Mihalis Lazaridis

Binary heterogeneous nucleation of a water-sulphuric acid system: The effect of hydrate interaction

Abstract Binary heterogeneous nucleation of water and sulphuric acid vapours has been investigated using the hydrates interaction model in atmospheric conditions. The effect of the contact angle as well as the effect of the size of the condensation nucleus are studied. The number of adsorbed molecules on the condensation nucleus is considered. Hydration is found to decrease the nucleation rate by several orders of magnitude depending on contact angle, temperature, water and acid activity.

Extended hydrates interaction model: Hydrate formation and the energetics of binary homogeneous nucleation

The classical hydrates interaction model presented by Jaecker‐Voirol e t a l. is extended into systems where the gas‐phase number concentrations of acid and water molecules are of the same order of magnitude. Besides the sulfuric acid–water system, the hydrogen iodide–water and the nitric acid–water systems are considered. The distribution N h,k of hydrates containing hwater and kacid molecules has been calculated as a function of relative humidity and relative acidity. An extended formula for the Gibbs free energy of dropletformation is derived. The fraction of free molecules to the total number of molecules (free molecules+hydrates) is solved numerically and therefore the equilibrium constants of hydrate formation are not needed. Hydrate formation often has a significant effect on energetics of nucleation in the acid–water systems and the extended hydrates interaction model represents a definite improvement over the older hydrates interaction model.

Aerosols and environmental pollution.

The number of publications on atmospheric aerosols has dramatically increased in recent years. This review, predominantly from a European perspective, summarizes the current state of knowledge of the role played by aerosols in environmental pollution and, in addition, highlights gaps in our current knowledge. Aerosol particles are ubiquitous in the Earth’s atmosphere and are central to many environmental issues; ranging from the Earth’s radiative budget to human health. Aerosol size distribution and chemical composition are crucial parameters that determine their dynamics in the atmosphere. Sources of aerosols are both anthropogenic and natural ranging from vehicular emissions to dust resuspension. Ambient concentrations of aerosols are elevated in urban areas with lower values at rural sites. A comprehensive understanding of aerosol ambient characteristics requires a combination of measurements and modeling tools. Legislation for ambient aerosols has been introduced at national and international levels aiming to protect human health and the environment.

Measurements of particulate matter within the framework of the European Monitoring and Evaluation Programme (EMEP): I. First results

Particulate matter (PM) monitoring presents a new challenge to the transboundary air pollution strategies in Europe. Evidence for the role of long-range transport of particulate matter and its significant association with a wide range of adverse health effects has urged for the inclusion of particulate matter within the European Monitoring and Evaluation Programme (EMEP) framework. Here we review available data on PM physico-chemical characteristics within the EMEP framework. In addition we identify future research needs for the characterisation of the background PM in Europe that include detailed harmonised measurements of mass, size and chemical composition (mass closure) of the ambient aerosol.

Binary heterogeneous nucleation at a non-uniform surface

Abstract The model for the heterogeneous nucleation on aerosol particles with a non-uniform surface introduced by Gorbunov and Kakutkina has been extended to binary systems, and the results of this model have been compared with the results of the uniform surface model. Binary heterogeneous nucleation of water-sulphuric acid and water-nitric acid vapours have been investigated. The uniform surface model is found to underestimate the nucleation rate with a few orders of magnitude compared to the model for non-uniform surfaces.

Human Exposure to Pollutants via Dermal Absorption and Inhalation

The human body is exposed to pollution on a daily basis via dermal exposure and inhalation. This book reviews the information necessary to address the steps in exposure assessment relevant to air pollution. The aim is to identify available information including data sources and models, and show that an integrated multi-route exposure model can be built, validated and used as part of an air quality management process. n nMany epidemiological studies have focused on inhalation exposure. Whilst this is appropriate for many substances, failure to consider the importance of exposure and uptake of material deposited on the skin may lead to an over/underestimation of the risk. Hence dermal exposure is also considered. Drinking water contamination by disinfection by-products is also discussed.

Measurements of particulate matter concentrations at a landfill site (Crete, Greece).

