Environmental Engineering Reference
In-Depth Information
(
)
18
2
Tehran D
:
δ
=
6 483
.
δ
O
+
306
.
R
=
0 95
.
(2)
(
)
18
2
NewDelhi
:
δ
D
=
702
.
δ
O
+
3 06
.
R
=
095
.
(3)
By comparing the obtained LMWL equations with GMWL, it is observed that
the slopes and intercepts of the LMWLs are less than the GMWL. Furthermore,
Fig.
1
shows that most of the observed isotope values are below the GMWL. This
phenomenon may be principally assigned to the effect of secondary evaporation
during rainfall (Vodila 2011). Source of the moisture in the cities of Tehran and New
Delhi are different, while the humidity is the same for both cities. Therefore, the
intercepts of the fitted LMWL are the same. In addition, the obtained LMWL for
New Delhi station in this study is nearly the same as the LMWL reported by Kumar
B. et al. (
2010a
). They developed the LMWL for New Delhi station based on all
seasons and monsoon data, respectively as
(
)
(
)
(
)
18
2
δ
D
=
720010
.
±
.
δ
O
+
460050
.
±
.
R
=
095
.
(4)
(
)
(
)
(
)
18
2
δ
D
=
720010
.
±
.
δ
O
+
270080
.
±
.
R
=
097
.
(5)
Effects of Temperature
As already discussed, the concentration of water's heavy stable isotopic compo-
nents may change due to fraction process (Leibundgut et al.
2009
). The variation in
ʴ
18
O corresponding to precipitation with temperature in the stations of Tehran and
New Delhi are shown in Fig.
2
. By investigation of data recorded in both stations
(see Table
1
), more negative values are generally occurred during the winter. As a
a
b
-5
-6
-7
-8
-9
-10
-11
15
10
5
0
-5
-10
-15
δ
18
O=0.33T - 8.691
δ
18
O=0.083T - 10.06
R
2
= 0.331
R
2
= 0.987
-20
-12
-10
0
10
Temperature(C)
20
30
40
-10
0
10
20
30
40
Temperature(C)
Fig. 2
Correlation between isotope values oxygen-18 and air temperature (T) at (
a
) New Delhi
and (
b
) Tehran stations
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