Photochemical pollution indicators--an analysis of 12 European monitoring stations.

Indicators were devised to classify air pollution monitoring sites according to the type of expected photochemical pollution. The indicators are based on measured ozone volume fractions, the most frequently monitored component of photochemical pollution, and in particular on two contributions: one due to the ratio of daily maximum-to-minimum ozone volume fractions and the other to observed peak values. The two contributions regarded as independent are logically connected by "and" and therefore mathematically combined by multiplication. The criterion of classification is mainly described by the mentioned ratio and incidences of ozone volume fractions exceeding the limit of 80 ppb. Twelve monitoring stations within the European network (Cooperative programme for monitoring and evaluation of long-range transmission of air pollutants in Europe, EMEP) were classified according to this indicator predicting what ozone levels can be expected at the particular sites during the growth season (April through September) into three groups: clean, medium, and polluted, based on the data for the 7 years (1997 to 2003).

Electron ionisation induced fragmentation of fused norbornene analogues containing SiMe2 or GeMe2 and oxygen bridges. Migration of SiMe2 and GeMe2 groups.

The main electron ionisation induced fragmentation processes of fused norbornene analogues containing SiMe2 or GeMe2 and oxygen bridges, as well as their dependence on substitution, were investigated using mass (MS) and tandem mass (MS/MS) spectrometric analysis. Formation of the rearrangement ions of m/z 176 in the mass spectra of fused norbornene analogues containing SiMe2 and m/z 222 in the mass spectrum of norbornene analogues containing GeMe2 provides firm evidence for the migration of a SiMe2 and GeMe2 bridge, respectively.

Kinetics of heterogeneous ozone reactions.

Earlier results on ozone destruction on solid surfaces gave apparent first order kinetics. Estimating the reaction kinetics from our data on ozone destruction on various powders (silica-gel, alumina, wood ash, coal ash, Saharan sand, calcite), we found that only calcite and wood ash exhibited such a behaviour. Removal of ozone by other powders used showed two straight lines in ln c-t plot with two different half-lives, t'(1/2) < t''(1/2). Comparing the kinetic constants for ozone removal on silica-gel and that of ozone reactions with polynuclear aromatic hydrocarbons (PAHs) adsorbed in submonolayer coverage on the same powder, the first reaction seems to be more likely in the case of pyrene and particularly fluoranthene. Enhanced ozone destruction on airborne aerosols could be an additional reason for fluoranthene stability in the real atmosphere.

Gas phase reaction rate measurements in Fourier transform mass spectrometry.

Determination of the concentration of neutral polycyclic aromatic hydrocarbon molecules in the mass spectrometer for reaction rate measurement is investigated. Copyright 1999 John Wiley & Sons, Ltd.

On the mechanism of HOONO to HONO2 conversion.

We have conducted an examination (using density functional theory) of possible transition states that could lead to HNO3 from peroxynitrous acid (HOONO) and one or two water molecules. We find no transition states with free energies in the range of 20 kcal/mol, i.e., near the experimental value in solution. The implications for the mechanism of conversion of HOONO to nitrate are discussed.

Spectroscopic investigations of dehydroepiandrosterone. Part II: Photoelectron spectrum and electronic structure.

The gas phase electronic structure of dehydroepiandrosterone (3 beta-hydroxy-5 alpha-androstene-17-one, DHEA) is elucidated from its Het photoelectron spectrum, quantum chemical calculations, and correlation with spectra of the related molecules 5 alpha-androstene-17-one (I) and epiandrosterone (3 beta-hydroxy-5 alpha-androstane-17-one) (2). The lowest ionization energy event in DHEA is shown to correspond to a pi-ionization energy of approximately 8.5 eV, followed closely and overlapped in part by the carbonyl lone pair ionization at 8.7 eV.

[Man, the environment and ozone]. / Covjek, okolis i ozon.

Ozone is a naturally occurring gas, formed in the trimolecular reaction of oxygen atoms with molecular oxygen. Its strong absorption in the UV region provides protection from excessive irradiation of the Earth's surface. Occupational exposure to ozone involves electric arc welding, mercury vapour lamps, office photocopy machines, X-ray generators and other high voltage electrical equipment, water purification and bleaching. Ozone is the most abundant oxidant in the photochemical smog. The lung cell injury induced by ozone involves a complex biochemical mechanism which is due to free radical generation. Moderate exposure produces upper respiratory tract symptoms and eye irritation, severe acute exposure results in pulmonary oedema. Measurements of atmospheric ozone concentrations in Croatia began at the end of the 19th century; continuous monitoring has been carried out since 1975.

Lesion spectra: radiation signatures and biological gateways.

We describe an integrative approach to the modeling of biophysical radiation effects. The model takes aim at practical applications of the knowledge provided by molecular studies of radiation-matter interactions in DNA. The central proposition is the idea that the distribution of molecular lesions (i.e., a molecular lesion spectrum, MLS) generated in DNA by exposure to a particular radiation is a characteristic of that causal radiation (i.e., is a radiation signature, RS). We have found that adaptive neural networks (ANN's) provide an efficient way to validate that proposition and that ANN's are also likely to be invaluable in any attempt to correlate cancers with radiation types (i.e., with RS's), to use RS's for evaluating individual carcinogenic susceptibilities, and to develop a low-dose personalized monitoring capability. Although efforts to identify products of radiation that are specific to radiation type and to link those with biological responses are almost a century old, the RS concept has provided the first quantitative confirmation of such causal relations. That is, RS's and radiation markers have been identified for various types of radiation, electromagnetic (EM) and particulate, and these signatures and markers may constitute a new way for fast radiation exposure estimates, risk assessment, and cumulative low-dose evaluation. In this work, while we will present a short review of the concepts and methods related to both RS's and markers, almost the entire effort will relate to the modeling and interpretation of RS's using ANN processing.

[Toxicology of polycyclic aromatic hydrocarbons and the mutagenicity of the air]. / Toksikologija policiklickih aromatskih ugljikovodika i mutagenost atmosfere.

Toxicological properties of polynuclear aromatic hydrocarbons (PAH) and their derivatives concerning their carcinogenicity, embryotoxicity and phototoxicity are reviewed. The importance of the Ames test and biologically directed chemical analysis for identification of these mutagenic compounds is emphasized. Possible chemical reactions acting as sources of mutagenic PAH derivatives in the atmosphere are given.

Airborne polycyclic aromatic hydrocarbons in the city of Zagreb, Yugoslavia.

The concentrations of six PAHs (benzo[a]pyrene, benzo[b]fluoranthene, ideno[1,2,3-c,d]-pyrene, benzo[a]anthracene, benzo[k]fluoranthene and fluoranthene), and lead have been measured systematically for six winter periods from 1977/78 to 1982/83 in the urban air of the city of Zagreb. The average mass concentrations of PAHs were approximately 10 ng m-3. The distribution of PAHs in urban air is discussed. The analytical method for PAH determination is based on filter extraction, two-dimensional thin-layer chromatography and fluorescence spectrometry; lead is measured by atomic absorption.