How do different marine engine fuels and wet scrubbing affect gaseous air pollutants and ozone formation potential from ship emissions?

Sulphur Emission Control Areas (SECAs), mandated by the International Maritime Organization (IMO), regulate fuel sulphur content (FSC) to mitigate the environmental and health impact of shipping emissions in coastal areas. Currently, FSC is limited to 0.1% (w/w) within and 0.5% (w/w) outside SECAs, with exceptions for ships employing wet sulphur scrubbers. These scrubbers enable vessels using non-compliant fuels such as high-sulphur heavy fuel oils (HFOs) to enter SECAs. However, while sulphur reduction via scrubbers is effective, their efficiency in capturing other potentially harmful gases remains uncertain. Moreover, emerging compliant fuels like highly aromatic fuels or low-sulphur blends lack characterisation and may pose risks. Over three years, we assessed emissions from an experimental marine engine at 25% and 75% load, representative of manoeuvring and cruising, respectively. First, characterizing emissions from five different compliant and non-compliant fuels (marine gas oil MGO, hydro-treated vegetable oil HVO, high-, low- and ultra-low sulphur HFOs), we calculated emission factors (EF). Then, the wet scrubber gas-phase capture efficiency was measured using compliant and non-compliant HFOs. NOx EF varied among fuels (5200-19700 mg/kWh), with limited scrubber reduction. CO (EF 750-13700 mg/kWh) and hydrocarbons (HC; EF 122-1851 mg/kWh) showed also insufficient abatement. Carcinogenic benzene was notably higher at 25% load and about an order of magnitude higher with HFOs compared to MGO and HVO, with no observed scrubber reduction. In contrast, carbonyls such as carcinogenic formaldehyde and acetaldehyde, acting as ozone precursors, were effectively scrubbed due to their polarity and water solubility. The ozone formation potential (OFP) of all fuels was examined. Significant EF differences between fuels and engine loads were observed, with the wet scrubber providing limited or no reduction of gaseous emissions. We suggest enhanced regulations and emission abatements in the marine sector to mitigate gaseous pollutants harmful to human health and the environment.

Humic-like Substances (HULIS) in Ship Engine Emissions: Molecular Composition Effected by Fuel Type, Engine Mode, and Wet Scrubber Usage.

Humic-like substances (HULIS), known for their substantial impact on the atmosphere, are identified in marine diesel engine emissions obtained from five different fuels at two engine loads simulating real world scenarios as well as the application of wet sulfur scrubbers. The HULIS chemical composition is characterized by electrospray ionization (ESI) ultrahigh resolution mass spectrometry and shown to contain partially oxidized alkylated polycyclic aromatic compounds as well as partially oxidized aliphatic compounds, both including abundant nitrogen- and sulfur-containing species, and clearly different to HULIS emitted from biomass burning. Fuel properties such as sulfur content and aromaticity as well as the fuel combustion efficiency and engine mode are reflected in the observed HULIS composition. When the marine diesel engine is operated below the optimum engine settings, e.g., during maneuvering in harbors, HULIS-C emission factors are increased (262-893 mg kg-1), and a higher number of HULIS with a shift toward lower degree of oxidation and higher aromaticity is detected. Additionally, more aromatic and aliphatic CHOS compounds in HULIS were detected, especially for high-sulfur fuel combustion. The application of wet sulfur scrubbers decreased the HULIS-C emission factors by 4-49% but also led to the formation of new HULIS compounds. Overall, our results suggest the consideration of marine diesel engines as a relevant regional source of HULIS emissions.

An alternative in vitro model considering cell-cell interactions in fiber-induced pulmonary fibrosis.

