Heavy metal contamination in Celosia argentea from Four Different Locations.

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Heavy metal contamination in Celosia argentea from
Four Different Locations
BY
OKEBUNMI, Oladipupo Ayodeji
130521019
A PROJECT SUBMITTED TO THE DEPARTMENT OF
BOTANY, FACULTY OF SCIENCE, IN PARTIAL
FULFILMENT OF THE REQUIREMENTS FOR THE AWARD
OF THE DEGREE OF BACHELOR OF SCIENCE (B.SC.
HONS.) IN BOTANY OF THE LAGOS STATE UNIVERSITY,
OJO. LAGOS, NIGERIA.
DECEMBER, 2017

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CERTIFICATION
This is certify that this research work was carried out by OKEBUNMI,
Oladipupo Ayodeji with matriculation number 130521019 in the Department of
Botany, Lagos State University, Ojo, under my supervision has been approved as
a document of reference by the Department.
…………………………….. ……………………………..
Dr. (Mrs.) S. O. Oluwole DATE
Supervisor
…………………………….. ……………………………..
Dr. (Mrs.) S. O. Oluwole DATE
Ag. Head of Department
…………………………….. ……………………………..
Prof. A. E. Ayodele DATE
External Examiner

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DEDICATION
This work is dedicated to my family; my parents, Mr. & Mrs. B.M. Okebunmi
and my siblings, Odunayo & Oyindamola Okebunmi.

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ACKNOWLEDGEMENTS
This work would not have possible without the guidance and the help of several
individuals who in one way or another contributed and extended their priceless
assistance in the preparation and completion of this study.
I would like to express my sincere gratitude to my supervisor, Dr. (Mrs.) S. O.
Oluwole for her inestimable guidance and assistance during the course of this
study.
I would also like to express gratitude to the members of the Staff of the
Department of Botany, Lagos State University, Ojo, for all of the knowledge they
have imparted to me.
Lastly, many thanks to my friends and course mates; Kelvin, Michael, Razak,
Tobi for all of their invaluable support and assistance during the course of this
work.

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TABLE OF CONTENTS
Title page i
Certification ii
Dedication iii
Acknowledgements iv
Table of contents v
List of Tables vii
List of Figures viii
List of Plates ix
Abstract x
CHAPTER ONE: INTRODUCTION
1.0 Introduction 1
1.1 Literature Review 6
1.2 Cultivation 8
1.3 Harvest and Storage 9
1.4 Uses 10
1.5 Health Benefits 11
1.6 Pests & Diseases 11
CHAPTER TWO: MATERIALS AND METHOD
2.1 Methods 13
2.1.1 Sample Treatment 15
2.1.2 Sample Digestion 15
2.1.3 Preparation of AAS Stock Standard 15
2.1.4 Serial Dilution of Stock Standard 15
CHAPTER THREE: RESULTS
3.1Results 17

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CHAPTER FOUR: DISCUSSION, CONCLUSION &
RECOMMENDATION
Discussion 22
Conclusion & Recommendation 26
REFERENCES 27

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LIST OF TABLES
Table Page
1. Analysis of heavy metal contamination of Celosia argentea from 18
control and study areas (mg/kg)

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LIST OF FIGURES
FIGURE PAGE
Figure 1 Concentration of heavy metals of plant samples from 19
four locations.
Figure 2 Concentration of heavy metals in plant samples from 20
control and roadside areas.
Figure 3 Concentration of heavy metals in plant samples from 21
control and market areas.

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LIST OF PLATES
PLATE PAGE
1 A growing Celosia argentea 7
2 The germinating Celosia argentea after 2 weeks 14

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ABSTRACT
Leafy vegetables are important sources of many nutrients, including potassium,
dietary fibre, folic acid, Vitamin A, Vitamin E, and Vitamin C. Consumption of
leafy vegetables in urban areas contaminated with heavy metals is a major source
of health problems for humans. This study was conducted to analyse the heavy
metal levels in Celosia argentea grown in selected ever busy roads near Lagos
State University and some selected markets using Atomic Absorption
Spectrometers (AAS). Dry ashing method was used to destroy the organic matter
to determine the content of the heavy metals. The results showed that the mean
concentration of heavy metals in mg/kg dry weight were in the range of: Fe (0.607
- 1.657), Cu (0.161 - 0.229), Zn (0.056 - 0.4101), Mn (0.092 - 1.1924), Cr (0.297
- 0.7790), Co (0.0921 - 0.3101), Hg (ND - 0.0013) and Pb (0.034 - 0.1642.
Cadmium and Nickel were not detected in any of the samples. The levels of heavy
metals determined in the analysed Celosia argentea samples were found to be
below the permissible limits set by FAO/WHO; hence they are safe for human
consumption. However, farming along roadsides should be discouraged. So also
should the excessive use of insecticides and pesticides.

