Browsing by Subject "ozone"

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  • Mortensen, Lisbeth; Weisberg, Knud V. (Suomen metsätieteellinen seura, 1981)
  • Alghamdi, Mansour A.; Al-Hunaiti, Afnan; Arar, Sharif; Khoder, Mamdouh; Abdelmaksoud, Ahmad S.; Al-Jeelani, Hisham; Lihavainen, Heikki; Hyvärinen, Antti; Shabbaj, Ibrahim I.; Almehmadi, Fahd M.; Zaidan, Martha A.; Hussein, Tareq; Dada, Lubna (2019)
    Ground level ozone (O-3) plays an important role in controlling the oxidation budget in the boundary layer and thus affects the environment and causes severe health disorders. Ozone gas, being one of the well-known greenhouse gases, although present in small quantities, contributes to global warming. In this study, we present a predictive model for the steady-state ozone concentrations during daytime (13:00-17:00) and nighttime (01:00-05:00) at an urban coastal site. The model is based on a modified approach of the null cycle of O-3 and NOx and was evaluated against a one-year data-base of O-3 and nitrogen oxides (NO and NO2) measured at an urban coastal site in Jeddah, on the west coast of Saudi Arabia. The model for daytime concentrations was found to be linearly dependent on the concentration ratio of NO2 to NO whereas that for the nighttime period was suggested to be inversely proportional to NO2 concentrations. Knowing that reactions involved in tropospheric O-3 formation are very complex, this proposed model provides reasonable predictions for the daytime and nighttime concentrations. Since the current description of the model is solely based on the null cycle of O-3 and NOx, other precursors could be considered in future development of this model. This study will serve as basis for future studies that might introduce informing strategies to control ground level O-3 concentrations, as well as its precursors' emissions.
  • Eusuf, Saad Bin (Helsingin yliopisto, 2020)
    Stress response in plants is influenced by several external and internal factors and is executed in a modular way. Environmental stimuli or stress is sensed by cellular receptors and the signal is transduced inside cell via the phospho-activation of highly conserved intracellular signaling cascades like mitogen activated protein kinase (MAPK) cascades. The signal then activates biosynthesis pathways of major stress response hormones like Salicylic acid (SA). In Arabidopsis about 90% SA is synthesized via isochorismate pathway and Isochorismate synthase 1 (ICS1) is a rate limiting enzyme in this pathway. In this study, goal was to select transgenic ICS1 (homozygous) candidate lines from parent ICS1-CFP by selective regeneration. Then, by molecular and physiological characterization of transgenic ICS1-CFP plants, the function of ICS1 phosphorylation, more specifically, impact of different photoperiods (Long day; LD and Short day; SD) and stress conditions on ICS1 activity would have resolved. However, there were no homozygous candidate line from any parent ICS1-CFP plants after several screening. Nevertheless, ozone treated stress sensitivity test was performed with heterozygous ICS1-CFP candidate plants (T2 generation). Ozone treated stress depends on stomata factor because ozone enters into plants through stomata. Therefore, stomata index analysis was performed with sid2 and WT (Col-0) phenotypes and grown in LD and SD conditions. Since, stomata number was different between LD and SD plants of both sid2 and WT phenotypes, a different method named Xanthine-Xanthine oxidase (X/XO) treatment was applied that induce oxidative stress regardless of stomata. Although, WT and sid2 had shown sensitivity to the treatment, the overall cell death percentage was very low. Lastly, our aim was to observe the impact of different photoperiods on the activation of two particular MAPKs i.e MPK3 and MPK6 under stress conditions. The phosphorylated (P-MPK3 and P-MPK6) are found abundantly in ozone treated plants as an early response. In this experiment, plants were grown in both LD and SD, stressed with both ozone and X/XO treatments, the activation of P-MPK3 and P-MPK6 was observed by protein level analysis (western blotting) in detailed time course. Although, the activation was visualized in both LD and SD plants, qualitatively the pattern was similar between day type samples and activation signal was very weak in both stress methods. In addition, anti-ICS1 antibody provided by Agrsera TM was tested for its efficiency to detect endogenous ICS1 protein in plants in two experimental set-up. Although the antibody could detect overexpressed ICS1-CFP protein in samples, it was not that efficient to detect endogenous ICS1 in any of the experiments.
