Faculty of Resource Science and Technology - ir.unimas.my PROFILE OF HYDROCARBONS AND HEAVY...the...
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THE PROFILE OF HYDROCARBONS AND HEAVY METALS IN SURFACE
SEDIMENTS FROM BATANG AI HYDROELECTRIC DAM, LUBOK ANTU,
SARAWAK
Nur Aein Binti Razali (24522)
Bachelor of Science with Honours
(Resource Chemistry)
2012
Faculty of Resource Science and Technology
THE PROFILE OF HYDROCARBONS AND HEAVY METALS IN
SURFACE SEDIMENTS FROM BATANG AI HYDROELECTRIC DAM,
LUBOK ANTU, SARAWAK
NUR AEIN BT RAZALI
This project submitted in partial fulfillment of the requirements for the degree of
Bachelor of Science with Honours
(Resource Chemistry)
FACULTY OF RESOURCE SCIENCE AND TECHNOLOGY
UNIVERSITY MALAYSIA SARAWAK
2012
ii
DECLARATION
I hereby declare that no portion of this work referred to in dissertation has been submitted in
support of an application for another degree or qualification to this university or any other
institution of higher learning.
_________________________
(Nur Aein Bt Razali)
Student Number : 24522
Department of Chemistry
Faculty of Resource Science and Technology
University Malaysia Sarawak
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ACKNOWLEDGEMENT
Alhamdullilah and most gratitude to Allah S.W.T. for the strength and courage to gave
me throughput completing this project to success.
I would like to thank the following individuals for helping me to complete my final
year project. Special thank to Prof Zaini Assim for his guidance, advice and support
throughout the period of my research. I also would like to thank to the laboratory assistants for
their cooperation, technical support, advice and help during this project.
I would like to thank, Master student Suhaila Gusni, my friends Ammar Ubaidullah
Rozali, Farahnasya Nabilah Huda Zahari, Widia Natasya Ariffin, Nur Atika Che Rusli and
Nur Hidayah Bt Kamarol Zaman, for their help, support and encouragement.
Lastly, I would like to express my gratitude to my parents Razali Yusof and Fauziah
Samdin, and family members for their love, moral and financial support that had given me the
strength to the completion my final year project.
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TABLE OF CONTENT
CONTENT Page
DECLARATION ii
ACKNOWLEDGEMENT iii
TABLE OF CONTENTS iv
LIST OF TABLES vii
LIST OF FIGURES ix
ABSTRACT x
ABSTRAK x
CHAPTER ONE: INTRODUCTION
1.1 General Introduction 1
1.2 Objectives of the Project 2
CHAPTER TWO: LITERATURE REVIEWS
2.1 Hydrocarbons in Aquatic Sediment 3
2.2 Heavy metals in Aquatic Sediment 5
2.3 Importance of Core Sediment in Environmental Studies 6
CHAPTER THREE: MATERIALS AND METHODS
3.1 Sampling Sites 8
3.2 Hydrocarbon in Sediment
3.2.1 Extraction of Geolipid 9
3.2.2 Column Chromatography Fractionation of Geolipid 9
3.2.3 Gas Chromatography-Flame Ionization Detector (GC-FID)
Analysis
10
3.2.4 Data Analysis
3.2.4.1 Qualitative Analysis 11
3.2.4.2 Quantitative Analysis 12
3.3 Heavy Metal Analysis
3.3.1 Sample Preparation 13
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3.3.2 Atomic Absorption Spectrophotometer (AAS) Analysis 13
CHAPTER FOUR : RESULTS AND DISCUSSION
4.1 Response Factors (RFs) for Hydrocarbons
4.1.1 Aliphatic Hydrocarbon 16
4.1.2 Polycyclic Aromatic Hydrocarbons (PAHs) 18
4.2 Aliphatic Hydrocarbon in Sediments of Batang Ai Hydroelectric
