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We pr
o
vide the
re
sults of 24-
hour ob
ser
va
tions m
ade in a
m
eadow s
ite l
o
cate
d in a sm
all r
iver
val
ley
in Cen
tra
l Eu
rope.
Sam
ples of at
m
o
-
spheri
c air
wer
e take
n from
thre
e ho
ri
zons: ne
ar t
he soil
(0.05 m
), i
n the gr
ass (
0.5 m
) and a
bove the m
eadow (
2 m
) at
two-
hour in
ter
vals.
At the
sam
e tim
e, sa
m
ples of soi
l air
wer
e col
lect
ed from
two ho
ri
zons: –0.
1 and –0.5 m
.
We ha
ve found a var
i
a
tion of
d
13
C above t
he
ground from
–6‰ dur
ing the da
y to –20‰
late
at night
ac
com
pa
nied by
vari
a
tions i
n CO
2
con
cen
tra
tion from
270 ppm
dur
ing the da
y,
to
var
i
ous lev
els l
ate a
t night a
t dif
fer
ent hei
ghts above
the gr
ound. The
m
ax
i
m
um
con
cen
tra
tion wa
s 1430 ppm
at the
ground le
vel.
The c
or
-
re la tion
co ef f
i cient
be tween
d
13
C and re
cip
ro
cal of c
on
cen
tra
tion wa
s the hi
gh
est (
R
2
= 0.984)
for the s
am
ples c
ol
lect
ed 2 m
above the
ground, t
he re
gres
sion li
ne cle
arl
y in
di
cat
ing CO
2
m
ix
ing from
the tw
o source
s: at
m
o
spheri
c and bioge
nic r
es
er
voirs.
The i
n
ter
cept of t
he
m
ix
ing line yields
d
13
C = –23.0‰
for the bi
ogenic C
O
2
.
In con
trast, the di
ur
nal vari
a
tions in th
e soil were rel
a
tively sm
all,
d
13
C var
ied
from
–21.6 to –23.
4‰, w
hile C
O
2
con
cen
tra
tion from
4300 to 8200 and from
24 700 to 34 500 ppm
at dept
hs of 0.1 m
and 0.5 m
re
spec
-
tively, which is less than
2-fold
. Sm
all di
ur
nal vari
a
tions are char
ac
ter
is
tic of dry soils, wh
ere
d
13
C is weakly cor
re
lated with CO
2
con cen
-
tra
tion (
in our c
ase
R
2
was 0.
30 and 0.54,
re
spec
tivel
y)
.
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