ABSTRACT
The uptake and accumulation of lead, nickel, cadmium, chromium and arsenic in
the root, stem leaves and fruits of okra (Ablmoschus esculentus) and pepper
(Capsicum annum), and the leaves and root of lettuce (Lactuca sativa) at different
metal concentrations in the soil was studied. The physio-chemical properties of the
soil indicate: total nitrogen as 0.21%, organic matter 3.32%, cation exchange
capacity (CEC) was 17.20 mol/kg, clay 20%, silt 46% and sand 34%. The soil pH
was weakly acidic and the textural class was loam. The result obtained for uptake
and accumulation showed that different plants had different preferences for each
metal at the concentration used. The variation in the concentration of applied metal
ion increased.
TABLE OF CONTENTS
Title page ………………………………………………………………………… i
Declaration……………………………..…………..…………………………….. ii
Certification…………………………………….………………………………. iii
Dedication………………………………………………………………………. iv
Acknowledgment……………………………………………………………….. v
Abstract………………………………………………………………………….. vii
Table of Contents……………………………………………………………….. ix
CHAPTER ONE
1.0 Introduction……………………………………………………………….. 1
1.1.0 Description of the Species…………………………………………………. 2
1.1.1 Origin of Pepper (Capsicum annum)………………………………………. 3
1.1.2 Growth, Development and Ecology……………………………………….. 3
1.1.3 Uses of Capsicum …………………………………………………………..4
1.1.4 Origin of Okra (Abelmoschus esculentus)………………………………… 5
1.1.5 Growth, Development and Ecology of Species…………………………… 5
1.1.6 Origin of Lettuce (Lactuca sativa) ………………………………………… 6
1.1.7 Growth, Development and Ecology of Species (Lettuce)………………… 6
1.1.8 Uses of (Lactuca sativa)…………………………………………………… 7
1.2 Statements of the Problem………………………………………………… 7
1.3 Aim and Objectives of the Study…………………………………………. 7
1.4 Justification for the Study……………………………………..…………. 8
9
CHAPTER TWO
LITERATURE REVIEW
2.0 INTRODUCTION: Uptake of metals by
plant………………………………… 9
2.1 Variation in Trace Element Uptake and Accumulation in Plant
Tissues……… 13
2.1.1 Cadmium
(Cd)………………………………………………………………… 13
2.1.2
Nickel………………………………………………………………………….
. 13
2.1.3
Chromium……………………………………………………………………..
.. 14
2.1.4 Lead
(Pb)………………………………………………………………………. 14
2.1.5
Arsenic………………………………………………………………………
… 15
2.2 Factors Affecting the Uptake of Trace
Elements……………………………… 16
2.3 Trace Elements and Human
10
Health…………………………………………… 19
2.4 Lead in the Soil, Plant and Human beings…………………………………….
20
2.4.1 Nickel (Ni)……………………………………………………………………
21
2.4.2 Lead……………………………………………………………………………
22
2.4.3 Chromium
(Cr)………………………………………………………………… 22
2.4.4 Arsenic
(As)…………………………………………………………………… 23
2.4.5 Cadmium (Cd)……………………………………….…………………………
24
CHAPTER THREE
3.0 Experimental………………………………………………………………
….28
3.1 Sample collection and treatment…………………………………………… ..
.28
3.1.1 Collection of the soil…………………………………………………………
.28
3.1.2 Collection of the seeds………………………………………………………
..28
11
3.1.3 Soil treatment analysis…………………………………………………… …..
28
3.2 Reagents………………………………………………………………………
29
3.3 Determination of the physico-chemical parameter of the soil
used……………30
3.3.1 Determination of silt, clay and sand………………………………………..…
30
3.3.2 P
H
Determination…………………………………………………………..…
32
3.3.3 Organic carbon (WALKLEY- Black)………………..………………………
33
3.3.4 Total nitrogen in soils……………..…..……………………………………..
33
3.4 Preparation of solutions applied to soil………………………………………
36
3.4.1 Lead stock solution
……………………………………………………..…….36
3.4.2 Nickel stock
solution…………………………………………………….….…36
3.4.3 Chromium stock
12
solution…………………………………………………..…37
3.4.4 Cadmium stock
solution………………………………………………………37
3.4.5 Arsenic stock solution
………………………………………………..………38
3.5 Digestion of soil (Allen et al
1974)……………………….……………..……38
3.6 Digestion of plant samples (Allen et al
1974)……………………………..…38
3.7 Principle and Application of Atomic Absorption
Spectrometry…………..…39
3.8 Analytical
techniques…………………………………………………………40
3.8.1 Preparation of Calibration curves……………………………………………
40
3.9 Determination of metal concentration in the samples…………………….…
41
3.10 Determination of arsenic using X-Ray Fluorescence (ED –XRF)………
…..41
CHAPTER FOUR
13
4.0 Results and Discussions………..……………………………………………………
43
4.1 Physico-chemical analysis of the soil used……..………………………….…………
43
4.2 Uptake of metals by plants……………………………………………………….…
45
4.3 Lead in lettuce, okra and
pepper………………………………………………………57
4.4 Nickel in lettuce, okra and pepper……………………………………………………58
4.5 Cadmium in lettuce, okra and
pepper………………………………………….……..60
4.6 Chromium in lettuce, okra and pepper………………………………………….…….61
4.7 Arsenic in lettuce, okra and pepper
…………………………………………….…… 64
4.8 Correlation studies…………………………………………………………..………
66
4.9
Conclusion…………………………………………………………………..………..