Dam
4.2.1 Distribution of Aliphatic Hydrocarbon 19
4.2.2 Biomarker Indices of Aliphatic Hydrocarbons in Sediments
4.2.2.1 Carbon Preference Index (CPI) 23
4.2.2.2 Pristane/Phytane (Pr/Phy) Ratio 23
4.2.2.3 The Ratio of Isoprenoid/n-Alkane 24
4.3 Aromatic Hydrocarbon in Sediments of Batang Ai Hydroelectric
Dam
4.3.1 Distribution of PAHs 25
4.3.2 Biomarker Indices of PAHs in Surface Sediments
4.3.2.1 Fluoroanthene/Pyrene (Fluo/Pyr) 30
4.3.2.2 Phenanthrene/Antharacene (Phe/Ant) 30
4.3.2.3 Benzo (a) anthracene /Chrysene (B(a)A/Chry) 30
4.4 Distribution of Hydrocarbons from Other Places
4.4. 1 Aliphatic Hydrocarbons 32
4.4.2 Aromatic Hydrocarbons 34
4.5 Heavy Metals in the Surface Sediments from Batang Ai
Hydroelectric Dam
4.5.1 Calibration of Standard Heavy Metals on AAS 35
4.5.2 Distribution of Heavy Metals in the Surface Sediments from
Batang Ai Hydroelectric Dam
40
4.5.3 Spatial Distribution of Heavy Metals in the Surface Sediments
from Batang Ai Hydroelectric Dam
4.5.3.1 Copper, Manganase, Zinc and Chromium 42
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4.5.3.2 Argentum, Nickel and Tin 45
4.5.4 Correlation Coefficient of Heavy Metals in the Surface
Sediments from Batang Ai Hydroelectric Dam
45
4.5.5 Sediment quality criteria and Environmental Status of Sediment
from Batang Ai Hydroelectric Dam based on Heavy Metals
Content
46
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION
5.1 Conclusion 48
5.2 Recommendation 49
REFERENCES 50
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LIST OF TABLES
Table
Page
Table 3.1 : The eluting solvent used during geolipid fractionation
10
Table 3.2 : Concentration of heavy metal standards in calibration
analysis on AAS
14
Table 4.1 : RFs value for aliphatic hydrocarbon standard
17
Table 4.2 : RFs value for polycyclic aromatic hydrocarbon (PAH)
standard
18
Table 4.3 : Distribution of aliphatic hydrocarbon in the surface
sediments from Batang Ai hydroelectric Dam from
different sampling stations
20
Table 4.4 : Biomarker indices for aliphatic hydrocarbon in surface
sediments at Batang Ai Hydroelectric Dam
25
Table 4.5 : Distribution of PAHs in the surface sediments from Batang
Ai hydroelectric Dam from different sampling stations.
29
Table 4.6 : Biomarker indices for PAHs in surface sediments at
Batang Ai Hydroelectric Dam
31
Table 4.7 : Concentration of aliphatic hydrocarbons in sediments from
other locations
33
Table 4.8 : Concentration of PAHs in sediments from other areas
34
Table 4.9 : Calibration curve equations of heavy metals analyzed
on AAS
38
Table 4.10 : The value of LOD, LOQ and sensitivity of heavy metals
analyzed on AAS
39
Table 4.11 : Distribution of heavy metal in the surface sediments from
Batang Ai Hydroelectric Dam
41
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Table 4.12 : Pearson correlation (PC) coefficient matrix between heavy
metals in surface sediments of Batang Ai Hydroelectric
Dam
46
Table 4.13 : Concentration of heavy metals in surface sediment from
Batang Ai hydroelectric dam in comparison with USEPA
guideline classification values for sediment metal
concentration (µg/g).
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LIST OF FIGURES
Figures
Page
Figures 3.1 : Location of sampling sites at Batang Ai hydroelectric Dam
at Lubok Antu District, Sri Aman, Sarawak.
