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9844 
Journal Article 
Atmospheric chloroform (CHCl3): ocean-air exchange and global mass balance 
Khalil, MAK; Rasmussen, RA; Hoyt, SD 
1983 
1 
Tellus. Series B, Chemical and Physical Meteorology
ISSN: 0280-6509
EISSN: 1600-0889 
35B 
4 
266-274 
WOS:A1983RF12100003 
Based on the observed global concentrations of chloroform (CHCl3) in the air and seawater, it is demonstrated that the tropical oceans are a source of chloroform to the atmosphere. Even though the total yearly emissions of CHCl3 from the oceans are still uncertain, the flux is estimated to be 0.35 Tg/yr. Anthropogenic sources estimate to be 0.25 Tg/yr. This result suggests that atmospheric CHCl3 may be mostly natural in origin and not entirely man-made as previously thought. The global burden of CHCl3 in the atmosphere is estimated to be about 0.33 Tg and its lifetime is about 6 months. Reaction with tropospheric OH radicals may explain most of the removal of CHCl3 from the atmosphere, but the likelihood of other removal mechanisms is suggested. An average concentration of about 25 ppt was observed at ground level, declining at about 7 percent/km with height. The ratio of Northern Hemisphere to Southern Hemisphere burden of CHCl3 is found to be about 1.6. A global mass balance model is used to show that these findings are mutually consistent. 28 references.