6 results
Search Results
Now showing 1 - 6 of 6
- ItemOverview of the international project on biogenic aerosol formation in the boreal forest (BIOFOR)(Milton Park : Taylor & Francis, 2001) Kulmala, M.; Hämeri, K.; Aalto, P.P.; Mäkelä, J.M.; Pirjola, L.; Nilsson, E. Douglas; Buzorius, G.; Rannik, Ü.; Dal Maso, M.; Seidl, W.; Hoffman, T.; Janson, R.; Hansson, H.-C.; Viisanen, Y.; Laaksonen, A.; O’dowd, C.D.Aerosol formation and subsequent particle growth in ambient air have been frequently observed at a boreal forest site (SMEAR II station) in Southern Finland. The EU funded project BIOFOR (Biogenic aerosol formation in the boreal forest) has focused on: (a) determination of formation mechanisms of aerosol particles in the boreal forest site; (b) verification of emissions of secondary organic aerosols from the boreal forest site; and (c) quantification of the amount of condensable vapours produced in photochemical reactions of biogenic volatile organic compounds (BVOC) leading to aerosol formation. The approach of the project was to combine the continuous measurements with a number of intensive field studies. These field studies were organised in three periods, two of which were during the most intense particle production season and one during a non-event season. Although the exact formation route for 3 nm particles remains unclear, the results can be summarised as follows: Nucleation was always connected to Arctic or Polar air advecting over the site, giving conditions for a stable nocturnal boundary layer followed by a rapid formation and growth of a turbulent convective mixed layer closely followed by formation of new particles. The nucleation seems to occur in the mixed layer or entrainment zone. However two more prerequisites seem to be necessary. A certain threshold of high enough sulphuric acid and ammonia concentrations is probably needed as the number of newly formed particles was correlated with the product of the sulphuric acid production and the ammonia concentrations. No such correlation was found with the oxidation products of terpenes. The condensation sink, i.e., effective particle area, is probably of importance as no nucleation was observed at high values of the condensation sink. From measurement of the hygroscopic properties of the nucleation particles it was found that inorganic compounds and hygroscopic organic compounds contributed both to the particle growth during daytime while at night time organic compounds dominated. Emissions rates for several gaseous compounds was determined. Using four independent ways to estimate the amount of the condensable vapour needed for observed growth of aerosol particles we get an estimate of 2–10×107 vapour molecules cm−3. The estimations for source rate give 7.5–11×104 cm−3 s−1. These results lead to the following conclusions: The most probable formation mechanism is ternary nucleation (water-sulphuric acid-ammonia). After nucleation, growth into observable sizes (~3 nm) is required before new particles appear. The major part of this growth is probably due to condensation of organic vapours. However, there is lack of direct proof of this phenomenon because the composition of 1–5 nm size particles is extremely difficult to determine using the present state-of-art instrumentation.
- ItemEmission fluxes and atmospheric degradation of monoterpenes above a boreal forest: Field measurements and modelling(Milton Park : Taylor & Francis, 2001) Spanke, Jörg; Rannik, Üllar; Forkel, Renate; Nigge, Walter; Hoffman, ThorstenThe contribution of monoterpenes to aerosol formation processes within and above forests is not well understood. This is also true for the particle formation events observed during the BIOFOR campaigns in Hyytiälä, Finland. Therefore, the diurnal variation of the concentrations of several biogenic volatile organic compounds (BVOCs) and selected oxidation products in the gas and particle phase were measured on selected days during the campaigns in Hyytiälä, Finland. α-pinene and Δ3-carene were found to represent the most important monoterpenes above the boreal forest. A clear vertical gradient of their concentrations was observed together with a change of the relative monoterpene composition with height. Based on concentration profile measurements of monoterpenes, their fluxes above the forest canopy were calculated using the gradient approach. Most of the time, the BVOC fluxes show a clear diurnal variation with a maximum around noon. The highest fluxes were observed for α-pinene with values up to 20 ng m−2 s−1 in summer time and almost 100 ng m−2 s−1 during the spring campaign. Furthermore, the main oxidation products from α-pinene, pinonaldehyde, and from β-pinene, nopinone, were detected in the atmosphere above the forest. In addition to these more volatile oxidation products, pinic and pinonic acid were identified in the particle phase in a concentration range between 1 and 4 ng m−3. Beside these direct measurement of known oxidation products, the chemical sink term in the flux calculations was used to estimate the amount of product formation of the major terpenes (α-pinene, β-pinene, Δ3-carene). A production rate of very low volatile oxidation products (e.g., multifunctional carboxylic) from ·OH- and O3-reaction of monoterpenes of about 1.3·104 molecules cm−3 s−1 was estimated for daylight conditions during summer time. Additionally, model calculations with the one-dimensional multilayer model CACHE were carried out to investigate the diurnal course of BVOC fluxes and chemical degradation of terpenes.
