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Direct measurement of the production rate of 14 C near Earth's surface
Author(s) -
Mak J. E.,
Brenninkmeijer C. A. M.,
Southon J. R.
Publication year - 1999
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1999gl010791
Subject(s) - atmosphere (unit) , flux (metallurgy) , production rate , earth (classical element) , environmental science , atmospheric sciences , carbon fibers , production (economics) , geology , meteorology , chemistry , materials science , physics , industrial engineering , organic chemistry , composite material , composite number , engineering , economics , mathematical physics , macroeconomics
Environmental 14 C is well known for its application in carbon dating organic material, as well as its use as a geochemical tracer in the oceans and atmosphere. More recently, 14 C in the form of atmospheric 14 CO has been used to estimate the concentration of hydroxyl radical, which is the primary oxidant of the atmosphere. This latter application is dependent upon accurate knowledge of the cosmogenic production rate, which has been calculated, but not directly measured. We have measured the atmospheric production rate of 14 C near the earth's surface on a 300‐meter research tower in Colorado, at the South Pole, at Scott Base, Antarctica, and near Mount Cook, New Zealand. The observed production rate near the surface was 50% of the production rate calculated by an earlier study. We also find that the ‘ground effect’, which causes an increase in the thermal neutron flux resulting in an enhancement of the production rate of 14 C, is significantly smaller than calculated in earlier studies.