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Wildfires, which have been occurring increasingly in the era of climate change, emit massive amounts of particulate matter (PM) into the atmosphere, strongly affecting air quality and public health. Biomass burning aerosols may contain environmentally persistent free radicals (EPFRs, such as semiquinone radicals) and redox-active compounds that can generate reactive oxygen species (ROS, including ·OH, superoxide and organic radicals) in the aqueous phase. However, there is a lack of data on EPFRs and ROS associated with size-segregated wildfire PM, which limits our understanding of their climate and health impacts. We collected size-segregated ambient PM in Southern California during two wildfire events to measure EPFRs and ROS using electron paramagnetic resonance spectroscopy. EPFRs are likely associated with soot particles as they are predominantly observed in submicron particles (PM 1 , aerodynamic diameter ≤ 1 μm). Upon extraction in water, wildfire PM mainly generates ·OH (28–49%) and carbon-centered radicals (∼50%) with minor contributions from superoxide and oxygen-centered organic radicals (2–15%). Oxidative potential measured with the dithiothreitol assay (OP-DTT) is found to be high in wildfire PM 1 , exhibiting little correlation with the radical forms of ROS ( r 2 ≤ 0.02). These results are in stark contrast with PM collected at highway and urban sites, which generates predominantly ·OH (84–88%) that correlates well with OP-DTT ( r 2 ∼ 0.6). We also found that PM generated by flaming combustion generates more radicals with higher OP-DTT compared to those by smoldering or pyrolysis.
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A semi-automated instrument for cellular oxidative potential evaluation (SCOPE) of water-soluble extracts of ambient particulate matter
Abstract. Several automated instruments exist to measure the acellularoxidative potential (OP) of ambient particulate matter (PM). However,cellular OP of the ambient PM is still measured manually, which severelylimits the comparison between two types of assays. Cellular assays couldprovide a more comprehensive assessment of the PM-induced oxidative stress,as they incorporate more biological processes involved in the PM-catalyzedreactive oxygen species (ROS) generation. Considering this need, wedeveloped a semi-automated instrument, the first of its kind, for measuring thecellular OP based on a macrophage ROS assay using rat alveolar macrophages.The instrument named SCOPE – semi-automated instrument for cellularoxidative potential evaluation – uses dichlorofluorescein diacetate (DCFH-DA)as a probe to detect the OP of PM samples extracted in water. SCOPE iscapable of analyzing a batch of six samples (including one negative and onepositive control) in 5 h and is equipped to operate continuously for24 h with minimal manual intervention after every batch of analysis,i.e., after every 5 h. SCOPE has a high analytical precision asassessed from both positive controls and ambient PM samples (coefficient of variation (CoV)<17 %). The results obtained from the instrument were in good agreementwith manual measurements using tert-butyl hydroperoxide (t-BOOH) as thepositive control (slope =0.83 for automated vs. manual, R2=0.99)and ambient samples (slope =0.83, R2=0.71). We furtherdemonstrated the ability of SCOPE to analyze a large number of both ambientand laboratory samples and developed a dataset on the intrinsic cellular OPof several compounds, such as metals, quinones, polycyclic aromatichydrocarbons (PAHs) and inorganic salts, commonly known to be present inambient PM. This dataset is potentially useful in future studies toapportion the contribution of key chemical species in the overall cellularOP of ambient PM.
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- Award ID(s):
- 1847237
- PAR ID:
- 10326658
- Date Published:
- Journal Name:
- Atmospheric Measurement Techniques
- Volume:
- 14
- Issue:
- 12
- ISSN:
- 1867-8548
- Page Range / eLocation ID:
- 7579 to 7593
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/amt-14-7579-2021
