Hohenpeissenberg Photochemical Experiment (HOPE 2000) : measurements and photostationary state calculations of OH and peroxy radicals

Measurements of OH, total peroxy radicals, non-methane hydrocarbons (NMHCs) and various other trace gases were made at the Meteorological Observatory Hohenpeissenberg in June 2000. The data from an intensive measurement period characterised by high solar insolation (18-21 June) are analysed. The maximum midday OH concentration ranged between 4.5x106 molecules cm-3 and 7.4x106 molecules cm-3. The maximum total ROx (ROx =OH+RO+HO2+RO2) mixing ratio increased from about 55 pptv on 18 June to nearly 70 pptv on 20 and 21 June. A total of 64 NMHCs, including isoprene and monoterpenes, were measured every 1 to 6 hours. The oxidation rate of the NMHCs by OH was calculated and reached a total of over 14x106 molecules cm-3 s-1 on two days. A simple photostationary state balance model was used to simulate the ambient OH and peroxy radical concentrations with the measured data as input. This approach was able to reproduce the main features of the diurnal profiles of both OH and peroxy radicals. The balance equations were used to test the effect of the assumptions made in this model. The results proved to be most sensitive to assumptions about the impact of unmeasured volatile organic compounds (VOC), e.g. formaldehyde (HCHO), and about the partitioning between HO2 and RO2. The measured OH concentration and peroxy radical mixing ratios were reproduced well by assuming the presence of 3 ppbv HCHO as a proxy for oxygenated hydrocarbons, and a HO2/ RO2 ratio between 1:1 and 1:2. The most important source of OH, and conversely the greatest sink for peroxy radicals, was the recycling of HO2 radicals to OH. This reaction was responsible for the recycling of more than 45x106 molecules cm-3 s-1 on two days. The most important sink for OH, and the largest source of peroxy radicals, was the oxidation of NMHCs, in particular, of isoprene and the monoterpenes

The Global Atmosphere Watch reactive gases measurement network

Long-term observations of reactive gases in the troposphere are important for understanding trace gas cycles and the oxidation capacity of the atmosphere, assessing impacts of emission changes, verifying numerical model simulations, and quantifying the interactions between short-lived compounds and climate change. The World Meteorological Organization’s (WMO) Global Atmosphere Watch (GAW) program coordinates a global network of surface stations some of which have measured reactive gases for more than 40 years. Gas species included under this umbrella are ozone, carbon monoxide, nitrogen oxides, and volatile organic compounds (VOCs). There are many challenges involved in setting-up and maintaining such a network over many decades and to ensure that data are of high quality, regularly updated and made easily accessible to users. This overview describes the GAW surface station network of reactive gases, its unique quality management framework, and discusses the data that are available from the central archive. Highlights of data use from the published literature are reviewed, and a brief outlook into the future of GAW is given. This manuscript constitutes the overview of a special feature on GAW reactive gases observations with individual papers reporting on research and data analysis of particular substances being covered by the program. - See more at: http://elementascience.org/article/info:doi/10.12952/journal.elementa.000067#sthash.cHvHu0T6.dpu

Messungen von Wasserstoffperoxid und organischen Hydroperoxiden am Schauinsland im Schwarzwald: ein Beitrag zur Charakterisierung der limitierenden Faktoren bei der Ozonproduktion

Continuous measurements ofH202and organic hydroperoxides were performed at the field station Schauinsland between January 1989 and June 1991 using an ezyme catalysed fluorescence instrument. The mixing ratios were in the range of the detection limit (20 ppt) up to 4.4 ppb for ~Oz and 1.7 ppb for ROOR. Both Hz02 and ROOH show a strong seasonal variation with maximum concentrations in summer. The observed seasonal trend is in line with the photochemical formation mechanism on the one hand and the main atmospheric loss processes on the other hand. The mixing ratios ofHz02 and ROOH are strongly influenced by wet deposition. For interpretation ofthe behavior ofthese substances in gas phase, this influence has to be eliminated. This was achieved by selecting sunny periods from the whole data set. In addition, periods were selected, where production exeeds chemical losses, because then, the measured concentrations of photochemically produced species, in first approximation, should reflect their production rates. This is the case when air masses arrive at Schauinsland from the nearby city of Freiburg and Rhine valley during summer and daytime. Comparison of results of smog chamber experiments performed by Hess et al. (1992 a.b,c) with chemical box model calculations using the EURORADM mechanism (Stockwell and Kley, 1994) showed, that a positive slope in the H20/Ox ratio with increasing photochemical age is an indicator for NOx limitation of photochemical ozone production. The box model was initialized using typical NOx start concentrations and VOCINOx ratios for the Schauinsland site. Analysis ofthe measured concentration ratios ofH202 and Ox versus the photochemical age of the air masses gave the result, that a large fraction of these measurements already fall into thecategory where theozone production isNOx limited. For this analysis only data were used, where the station was influenced by fresh anthropogenic emissions from Freiburg and the Rhine Valley, i.e. the analysed air masses were exposed to anthropogenic emissions later than four hours before arrival at the site. Since the advected air mass from other wind sectors are photochemically further processed, because anthropogenic sources are more distant, it C3Jl be coneluded that at Schauinsland the photochemical ozone production is in most cases limited by the availibility ofNOx' Since Schauinsland is relative dose to a large anthropogenic pollution source, this conclusion shoud be also valid for most rural areas in Europe