Particularly since the wide-ranging health effects of asbestos exposure became known, great emphasis has been placed on detailed toxicity testing of known but also newly developed fiber materials. Exposure to respirable pollutants like fibers can lead to tissue injury causing lung diseases such as pulmonary fibrosis or cancer. In order to detect the toxic potential of such aerosols at an early stage, the development of suitable test systems is essential. In this study, we illustrate the development of an advanced in vitro cell model closely resembling the physiological structure of the alveoli, and we highlight its advantages over simpler models to predict pro-fibrotic changes. For this reason, we analyzed the cytotoxic effects of fiber-like multi-walled carbon nanotubes after 24 and 48 h exposure, and we investigated inflammatory, genotoxic and pro-fibrotic changes occurring in the developed triple culture consisting of lung epithelial cells, macrophages and fibroblasts compared to a co-culture of epithelial cells and fibroblasts or a mono culture of epithelial cells. In summary, the triple culture system is more precisely able to detect a pro-fibrotic phenotype including epithelial-mesenchymal transition as well as secondary genotoxicity, even if exhibiting lower cytotoxicity in contrast to the less advanced systems. These effects might be traced back to the complex interplay between the different cell types, all of which play an important role in the inflammatory response, which precedes wound healing, or even fibrosis or cancer development.

External trap-and-release membrane inlet for photoionization mass spectrometry: Towards fast direct analysis of aromatic pollutants in aquatic systems.

RATIONALE: Fast and sensitive detection of aromatic hydrocarbons (AHs) in water is of high importance because of their significant impact on human health and the environment. For this, resonance-enhanced multiphoton ionization (REMPI) coupled to trap-and-release membrane-introduction mass spectrometry (T&R-MIMS) offers the possibility of sensitive on-line water analysis with a time resolution of minutes. METHODS: REMPI is a versatile tool for sensitive gas-phase analysis, in which AHs are selectively ionized in complex gas mixtures by the subsequent absorption of at least two photons. In T&R-MIMS, selective extraction and enrichment of analytes from water can be achieved using semipermeable membranes. By the subsequent stimulated desorption of enriched compounds, mass spectrometric detection is enabled. RESULTS: We present an external T&R inlet for hollow-fiber membranes coupled to REMPI time-of-flight mass spectrometry, which enables direct and sensitive detection of semi-volatile AHs in water. In laboratory experiments, spiked water samples were analyzed. For the investigated compounds, limits of detection (LODs) in the range 1-47 ng/L were determined. The LODs are approximately one order of magnitude lower than in a previously reported continuous membrane-introduction approach using a planar membrane. Further improvement of LOD may be realized by extending the trapping time and by increasing the release temperature. Furthermore, the system was applied to investigate different fuels suspended in water and real water samples. The obtained data are in good agreement with findings of a former study. CONCLUSIONS: In the framework of the present study, we demonstrate the high potential of the combination of REMPI and T&R-MIMS in the form of a newly developed external hollow-fiber membrane inlet. With the developed system, semi-volatile AHs can be directly detected down to ng/L levels on a minute time scale. The approach thus may pave the way to future ship application in marine sciences, natural resources exploration or pollutant and hazard detection.

Influence of wood species on toxicity of log-wood stove combustion aerosols: a parallel animal and air-liquid interface cell exposure study on spruce and pine smoke.

BACKGROUND: Wood combustion emissions have been studied previously either by in vitro or in vivo models using collected particles, yet most studies have neglected gaseous compounds. Furthermore, a more accurate and holistic view of the toxicity of aerosols can be gained with parallel in vitro and in vivo studies using direct exposure methods. Moreover, modern exposure techniques such as air-liquid interface (ALI) exposures enable better assessment of the toxicity of the applied aerosols than, for example, the previous state-of-the-art submerged cell exposure techniques. METHODS: We used three different ALI exposure systems in parallel to study the toxicological effects of spruce and pine combustion emissions in human alveolar epithelial (A549) and murine macrophage (RAW264.7) cell lines. A whole-body mouse inhalation system was also used to expose C57BL/6 J mice to aerosol emissions. Moreover, gaseous and particulate fractions were studied separately in one of the cell exposure systems. After exposure, the cells and animals were measured for various parameters of cytotoxicity, inflammation, genotoxicity, transcriptome and proteome. RESULTS: We found that diluted (1:15) exposure pine combustion emissions (PM1 mass 7.7 ± 6.5 mg m- 3, 41 mg MJ- 1) contained, on average, more PM and polycyclic aromatic hydrocarbons (PAHs) than spruce (PM1 mass 4.3 ± 5.1 mg m- 3, 26 mg MJ- 1) emissions, which instead showed a higher concentration of inorganic metals in the emission aerosol. Both A549 cells and mice exposed to these emissions showed low levels of inflammation but significantly increased genotoxicity. Gaseous emission compounds produced similar genotoxicity and a higher inflammatory response than the corresponding complete combustion emission in A549 cells. Systems biology approaches supported the findings, but we detected differing responses between in vivo and in vitro experiments. CONCLUSIONS: Comprehensive in vitro and in vivo exposure studies with emission characterization and systems biology approaches revealed further information on the effects of combustion aerosol toxicity than could be achieved with either method alone. Interestingly, in vitro and in vivo exposures showed the opposite order of the highest DNA damage. In vitro measurements also indicated that the gaseous fraction of emission aerosols may be more important in causing adverse toxicological effects. Combustion aerosols of different wood species result in mild but aerosol specific in vitro and in vivo effects.

