Oxidative potential of atmospheric aerosols

Atmospheric particulate matter (PM) is one of the leading health risks worldwide [1,2]. Several epidemiological studies have provided evidence of the association between exposure to PM and the onset of cardiovascular and respiratory diseases [3], as well as cardiopulmonary diseases and other adverse health effects [4]. The exact mechanisms leading to PM toxicity are not fully known, however, several studies suggest that the generation of reactive oxygen species (ROS) could be a major mechanism by which PM leads to both chronic and acute adverse health effects [5,6]. For this reason, in recent years, the oxidative potential (OP) of PM, defined as its ability to generate oxidative stress in biological systems, has been proposed as a relevant metric for addressing PM exposure [7,8]. However, the link between OP and adverse health effects is still uncertain [9–11], and contrasting results have been obtained when PM oxidative potential has been compared with the results of in-vivo and in-vitro toxicological tests or the outcomes of epidemiological studies [12]. The OP can be evaluated through several in vitro assays, but protocols employing chemical (acellular) assays have become common as well. Acellular assays can be useful for investigating the PM properties which are responsible for oxidative stress: ROS compounds can either be carried by components of the aerosol itself (particle-bound ROS) or induced by the catalytic activity exerted by aerosol constituents (PM-induced ROS). The diverse OP assays developed so far have certainly improved our knowledge of the mechanisms underlying PM oxidative stress. At the same time, they pose the issue of comparability between the different assays and protocols, as well as problems surrounding the actual correlation between acellular OP and in vitro (or in vivo) toxicity. Measurements of PM oxidative potential are influenced by the chemical composition of the aerosol, by its size distribution, and by the weight of different natural and anthropogenic sources of PM leading to temporal and spatial variabilities that need investigation in current research. Moreover, recent studies show that photochemical aging increases the oxidative potential of atmospheric aerosols. However, several aspects regarding the specific chemical species, aerosol sources, and atmospheric processes that affect OP are not well established, and further research is needed [13–15]. Another topic that needs extensive research is the characterization of the OP of indoor aerosols. This special issue includes five research papers and two review papers discussing recent advances in the studies of the oxidative potential of atmospheric particulate matter

Size-segregated aerosol chemical composition at a boreal site in southern Finland, during the QUEST project

International audienceSize-segregated aerosol samples were collected during the QUEST field campaign at Hyytiälä, a boreal forest site in Southern Finland, during spring 2003. Aerosol samples were selectively collected during both particle formation events and periods in which no particle formation occurred. A comprehensive characterisation of the aerosol chemical properties (water-soluble inorganic and organic fraction) and an analysis of the relevant meteorological parameters revealed how aerosol chemistry and meteorology combine to determine a favorable "environment" for new particle formation. The results indicated that all events, typically favored during northerly air mass advection, were background aerosols (total mass concentrations range between 1.97 and 4.31 µg m-3), with an increasingly pronounced marine character as the northerly air flow arrived progressively from the west and, in contrast, with a moderate SO2-pollution influence as the air arrived from more easterly directions. Conversely, the non-event aerosol, transported from the south, exhibited the chemical features of European continental sites, with a marked increase in the concentrations of all major anthropogenic aerosol constituents. The higher non-event mass concentration (total mass concentrations range between 6.88 and 16.30 µg m-3) and, thus, a larger surface area, tended to suppress new particle formation, more efficiently depleting potential gaseous precursors for nucleation. The analysis of water-soluble organic compounds showed that clean nucleation episodes were dominated by aliphatic biogenic species, while non-events were characterised by a large abundance of anthropogenic oxygenated species. Interestingly, a significant content of ?-pinene photo-oxidation products was observed in the events aerosol, accounting for, on average, 72% of their WSOC; while only moderate amounts of these species were found in the non-event aerosol. If the organic vapors condensing onto accumulation mode particles are responsible also for the growth of newly formed thermodynamically stable clusters, our finding allows one to postulate that, at the site, ?-pinene photo-oxidation products (and probably also photo-oxidation products from other terpenes) are the most likely species to contribute to the growth of nanometer-sized particles

Size-segregated aerosol mass closure and chemical composition in Monte Cimone (I) during MINATROC

