<
P>&nb
sp;Radi
on
uclide
s are widely
used t
o perf
orm
ge
ochr
on
ol
ogic inve
sti
gati
on
s of the trace
sediment de
positi
on
pr
oce
ss in aq
uatic envir
onment
s on different tem
poral
scale
s. Thi
s st
udy
pre
sent
s the activitie
s of radi
on
uclide
s t
o select a rea
sonable
ge
ochr
on
ol
ogic datin
g meth
od and
st
udy the
sediment de
positi
onal envir
onment in Lake Qin
ghai
on the Qin
ghai-Tibet Platea
u. The ran
ge
of ctivitie
s (Bq.k
g1 )
of 137C
s, 226Ra, 238U, 228Ra, 228Th, and 40K were 2e103, 24e49, 33e156, 20e49, 30e50, and 403e664, re
spectively. The
sedimentati
on flfl
ux wa
s calc
ulated a
s 1.66 106 t
on.a1 ba
sed
on the
summary
sedimentati
on rate in Lake Qin
ghai, and the
sediment c
ontrib
uti
on
s fr
om river
s, a
uthi
genic carb
onate
s, lac
ustrine
or
gani
sm
s, and atm
ospheric de
positi
on were 45.18%, 22.44%, 3.02%, and 29.36%, re
spectively. The decrea
sed 226Ra/238U radi
oactivity rati
os fr
om the catchment t
o the lake centre indicated that the rem
oval
of
urani
um relative t
o it
s da
ughter
pr
od
uct
s occ
ur
s d
urin
g er
osi
on
pr
oce
sse
s. The
positive 228Thex (exce
ss 228Th) val
ue
s in the
upper 1 cm
of the
sediment
sugge
sted that the
sediment in the t
op 1 cm have been re
suspended, mixed and/
or tran
sported. The di
strib
uti
on
of 137C
s in the
sediment
s indicated that the maxim
um activity
of 137C
s in the
sediment
s c
orre
spond
s t
o the 1963
peak in the
gl
obal fall
out fr
om atm
ospheric n
uclear wea
pon
s te
stin
g; m
ore
over, the 1986 Chern
obyl accident
si
gnal wa
s diffific
ult t
o identify. The
use
of 137C
s a
s a chr
on
ol
ogic t
ool m
ust be
perf
ormed caref
ully d
ue t
o it
s mi
grati
on
pr
oce
ss in
sediment
s.
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