Development and Optimization of an External-Membrane Introduction Photoionization Mass Spectrometer for the Fast Analysis of (Polycyclic)Aromatic Compounds in Environmental and Process Waters.

The development of sensitive analytical techniques for the real-time detection of aromatic hydrocarbons (AHs) and polycyclic aromatic hydrocarbons (PAHs) is of high importance, because of their impact on human health and the environment. A promising approach, regarding to direct determination of (P)AHs in aqueous samples, is resonance-enhanced multiphoton ionization (REMPI) coupled to external-membrane introduction mass spectrometry (eMIMS). In eMIMS, analytes are extracted from the water phase into the gas phase, which is supplied to the MS by using an external semipermeable membrane setup. As a result, no laborious enrichment techniques are needed. With REMPI, ions are formed by the subsequent absorption of two photons via an excited molecular state. The unique ionization scheme of REMPI provides selective and sensitive detection of (P)AHs. When combining the capabilities of REMPI and MIMS, direct measurements of sub-µg/L concentrations of small (polycyclic)aromatic compounds are feasible. In this study, we present an external sheet membrane probe (ESMP) for the determination of selected (polycyclic)aromatic species in water samples by using REMPI time-of-flight mass spectrometry (REMPI-TOFMS). This inlet design shows promising results with respect to the direct analysis of (P)AHs in aquatic environments. With this early stage system, concentrations down to tens of ng/L for selected small (polycyclic)aromatic compounds are accessible within minutes without any sample preparation.

Highly time-resolved imaging of combustion and pyrolysis product concentrations in solid fuel combustion: NO formation in a burning cigarette.

The highly dynamic, heterogeneous combustion process within a burning cigarette was investigated by a miniaturized extractive sampling probe (microprobe) coupled to photoionization mass spectrometry using soft laser single photon ionization (SPI) for online real-time detection of molecular ions of combustion and pyrolysis products. Research cigarettes smoked by a smoking machine are used as a reproducible model system for solid-state biomass combustion, which up to now is not addressable by current combustion-diagnostic tools. By combining repetitively recorded online measurement sequences from different sampling locations in an imaging approach, highly time- and space-resolved quantitative distribution maps of, e.g., nitrogen monoxide, benzene, and oxygen concentrations were obtained at a near microscopic level. The obtained quantitative distribution maps represent a time-resolved, movie-like imaging of the respective compound's formation and destruction zones in the various combustion and pyrolysis regions of a cigarette during puffing. Furthermore, spatially resolved kinetic data were ascertainable. The here demonstrated methodology can also be applied to various heterogenic combustion/pyrolysis or reaction model systems, such as fossil- or biomass-fuel pellet combustion or to a positional resolved analysis of heterogenic catalytic reactions.

Real-time analysis of organic compounds in ship engine aerosol emissions using resonance-enhanced multiphoton ionisation and proton transfer mass spectrometry.

