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We describe resonance effects in laser desorption–ionization (LDI) of particles that substantially increase the sensitivity and selectivity to metals in single-particle mass spectrometry (SPMS). Within the proposed scenario, resonant light absorption by ablated metal atoms increases their ionization rate within a single laser pulse. By choosing the appropriate laser wavelength, the key micronutrients Fe, Zn and Mn can be detected on individual aerosol particles with considerably improved efficiency. These ionization enhancements for metals apply to natural dust and anthropogenic aerosols, both important sources of bioavailable metals to marine environments. Transferring the results into applications, we show that the spectrum of our KrF-excimer laser is in resonance with a major absorption line of iron atoms. To estimate the impact of resonant LDI on the metal detection efficiency in SPMS applications, we performed a field experiment on ambient air with two alternately firing excimer lasers of different wavelengths. Herein, resonant LDI with the KrF-excimer laser (248.3 nm) revealed iron signatures for many more particles of the same aerosol ensemble compared to the more common ArF-excimer laser line of 193.3 nm (nonresonant LDI of iron). Many of the particles that showed iron contents upon resonant LDI were mixtures of sea salt and organic carbon. For nonresonant ionization, iron was exclusively detected in particles with a soot contribution. This suggests that resonant LDI allows a more universal and secure metal detection in SPMS. Moreover, our field study indicates relevant atmospheric iron transport by mixed organic particles, a pathway that might be underestimated in SPMS measurements based on nonresonant LDI. Our findings show a way to improve the detection and source attribution capabilities of SPMS for particle-bound metals, a health-relevant aerosol component and an important source of micronutrients to the surface oceans affecting marine primary productivity.

The human respiratory system is the gateway of entry for inhaled detritus from anthropogenic (e.g. combustion-derived (CD) particulate matter (PM; e.g. diesel exhaust and wood-burning PM). Adult humans inhale 20m3 of air and suspended debris (gases and particles) into the airways daily. Inhalation exposure to CDPM (Figure 1) is known to increase the risk of morbidity and mortality of lung and heart diseases in all exposed individuals. The physicochemical properties of size, surface area and presence of transition metals have been implicated as drivers of the oxidative capacity of CDPM. However, the precise role of reactive organic compounds (ROC) in ambient aerosols, present either in the gas or particle phase has not been fully-investigated for their relevance in the induction of the observed adverse health effects. When addressing the toxicity of inhalation hazards such as wood smoke CDPM, a model that resembles the human lung responding to toxic challenges is required. In our in vitro exposure studies, we utilised normal human bronchial epithelial (NHBE) cells grown at the air-liquid interface (ALI) using filter-well technology (Prytherch et al 2011), to create an in vivo-like 3-dimensional lung model. This model is a fully-differentiated, pseudo-stratified, muco-ciliary epithelium containing basal, serous, Clara, goblet and ciliated cells. NHBE cells were exposed to wood smoke derived from Spruce, Beech and Birch at a dose of 152µg/cm2: carbon black (CB; negative control; Monarch 120, Cabot UK; DQ12 quartz (positive control). Following exposure (24 hours), tissue integrity (i.e. transepithelial electrical resistance (TEER) was measured to reveal minor disruption to bronchial tissue integrity (Figure 2). However, changes in cellular energy levels (i.e. ATP) between the types of wood smokes (Figure 3), could infer the smoke acted as an irritant to the lung environment. Wood smoke exposure can depress the immune system and damage the layer of cells in the lungs that protect and cleanse the airways. Further work on the biological and histological impacts of wood smoke will allow us to reveal mechanisms behind the changes observed, as well identifying biomarkers of cell damage by specific CDPM ROCs. For vulnerable populations, such as people with asthma, chronic respiratory disease and those with cardiovascular disease, wood smoke is particularly harmful, even at short exposures it can prove dangerous. Wood smoke interferes with normal lung development in infants and children. It also increases children’s risk of lower respiratory infections such as bronchitis and pneumonia. Prytherch, Z., Job, C., Marshall, H., Oreffo, V., Foster, M. and BéruBé, K.A. (2011) Macro. Bios. 11, 1467–77. This work was supported by HICE (www.hice-vi.eu).

