A16
CONTRIBUTION OF ENVIRONMENTAL ISOTOPE TECHNIQUES
IN STUDYING THE GROUNDWATER RESOURCES AT PEKANNENASI, PAHANG
Kamarudin Samuding, Roslanzairi Mostapa and Mohd Muzamil Mohd Hashim, Jeremy Andy
anak Dominic Daung and Nor Dalila Desa and Kamaruzaman Mohamad
Environmental Tracer Application Group, Malaysian Nuclear Agency,
Bangi, 43000 Kajang, Selangor, MALAYSIA.
Tel: 03-89250510 Fax: 03-89250907
Email:
[email protected]
The contribution of environmental isotope techniques in identifying the groundwater
resources is presented. According to Siddle (1998), environmental isotopes have now
been used to study groundwater systems particularly for determining the groundwater
recharge sources, ages of water bodies, the interaction between surface water and
groundwater. Most frequently used environmental isotopes include the stable isotopes 2H
and 18O whereas tritium (3H) is radioactive isotopes (Kortelainen 2011, Aggarwal et al.
2009). The environmental isotopes particularly stables isotopes (18O and 2H) are
measured using Continuous Flow Isotope Ratio Mass Spectrometer (CF-IRMS). Oxygen
and hydrogen isotope compositions are expressed as units of parts per thousand or delta
per mill (δ ‰) deviation from standard mean ocean water (SMOW). Whilst, the
radioactive environmental isotopes Tritium is measured using tritium enrichment system
and liquid scintillation counter. The precision of the analytical measurement is ±0.05‰
for δ2H and ±1‰ for and δ18O. For the isotope analysis, the samples were measured in
triplicates in each analytical run for better results. The usual way to interpret stable
2
18
O from the precipitation isotopes values. In
hydrological cycle, precipitation is considered as the input for surface water and
groundwater. Hence the importance of establishing Local Meteoric Water Line (LMWL),
thus establishing weighted mean precipitation was adopted as shown in Figure 1.
These techniques have been used to study the groundwater resources at PekanNenasi Pahang. In this study, number of samples has been collected from various sources
such as boreholes (shallow and deep aquifers) and several locations along Sungai Pahang
from Paloh Hinai to the estuary as shown in Figure 2. The results show that most of the
isotopic composition of 2H–H2O and 18O–H2O at the study area is seen narrow isotopic
variation may suggest that all groundwater samples originated from the same area of
recharge predominantly from rainfall and nearby main rivers (Sungai Pahang) as shown
in Figure 3. Besides that, the δ2H and δ18O compositions for the groundwater that is
closed to the coastline is relatively enriched and fall on the mixing line. This indicates
that the sea water intrusion occurred in this area and can be proved by the supporting data
from physical dan chemical parameters. The value of isotope compositions are also seen
enriched at the surface water which are located near to the coastline. Results from the
radioactive environmental isotopes Tritium (3H) show that the shallow groundwater is
consider as a modern water, whereas the deep groundwater might be an old water
especially at the borehole BH-3A and BH-3B (Figure 4). As a summary, environmental
isotope techniques has a capability to confirm the results obtained by conventional
hydrological methods as well as to provide more information to some hydrological
problems.
Keywords: Environmental isotopes, groundwater, surface water, seawater intrusion, recharge
References
North, J. & Frew, R.D. 2007. Isotopic Characterization of leachate from seven New
Zealand Landfill. In: Landfill Research Focus. Nova Science Publisher. pp. 199261.ISBN 1-60021-7753
Hackley, K.C., Liu, C.L., and Coleman, D.D., 1996. Environmental isotope
characteristics of landfill leachates and gases. Ground Water, 34: 827-836
Sidle, W.C. 1998. Environmental Isotope For Resolution of hydrology problems.
Environmental Monitoring Assessment 52: 389-410 Academic Publishers Printed
in Netherlands.
Figure 1: Establishment Local Meteoric Water Line (LMWL)
Figure 2: Map of the study area
Figure 3: Plot of isotopic composition of surface water and groundwater
Figure 4: Results of isotopic composition, Tritium at the study area