@article{NehrBausCınaretal.2024, author = {Nehr, Sascha and Baus, Lukas and {\c{C}}{\i}nar, Hasan and Elsen, Ingo and Frauenrath, Tobias}, title = {Indoor environmental quality assessment in passively ventilated classrooms in Germany and estimation of ventilation energy losses}, series = {Journal of Building Engineering}, volume = {97}, journal = {Journal of Building Engineering}, publisher = {Elsevier}, issn = {2352-7102}, doi = {10.1016/j.jobe.2024.110937}, year = {2024}, language = {en} } @article{PangNovelliKaminskietal.2022, author = {Pang, Jacky Yat Sing and Novelli, Anna and Kaminski, Martin and Acir, Ismail-Hakki and Bohn, Birger and Carlsson, Philip T. M. and Cho, Changmin and Dorn, Hans-Peter and Hofzumahaus, Andreas and Li, Xin and Lutz, Anna and Nehr, Sascha and Reimer, David and Rohrer, Franz and Tillmann, Ralf and Wegener, Robert and Kiendler-Scharr, Astrid and Wahner, Andreas and Fuchs, Hendrik}, title = {Investigation of the limonene photooxidation by OH at different NO concentrations in the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber)}, series = {Atmospheric Chemistry and Physics}, volume = {22}, journal = {Atmospheric Chemistry and Physics}, number = {13}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-22-8497-2022}, pages = {8497 -- 8527}, year = {2022}, abstract = {Abstract. The oxidation of limonene by the hydroxyl (OH) radical and ozone (O3) was investigated in the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) in experiments performed at different nitric oxide (NO) mixing ratios from nearly 0 up to 10 ppbv. For the experiments dominated by OH oxidation, the formaldehyde (HCHO) yield was experimentally determined and found to be (12 ± 3), (13 ± 3), and (32 ± 5) \% for experiments with low (∼ 0.1 ppbv), medium (∼ 0.3 ppbv), and high NO (5 to 10 ppbv), respectively. The yield in an ozonolysis-only experiment was (10 ± 1) \%, which agrees with previous laboratory studies. The experimental yield of the first-generation organic nitrates from limonene-OH oxidation is calculated as (34 ± 5) \%, about 11 \% higher than the value in the Master Chemical Mechanism (MCM), which is derived from structure-activity relationships (SARs). Time series of measured radicals, trace-gas concentrations, and OH reactivity are compared to results from zero-dimensional chemical box model calculations applying MCM v3.3.1. Modeled OH reactivity is 5 to 10 s-1 (25 \% to 33 \% of the OH reactivity at the start of the experiment) higher than measured values at the end of the experiments under all chemical conditions investigated, suggesting either that there are unaccounted loss processes of limonene oxidation products or that products are less reactive toward OH. In addition, model calculations underestimate measured hydroperoxyl radical (HO2) concentrations by 20 \% to 90 \% and overestimate organic peroxyl radical (RO2) concentrations by 50 \% to 300 \%. The largest deviations are found in low-NO experiments and in the ozonolysis experiment. An OH radical budget analysis, which uses only measured quantities, shows that the budget is closed in most of the experiments. A similar budget analysis for RO2 radicals suggests that an additional RO2 loss rate constant of about (1-6) × 10-2 s-1 for first-generation RO2 is required to match the measured RO2 concentrations in all experiments. Sensitivity model runs indicate that additional reactions converting RO2 to HO2 at a rate constant of about (1.7-3.0) × 10-2 s-1 would improve the model-measurement agreement of NOx, HO2, and RO2 concentrations and OH reactivity. Reaction pathways that could lead to the production of additional OH and HO2 are discussed, which include isomerization reactions of RO2 from the oxidation of limonene, different branching ratios for the reaction of RO2 with HO2, and a faster rate constant for RO2 recombination reactions. As the exact chemical mechanisms of the additional HO2 and OH sources could not be identified, further work needs to focus on quantifying organic product species and organic peroxy radicals from limonene oxidation.}, language = {en} } @article{TanHantschkeKaminskietal.2021, author = {Tan, Zhaofeng and Hantschke, Luisa and Kaminski, Martin and Acir, Ismail-Hakki and Bohn, Birger and Cho, Changmin and Dorn, Hans-Peter and Li, Xin and Novelli, Anna and Nehr, Sascha and Rohrer, Franz and Tillmann, Ralf and Wegener, Robert and Hofzumahaus, Andreas and Kiendler-Scharr, Astrid and Wahner, Andreas and Fuchs, Hendrik}, title = {Atmospheric photo-oxidation of myrcene: OH reaction rate constant, gas-phase oxidation products and radical budgets}, series = {Atmospheric Chemistry and Physics}, volume = {21}, journal = {Atmospheric Chemistry and Physics}, number = {20}, publisher = {Copernicus GmbH}, issn = {1680-7324}, doi = {10.5194/acp-21-16067-2021}, pages = {16067 -- 16091}, year = {2021}, abstract = {Abstract. The photo-oxidation of myrcene, a monoterpene species emitted by plants, was investigated at atmospheric conditions in the outdoor simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a Large Reaction Chamber). The chemical structure of myrcene consists of one moiety that is a conjugated π system (similar to isoprene) and another moiety that is a triple-substituted olefinic unit (similar to 2-methyl-2-butene). Hydrogen shift reactions of organic peroxy radicals (RO2) formed in the reaction of isoprene with atmospheric OH radicals are known to be of importance for the regeneration of OH. Structure-activity relationships (SARs) suggest that similar hydrogen shift reactions like in isoprene may apply to the isoprenyl part of RO2 radicals formed during the OH oxidation of myrcene. In addition, SAR predicts further isomerization reactions that would be competitive with bimolecular RO2 reactions for chemical conditions that are typical for forested environments with low concentrations of nitric oxide. Assuming that OH peroxy radicals can rapidly interconvert by addition and elimination of O2 like in isoprene, bulk isomerization rate constants of 0.21 and 0.097 s-1 (T=298 K) for the three isomers resulting from the 3′-OH and 1-OH addition, respectively, can be derived from SAR. Measurements of radicals and trace gases in the experiments allowed us to calculate radical production and destruction rates, which are expected to be balanced. The largest discrepancies between production and destruction rates were found for RO2. Additional loss of organic peroxy radicals due to isomerization reactions could explain the observed discrepancies. The uncertainty of the total radical (ROx=OH+HO2+RO2) production rates was high due to the uncertainty in the yield of radicals from myrcene ozonolysis. However, results indicate that radical production can only be balanced if the reaction rate constant of the reaction between hydroperoxy (HO2) and RO2 radicals derived from myrcene is lower (0.9 to 1.6×10-11 cm3 s-1) than predicted by SAR. Another explanation of the discrepancies would be that a significant fraction of products (yield: 0.3 to 0.6) from these reactions include OH and HO2 radicals instead of radical-terminating organic peroxides. Experiments also allowed us to determine the yields of organic oxidation products acetone (yield: 0.45±0.08) and formaldehyde (yield: 0.35±0.08). Acetone and formaldehyde are produced from different oxidation pathways, so that yields of these compounds reflect the branching ratios of the initial OH addition to myrcene. Yields determined in the experiments are consistent with branching ratios expected from SAR. The yield of organic nitrate was determined from the gas-phase budget analysis of reactive oxidized nitrogen in the chamber, giving a value of 0.13±0.03. In addition, the reaction rate constant for myrcene + OH was determined from the measured myrcene concentration, yielding a value of (2.3±0.3)×10-10 cm3 s-1.