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Figures 4.1 : Gas chromatogram of aliphatic hydrocarbon standards
obtained from GC-FID analysis
15
Figures 4.2 : Gas chromatogram of aromatic hydrocarbon standards
obtained from GC-FID analysis
15
Figures 4.3 : Gas chromatogram of aliphatic fraction from (a) ST1, (b)
ST2, (c ) ST3 and (d) ST4
21
Figures 4.4 : Gas chromatogram of aliphatic fraction from (a) ST5, (b)
ST6 and (c) ST7
22
Figures 4.5 : Gas chromatogram of aromatic fraction from (a) ST1, (b)
ST2 and (c) ST3
26
Figures 4.6 : Gas chromatogram of aromatic fraction from (a) ST4, (b)
ST5 and (c) ST6
27
Figures 4.7 : Gas chromatogram of aromatic fraction from ST7
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Figures 4.8 : Calibration graph of (a) Ni, (b) Cu, (c) Mn and (d) Pb
analyzed on AAS
35
Figures 4.9 : Calibration graph of (a) Cd, (b) Pb, (c) Zn and (d) Cr
analyzed on AAS
36
Figures 4.10 : Calibration graph of (a) Sn, (b) Ag, (c) As and (d) Bi
analyzed on AAS
37
Figures 4.11 : Spatial distribution of (a) Cu, (b) Mn, (c) Zn and (d) Cr in
surface sediment at Batang Ai hydroelectric Dam.
43
Figures 4.12 : Spatial distribution of (a) Ag, (b) Ni and (c) Sn in surface
sediment at Batang Ai hydroelectric Dam.
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Profiles of Hydrocarbons and Heavy Metals in Surface Sediments
from Batang Ai Hydroelectric Dam, Lubok Antu, Sarawak
Nur Aein Binti Razali
Department of Chemistry
Faculty of Resource Science and Technology
University Malaysia Sarawak
ABSTRACT
A study was carried out to determine distribution of hydrocarbons and heavy metals in fresh water surface
sediments from Batang Ai hydroelectric Dam, Lubok Antu, Sarawak. The surficial sediments from seven
sampling sites in the vicinity of Batang Ai hydroelectric Dam were analyzed for hydrocarbons (aliphatic and
aromatic) using gas chromatography flame ionization detector (GC-FID) and also heavy metal using atomic
absorption spectrophotometer (AAS). The total concentration aliphatic hydrocarbons varied from 804 – 1014.39
µg/g, while total concentration of PAH varied from 1248 - 7827 ng/g dry weights. Eleven heavy metals analyzed
are Ni, Cu, Mn, Pb, Cd, Zn, Cr, Sn, Ag, As and Bi. Sediment from sampling site ST2 which is near to the
outflow area were highly deposited with heavy metals compared to other sampling sites at Batang Ai
hydroelectric Dam. The concentration level of chromium (Cr) and copper (Cu) from site ST2 can be classified as
heavily polluted.
Key Words: Heavy metals, hydrocarbons, surface sediments, atomic absorption spectrophotometer (AAS), gas
chromatography-flame ionization detector (GC-FID)
ABSTRAK
Satu kajian telah dijalankan untuk menentukan taburan hidrokarbon dan logam berat dalam enapan permukaan
air tawar daripada empangan hidroelektrik Batang Ai, Lubok, Antu, Sarawak. Enapan permukaan daripada
tujuh lokasi pensampelan dalam lingkungan empangan hidroelektrik Batang Ai telah dianalisis untuk
hidrokarbon (alifatik dan aromatic) menggunakan kromatografi gas/pengesan pengionan nyalaan (KG-PPN)
dan juga logam berat menggunakan spektrofotometer serapan atom (SSA). Jumlah kepekatan hidrokarbon
alifatik adalah dalam julat 804 – 1014.39 µg/g, manakala jumlah kepekatan hidrokarbon aromatik adalah dalam
julat 1248 – 7827 ng/g berat kering. Sebanyak 11 logam berat yang telah dianalisis iaitu Ni, Cu, Mn, Pb, Cd,
Zn, Cr, Sn, Ag, As dan Bi. Enapan dari stesen pensempelan ST2 yang berdekatan dengan aliran keluar air
empangan menupukkan logam berat yang tinggi berbanding dengan stesen pensempelan lain di empangan
hidroelektrik Batang Ai. Kepekatan kromium (Cr) dan tembaga (Cu) dalam enapan dari stesen ST2 boleh
diklasifikasikan sebagai sangat tercemar.
