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

Abstract

The major fraction of intermediate and semi‐volatility organic compounds (I/SVOCs) is still unresolved by traditional analyses, leaving large unresolved complex mixture (UCM) and limiting the estimation of secondary organic aerosol (SOA). This study addressed the UCM by employing two‐dimensional gas chromatography−time‐of‐flight mass spectrometry. The ratios of UCM in I/SVOCs emitted from household burning of biomass and coal were reduced to 1.0 ± 0.3% and 2.1 ± 2.0%, respectively, and these levels are one order of magnitude less than those reported in previous studies. Phenols, polycyclic aromatic hydrocarbons, and ketones made the major contribution to I/SVOCs emission factors (EFs) (65.9 ± 9.6%) for biomass burning, while amides, acids, and esters constituted the majority of EFs (56.5 ± 45.0%) for coal burning. Furthermore, SOA production can be predicted via the highly identified I/SVOCs compounds based on volatility distributions of each speciated species. These majority compounds contribute the predicted SOA production with 76.0 ± 12.7% and 82.0 ± 60.3% for biomass and coal burning, respectively. Underestimated SOA production with the ratio of 62.5 ± 25.2% to 80.9 ± 2.8% via previous Bins method has been well addressed. The obtained results suggest that the nontarget analysis can significantly improve the accuracy of I/SVOCs estimation and environmental impacts by addressing chemical components at the molecular level.

Dynamic Evolution and Covariant Response Mechanism of Volatile Organic Compounds and Residual Functional Groups during the Online Pyrolysis of Coal and Biomass Fuels

“…20,28,63,64 The complicated nature of CBF−VOC classes was consistent with those of intermediate-/semi-VOCs and PAHs emitted from residential solid fuel combustion. 6,65,66 Molecular formulas of CBF−VOCs were divided into six categories (Figure 1a). CH/CHO compounds of CBF showed the maximum proportions (51.3−72.9%), consistent with those from reported corncob/briquette/anthracite/tobacco combustion (63.6−87.5%).…”

“…The volatility distribution of identified VOCs covered the log 10 C 0 range of approximately −1 to 10 μg•m −3 , belonging to volatile, intermediate-volatile and semi-volatile regions (Figure 2a). As shown in Table S3, the relative CBF−VOC percentages (48.4−71.9%) were higher than those from coal/wood/corncob (1.3−29.8%) 66 and gasoline/diesel (25.9−26.9%) sources 70 and were similar to those of gas-turbine engine (50.5−57.3%) 70 and gasoline vehicle (66 ± 27%) emissions. 25 The relative CBF− intermediate-VOC percentages (28.1−45.2%) were comparable with those (26−31%) from bituminous coal combustion 1 and were lower than those from wood/corncob (64.2− 68.6%) 66 and gasoline/diesel (25.9−26.9%) sources.…”

“…As shown in Table S3, the relative CBF−VOC percentages (48.4−71.9%) were higher than those from coal/wood/corncob (1.3−29.8%) 66 and gasoline/diesel (25.9−26.9%) sources 70 and were similar to those of gas-turbine engine (50.5−57.3%) 70 and gasoline vehicle (66 ± 27%) emissions. 25 The relative CBF− intermediate-VOC percentages (28.1−45.2%) were comparable with those (26−31%) from bituminous coal combustion 1 and were lower than those from wood/corncob (64.2− 68.6%) 66 and gasoline/diesel (25.9−26.9%) sources. 70 Huo et al reported that intermediate-VOC and semi-VOC percentages in the total emissions from bituminous coal and wood combustion were 37.2 and 5.9%, respectively, which were comparable to the relative percentages of SBCintermediate-VOC (44.7−45.2%) and WP−semi-VOC (8.3− 22.6%).…”

“…65 Furthermore, for average percentages of CBF−VOC classes (Figure 1b), aldehydes/ ketones/acids (30−42%) were predominant and were similar to aldehydes/ketones/acids percentages (26.8−36.9%) in intermediate-/semi-VOCs from coal/wood/corncob combustion (Table S3). 66 The reported PAH percentage (16.5− 18.6%) in the intermediate-VOCs from solid fuel combustion was within the percentage range of CBF-aromatics (16−32%). 6 Alcohols/phenols/ethers/esters percentages (9−28%) from CBF pyrolysis were lower than those (33.4−34.3%) in offlinemeasured intermediate-semi-VOCs from coal/wood/corncob combustion, 66 indicating that alcohols/phenols/ethers/esters were susceptible to the apparent difference between online and offline measurements.…”

“…66 The reported PAH percentage (16.5− 18.6%) in the intermediate-VOCs from solid fuel combustion was within the percentage range of CBF-aromatics (16−32%). 6 Alcohols/phenols/ethers/esters percentages (9−28%) from CBF pyrolysis were lower than those (33.4−34.3%) in offlinemeasured intermediate-semi-VOCs from coal/wood/corncob combustion, 66 indicating that alcohols/phenols/ethers/esters were susceptible to the apparent difference between online and offline measurements.…”