}, language = {en} } @article{NovelliKaminskiRolletteretal.2018, author = {Novelli, Anna and Kaminski, Martin and Rolletter, Michael and Acir, Ismail-Hakki and Bohn, Birger and Dorn, Hans-Peter and Li, Xin and Lutz, Anna and Nehr, Sascha and Rohrer, Franz and Tillmann, Ralf and Wegener, Robert and Holland, Frank and Hofzumahaus, Andreas and Kiendler-Scharr, Astrid and Wahner, Andreas and Fuchs, Hendrik}, title = {Evaluation of OH and HO2 concentrations and their budgets during photooxidation of 2-methyl-3-butene-2-ol (MBO) in the atmospheric simulation chamber SAPHIR}, series = {Atmospheric Chemistry and Physics}, volume = {18}, journal = {Atmospheric Chemistry and Physics}, number = {15}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-18-11409-2018}, pages = {11409 -- 11422}, year = {2018}, abstract = {Several previous field studies have reported unexpectedly large concentrations of hydroxyl and hydroperoxyl radicals (OH and HO2, respectively) in forested environments that could not be explained by the traditional oxidation mechanisms that largely underestimated the observations. These environments were characterized by large concentrations of biogenic volatile organic compounds (BVOC) and low nitrogen oxide concentration. In isoprene-dominated environments, models developed to simulate atmospheric photochemistry generally underestimated the observed OH radical concentrations. In contrast, HO2 radical concentration showed large discrepancies with model simulations mainly in non-isoprene-dominated forested environments. An abundant BVOC emitted by lodgepole and ponderosa pines is 2-methyl-3-butene-2-ol (MBO), observed in large concentrations for studies where the HO2 concentration was poorly described by model simulations. In this work, the photooxidation of MBO by OH was investigated for NO concentrations lower than 200 pptv in the atmospheric simulation chamber SAPHIR at Forschungszentrum J{\"u}lich. Measurements of OH and HO2 radicals, OH reactivity (kOH), MBO, OH precursors, and organic products (acetone and formaldehyde) were used to test our current understanding of the OH-oxidation mechanisms for MBO by comparing measurements with model calculations. All the measured trace gases agreed well with the model results (within 15 \%) indicating a well understood mechanism for the MBO oxidation by OH. Therefore, the oxidation of MBO cannot contribute to reconciling the unexplained high OH and HO2 radical concentrations found in previous field studies.}, language = {en} } @article{RolletterKaminskiAciretal.2019, author = {Rolletter, Michael and Kaminski, Martin and Acir, Ismail-Hakki and Bohn, Birger and Dorn, Hans-Peter and Li, Xin and Lutz, Anna and Nehr, Sascha and Rohrer, Franz and Tillmann, Ralf and Wegener, Robert and Hofzumahaus, Andreas and Kiendler-Scharr, Astrid and Wahner, Andreas and Fuchs, Hendrik}, title = {Investigation of the α-pinene photooxidation by OH in the atmospheric simulation chamber SAPHIR}, series = {Atmospheric Chemistry and Physics}, volume = {19}, journal = {Atmospheric Chemistry and Physics}, number = {18}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-19-11635-2019}, pages = {11635 -- 11649}, year = {2019}, abstract = {Abstract. The photooxidation of the most abundant monoterpene, α-pinene, by the hydroxyl radical (OH) was investigated at atmospheric concentrations in the atmospheric simulation chamber SAPHIR. Concentrations of nitric oxide (NO) were below 120 pptv. Yields of organic oxidation products are determined from measured time series giving values of 0.11±0.05, 0.19±0.06, and 0.05±0.03 for formaldehyde, acetone, and pinonaldehyde, respectively. The pinonaldehyde yield is at the low side of yields measured in previous laboratory studies, ranging from 0.06 to 0.87. These studies were mostly performed at reactant concentrations much higher than observed in the atmosphere. Time series of measured radical and trace-gas concentrations are compared to results from model calculations applying the Master Chemical Mechanism (MCM) 3.3.1. The model predicts pinonaldehyde mixing ratios that are at least a factor of 4 higher than measured values. At the same time, modeled hydroxyl and hydroperoxy (HO2) radical concentrations are approximately 25 \% lower than measured values. Vereecken et al. (2007) suggested a shift of the initial organic peroxy radical (RO2) distribution towards RO2 species that do not yield pinonaldehyde but produce other organic products. Implementing these modifications reduces the model-measurement gap of pinonaldehyde by 20 \% and also improves the agreement in modeled and measured radical concentrations by 10 \%. However, the chemical oxidation mechanism needs further adjustment to explain observed radical and pinonaldehyde concentrations. This could be achieved by adjusting the initial RO2 distribution, but could also be done by implementing alternative reaction channels of RO2 species that currently lead to the formation of pinonaldehyde in the model.}, language = {en} } @article{NehrRosse2020, author = {Nehr, Sascha and Rosse, Joel}, title = {Bewertung von Rauchschutzdruckanlagen und Wassernebell{\"o}schanlagen zur Sicherstellung bauordnungsrechtlicher Schutzziele}, series = {HLH}, volume = {71}, journal = {HLH}, number = {07-08}, publisher = {VDI}, issn = {1436-5103}, doi = {10.37544/1436-5103-2020-07-08-26}, pages = {26 -- 30}, year = {2020}, abstract = {Um das Leben von Menschen und Tieren zu sch{\"u}tzen, schreibt das Baurecht brandschutztechnische Maßnahmen vor. Diese k{\"o}nnen sowohl baulich als auch anlagentechnisch umgesetzt werden. Bei der Entscheidung f{\"u}r eine konkrete brandschutztechnische Maßnahme ist neben der Sicherheit auch die Wirtschaftlichkeit ein bedeutendes Kriterium. In dieser Arbeit wird ein modellgest{\"u}tzter Vergleich der technisch anerkannten Rauchschutzdruckanlage (RDA) mit der alternativen Wassernebell{\"o}schanlage (WNLA) herangezogen zum Zweck der Kostenminimierung bei gleichzeitiger Sicherstellung bauordnungsrechtlicher Schutzziele im Bereich des Brandschutzes.}, language = {de} } @article{NehrHoesenTanabe2017, author = {Nehr, Sascha and H{\"o}sen, Elisabeth and Tanabe, Shin-ichi}, title = {Emerging developments in the standardized chemical characterization of indoor air quality}, series = {Environment International}, volume = {98}, journal = {Environment International}, publisher = {Elsevier}, issn = {0160-4120}, doi = {10.1016/j.envint.2016.09.020}, pages = {233 -- 237}, year = {2017}, language = {en} } @article{BergmannKlimekNehretal.2021, author = {Bergmann, Karl-Christian and Klimek, Ludger and Nehr, Sascha and Straff, Wolfgang and Werchan, Barbora}, title = {Allergenic pollen: is it also an indoor problem?