  • Cui, Fuqiang; Wu, Hongpo; Safronov, Omid; Zhang, Panpan; Kumar, Rajeev; Kollist, Hannes; Salojärvi, Jarkko Tapani; Panstruga, Ralph; Overmyer, Kirk Loren (2018)
    The atmospheric pollutant ozone (O-3) is a strong oxidant that causes extracellular reactive oxygen species (ROS) formation, has significant ecological relevance, and is used here as a non-invasive ROS inducer to study plant signalling. Previous genetic screens identified several mutants exhibiting enhanced O-3 sensitivity, but few with enhanced tolerance. We found that loss-of-function mutants in Arabidopsis MLO2, a gene implicated in susceptibility to powdery mildew disease, exhibit enhanced dose-dependent tolerance to O-3 and extracellular ROS, but a normal response to intracellular ROS. This phenotype is increased in a mlo2 mlo6 mlo12 triple mutant, reminiscent of the genetic redundancy of MLO genes in powdery mildew resistance. Stomatal assays revealed that enhanced O-3 tolerance in mlo2 mutants is not caused by altered stomatal conductance. We explored modulation of the mlo2-associated O-3 tolerance, powdery mildew resistance, and early senescence phenotypes by genetic epistasis analysis, involving mutants with known effects on ROS sensitivity or antifungal defence. Mining of publicly accessible microarray data suggests that these MLO proteins regulate accumulation of abiotic stress response transcripts, and transcript accumulation of MLO2 itself is O-3 responsive. In summary, our data reveal MLO2 as a novel negative regulator in plant ROS responses, which links biotic and abiotic stress response pathways.
  • Lee, Hei Shing (Helsingin yliopisto, 2021)
    In atmospheric sciences, measurements provided by remote-sensing instruments are crucial in observing the state of atmosphere. The associated uncertainties are important in nearly all data analyses. Random uncertainties reported by satellite instruments are typically estimated by inversion algorithms (ex-ante). They can be incomplete due to simplified or incomplete modelling of atmospheric processes used in the retrievals, and thus validating random uncertainties is important. However, such validation of uncertainties (or their estimates from statistical analysis afterwards, i.e. ex-post) is not a trivial task, because atmospheric measurements are obtained from the ever-changing atmosphere. This Thesis aims to explore the structure function method – an important approach in spatial statistics – and apply it to total ozone column measurements provided by the nadir-viewing satellite instrument TROPOMI. This method allows us to simultaneously perform validation of reported ex-ante random uncertainties and to explore of local-scale natural variability of atmospheric parameters. Two-dimensional structure functions of total ozone column have been evaluated based on spatial separations in latitudinal and longitudinal directions over selected months and latitude bands. Our results have indicated that the ex-post random uncertainties estimated agree considerably well with the reported ex-ante random uncertainties, which are within 1-2 DU. Discrepancies between them are very small in general. The morphology of ozone natural variability has also been illustrated: ozone variability is minimal in the tropics throughout the year, whereas in middle latitudes and polar regions they attain maxima in local spring and winter. In every scenario, the ozone structure functions are anisotropic with a stronger variability in the latitudinal direction, except at specific seasons in polar regions where isotropic behaviour is observed. Our analysis has demonstrated that the structure function method is a remarkable and promising tool for validating random uncertainties and exploring natural variability. It has a high potential for applications in other remote sensing measurements and atmospheric model data.