Organic combustion aerosols from a marine medium-speed diesel engine, capable to run on distillate (diesel fuel) and residual fuels (heavy fuel oil), were investigated under various operating conditions and engine parameters. The online chemical characterisation of the organic components was conducted using a resonance-enhanced multiphoton ionisation time-of-flight mass spectrometer (REMPI TOF MS) and a proton transfer reaction-quadrupole mass spectrometer (PTR-QMS). Oxygenated species, alkenes and aromatic hydrocarbons were characterised. Especially the aromatic hydrocarbons and their alkylated derivatives were very prominent in the exhaust of both fuels. Emission factors of known health-hazardous compounds (e.g. mono- and poly-aromatic hydrocarbons) were calculated and found in higher amounts for heavy fuel oil (HFO) at typical engine loadings. Lower engine loads lead in general to increasing emissions for both fuels for almost every compound, e.g. naphthalene emissions varied for diesel fuel exhaust between 0.7 mg/kWh (75 % engine load, late start of injection (SOI)) and 11.8 mg/kWh (10 % engine load, late SOI) and for HFO exhaust between 3.3 and 60.5 mg/kWh, respectively. Both used mass spectrometric techniques showed that they are particularly suitable methods for online monitoring of combustion compounds and very helpful for the characterisation of health-relevant substances. Graphical abstract Three-dimensional REMPI data of organic species in diesel fuel and heavy fuel oil exhaust.

Differential proteomic analysis of mouse macrophages exposed to adsorbate-loaded heavy fuel oil derived combustion particles using an automated sample-preparation workflow.

Ship diesel combustion particles are known to cause broad cytotoxic effects and thereby strongly impact human health. Particles from heavy fuel oil (HFO) operated ships are considered as particularly dangerous. However, little is known about the relevant components of the ship emission particles. In particular, it is interesting to know if the particle cores, consisting of soot and metal oxides, or the adsorbate layers, consisting of semi- and low-volatile organic compounds and salts, are more relevant. We therefore sought to relate the adsorbates and the core composition of HFO combustion particles to the early cellular responses, allowing for the development of measures that counteract their detrimental effects. Hence, the semi-volatile coating of HFO-operated ship diesel engine particles was removed by stepwise thermal stripping using different temperatures. RAW 264.7 macrophages were exposed to native and thermally stripped particles in submersed culture. Proteomic changes were monitored by two different quantitative mass spectrometry approaches, stable isotope labeling by amino acids in cell culture (SILAC) and dimethyl labeling. Our data revealed that cells reacted differently to native or stripped HFO combustion particles. Cells exposed to thermally stripped particles showed a very differential reaction with respect to the composition of the individual chemical load of the particle. The cellular reactions of the HFO particles included reaction to oxidative stress, reorganization of the cytoskeleton and changes in endocytosis. Cells exposed to the 280 °C treated particles showed an induction of RNA-related processes, a number of mitochondria-associated processes as well as DNA damage response, while the exposure to 580 °C treated HFO particles mainly induced the regulation of intracellular transport. In summary, our analysis based on a highly reproducible automated proteomic sample-preparation procedure shows a diverse cellular response, depending on the soot particle composition. In particular, it was shown that both the molecules of the adsorbate layer as well as particle cores induced strong but different effects in the exposed cells.

Looking into individual coffee beans during the roasting process: direct micro-probe sampling on-line photo-ionisation mass spectrometric analysis of coffee roasting gases.

A micro-probe (µ-probe) gas sampling device for on-line analysis of gases evolving in confined, small objects by single-photon ionisation time-of-flight mass spectrometry (SPI-TOFMS) was developed. The technique is applied for the first time in a feasibility study to record the formation of volatile and flavour compounds during the roasting process within (inside) or in the direct vicinity (outside) of individual coffee beans. A real-time on-line analysis of evolving volatile and semi-volatile organic compounds (VOC and SVOC) as they are formed under the mild pyrolytic conditions of the roasting process was performed. The soft-ionisation mass spectra depict a molecular ion signature, which is well corresponding with the existing knowledge of coffee roasting and evolving compounds. Additionally, thereby it is possible to discriminate between Coffea arabica (Arabica) and Coffea canephora (Robusta). The recognized differences in the roasting gas profiles reflect the differences in the precursor composition of the coffee cultivars very well. Furthermore, a well-known set of marker compounds for Arabica and Robusta, namely the lipids kahweol and cafestol (detected in their dehydrated form at m/z 296 and m/z 298, respectively) were observed. If the variation in time of different compounds is observed, distinctly different evolution behaviours were detected. Here, phenol (m/z 94) and caffeine (m/z 194) are exemplary chosen, whereas phenol shows very sharp emission peaks, caffeine do not have this highly transient behaviour. Finally, the changes of the chemical signature as a function of the roasting time, the influence of sampling position (inside, outside) and cultivar (Arabica, Robusta) is investigated by multivariate statistics (PCA). In summary, this pilot study demonstrates the high potential of the measurement technique to enhance the fundamental knowledge of the formation processes of volatile and semi-volatile flavour compounds inside the individual coffee bean.