}, series = {Allergo Journal International}, volume = {30}, journal = {Allergo Journal International}, number = {6}, publisher = {Springer Nature}, issn = {2197-0378}, doi = {10.1007/s40629-020-00161-3}, pages = {207 -- 208}, year = {2021}, language = {en} } @article{BekoeCarslawFauseretal.2020, author = {Bek{\"o}, Gabriel and Carslaw, Nicola and Fauser, Patrik and Kauneliene, Violeta and Nehr, Sascha and Phillips, Gavin and Saraga, Dikaia and Schoemaecker, Coralie and Wierzbicka, Aneta and Querol, Xavier}, title = {The past, present, and future of indoor air chemistry}, series = {Indoor Air}, volume = {30}, journal = {Indoor Air}, number = {3}, publisher = {Wiley}, issn = {0905-6947}, doi = {10.1111/ina.12634}, pages = {373 -- 376}, year = {2020}, language = {en} } @article{BergmannKlimekNehretal.2021, author = {Bergmann, Karl-Christian and Klimek, Ludger and Nehr, Sascha and Straff, Wolfgang and Werchan, Barbora}, title = {Allergene Pollen - auch ein Problem von Innenr{\"a}umen?}, series = {Allergo Journal}, volume = {30}, journal = {Allergo Journal}, number = {6}, publisher = {Springer Nature}, issn = {0941-8849}, doi = {10.1007/s15007-021-4863-0}, pages = {54 -- 55}, year = {2021}, language = {de} } @article{Nehr2021, author = {Nehr, Sascha}, title = {Hygienische Bewertung von L{\"u}ftungskonzepten in frei gel{\"u}fteten Unterrichtsr{\"a}umen durch Messungen der Luftwechselrate}, series = {Immissionsschutz}, journal = {Immissionsschutz}, number = {1}, publisher = {Erich Schmidt Verlag}, issn = {1868-7776}, doi = {10.37307/j.1868-7776.2021.01.03}, year = {2021}, language = {de} } @article{AlvarezCarslawDusanteretal.2022, author = {Alvarez, Elena G{\´o}mez and Carslaw, Nicola and Dusanter, S{\´e}bastien and Edwards, Pete and G{\´a}bor Mihucz, Viktor and Heard, Dwayne and Kleffmann, J{\"o}rg and Nehr, Sascha and Schoemacker, Coralie and Venables, Dean}, title = {Techniques for measuring indoor radicals and radical precursors}, series = {Applied Spectroscopy Reviews}, volume = {57}, journal = {Applied Spectroscopy Reviews}, number = {7}, publisher = {Informa UK Limited}, issn = {0570-4928}, doi = {10.1080/05704928.2022.2087666}, pages = {580 -- 624}, year = {2022}, abstract = {Radicals and their precursors play a central role in the chemical transformations occurring in indoor air and on indoor surfaces. Such species include OH, HO2, peroxy radicals, nitrous acid, reactive chlorine species, NO3, N2O5, Criegee intermediates, and glyoxal and methylglyoxal. Recent advances on instrumental analysis and modeling studies have demonstrated the need for a wider range of measurements of radical species and their precursors in indoor air. This work reviews measurement techniques and provides considerations for indoor measurements of several radicals and their precursors. Techniques to determine the actinic flux are also presented owing to the relevance of photolytically-initiated processes indoors. This review is also intended to provide pointers for those wanting to learn more about measurements of radicals indoors.}, language = {en} } @article{KaminskiFuchsAciretal.2017, author = {Kaminski, Martin and Fuchs, Hendrik and Acir, Ismail-Hakki and Bohn, Birger and Brauers, Theo and Dorn, Hans-Peter and H{\"a}seler, Rolf and Hofzumahaus, Andreas and Li, Xin and Lutz, Anna and Nehr, Sascha and Rohrer, Franz and Tillmann, Ralf and Vereecken, Luc and Wegener, Robert and Wahner, Andreas}, title = {Investigation of the β-pinene photooxidation by OH in the atmosphere simulation chamber SAPHIR}, series = {Atmospheric Chemistry and Physics}, volume = {17}, journal = {Atmospheric Chemistry and Physics}, number = {11}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-17-6631-2017}, pages = {6631 -- 6650}, year = {2017}, abstract = {Abstract. Besides isoprene, monoterpenes are the non-methane volatile organic compounds (VOCs) with the highest global emission rates. Due to their high reactivity towards OH, monoterpenes can dominate the radical chemistry of the atmosphere in forested areas. In the present study the photochemical degradation mechanism of β-pinene was investigated in the J{\"u}lich atmosphere simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber). One focus of this study is on the OH budget in the degradation process. Therefore, the SAPHIR chamber was equipped with instrumentation to measure radicals (OH, HO2, RO2), the total OH reactivity, important OH precursors (O3, HONO, HCHO), the parent VOC β-pinene, its main oxidation products, acetone and nopinone and photolysis frequencies. All experiments were carried out under low-NO conditions ( ≤  300 ppt) and at atmospheric β-pinene concentrations ( ≤  5 ppb) with and without addition of ozone. For the investigation of the OH budget, the OH production and destruction rates were calculated from measured quantities. Within the limits of accuracy of the instruments, the OH budget was balanced in all β-pinene oxidation experiments. However, even though the OH budget was closed, simulation results from the Master Chemical Mechanism (MCM) 3.2 showed that the OH production and destruction rates were underestimated by the model. The measured OH and HO2 concentrations were underestimated by up to a factor of 2, whereas the total OH reactivity was slightly overestimated because the model predicted a nopinone mixing ratio which was 3 times higher than measured. A new, theory-derived, first-generation product distribution by Vereecken and Peeters (2012) was able to reproduce the measured nopinone time series and the total OH reactivity. Nevertheless, the measured OH and HO2 concentrations remained underestimated by the numerical simulations. These observations together with the fact that the measured OH budget was closed suggest the existence of unaccounted sources of HO2. Although the mechanism of additional HO2 formation could not be resolved, our model studies suggest that an activated alkoxy radical intermediate proposed in the model of Vereecken and Peeters (2012) generates HO2 in a new pathway, whose importance has been underestimated so far. The proposed reaction path involves unimolecular rearrangement and decomposition reactions and photolysis of dicarbonyl products, yielding additional HO2 and CO. Further experiments and quantum chemical calculations have to be made to completely unravel the pathway of HO2 formation.}, language = {en} } @article{HerrBrennerThekokeetal.2017, author = {Herr, Caroline E. and Brenner, Bernhard and Thekoke, Jochen and Nehr, Sascha}, title = {Stand der Aktivit{\"a}ten in den VDI - Arbeitsgruppen (Gemeinschaftsausschuss „Bioaerosole und Biologische Agenzien")}, series = {Das Gesundheitswesen}, volume = {79}, journal = {Das Gesundheitswesen}, number = {4}, publisher = {Thieme}, issn = {0941-3790}, doi = {10.1055/s-0037-1602072}, pages = {299 -- 374}, year = {2017}, language = {de} } @article{NehrFranzenReuterKucejko2017, author = {Nehr, Sascha and Franzen-Reuter, Isabelle and Kucejko, Catharina}, title = {New directions: Future approaches to the standardized assessment of airborne pollutants affecting environmental quality}, series = {Atmospheric Environment}, volume = {166}, journal = {Atmospheric Environment}, publisher = {Elsevier}, issn = {1352-2310}, doi = {10.1016/j.atmosenv.2017.06.051}, pages = {570 -- 572}, year = {2017}, language = {en} } @article{HerrBrennerThekokeetal.2017, author = {Herr, Caroline E. W. and Brenner, Bernhard and Thekoke, Jochen and Nehr, Sascha and Winkler, Gisela}, title = {Erfahrung mit dem LAI Leitfaden bei der Bewertung von Bioaerosoleemissionen aus Anlagen}, series = {Das Gesundheitswesen}, volume = {79}, journal = {Das Gesundheitswesen}, number = {4}, publisher = {Thieme}, issn = {0941-3790}, doi = {10.1055/s-0037-1602110}, pages = {299 -- 374}, year = {2017}, language = {de} } @misc{NehrBorowiakHerrmannetal.2017, author = {Nehr, Sascha and Borowiak, Annette and Herrmann, Hartmut and Wiesen, P. and Zellner, Reinhard}, title = {New and emerging technologies: Impact on air quality and climate - 3rd VDI/DECHEMA/GDCh Expert Forum on Atmospheric Chemistry (EFAC 3)}, series = {Gefahrstoffe Reinhaltung der Luft}, volume = {77}, journal = {Gefahrstoffe Reinhaltung der Luft}, number = {1/2}, publisher = {Springer-VDI-Verl.