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Elemental composition study of aerosols collected in a speleotherapeutic cave situated below Budapest

Zs. Kertész, I. Borbély-Kiss and I. Hunyadi

The Szemlohegy-cave is one of the well-known hydrothermal caves of the densely poppulated Rózsadomb area of Budapest, which have been used for speleotherapy of respiratory diseases for years. It is known from the periodically changing airborne radon activity concentration data, that airflow of seasonally reversed direction are formed along the cave passages and fissures due to the temperature difference between the surface and cave air. This means that an intensive interaction takes place between the cave and its environment. The pollution of nearby waters and the urban atmospheric air represents a real danger for these caves below Buda, which are candidates for the UNESCO World Heritage. The study of cave aerosols should be very important from the point of view of either the control possibilities of environmental protection or speleotherapy, and probably helps in getting acquainted with the cave-forming processes. We applied our standard aerosol sampling method to the high-humidity environment of the caves, and we studied the elemental composition, size fractionation as well as the spatial distribution and the seasonal variation of cave aerosols.

Aerosol sampling was performed in October 1995, when the summer air circulation was dominant, and in January 1996 and in March 1998, when the winter air circulation took place in the cave. Six portable membrane pumps with 2-stage Nuclepore filter holders were placed along the cave fissures to obtain aerosol spatial distribution. In March 1998 a 7-stage cascade impactor was also deployed in the speleotherapeutic sites, with the help of which we sudied the size fractionation. Temperature and relative humidity were also measured during the sampling.

Concentrations of the following elements were determined by PIXE: Al, Si, P, S, Cl, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Ba, and Pb.

We pointed out that the external polluted air penetrate into the cave, down to its bottom due to cave air motions. However aerosol concentration diminish with increasing distance from the entrance, and are minimal in the site of the therapy. Statement could be made also for the most probable air passages. With the help of the cascade impactor the cleaning effect of the cave was also showed.

Though traces of the anthropogenic pollution of the Budapest air is shown in the Szemlohegy-cave, every case the measured elemental concentrations remained less than one-tenth the air quality standards valid for the increasingly protected areas. The elements S, Cl, Zn, Br or Pb as tracers indicate the interaction between the cave air and the urban atmosphere, and also the direction and the strength of air movements in the cave.

This work was supported by the National Scientific Research Found, Budapest (Contract No. OTKA-T017040 and T016558), and the results are accepted for publication in NIMB (Ref. No. 2101): Zs. Kertész, I. Borbély-Kiss and I. Hunyadi: Study of Aerosols Collected in a Speleotherapeutic Cave Situated below Budapest, Hungary.

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EP Systema, Debrecen, Hungary