also be a significant one. In warmer season, NACs may be mostly derived from traffic-related aromatic VOCs. The contribution of NACs to the light absorption of the aqueous extracts was up to 10-times higher (contribution to Abs365 up to 31%) than their mass contributions to WSOC (up to 3%) of corresponding size-segregated aerosols, confirming that most of the identified NACs are strong BrC chromophores.

Item Type:	Article
Uncontrolled Keywords:	Nitroaromatic compounds, Water-soluble organic carbon, Size distribution, Brown carbon, Biomass burning
Subjects:	NATURAL SCIENCES > Interdisciplinary Natural Sciences > Marine Science
Divisions:	Division for Marine and Enviromental Research
Projects:	Project title Project leader Project code Project type Chemical nature of size segregated water soluble organic aerosols in their nitro-aromatic constituents-AERONAR, Marie Curie FP7-PEOPLE-2011-COFUND Sanja Frka Milosavljević 47 MZOS
Depositing User:	Sanja Frka Milosavljević
Date Deposited:	08 Mar 2024 09:10
URI:	http://fulir.irb.hr/id/eprint/8724
DOI:	10.1016/j.chemosphere.2022.134381

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