}, pages = {15 -- 18}, year = {2017}, language = {de} } @misc{WalserThelokeNehretal.2017, author = {Walser, Sandra M. and Theloke, Jochen and Nehr, Sascha and Brenner, Bernhard and Herr, Caroline E. W.}, title = {Gemeinschaftsausschuss „Bioaerosole und biologische Agenzien" der VDI/DIN-Kommission Reinhaltung der Luft}, series = {Umweltmedizin - Hygiene - Arbeitsmedizin}, volume = {22}, journal = {Umweltmedizin - Hygiene - Arbeitsmedizin}, number = {2}, publisher = {ecomed-Storck}, year = {2017}, language = {de} } @inproceedings{Nehr2017, author = {Nehr, Sascha}, title = {Probleme in der Praxis der Geruchsbeurteilung - Handlungsfelder f{\"u}r die technische Regelsetzung}, series = {Ger{\"u}chte in der Umwelt: N{\"u}rnberg, 15. und 16. November 2017}, volume = {VDI-Berichte 2315}, booktitle = {Ger{\"u}chte in der Umwelt: N{\"u}rnberg, 15. und 16. November 2017}, publisher = {VDI-Verlag}, issn = {0083-5560}, pages = {171}, year = {2017}, subject = {Geruchsemission}, language = {de} } @inproceedings{Nehr2017, author = {Nehr, Sascha}, title = {Probleme in der Praxis der Geruchsbeurteilung - Handlungsfelder f{\"u}r die technische Regelsetzung}, series = {Ger{\"u}che in der Umwelt: N{\"u}rnberg, 15. und 16. November 2017}, volume = {VDI-Berichte 2315}, booktitle = {Ger{\"u}che in der Umwelt: N{\"u}rnberg, 15. und 16. November 2017}, publisher = {VDI Verlag}, address = {D{\"u}sseldorf}, organization = {VDI Wissensforum}, isbn = {978-3-18-092315-4}, issn = {0083-5560}, pages = {171 -- 180}, year = {2017}, language = {de} } @article{SaffellNehr2023, author = {Saffell, John and Nehr, Sascha}, title = {Improving Indoor Air Quality through Standardization}, series = {Standards}, volume = {3}, journal = {Standards}, number = {3}, publisher = {MDPI}, issn = {2305-6703}, doi = {10.3390/standards3030019}, pages = {240 -- 267}, year = {2023}, abstract = {Human beings experience a large fraction of their exposure to air pollutants in indoor environments. Air pollution is a large environmental health risk, and exposure to ambient air pollution and indoor air pollution contribute equally to the total number of fatalities worldwide. Although legislative authorities have established limit values for ambient outdoor air and stack emissions, there are inconsistent and variable national and regional limit values for gaseous substances and airborne particulate matter in the built environment (schools, homes, healthcare facilities, offices, and other public spaces). This lack of regulation is unsurprising, because indoor spaces are characterized by complex air chemistry, and their construction materials and types of activities vary significantly. The current understanding of indoor pollutants, including short-lived oxidants, degradation of VOCs, particle formation, and particle composition, is incomplete. It is necessary to identify and assess emerging pollutants and their toxicity, and to consider new consumer products and green construction materials and their impact on indoor air quality (IAQ). Learning from IAQ surveys and audit protocols, research methodologies should be regularized for cross-research comparisons. Some indoor air quality guidance and standards have been written, and several more are in development, with the international ISO 16000 series of indoor standards leading the way for improving indoor air data quality. The WHO has established some ambient air limit values which can mostly be translated into indoor limit values. The built environment needs to harmonize energy efficiency, thermal comfort and air quality standards and guidance. In this review, we discuss the next steps for improving international, regional and national standards and guidance, leading to better and more complete indoor air quality regulations.}, language = {en} } @article{BausNehr2022, author = {Baus, Lukas and Nehr, Sascha}, title = {Potentials and limitations of direct air capturing in the built environment}, series = {Building and Environment}, volume = {208}, journal = {Building and Environment}, publisher = {Elsevier}, issn = {0360-1323}, doi = {10.1016/j.buildenv.2021.108629}, year = {2022}, abstract = {This concept study presents an approach for resolving the trade-off between energy-efficient building operation and the provision of hygienically harmless indoor air quality. A novel coupling of HVAC-systems (heating, ventilation and air conditioning systems) with DAC-technology (direct air capturing technology) is proposed to separate CO2 in the exhaust air of buildings and recirculate the CO2-depleted air back into the building. In a mainly theoretical approach, the corresponding potentials and limitations of the novel HVAC/DAC-coupling in recirculation mode are evaluated. For that purpose, CO2-loads in the feed and exhaust air of four buildings located in Germany were measured using calibrated non-dispersive infrared (NDIR) sensors with pyroelectric detection principle. Subsequent numerical model simulations resort to typical meteorological data as well as building operation parameters grouped in different scenarios. The measurement and simulation results were assessed with regard to: (i) the unique possibilities of a HVAC/DAC-coupling in recirculation mode for the improvement of indoor air quality, (ii) the energy saving potentials through reduced air conditioning requirements enabled by a HVAC/DAC-coupling in recirculation mode, and (iii) the potential allocation of CO2 separated from building exhaust air for energetic and/or material reutilization in decentralized systems. In conclusion, a HVAC/DAC-coupling in recirculation mode can not only reduce the energy demand of buildings but also facilitates access to unutilized CO2-resources transported in the built environment and additionally offers the potential to improve indoor air quality. However, a suitable DAC module for operation in indoor air is not yet commercially available.