Processing of carbon-reinforced construction materials releases PM2.5 inducing inflammation and (secondary) genotoxicity in human lung epithelial cells and fibroblasts.

Building demolition following domestic fires or abrasive processing after thermal recycling can release particles harmful for the environment and human health. To mimic such situations, particles release during dry-cutting of construction materials was investigated. A reinforcement material consisting of carbon rods (CR), carbon concrete composite (C³) and thermally treated C³ (ttC³) were physicochemically and toxicologically analyzed in monocultured lung epithelial cells, and co-cultured lung epithelial cells and fibroblasts at the air-liquid interface. C³ particles reduced their diameter to WHO fibre dimensions during thermal treatment. Caused by physical properties or by polycyclic aromatic hydrocarbons and bisphenol A found in the materials, especially the released particles of CR and ttC³ induced an acute inflammatory response and (secondary) DNA damage. Transcriptome analysis indicated that CR and ttC³ particles carried out their toxicity via different mechanisms. While ttC³ affected pro-fibrotic pathways, CR was mostly involved in DNA damage response and in pro-oncogenic signaling.

Aerosol emissions from a marine diesel engine running on different fuels and effects of exhaust gas cleaning measures.

The emissions of marine diesel engines have gained both global and regional attentions because of their impact on human health and climate change. To reduce ship emissions, the International Maritime Organization capped the fuel sulfur content of marine fuels. Consequently, either low-sulfur fuels or additional exhaust gas cleaning devices for the reduction in sulfur dioxide (SO2) emissions became mandatory. Although a wet scrubber reduces the amount of SO2 significantly, there is still a need to consider the reduction in particle emissions directly. We present data on the particle removal efficiency of a scrubber regarding particle number and mass concentration with different marine fuel types, marine gas oil, and two heavy fuel oils (HFOs). An open-loop sulfur scrubber was installed in the exhaust line of a marine diesel test engine. Fine particulate matter was comprehensively characterized in terms of its physical and chemical properties. The wet scrubber led up to a 40% reduction in particle number, whereas a reduction in particle mass emissions was not generally determined. We observed a shift in the size distribution by the scrubber to larger particle diameters when the engine was operated on conventional HFOs. The reduction in particle number concentrations and shift in particle size were caused by the coagulation of soot particles and formation/growing of sulfur-containing particles. Combining the scrubber with a wet electrostatic precipitator as an additional abatement system showed a reduction in particle number and mass emission factors by >98%. Therefore, the application of a wet scrubber for the after-treatment of marine fuel oil combustion will reduce SO2 emissions, but it does not substantially affect the number and mass concentration of respirable particulate matters. To reduce particle emission, the scrubber should be combined with additional abatement systems.

Pyrolysis and combustion of tobacco in a cigarette smoking simulator under air and nitrogen atmosphere.

A coupling between a cigarette smoking simulator and a time-of-flight mass spectrometer was constructed to allow investigation of tobacco smoke formation under simulated burning conditions. The cigarette smoking simulator is designed to burn a sample in close approximation to the conditions experienced by a lit cigarette. The apparatus also permits conditions outside those of normal cigarette burning to be investigated for mechanistic understanding purposes. It allows control of parameters such as smouldering and puff temperatures, as well as combustion rate and puffing volume. In this study, the system enabled examination of the effects of "smoking" a cigarette under a nitrogen atmosphere. Time-of-flight mass spectrometry combined with a soft ionisation technique is expedient to analyse complex mixtures such as tobacco smoke with a high time resolution. The objective of the study was to separate pyrolysis from combustion processes to reveal the formation mechanism of several selected toxicants. A purposely designed adapter, with no measurable dead volume or memory effects, enables the analysis of pyrolysis and combustion gases from tobacco and tobacco products (e.g. 3R4F reference cigarette) with minimum aging. The combined system demonstrates clear distinctions between smoke composition found under air and nitrogen smoking atmospheres based on the corresponding mass spectra and visualisations using principal component analysis.