International audiencePhysical and chemical characterizations of the atmospheric aerosol were carried out at Mt. Cimone (Italy) during the 4 June-4 July 2000 period. Particle size distributions in the size range 6nm-10µm were measured with a differential mobility analyzer (DMA) and an optical particle counter (OPC). Size-segregated aerosol was sampled using a 6-stage low pressure impactor. Aerosol samples were submitted to gravimetric and chemical analyses. Ionic, carbonaceous and refractory components of the aerosol were quantified. We compared the sub- and superµm aerosol mass concentrations determined by gravimetric measurements (mGM), chemical analyses (mmCA), and by converting particle size distribution to aerosol mass concentrations (mmSD). Mean random uncertainties associated with the determination of mmGM, mmCA, and mmSD were assessed. The three estimates of the sub-µm aerosol mass concentration agreed, which shows that within experimental uncertainty, the sub-µm aerosol was composed of the quantified components. The three estimates of the super-µm aerosol mass concentration did not agree, which indicates that random uncertainties and/or possible systematic errors in aerosol sampling, sizing or analyses were not adequately accounted for. Aerosol chemical composition in air masses from different origins showed differences, which were significant in regard to experimental uncertainties. During the Saharan dust advection period, coarse dust and fine anthropogenic particles were externally mixed. No anthropogenic sulfate could be found in the super-µm dust particles. In contrast, nitrate was shifted towards the aerosol super-µm fraction in presence of desert dust

Synchronous oceanic spreading and continental rifting in West Antarctica

Magnetic anomalies associated with new ocean crust formation in the Adare Basin off north-western Ross Sea (43 – 26 Ma) can be traced directly into the Northern Basin that underlies the adjacent morphological continental shelf, implying a continuity in the emplacement of oceanic crust. Steep gravity gradients along the margins of the Northern Basin, particularly in the east, suggest that little extension and thinning of continental crust occurred before it ruptured and the new oceanic crust formed, unlike most other continental rifts and the Victoria Land Basin further south. A pre-existing weak crust and localisation of strain by strike slip faulting are proposed as the factors allowing the rapid rupture of continental crust

Significant variations of trace gas composition and aerosol properties at Mt. Cimone during air mass transport from North Africa – contributions from wildfire emissions and mineral dust

Abstract. High levels of trace gas (O3 and CO) and aerosol (BC, fine and coarse particle volumes), as well as high scattering coefficient (σp) values, were recorded at the regional GAW-WMO station of Mt. Cimone (CMN, 2165 m a.s.l., Italy) during the period 26–30 August 2007. Analysis of air-mass circulation, aerosol chemical characterization and trace gas and aerosol enhancement ratios (ERs), showed that high O3 and aerosol levels were likely linked to (i) the transport of anthropogenic pollution from northern Italy, and (ii) the advection of air masses rich in mineral dust and biomass burning (BB) products from North Africa. In particular, during the advection of air masses from North Africa, the CO and aerosol levels (CO: 175 ppbv, BC: 1015 ng/m3, fine particle volume: 3.00 μm3 cm−3, σp: 84.5 Mm−1) were even higher than during the pollution event (CO: 138 ppbv, BC: 733 ng/m3, fine particles volume: 1.58 μm3 cm−3, σp: 44.9 M

Significant variations of trace gas composition and aerosol properties at Mt. Cimone during air mass transport from North Africa – contributions from wildfire emissions and mineral dust

High levels of trace gas (O3 and CO) and aerosol (BC, fine and coarse particle volumes), as well as high scattering coefficient (σp) values, were recorded at the regional GAW-WMO station of Mt. Cimone (CMN, 2165 m a.s.l., Italy) during the period 26–30 August 2007. Analysis of air-mass circulation, aerosol chemical characterization and trace gas and aerosol enhancement ratios (ERs), showed that high O3 and aerosol levels were likely linked to (i) the transport of anthropogenic pollution from northern Italy, and (ii) the advection of air masses rich in mineral dust and biomass burning (BB) products from North Africa. In particular, during the advection of air masses from North Africa, the CO and aerosol levels (CO: 175 ppbv, BC: 1015 ng/m3, fine particle volume: 3.00 μm3 cm−3, σp: 84.5 Mm−1) were even higher than during the pollution event (CO: 138 ppbv, BC: 733 ng/m3, fine particles volume: 1.58 μm3 cm−3, σp: 44.9 Mm). Moreover, despite the presence of mineral dust able to affect significantly the O3 concentration, the analysis of ERs showed that the BB event represented an efficient source of fine aerosol particles (e.g. BC), but also of the O3 recorded at CMN. In particular, the calculated O3/CO ERs (0.10–0.17 ppbv/ppbv) were in the range of values found in literature for relatively aged (2–4 days) BB plumes and suggested significant photochemical O3 production during the air-mass transport. For fine particles and σp, the calculated ERs was higher in the BB plumes than during the anthropogenic pollution events, stressing the importance of the identified BB event as a source of atmospheric aerosol able to affect the atmospheric radiation budget. These results suggest that episodes of mineral dust mobilization and wildfire emissions over North Africa could significantly influence radiative properties (as deduced from σp observations at CMN) and air quality over the Mediterranean basin and northern Italy

