> I would be very grateful if anyone could provide me information (value and
> sources of references) on del C-13 of methane in atmosphere.
In addition to the references already mentioned, you can also check out:
"Carbon isotopic composition of atmospheric methane: fossil and biomass
burning source strengths" -- Quay et al, Global Biogeochemical Cycles,
Vol 5, No 1, pp 25-47, March 1991.
"Determination of the isotopic composition of atmospheric methane and its
application in the antarctic" -- Lowe et al, JGR, Vol 96, No D8, pp
"Atmospheric Methane and its carbon isotopes in the southern hemisphere:
their time series and an instructive model" -- Lassey et al, Chemosphere,
Vol 26, Nos 1-4, pp 143-160, 1993.