Comparison of Relationship Between the Concentrations of Water Isotopes in Precipitation in the Cities of Tehran (Iran) and New Delhi (India) - Management of Natural Resources in a Changing Environment - page 28

measured by mass spectrometry. In general, the isotopic abundance ratios are
expressed as parts per mil of their deviations as given by (Vienna Standard Mean
Ocean Water, VSMOW)

R − R

sample SMOW

δ= × 100‰ (1)

R

SMOW

where R refers to the isotopic ratio (D/H) or ( 18 O/ 16 O) (Machavaram and
Krishnamurthy 1995 ). In 1954, the International Atomic Energy Agency (IAEA), in
co-operation with the World Meteorological Organization (WMO), conducted a
worldwide survey of oxygen and hydrogen isotope content in precipitation. Since
1961, more than 780 meteorological stations in 101 countries have been monthly
collecting precipitation samples. These samples are analyzed at the isotope hydrol-
ogy laboratory (IAEA 2006 ).
Monitoring the variation of isotopic composition of precipitation requires to
investigate ʴ 18 O and ʴD values of precipitation. Many researchers such as Argiriou
and Lykoudis ( 2006 ), Yu et al. ( 2008 ), Takeuchi et al. ( 2009 ), Van der Veer et al.
( 2009 ), Kumar et al. ( 2010a , b ), Warrier and Babu ( 2011 ), and Vodila et al. ( 2011 )
have recently studied the variation of ʴ 18 O and ʴD in precipitation for different parts
of the world.
In this study, the effect of meteorological factors on precipitation isotopic
data have been investigated in two stations of the Atomic Energy Agency,
namely Tehran and New Delhi stations. The precipitation of Tehran is controlled
by the Atlantic and the Eastern Mediterranean moisture sources, while in New
Delhi it is controlled by Southwest monsoon rainfall that comes from the direc-
tion of Arabian Sea. The source of the moisture in the cities of Tehran and
New Delhi are different. The most important aim of this study is to discuss the
effects of these different sources of moisture on water isotopes' concentration in
precipitation.

Materials and Methods

Sampling Stations

In this research, rainfall recorded at two GNIP stations (Tehran-New Delhi) are used
to study the effect of the meteorological factor on the concentration of isotope
composition.
Tehran situated in the north of Iran on the southern slopes of Alborz Mountains
is located between 35°34′ and 35°50′N and 51°20′ and 51°36′E and encompasses an
altitude range between 1,050 and 2,000 m above mean sea level (amsl). Tehran fea-
tures a semi-arid and continental climate which is largely defined by its geographic