}, language = {en} } @article{NehrDuarteAlmeidaetal.2023, author = {Nehr, Sascha and Duarte, Regina M. B. O. and Almeida, Antoine S. and Baus, Lukas and Bergmann, Karl-Christian}, title = {Assessing the relevance of allergenic pollen in indoor environments—current knowledge base and research needs}, series = {Allergo Journal International}, volume = {32}, journal = {Allergo Journal International}, number = {6}, publisher = {Springer Nature}, issn = {2197-0378}, doi = {10.1007/s40629-023-00251-y}, pages = {167 -- 175}, year = {2023}, abstract = {SummaryAirborne pollen allergens—a relevant component of bioaerosols and, therefore, of airborne particulate matter—are considered an important metric in air quality assessments. Although the measurement of airborne pollen allergen concentrations in outdoor environments (namely, in urban areas) has been recognized as a key environmental health indicator, no such obligation exists for indoor environments (dwellings or occupational settings). However, people spend most of their daily time (80-90\%) indoors, where the majority of their exposure to air pollution, including pollen allergens, occurs. Nonetheless, the relative importance of airborne pollen allergen exposure indoors differs from outdoors because of differences in pollen loads, sources, dispersion, and degree of penetration from the outdoor surroundings, as well as the differences in the allergenic pollen profiles. In this brief review, we mined the literature over the last 10 years to summarize what existing measurements reveal about the relevance of airborne allergenic pollen in indoor environments. The research priorities on this topic are presented, highlighting the challenges and the motivations for obtaining pollen data in built environments which are key to understand the extent and mechanisms of human exposure to airborne pollen allergens. Thus, we provide a comprehensive assessment of the relevance of airborne allergenic pollen in indoor environments, highlighting knowledge gaps and research needs related to their health effects.}, language = {en} } @article{BausNehrMaeda2023, author = {Baus, Lukas and Nehr, Sascha and Maeda, Nobutaka}, title = {Investigation of CO2-Sorption Characteristics of Readily Available Solid Materials for Indoor Direct Air Capturing}, series = {Indoor Air}, volume = {2023}, journal = {Indoor Air}, editor = {Ming, Ting Zhen}, publisher = {Wiley}, issn = {1600-0668}, doi = {10.1155/2023/8821044}, pages = {1 -- 8}, year = {2023}, abstract = {Direct air capturing (DAC) is an energy demanding process for CO2-removal from air. Ongoing research focuses on the potential of indoor air as DAC-feed to profit from currently unused energetic synergies between DAC and the built environment. In this work, we investigated the performance of three different readily available, solid DAC-adsorbers under typical indoor environmental conditions of 16-25°C, 25-60\% relative humidity (RH), and CO2-concentrations of less than 800 ppm above atmospheric concentrations. The measured mass-specific CO2-adsorption capacities of K2CO3-impregnated activated carbon, polyethylenimine-snow (PEI-snow), and polyethylenimine (PEI) on silica a amount to 6.5 ± 0.3 mg g-1, 52.9 ± 4.9 mg g-1, and 56.9 ± 4.2 mg g-1, respectively. Among the three investigated adsorber materials, PEI on silica is the most promising candidate for DAC-applications as its synthesis is rather simple, the CO2-desorption is feasible at moderate conditions of about 80°C at 100 mbar, and the competing co-adsorption of water does not strongly affect the CO2-adsorption under the investigated experimental conditions.}, language = {en} } @article{NehrJaeckel2023, author = {Nehr, Sascha and J{\"a}ckel, Simon}, title = {Successful Innovation Transfer through Pre-Standardization: A Case Study}, series = {Standards}, volume = {3}, journal = {Standards}, number = {1}, publisher = {MDPI}, issn = {2305-6703}, doi = {10.3390/standards3010004}, pages = {31 -- 42}, year = {2023}, abstract = {This study presents an approach to structure, analyze and evaluate corporate standardization processes using the example of pre-standardization for the reduction of environmental impacts in product design and development. For this purpose, we give a detailed description of the evolution of the European Standard EN 16524 entitled "Mechanical products—Methodology for reduction of environmental impacts in product design and development". The standardization strategy behind the evolution of EN 16524 is analyzed using the approach of a Business Model Canvas combined with an evaluation using pre-defined success factors. Moreover, we derive general recommendations for corporate standardization professionals in checklists for each field of the underlying Business Model Canvas. With regard to the case study depicted here, we come to the conclusion that pre-standards are especially suited for innovation transfer in the field of emerging and rapidly evolving scientific and technical results.}, language = {en} } @incollection{SturtevantMetzgerNehretal.2021, author = {Sturtevant, Cove and Metzger, Stefan and Nehr, Sascha and Foken, Thomas}, title = {Quality Assurance and Control}, series = {Springer Handbook of Atmospheric Measurements}, booktitle = {Springer Handbook of Atmospheric Measurements}, editor = {Foken, Thomas}, publisher = {Springer Nature}, address = {Cham}, isbn = {9783030521707}, issn = {2522-8692}, doi = {10.1007/978-3-030-52171-4_3}, pages = {49 -- 92}, year = {2021}, language = {en} } @incollection{NehrSimmler2023, author = {Nehr, Sascha and Simmler, Walter}, title = {Air, 6. Photochemical Degradation}, series = {Ullmann's Encyclopedia of Industrial Chemistry}, booktitle = {Ullmann's Encyclopedia of Industrial Chemistry}, edition = {1}, publisher = {Wiley}, isbn = {9783527303854}, doi = {10.1002/14356007.o02_o06.pub2}, pages = {1 -- 11}, year = {2023}, language = {en} } @article{FuchsAcirBohnetal.2014, author = {Fuchs, H. and Acir, Ismail-Hakki and Bohn, Birger and Brauers, Theo and Dorn, Hans-Peter and H{\"a}seler, R. and Hofzumahaus, A. and Holland, F. and Kaminski, M. and Li, X. and Lu, K. and Lutz, A. and Nehr, Sascha and Rohrer, F. and Tillmann, R. and Wegener, R. and Wahner, A.}, title = {OH regeneration from methacrolein oxidation investigated in the atmosphere simulation chamber SAPHIR}, series = {Atmospheric Chemistry and Physics}, volume = {14}, journal = {Atmospheric Chemistry and Physics}, number = {15}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-14-7895-2014}, pages = {7895 -- 7908}, year = {2014}, abstract = {Abstract. Hydroxyl radicals (OH) are the most important reagent for the oxidation of trace gases in the atmosphere. OH concentrations measured during recent field campaigns in isoprene-rich environments were unexpectedly large. A number of studies showed that unimolecular reactions of organic peroxy radicals (RO2) formed in the initial reaction step of isoprene with OH play an important role for the OH budget in the atmosphere at low mixing ratios of nitrogen monoxide (NO) of less than 100 pptv. It has also been suggested that similar reactions potentially play an important role for RO2 from other compounds. Here, we investigate the oxidation of methacrolein (MACR), one major oxidation product of isoprene, by OH in experiments in the simulation chamber SAPHIR under controlled atmospheric conditions. The experiments show that measured OH concentrations are approximately 50\% larger than calculated by the Master Chemical Mechanism (MCM) for conditions of the experiments (NO mixing ratio of 90 pptv). The analysis of the OH budget reveals an OH source that is not accounted for in MCM, which is correlated with the production rate of RO2 radicals from MACR. In order to balance the measured OH destruction rate, 0.77 OH radicals (1σ error: ± 0.31) need to be additionally reformed from each reaction of OH with MACR. The strong correlation of the missing OH source with the production of RO2 radicals is consistent with the concept of OH formation from unimolecular isomerization and decomposition reactions of RO2. The comparison of observations with model calculations gives a lower limit of 0.03 s-1 for the reaction rate constant if the OH source is attributed to an isomerization reaction of MACR-1-OH-2-OO and MACR-2-OH-2-OO formed in the MACR + OH reaction as suggested in the literature (Crounse et al., 2012). This fast isomerization reaction would be a competitor to the reaction of this RO2 species with a minimum of 150 pptv NO. The isomerization reaction would be the dominant reaction pathway for this specific RO2 radical in forested regions, where NO mixing ratios are typically much smaller.