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Chemical composition, structures, and light absorption of N-containing aromatic compounds emitted from burning wood and charcoal in household cookstoves.

ABSTRACT: N-containing aromatic compounds (NACs) are an important group of light-absorbing molecules in the atmosphere. They are often observed in combustion emissions, but their chemical formulas and structural characteristics remain uncertain. In this study, red oak wood and charcoal fuels were burned in cookstoves using the standard water boiling test (WBT) procedure. Submicron aerosol particles in the cookstove emissions were collected using quartz (Q _f ) and polytetrafluoroethylene (PTFE) filter membranes positioned in parallel. A back-up quartz filter (Q _b ) was also installed downstream of the PTFE filter to evaluate the effect of sampling artifact on NACs measurements. Liquid chromatography-mass spectroscopy (LC-MS) techniques identified seventeen NAC chemical formulas in the cookstove emissions. The average concentrations of total NACs in Q _b samples (0.37 ± 0.31 - 1.79 ± 0.77 μg m^-3) were greater than 50% of those observed in the Q _f samples (0.51 ± 0.43 - 3.91 ± 2.06 μg m^-3), and the Q _b to Q _f mass ratios of individual NACs had a range of 0.02 - 2.71, indicating that the identified NACs might have substantial fractions remaining in the gas-phase. In comparison to other sources, cookstove emissions from red oak or charcoal fuels did not exhibit unique NAC structural features, but had distinct NACs composition. However, before identifying NACs sources by combining their structural and compositional information, the gas-particle partitioning behaviors of NACs should be further investigated. The average contributions of total NACs to the light absorption of organic matter at λ = 365 nm (1.10 - 2.57%) in Q _f and Q _b samples (10.7 - 21.0%) are up to 10 times larger than their mass contributions (Q _f 0.31 - 1.01%, Q _b 1.08 - 3.31%), so the identified NACs are mostly strong light absorbers. To explain more sample extracts absorption, future research is needed to understand the chemical and optical properties of high molecular weight (e.g., MW > 500 Da) entities in particulate matter.

SUBMITTER: Xie M

PROVIDER: S-EPMC7863623 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:This study seeks to understand the compositional details of N-containing aromatic compounds (NACs) emitted during biomass burning (BB) and their contribution to light-absorbing organic carbon (OC), also termed brown carbon (BrC). Three laboratory BB experiments were conducted with two U.S. pine forest understory fuels typical of those consumed during prescribed fires. During the experiments, submicron aerosol particles were collected on filter media and subsequently extracted with methanol and examined for their optical and chemical properties. Significant correlations (p < 0.05) were observed between BrC absorption and elemental carbon (EC)/OC ratios for individual burns data. However, the pooled experimental data indicated that the BB BrC absorption depends on more than the BB fire conditions as represented by the EC/OC ratio. Fourteen NAC formulas were identified in the BB samples, most of which were also observed in simulated secondary organic aerosol (SOA) from photo-oxidation of aromatic VOCs with NOX. However, the molecular structures associated with the identical NAC formula from BB and SOA are different. In this work, the identified NACs from BB are featured by methoxy and cyanate groups, and are predominately generated during the flaming phase. The mass concentrations of identified NACs were quantified using authentic and surrogate standards, and their contributions to bulk light absorption of solvent extractable OC were also calculated. The contributions of identified NACs to organic matter (OM) and BrC absorption were significantly higher in flaming-phase samples than those in smoldering-phase samples, and correlated with EC/OC ratio (p < 0.05) for both individual burns and pooled experimental data, indicating that the formation of NACs from BB largely depends on burn conditions. The average contributions of identified NACs to overall BrC absorption at 365 nm ranged from 0.087 ± 0.024 to 1.22 ± 0.54%, 3 - 10 times higher than their mass contributions to OM (0.023 ± 0.0089 to 0.18 ± 0.067%), so the NACs with light absorption identified in this work from BB are likely strong BrC chromophores. Further studies are warranted to identify more light-absorbing compounds to explain the unknown fraction (> 98%) of BB BrC absorption.

Project description:BACKGROUND:Household air pollution from cooking with solid fuels affects nearly 3 billion people worldwide and is responsible for an estimated 2.5 million premature deaths and 77 million disability-adjusted life years annually. Investigating the effect of household air pollution on indicators of cardiometabolic disease, such as metabolic syndrome, can help clarify the pathways between this widespread exposure and cardiovascular diseases, which are increasing in low- and middle-income countries. METHODS:Our cross-sectional study of 150 women in rural Honduras (76 with traditional stoves and 74 with cleaner-burning Justa stoves) explored the effect of household air pollution exposure on cardiovascular disease risk factors. Household air pollution was measured by stove type and 24-h average kitchen and personal fine particulate matter [PM2.5] mass and black carbon concentrations. Health endpoints included non-fasting total cholesterol, high-density lipoprotein, calculated low-density lipoprotein, triglycerides, waist circumference to indicate abdominal obesity, and presence of metabolic syndrome (defined by current modified international guidelines: waist circumference???80?cm plus any two of the following: triglycerides?>?200?mg/dL, HDL?<?50?mg/dL, systolic blood pressure???130?mmHg, diastolic blood pressure???85?mmHg, or glycated hemoglobin?>?5.6%). RESULTS:Forty percent of women met the criteria for metabolic syndrome. The prevalence ratio [PR] for metabolic syndrome (versus normal) per interquartile range increase in kitchen PM2.5 and kitchen black carbon was 1.16 (95% confidence interval [CI]: 1.01-1.34) per 312??g/m3 increase in PM2.5, and 1.07 (95% CI: 1.03-1.12) per 73??g/m3 increase in black carbon. There is suggestive evidence of a stronger effect in women ??40 years of age compared to women <?40 (p-value for interaction?=?0.12 for personal PM2.5). There was no evidence of associations between all other exposure metrics and health endpoints. CONCLUSIONS:The prevalence of metabolic syndrome among our study population was high compared to global estimates. We observed a suggestive effect between metabolic syndrome and exposure to household air pollution. These results for metabolic syndrome may be driven by specific syndrome components, such as blood pressure. Longitudinal research with repeated health and exposure measures is needed to better understand the link between household air pollution and indicators of cardiometabolic disease risk.

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Chemical composition, structures, and light absorption of N-containing aromatic compounds emitted from burning wood and charcoal in household cookstoves.

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