J. Kesselmeier

Global budget of atmospheric carbonyl sulfide: Temporal and spatial variations of the dominant sources and sinks

[1] The spatial and temporal variability of the global fluxes of carbonyl sulfide (COS) is discussed together with possible implications for total column atmospheric COS loading. The input of COS into the atmosphere is calculated as the sum of all known direct sources of COS plus the conversion of carbon disulfide (CS 2 ) and dimethyl sulfide (DMS) to COS by atmospheric oxidation processes. Recent models are used to predict COS, CS 2 , and DMS release from the oceans and COS uptake by soils, plants, and oceans. This forward approach to constructing global integrated COS fluxes has a large associated range of uncertainty. The best guess global annual-integrated COS net flux estimate does not differ from zero within the range of estimated uncertainty, consistent with the observed absence of long-term trends in atmospheric COS loading. Interestingly, the hemispheric time-dependent monthly fluxes are very close in phase for the Northern and Southern Hemispheres. The monthly variation of the Northern Hemisphere flux seems to be driven primarily by high COS vegetation uptake in summer, while the monthly variation of the Southern Hemisphere flux appears to be driven mostly by high oceanic fluxes of COS, CS 2 , and DMS in summer.

Emissions of volatile organic compounds from Quercus ilex L. measured by Proton Transfer Reaction Mass Spectrometry under different environmental conditions.

Volatile organic compound (VOC) emissions of the Mediterranean holm oak (Quercus ilex L.) were investigated using a fast Proton Transfer Reaction Mass Spectrometry (PTR-MS) instrument for analysis. This technique is able to measure compounds with a proton affinity higher than water with a high time resolution of 1 s per compound. Hence nearly all VOCs can be detected on-line. We could clearly identify the emission of methanol, acetaldehyde, ethanol, acetone, acetic acid, isoprene, monoterpenes, toluene, and C10-benzenes. Some other species could be tentatively denominated. Among these are the masses 67 (cyclo pentadiene), mass 71 (tentatively attributed to methyl vinyl ketone (MVK) and metacrolein (MACR)), 73 (attributed to methyl ethyl ketone (MEK)), 85 (C6H12 or hexanol), and 95 (vinylfuran or phenol). The emissions of all these compounds (identified as well as nonidentified) together represent 99% of all masses detected and account for a carbon loss of 0.7–2.9% of the net photosynthesis. Of special interest was a change in the emission behavior under changing environmental conditions such as flooding or fast light/dark changes. Flooding of the root system caused an increase of several VOCs between 60 and 2000%, dominated by the emission of ethanol and acetaldehyde, which can be explained by the well described production of ethanol under anoxic conditions of the root system and the recently described subsequent transport and partial oxidation to acetaldehyde within the green leaves. However, ethanol emissions were dominant. Additionally, bursts of acetaldehyde with lower ethanol emission were also found under fast light/dark changes. These bursts are not understood.

Controlling variables for the uptake of atmospheric carbonyl sulfide by soil

Soil samples from arable land were investigated for their exchange of carbonyl sulfide (COS) with the atmosphere under controlled conditions using dynamic cuvettes in a climate chamber. The investigated soil type acted as a significant sink for the trace gas COS. Atmospheric COS mixing ratios, temperature, and soil water content were found to be the physicochemical parameters controlling the uptake. Emission was never observed under conditions representative of a natural environment. The observed compensation point (i.e., an ambient concentration where the consumption and production balance each other and the net flux is zero) for the uptake was about 53 parts per trillion. Uptake rates ranged between 1.5 and 10.3 pmol m−2 s−1. The consumption of COS by the soil sample depended on the physiological activity of the microorganisms in the soil, as indicated by a clear optimum temperature and by a drastic inhibition in the presence of the enzyme inhibitor 6-ethoxy-2-benzothiazole-2-sulfonamide (EZ), a specific inhibitor for carbonic anhydrase.

Net ecosystem fluxes of isoprene over tropical South America inferred from Global Ozone Monitoring Experiment (GOME) observations of HCHO columns

