Maria Kolarova

Variation of short-lived beta radionuclide (radon progeny) concentrations and the mixing processes in the atmospheric boundary layer.

Radon is emitted to the atmosphere with quasi constant emission rates depending on the radium concentration in the earths crust and soil physical properties. In this way, the 222Rn and 220Rn concentration in air reflects significantly the thickness of the atmospheric boundary layer (ABL). The aerosol-associated, beta-emitting progeny nuclides of 222Rn were measured daily in the framework of the atmospheric radioactivity monitoring program of NIMH at Sofia. The 214Pb concentration was estimated from the measured short-lived beta activity of 24-h filter samples, changed daily at 6:00 GMT. The impact of some meteorological factors such as wind direction, wind velocity, humidity, and temperature on short-lived beta radionuclides is estimated, and the results show no simple statistical relationship. A seasonal pattern was observed with winter minima and late summer-early autumn maxima. High variability in daily morning concentrations and mean monthly values was observed. There were well pronounced differences between years. The height of the convective ABL was estimated from daily radio-soundings at 12:00 GMT for the period 2001-2006 and from seven soundings per day during the experimental campaign in Sofia in October 2003. In general, concentrations of short-lived 222Rn progeny nuclides decreased with increased convective ABL height.

Assessing the Impact of Port Bourgas on Air Quality During Different Seasons

Bulk cargo handling operations is one of the major factors that may cause undesirable effect to the air quality of urban and port areas in Bourgas. The air quality monitoring of the port of Bourgas is needed to deliver reliable data for air pollution assessment in the area of the port, as well as for better insight of the impact of the port activities on the air quality of the city. Unfortunately, there is no information for the bulk cargo or open source events. There is no record on what type and amount of material, what size of the pile and duration of exposure to wind existed. Therefore, in this dispersion study of the particulate matter with diameter size smaller than 10 micrometers (PM10), we use as source a pile of arbitrary size and emission rate that give concentrations close to those observed in the centre of the city by the air quality authorities at wind speed of 5 ms–1. The United States Environmental Protection Agency (US EPA) AERMOD (Air DispERsion MODel) system is used here to illustrate the dispersion pattern and to show applicability for future use by the port authorities. The results showed that the central part of Bourgas might be polluted by port activities at southern winds, but those have low frequency. The easterly and southeasterly winds, which appear more often, bring the eventual pollutants from the port towards the lake “Bourgasko ezero” and the district “Pobeda.” Comparing monitoring data from the port and from different parts of the city, we revealed no difference in winter months, but higher concentrations at the port in the transition months April and September.

The ABL Models Yordan and Yorcon — Top-Down and Bottom-Up Approaches for Air Pollution Applications

Two atmospheric boundary layer (ABL) models developed in agreement with the similarity theory are applied: YORDAN - for stable and neutral conditions and YORCON - for convective cases. Both models consist of a surface layer and an overlying Ekman layer. The vertical profiles of the temperature, wind velocity and the turbulent exchange coefficient in the ABL can be obtained applying the models. A proper parameterization is developed in both cases applying the resistance laws for stable, neutral and convective conditions. The relation between the external and internal to ABL parameters are given by the resistance laws numerically solved in both models. The input parameters for the models are obtained from the experimental data applying two approaches: the first one (called “top-down” approach) uses data for the geostrophic wind and the potential temperature. The second one (called “bottom-up” approach) uses data from the surface meteorological observations.

Parameterization of PBL from the Surface Wind and Stability Classes Data

The aim of the present work is to determine the vertical profiles of wind velocity and turbulent exchange coefficient in the Planetary Boundary Layer (PBL). Here a simple but very effective PBL model is presented based on the similarity theory. As input to this model the internal to PBL parameters are needed. There are two ways to obtain these parameters from experimental data and they are called here “down-up” and “updown” approaches. The full description of the “up-down” approach is given in a number of papers by the same authors. It will be also presented here briefly. The main stress will be on the “down-up” approach allowing to obtain the wind and turbulence profiles using the data collected from automatic weather stations. Recently, such stations are introduced in the observational network of NIMH providing hourly measurements of the wind velocity at 10-m height as well as atmospheric stability classes (based on measurements of the horizontal wind pulsation). The proposed approach uses these data for determining the internal and external PBL parameters on the basis of the Similarity theory.

On the Relationship Between Synoptic Scale Parameters and Pasquill Stability Classes for the Purposes of Air Pollution Modeling

Quite often, for the tasks connected with environmental impact assessment it is necessary to estimate pollutant concentrations on the basis of standard meteorological data such as sunshine, cloud amount, and wind velocity using the Pasquill stability classes. They are usually determined from the atmospheric characteristics estimated near the ground surface using a table classification with 10 m wind velocity and insolation intensity (or cloud cover at night). These meteorological data are not allways available and they are difficult for prognostication. For the purposes of the prognostical estimation of the atmospheric diffusion in case of emergency releases when regulatory type models are used it is useful to find the relation between the synoptic scale parameters obtained from the numerical weather prediction and the Pasquill stability classes.