3 research outputs found
Comparison of OH reactivity measurements in the atmospheric simulation chamber SAPHIR
Hydroxyl (OH) radical reactivity (kOH) has been measured for 18 years with different measurement techniques. In order to compare the performances of instruments deployed in the field, two campaigns were conducted performing experiments in the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich in October 2015 and April 2016. Chemical conditions were chosen either to be representative of the atmosphere or to test potential limitations of instruments. All types of instruments that are currently used for atmospheric measurements were used in one of the two campaigns. The results of these campaigns demonstrate that OH reactivity can be accurately measured for a wide range of atmospherically relevant chemical conditions (e.g. water vapour, nitrogen oxides, various organic compounds) by all instruments. The precision of the measurements (limit of detection  < 1 s−1 at a time resolution of 30 s to a few minutes) is higher for instruments directly detecting hydroxyl radicals, whereas the indirect comparative reactivity method (CRM) has a higher limit of detection of 2 s−1 at a time resolution of 10 to 15 min. The performances of the instruments were systematically tested by stepwise increasing, for example, the concentrations of carbon monoxide (CO), water vapour or nitric oxide (NO). In further experiments, mixtures of organic reactants were injected into the chamber to simulate urban and forested environments. Overall, the results show that the instruments are capable of measuring OH reactivity in the presence of CO, alkanes, alkenes and aromatic compounds. The transmission efficiency in Teflon inlet lines could have introduced systematic errors in measurements for low-volatile organic compounds in some instruments. CRM instruments exhibited a larger scatter in the data compared to the other instruments. The largest differences to reference measurements or to calculated reactivity were observed by CRM instruments in the presence of terpenes and oxygenated organic compounds (mixing ratio of OH reactants were up to 10 ppbv). In some of these experiments, only a small fraction of the reactivity is detected. The accuracy of CRM measurements is most likely limited by the corrections that need to be applied to account for known effects of, for example, deviations from pseudo first-order conditions, nitrogen oxides or water vapour on the measurement. Methods used to derive these corrections vary among the different CRM instruments. Measurements taken with a flow-tube instrument combined with the direct detection of OH by chemical ionisation mass spectrometry (CIMS) show limitations in cases of high reactivity and high NO concentrations but were accurate for low reactivity (< 15 s−1) and low NO (< 5 ppbv) conditions
Netto-Null-2050 Wegweiser - Strategische Handlungsempfehlungen und mögliche Wege für ein CO2-neutrales Deutschland bis 2050
Spätestens seit dem Pariser Klimaabkommen (UNFCCC, 2015) im Jahr 2015 ist Klimaschutz in aller
Munde. Die aktuellen Erkenntnisse des Band 1 des
6. IPCC-Sachstandsberichts (IPCC, 2021) unterstreichen diese Notwendigkeit: Der Klimawandel ist
menschengemacht. Schnelle CO2-Minderung ist
notwendiger denn je. Von der lokalen über die EU
bis zur globalen Ebene soll bis 2050 – oder sogar
schon früher – die Null unterm Strich sein: Alle
Emissionen von Kohlendioxid – und auch anderen
Treibhausgasen – sind dann so weit wie nur möglich reduziert und die CO2-Konzentration in der Atmosphäre steigt nicht mehr an. Eines ist jedoch
Fakt: Auf dem Weg dahin werden sich nicht alle
CO2-Emissionen vermeiden lassen und auch am Ende bleiben CO2-Emissionen übrig. Wie reduzieren wir also CO2 und was machen wir mit dem
„Rest“, um auf Null zu kommen? Genau darauf gibt
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