  • Thölix, Laura (2018)
    Finnish Meteorological Insitute Contributions 146
    Ozone and water vapour are important trace gases in the atmosphere, where both play an important role in radiative and chemical processes. Ozone protects the Earth's biosphere, humans and materials from the harmful ultraviolet (UV) radiation. The distributions and changes of ozone and water vapour are thus important to understand. Restrictions on the production and use of ozone depleting substances (ODS) within the Montreal Protocol have stopped the growth of the ozone loss, even signs of recovery of the ozone layer have been seen. However, many ODSs are long lived in the atmosphere and it will take decades before they are removed. Stratospheric water vapour influences the polar ozone loss by controlling the formation of polar stratospheric clouds (PSC). The climate change will cool the stratosphere, which could favour the formation of PSCs. This could cause significant ozone depletion despite the lower chlorine loadings in the future stratosphere. Atmospheric models are needed for studying these phenomena, because the number of observations is limited. Also the prediction of future ozone loss requires models. In this study simulations of the middle atmosphere have been made using the FinROSE chemistry transport model (FinROSE-CTM). It is an off-line 3-dimensional model, covering the altitude range of ca. 10–80 km, including the stratosphere. The model can be used for short term case studies, as well as for decadal simulations. The FinROSE-CTM needs pre-calculated winds, temperature and surface pressure, and then calculates the chemistry and transport using the meteorology. In this study ECMWF reanalysis data and climate model data have been used. Model results have been compared to ground based and satellite observations, and the model has been shown to be suitable for polar stratospheric ozone and water vapour studies. When running the model with climate model data also future conditions can be predicted. Both observations and simulations show an increase in the water vapour concentration in the Arctic stratosphere after 2006, but around 2012 the concentration started to decrease. Model calculations suggest that this increase in water vapour is mostly explained by transport-related processes. The increase in water vapour in the presence of the low winter temperatures in the Arctic stratosphere led to more frequent occurrence of ICE PSCs in the Arctic vortex. In a recent study, we studied the effect of changes in the water vapour concentration in the tropical tropopause on Arctic ozone depletion. A change in the tropical tropopause water vapour concentration resulted in a corresponding change in the Arctic stratosphere. We found that the impact of water vapour changes on ozone loss in the Arctic polar vortex depends on the meteorological conditions. The strongest effect was in intermediately cold conditions, when added water vapour resulted in more ozone loss due to the additional PSCs and associated chlorine activation on their surface. The effect was less pronounced in cold winters because cold conditions persisted long enough for a nearly complete chlorine activation even with observed water vapour. The results show that the simulated water vapour concentration in the tropical tropopause has a significant impact on the Arctic ozone loss and deserves attention, and therefore needs to be well simulated in order to improve future projections of ozone layer recovery.
  • Nuhkat, Maris; Brosché, Mikael; Stoelzle-Feix, Sonja; Dietrich, Petra; Hedrich, Rainer; Roelfsema, M.Rob G.; Kollist, Hannes (2021)
    Plant stress signalling involves bursts of reactive oxygen species (ROS), which can be mimicked by the application of acute pulses of ozone. Such ozone-pulses inhibit photosynthesis and trigger stomatal closure in a few minutes, but the signalling that underlies these responses remains largely unknown. We measured changes in Arabidopsis thaliana gas exchange after treatment with acute pulses of ozone and set up a system for simultaneous measurement of membrane potential and cytosolic calcium with the fluorescent reporter R-GECO1. We show that within 1 min, prior to stomatal closure, O3 triggered a drop in whole-plant CO2 uptake. Within this early phase, O3 pulses (200–1000 ppb) elicited simultaneous membrane depolarization and cytosolic calcium increase, whereas these pulses had no long-term effect on either stomatal conductance or photosynthesis. In contrast, pulses of 5000 ppb O3 induced cell death, systemic Ca2+ signals and an irreversible drop in stomatal conductance and photosynthetic capacity. We conclude that mesophyll cells respond to ozone in a few seconds by distinct pattern of plasma membrane depolarizations accompanied by an increase in the cytosolic calcium ion (Ca2+) level. These responses became systemic only at very high ozone concentrations. Thus, plants have rapid mechanism to sense and discriminate the strength of ozone signals. © 2021 The Authors. New Phytologist © 2021 New Phytologist Foundation