72
4.10 Recommendations………………………………………………………….…………72
References ……………………………………………………………….………….74
Appendix …………………………………………………………………….………86
CHAPTER ONE
INTRODUCTION
High heavy metals’ contamination of soils is one of the major
environmental problems. Increasing industrial pollution, urban activities, and
agricultural practice lead to a build-up of toxic levels of cadmium, copper,
lead, zinc, nickel (Dudka et al, 1996). When accumulated in excess in plant
tissues, these metals cause alterations in various vital growth processes such as
mineral, nutrition, transpiration, photosynthesis, enzyme activities related to
metabolism and biosynthesis of chlorophyll and nucleic acids (Doncheva et al,
1996).
Plants and animals need specific elements for them to grow and function
properly. At least 16 elements are essential for healthy growth and
development of higher plants (Wild, 1988). Carbon, hydrogen and oxygen are
derived from air and water while the other elements are supplied by the soil,
and enter the roots. These include trace elements, which are essential to plants
but may be required by animals (Brian, 1964, Jones and Clement, 1973).
Chromium availability in the soil depends on several soil conditions,
such as pH, or redox potential (Bartlett and Kimble, 1976). The solubility of
chromium and other metal salts can be increased or decreased depending on
the presence of other elements in the soil/plant system (Smith and Demchak,
1987). When chromium is in the soil solution, it can be taken up by roots and
accumulated and distributed within the plant. This fact may lead to interactions
19
between chromium and other essential elements, which can have a significant
effect on the nutrient concentration and distribution in the plant as well as
modifying some physiological processes affecting plant morphology.
It has been reported that plant grown in sludge-treated soils take up
heavy metals (Bojakowska and Kochary, 1985; Adeniyi, 1996). These toxic
metals taken up by plant roots and passed to stems and leaves, which are
eventually consumed by animals and humans. The amount of these metals
present in the different parts of a plant may depend on the amount present in
the soil and the processes involved in transporting these metals from the root
to the stem and fruits are controlled by the plant. For example Crump et al,
(1980) studied seasonal variations in the lead levels of a pasture grass growing
near a motorway, and found that there was a large reduction in the
concentration of lead in the grass during spring. This was thought to be due to
the rapid spring growth of the grass causing dilution.
1.1.0 DESCRIPTION OF THE SPECIES
Lettuce, okra and pepper belong to the class of leafy vegetables. They
can be described as plants, which provide a source of food often low in calories
and dry matter contents. They are consumed in addition to a starchy basic food
in order to make it more palatable. Vegetables add protective nutrients
especially vitamins and minerals to the diet. They also make several
contributions to the tropical diets, which include:
20
(a) They improve digestion.
(b) They sometimes have a curative action (Gruben and Denton, 2004).
1.1.1 ORIGIN OF PEPPER (Capsicum annuum)
The genus capsicum originated in central and south America. The
approximately 25 wild species all occur in this area. Mexico was probably the
centre of origin of the sweet pepper (Capsicum annuum).
The aromatic hot pepper was probably introduced into West African
during a later period than the chilli and bird pepper, and Africa slaves brought it
back from West Africa to the Caribbean and West Indies.
1.1.2 GROWTH, DEVELOPMENT AND ECOLOGY
Seeds germinate 6-21 days after sowing. Continuous flowering starts 60-
90 days after sowing. Flowers open three hours after sun rise and remain open
for 1-3 days. Optimal temperatures for growth and production are between 18°C
and 30°C. Seeds germinate best at 25-30°C.
Capsicum grows on almost all soil types but is most suited to well
drained sandy or loamy soils, rich in lime, with a pH of 5.5 – 6.8 and a high
water retention capacity.
Fruits begin to mature 4-5 weeks after flowering, and can be picked
every 5-7 days. The peak harvest period is 4-7 months after sowing. In the
absence of frost and diseases growth continues and plants may be become
perennial.
21
1.1.3 USES OF CAPSICUM
1. Capsicum fruits are consumed in fresh dried or processed form. Nonpungent
fruits, usually called sweet pepper, are eaten raw in salads, but
more commonly cooked, fried or processed together with other foods.
2. The red pigment extracted from ripe fruits is used as a natural colouring
agent for food and cosmetics.