Hyphenation of a carbon analyzer to photo-ionization mass spectrometry to unravel the organic composition of particulate matter on a molecular level.

The carbonaceous fraction of airborne particulate matter (PM) is of increasing interest due to the adverse health effects they are linked to. Its analytical ascertainment on a molecular level is still challenging. Hence, analysis of carbonaceous fractions is often carried out by determining bulk parameters such as the overall content of organic compounds (OC) and elemental carbon (EC) as well as the total carbon content, TC (sum of OC and EC), however, no information about the individual substances or substance classes, of which the single fractions consist can be obtained. In this work, a carbon analyzer and a photo-ionization time-of-flight mass spectrometer (PI-TOF-MS) were hyphenated to investigate individual compounds especially from the OC fractions. The carbon analyzer enables the stepwise heating of particle samples and provides the bulk parameters. With the PI-TOF-MS, it is possible to detect the organic compounds released during the single-temperature steps due to soft ionization and fast detection of the molecular ions. The hyphenation was designed, built up, characterized by standard substances, and applied to several kinds of samples, such as ambient aerosol, gasoline, and diesel emission as well as wood combustion emission samples. The ambient filter sample showed a strong impact of wood combustion markers. This was revealed by comparison to the product pattern of the similar analysis of pure cellulose and lignin and the wood combustion PM. At higher temperatures (450 °C), a shift to smaller molecules occurred due to the thermal decomposition of larger structures of oligomeric or polymeric nature comparable to lignocelluloses and similar oxygenated humic-like substances. Finally, particulate matter from gasoline and diesel containing 10% biodiesel vehicle exhaust has been analyzed. Gasoline-derived PM exhibited large polycyclic aromatic hydrocarbons, whereas diesel PM showed a much higher total organic content. The detected pattern revealed a strong influence of the biodiesel content on the nature of the particulate organic material.

Highly resolved online organic-chemical speciation of evolved gases from thermal analysis devices by cryogenically modulated fast gas chromatography coupled to single photon ionization mass spectrometry.

Multi-dimensional analysis (MDA) in analytical chemistry is often applied to improve the selectivity of an analytical device and, therefore, to achieve a better overview of a sample composition. Recently, the hyphenation of thermogravimetry with single photo ionization mass spectrometry (TG-SPIMS) using an electron beam pumped excimer lamp (EBEL) for VUV radiation was applied. The concept of MDA has been realized by upgrading the TG-SPIMS system with a quasi comprehensive chromatographic separation step before the soft ionization (TG-GCxSPIMS). The system was characterized by the thermal analysis of diesel fuel, which has often been investigated by the GCxGC-community and is therefore a well-known sample material in MDA. Data from this measurement are used to explain the three-dimensional data structure and the advantages of the online TG-GCxSPIMS as compared to TG-SPIMS. Subsequently, the thermal decomposition behavior of a polymer, acrylonitrile-butadiene-styrene (ABS), is investigated. TG-GCxSPIMS provides a two-dimensional analysis of the evolved gaseous products. TG relevant data are obtained as well as an improved resolution power to separate isobaric molecular structures without losing any fraction of the samples, as is often the case in heart cutting approaches. Additionally, this solution is not associated with any extension of the measurement time. The assignment of the substance pattern to distinct species is improved as compared to solely using mass spectrometry without a preceding separation step. Furthermore, hitherto undetected compounds have been found in the evolved gases from the thermal degradation of ABS. Finally, a first estimation of the limit of detection has been carried out. This results in a significant decrease of the LOD in case of TG-GCxSPIMS (500 ppt for toluene) as compared to 30 ppb, which could be reached with TG-SPIMS.

Characterization of Polyethylene Branching by Thermal Analysis-Photoionization Mass Spectrometry.