A lot of emission reduction measures to improve the air quality in Beijing were performed during the Olympic Summer Games in 2008, which has cut down coarse particles largely. But high air pollution has become more frequent (Du et al., 2014; Gao et al., 2014). In order to find out the long-term characteristics of airborne PM in different seasons, a continuous oneyear daily mean PM sampling from June 2010 till June 2011 was performed on the ground at the campus of the China University of Geosciences, Beijing (CUGB). To discriminate the composition of PM2.5 source attribution, particle characteristics and external impacts on the PM levels were investigated. Two sequential High-Volume operated to collect PM4 samples. The inorganic elements, inorganic water-soluble ions, EC and OC as well as Levoglucosan, eleven hopane substances and eleven PAHs of PM were analysed from PM samples by PEDXRF, ICP-MS, IC, thermal/optical carbon analyser and in situ derivatisation direct thermal desorption gas chromatography time-offlight mass spectrometry (IDTD-GC-TOFMS), respectively. Positive matrix factorization (version 3.0, U.S. EPA) on the basis of the chemical composition analyses and back trajectory cluster analyses were combined together to perform source apportionment. The results show that the main sources of particles during haze are different from season to season (Figure 1): secondary inorganic ions formation and biomass burning for summer and autumn haze, coal combustion for winter haze and mineral dust emissions for spring haze. Sources of PM during clear days were dominated by mineral dust emissions and traffic while haze was characterized by secondary inorganic ions formation during the whole year. High air pollution was found to be always accompanied by southerly air flows (industry and cities are about 100 km away), high relative humidity, low mixing layer height and low wind speed, i.e. stagnant weather conditions (Liu et al., 2014).

Background\ud \ud Ship engine emissions are important with regard to lung and cardiovascular diseases especially in coastal regions worldwide. Known cellular responses to combustion particles include oxidative stress and inflammatory signalling.\ud \ud Objectives\ud \ud To provide a molecular link between the chemical and physical characteristics of ship emission particles and the cellular responses they elicit and to identify potentially harmful fractions in shipping emission aerosols.\ud \ud Methods\ud \ud Through an air-liquid interface exposure system, we exposed human lung cells under realistic in vitro conditions to exhaust fumes from a ship engine running on either common heavy fuel oil (HFO) or cleaner-burning diesel fuel (DF). Advanced chemical analyses of the exhaust aerosols were combined with transcriptional, proteomic and metabolomic profiling including isotope labelling methods to characterise the lung cell responses.\ud \ud Results\ud \ud The HFO emissions contained high concentrations of toxic compounds such as metals and polycyclic aromatic hydrocarbon, and were higher in particle mass. These compounds were lower in DF emissions, which in turn had higher concentrations of elemental carbon (“soot”). Common cellular reactions included cellular stress responses and endocytosis. Reactions to HFO emissions were dominated by oxidative stress and inflammatory responses, whereas DF emissions induced generally a broader biological response than HFO emissions and affected essential cellular pathways such as energy metabolism, protein synthesis, and chromatin modification.\ud \ud Conclusions\ud \ud Despite a lower content of known toxic compounds, combustion particles from the clean shipping fuel DF influenced several essential pathways of lung cell metabolism more strongly than particles from the unrefined fuel HFO. This might be attributable to a higher soot content in DF. Thus the role of diesel soot, which is a known carcinogen in acute air pollution-induced health effects should be further investigated. For the use of HFO and DF we recommend a reduction of carbonaceous soot in the ship emissions by implementation of filtration devices.

A newly conceived compact and mobile time-of flight mass spectrometer (TOFMS) for real-time monitoring of highly complex gas mixtures is presented. The device utilizes two selective and sensitive soft ionization techniques, viz., resonance-enhanced multiphoton ionization (REMPI) and single-photon ionization (SPI) in a (quasi)-simultaneous mode. Both methods allow a fragmentationless ionization. The REMPI method selectively addresses aromatic species, while with SPI applying vacuum ultaviolet light (118 nm) in principle all compounds with an ionization potential below 10.5 eV are accessible. This provides comprehensive information of the chemical composition of complex matrixes. The combustion and pyrolysis behavior of five organic materials typically used in steel processing in China was studied. The trace amounts of organic compounds in the gas phase during combustion and pyrolysis were monitored selectively and sensitively by real-time SPI/REMPI-TOFMS. The measurements were carried out at several constant temperatures in the range from 300 to 1190 degrees C in both synthetic air and nitrogen. Timely resolved mass spectra reveal the formation and subsequent growth of aromatic molecules. At lower temperatures, highly alkylated PAHs predominate, while at temperatures above 800 degrees C, the more stable benzene and PAHs without side chains prevail. Potential hyphenation of SPI/REMPI-TOFMS to methods of thermal analysis is discussed.