}, language = {en} } @article{NehrBohnDornetal.2014, author = {Nehr, Sascha and Bohn, Birger and Dorn, Hans-Peter and Fuchs, H. and H{\"a}seler, R. and Hofzumahaus, A. and Li, X. and Rohrer, F. and Tillmann, R. and Wahner, A.}, title = {Atmospheric photochemistry of aromatic hydrocarbons: OH budgets during SAPHIR chamber experiments}, series = {Atmospheric Chemistry and Physics}, volume = {14}, journal = {Atmospheric Chemistry and Physics}, number = {13}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-14-6941-2014}, pages = {6941 -- 6952}, year = {2014}, abstract = {Abstract. Current photochemical models developed to simulate the atmospheric degradation of aromatic hydrocarbons tend to underestimate OH radical concentrations. In order to analyse OH budgets, we performed experiments with benzene, toluene, p-xylene and 1,3,5-trimethylbenzene in the atmosphere simulation chamber SAPHIR. Experiments were conducted under low-NO conditions (typically 0.1-0.2 ppb) and high-NO conditions (typically 7-8 ppb), and starting concentrations of 6-250 ppb of aromatics, dependent on OH rate constants. For the OH budget analysis a steady-state approach was applied in which OH production and destruction rates (POH and DOH) have to be equal. The POH were determined from measurements of HO2, NO, HONO, and O3 concentrations, considering OH formation by photolysis and recycling from HO2. The DOH were calculated from measurements of the OH concentrations and total OH reactivities. The OH budgets were determined from DOH/POH ratios. The accuracy and reproducibility of the approach were assessed in several experiments using CO as a reference compound where an average ratio DOH/POH = 1.13 ± 0.19 was obtained. In experiments with aromatics, these ratios ranged within 1.1-1.6 under low-NO conditions and 0.9-1.2 under high-NO conditions. The results indicate that OH budgets during photo-oxidation experiments with aromatics are balanced within experimental accuracies. Inclusion of a further, recently proposed OH production via HO2 + RO2 reactions led to improvements under low-NO conditions but the differences were small and insignificant within the experimental errors.}, language = {en} } @article{FuchsHofzumahausRohreretal.2013, author = {Fuchs, H. and Hofzumahaus, A. and Rohrer, F. and Bohn, Birger and Brauers, Theo and Dorn, Hans-Peter and H{\"a}seler, R. and Holland, F. and Kaminski, M. and Li, X. and Lu, K. and Nehr, Sascha and Tillmann, R. and Wegener, R. and Wahner, A.}, title = {Experimental evidence for efficient hydroxyl radical regeneration in isoprene oxidation}, series = {Nature Geoscience}, volume = {6}, journal = {Nature Geoscience}, number = {12}, publisher = {Springer Nature}, issn = {1752-0894}, doi = {10.1038/NGEO1964}, pages = {1023 -- 1026}, year = {2013}, language = {en} } @article{NehrGlatkeHellacketal.2016, author = {Nehr, Sascha and Glatke, D. and Hellack, Bryan and Herrmann, Hartmut and Hoffmann, B. and Kuhlbusch, T. A. J. and Schins, Roel and Wiesen, P. and Zellner, P.}, title = {Tropospheric aerosols - Current research and future air quality policy}, series = {Gefahrstoffe, Reinhaltung der Luft}, volume = {76}, journal = {Gefahrstoffe, Reinhaltung der Luft}, number = {6}, publisher = {Springer-VDI-Verl.}, issn = {1436-4891}, pages = {231 -- 237}, year = {2016}, language = {de} } @article{ZellnerHerrmannWiesenetal.2016, author = {Zellner, R. and Herrmann, H. and Wiesen, P. and Nehr, Sascha}, title = {New and Emerging Technologies of Societal Relevance: Impact on Air Quality and Climate}, series = {Chemie Ingenieur Technik}, volume = {88}, journal = {Chemie Ingenieur Technik}, number = {9}, publisher = {Wiley}, issn = {0009-286X}, doi = {10.1002/cite.201650083}, pages = {1257 -- 1258}, year = {2016}, language = {en} } @article{NehrHermannThelokeetal.2016, author = {Nehr, Sascha and Hermann, Hartmut and Theloke, Jochen and Wiesen, Peter}, title = {NMVOCs, NOx, O3, and the EU Thematic Strategy on Air Pollution}, series = {Gefahrstoffe, Reinhaltung der Luft}, volume = {76}, journal = {Gefahrstoffe, Reinhaltung der Luft}, number = {1/2}, publisher = {Springer-VDI-Verl.}, issn = {1436-4891}, pages = {7 -- 13}, year = {2016}, language = {de} } @inproceedings{NehrTanabe2014, author = {Nehr, Sascha and Tanabe, Shin-ichi}, title = {ISO/TC 146/SC 6 - Setting international standards for the assessment of indoor air quality}, series = {Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, Hong Kong}, booktitle = {Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, Hong Kong}, address = {Hong Kong}, year = {2014}, language = {en} } @techreport{NehrHoesen2016, author = {Nehr, Sascha and H{\"o}sen, Elisabeth}, title = {Luftqualit{\"a}t in Innenr{\"a}umen: Handlungsfelder der Standardisierung und Forschungsbedarf}, publisher = {VDI}, organization = {VDI Verein Deutscher Ingenieure e.V., Kommission Reinhaltung der Luft im VDI und DIN}, year = {2016}, language = {de} } @techreport{OliveiraBritoPohlNehr2025, author = {Oliveira Brito, Marcel and Pohl, Tobias and Nehr, Sascha}, title = {Sicheres Schadstoffmonitoring per UAV in Gefahrenszenarien f{\"u}r Einsatzkr{\"a}fte (SiSchaMo): Erforschung eines modularen Sensorsystems zur dreidimensionalen Erfassung und Charakterisierung von Gefahrstoffwolken mittels UAV in-situ Messungen ; Abschlussbericht zum Teilvorhaben}, publisher = {Technische Informationsbibliothek}, address = {Hannover}, doi = {10.34657/18646}, url = {http://nbn-resolving.de/urn:nbn:de:hbz:due62-opus-55799}, pages = {40}, year = {2025}, subject = {Drohne}, language = {de} } @inproceedings{StaehlerWeyersHoffmannetal.2025, author = {St{\"a}hler, Lisa and Weyers, Simone and Hoffmann, Barbara and Soppa, Vanessa and Oberwinster, Lukas and Nehr, Sascha and Pohl, Tobias and Kuß, Oliver and Lang, Alexander and Pischke, Claudia}, title = {UNITY: Multistrategische Intervention zur F{\"o}rderung von Radmobilit{\"a}t, Gesundheit und Nachhaltigkeit im Rahmen der Stadtentwicklung D{\"u}sseldorf - Teilprojekt 1 [Poster]}, series = {60. Jahrestagung der Deutschen Gesellschaft f{\"u}r Sozialmedizin und Pr{\"a}vention (DGSMP) Teilhabe und Ko-Kreation, 17. - 19. September 2025, Berlin}, booktitle = {60. Jahrestagung der Deutschen Gesellschaft f{\"u}r Sozialmedizin und Pr{\"a}vention (DGSMP) Teilhabe und Ko-Kreation, 17. - 19. September 2025, Berlin}, year = {2025}, subject = {Stadtplanung}, language = {de} } @inproceedings{SoppaOberwinsterPischkeetal.2025, author = {Soppa, Vanessa and Oberwinster, Lukas and Pischke, Claudia and St{\"a}hler, Lisa and Weyers, Simone and Nehr, Sascha and Pohl, Tobias and Kuß, Oliver and Lang, Alexander and Hoffmann, Barbara}, title = {UNITY: Multistrategische Intervention zur F{\"o}rderung von Radmobilit{\"a}t, Gesundheit und Nachhaltigkeit im Rahmen der Stadtentwicklung D{\"u}sseldorf - Teilprojekt 2 [Poster]}, series = {60. Jahrestagung der Deutschen Gesellschaft f{\"u}r Sozialmedizin und Pr{\"a}vention (DGSMP) Teilhabe und Ko-Kreation, 17. - 19. September 2025, Berlin}, booktitle = {60. Jahrestagung der Deutschen Gesellschaft f{\"u}r Sozialmedizin und Pr{\"a}vention (DGSMP) Teilhabe und Ko-Kreation, 17. - 19. September 2025, Berlin}, year = {2025}, language = {de} } @article{CarslawBekoeLangeretal.2024, author = {Carslaw, Nicola and Bek{\"o}, Gabriel and Langer, Sarka and Schoemaecker, Coralie and Mihucz, Victor G. and Dudzinska, Marzenna and Wiesen, Peter and Nehr, Sascha and Huttunen, Kati and Querol, Xavier and Shaw, David}, title = {A new framework for indoor air chemistry measurements: Towards a better understanding of indoor air pollution}, series = {Indoor Environments}, volume = {1}, journal = {Indoor Environments}, number = {1}, publisher = {Elsevier}, issn = {2950-3620}, doi = {10.1016/j.indenv.2023.100001}, year = {2024}, language = {en} } @article{EmanuelssonHallquistKristensenetal.2013, author = {Emanuelsson, E. U. and Hallquist, M. and Kristensen, K. and Glasius, M. and Bohn, Birger and Fuchs, H. and Kammer, B. and Kiendler-Scharr, A. and Nehr, Sascha and Rubach, F. and Tillmann, R. and Wahner, A. and Wu, H.