Large amounts of solid waste are disposed in landfills and the potential of particulate matter (PM) emissions into the atmosphere is significant. Particulate matter emissions in landfills are the result of resuspension from the disposed waste and other activities such as mechanical recycling and composting, waste unloading and sorting, the process of coating residues and waste transport by trucks. Measurements of ambient levels of inhalable particulate matter (PM(10)) were performed in a landfill site located at Chania (Crete, Greece). Elevated PM(10) concentrations were measured in the landfill site during several landfill operations. It was observed that the meteorological conditions (mainly wind velocity and temperature) influence considerably the PM(10) concentrations. Comparison between the PM(10) concentrations at the landfill and at a PM(10) background site indicates the influence of the landfill activities on local concentrations at the landfill. No correlation was observed between the measurements at the landfill and the background sites. Finally, specific preventing measures are proposed to control the PM concentrations in landfills.

Heterogeneous nucleation on rough surfaces: implications to atmospheric aerosols

Abstract The effect of the surface roughness of solid atmospheric aerosol particles on their heterogeneous nucleation capability has been examined using the concept of “self-affine” rough surfaces. The surface roughness has a great influence on the contact angle between the particle surface and the nucleating liquid droplets. Roughness enhances wetting and the rate of heterogeneous nucleation from the vapor to the liquid phase. The paper furthermore discusses the considerable influence of the surface roughness on the physico-chemical characteristics of atmospheric insoluble aerosol particles.

Variability of ozone in the Eastern Mediterranean during a 7-year study

Ozone measurements have been performed in the period 2003–2009 at Akrotiri (suburban) and Finokalia (coastal) monitoring stations on the island of Crete, Greece. The main objectives were to investigate the concentration levels of ozone in the region of Crete, its spatial and temporal variability, the effect of air mass origin and local sources on ozone levels, and the frequency of exceedances of the EU limits for ozone concentrations in the area. The observed mean values for Akrotiri and Finokalia stations were 44.5u2009±u20098.5 and 49.1u2009±u200910.6xa0ppbv, respectively. Ozone concentrations were higher during the 8-month period between March and October (52.3u2009±u20096.8 and 53.0u2009±u20097.4xa0ppbv for Akrotiri and Finokalia station, respectively) whereas, in the period November–February, the concentrations were lower (37.7u2009±u20094.7 and 39.1u2009±u20096.9xa0ppbv, respectively). The above values indicate that there is not a west-east gradient of ozone concentration in the studied area. At both stations, AOT40 limit values were higher than the limit set by the European Union (Directive 2008/50/EC). Exceedances of the EU target value were encountered during 88 and 67xa0% of the time in Akrotiri and Finokalia stations, respectively. Differences on the diurnal patterns and daily ozone maxima between the two stations were attributed to the different characteristics of the two stations and to the effect of local pollution sources to Akrotiri station. The average value of the amplitude of the daily cycle (calculated as the difference between maximum and minimum values) in the case of Akrotiri was 8.3xa0ppbv, and it was about two times the corresponding value in Finokalia (4.7xa0ppbv), which is an indication of the effect of the anthropogenic emission produced in the city of Chania to the Aktotiri station environment. At Finokalia, the maximum values were observed 2–4xa0h later than those at Akrotiri. During springtime, the difference in the maximum values appearance was close to 4xa0h, with the maximum at Akrotiri at 16:00 (LT) and at Finokalia at about 20:00 (LT). This time difference supports the transfer of gaseous precursors and already formed ozone molecules toward Finokalia.

Gas–particle partitioning of organic compounds in the atmosphere

Abstract Gas–particle partitioning of condensable organic compounds in the atmosphere is described using two methods. The first method is based on the use of a comprehensive mechanistic model of adsorption/absorption processes. The second method is based on aerosol yields estimates. The model parameters in the adsorption/absorption model are evaluated from experimental data. The concepts of concentration of adsorbed molecules on the surface of aerosol particles and diffusion of adsorbed molecules in the liquid phase are used for determining the importance of the adsorption/absorption mechanisms. The model calculations showed a qualitative agreement with available experimental data for alkanes. Furthermore, a modified version of the Carbon Bond IV chemical mechanism including an aerosol yields method to model the formation of organic aerosols in reactive plumes is used in combination with a plume dispersion model. The formation of secondary organic matter in plumes contributes significantly to the total secondary aerosol mass produced.