Dr. William Smethie Jr.
Earth Institute Contact: Dr. William Smethie Jr.
SF5CF3 is an anthropogenic gas that has an atmospheric concentration of about 0.2 ppt. It has been increasing in the atmosphere for the past 3 decades parallel to the increase of SF6, which has a 30 times greater concentration in the atmosphere. The origin of SF5CF3 is not known, but it is beginning to be used in tracer release experiments in the ocean and groundwater systems to study mixing and transport. Hence there is an interest in determining is origin. Its parallel behavior to SF6 in the atmosphere suggests that it is related to either the manufacture or use of SF6. SF6 is used as an insulator in high voltage equipment such as transformers. One possible source of SF5CF3 is production from SF6 in high voltage equipment. It should be possible to distinguish between a source from the manufacturing process or a source from production in high voltage equipment by measuring the variability of the SF6 and SF5CF3 in the atmosphere. Manufacture of SF6 occurs at a very few locations in the world, but use in electrical equipment is very widespread and extensive in highly populated areas such as the New York metropolitan region. The temporal variability of SF6 has been measured in the atmosphere at Lamont and there are sharp spikes in the concentration that correlate with different wind patterns that sometimes bring air from the heavily populated region to the south and other times air from the ocean. If SF5CF3 is produced in high voltage electrical equipment, which is the main source of SF6 for the atmosphere, SF5CF3 and SF6 should co-vary. If SF5CF3 is produced only in the manufacture of SF6, then the variability of SF6 should be independent of the variability of SF5CF3.