Chemical characterisation of humic-like substances from urban, rural and tropical biomass burning environments using liquid chromatography with UV/vis photodiode array detection and electrospray ionisation mass spectrometry

Abstract

Environmental context. One of the most important classes of water-soluble organic compounds in continental fine and tropical biomass burning aerosol is humic-like substances (HULIS), which contain components with strong polar, acidic and chromophoric properties. We focus on the chemical characterisation of HULIS and provide evidence that nitro-aromatic catecholic compounds are among the major species of HULIS. This indicates that volatile aromatic hydrocarbons emitted during biomass burning are important gas-phase precursors for HULIS.Abstract. Humic-like substances (HULIS) are ubiquitously present in the troposphere and make up a major fraction of continental fine-sized water-soluble organic compounds. They are regarded as material with strong polar, acidic and chromophoric properties; however, structural information at the individual component level is rather limited. In the present study, we have characterised HULIS from different locations using liquid chromatography coupled to photodiode array detection and negative ion electrospray ionisation mass spectrometry. Aerosol samples with particles less than 2.5 mm in diameter (PM 2.5

Comparative study for separation of atmospheric humic-like substance (HULIS) by ENVI-18, HLB, XAD-8 and DEAE sorbents: Elemental composition, FT-IR, 1H NMR and off-line thermochemolysis with tetramethylammonium hydroxide (TMAH)

“…However, it is found that the HULIS samples isolated from different environments or sources, and from aerosol samples collected in different seasons can have different properties (Salma et al, , 2010Wex et al, 2007;Lin et al, 2010;Claeys et al, 2012;Fan et al, 2012;Song et al, 2012). Therefore, further efforts will be required in the future to comparative study the HULIS isolating methods, possibly using different HULIS samples isolated from rural, marine and biomass burning aerosol samples, and aerosol samples in different seasons.…”

The Molecular Identification of Organic Compounds in the Atmosphere: State of the Art and Challenges

“…This approach has been recently used in the study of nitrogen-containing compounds with chromophoric properties such as nitroaromatics and imidazoles. 333,44 But the level of identification in complex mixtures remains low and coupling high resolution MS with HPLC/UV-Vis detection is necessary to increase it.…”

“…Some atmospheric aerosols have been found to contain light-absorbing macromolecular fractions having properties similar to those of humic substances, and therefore termed humic-like substances. 333,354,491,498 However, the definition of atmospheric HULIS being based on their extraction procedure, 491,498a,498b it is difficult to attribute them to a single compound or source. HULIS are often linked to biomass burning aerosols 491 but have also been found in a wide range of atmospheric aerosols, including rural and remote ones.…”

“…444,483 They were also found in the HULIS fraction of biomass burning-influenced aerosols from Hungary and Brazil. 333 In all these studies the identification of the nitro-aromatic compounds was achieved by comparing the LC retention times and MS fragmentation patterns of the compounds present in the atmospheric samples, those present in laboratory-generated aerosols, and authentic standards. Very recently, the HPLC/ESI-MS/MS analysis of a series of nitroaromatic compounds in ambient aerosols was improved 379,387 by separating isobaric isomers, notably of methyl-nitrocatechols and nitro-guaiacol, by substituting acetonitrile with tetrahydrofuran in the LC eluent.…”

Climate engineering by mimicking natural dust climate control: the iron salt aerosol method

“…The sources of SOA are biogenic VOCs such as terpenes (Fry et al, 2014). HULISs contain polyphenolic redox mediators such as catechol and nitro-catechols (Claeys et al, 2012;Hoffer et al, 2004;Ofner et al, 2011;Pillar et al, 2014).…”