Click Here JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, D20304, doi:10.1029/2008JD009863, 2008 for Full Article Net ecosystem fluxes of isoprene over tropical South America inferred from Global Ozone Monitoring Experiment (GOME) observations of HCHO columns Michael P. Barkley, 1 Paul I. Palmer, 1 Uwe Kuhn, 2,3 Juergen Kesselmeier, 2 Kelly Chance, 4 Thomas P. Kurosu, 4 Randall V. Martin, 4,5 Detlev Helmig, 6 and Alex Guenther 7 Received 24 January 2008; revised 17 June 2008; accepted 22 July 2008; published 17 October 2008. [ 1 ] We estimate isoprene emissions over tropical South America during 1997–2001 using column measurements of formaldehyde (HCHO) from the Global Ozone Monitoring Experiment (GOME) satellite instrument, the GEOS-Chem chemistry transport model, and the MEGAN (Model of Emissions of Gases and Aerosols from Nature) bottom-up isoprene inventory. GEOS-Chem is qualitatively consistent with in situ ground-based and aircraft concentration profiles of isoprene and HCHO, and GOME HCHO column data (r = 0.41; bias = +35%), but has less skill in reproducing wet season observations. Observed variability of GOME HCHO columns over South America is determined largely by isoprene and biomass burning. We find that the column contributions from other biogenic volatile organic compounds (VOC) are typically smaller than the column fitting uncertainty. HCHO columns influenced by biomass burning are removed using Along Track Scanning Radiometer (ATSR) firecounts and GOME NO 2 columns. We find that South America can be split into eastern and western regions, with fires concentrated over the eastern region. A monthly mean linear transfer function, determined by GEOS-Chem, is used to infer isoprene emissions from observed HCHO columns. The seasonal variation of GOME isoprene emissions over the western region is broadly consistent with MEGAN (r = 0.41; bias = 25%), with largest isoprene emissions during the dry season when the observed variability is consistent with knowledge of temperature dependence. During the wet season, other unknown factors play a significant role in determining observed variability. Citation: Barkley, M. P., P. I. Palmer, U. Kuhn, J. Kesselmeier, K. Chance, T. P. Kurosu, R. V. Martin, D. Helmig, and A. Guenther (2008), Net ecosystem fluxes of isoprene over tropical South America inferred from Global Ozone Monitoring Experiment (GOME) observations of HCHO columns, J. Geophys. Res., 113, D20304, doi:10.1029/2008JD009863. 1. Introduction [ 2 ] Tropical terrestrial ecosystems are a significant source of biogenic volatile organic compounds (BVOCs). The dominant nonmethane BVOC is isoprene (C 5 H 8 ), which represents almost half of the global annual nonmethane VOC flux [Guenther et al., 1995, 2006]. Tropical ecosystems contribute nearly 75% of the global atmospheric isoprene School of GeoSciences, University of Edinburgh, Edinburgh, UK. Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany. Now at Agroscope Reckenholz-Taenikon Research Station, Zurich, Switzerland. Atomic and Molecular Physics Division, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA. Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada. INSTAAR, University of Colorado, Boulder, Colorado, USA. Biosphere-Atmosphere Interactions Group, Atmospheric Chemistry Division, NCAR, Boulder, Colorado, USA. Copyright 2008 by the American Geophysical Union. 0148-0227/08/2008JD009863

Exchange of short‐chain monocarboxylic acids by vegetation at a remote tropical forest site in Amazonia

09.00 budget [Guenther et al., 2006], reflecting a year-long growing season, warm temperatures, and high solar insola- tion. The high VOC loading and favorable atmospheric conditions (high concentrations of the hydroxyl radical, OH) ensures that the tropics also exert considerable influ- ence on global tropospheric photochemistry [Andreae and Crutzen, 1997]. Isoprene has a strong influence on the oxidation capacity of the atmospheric boundary layer [Poisson et al., 2000; Monson and Holland, 2001], and can contribute to the formation of tropospheric ozone [Wang and Shallcross, 2000; Sanderson et al., 2003] and be a precursor of secondary organic aerosol [Claeys et al., 2004; Henze and Seinfeld, 2006], thereby playing a signif- icant role in determining Earth’s climate. Isoprene emis- sions also represent a significant loss of fixed carbon from the terrestrial biosphere, relative to the net biome produc- tivity [Kesselmeier et al., 2002a]. [ 3 ] Global and regional isoprene emissions, determined by bottom-up models constrained by sparse in situ data, are poorly known [Guenther et al., 1995, 2006; Potter et al., D20304 1 of 24

Environmental variables controlling the uptake of carbonyl sulfide by lichens

[1] As part of the project LBA-EUSTACH (European Studies on Trace gases and Atmospheric Chemistry as a contribution to the Large-Scale Biosphere-Atmosphere experiment in Amazonia), the exchange of formic acid and acetic acid between vegetation and the atmosphere was investigated in the wet-to-dry season transition and the dry-to-wet season transition periods in 1999 in Rondonia, Brazil. Direct exchange measurements on the branch level mainly exhibited uptake of formic acid and acetic acid for all plant species in both seasons, although diel, seasonal, and interspecies variations were observed. Even though other physiological and physico-chemical parameters may have contributed, the uptake of organic acids was found to be primarily a function of the ambient atmospheric mixing ratios. The linear dependence suggests a bidirectional exchange behavior of the plants and calculated deposition velocities (0.17-0.23 cm s -1 ), compensation point mixing ratios (0.16-0.30 ppb), and potential emission rates under purified air conditions (0.013-0.031 nmol m -2 s -1 ) are discussed. Vertical profile measurements in and above the primary forest canopy further strengthened the assumption that the forest is rather a sink than a source for organic acids. The generally lower mixing ratios observed within the canopy were indicative of an uptake by vegetation and/or the soil surface. Continuous measurements of the ambient atmospheric mixing ratios at the canopy top revealed strong diel variations in both seasons and a marked seasonality with higher mixing ratios during the dry season, both being mirrored in the variation of observed uptake rates of the plants. High atmospheric concentrations during the dry season were attributed to biomass burning. During the wet season, when biomass burning activity was low, indirect emission by the vegetation, i.e., photochemical oxidation of primarily emitted biogenic reactive hydrocarbons, was assumed to dominantly contribute to the atmospheric burden of the organic acids. The high degree of correlation between atmospheric formic acid and acetic acid indicated that similar atmospheric processes were affecting their mixing ratios.