Analysis of elevated springtime levels of Peroxyacetyl nitrate (PAN) at the high Alpine research sites Jungfraujoch and Zugspitze

The largest atmospheric peroxyacetyl nitrate (PAN) mole fractions at remote surface sites in the Northern Hemisphere are commonly observed during the months April and May. Different formation mechanisms for this seasonal maximum have previously been suggested: hemispheric-scale production from precursors accumulated during the winter months, increased springtime transport from up-wind continents or increased regional-scale production in the atmospheric boundary layer from recent emissions. The two high Alpine research sites Jungfraujoch (Switzerland) and Zugspitze (Germany) exhibit a distinct and consistent springtime PAN maximum. Since these sites intermittently sample air masses of free-tropospheric and boundary layer origin, they are ideally suited to identify the above-mentioned PAN formation processes and attribute local observations to these. Here we present a detailed analysis of PAN observations and meteorological conditions during May 2008 when PAN levels were especially elevated at both sites. The highest PAN concentrations were connected with anticyclonic conditions, which persisted in May 2008 for about 10 days with north-easterly advection towards the sites. A backward dispersion model analysis showed that elevated PAN concentrations were caused by the combination of favourable photochemical production conditions and large precursor concentrations in the European atmospheric boundary layer. The results suggest that the largest PAN values in spring 2008 at both sites were attributable to regional-scale photochemical production of PAN in the (relatively cold) planetary boundary layer from European precursors, whereas the contribution of inter-continental transport or free-tropospheric build-up was of smaller importance for these sites.ISSN:1680-7375ISSN:1680-736

A European-wide 222Radon and 222Radon progeny comparison study [Dataset]

Although atmospheric 222Radon (222Rn) activity concentration measurements are currently performed world-wide, they are being made by many different laboratories and with fundamentally different measurement principles, so compatibility issues can limit their utility for regional-to-global applications. Consequently, we conducted a European‐wide 222Rn/222Rn progeny comparison study in order to evaluate the different measurement systems in use, determine potential systematic biases between them, and estimate correction factors that could be applied to harmonize data for their use as a tracer in atmospheric applications. Two compact portable Heidelberg Radon Monitors (HRM) were moved around to run for at least one month at each of the nine European measurement stations included in this comparison. Linear regressions between parallel data sets were calculated, yielding correction factors rela tive to the HRM ranging from 0.68 to 1.45. A calibration bias between ANSTO (Australian Nuclear Science and Technology Organisation) two‐filter radon monitors and the HRM of ANSTO/HRM = 1.11±0.05 was found. Moreover, for the continental stations using one‐filter systems that derive atmospheric 222Rn activity concentrations from measured atmospheric progeny activity concentrations, preliminary 214Po/222Rn disequilibrium values were also estimated. Mean station-specific disequilibrium values between 0.8 at mountain sites (e.g. Schauinsland) and 0.9 at non‐mountain sites for sampling heights around 20 to 30 m above ground level were determined. The respective corrections for calibration biases and disequilibrium derived in this study need to be applied to obtain a compatible European atmospheric 222Rn data set for use in quantitative applications, such as regional model intercomparison and validation, or trace gas flux estimates with the Radon‐Tracer‐Method

A European-wide (222)radon and (222)radon progeny comparison study

Although atmospheric (222)radon (Rn-222) activity concentration measurements are currently performed worldwide, they are being made by many different laboratories and with fundamentally different measurement principles, so compatibility issues can limit their utility for regional-to-global applications. Consequently, we conducted a European-wide Rn-222 / Rn-222 progeny comparison study in order to evaluate the different measurement systems in use, determine potential systematic biases between them, and estimate correction factors that could be applied to harmonize data for their use as a tracer in atmospheric applications. Two compact portable Heidelberg radon monitors (HRM) were moved around to run for at least 1 month at each of the nine European measurement stations included in this comparison. Linear regressions between parallel data sets were calculated, yielding correction factors relative to the HRM ranging from 0.68 to 1.45. A calibration bias between ANSTO (Australian Nuclear Science and Technology Organisation) two-filter radon monitors and the HRM of ANSTO / HRM = 1.11 +/- 0.05 was found. Moreover, for the continental stations using one-filter systems that derive atmospheric Rn-222 activity concentrations from measured atmospheric progeny activity concentrations, preliminary Po-214 / Rn-222 disequilibrium values were also estimated. Mean station-specific disequilibrium values between 0.8 at mountain sites (e.g. Schauinsland) and 0.9 at non-mountain sites for sampling heights around 20 to 30m above ground level were determined. The respective corrections for calibration biases and disequilibrium derived in this study need to be applied to obtain a compatible European atmospheric Rn-222 data set for use in quantitative applications, such as regional model intercomparison and validation or trace gas flux estimates with the radon tracer method