The chemical composition of the atmosphere is determined by terrestrial sources

for Chemical and Environmental Physics,45 Manning Road, Billerica, MA 01821ABSTRACTBiogenic emissions from and dry deposition to terrestrial surfaces areimportant processes determining the trace gas composition of the atmosphere. Wehave developed an instrument for flux measurements of gases such as CH4, N20, and03 based on the eddy correlation technique which combines trace gas fluctuationmeasurements with simultaneous windfield measurements. The instrument combines atunable diode laser infrared light source with an open-path multipass absorptioncell in order to provide the fast time response ("O.ls) and short basepathlength (0.6m) required for the eddy correlation method. Initial field testsusing the instrument to measure methane emissions from a local wetland demonstratethe capability for high precision eddy correlation flux measurements.