-C. and Mentel, Th. F.}, title = {Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties}, series = {Atmospheric Chemistry and Physics}, volume = {13}, journal = {Atmospheric Chemistry and Physics}, number = {5}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-13-2837-2013}, pages = {2837 -- 2855}, year = {2013}, abstract = {Abstract. Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in J{\"u}lich, Germany. In this study aromatic compounds served as examples of anthropogenic volatile organic compound (VOC) and a mixture of α-pinene and limonene as an example for biogenic VOC. Several experiments with exclusively aromatic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μg m-3. The yields (0.5 to 9\%) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Furthermore, the OH measurements in combination with the derived yields for aromatic SOA enabled application of a simplified model to calculate the chemical turnover of the aromatic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (\≈8\%) up to significant fraction (50\%) providing a suitable range to study the effect of aerosol composition on the aerosol volatility (volume fraction remaining (VFR) at 343 K: 0.86-0.94). The aromatic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of aromatic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. The SOA yields, O/C, and f44 (the mass fraction of CO2+ ions in the mass spectra which can be considered as a measure of carboxylic groups) in the mixed photo-chemical experiments could be described as linear combinations of the corresponding properties of the pure systems. For VFR there was in addition an enhancement effect, making the mixed aerosol significantly less volatile than what could be predicted from the pure systems. A strong positive correlation was found between changes in volatility and O/C with the exception during dark hours where the SOA volatility decreased while O/C did not change significantly. Thus, this change in volatility under dark conditions as well as the anthropogenic enhancement is due to chemical or morphological changes not affecting O/C.}, language = {en} } @article{LuRohrerHollandetal.2012, author = {Lu, K. D. and Rohrer, F. and Holland, F. and Fuchs, H. and Bohn, Birger and Brauers, Theo and Chang, C. C. and H{\"a}seler, R. and Hu, M. and Kita, K. and Kondo, Y. and Li, X. and Lou, S. R. and Nehr, Sascha and Shao, M. and Zeng, L. M. and Wahner, A. and Zhang, Y. H. and Hofzumahaus, A.}, title = {Observation and modelling of OH and HO2 concentrations in the Pearl River Delta 2006: a missing OH source in a VOC rich atmosphere}, series = {Atmospheric Chemistry and Physics}, volume = {12}, journal = {Atmospheric Chemistry and Physics}, number = {3}, publisher = {Copernicus}, issn = {1680-7324}, doi = {10.5194/acp-12-1541-2012}, pages = {1541 -- 1569}, year = {2012}, abstract = {Abstract. Ambient OH and HO2 concentrations were measured by laser induced fluorescence (LIF) during the PRIDE-PRD2006 (Program of Regional Integrated Experiments of Air Quality over the Pearl River Delta, 2006) campaign at a rural site downwind of the megacity of Guangzhou in Southern China. The observed OH concentrations reached daily peak values of (15-26) × 106 cm-3 which are among the highest values so far reported for urban and suburban areas. The observed OH shows a consistent high correlation with j(O1D) over a broad range of NOx conditions. The correlation cannot be reproduced by model simulations, indicating that OH stabilizing processes are missing in current models. The observed OH exhibited a weak dependence on NOx in contrast to model predictions. While modelled and measured OH agree well at NO mixing ratios above 1 ppb, a continuously increasing underprediction of the observed OH is found towards lower NO concentrations, reaching a factor of 8 at 0.02 ppb NO. A dependence of the modelled-to-measured OH ratio on isoprene cannot be concluded from the PRD data. However, the magnitude of the ratio fits into the isoprene dependent trend that was reported from other campaigns in forested regions. Hofzumahaus et al. (2009) proposed an unknown OH recycling process without NO, in order to explain the high OH levels at PRD in the presence of high VOC reactivity and low NO. Taking a recently discovered interference in the LIF measurement of HO2 into account, the need for an additional HO2 → OH recycling process persists, but the required source strength may be up to 20\% larger than previously determined. Recently postulated isoprene mechanisms by Lelieveld et al. (2008) and Peeters and M{\"u}ller (2010) lead to significant enhancements of OH expected for PRD, but an underprediction of the observed OH by a factor of two remains at low NO (0.1-0.2 ppb). If the photolysis of hydroperoxy aldehydes from isoprene is as efficient as proposed by Peeters and M{\"u}ller (2010), the corresponding OH formation at PRD would be more important than the primary OH production from ozone and HONO. While the new isoprene mechanisms need to be confirmed by laboratory experiments, there is probably need for other, so far unidentified chemical processes to explain entirely the high OH levels observed in Southern China.}, language = {en} } @article{FuchsDornBachneretal.2012, author = {Fuchs, H. and Dorn, Hans-Peter and Bachner, M. and Bohn, Birger and Brauers, Theo and Gomm, S. and Hofzumahaus, A. and Holland, F. and Nehr, Sascha and Rohrer, F. and Tillmann, R. and Wahner, A.