First measurements of total chlorine and bromine in the lower stratosphere

A total halogen collection system employing ultra‐pure activated charcoal traps has been developed for use in the stratosphere aboard aircraft and balloon sampling platforms. Neutron activation techniques for low‐level chlorine, bromine, and iodine analysis within the activated charcoal sampling matrix were developed. Initial results from six aircraft flights and one balloon mission in the lower stratosphere are presented for latitudes ranging from 16°N to 67°N. Little variability was observed in twelve total, gaseous and particulate chlorine (Cl tot ) determinations as a function of latitude at 20 km with values ranging between 2.7 ± .9 ppbv and 3.2 ± .7 ppbv. Five total bromine (Br tot ) values showed substantial variability ranging from 7 ± 4 pptv to 40 ± 11 pptv. No iodine was observed in any samples but a calculated I tot upper limit of < 3 pptv was determined.