ABSTRACT
The study assessed the physicochemical properties and heavy metals (chromium (Cr), zinc (Zn), cadmium (Cd), and copper (Cu)) levels in sawdust, soil and plants at Ahiaeke timber market, Umuahia, Nigeria using Flame Atomic Absorption Spectrometer (AAS) in order to ascertain the impact of timber market on the surrounding environment. Sawdust was collected randomly from fifteen different sampling points in four cardinal points (i.e. three sampling points each at north (N), south (S), east (E), west (W), and at the center (C) of the dumps from three dump. Soil samples were collected randomly from twelve different sampling points at 0-10, 11-20, and 21-30 cm soil depth with well cleaned Dutch soil auger in four cardinal points (i.e. two sampling points each at north (N), south (S), east (E) and west (W) of 20, 40, 60 and 80 m from the center of the sawdust wastes each dumpsite, and control was taken 500 m away from dumpsite. Plant samples were also collected at the same point where soil was sampled. The highest values of P (1.103±0.12 %), Organic carbon (27.98 ± 0.021%) and K (2.2± 0.04 %) of sawdust particles were obtained at sawdust dump 2 and these values are significantly (P< 0.05) higher than their corresponding values in sawdust dump 1 (0.805±0.013, 24.15±0.165 and 1.83±0.061 %) and sawdust dump 3 (0.94±0.050, 25.614±0.785 and 2.073±0.006 %). The mean values of soil pH ranges from 6.03±0.115 to 3.67±0.28 indicating that the soil is acidic. The highest concentration of Zn (51.00±1.84 mg/kg) and Cr (0.170±0.014 mg/kg) was observed at the sawdust dump 2; Cu (8.24±0.60 mg/kg) was obtained at the sawdust dump 1 while Cd (4.72±0.071 mg/kg) occurred at the sawdust dump 3. The values of the highest concentration of Zn (119.7±7.02 mg/kg), Cu (75.85±4.80 mg/kg) and Cd (22.39±3.30 mg/kg) in soil were observed in 0-10 cm depth at the distance of 20 m. The values of Zn (119.7±7.02 mg/kg) and Cd (22.39±3.30 mg/kg) in soil is above the maximum permitted levels of 60 mg/kg (Zn) and 0.1 mg/kg (Cd) established by the Codex Alimentarius Commission. The highest concentration of Zn (34.70±7.05 mg/kg), Cu (5.34±0.11 mg/kg) and Cd (2.94±0.515) in plants was assimilated by Centrosema pubescence. The level of Cd in plants is well above the permissible limit (PL) 0.3 mg/kg set by FAO/WHO for vegetables and herbs. Consumption of such contaminated C. pubescence can be a route of entry of Cd in grazing animals’ vis-à-vis the people who depend on such herbivores for protein.
TABLE
OF CONTENTS
Title
page i
Declaration
ii
Certification
iii
Dedication
iv
Acknowledgment v
Table
of Contents vi
List
of Tables
ix
List
of Figures x
List
of Plates xi
Abstract xii
CHAPTER 1:
INTRODUCTION
1.1 Background
of the Study
1
1.2 Problem Statement
3
1.3 Aim and
Objectives of the Study
3
1.4 Justification of the Study
4
1.5 Scope of the Study
4
CHAPTER 2:
LITERATURE REVIEW
2.1 History of Sawmill in Nigeria 6
2.2 Approaches and
Challenges to Sawdust Waste Disposal 7
2.3
Soil Quality 10
2.3.1 Organic Matter 11
2.3.2 Soil pH 11
2.3.3 Nitrogen 11
2.3.4 Phosphorus 12
2.3.5 Soil
texture 12
2.4 Physicochemical Parameters of
Soil and Environmental
Implication
13
2.5
Heavy Metal in Soil 14
2.5.1
Heavy metal and contamination pattern 17
2.6 Effect of Heavy Metals Polluted Soil on Plant 19
2.7 Summary of Literature Review 23
CHAPTER 3: MATERIALS AND
METHODS
3.1
Study Area Location 24
3.2
Sampling and Sample Collection 25
3.2.1
Sawdust sample collection
25
3.2.2
Soil sample collection 31
3.3.3
Plant sample collection
31
3.3 Material Preparation 31
3.3.1 Sawdust sample preparation 32
3.3.2 Soil sample preparation 32
3.3.3 Plants sample preparation 32
3.3.4 Stock solution preparation 32
3.4 Labouratory Experimental
Procedures 33
3.4.1 Sawdust mineral experimental
procedure 33
3.4.2 Sawdust heavy metal
experimental procedure 35
3.4.3
Soil physicochemical properties experimental procedure. 36
3.4.4
Soil heavy metal experimental procedure 39
3.4.5
Plant heavy metal analysis 39
3.5
Experimental Design and Statistical Analysis 40
CHAPTER 4: RESULTS AND
DISCUSSION
4.1
Mineral Content (%) in Sawdust
41
4.2
Heavy Metal Concentration in Sawdust 42
4.3