}, title = {Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration}, series = {Atmospheric Measurement Techniques}, volume = {5}, journal = {Atmospheric Measurement Techniques}, number = {7}, publisher = {Copernicus}, issn = {1867-8548}, doi = {10.5194/amt-5-1611-2012}, pages = {1611 -- 1626}, year = {2012}, abstract = {Abstract. During recent field campaigns, hydroxyl radical (OH) concentrations that were measured by laser-induced fluorescence (LIF) were up to a factor of ten larger than predicted by current chemical models for conditions of high OH reactivity and low NO concentration. These discrepancies, which were observed in forests and urban-influenced rural environments, are so far not entirely understood. In summer 2011, a series of experiments was carried out in the atmosphere simulation chamber SAPHIR in J{\"u}lich, Germany, in order to investigate the photochemical degradation of isoprene, methyl-vinyl ketone (MVK), methacrolein (MACR) and aromatic compounds by OH. Conditions were similar to those experienced during the PRIDE-PRD2006 campaign in the Pearl River Delta (PRD), China, in 2006, where a large difference between OH measurements and model predictions was found. During experiments in SAPHIR, OH was simultaneously detected by two independent instruments: LIF and differential optical absorption spectroscopy (DOAS). Because DOAS is an inherently calibration-free technique, DOAS measurements are regarded as a reference standard. The comparison of the two techniques was used to investigate potential artifacts in the LIF measurements for PRD-like conditions of OH reactivities of 10 to 30 s-1 and NO mixing ratios of 0.1 to 0.3 ppbv. The analysis of twenty experiment days shows good agreement. The linear regression of the combined data set (averaged to the DOAS time resolution, 2495 data points) yields a slope of 1.02 ± 0.01 with an intercept of (0.10 ± 0.03) × 106 cm-3 and a linear correlation coefficient of R2 = 0.86. This indicates that the sensitivity of the LIF instrument is well-defined by its calibration procedure. No hints for artifacts are observed for isoprene, MACR, and different aromatic compounds. LIF measurements were approximately 30-40\% (median) larger than those by DOAS after MVK (20 ppbv) and toluene (90 ppbv) had been added. However, this discrepancy has a large uncertainty and requires further laboratory investigation. Observed differences between LIF and DOAS measurements are far too small to explain the unexpected high OH concentrations during the PRIDE-PRD2006 campaign.}, language = {en} } @article{FuchsBohnHofzumahausetal.2011, author = {Fuchs, H. and Bohn, Birger and Hofzumahaus, A. and Holland, F. and Lu, K. D. and Nehr, Sascha and Rohrer, F. and Wahner, A.}, title = {Detection of HO2 by laser-induced fluorescence: calibration and interferences from RO2 radicals}, series = {Atmospheric Measurement Techniques}, volume = {4}, journal = {Atmospheric Measurement Techniques}, number = {6}, publisher = {Copernicus}, issn = {1867-8548}, doi = {10.5194/amt-4-1209-2011}, pages = {1209 -- 1225}, year = {2011}, abstract = {Abstract. HO2 concentration measurements are widely accomplished by chemical conversion of HO2 to OH including reaction with NO and subsequent detection of OH by laser-induced fluorescence. RO2 radicals can be converted to OH via a similar radical reaction sequence including reaction with NO, so that they are potential interferences for HO2 measurements. Here, the conversion efficiency of various RO2 species to HO2 is investigated. Experiments were conducted with a radical source that produces OH and HO2 by water photolysis at 185 nm, which is frequently used for calibration of LIF instruments. The ratio of HO2 and the sum of OH and HO2 concentrations provided by the radical source was investigated and was found to be 0.50 ± 0.02. RO2 radicals are produced by the reaction of various organic compounds with OH in the radical source. Interferences via chemical conversion from RO2 radicals produced by the reaction of OH with methane and ethane (H-atom abstraction) are negligible consistent with measurements in the past. However, RO2 radicals from OH plus alkene- and aromatic-precursors including isoprene (mainly OH-addition) are detected with a relative sensitivity larger than 80 \% with respect to that for HO2 for the configuration of the instrument with which it was operated during field campaigns. Also RO2 from OH plus methyl vinyl ketone and methacrolein exhibit a relative detection sensitivity of 60 \%. Thus, previous measurements of HO2 radical concentrations with this instrument were biased in the presence of high RO2 radical concentrations from isoprene, alkenes or aromatics, but were not affected by interferences in remote clean environment with no significant emissions of biogenic VOCs, when the OH reactivity was dominated by small alkanes. By reducing the NO concentration and/or the transport time between NO addition and OH detection, interference from these RO2 species are suppressed to values below 20 \% relative to the HO2 detection sensitivity. The HO2 conversion efficiency is also smaller by a factor of four, but this is still sufficient for atmospheric HO2 concentration measurements for a wide range of conditions.}, language = {en} } @article{WannekNehrVahlenkampetal.2009, author = {Wannek, C. and Nehr, Sascha and Vahlenkamp, M. and Mergel, J. and Stolten, D.}, title = {Pseudo-half-cell measurements on symmetrical catalyst-coated membranes and their relevance for optimizing DMFC anodes}, series = {Journal of Applied Electrochemistry}, volume = {40}, journal = {Journal of Applied Electrochemistry}, number = {1}, publisher = {Springer Nature}, issn = {0021-891X}, doi = {10.1007/s10800-009-9960-9}, pages = {29 -- 38}, year = {2009}, language = {en} } @article{NehrBohnWahner2012, author = {Nehr, Sascha and Bohn, Birger and Wahner, Andreas}, title = {Prompt HO2Formation Following the Reaction of OH with Aromatic Compounds under Atmospheric Conditions}, series = {The Journal of Physical Chemistry A}, volume = {116}, journal = {The Journal of Physical Chemistry A}, number = {24}, publisher = {American Chemical Society (ACS)}, issn = {1089-5639}, doi = {10.1021/jp210946y}, pages = {6015 -- 6026}, year = {2012}, language = {en} } @article{NehrBohnFuchsetal.2011, author = {Nehr, Sascha and Bohn, Birger and Fuchs, Hendrik and Hofzumahaus, Andreas and Wahner, Andreas}, title = {HO2 formation from the OH + benzene reaction in the presence of O2}, series = {Physical Chemistry Chemical Physics}, volume = {13}, journal = {Physical Chemistry Chemical Physics}, number = {22}, publisher = {Royal Society of Chemistry (RSC)}, issn = {1463-9076}, doi = {10.1039/c1cp20334g}, year = {2011}, language = {en} } @article{UruciFlorouPaglioneetal.2025, author = {Uruci, Petro and Florou, Kalliopi and Paglione, Marco and Kaltsonoudis, Christos and Picquet-Varrault, B{\´e}n{\´e}dicte and Doussin, Jean-Fran{\c{c}}ois and Cazaunau, Mathieu and Leskinen, Ari and Hao, Liqing and Virtanen, Annele and Bell, David M. and Mutzel, Anke and Mothes, Falk and Herrmann, Hartmut and R{\´o}denas, Milagros and Mu{\~n}oz, Amalia and Fuchs, Hendrik and Bohn, Birger and Nehr, Sascha and Alfarra, M. Rami and Voliotis, Aristeidis and McFiggans, Gordon and Patroescu-Klotz, Iulia V. and Illmann, Niklas and Pandis, Spyros N.}, title = {Toluene photo-oxidation and secondary organic aerosol formation: EUROCHAMP-2020 multi-chamber experiments}, series = {Journal of Atmospheric Chemistry}, volume = {82}, journal = {Journal of Atmospheric Chemistry}, number = {2}, publisher = {Springer Nature}, issn = {0167-7764}, doi = {10.1007/s10874-025-09485-2}, year = {2025}, language = {en} } @inproceedings{NehrBausCınar2025, author = {Nehr, Sascha and Baus, Lukas and {\c{C}}{\i}nar, H.}, title = {L{\"u}ftung in Bildungseinrichtungen, 29. Oktober 2025, K{\"o}ln}, series = {2. K{\"o}lner Innenraum-Forum}, booktitle = {2. K{\"o}lner Innenraum-Forum}, publisher = {HYGIUM - Zentrum f{\"u}r Hygiene und Umweltmedizin GmbH}, year = {2025}, language = {de} } @article{NehrBausCınar2025, author = {Nehr, Sascha and Baus, Lukas and {\c{C}}{\i}nar, Hasan}, title = {Gute Luft in Schulen - Ein Balanceakt zwischen Gesundheitsschutz und Energieeffizienz}, series = {Gefahrstoffe Reinhaltung der Luft}, volume = {85}, journal = {Gefahrstoffe Reinhaltung der Luft}, number = {03-04}, publisher = {VDI-Verlag}, issn = {0949-8036}, doi = {10.37544/0949-8036-2025-03-04-77}, pages = {77 -- 80}, year = {2025}, language = {de} }