TY - JOUR A1 - Fuchs, H. A1 - Dorn, Hans-Peter A1 - Bachner, M. A1 - Bohn, Birger A1 - Brauers, Theo A1 - Gomm, S. A1 - Hofzumahaus, A. A1 - Holland, F. A1 - Nehr, Sascha A1 - Rohrer, F. A1 - Tillmann, R. A1 - Wahner, A. T1 - Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration JF - Atmospheric Measurement Techniques N2 - 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 Jülich, 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. KW - Luftreinhaltung Y1 - 2012 U6 - https://doi.org/10.5194/amt-5-1611-2012 SN - 1867-8548 VL - 5 IS - 7 SP - 1611 EP - 1626 PB - Copernicus ER - TY - JOUR A1 - Fuchs, H. A1 - Bohn, Birger A1 - Hofzumahaus, A. A1 - Holland, F. A1 - Lu, K. D. A1 - Nehr, Sascha A1 - Rohrer, F. A1 - Wahner, A. T1 - Detection of HO2 by laser-induced fluorescence: calibration and interferences from RO2 radicals JF - Atmospheric Measurement Techniques N2 - 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. KW - Luftreinhaltung Y1 - 2011 U6 - https://doi.org/10.5194/amt-4-1209-2011 SN - 1867-8548 VL - 4 IS - 6 SP - 1209 EP - 1225 PB - Copernicus ER - TY - JOUR A1 - Bergmann, Marie A1 - Haddad-Thoelke, Pascale A1 - Jeong, Haeran A1 - Kappeler, Ron A1 - Altug, Hicran A1 - Oberwinster, Lukas A1 - Boogaard, Hanna A1 - Pohl, Tobias A1 - Soppa, Vanessa A1 - Ogurtsova, Katherine A1 - Joss, Meltem Kutlar A1 - Andersen, Zorana Jovanovic A1 - Hoffmann, Barbara T1 - Systematic review and meta-analysis on the health effects of long-term exposure to ultrafine particles JF - European Respiratory Review N2 - Background Ultrafine particles (≤100 nm diameter) may have a higher toxicity than larger particles but are still not regulated nor part of routine air pollution monitoring. So far, health effects of long-term exposure to ambient ultrafine particles are not well understood, owing to a lack of exposure data and epidemiological studies. Methods We conducted a systematic review and meta-analysis on the health effects of long-term exposure to ultrafine particles, including studies published until December 2024. A meta-analysis was conducted for outcomes with at least four available effect estimates. Confidence in the body of evidence was evaluated using the Office of Health Assessment and Translation method. Results We identified 85 studies investigating various mortality, morbidity and subclinical outcomes. In meta-analyses of single-pollutant models, we found positive associations with natural mortality (hazard ratio 1.06, 95% CI 1.04–1.08) and C-reactive protein (10.14% increase (95% CI −0.51–21.99%) per 10 000 pt·cm−3 increase in long-term exposure to ultrafine particles, with low and inadequate levels of evidence, respectively. The remaining studies revealed overall limited evidence for adverse effects on a wide range of outcomes. Less than half of the studies adjusted for co-pollutants. Conclusion The evidence base on long-term health effects of ultrafine particles has increased substantially in the past decade, while the overall evidence for independent effects of long-term ultrafine particle exposure remains inadequate to low. More studies are needed to draw firm conclusions about the independent adverse effects of long-term ultrafine particles on various health end-points, with a special focus on the influence of co-pollutant adjustment. KW - Luftreinhaltung KW - Schadstoffbelastung KW - Luftverunreinigender Stoff KW - Feinstaub KW - Auswirkung Y1 - 2026 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:hbz:due62-opus-60272 SN - 1600-0617 VL - 35 IS - 179 PB - European Respiratory Society ER -