  • Päivärinta, Sanna-mari (Finnish Meteorological Institute, 2017)
    Finnish Meteorological Institute Contributions 136
    Odd nitrogen (NOx = N + NO + NO2) in the polar regions is mainly produced in the upper atmosphere through ionization processes by solar extreme ultraviolet radiation, soft X-rays and high energy particles originating from the space. During periods of high geomagnetic activity, normally close to the solar maximum, energetic particle precipitation (EPP) provides an in-situ source of NOx also in the middle atmosphere. Understanding the behaviour of NOx in the middle atmosphere is of great importance due to its capability to act as a catalyst in chemical reaction cycles destroying ozone in the stratosphere. This work considers EPP in the form of solar proton events (SPEs). Atmospheric dynamics play an important role in determining the distributions of long-lived trace gases in the middle atmosphere. The main loss mechanism for NOx is photolysis at the upper stratospheric and mesospheric altitudes, leading to long photochemical lifetime of NOx during the dark polar winter. NOx in the middle atmosphere, also if produced in-situ due to SPEs, is therefore affected by atmospheric dynamics, and transported from the mesosphere-lower hermosphere (MLT) region down to the middle atmosphere. This descent phenomenon can be intensified in the aftermath of sudden stratospheric warmings (SSWs), which are dynamical phenomena able to affect a wide range of altitudes in the Northern polar region atmosphere. The enhanced downward transport of NOx can thus strengthen the NOx-ozone connection in the stratosphere. In this work we used both space born observations from several satellite instruments and a chemistry transport model in the examination of the SSW and SPE caused effects in the stratosphere and mesosphere. The scientific objectives of this work were to find out the individual and combined effects of SSWs and SPEs on the NOx and ozone balance in the Northern middle atmosphere, and assess the relative contributions of dynamics (SSWs) and in-situ production of NOx (SPEs) on ozone in the stratosphere. The results showed dramatic increases in NOx in the middle atmosphere, even by a factor of 50, following both periods of enhanced NOx descent in connection with SSWs and in-situ production of NOx due to SPEs. A clear long-term (order of months) decrease in stratospheric ozone (10-90 %), coinciding with the enhanced amounts of NOx, was evident and affected mostly by dynamics in the upper stratosphere. The results of this work emphasize the importance of in-situ production of NOx (SPEs) on the ozone balance in the upper stratosphere, but also the key role of dynamics (SSWs) in transporting the SPE effect to even lower altitudes and its capability to strengthen the effect.
  • Grabsztunowicz, Magda; Rantala, Marjaana; Ivanauskaite, Aiste; Blomster, Tiina; Koskela, Minna M.; Vuorinen, Katariina; Tyystjarvi, Esa; Burow, Meike; Overmyer, Kirk; Mähönen, Ari P.; Mulo, Paula (2021)
    In Arabidopsis, two leaf-type ferredoxin-NADP(+) oxidoreductase (LFNR) isoforms function in photosynthetic electron flow in reduction of NADP(+), while two root-type FNR (RFNR) isoforms catalyse reduction of ferredoxin in non-photosynthetic plastids. As the key to understanding, the function of RFNRs might lie in their spatial and temporal distribution in different plant tissues and cell types, we examined expression of RFNR1 and RFNR2 genes using beta-glucuronidase (GUS) reporter lines and investigated accumulation of distinct RFNR isoforms using a GFP approach and Western blotting upon various stresses. We show that while RFNR1 promoter is active in leaf veins, root tips and in the stele of roots, RFNR2 promoter activity is present in leaf tips and root stele, epidermis and cortex. RFNR1 protein accumulates as a soluble protein within the plastids of root stele cells, while RFNR2 is mainly present in the outer root layers. Ozone treatment of plants enhanced accumulation of RFNR1, whereas low temperature treatment specifically affected RFNR2 accumulation in roots. We further discuss the physiological roles of RFNR1 and RFNR2 based on characterization of rfnr1 and rfnr2 knock-out plants and show that although the function of these proteins is partly redundant, the RFNR proteins are essential for plant development and survival.