Ambient air pollution is one of the leading five health risks worldwide. One of the most harmful air pollutants is particulate matter (PM), which has different physical characteristics (particle size ...and number, surface area and morphology) and a highly complex and variable chemical composition. Our goal was first to comparatively assess the effects of exposure to PM regarding cytotoxicity, release of pro-inflammatory mediators and gene expression in human bronchial epithelia (HBE) reflecting normal and compromised health status. Second, we aimed at evaluating the impact of various PM components from anthropogenic and biogenic sources on the cellular responses. Air-liquid interface (ALI) cultures of fully differentiated HBE derived from normal and cystic fibrosis (CF) donor lungs were exposed at the apical cell surface to water-soluble PM filter extracts for 4 h. The particle dose deposited on cells was 0.9-2.5 and 8.8-25.4 μg per cm2 of cell culture area for low and high PM doses, respectively. Both normal and CF HBE show a clear dose-response relationship with increasing cytotoxicity at higher PM concentrations. The concurrently enhanced release of pro-inflammatory mediators at higher PM exposure levels links cytotoxicity to inflammatory processes. Further, the PM exposure deregulates genes involved in oxidative stress and inflammatory pathways leading to an imbalance of the antioxidant system. Moreover, we identify compromised defense against PM in CF epithelia promoting exacerbation and aggravation of disease. We also demonstrate that the adverse health outcome induced by PM exposure in normal and particularly in susceptible bronchial epithelia is magnified by anthropogenic PM components. Thus, including health-relevant PM components in regulatory guidelines will result in substantial human health benefits and improve protection of the vulnerable population.
Reactive oxygen species (ROS) are believed to contribute
to the adverse health effects of aerosols. This may happen by inhaled
particle-bound (exogenic) ROS (PB-ROS) or by ROS formed within the
...respiratory tract by certain aerosol components (endogenic ROS). We
investigated the chemical composition of aerosols and their exogenic ROS
content at the two contrasting locations Beijing (China) and Bern
(Switzerland). We apportioned the ambient organic aerosol to different
sources and attributed the observed water-soluble PB-ROS to them. The
oxygenated organic aerosol (OOA, a proxy for secondary organic aerosol, SOA)
explained the highest fraction of the exogenic ROS concentration variance at
both locations. We also characterized primary and secondary aerosol
emissions generated from different biogenic and anthropogenic sources in
smog chamber experiments. The exogenic PB-ROS content in the OOA from these
emission sources was comparable to that in the ambient measurements. Our
results imply that SOA from gaseous precursors of different anthropogenic
emission sources is a crucial source of water-soluble PB-ROS and should be
additionally considered in toxicological and epidemiological studies in an
adequate way besides primary emissions. The importance of PB-ROS may be
connected to the seasonal trends in health effects of PM reported by
epidemiological studies, with elevated incidences of adverse effects in
warmer seasons, which are accompanied by more-intense atmospheric oxidation
processes.
Organic aerosols are a major fraction, often more than 50%, of the total atmospheric aerosol mass. The chemical composition of the total organic aerosol mass is poorly understood, although hundreds ...of compounds have been identified in the literature. High molecular weight compounds have recently gained much attention because this class of compounds potentially represents a major fraction of the unexplained organic aerosol mass. Here we analyze secondary organic aerosols, generated in a smog chamber from α-pinene ozonolysis with ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). About 450 compounds are detected in the mass range of m/z 200−700. The mass spectrum is clearly divided into a low molecular weight range (monomer) and a high molecular weight range, where dimers and trimers are distinguishable. Using the Kendrick mass analysis, the elemental composition of about 60% of all peaks could be determined throughout the whole mass range. Most compounds have high O:C ratios between 0.4 and 0.6. Small compounds (i.e., monomers) have a higher maximum O:C ratio than dimers and trimers, suggesting that condensation reactions with, for example, the loss of water are important in the oligomer formation process. A program developed in-house was used to determine exact mass differences between peaks in the monomer, dimer, and trimer mass range to identify potential monomer building blocks, which form the co-oligomers observed in the mass spectrum. A majority of the peaks measured in the low mass region of the spectrum (m/z < 300) is also found in the calculated results. For the first time the elemental composition of the majority of peaks over a wide mass range was determined using advanced data analysis methods for the analysis of ultra-high-resolution MS data. Possible oligomer formation mechanisms in secondary organic aerosols were investigated.