Kata kunci: Logam berat, hidrokarbon, enapan permukaan, spektrofotometer serapan atom (SSA), kromatografi
gas/pengesan pengion nyalaan (KG-PPN)
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CHAPTER ONE
INTRODUCTION
1.1 General Introduction
The important sources of water in Malaysia are from the lakes and reservoirs. Lakes
and reservoirs function as storage basins for municipal and industrial water supply, agriculture
and hydropower. Water quality studies mainly focuses on water quality analysis, pollution
source identification and water quality improvement techniques (Sharip and Zakaria, 2008).
Batang Ai hydroelectric Dam serves Kuching and its surroundings with uninterrupted water
supply. Rapid land development activities upstream could contribute substantially to sediment
formation at lake bottoms. Creation of hydropower generation causes stratification problem.
Management measures on lake and reservoir requires understanding of key process that thrive
the ecosystem (Sharip and Zakaria, 2008).
Hydrocarbon generated by biological or diagnetic processes naturally at low content in
sediments and are a part of the naturally hydrocarbon baseline of ecosystem (Gao and Chen,
2008). According to Long et al. (1998), the presence of high concentration of certain
hydrocarbon has an adverse effect and may cause toxicity on aquatic ecosystem. Hydrocarbon
can become dangerous if they enter the food chain since several of the compound such as
PAHs is carcinogenic (Perelo, 2009). In order to measure the level of the total concentration of
hydrocarbon, the total aliphatic hydrocarbon (TAH) and polycyclic aromatic hydrocarbon
(PAH) were analyze after a single extraction.
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Heavy metals are widespread pollutants of great environmental concern as they are non
degradable, toxic and persistent with serious on aquatic ecology. Metal will be easily trapped
in the sediments it is because when sediment composed of fine sand and silt the sediment
become in stable condition. In general, industrialization and human activities are the main
contributors to heavy metals discharges into ecosystem. These metal subsequently enter into
the food chain directly or in directly and could give affect on human health (Hamzah et al.,
2001).
1.2 Objectives of the Project
The objectives of this project are :
a. to determine the profile of hydrocarbons and heavy metals in surface sediments from the
Batang Ai hydroelectric Dam,
b. to assess the spatial distribution of hydrocarbons and heavy metals in fresh water
sediments from Batang Ai hydroelectric Dam,
c. to evaluate the environmental status of sedimentary environment of Batang Ai
hydroelectric Dam based on the level of hydrocarbons and heavy metals in sediment.
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CHAPTER TWO
LITERATURE REVIEW
2.1 Hydrocarbons in Aquatic Sediment
Hydrocarbon is naturally occurring compounds and one of the important components
of sedimentary organic matter (Gao and Chen, 2008). According to Fadli (2010), the major
classes of hydrocarbons are n-alkanes, cycloalkanes, alkenes and aromatic compound. The
hydrocarbons synthesized by organisms occur normally in the biosphere. Among the biogenic
hydrocarbons, n-alkanes are the predominant group and they have been identified in many
species of plants and animals. Both terrestrial and marine organisms synthesize n-alkanes
where chains with odd carbon numbers predominate. N-alkanes of terrestrial origin are mainly
associated with higher plants, presenting chains with odd carbon numbers above n-C23. Marine
phytoplankton synthesize n-alkanes (lower than n-C23) with odd carbon numbers (Nishigima
et al., 2001).
The aliphatic hydrocarbon consist of both fully saturated normal alkane (paraffin) from
C2 to C60 with a smooth distribution between odd and even number of alkanes including
isoprenoid hydrocarbon. The aliphatic hydrocarbons comprise n-alkanes, branched alkanes,
isoprenoids and cyclic compounds, including geochemical biomarkers, such as hopanes and
steranes. Their analysis can be used to fingerprint spilled oils and provides additional
information on the source of hydrocarbon contamination and the extent of degradation of the
oil spill.
