Search results for "Ozone"

Identification and climatology of cut-off lows near the tropopause.

2008

Cut-off low pressure systems (COLs) are defined as closed lows in the upper troposphere that have become completely detached from the main westerly current. These slow-moving systems often affect the weather conditions at the earth's surface and also work as a mechanism of mass transfer between the stratosphere and the troposphere, playing a significant role in the net flow of tropospheric ozone. In the first part of this work we provide a comprehensive summary of results obtained in previous studies of COLs. Following this, we present three long-term climatologies of COLs. The first two climatologies are based on the conceptual model of a COL, using European Centre for Medium-range Weather…

Impact of elevated ozone on chlorophyll a fluorescence in field-grown oat (Avena sativa).

2001

Oat (Avena sativa) plants were grown in the field near the urban area of Valencia, Eastern Spain. The data on air quality showed that ozone was the main phytotoxic pollutant present in ambient air reaching a 7-h mean of 46 nl l(-1) and a maximum hourly peak of 322 nl l(-1). The effect of ambient ozone on PSII activity was examined by measurements of chlorophyll (Chl) a fluorescence. In leaves with visible symptoms, the function of PSII was changed at high actinic irradiances. Nonphotochemical quenching (NPQ) was higher and quantum efficiency of PSII (Phi(PSII)), photochemical quenching (q(p)), quantum efficiency of excitation capture and PSII electron flow (F(v)'/F(m)') were lower. An enhan…

Interactions between nitrogen fertilization and ozone in watermelon cultivar Reina de Corazones in open-top chambers. Effects on chlorophyll alpha fl…

2006

Watermelon (Citrillus lanants) plants were grown for two consecutive years in open-top chambers with three different ozone concentrations (O-3-free air, O-3 ambient, and air with additional O-3; CFA, NFA, and NFA+O-3) and three nitrogen fertilizer concentrations [0, 14.0, and 29.6 g N per pot; N0, N1, and N2). There was an interaction between ozone and N fertilizer for the major parameters studied. O-3 and N2 treatments led to a significant decrease in maximum efficiency of photosystem 2 (PS2) photochemistry (F-v/F-m), and induced a significant decrease in the actual quantum yield of PS2 (Phi(PS2)), due mainly to the increased closure of PS2 reaction centres (q(P)) and to an increase in the…

Effects of ozone on photosynthetic CO2 exchange, chlorophyll a fluorescence and antioxidant systems in lettuce leaves

2002

The effects of ozone exposure on lettuce leaves were investigated by means of gas exchange, modulated chlorophyll a fluorescence and antioxidants systems. High ozone concentration decreased the rate of photosynthesis at light saturation level and changes in stomatal conductance and transpiration rate. However, an increase in intercellular CO 2 concentration indicated a decrease in the carboxylation efficiency. These data agreed with a reduction of non-cyclic electron flow and lower capacity to reduce the quinone pool. Ozone affected the ascorbate pool and decreased ascorbate peroxidase activity, increased lipid peroxidation, altered membrane properties and reduced the development of non-pho…

Responses of citrus plants to ozone: leaf biochemistry, antioxidant mechanisms and lipid peroxidation.

2006

The effects of ozone upon 3-year-old trees of Clementina mandarin (Citrus clementina Hort. ex Tan.) cv. Marisol exposed for 12 months to ambient (10 nl l(-1)) and high (30 and 65 nl l(-1)) concentrations in open top chambers (OTCs) were investigated. The data showed that in leaves, ozone reduced total chlorophylls, carotenoid and carbohydrate concentration. and increased 1-aminocyclopropane-1-carboxylic acid (ACC) content and ethylene production. In treated plants, the ascorbate leaf pool was decreased, while lipid peroxidation and Solute leakaGe were significantly higher than in ozone-free controls. The data indicated that ozone triggered protective mechanisms against oxidative stress in c…

Chlorophyll a fluorescence, antioxidant enzymes and lipid peroxidation in tomato in response to ozone and benomyl

2001

Ozone is a widely distributed phytotoxic air pollutant and is known to reduce the yield of several important agricultural crops in Spain. However, benomyl has been found to lessen the adverse impact of ozone on plants. We studied the effects of ozone and benomyl on chlorophyll a fluorescence, antioxidant enzymes, and lipid peroxidation in tomato (Lycopersicon esculentum Mill. cv. Tiny Tim) grown in open-top chambers in the field. Our results indicate that benomyl prevented the peroxidation of membrane lipids and increased protection of PSII from ozone. There was also a significant reduction in the activity of the antioxidant enzyme superoxide dismutase in ozone-exposed plants that had not b…

Scientific approach for ozone absorption in blood during systemic indirect endovenous ozonetherapy

2018

Introduction.
 Reading reference ozone books from Dra. Menendez, Dra. Viebhan, Dra. Borrelli and Dr. Bocci, proper timing for mixing ozone in blood during autohemotherapy is not calculated in a scientific way, having only an estimation of it based on changes in the blood color, more related to oxygen absorption than on ozone itself.
 
 Material and methods.
 We decided to reproduce a reduced model of great autohemotherapy or recently renamed as systemic indirect endovenous ozonotherapy (SIEVO) by the World Federation of Ozone Therapy – WFOT, using syringes to simplify the experiment. Our model consisted of a 20 mL syringe filled with 10 mL of blood withdrawn from healthy…

2017

Abstract. Polycyclic aromatic hydrocarbons (PAHs) are hazardous pollutants, with increasing emissions in pace with economic development in East Asia, but their distribution and fate in the atmosphere are not yet well understood. We extended the regional atmospheric chemistry model WRF-Chem (Weather Research Forecast model with Chemistry module) to comprehensively study the atmospheric distribution and the fate of low-concentration, slowly degrading semivolatile compounds. The WRF-Chem-PAH model reflects the state-of-the-art understanding of current PAHs studies with several new or updated features. It was applied for PAHs covering a wide range of volatility and hydrophobicity, i.e. phenanth…

Regional and seasonal radiative forcing by perturbations to aerosol and ozone precursor emissions

2016

Abstract. Dedicated model simulations by four general circulation and chemistry-transport models are used to establish a matrix of specific radiative forcing, defined as the radiative forcing per unit change in mass emitted, as a function of the near-term climate forcer emitted, its source region, and the season of emission. Emissions of eight near-term climate forcers are reduced: sulphur dioxide, the precursor to sulphate aerosols; black carbon aerosols; organic carbon aerosols; ammonia, a precursor to nitrate aerosols; methane; and nitrogen oxides, carbon monoxide, and volatile organic compounds, the precursors to ozone and to secondary organic aerosols. The focus is on two source region…

The impact of overshooting deep convection on local transport and mixing in the tropical upper troposphere/lower stratosphere (UTLS)

2015

Abstract. In this study we examine the simulated downward transport and mixing of stratospheric air into the upper tropical troposphere as observed on a research flight during the SCOUT-O3 campaign in connection to a deep convective system. We use the Advanced Research Weather and Research Forecasting (WRF-ARW) model with a horizontal resolution of 333 m to examine this downward transport. The simulation reproduces the deep convective system, its timing and overshooting altitudes reasonably well compared to radar and aircraft observations. Passive tracers initialised at pre-storm times indicate the downward transport of air from the stratosphere to the upper troposphere as well as upward tr…