- ItemA new feedback mechanism linking forests, aerosols, and climate(München : European Geopyhsical Union, 2004) Kulmala, M.; Suni, T.; Lehtinen, K.E.J.; Dal Maso, M.; Boy, M.; Reissell, A.; Rannik, Ü.; Aalto, P.; Keronen, P.; Hakola, H.; Bäck, J.; Hoffmann, T.; Vesala, T.; Hari, P.The possible connections between the carbon balance of ecosystems and aerosol-cloud-climate interactions play a significant role in climate change studies. Carbon dioxide is a greenhouse gas, whereas the net effect of atmospheric aerosols is to cool the climate. Here, we investigated the connection between forest-atmosphere carbon exchange and aerosol dynamics in the continental boundary layer by means of multiannual data sets of particle formation and growth rates, of CO2 fluxes, and of monoterpene concentrations in a Scots pine forest in southern Finland. We suggest a new, interesting link and a potentially important feedback among forest ecosystem functioning, aerosols, and climate: Considering that globally increasing temperatures and CO2 fertilization are likely to lead to increased photosynthesis and forest growth, an increase in forest biomass would increase emissions of non-methane biogenic volatile organic compounds and thereby enhance organic aerosol production. This feedback mechanism couples the climate effect Of CO2 with that of aerosols in a novel way.
- ItemA method for detecting the presence of organic fraction in nucleation mode sized particles(München : European Geopyhsical Union, 2005) Vaattovaara, P.; Räsänen, M.; Kühn, T.; Joutsensaari, J.; Laaksonen, A.New particle formation and growth has a very important role in many climate processes. However, the overall knowlegde of the chemical composition of atmospheric nucleation mode (particle diameter, d<20 nm) and the lower end of Aitken mode particles (d≤50 nm) is still insufficient. In this work, we have applied the UFO-TDMA (ultrafine organic tandem differential mobility analyzer) method to shed light on the presence of an organic fraction in the nucleation mode size class in different atmospheric environments. The basic principle of the organic fraction detection is based on our laboratory UFO-TDMA measurements with organic and inorganic compounds. Our laboratory measurements indicate that the usefulness of the UFO-TDMA in the field experiments would arise especially from the fact that atmospherically the most relevant inorganic compounds do not grow in subsaturated ethanol vapor, when particle size is 10 nm in diameter and saturation ratio is about 86% or below it. Furthermore, internally mixed particles composed of ammonium bisulfate and sulfuric acid with sulfuric acid mass fraction ≤33% show no growth at 85% saturation ratio. In contrast, 10 nm particles composed of various oxidized organic compounds of atmospheric relevance are able to grow in those conditions. These discoveries indicate that it is possible to detect the presence of organics in atmospheric nucleation mode sized particles using the UFO-TDMA method. In the future, the UFO-TDMA is expected to be an important aid to describe the composition of atmospheric newly-formed particles.
- ItemProtein O-mannosylation in the murine brain: Occurrence of Mono-O-Mannosyl glycans and identification of new substrates(San Francisco, CA : Public Library of Science, 2016) Bartels, Markus F.; Winterhalter, Patrick R.; Yu, Jin; Liu, Yan; Lommel, Mark; Möhrlen, Frank; Hu, Huaiyu; Feizi, Ten; Westerlind, Ulrika; Ruppert, Thomas; Strahl, SabineProtein O-mannosylation is a post-translational modification essential for correct development of mammals. In humans, deficient O-mannosylation results in severe congenital muscular dystrophies often associated with impaired brain and eye development. Although various O-mannosylated proteins have been identified in the recent years, the distribution of O-mannosyl glycans in the mammalian brain and target proteins are still not well defined. In the present study, rabbit monoclonal antibodies directed against the O-mannosylated peptide YAT(α1-Man)AV were generated. Detailed characterization of clone RKU-1-3-5 revealed that this monoclonal antibody recognizes O-linked mannose also in different peptide and protein contexts. Using this tool, we observed that mono-O-mannosyl glycans occur ubiquitously throughout the murine brain but are especially enriched at inhibitory GABAergic neurons and at the perineural nets. Using a mass spectrometry-based approach, we further identified glycoproteins from the murine brain that bear single O-mannose residues. Among the candidates identified are members of the cadherin and plexin superfamilies and the perineural net protein neurocan. In addition, we identified neurexin 3, a cell adhesion protein involved in synaptic plasticity, and inter-alpha-trypsin inhibitor 5, a protease inhibitor important in stabilizing the extracellular matrix, as new O-mannosylated glycoproteins.
- ItemThe influence of cadmium stress on the content of mineral nutrients and metal-binding proteins in arabidopsis halleri(Heidelberg : Springer, 2012) Przedpełska-Wąsowicz, Ewa; Polatajko, Aleksandra; Wierzbicka, MałgorzataWe investigated the influence of cadmium stress on zinc hyperaccumulation, mineral nutrient uptake, and the content of metal-binding proteins in Arabidopsis halleri. The experiments were carried out using plants subjected to long-term cadmium exposure (40 days) in the concentrations of 45 and 225 μM Cd2+. Inductively coupled plasma-mass spectrometry, size exclusion chromatography coupled with plasma-mass spectrometry, and laser ablation inductively coupled plasma-mass spectrometry used for ablation of polyacylamide gels were employed to assess the content of investigated elements in plants as well as to identify metal-binding proteins. We found that A. halleri is able to translocate cadmium to the aerial parts in high amounts (translocation index >1). We showed that Zn content in plants decreased significantly with the increase of cadmium content in the growth medium. Different positive and negative correlations between Cd content and mineral nutrients were evidenced by our study. We identified more than ten low-molecular-weight (<100 kDa) Cd-binding proteins in Cd-treated plants. These proteins are unlikely to be phytochelatins or metallothioneins. We hypothesize that low-molecular-weight Cd-binding proteins can be involved in cadmium resistance in A. halleri.