3. It is widely used in local medicine. Pungent pepper cause strong
salivation, aid digestion and are laxative. Capsacin, the active
ingredient, stimulates the mucous membrane of the mouth, stomach and
bowels causing strong peristalsis.
4. It is said that regular consumption is beneficial for vascular conditions
and against haemorrrhoids, varicose veins, anorexia and liver congestion.
5. The leaves are used as a dressing for wounds and sores, and the leaf sap is
squeezed into the eyes against headache (Ghana, Congo). Gruben and
Tahir (2004). The leaves are prepared as a portion to treat cough and
heart pain.
6. In Guinea a mixture including red pepper powder is used as a traditional
insecticide to control kola weevil.
7. In recent years hot pepper is increasingly used in aerosol sprays
replacing tear gas for crowd dispersal, police officials.
22
1.1.4 ORIGIN OF OKRA (Abelmoschus esculentus)
Origin and distribution: The genus Abelmoschus originated in southeast
Asia. However, the cultigens are of uncertain origin. It is widely spread in
tropical, subtropical and warm temperate regions, but is particularly popular in
West Africa, India, Philippines e.t.c.
1.1.5 GROWTH DEVELOPMENT AND ECOLOGY OF SPECIES
Seeds germinate 5-10 days after sowing. Continuous flowering starts
within 45-80 days. Abelmoschus esculentus needs temperatures above 20°C for
normal growth and development. Germination percentage and speed of
emergence are optimal at 30-35°C.
Common okra tolerates a wide variety of soils but prefers well drained
sandy loams, with pH 6-7 and a high content of organic matter. For vegetable
use the fruits are picked about one week after anthesis. The regular removal of
young fruits permits sustained vegetative growth and flowering, prolonging the
productive period. In a seed crop, it takes about one month from anthesis to
fruit maturity.
Uses of Abelmuschus esculentus
1. Young immature fruits are important vegetable, consumed cooked or
fried. In West Africa they are usually boiled in water to make slimy
soaps and sauces
(2) Okra mucilage is suitable for medicinal and industrial applications. It
23
has been used as a plasma replacement or blood volume expander.
(3) Okra mucilage has been added as a size to glaze paper and is used in
confectionery.
(4) The bark fibre has been locally used for fish lines and game traps. It is
suitable for spinning into rope and for paper and cardboard manufacture.
(5) Roasted okra seeds are used in some areas as a substitute for coffee.
(6) The leaves are sometimes used as cattle feed.
1.1.6 ORIGIN OP LETTUCE (Lactuca sativa)
The origin of lettuce is in Turkey or the Middle East. Lettuce was known
as a vegetable in the Mediterranean as early as 450 BC. At present lettuce is the
world’s most important salad crop. Lettuce is important in Africa as an exotic.
1.1.7 GROWTH, DEVELOPMENT AND ECOLOGY OF SPECIES
(LETTUCE)
The seeds germinate within l-4days, at temperatures from 15-25°C.
Growth of young lettuce plants is exponential, slow in the beginning and very
vast in the last weeks before the harvest stage. The head is fully formed and
ready for harvesting about two months after sowing. Plants start bolting within
2-3 months old. Lettuce grows best at moderate day temperature of 15-20°C.
Lettuce is often grown on neutral sandy-loamy soils with pH 6.5-7.2. It does
not tolerate acid soils (pH <5.5). In temperate countries, lettuce is partially
grown in green houses.
24
1.1. 8 USES
Lettuce is grown for its leaves, which are usually eaten raw as a salad
with a dressing of oil vinegar. Occasionally lettuce is used as a cooked
vegetable, especially in low land areas. In China, a form of lettuce with a
thickened stem is eaten as a cooked vegetable.
1.2 STATEMENT OF THE PROBLEM
The trace metals under investigation have been generally adjudged to be toxic
to human and animals if taken in high concentrations. Vegetables take up and
accumulate these metals in different concentrations depending on the
concentration of the metals in the soil. These plants also accumulate these
metals to a different extent in the roots, stem, leaf and fruits.
1.3 AIM AND OBJECTIVES OF THE STUDY
This study was conducted to:
1. Determine the uptake of lead, nickel, cadmium, chromium and arsenic by
lettuce, okra and pepper at different concentrations in the soil.
2. To determine the distribution/accumulation of these metals in the different
parts of the plants.
25
1.4 JUSTIFICATION FOR THE STUDY
The uptake of some of the metals lead, nickel, cadmium, chromium and arsenic in
various concentrations by these vegetable plants is a source of concern, because high
concentration of these metals in these vegetables plants could affect human beings, who
depend on it as their source of essential minerals, vitamins and dietary fibre.
Do you need help? Talk to us right now: (+234) 08060082010, 08107932631 (Call/WhatsApp). Email: [email protected].
IF YOU CAN'T FIND YOUR TOPIC, CLICK HERE TO HIRE A WRITER»