The rising demand for more and more specialized polyethylene represents a challenge for synthesis and analysis. The desired properties are dependent on the structure, but its elucidation is still intricate. For this purpose, we applied thermal analysis hyphenated to single photon ionization mass spectrometry (STA-SPI-MS). The melting and pyrolysis behavior of different types of polyethylene were tracked by DSC and mass loss. Crystallinity and melting point give hints about the branching but are also influenced by the molecular weight distribution. The evolving gas analysis patterns obtained by SPI-MS however, contain specific molecular information about the samples. Shifts in the summed spectra, which can be clearly observed with our technique, result from differently favored degradation reactions due to the respective structure. Pyrolysis gas chromatography mass spectrometry (Py-GC-EI-MS) was used to support the assignment of pyrolysis products. Principal component analysis was successfully applied to reduce the complexity of data and find suitable markers. The obtained grouping is based on the molecular fingerprint of the samples and is strongly influenced by short-chain branching. Short and medium alkenes and dienes have the strongest impact on the first four principal components. Thus, two marker ratios could be defined, which also give a comprehensible and robust grouping. Butene and pentene were the most abundant signals in our set of samples. With STA-PI-MS, a broad range of pyrolysis products can be measured at the same time, possibly extending the range for quantifiable short-chain branches to more than six carbon atoms for PE. Unfortunately, no clear trend between long-chain branching and any grouping was observed. The quite universal and soft single photon ionization enables access to many different compound classes and hence other polymers can be studied.

Real time monitoring of slow pyrolysis of polyethylene terephthalate (PET) by different mass spectrometric techniques.

In the context of waste upgrading of polyethylene terephthalate (PET) by pyrolysis, this study presents three on-line mass spectrometric techniques with soft ionization for monitoring the emitted decomposition products and their thermal dependent evolution profiles. Pyrolysis experiments were performed using a thermogravimetric analyzer (TGA) under nitrogen atmosphere with a heating rate of 5 °C/min from 30 °C to 600 °C. Single-photon ionization (SPI at 118 nm/10.5 eV) and resonance enhanced multiple photon ionization (REMPI at 266 nm) were used with time-of-flight mass spectrometry (TOF-MS) for evolved gas analysis (TGA-SPI/REMPI-TOFMS). Additionally, the chemical signature of the pyrolysis products was investigated by atmospheric pressure chemical ionization (APCI) ultra high resolution Fourier Transform ion cyclotron resonance mass spectrometry (FT-ICR MS) which enables assignment of molecular sum formulas (TGA-APCI FT-ICR MS). Despite the soft ionization by SPI, the fragmentation of some compounds with the loss of the [O-CH = CH2] fragment is observed. The major compounds were acetaldehyde (m/z 44), benzoic acid (m/z 122) and a fragment of m/z 149. Using REMPI, aromatic species were selectively detected. Several series of pyrolysis products were observed in different temperature intervals, showing the presence of polycyclic aromatic hydrocarbons (PAHs), especially at high temperatures. FT-ICR MS data showed, that the CHO4 class was the most abundant compound class with a relative abundance of 45.5%. The major compounds detected with this technique corresponded to m/z 193.0495 (C10H9O4+) and 149.0233 (C8H5O3+). Based on detailed chemical information, bulk reaction pathways are proposed, showing the formation of both cyclic monomer/dimer and linear structures.

Thermal desorption-multiphoton ionization time-of-flight mass spectrometry of individual aerosol particles: a simplified approach for online single-particle analysis of polycyclic aromatic hydrocarbons and their derivatives.

Online single-particle (SP) laser mass spectrometry (MS) is an important tool for fundamental and applied aerosol research. Usually laser desorption/ionization (LDI) is applied for ablation and ionization of atoms and molecular fragments from the nanometer- or micrometer-sized air-borne particles and time-of-flight analysers (TOFMS) are used for mass-selective detection of mainly inorganic analytes. The detection of molecular organic compounds is solely possible under very special experimental conditions and extremely dependent on the particle matrix and thus limited to special applications. Very recently it was shown that by implementation of a two-step laser desorption (LD) resonance-enhanced multiphoton ionization (REMPI) postionization approach the single-particulate molecular signature of polycyclic aromatic hydrocarbons (PAH) and their derivatives can be recorded (LD-REMPI-SP-TOFMS). By this, particles from different sources could be differentiated via the patterns of specific molecular source tracers such as retene for soft wood combustion or larger PAH as indicator for gasoline car emissions. One drawback of the LD-REMPI-SP-TOFMS method in particular for field applications is, however, the necessity of operation and adjustment of two lasers. In this paper the successful implementation of a thermal desorption step in single-particle mass spectrometry is described (TD-REMPI-SP-TOFMS). After size determination by particle velocimetry, individual particles are thermally desorbed on a heated surface in the ion source of the TOFMS. Desorbed molecules are ionized subsequently by REMPI, which addresses selectively PAH and molecular trace indicators. The TD-REMPI-SP-TOFMS concept was tested with reference particles and applied for automotive exhaust and ambient monitoring. The comparison of the results with the ones obtained by the two-laser approach (LD-REMPI-SP-TOFMS) indicates that the patented TD-REMPI-SP-TOFMS technology presented here is nearly equally well suited for studying organic source tracers in ambient aerosols and aerosol emissions. The increased ruggedness and simplicity of the new approach, however, may favor its application for field measurements in aerosol science and technology.

