Clair Patterson


Clair Cameron Patterson (June 2, 1922 – December 5, 1995) was ageochemist born in Mitchellville, Iowa, United States. He graduated fromGrinnell College in Grinnell, Iowa, received his Ph.D. from the University of Chicago, and spent his entire professional career at the California Institute of Technology.

In collaboration with George Tilton, Patterson developed the uranium-lead dating method into lead-lead dating, and by using lead isotopic data from theCanyon Diablo meteorite, he calculated an age for the Earth of 4.55 billion years; a figure far more accurate than those that existed at the time and one that has remained largely unchanged since 1956.

Patterson had first encountered lead contamination in the late 1940s as a graduate student at the University of Chicago. His work on this led to a total re-evaluation of the growth in lead concentrations in the atmosphere and the human body from industrial causes and his subsequent campaigning was seminal in the banning of lead additives to gasoline and lead solder in food cans.

Clair (Pat) Patterson was born in Mitchellville, Iowa and graduated from Grinnell College in chemistry where he met his wife, Lorna (Laurie) McCleary. They both moved to the University of Iowa for graduate work where he did an M.A. in molecularspectroscopy. Both were then sent to work on the Manhattan Project, first at the University of Chicago and then at Oak Ridge, Tennessee where he encountered mass spectrometry.

After the war they returned to Chicago where Laurie took a research job as an infrared spectroscopist to support Pat whilst he did a Ph.D. at the University of Chicago under Harrison Brown. After a postdoctoral year at Chicago, Patterson moved with Brown to the Division of Geology (later the Division of Geological and Planetary Sciences) at the California Institute of Technology (Caltech) in 1952 as founding members of its geochemistry program. Pat remained at Caltech for the rest of his life. He and Laurie had four children.

Harrison Brown of the University of Chicago developed a new method for counting lead isotopes in igneous rocks, and assigned it to Clair Cameron Patterson as a dissertation project in 1948. During this period he operated under the assumption that meteorites are left-over materials from the creation of the Solar System, and thus by measuring the age of one of these rocks the age of the Earth would be revealed. Gathering the materials required time, and in 1953, Clair Cameron Patterson had his final specimens from the Canyon Diablo meteorite. He took them to the Argonne National Laboratory, where he was granted time on a late model mass spectrometer.

In a meeting in Wisconsin soon afterward, Patterson revealed the results of his study. The definitive age of the Earth is 4.550 billion years (give or take 70 million years). This number still stands although the margin of error is now down to about 20 million years.

His ability to isolate microgram quantities of lead from ordinary rocks and determine their isotope composition led him to examining the lead in ocean sediment samples from the Atlantic and Pacific. Deriving from the different ages at which the landmasses had drained into the ocean, he was able to show that the amount of anthropogenic lead presently dispersed into the environment was about eighty times the amount being deposited in the ocean sediments: the geochemical cycle for lead appeared to be badly out of balance.

The limitations of the analytic procedures led to him using other approaches. He found that deep ocean water contained 3-10 times less lead than surface water, in contrast to similar metals such as barium. This led him to doubt the commonly held view that lead concentrations had only grown by a factor of two over naturally occurring levels.

Patterson returned to the problem of his initial experiment and the contamination he had found in the blanks used for sampling. He determined through ice-core samples from Greenland that atmospheric lead levels had begun to increase steadily and dangerously soon after tetraethyllead began to see widespread use in fuel, when it was discovered to reduceengine knock in internal combustion engines. Patterson subsequently identified this, along with the various other uses of lead in manufacturing, as the cause of the contamination of his samples, and because of the significant public-health implications of his findings, he devoted the rest of his life to removing as much introduced lead from the environment as possible.

Patterson died in his home in Sea Ranch, California at the age of 73 on December 5, 1995. The reported cause of his death was a severe asthma attack.

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