A20
VERTICAL PROFILE OF HEAVY METALS AND
SEDIMENTATION RATE OF MEANDER CORE SEDIMENTS OF
KERTEH RIVER, TERENGGANU, MALAYSIA BY USING PB-210
DATING TECHNIQUE
Qatrunnada Mohd Nasir1, Hasrizal Shaari12, Khawar Sultan2, Che Abd. Rahim
Mohamed3 & Joseph Bidai1
1
Institute of Oceanography and Environment, UMT
School of Marine Science and Environment, UMT
3
School of Environmental and Natural Resource Sciences, UKM
Email: [email protected] , [email protected]
2
Downcore variations of heavy metal (Al, Fe, Mn, Na, Ca, Mg, Ba, Sr, Zn, Pb, Cr, Cu, and
Ni) concentrations and sediment texture of core samples (interval thickness ~2 cm) from
meander deposits was investigated. This work focused on Kerteh River mangroves in a
meander setting along the east coast of Peninsular Malaysia. The river loop sediment
deposits and meander cutoff preserved recent depositional history. All measured metals
showed a systematic change with depth of increasing (Mn, Ca, Sr, Zn, Pb, Cr and Ni) or
decreasing (Al, Fe, Na, Mg, Ba, and Cu) in concentration. Most metal contents showed a
significant change at the depth of 60 to 70 cm at the downstream sampling location
indicating a sudden change in depositional environment. Sediment age was determined
by 210Pb activity concentrations as vertical variations in metal contents. The age-depth
model indicated that the age of sediments of upstream location is younger (≤ 30 years)
than the downstream sediments (≤ 150 years). It, therefore, shows the great potential as
recent historical record of environment at oxbow loop sediment deposition. However, the
upstream location recorded anthropogenic contribution probably due to the industrial
development in this region as indicated by metal enrichment (Zn, Pb, Cr and Ni).
Sediments are classified as sandy loam to silty loam in texture with average mean size of
3.47 – 5.92 µm (upstream) and 1.52 – 6.47 µm (downstream) respectively, along the flow
path. Overall, grain size distribution showed a bimodal distribution patterns. The
sedimentation rate was determined to be 4.68 cm/year at the upstream and 0.73 cm/year
at the downstream sampling location. Significantly higher sediment deposition rate at the
upstream meander location is due to the free connection with the river. High deposition
and removal of sediments at the upstream location allowed only younger layers of
sediments to be deposited. Total organic carbon (TOC) content ranged between 0.85%
and 5.60% with significantly higher values at downstream (average ~4.13%). This study
is important in showing that the river meander loops deposits carry huge potential of
recent environmental record.
Keywords: Sedimentation, Core, Pb-210, Metals, River, Meander, Tropical, Malaysia
INTRODUCTION
Mangrove forest is very special as it has a sectioning zone which has basic geomorphic
features of braided-to-meandering channels (Naiman et al., 2005). This system plays an
important role in sediment exchanges with adjacent mud flats and open coastal waters by
providing a mechanism for trapping sediment (Kamaruzzaman and Ong, 2008). Most of
the researchers agreed that sediment cores are the best tools in order to study the history
of the environment as they storing the past environment condition (Ellison and Stoddart,
1991; Naiman et al., 2005). The data reading obtained from mangrove sediment will be
more precise and accurate (Santen et al., 2007). The enhancement of natural radioactivity
is the result of human activities; mainly from the mining of ores, gas and coal burning,
production of fertilizer, which are reactive particles that tend to bind with particles
(Sabuti and Mohamed, 2013). One of the naturally producing radionuclides is 210Pb, a
useful tracer for this study to establish the age-depth model. 210Pb dating method is an
ideal tracer for sediment deposited during the last 100 - 150 years (Blais et al., 1995;
Bakar et al., 2011). From an ecological perspective, adjustments in meandering rivers
especially those related to human-induced effects, often produce accelerated rates of
geomorphic change that result in disturbance of stream ecosystems (Rhoads, 2003). The
purpose of this study is to understand the evolution of the intertidal zone of the
Terengganu and predict the sustainability of mangrove ecosystem in Terengganu and in
the East Coast Peninsular Malaysia generally.
METHODOLOGY
This study was conducted at Kerteh River, Terengganu on the East Coast of Peninsular
Malaysia. Kerteh River shows the schematic river corridor in a braided-to-meandering
transition zone. This river is approximately 23 km in length and receives runoff from its
main tributaries such as Ranggun River, Mat Ikat River and Cabang River before
discharging into South China Sea. The land use within the catchment is predominantly
rural and agricultural activities. There is also Kerteh Airport located about 5 km from the
sampling site area. The sampling site is located about 2.3 km from the river mouth of
Kuala Kerteh and 400 m from the bridge ports of Kerteh. The two sediment cores at
upstream (KR1) and downstream (KR2) have been sampled at mudflat of the river.