Physicochemical Characteristics of Soil at the Study Area 46
4.4
The Chemical Properties of Soil at the Study Area 48
4.5
Heavy Metal Concentration in Soil Sample at Dumpsite 51
4.6
Heavy Metal Concentration in Plant Sample 54
4.7
Discussion
57
CHAPTER FIVE: CONCLUSION
AND RECOMMENDATION
5.1
Conclusion 66
5.2
Recommendation 67
References 68
Appendices 77
LIST OF TABLES
3.1: ANOVA Table 40
4.1: Mean± SD of Sawdust Mineral Contents (%) at the Study Area 41
4.2: Mean ± SD of Heavy Metal Concentration (mg/kg)
in Sawdust at the
Study Area 42
4.3: Mean ± SD of Physical properties (%) of soil
samples at sampled distances 46
4.4: Mean ± SD of Chemical Properties (%) of Soil at
the Study Area 47
4.5: Mean ± SD of heavy metal concentration (mg/kg) in
Soil Samples 51
4.6: Comparison of result with
International Standard 53
4.7: Mean
± SD of Heavy Metal Concentration (mg/kg) in Plant Samples 54
LIST OF FIGURES
3.1: Map of Nigeria showing Abia State 26
3.2: Map of Abia State showing Umuahia
North
27
3.3:
Map of Umuahia North showing Ahia-Eke Timber Market 28
3.4:
Map showing the sampling point of collection at dumpsite 29
4.1: Zinc concentration of sawdust at
the dumpsite
43
4.2: Cadmium concentration in sawdust
at the dumpsite.
44
4.3: Chromium concentration of
sawdust at the dumpsite
45
4.4: Particle size distribution of
the soil of Ahiaeke timber market. 48
4.5: Heavy metal concentration of
soil samples at various distance and depth.
52
4.6: Heavy metal concentration of
plants at various distances at the study area. 55
LIST
OF PLATES
1: Sawdust waste at the dumpsite
30
CHAPTER
1
INTRODUCTION
1.1
BACKGROUND
OF THE STUDY
The environment is continuously being
contaminated by various human activities, such as industrial production,
agricultural processes, and mineral exploitation, food processing, commercial,
social, and domestic activities that generate contaminants like heavy metals.
The release of heavy metal is of great concern the world over since metal are
non-biodegradable (Wu and Zhang, 2010) and cannot be detoxified and removed by
metabolic activities once they are available in the environment. This can
result to the building-up of toxic levels in terrestrial and aquatic ecosystems.
Metals such as zinc (Zn), copper (Cu), manganese (Mn), iron (Fe), and nickel
(Ni) are required by living organism to aid in their metabolic functions but
are toxic when they exceeded their normal threshold in soil through external
addition. Non-essential metal such as lead (Pb), chromium (Cr), mercury (Hg)
and cadmium (Cd) are not necessary for growth of living organisms
(Kabata-Pendias, 2011).
Plants growing on metal contaminated
soil tend to take-up metals from soil solution via the roots and translocate it
to the stems and the leaves. Their (metals) chemical form in soil can strongly
influence their uptake by plants (Pitchell and Anderson, 1997) either as mobile
ions present in the soil solution through the roots (Davies, 1983) or through
foliar absorption (Chapel, 1986) resulting in bioaccumulation of the elements
in plants tissues (Amusan et al.,
2005). This however, is dependent on the type of metal, plant species and plant
part (Juste and Mench, 1992). The exploitation of such trees at maturity and
subsequent processing at timber markets will result to release of metal in form
of dust particles in the environment. The increasing demand for wood as building
material, for furniture purposes, sculptural work, and in various industries
vis-à-vis poor planning and ineffective implementation of budget allocation for
waste collection and disposal by the Government has resulted to high volumes of
sawdust waste at dumpsite in Umuahia timber market. The decomposition of the
sawdust may culminate to contamination of the immediate surroundings via
leaching of metals and other chemical pollutants into the soil. The concomitant
effect is possible ecological imbalance and deterioration in the quality of
plant products around the vicinity. Similarly, it may result to bioaccumulation
of metals in plants hence; culminate to bio magnification in food chain via
herbivorous animals and man that depend on such plants for food and medicine.