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Polycyclic aromatic hydrocarbons (PAH) are rarely found as products of biosynthesis.
Aromatic hydrocarbons contain one or more aromatic rings which are connected as fused ring
(naphthalene) or line ring (biphenyl) and normally consist of unsubsituted or parent aromatic
structure and like structure with multiple alkyl substitution. These hydrocarbons present a
higher toxicity for organisms. The PAH that are formed in processes of incomplete
combustion of gasoline, diesel oil and other refined petroleum products, generate particles
composed of PAH with high molecular weight, transported to the ocean by the atmosphere
and rivers . The PAH are associated with particulate and dissolved material and tend to be
deposited in the sediments. The presence of PAH in sediments can be utilized as an indication
of oil pollution (Nishigima et al., 2001).
Aliphatic and polycyclic aromatic hydrocarbons are sedimentary contaminants due to
their tendency to accumulate in sediments. Sedimentary aliphatic hydrocarbon has both
biogenic and anthropogenic sources (Peng et al., 2008). Biogenic sources are generated by
biological processes. Biological sources include terrestrial plant, phytoplankton, animals,
bacteria, microalgae and macroalgae (Nishigima et al., 2001). Anthropogenic source generated
by human such as industrials and domestic wates, emissions from the transportation, storage,
processing and combustion of fossil fuels (Doskey, 2000).
Human activities are significantly influenced the composition and distribution of
hydrocarbon and the substances coming from various sources including biogenic, diagenetic,
petrogenic and pyrogenic (Gao and Chen, 2008).
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2.2 Heavy Metals in Aquatic Sediments
Metals and metal compounds are natural constituents of all ecosystems, moving
between atmosphere, hydrosphere, lithosphere, and biosphere. Their distribution in the
environment is a result of natural processes (volcanoes, erosion, spring water, bacterial
activity) and anthropogenic activities (fossil fuel combustion, industrial and agricultural
processes) (Florea and Busselberg, 2005).
Heavy metal are released into the environment via airborne, contaminants, rural land
use activities, sewage sludge, mine waste, industrial waste, wastewater, pesticides and
fertilizer application (Hamzah et al., 2001). Metal may be presented in the estuarine system as
dissolve species, as free ion or forming organic complex with acid (Spencer and MacLeod,
2002).
The high concentrations of heavy metals are derived from anthropogenic input from
industrial activites around the estuary (Harikumar and Nasir, 2010). Some heavy metal are
potentially harmful (Cd, Hg, Pb) but some are essentially important to human health (Fe, Ca,
Mg). However high concentration of heavy metals could affect human health (Hamzah et al.,
2001). Exposure to heavy metals is potentially harmful especially for those metal-compounds,
which do not have any physiological role in the metabolism of cells. The ingestion of metals
via food or water could modify the metabolism of other essential elements such as Zn, Cu, Fe
and Se) (Florea and Busselberg, 2005).
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An adverse impact on aquatic ecosystem will occur by the heavy metals which are
mostly detachable from sediments and therefore contribute to hazardous waste. Thus, to
determine heavy metal portioning, selective chemical teaching techniques will be used. This
technique has been widely used to reconstruct the history of metal pollution (Hosono et al.,
2010).
Heavy metals from non degradable materials often accumulate causing biological
effect (Kar et al., 2008). A better understanding of the contaminant data to assists in the
interpretation and in making decision will be achieved by knowing the spatial and temporal
variance in the concentration of heavy metals in the aquatic environment. Therefore,
monitoring these metals is important for safety of the environment and human health in
particular.