Impact of photochemical ageing on Polycyclic Aromatic Hydrocarbons (PAH) and oxygenated PAH (Oxy-PAH/OH-PAH) in logwood stove emissions.

The combustion of spruce logwood in a modern residential stove was found to emit polycyclic aromatic hydrocarbons (PAH) and oxygenated polycyclic aromatic hydrocarbons (OPAH) with emission factors of 404 µg MJ-1 of 35 analysed PAH, 317 µg MJ-1 of 11 analysed Oxy-PAH and 12.5 µg MJ-1 of 5 analysed OH-PAH, most of which are known as potential mutagens and carcinogens. Photochemical ageing in an oxidation flow reactor (OFR) degraded particle-bound PAH, which was also reflected in declining PAH toxicity equivalent (PAH-TEQ) values by 45 to 80% per equivalent day of photochemical ageing in the atmosphere. OPAH concentrations decreased less than PAH concentrations during photochemical ageing, supposedly due to their secondary formation, while 1-hydroxynaphthalene, 1,5-dihydroxynaphthalene and 1,8-naphthalaldehydic acid were significantly increased after ageing. Furthermore, secondary organic aerosol (SOA) formation and aromatic compounds not included in targeted analysis were investigated by thermal-optical carbon analysis (TOCA) hyphenate to resonance-enhanced multi-photon ionisation time-of-flight mass spectrometry (REMPI-TOFMS). The commonly used PAH-source indicators phenanthrene/anthracene, fluoranthene/pyrene, retene/chrysene, and indeno[cd]pyrene/benzo[ghi]perylene remained stable during photochemical ageing, enabling identification of wood combustion emissions in ambient air. On the other hand, benz[a]pyrene/benz[e]pyrene and benz[a]anthracene/chrysene were found to decrease with increasing photochemical age. Retene/chrysene was not a proper classifier for the wood combustion emissions of this study, possibly due to more efficient combustion than in open wood burning, from which this diagnostic ratio was initially derived. This study motivates in-depth investigation of degradation kinetics of particle-bound species on different combustion aerosol as well as the consequences of photochemical ageing on toxicity and identification of wood combustion emissions in ambient air.

Chemical composition and speciation of particulate organic matter from modern residential small-scale wood combustion appliances.

Combustion technologies of small-scale wood combustion appliances are continuously developed decrease emissions of various pollutants and increase energy conversion. One strategy to reduce emissions is the implementation of air staging technology in secondary air supply, which became an established technique for modern wood combustion appliances. On that account, emissions from a modern masonry heater fuelled with three types of common logwood (beech, birch and spruce) and a modern pellet boiler fuelled with commercial softwood pellets were investigated, which refer to representative combustion appliances in northern Europe In particular, emphasis was put on the organic constituents of PM2.5, including polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs (OPAHs) and phenolic species, by targeted and non-targeted mass spectrometric analysis techniques. Compared to conventional wood stoves and pellet boilers, organic emissions from the modern appliances were reduced by at least one order of magnitude, but to a different extent for single species. Hence, characteristic ratios of emission constituents and emission profiles for wood combustion identification and speciation do not hold for this type of advanced combustion technology. Additionally, an overall substantial reduction of typical wood combustion markers, such as phenolic species and anhydrous sugars, were observed. Finally, it was found that slow ignition of log woods changes the distribution of characteristic resin acids and phytosterols as well as their thermal alteration products, which are used as markers for specific wood types. Our results should be considered for wood combustion identification in positive matrix factorisation or chemical mass balance in northern Europe.