Quite a number of studies on sawmilling or wood processing activities have been
carried out in terms of the health effects of workers of the sawmills (Boateng
and Amedofu, 2004; Ugheoke et al.,
2006; Oke and Oyedare, 2006; Arimoro et
al., 2007; Verma et al., 2007;
Lasode and Balogun, 2010; Bello and Mijinyawa, 2010; Edith and Nkwocha, 2012),
heavy metals in sawdust particles (Nwajei and Iwegbue, 2007; Ncube and Phiri,
2015) and soil (Ezekiel et al.,
2013). From the researcher’s view, literature searched shows that no work has
been done on heavy metal accumulation in soil, sawdust and plants at timber
market or sawmills. This study, therefore, attempted to fill this gap by
investigating heavy metal distribution in soil and accumulation in plants at new
timber market, Ahiaeke, Abia State, Nigeria. The specific objectives were to
identify some metals in sawdust, their distribution in soil at various depths
and distances and accumulation in plant species around the timber market
sawdust dumpsite.
1.2
PROBLEM
STATEMENT
Due to rapid civilization and
urbanization, the growing demand for wood products as building materials,
sculpture, furniture, artistic designs, decorative purposes and domestic use from forest in various industrial sectors has
led to an increase in sawmill industries in Umuahia, Abia State and the rain
forest zone of Nigeria at large. This accounts for 93.32% of the total number
of wood based industries in Nigeria (Fuwape, 2001). An estimate of wood residue
generated by Nigerian sawmills to be 1.72 million m for the year 1981 which
rose to 3.87 million m by 1993 by Badejo, (2001) estimate. Apart from its
economic and social contribution to our society, it has contributed negatively
to the environment and human health as wood processing generates large volume
of sawdust which is indiscriminately disposed around the site without adequate
monitoring, management and consideration for the environment (Osakwe, 2013).
Due to the uncontrolled dumping of
sawdust in the vicinity of timber, it is anticipated that the soil quality may
be adversely affected with heavy metals and plants growing on such site may
take up metals alongside the nutrients and thus entering the food chain. It is
therefore of the utmost importance to monitor the environment constantly, to
prevent disasters arising from the introduction of heavy metals into soil,
plants, particularly by the activities process of sawmill industry and also to
alert people in that vicinity on the possible health risk associated with
farming or cutting of fodder for herbivores (i.e. domestic) or consuming crops
from such land.
1.3 AIM AND OBJECTIVES OF THE STUDY
The aim of this study was
to assess the metal content (Cd, Cu, Cr and Zn) in sawdust, soil, plants at
Umuahia, New Timber Market, Abia State. The aim was achieved through the
following objectives.
1)
Assessment of some
selected chemical properties and heavy metals in sawdust at different sampled
dumpsite.
2)
Determination of the
physicochemical properties and selected heavy metals in soil at various
distances and depth in sawdust dumpsites.
3)
Compare the heavy metal
concentration in the dumpsite to the International Standard (Dutch criteria and FAO/WHO Codex Alimentarius
Commission)
4)
Assessment of the level of accumulation
of selected heavy metal in plants grown at various distances around the sawdust.
Heavy metals can be hazardous in
their ability to cause cancer or neurological damages (Shemang, 2010). The
determination of the levels of Chromium (Cr), Cadmium (Cd), Copper (Cu), and
Zinc (Zn) in sawdust, soil and plants at the new timber market, Ahiaeke, Umuahia,
Nigeria would assist in knowing the concentration of heavy metals present in woodwaste
dumpsite, and in order to ascertain the potential threats of heavy metals
uptake by plants and consumers of such plants. On the other hand, this study will
make basis for further studies/monitoring of heavy metals concentrations in
sawdust, soil, and plants at Umuahia timber market. Moreover, the outcome of
this study will be of great interest to the ministry of environment and other
environmental agencies in Umuahia, Abia State in monitoring activities on the
level of heavy metal and providing remedial action to take to remove the heavy
metals.
1.5
SCOPE OF THE STUDY
The
scope of the study focused mainly on collection of samples from sawmill industry
in Ahia-eke, new timber market, and analyzing these samples to determine the
concentration of heavy metals (Zn, Cu, Cd, Cr) in soil, plants and sawdust; and
also to analyze the physicochemical parameters of soil and mineral content of
sawdust. This study is limited to analysis of heavy metal and physiochemical properties
at distance of 20m, 40m, 60m, 80m and 500m from the point of discharge.
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