Simultaneous Detection of Alkylamines in the Surface Ocean and Atmosphere of the Antarctic Sympagic Environment

Measurements of alkylamines from seawater and atmospheric samples collected simultaneously across the Antarctic Peninsula, South Orkney and South Georgia Islands are reported. Concentrations of mono-, di-, and trimethylamine (MMA, DMA, and TMA, respectively), and their precursors, the quarternary amines glycine betaine and choline, were enhanced in sympagic seawater samples relative to ice-devoid pelagic ones, suggesting the microbiota of sea ice and sea ice-influenced ocean is a major source of these compounds. Primary sea-spray aerosol particles artificially generated by bubbling seawater samples were investigated by aerosol time-of-flight mass spectrometry (ATOFMS) of single particles; their mixing state indicated that alkylamines were aerosolized with sea spray from dissolved and particulate organic nitrogen pools. Despite this unequivocal sea spray-associated source of alkylamines, ATOFMS analyses of ambient aerosols in the sympagic region indicated that the majority (75–89%) of aerosol alkylamines were of secondary origin, that is, incorporated into the aerosol after gaseous air–sea exchange. These findings show that sympagic seawater properties are a source of alkylamines influencing the biogenic aerosol fluxed from the ocean into the boundary layer; these organic nitrogen compounds should be considered when assessing secondary aerosol formation processes in Antarctica

Corrigendum to "Chemical characterization of springtime submicrometer aerosol in Po Valley, Italy" published in Atmos. Chem. Phys., 12, 8401–8421, 2012

No abstract available

Regional variation of organic functional groups in aerosol particles on four U.S. east coast platforms during the International Consortium for Atmospheric Research on Transport and Transformation 2004 campaign

Submicron atmospheric aerosol samples were collected during the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) 2004 campaign on four platforms: Chebogue Point (Nova Scotia, Canada), Appledore Island (Maine), the CIRPAS Twin Otter over Ohio, and the NOAA R/V Ronald H. Brown in the Gulf of Maine. Saturated aliphatic C-C-H, unsaturated aliphatic C=C−H, aromatic C=C−H, organosulfur C-O-S, carbonyl C=O, and organic hydroxyl C-OH functional groups were measured by calibrated Fourier Transform Infrared (FTIR) spectroscopy at all four sampling platforms. The ratio of molar concentrations of carbonyl C=O to saturated aliphatic C-C-H groups was nearly constant at each sampling platform, with the Twin Otter samples having the lowest ratio at 0.1 and the three more coastal platforms having ratios of 0.4 and 0.5. Organic mass (OM) to organic carbon (OC) ratios follow similar trends for the four platforms, with the Twin Otter having the lowest ratio of 1.4 and the coastal platforms having slightly higher values typically between 1.5 and 1.6. Organosulfur compounds were occasionally observed. Collocated organic aerosol sampling with two Aerodyne aerosol mass spectrometers for OM, a Sunset Laboratory thermo-optical analysis instrument for OC, and an ion chromatography-particle into liquid sampler (IC-PILS) for speciated carboxylic acids provided comparable results for most of the project, tracking the time series of FTIR OM, OC, and carbonyl groups, respectively, and showing simultaneous peaks of similar magnitude during most of the project. The FTIR/IC-PILS comparison suggests that about 9% of the carbonyl groups found in submicron organic particles on the Twin Otter are typically associated with low molecular weight carboxylic acids