2.3 Importance of Core Sediment in Environmental Studies
Bottom sediments consist of particles that have been transported by water, air, or
glaciers from the sites of origin in a terrestrial environment and have been deposited on the
floor of a river, lake, or ocean. Bottom sediment will also contain materials precipitate from
chemical and biological processes. Natural processes responsible for the formation of bottom
sediments can be altered by the anthropogenic activities. Sediments will accumulate due to the
effect from changes in the climate linked to the changes in the ocean (Kamaruzzaman et al. ,
2011). These accumulate in sediments via several pathways, including disposal of liquid
effluents, terrestrial runoff and leachate carrying chemicals originating from numerous urban,
industrial and agricultural activities as well as atmospheric deposition (Kassim, 2010)
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Sediment core analysis is very useful because it is commonly used to characterize
contamination in deeper sediments, documentation of historical changes in vertical
distribution of contaminants, reducing oxygen exposure needed for sample analysis and
correlate organism exposure to specific sediment layer (Jeng, 2007). The geochemical
characteristics of the sediments can be used to determine the weathering trend and the source
of pollution (Harikumar and Nasir, 2010).
Textural properties of lake sediments (e.g., porosity, water content) can serve as tools
for evolving and assessing the possible effects of sediment focusing, slumping and
inhomogeniety in the sediment composition. Sediment focusing is a process whereby water
turbulence moves sedimented material from shallower to deeper zones of a lake (Kassim,
2010).
Many researchers have used sediments to study the behavior of metals. The occurrence
of increase levels of metal especially in the sediments can be good indication of man induced
pollution of high level of heavy metals can often be attribute to anthropogenic influences
rather than natural enrichment of the sediment by geological weathering (Harikumar and
Nasir, 2010).
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CHAPTER THREE
MATERIALS AND METHODS
3.1 Sampling Sites
The location of sampling area at Batang Ai Hydroelectric Dam is shown in Figure 3.1.
Seven sampling sites were selected at Batang Ai Hydroelectric Reservoir. The surface
sediments were collected using stainless steel grab sampler. The sediment sample for heavy
metals analysis was placed in plastic bag, while the sediment samples for hydrocarbon
analysis was wrapped with aluminum foil. The sediment samples were stored in cooler box
during transportation. Upon arrived in UNIMAS laboratory, the sample was stored in freezer
at -18 0C until further analysis.
Figure 3.1: Location of sampling sites at Batang Ai Hydroelectric Dam at Lubok Antu
District, Sri Aman, Sarawak.
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3.2 Hydrocarbon in Surface Sediment
3.2.1 Extraction of Geolipid
The extraction and fractionation procedure for hydrocarbons analysis was carried out
according to procedure described by Zakaria et al. (2000). Extraction of geolipids from
sediments was performed using Soxhlet extraction method. Exactly 10 g (2 mm) sediment was
placed in the extraction thimbles (30 mm x 100 mm, Whatman) and extracted with 200 mL
dichloromethane for 8 hours extraction times. Exactly 50 µL of the internal standards
mixture containing (50 ppm of each component), anthracene-d10 and n-ecosene in
dichloromethane was spiked into the sample. Then, the crude extract was reduced to nearly
dryness using rotovap. The residue was diluted with dichloromethane and evaporates to
dryness by blowing with gentle stream of pure N2. The residue in vial is considered as total
extractable lipids (TEL).
3.2.2 Column Chromatography Fractionation of Geolipid
TEL was dissolved in 5 ml n-hexane and then subjected to fractionate on a column
chromatography (1.1 cm x 50 cm) which are packed with 7.5 g activated silica gel (60 mesh).
The eluting solvents used are listed in the Table 3.1.
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Table 3.1: The eluting solvents used during geolipid fractionation
Fraction Eluting solvent Group of compounds
extracted on silica gel
column chromatography
F1 40 mL hexane Aliphatic hydrocarbons
F2 40 mL mixture of dichloromethane: hexane (1:3,
v/v)
PAHs
The total aliphatic hydrocarbon (TAH), F1 fraction was collected by eluting the
chromatography column with 40 mL of hexane, while the PAH fraction, F2 was collected by
eluting the column with mixtures of 40mL methylene chloride: hexane (1:3, v/v). Each
fraction were then evaporated and transferred to a vial with 1 ml of dichloromethane. The
solvent in each vial was evaporated just to the point of dryness under a gentle stream of
nitrogen.