In early spring the Baltic region is frequently affected by high-pollution events due to biomass burning in that area. Here we present a comprehensive study to investigate the impact of biomass/grass ...burning (BB) on the evolution and composition of aerosol in Preila, Lithuania, during springtime open fires. Non-refractory submicron particulate matter (NR-PM1) was measured by an Aerodyne aerosol chemical speciation monitor (ACSM) and a source apportionment with the multilinear engine (ME-2) running the positive matrix factorization (PMF) model was applied to the organic aerosol fraction to investigate the impact of biomass/grass burning. Satellite observations over regions of biomass burning activity supported the results and identification of air mass transport to the area of investigation. Sharp increases in biomass burning tracers, such as levoglucosan up to 683 ng m−3 and black carbon (BC) up to 17 µg m−3 were observed during this period. A further separation between fossil and non-fossil primary and secondary contributions was obtained by coupling ACSM PMF results and radiocarbon (14C) measurements of the elemental (EC) and organic (OC) carbon fractions. Non-fossil organic carbon (OCnf) was the dominant fraction of PM1, with the primary (POCnf) and secondary (SOCnf) fractions contributing 26–44 % and 13–23 % to the total carbon (TC), respectively. 5–8 % of the TC had a primary fossil origin (POCf), whereas the contribution of fossil secondary organic carbon (SOCf) was 4–13 %. Non-fossil EC (ECnf) and fossil EC (ECf) ranged from 13–24 and 7–13 %, respectively. Isotope ratios of stable carbon and nitrogen isotopes were used to distinguish aerosol particles associated with solid and liquid fossil fuel burning.
Inhalation of atmospheric particles is linked to human diseases. Reactive oxygen species (ROS) present in these atmospheric aerosols may play an important role. However, the ROS content in aerosols ...and their formation pathways are still largely unknown. Here, we have developed an online and offline ROS analyzer using a 2′,7′-dichlorofluorescin (DCFH) based assay. The ROS analyzer was calibrated with H2O2 and its sensitivity was characterized using a suite of model organic compounds. The instrument detection limit determined as 3 times the noise is 1.3 nmol L−1 for offline analysis and 2 nmol m−3 of sampled air when the instrument is operated online at a fluorescence response time of approximately 8 min, while the offline method detection limit is 18 nmol L−1. Potential interferences from gas-phase O3 and NO2 as well as matrix effects of particulate SO42− and NO3− were tested, but not observed. Fe3+ had no influence on the ROS signal, while soluble Fe2+ reduced it if present at high concentrations in the extracts. Both online and offline methods were applied to identify the ROS content of different aerosol types, i.e., ambient aerosols as well as fresh and aged aerosols from wood combustion emissions. The stability of the ROS was assessed by comparing the ROS concentration measured by the same instrumentation online in situ with offline measurements. We also analyzed the evolution of ROS in specific samples by conducting the analysis after storage times of up to 4 months. The ROS were observed to decay with increasing storage duration. From their decay behavior, ROS in secondary organic aerosol (SOA) can be separated into short- and long-lived fractions. The half-life of the short-lived fraction was 1.7 ± 0.4 h, while the half-life of the long-lived fraction could not be determined with our uncertainties. All these measurements showed consistently that on average 60 ± 20 % of the ROS were very reactive and disappeared during the filter storage time. This demonstrates the importance of a fast online measurement of ROS.
Aerosols still present the largest uncertainty in estimating anthropogenic radiative forcing. Cloud processing is potentially important for secondary organic aerosol (SOA) formation, a major aerosol ...component: however, laboratory experiments fail to mimic this process under atmospherically relevant conditions. We developed a wetted-wall flow reactor to simulate aqueous-phase processing of isoprene oxidation products (iOP) in cloud droplets. We find that 50 to 70% (in moles) of iOP partition into the aqueous cloud phase, where they rapidly react with OH radicals, producing SOA with a molar yield of 0.45 after cloud droplet evaporation. Integrating our experimental results into a global model, we show that clouds effectively boost the amount of SOA. We conclude that, on a global scale, cloud processing of iOP produces 6.9 Tg of SOA per year or approximately 20% of the total biogenic SOA burden and is the main source of SOA in the mid-troposphere (4 to 6 km).
