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Session 3151

A TRACER LABORATORY FOR UNDERGRADUATE ENVIRONMENTAL ENGINEERING PROGRAMS

HOLLY G. PETERSON MONTANA TECH OF THE UNIVERSITY OF MONTANA

I. INTRODUCTION Environmental engineers are often involved in field work to assess the impacts of environmental problems. While traditional lectures and problem-solving exercises serve as the basis of most college-level courses in environmental engineering, “hands-on” projects are necessary to provide students with additional skills to succeed as professionals after graduation. The purpose of this paper is to describe a novel application of atmospheric tracer technologies to enhance laboratory facilities in environmental engineering. With a minimal amount of inexpensive, specialized equipment, tracer experiments can be conducted throughout the curriculum to complement traditional lectures and problem-solving exercises for fundamental topics such as mass balance, unit conversions, dispersion of pollutants, risk analysis, indoor air quality, and ventilation. Section II contains background on tracer technologies while Section III specifies equipment and layout for a field experiment. Example applications are described in Sections IV, and conclusions follow in Section V.

II. BACKGROUND For a typical tracer study in the field, experiments are conducted in which air parcels are tagged with a tracer gas. The air parcels are tracked while measuring concentrations downwind of the source, and by investigating how the tracer behaves, we learn how pollutants are advected and diluted by the atmosphere.

As reported by Gifford, substances used as tracers by early researchers include Kleenex lint, dandelion seeds, balloons, smoke puffs, and soap bubbles.1 Shortcomings associated with these tracers are non-negligible mass constraints in addition to detection and measurement limitations. During the past decade, however, significant developments have been made in gaseous tracer technologies. Compared to particles or balloons, non-reactive gases are more likely to truly follow the airflow, and tracer gas detection systems have been designed to measure concentrations as small as a few parts-per-trillion-by-volume (pptv) and to measure concentrations in real time. Sulfur hexafluoride (SF6) is one of the preferred tracers because it is chemically inert, nonflammable, non-radioactive, odorless, insoluble in water, and easily measured using electron capture detection.2 In addition, SF6 is man-made with no natural sources in the environment. With a low background concentration in the atmosphere, approximately 3 pptv3, sulfur hexafluoride is a minor contributor to predicted global warming.

To date, tracer technologies have been used primarily by researchers to obtain data for developing and testing relationships that predict transport and diffusion of air pollutants. The following sections, however, describe equipment and applications of a tracer laboratory for educating undergraduate environmental engineering students.

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Peterson, H. G. (1997, June), A Tracer Laboratory For Undergraduate Environmental Engineering Programs Paper presented at 1997 Annual Conference, Milwaukee, Wisconsin. 10.18260/1-2--6841