3.2.3 Gas Chromatography- Flame Ionization Detector (GC-FID) Analysis
Computerized capillary gas chromatography analysis Clarus 680 series equipped with
standard flame ionization detector (FID) was used to perform gas chromatographic analysis of
hydrocarbon fractions, F1 and F2. The FID response proportionately to the number of CH2
groups introduced to the flame. Prior the GC-FID analysis, samples was diluted with 100 µL
hexane in 3 mLl capacity vial. Exactly 1 µLl sample was injected in less split mode and
separated on fused silica capillary column (25 m x 0.22 mm internal diameter 0.25 µm film
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thickness) of DB-5 phase (crosslinked 5% diphenyl and 95% dimethylpolysiloxane). The
temperature in the oven were maintained 500C for 5 minutes and temperature was ramped at
310 0C at a rate 6.5
0C/min. The final temperature was held for 16.5 minutes. Temperature for
injector and detector was set at 280 0C and 320
0C respectively. The H2 compressed air and N2
gas flow was set at 30 mL/min, 400.0 mL/min and 25.0 mL/min respectively.
3.2.4 Data Analysis
3.2.4.1 Qualitative Analysis
The retention time for n-alkane on GC-FID detector were determined by comparing the
retention time with n-alkane in a mixture of standards. However, n-alkane standards only
consist of even number carbon n-alkane. The qualitative analysis for odd number was
determined based on the two adjacent alkanes. As for isoprenoid pristane is calculated by
average retention time of C17 - C18 and phytane is calculated by average retention time of C18-
C19.
Various biomarkers indices can be used in order to determine the origin of organic
matters in the surface sediment samples. The ratios of pristine/phytane, phytane/C18,
pristane/C17 and nC25/nC15 were calculated as biomarker indices for aliphatic hydrocarbon.
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The carbon preference index (CPI) was calculated according to Bray and Evans (1961)
as equation 3.1:
CPI = 1 C25+C27+C29+C31+C33 + C25+C27+C29+C31+C33 …equation 3.1
2 C26+C28+C30+C32+C34 C24+C26+C28+C30+C32
where, Cn = alkane with n number of carbons
3.2.4.2 Quantitative Analysis
The relative response factor (RFs) for even number carbon n-alkanes in F1 and each of
the PAH compound for F2 determined according to Howsam and Puttmann, (1989) as
equation 3.2:
RFs = (Cstd / Astd) x (Ais x Cis) … equation 3.2
where, Cstd = Concentration standard analyte
Astd = Gas chromatogram for standard analyte
Ais = Gas chromatogram for internal standards
Cis = Concentration of internal standards
RFs for odd carbon of n-alkane were calculated using average of two adjacent even
numbers n-alkane carbon. The RFs are used in the calculation of the concentration for
individual alkane in sediments by using the equation 3.3:
Concentration of analytes = (Cis/ Ais) X Ax X RF …equation 3.3
where, Ax = Chromatogram for analyte x
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3.3 Heavy Metal Analysis
3.3.1 Sample Preparation
The sediment sample preparation was carried out according to procedure described by
Binning and Baird (2001). The sediment was air dried in petri-dishes, then ground into a
powder. Approximately 0.5 g of each dried sediment sample was placed in a beaker and mixed
with 20 mL Aqua Regia (cHNO3: cHCl; 1:3; v/v) and allowed to stand overnight. The mixture
was heated to near dryness and allowed to cool before 1 mL of a HNO3 solution was added.
The sediment samples was then allowed to stand overnight and then filtered through Whatman
No 41 filter paper. The filtrates was transferred to a 100 mL volumetric flask and made up to
the mark with deionized water.
3.3.2 Atomic Absorption Spectrophotometer (AAS) Analysis
The solution was analyzed for the metals content using AAS model Thermo Scientific
iCE 3000 SERIES using the calibration curve method. The samples were analyzed for Ni, Cu,
Mn, As, Pb, Cd, Bi, Zn, Cr, Sn and Ag. Prior to AAS analysis calibration solution were
analyzed. The concentration of respective heavy metals standard used during calibration
analysis is shown in Table 3.2.