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CHAPTER ONE
INTRODUCTION AND LITERATURE REVIEW
1.0 INTRODUCTION
Metals occur naturally in the earth's crust and their contents in the environment can vary
between different regions resulting in spatial variations of background concentrations.
The distribution of metals in the environment is governed by the properties of the metal
and influences of environmental factors (Khlifi and Hamza-Chaffai, 2010). Of the 92
naturally occurring elements, approximately 30 metals and metalloids are potentially
toxic to humans.
Heavy metals is the generic term for metallic elements having an atomic Weight higher
than 40.04 (the atomic mass of Calcium, Ca) (Ming-Ho, 2005). Heavy metals can be
defined in several ways. One possible definition is the following: Heavy metals form
positive ions in solution and they have a density five times greater than that of water
(Hawkes, 1997).
Heavy metals are natural components of the earth crust and as a result they are found
naturally in soils and rocks with a subsequent range of natural concentrations in soils,
sediments, waters and organisms (Hutton and Synmon, 1986).
Heavy metals are among the contaminants in the environment. Besides the natural
activities, almost all human activities also have potential contribution to produce heavy
metals as side effects. Migration o
f these contaminants into non -contaminated areas as dust or leachates through the soil
and spreading of heavy metals containing sewage sludge are a few examples of events
contributing towards contamination of the ecosystems (Gaur and Adholeya, 2004).
Heavy metals are conventionally defined as elements with metallic properties and an
atomic number >20. The most common heavy metal contaminants are Cadmium (Cd),
Chromium (Cr), Copper (Cu), Mercury (Hg), Lead (Pb), and Zinc (Zn). Metals are
natural components in soil (Lasat, 2000). Some of these metals are micronutrients
necessary for plant growth, such as Zinc (Zn), Copper (Cu), Manganese (Mn), Nickel

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(Ni), and Cobalt (Co), while others have unknown biological function, such as;
Cadmium (Cd), Lead (Pb), and Mercury (Hg) (Gaur and Adholeya, 2004).
A ubiquitous characteristics of heavy metals in general regardless of whether they are
biologically essential or not is that they may exert toxic effects on plants in low
concentrations compared to macronutrients and these metals are considered to be
cytotoxic and mutagenic, although, a few of them are essential for metabolic processes
(Kabata – Pendias and Pendias, 2001; Fodor, 2002).
From a historical perspective, some heavy metals such as Gold (Au), Silver (Ag),
Copper (Cu), Tin (Sn) and Lead (Pb) have been used by mankind for thousands of years
(e.g., Gold (Au) around 8,000 years, Copper (Cu) >6,000 years). The places where these
metals were mined and smelted or where artefacts were made from them will have been
contaminated by these metals. Other geochemically associated heavy metal(loid)s such
as Arsenic (As) and Zinc (Zn), which were present in some of the ore deposits, but not
intentionally exploited, will also have contaminated the local environment. Analyses of
carbon and pollen-dated layers in peat cores from ombrotrophic bogs in Europe have
revealed that atmospheric pollution of Cu and Pb from mining and smelting has
occurred over a period of more than 4,000 years (De Vleeschouwer et al., 2009). Peaks
of contamination occurred at historically important times such as the Bronze Age, the
Roman Empire, the Industrial Revolution and the ‘modern’ period with its diverse
sources and greatly increased pollution loads. Apart from anthropogenic sources, soils
in areas underlain by rocks with anomalously high contents of heavy metal (loid) s will
also have become enriched through natural geomorphological and pedogenic processes
over an even longer timescale.
Most heavy metal soils worldwide have been exploited by human activities from early
times. However, due to the insufficient technologies of medieval time and earlier
periods, the remnants (heavy metal heaps) are still rich in heavy metals and carry a
typical metallophyte vegetation. The concentration of heavy metals can be particularly
high around smelters. When close to rivers, the heavy metals are gradually washed off
leading to the diminution of the heavy metal vegetation with special concern about the
risk of losing endangered plants (Becker and Dierschke, 2008; Lucassen et al., 2010).

