Airborne in-situ measurement of particulate sulfur and sulfuric acid with flame photometry and thermal analysis

An airborne in-situ particulate sulfur monitor based on the FPD principle has been developed and tested. The lower detection limit for particulate sulfur is about 1 ppb(4 μg SO 4 m −3). Time response to 90% of signal is about 5 s. The characteristic FPD zero drift caused by changes in pressure, humidity and other environmental factors has been compensated for by including an automatic zeroing cycle so that the zero signal can be monitored along with the sulfur signal. Preliminary results indicate that data collected during altitude descents or ascents is of good quality. With the addition of a preheater system, simultaneous measurement of sulfuric acid and total particulate sulfur profiles in plumes and haze palls is possible with a single monitor.