Sampling site characterization program

Before a source analysis program is undertaken, it is important to decide which information is really required. Sampling sites must be selected with care. Choice of the site can significantly affect accuracy and cost. Care must also be taken in the selection of sampling points at the site. Measurement usually involves the deterrnination of temperature, concentration, and characterization of the gas contaminants. It also requires the mass rates of emission of each contaminant, therefore concentration and volumetric flow data are required. 

The elemental analysis of oil sand bitumen (extra heavy oil) has also been widely reported (Speight, 1990), but the data suffer from the disadvantage that identification of the source is too general (i.e., Athabasca bitumen which covers several deposits) and is often not site specific. In addition, the analysis is quoted for separated bitumen, which may have been obtained by any one of several procedures and may therefore not be representative of the total bitumen on the sand. However, recent efforts have focused on a program to produce sound, reproducible data from samples for which the origin is carefully identified (Wallace et al., 1988). It is to be hoped that this program continues as it will provide a valuable database for tar sand and bitumen characterization. 

The field program of the Materials Effects Group currently exposes well-characterized specimens of marble and limestone, as well as metals and other materials, to outdoor conditions at sites that are instrumented to monitor meteorological variables, rain chemistry, and air quality factors. Further descriptions of the environmental conditions at the sites are given by Flinn and by Reddy et al. in this volume. Stone samples have been installed at sites near Raleigh, NC Chester, NJ Newcomb, NY and in Washington, DC, and have been monitored for one year. 

One typical TPD experiment is designed in a way to enable the pre-treatment of the sample, in situ the admission of specific adsorbate (probe) up to some specific surface coverage or up to the saturation and subsequently, desorption which is performed in a temperature-controlled regime. Many different chemical species can be used as probes if a chosen probe can titrate acid or basic sites at the surface, TPD can be used for the characterization of acidity/basicity of some adsorbent. In fact, temperature-programmed desorption and adsorption calorimetry are most commonly used for the study of acid/base properties of solid materials [20, 35, 36]. The same probe molecules that are used for adsorption calorimetry experiments are applicable in the case of TPD while the investigation of acidic/basic character of solids is perhaps... 

---