Abstract. It is being suggested that particle-bound or particle-induced
reactive oxygen species (ROS), which significantly contribute to the
oxidative potential (OP) of aerosol particles, are a promising metric
linking aerosol compositions to toxicity and adverse health effects.
However, accurate ROS quantification remains challenging due to the reactive
and short-lived nature of many ROS components and the lack of appropriate
analytical methods for a reliable quantification. Consequently, it remains
difficult to gauge their impact on human health, especially to identify how
aerosol particle sources and atmospheric processes drive particle-bound ROS
formation in a real-world urban environment. In this study, using a novel online particle-bound ROS instrument (OPROSI),
we comprehensively characterized and compared the formation of ROS in
secondary organic aerosols (SOAs) generated from organic compounds that
represent anthropogenic (naphthalene, SOANAP) and biogenic (β-pinene, SOAβPIN) precursors. The SOA mass was condensed onto
soot particles (SP) under varied atmospherically relevant conditions
(photochemical aging and humidity) to mimic the SOA formation from a mixing
of traffic-related carbonaceous primary aerosols and volatile organic compounds (VOCs). We systematically
analyzed the ability of the aqueous extracts of the two aerosol types
(SOANAP-SP and SOAβPIN-SP) to induce ROS production
and OP. We further investigated cytotoxicity and cellular ROS production
after exposing human lung epithelial cell cultures (A549) to extracts of the
two aerosols. A significant finding of this study is that more than 90 %
of all ROS components in both SOA types have a short lifetime, highlighting
the need to develop online instruments for a meaningful quantification of
ROS. Our results also show that photochemical aging promotes particle-bound
ROS production and enhances the OP of the aerosols. Compared to SOAβPIN-SP, SOANAP-SP elicited a higher acellular and cellular ROS
production, a higher OP, and a lower cell viability. These consistent results
between chemical-based and biological-based analyses indicate that
particle-bound ROS quantification could be a feasible metric to predict
aerosol particle toxicity and adverse human effects. Moreover, the cellular
ROS production caused by SOA exposure not only depends on aerosol type but
is also affected by exposure dose, highlighting a need to mimic the process
of particle deposition onto lung cells and their interactions as
realistically as possible to avoid unknown biases.
Magnesium and calcium chloride salts contribute to the global atmospheric aerosol burden via emission of sea spray and mineral dust. Their influence on aerosol hygroscopicity and cloud forming potential is...
Abstract. It is being suggested that particle-bound or particle-induced reactive oxygen species (ROS), which significantly contribute to the oxidative potential (OP) of aerosol particles, are a promising metric linking aerosol compositions to toxicity and adverse health effects. However, accurate ROS quantification remains challenging due to the reactive and short-lived nature of many ROS components and the lack of appropriate analytical methods for a reliable quantification. Consequently, it remains difficult to gauge their impact on human health, especially to identify how aerosol particle sources and atmospheric processes drive particle-bound ROS formation in a real-world urban environment. In this study, using a novel online particle-bound ROS instrument (OPROSI), we comprehensively characterized and compared the formation of ROS in secondary organic aerosols (SOA) generated from organic compounds that represent anthropogenic (naphthalene, SOANAP) and biogenic (β-pinene, SOAβPIN) precursors. The SOA mass was condensed onto soot particles (SP) under varied atmospherically relevant conditions (photochemical aging and humidity). We systematically analysed the ability of the aqueous extracts of the two aerosol types (SOANAP-SP and SOAβPIN-SP) to induce ROS production and OP. We further investigated cytotoxicity and cellular ROS production after exposing human lung epithelial cell cultures (A549) to extracts of the two aerosols. A significant finding of this study is that more than 90 % of all ROS components in both SOA types have a short lifetime, highlighting the need to develop online instruments for a meaningful quantification of ROS. Our results also show that photochemical aging promotes particle-bound ROS production and enhances the OP of the aerosols. Compared to SOAβPIN-SP, SOANAP-SP elicited a higher acellular and cellular ROS production, a higher OP and a lower cell viability. These consistent results between chemical-based and biological-based analyses indicate that particle-bound ROS quantification could be a feasible metric to predict aerosol particle toxicity and adverse human effects. Moreover, the cellular ROS production caused by SOA exposure not only depends on aerosol type, but is also affected by exposure dose, highlighting a need to mimic the process of particle deposition onto lung cells and their interactions as realistically as possible to avoid unknown biases.
The atmospheric aging of volatile
organic compounds leads to the
formation of complex mixtures of highly oxidized secondary organic
aerosols (SOAs). State-of-the-art mass spectrometry (MS) has become
a pivotal tool for their chemical characterization. In this study,
we characterized the chemical complexity of naphthalene-derived SOA
by three different time-of-flight (TOF) mass spectrometric techniques
applying electron ionization: high-resolution–TOF–aerosol
MS (AMS), direct inlet probe (DIP)–high-resolution TOFMS, and
thermal desorptioncomprehensive two-dimensional gas chromatographyTOFMS
(GC × GC). We discuss AMS as an online, DIP as an atline, and
GC × GC as an offline technique to compare their informative
value for studying the oxidation state, volatility, and molecular
composition of laboratory-generated SOA. For GC × GC, the accessible
organic content was limited to (semi-)volatile compounds and supported
a reliable assignment of the molecular composition. DIP and AMS were
used to derive secondary parameters such as O/C and H/C ratios, the
general functionality of the compound classes and their abundance
upon photochemical aging. Thereby, while the induced pyrolysis in
the AMS extended the accessibility range to polar, high-molecular-weight
compounds, thermal fragmentation also led to limited molecular information.
For DIP, low-volatility compounds could be volatilized and the high
mass resolution was useful to resolve isobaric mass fragments and
assign reliable sum formulas of fragments and molecular ions. Although
no single technique can provide information to describe the full chemical
complexity of the SOA, AMS, DIP, and GC × GC in their complementarity
are well suited to investigate the impact of SOA on health and environment.
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