Unexpected seasonality in quantity and composition of Amazon rainforest air reactivity

The uptake of atmospheric carbonyl sulfide (COS) by the lichen species Ramalina menziesii, representative for the open oak woodland in central California, was studied under laboratory conditions. By use of a dynamic cuvette system, the controlling parameters for the COS uptake were investigated under climate chamber conditions. The thallus water content, essential for the overall physiology of lichens, was found to be of basic importance for the trace gas exchange. A water content of 30% was the approximate minimum for COS uptake, with increasing activity up to a water content of 200%. Additionally, actual atmospheric mixing ratios have a significant influence on the exchange. The COS uptake was found to be a linear function of the ambient COS mixing ratio resulting in a compensation point as low as 37 ppt. A temperature optimum of 25°C was indicative of a physiological basis of the COS uptake. The inhibition of the COS consumption in the presence of a specific inhibitor for the enzyme carbonic anhydrase proved this enzyme to be of key relevance for the uptake. All these variables controlling the COS deposition were integrated into an uptake algorithm to model the exchange behavior of this lichen. The applicability of the model to field data is demonstrated. Uptake rates on a dry weight basis normalized to optimized conditions (25°C; 450 ppt COS) reached 0.17±0.09 pmol g−1 s−1 (i.e. 4.2±2.2 pmol m−2 s−1 thallus surface area, respectively). The contribution of lichens to the global COS sink strength is assigned to be about 0.3 Tg a−1, representing not a major but a significant sink.

Dimethyl sulfide in the Amazon rain forest

The hydroxyl radical (OH) removes most atmospheric pollutants from air. The loss frequency of OH radicals due to the combined effect of all gas-phase OH reactive species is a measureable quantity termed total OH reactivity. Here we present total OH reactivity observations in pristine Amazon rainforest air, as a function of season, time-of-day and height (0–80 m). Total OH reactivity is low during wet (10 s−1) and high during dry season (62 s−1). Comparison to individually measured trace gases reveals strong variation in unaccounted for OH reactivity, from 5 to 15% missing in wet-season afternoons to mostly unknown (average 79%) during dry season. During dry-season afternoons isoprene, considered the dominant reagent with OH in rainforests, only accounts for ∼20% of the total OH reactivity. Vertical profiles of OH reactivity are shaped by biogenic emissions, photochemistry and turbulent mixing. The rainforest floor was identified as a significant but poorly characterized source of OH reactivity.

Global uptake of carbonyl sulfide (COS) by terrestrial vegetation: Estimates corrected by deposition velocities normalized to the uptake of carbon dioxide (CO 2 )

Surface-to-atmosphere emissions of dimethyl sulfide (DMS) may impact global climate through the formation of gaseous sulfuric acid, which can yield secondary sulfate aerosols and contribute to new particle formation. While oceans are generally considered the dominant sources of DMS, a shortage of ecosystem observations prevents an accurate analysis of terrestrial DMS sources. Using mass spectrometry, we quantified ambient DMS mixing ratios within and above a primary rainforest ecosystem in the central Amazon Basin in real-time (2010–2011) and at high vertical resolution (2013–2014). Elevated but highly variable DMS mixing ratios were observed within the canopy, showing clear evidence of a net ecosystem source to the atmosphere during both day and night in both the dry and wet seasons. Periods of high DMS mixing ratios lasting up to 8 h (up to 160 parts per trillion (ppt)) often occurred within the canopy and near the surface during many evenings and nights. Daytime gradients showed mixing ratios (up to 80 ppt) peaking near the top of the canopy as well as near the ground following a rain event. The spatial and temporal distribution of DMS suggests that ambient levels and their potential climatic impacts are dominated by local soil and plant emissions. A soil source was confirmed by measurements of DMS emission fluxes from Amazon soils as a function of temperature and soil moisture. Furthermore, light- and temperature-dependent DMS emissions were measured from seven tropical tree species. Our study has important implications for understanding terrestrial DMS sources and their role in coupled land-atmosphere climate feedbacks.