dear Evelyn
you will find most of the formula used in the 14C field in:
"Mook and van der Plicht (1999) Radiocarbon, 41(3), 227-239"
but before using one formula to estimate 14C turnover you have to
know which end-members you will use. You say you have a mixture
including bomb 14C, but which level?, when did your "bomb carbon
die"? atmospheric CO2 14C was the highest around 1962 (around 200pM)
and since the 14C level in atmosphere decreases (today around 112pM).
Be careful!

good luck and best wishes

christine

PS: through Radiocarbon journal web site, you can find an access to a
radiocarbon list "Radiocarbon Mailing List
<[log in to unmask]>" like this one for stable isotopes



>Hello Listmember,
>I am relatively new to the radiogenic part of carbon isotopes and am
>a bit puzzled on how to estimate MRT of carbon that includes much
>modern (bomb) carbon (i.e. has negative DEL 14C values). My data
>range from 111.7% modern to 99.62% modern.
>
>Somehow, I have difficulty finding the formula in the literature,
>whenever such calculations are published that include the decay of
>bomb carbon in estimation of MRT.
>
>much thanks for any replies.
>
>Evelyn
>
>Dr. Evelyn S. Krull
>CSIRO Land and Water
>Adelaide Laboratories
>PMB 2
>Glen Osmond SA 5064
>Australia
>
>phone: 61-8-8303-8516
>fax: 61-8-8303-8550
>e-mail: [log in to unmask]
>www.clw.csiro.au/staff/EKrull/



****************************************************************
Christine Hatté
Laboratoire des Sciences du Climat et de l'Environnement
UMR 1572 CEA/CNRS
Bât 12, Domaine du CNRS, Avenue de la Terrasse
F-91198 Gif sur Yvette Cedex,  FRANCE
Tel.: (33) (0)1 69 82 35 22 / 35 31      Fax.: (33) (0)1 69 82 35 68
e-mail: [log in to unmask]