Figure 1. Location of the cores, Kertih River at Terengganu, East Coast Peninsular
Malaysia.
The cores were sampled using a PVC corer with a diameter 2.5 inches penetrated into the
sediment, vacuumed out slowly to reduce the pressure and to maintain the structure of the
cores. Both cores been cut every 2 cm and dried in an oven at 60˚C. Walkley-Black acid
oxidation method for total organic carbon, Inductively Coupled Plasma Mass
Spectrometry (ICP-MS) for trace element had been conducted. The particle size analysis
had been done by using Particle Size Analyzer (Malvern Master-Sizer) and for the age
sediment dating conducted by using alpha-beta Counter Spectrometer (210Pb activity
concentration). The determination method of 210Pb activity is by using the IAEA-315
(Radionuclides in marine sediment) as a reference material. The Pb-210 activity in a layer
deposited at time, t in the past can be determined using the following equation:
Po-210 Activity (dpm) = Po-210 Added (dpm) x Po-210 Peak Area x PDC /(Po210 Peak Area)
where the PDC = e-λ×Δt is the plating date correction, with λ for Po-210 = 1.833 yr-1, and
Δt = date counted – date plated.
RESULT AND DISCUSSION
From the particle size characteristic analysis, the core at downstream have a silty loam
texture located at the area with slower water velocity due to the cut off river. The new
straighter river at upstream has changed the river flow led to the increasing finer-sized
sediment deposit and the formation of mudflat at downstream. The sedimentation rate for
upstream is 4.68 cm /yr and 0.73 cm /yr for downstream as show in the Figure 2 below.
The higher sediment deposition rate at the upstream meander as it is connected with the
river. The bottom depth of upstream core is during the year of 1988 at 122 cm depth.
While for downstream, at depth 104 cm of the core is on 1872 years. The age of
sediments at upstream is much younger (~120 years) as compared to the upstream
sediments. High deposition and removal of sediments at the upstream location allowed
only younger layers of sediments to be deposited.
Figure 2. Profile of sedimentation rate in sediment cores
The particle size of sediment is important in controlling the content of the element.
Average content are mostly decreased when the size increased. In addition, particle size
plays significant role in the accumulation between water and sediments. Table below
shows the value of correlation between heavy metal and sediment mean size at upstream
and downstream of Kerteh River. Among the 13 element, the concentration of Ni shows
no correlation with particle size for both cores. Ca and Cr also show no correlation with
particle size at upstream. Zn, Mg and Fe show a very high correlation with the particle
size with same r-value (0.92) at downstream. While at the upstream, only Pb shows the
highest value of correlation with particle size (r =0.58). Overall, the correlation of heavy
metals show a higher value with the downstream sediment mean size compared to the
upstream.
Table 1. Value of correlation (r) with strength correlation
Correlation coefficient (r)
Strength of relationship
< 0.20
Very negligible relationship
0.20 - 0.40
Low correlation;definite but weak related
0.40 - 0.70
Moderate correlation;substantial related
0.70 - 0.90
High correlation;marked relationship
Very
high
correlation;very
reliable
> 0.90
relationship
Table 2. Value of correlation between heavy metals and sediment mean size at Kerteh
River.
Correlation (r)
Al
Zn
Upstream
0.45
0.32
Downstream
0.87
0.92
Ca
0.46
Mg
Fe
Pb
Na
Ba
0.24
0.37
0.58
0.18
0.03
0.92
0.92
0.91
0.88
0.66
Cr
0.59
Cu
Ni
Sr
Mn
0.53
0.06
0.08
0.86
0.74
0.89
CONCLUSION
The vertical distribution of heavy metal (Al, Zn, Ca, Mg, Fe, Pb, Na, Ba, Cr, Cu, Ni, Sr
and Mn) concentrations showed a systematic trend of increasing and decreasing in core
samples. The distribution of particle size and texture classification were studied and
related with the age sediment dating analysis. The fine grained sediments tend to absorb
more elements compare to coarse grained sediments. As downstream have a much more
fine grained sediments, the results of heavy metals shows a significant correlation with
the particle size. The organic carbon at downstream is much higher due to the slow
velocity of water that lead to the accumulation of organic matter at downstream
compared to upstream which have lower organic carbon. There is a transition period
separating two distinct depositional environments between upstream and downstream
location. The observation is supported by vertical change patterns of particle size, heavy
metals and organic matter content. This transition might be related to fluvial landform
evolution from meander loop to the oxbow resulting in changes in supply and transport of
sediments. This transition might also be related to the anthropogenic impact (land use
changes) on the geometry of the meander loop, hence changes in sedimentation
environment.
ACKNOWLEDGEMENT
This research work was supported by the funds research culture, Department of Higher
Education (RAGS).
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