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Czech H.,University of Rostock | Schepler C.,University of Rostock | Klingbeil S.,University of Rostock | Klingbeil S.,Helmholtz Virtual Institute of Complex Molecular Systems in Environmental Health HICE | And 6 more authors.
Journal of Agricultural and Food Chemistry | Year: 2016

Coffee beans of two cultivars, Arabica (Mexico) and Robusta (Vietnam), were roasted in a small-scale drum roaster at different temperature profiles. Evolving volatile compounds out of the roasting off-gas were analyzed by photoionization mass spectrometry at four different wavelengths, either with single-photon ionization (SPI) or resonance-enhanced multiphoton ionization (REMPI). The different analyte selectivities at the four wavelengths and their relevance for the examination of the roasting process were discussed. Furthermore, intensities of observed m/z were grouped by non-negative matrix factorization (NMF) to reveal the temporal evolutions of four roasting phases ("evaporation", "early roast", "late roast", and "overroast") from NMF scores and the corresponding molecular composition from the NMF factor loadings, giving chemically sound results concerning the roasting phases. Finally, linear classifiers were constructed from real mass spectra at maximum NMF scores by linear discriminant analysis to obtain quantities which are simple to measure for real-time analysis of the roasting process. © 2016 American Chemical Society. Source


Mueller L.,Helmholtz Center Munich | Mueller L.,University of Rostock | Mueller L.,Helmholtz Virtual Institute of Complex Molecular Systems in Environmental Health HICE | Schnelle-Kreis J.,Helmholtz Center Munich | And 10 more authors.
Journal of Aerosol Science | Year: 2016

In this study, we present the impact of fuel additives (Fe, Al, and V) on the measured particulate organic matter (OM) fraction formed from the combustion of propane-heated diesel fuel (DF) in a DF Combustion Aerosol STandard (DF-CAST) burner prototype within the range of air-fuel-equivalence ratios (λDF) from 5.4 to 10.4. The OM fraction was measured by using high resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) and unmixed into factor profiles by applying the SoFi program, a source apportionment tool using positive matrix factorization (PMF)/multilinear engine (ME-2) solvers. The separated factors were correlated with the particle light absorption properties at UV (370 nm) and IR (950 nm) wavelengths, NO3-, and NH4+ as well as exhaust gas (CO2, CO, NO, NH3, hydrocarbons (HC), and formaldehyde (HCHO)). Addition of Fe, Al, and V to the DF yielded apparent catalytic processes leading to the formation of nitrogen-containing particulate OM (CHN and CHON families). The separated factors were distinct in terms of their oxidation state, correlation with the measured particulate and gaseous emissions. Similarities in the separated factors based on temporal evolution were observed in DF and DF+additive experiments. This study gives a new insight in the modification of DF combustion particle properties in the presence of fuel additives. © 2016 Elsevier Ltd. Source


Mueller L.,Helmholtz Center Munich | Mueller L.,University of Rostock | Mueller L.,Helmholtz Virtual Institute of Complex Molecular Systems in Environmental Health HICE | Jakobi G.,Helmholtz Center Munich | And 31 more authors.
Applied Energy | Year: 2015

Due to current and upcoming regulations to address the adverse impacts of particulate matter (PM) from shipping emissions, the maritime sector is required to find energy-efficient ways to comply mainly by using low fuel sulfur content (FSC) in regulated seas. We studied the PM emission from a research ship diesel engine with fuel switching capability, optimized for HFO used at cruising, operated at representative engine loads resulting to varying excess O2 emission which was an indirect measurement of air-fuel mixture (λ), using heavy fuel oil (HFO, 1.6 S (%m)) and diesel fuel (DF, <0.001 S (%m)). We determined the characteristics and temporal evolution of the PM by using the High Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS) in combination with aethalometer, particle sizers, online gas phase, and filter measurements. The average emission factors were higher for HFO than for DF with relative percent differences of ~200, ~180, ~150, and ~145 for SO42-, inorganic elements, organic matter (OM), and PM2.5, respectively, while that for black carbon (BC) was similar for both fuels. The difference between HFO and DF in terms of carbonaceous emissions was higher at 100% and 25% than at 75% and 50% engine loads. The exhaust temperature (T) decreased with increasing λ leading to the enhanced emission of OM in HFO and reduced OM and BC emission in DF. Contributions of hydrocarbons and oxygenated hydrocarbons increased with λ for HFO and decreased with DF. Gas phase total hydrocarbon (THC) was well correlated with BC only for HFO and OM and BC for DF. Overall, using a lower FSC reduced average PM emissions, however, engine load, and λ were strongly linked to the characteristics and temporal evolution of major PM emissions. The information in this study may help the marine sector and policy-making process in evaluating and designing future solutions for shipping emission regulations and diagnostics. © 2015 Elsevier Ltd. Source


