Chemical Fingerprinting of HULIS in Particulate Matters Emitted from Residential Coal and Biomass Combustion

Abstract

Identification of humic-like substances (HULIS) structures and components is still a major challenge owing to their chemical complexity. This study first employed a complementary method with the combination of two-dimensional gas chromatography–time-of-flight mass spectrometry and liquid chromatography–quadrupole-time-of-flight mass spectrometry to address low-polarity and polar components of HULIS in PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 μm), respectively. The combination method showed a significant correlation in identifying overlapping species and performed well in uncovering the chemical complexity of HULIS. A total of 1246 compound species in HULIS (65.6–81.0% for each sample), approximately 1 order of magnitude more compounds than that reported in previous studies, were addressed in PM2.5 collected in real-world household biomass and coal combustion. Aromatics were the most abundant compounds (37.4–64.1% in biomass and 34.5–70.0% in coal samples) of the total mass in all HULIS samples according to carbon skeleton determination, while the major components included phenols (2.6–21.1%), ketones (6.0–17.1%), aldehydes (1.1–6.8%), esters (2.9–20.0%), amines/amides (3.2–8.5%), alcohols (3.8–17.0%), and acids (4.7–15.1%). Among the identified HULIS species, 11–36% mass in biomass and 11–41% in coal were chromophores, while another 22–35 and 23–29% mass were chromophore precursors, respectively. The combination method shows promise for uncovering HULIS fingerprinting.

Addressing Unresolved Complex Mixture of I/SVOCs Emitted From Incomplete Combustion of Solid Fuels by Nontarget Analysis

“…The standard deviation (±) was applied as the uncertainty of the average value of the organic mass or proportion for parallel samples. The values beyond the decimal point are supported by a good detection limit in the analytical instruments (Huo et al., 2021)…”

“…Blank samples were analyzed with the same method, and their signals were deducted from those of the actual samples. The operating conditions for analyses were detailed in our previous study (Huo et al, 2021). The setting parameters of GC and TOF−MS are detailed in Table S2, while original chromatograms are shown in Figures S2 and S3 with original data included in supporting data (SD).…”

“…The standard deviation (±) was applied as the uncertainty of the average value of the organic mass or proportion for parallel samples. The values beyond the decimal point are supported by a good detection limit in the analytical instruments (Huo et al, 2021) When the volatility distribution was binned on the basis of retention times of n-alkanes, the quantifications of speciated I/SVOCs and UCM were also determined (Zhao et al, 2014). The total ion chromatogram of each sample was separated into B 8 -B 34 roughly equal width retention time bins.…”

“…The total numbers of I/SVOCs compounds identified were 601-633, 401-505, and 373-393 for corncob, wood, and coal samples, respectively, as detailed in SD. These identified compounds were divided into three categories (i.e., aromatics, aliphatics, and alicyclics) based on their carbon skeletons and 20 subcategories (i.e., phenols, ketones, PAHs, benzenes, aldehydes, O-heterocycles, N-heterocycles, indenes, alcohols, alkanes, alkenes, alkynes, acids, esters, amides, amines, nitriles, ethers, carbohydrates, and hydrocarbons) according to their functional groups (see Figures 3a, S8a and S9a, detailed in SD) (Huo et al, 2021). As an example, compounds containing benzene rings, open chains, and nonaromatic rings were classified as aromatic, aliphatic, and alicyclic, respectively.…”

Ocean Aerobiology

“…HULIS are produced by marine ecosystems (Stedmon and Markager, 2005;Murphy et al, 2008) or are transported into the ocean from terrestrial sources by rivers (Hedges et al, 1992;Huguet et al, 2009;Krachler and Krachler, 2021). The relative contributions of HULIS in marine aerosol from marine ecosystem processes, terrestrial ecosystems, and anthropogenic sources (e.g., combustion of coal and biomass; Huo et al, 2021) is uncertain. Much remains to be learned about the molecular diversity of primary marine aerosol and how it relates to processes in the underlying water.…”