• RESEARCHERS from:
• RENSSELAR POLYTECHNIC INSTITUTE
• and ASRC-SUNYA

INTRODUCTION

A cooperative effort between research groups at the Atmospheric Sciences Research Center of the State University of New York and the Surface Studies Laboratory at Rensselaer Polytechnic Institute is currently under way. The ultimate aim of this effort is to assess the role that heterogeneous catalysis of atmospheric chemical reactions at the surface of airborne particulate material plays in the overall turnover rate of pollutant gases in the atmosphere. The approach to the problem is twofold. On the one hand, atmospheric sampling techniques are being used to collect airborne particulate materials, such as those found in fossil fuel fired power plant boilers. These particles are characterized in terms of morphology, size distribution and chemical composition both bulk and surface. Samples of these particles are then prepared for chemical kinetic studies in the molecular beam surface research system, to be described below. In a concurrent study, samples are being prepared to simulate those aspects of the surface composition of the airborne particulates that are felt to be of possible significance catalytically. These samples, after characterization, are being exposed to reactant gas mixtures in the molecular beam system. A combination of mass spectrometric detection of desorbed product fluxes and Auger electron spectrometric detection of non-volatile surface products is being used to characterize the rate and extent of the surface reaction. It is hoped that this combination of techniques will lead to unequivocal conclusions as to the rate-limiting steps in the chemical reactions studied. In the work to date, we have been investigating the overall reaction SO/2 + O/2 +SO/3 + Sulfates at the surfaces of both real stack particulate samples and laboratory- prepared samples, prepared so as to simulate the surface composition of the real particulates. The aim of the work is to assess the role that catalytic reaction on particulate surfaces plays in the turnover of SO/2 in power plant plumes. The techniques used are applicable to a wide range of reactions on a wide range of surfaces. The aim of the present paper is as much to explain the potentialities and limitations of the techniques employed as to report results on the specific system studied to date.