Mueller L.,Helmholtz Center Munich | Mueller L.,University of Rostock | Mueller L.,Helmholtz Virtual Institute of Complex Molecular Systems in Environmental Health HICE | Jakobi G.,Helmholtz Center Munich | And 16 more authors.
Analytical and Bioanalytical Chemistry | Year: 2015

In this study, we produced a class of diffusion flame soot particles with varying chemical and physical properties by using the mini-Combustion Aerosol STandard (CAST) and applying varying oxidant gas flow rates under constant propane, quenching, and dilution gas supply. We varied the soot properties by using the following fuel-to-air equivalence ratios (Φ): 1.13, 1.09, 1.04, 1.00, 0.96, and 0.89. Within this Φ range, we observed drastic changes in the physical and chemical properties of the soot. Oxidant-rich flames (Φ<1) were characterized by larger particle size, lower particle number concentration, higher black carbon (BC) concentration, lower brown carbon BrC.[BC]-1 than fuel-rich flames (Φ>1). To investigate the polycyclic aromatic hydrocarbons (PAH) formation online, we developed a new method for quantification by using the one 13C-containing doubly charged PAH ion in a high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS). The time-resolved concentration showed that the larger PAHs prevailed in the fuel-rich flames and diminished in the oxidant-rich flames. By comparison with the offline in situ derivatization-thermal-desorption gas-chromatography time-of-flight mass spectrometry (IDTD-GC-ToF-MS), we found that the concentration by using the HR-ToF-AMS was underestimated, especially for lower mass PAHs (C14-C18) in the fuel-rich flames possibly due to size limitation and degradation of semi-volatile species under high vacuum and desorption temperature in the latter. For oxidant-rich flames, the large PAHs (C20 and C22) were detected in the HR-ToF-AMS while it was not possible in IDTD-GC-ToF-MS due to matrix effect. The PAH formation was discussed based on the combination of our results and with respect to Φ settings. © 2015 Springer-Verlag. Source


Mueller L.,Helmholtz Center Munich | Mueller L.,University of Rostock | Mueller L.,Helmholtz Virtual Institute of Complex Molecular Systems in Environmental Health HICE | Jakobi G.,Helmholtz Center Munich | And 16 more authors.
Analytical and Bioanalytical Chemistry | Year: 2015

In this study, we produced a class of diffusion flame soot particles with varying chemical and physical properties by using the mini-Combustion Aerosol STandard (CAST) and applying varying oxidant gas flow rates under constant propane, quenching, and dilution gas supply. We varied the soot properties by using the following fuel-to-air equivalence ratios (Φ): 1.13, 1.09, 1.04, 1.00, 0.96, and 0.89. Within this Φ range, we observed drastic changes in the physical and chemical properties of the soot. Oxidant-rich flames (Φ < 1) were characterized by larger particle size, lower particle number concentration, higher black carbon (BC) concentration, lower brown carbon BrC.[BC]−1 than fuel-rich flames (Φ > 1). To investigate the polycyclic aromatic hydrocarbons (PAH) formation online, we developed a new method for quantification by using the one 13C-containing doubly charged PAH ion in a high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS). The time-resolved concentration showed that the larger PAHs prevailed in the fuel-rich flames and diminished in the oxidant-rich flames. By comparison with the offline in situ derivatization-thermal-desorption gas-chromatography time-of-flight mass spectrometry (IDTD-GC-ToF-MS), we found that the concentration by using the HR-ToF-AMS was underestimated, especially for lower mass PAHs (C14–C18) in the fuel-rich flames possibly due to size limitation and degradation of semi-volatile species under high vacuum and desorption temperature in the latter. For oxidant-rich flames, the large PAHs (C20 and C22) were detected in the HR-ToF-AMS while it was not possible in IDTD-GC-ToF-MS due to matrix effect. The PAH formation was discussed based on the combination of our results and with respect to Φ settings. © 2015 Springer-Verlag Berlin Heidelberg Source

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