Use of Tracers for the Study of Atmospheric Chemical and Physical Transformation Processes

摘要

Despite insights afforded by laboratory studies into chemical and physical transformation processes in the atmosphere, it remains nonetheless desirable to observe the actual occurrence of such transformations in the ambient atmosphere and/or to measure the rates of these processes. The basis of such studies is observation of changes in concentrations of species of interest as a function of time, but in essentially all cases this translates into a need to observe concentrations as a function of position, the conversion between these two variables being the transport wind velocity. However, concentration changes resulting from processes other than chemical or physical transformation can interfere with the interpretation of transformation processes that is the objective of the study. Potential sources of error include inaccuracy in following an air parcel (especially in the presence of a concentration gradient), concentration changes resulting from dilution, and/or failure of an underlying steady-state assumption. This paper examines the use of tracer compounds as a means of avoiding such errors. Applications of conservative tracers include use as a Lagrangian marker and/or as a concentration standard. Also considered are applications of reactive tracer compounds to the study of atmospheric transformations. Examples of these several types of application are presented. (ERA citation 09:044471)