Stable carbon isotope ratio (
δ
13C) data can provide important information regarding the sources and the processing of atmospheric organic carbon species. Formic, acetic and oxalic acid were ...collected from Zurich city in August–September 2002 and March 2003 in the gas and aerosol phase, and the corresponding
δ
13C analysis was performed using a wet oxidation method followed by isotope ratio mass spectrometry. In August, the
δ
13C values of gas phase formic acid showed a significant correlation with ozone (coefficient of determination (
r
2)
=
0.63) due to the kinetic isotope effect (KIE). This indicates the presence of secondary sources (i.e. production of organic acids in the atmosphere) in addition to direct emission. In March, both gaseous formic and acetic acid exhibited similar
δ
13C values and did not show any correlation with ozone, indicating a predominantly primary origin. Even though oxalic acid is mainly produced by secondary processes, the
δ
13C value of particulate oxalic acid was not depleted and did not show any correlation with ozone, which may be due to the enrichment of
13C during the gas - aerosol partitioning.
The concentrations and
δ
13C values of the different aerosol fractions (water soluble organic carbon, water insoluble organic carbon, carbonate and black carbon) collected during the same period were also determined. Water soluble organic carbon (WSOC) contributed about 60% to the total carbon and was enriched in
13C compared to other fractions indicating a possible effect of gas - aerosol partitioning on
δ
13C of carbonaceous aerosols. The carbonate fraction in general was very low (3% of the total carbon).
A new environmental reaction smog chamber was built to simulate particle formation and growth similar to that expected in the atmosphere. The organic material is formed from nucleation of ...photooxidized organic compounds. The chamber is a 27 m3 fluorinated ethylene propylene (FEP) bag suspended in a temperature-controlled enclosure. Four xenon arc lamps (16 kW total) are used to irradiate primary gas components for experiments lasting up to 24 h. Experiments using irradiations of 1,3,5-trimethylbenzene-NOx-H2O at similar input concentrations without seed particles were used to determine particle number and volume concentration wall loss rates of 0.209+/-0.018 and 0.139+/-0.070 h(-1), respectively. The particle formation was compared with and without propene.
Isoprene, a compound emitted by vegetation, could be a major contributor to secondary organic aerosols (SOA) in the atmosphere. The main evidence for this contribution were the ...2‐methylbutane‐1,2,3,4‐tetraols, or 2‐methyltetrols (2‐methylerythritol and 2‐methylthreitol) present in ambient aerosols. In this work, the four stereoisomers of these tetraols were analyzed in aerosols from Aspvreten, Sweden. 2‐C‐methyl‐D‐erythritol was found in excess over its enantiomer in the Spring/Summer, by up to 29% in July. This clearly indicated some biological origins for this enantiomer, consistent with its well‐documented production by plants and other living organisms. In addition, a minimum of 20 to 60% of the mass of racemic tetraols appeared from biological origin. Thus, the SOA mass produced by isoprene in the atmosphere is less than what indicated by the 2‐methyltetrols in aerosols. Our results also demonstrate that stereochemical speciation can distinguish primary and secondary organic material in atmospheric aerosols.
Key Points
The first method distinguishing 1ary and 2ary organics in aerosols is proposed
This method shows that the 2‐methyltetrols in some aerosols are biological
The main evidence for isoprene contribution to atmospheric SOA is invalidated
We report the first measurements of HO2 uptake coefficients, γ, for secondary organic aerosol (SOA) particles and for the well-studied model compound sucrose which we doped with copper(II). Above ...65 % relative humidity (RH), γ for copper(II)-doped sucrose aerosol particles equalled the surface mass accommodation coefficient α = 0.22 ± 0.06, but it decreased to γ = 0.012 ± 0.007 upon decreasing the RH to 17 %. The trend of γ with RH can be explained by an increase in aerosol viscosity and the contribution of a surface reaction, as demonstrated using the kinetic multilayer model of aerosol surface and bulk chemistry (KM-SUB). At high RH the total uptake was driven by reaction in the near-surface bulk and limited by mass accommodation, whilst at low RH it was limited by surface reaction. SOA from two different precursors, α-pinene and 1,3,5-trimethylbenzene (TMB), was investigated, yielding low uptake coefficients of γ < 0.001 and γ = 0.004 ± 0.002, respectively. It is postulated that the larger values measured for TMB-derived SOA compared to α-pinene-derived SOA are either due to differing viscosity, a different liquid water content of the aerosol particles, or an HO2 + RO2 reaction occurring within the aerosol particles.
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