The chemical composition of the troposphere is determined by the sources and sinks of biogenic and anthropogenic trace gases and the intervening photochemical transformations and mass transport processes linking them. The recent recognition that a thorough understanding of these processes in the natural atmosphere is necessary before the effects of man-made perturbations may be assessed has prompted a concerted effort to study the natural troposphere. The insight gained from this research will allow more accurate predictions of the impact of man's activities on the environment. The objective of this Phase II SBIR research project is the development of instrumentation to measure fluxes of atmospheric trace gases to or from the earth's surface. The method to be investigated is based on the well established eddy correlation technique and would use a tunable diode laser light source combined with a multiple pass absorption cell to detect trace species at sub-part-per-billion levels. The instrument would be designed specifically to be interfaced with a sonic anemometer to provide fast time response and minimal flowfield interference as required for the eddy correlation method. In the Phase II study, final design, development, testing, and field demonstration of the instrument will be conducted. The final instrument will be applicable to flux measurements of trace gases including sulfur dioxide, nitric oxide, nitrogen dioxide, nitric acid, ozone, and hydrogen peroxide.