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Heavy metals are natural components of the earth crust and as a result they are found
naturally in soils and rocks with a subsequent range of natural concentrations in soils,
sediments, waters and organisms (Hutton and Synmon, 1986). Human activities through
industrial, agricultural, traffic domestic, mining and other anthropogenic processes have
contributed to elevated and toxic levels of these metals when compared to those
contributed from geogenic or lithological processes (Pam et al., 2013). Industrialization
and urbanization have been identifies as the two major causes of deterioration of air
quality. It may also be attributed to industrial activities besides the density of vehicular
traffic emissions especially diesel engines. On the other hand, rural areas receive
minimal amount of heavy metals (Wang and Huang, 2003; Fang et al., 2005).
Metal pollution has harmful effect on biological systems and does not undergo
biodegradation. Toxic heavy metals such as; Lead (Pb), Cobalt (Co), Cadmium (Cd)
can be differentiated from other pollutants, since they cannot be biodegraded but can be
accumulated in living organisms, thus causing various diseases and disorders even in
relatively lower concentrations (Pehlivan et al., 2009). Heavy metals, with soil
residence times of thousands of years, pose numerous health dangers to higher
organisms. They are also known to have effect on plant growth, ground cover and have
a negative impact on soil micro flora (Roy et al., 2005.). It is well known that heavy
metals cannot be chemically degraded and need to be physically removed or be
transformed into nontoxic compounds (Gaur and Adholeya, 2004).
Metal toxicity reduces vigour and growth of plants, causes death to plants in extreme
cases, interferes with photosynthesis, respiration, water relation, reproduction and it
causes changes in certain organelles, disruption of membrane structure and functions of
different plant species, (Wilkins, 1978; Prasad; 1997; Panda, 2007). Also, exposure of
man to such metals may cause bone and blood disorders, kidney damage and
neurological damage (NIEHS, 2014).

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Recently, (Sharma et al., 2008) have reported that atmospheric deposition can
significantly elevate the levels of heavy metals contamination in vegetables commonly
sold in the markets. The prolonged consumption of unsafe concentrations of heavy
metals through foodstuffs may lead to the chronic accumulation of heavy metals in the
kidney and liver of humans causing disruption of numerous biochemical processes,
leading to cardiovascular, nervous, kidney and bone diseases (WHO, 1992; Jarup,
2003). Some heavy metals such as Cu, Zn, Mn, Co and Mo act as micronutrients for the
growth of animals and human beings when present in trace quantities, whereas others
such as Cd, As, and Cr act as carcinogens (Feig et al., 1994; Trichopoulos, 1997). The
contamination of vegetables with heavy metals due to soil and atmospheric
contamination poses a threat to its quality and safety. Dietary intake of heavy metals
also poses risk to animals and human health. Heavy metals such as Cd and Pb have been
shown to have carcinogenic effects (Trichopoulos, 1997). High concentrations of heavy
metals (Cu, Cd and Pb) in fruits and vegetables were related to high prevalence of upper
gastrointestinal cancer (Turkdogan et al., 2002).
Fodor (2002), suggested an interesting stepwise model for the action of heavy metals in
plants. Initially, there are interactions with other ionic components present at the locus
of entry into the plant rhizosphere that subsequently have consequences for the
metabolism. This is followed by an impact on the formation of reactive oxygen species
(ROS) in the cell wall and an influence on the plasma lemma membrane system (stage
1). At stage 2, the metal ion reacts with all possible interaction partners within the
cytoplasm, including proteins, other macromolecules and metabolites. Stage 3 is mainly
related to the factors that influence homeostatic events, including water uptake,
transport and transpiration. At this stage, symptoms start to develop, and they become
visible at stage 4 according to Fodor’s model. As an example, the chlorophyll and,
usually to a smaller degree, carotenoid contents decrease, which have obvious
consequences for photosynthesis and plant growth (Barcelo and Poschenrieder, 2004).
The death of the plant cell occurs at stage 5. This model has the advantage that visible
effects are linked to metabolic events that are influenced by the metal ion of interest.

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Sharma and Agrawal (2005) described the general effects of heavy metals on plant
physiological processes. Because it can be easily measured, plant growth is commonly
used as a general parameter to study the influence of stressors, with growth rate
inhibition often being the most obvious plant reaction (Fodor 2002). This is especially
true of the root system, which is the first plant system to come into direct contact with
toxic ions. Leaf chlorosis, disturbed water balance and reduced stomatal opening
arecharacteristic effects of toxic Nickel (Ni) concentrations (Clemens 2006), but they
are also caused by many heavy metals (as part of heavy metal toxicity syndrome) and
even occur more generally as a stress response.
Aim and Objectives
The main aim of this study was to;
Investigate the heavy metal contamination in Celosia argentea.
The objectives include;
1. To cultivate Celosia argentea, using seeds obtained from National Horticultural
Research Institute and Training (NIHORT).
2. To collect mature samples of Celosia argentea from different selected markets in
Lagos.
3. To conduct heavy metal contamination analysis on the cultivated and collected
samples.
4. To determine the various levels of contamination in the different samples.

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1.1 LITERATURE REVIEW
Celosia argentea
Celosia argentea L, commonly known as plumed cockscomb, or the silver cock's comb
is an herbaceous plant of tropical origin and it is known for its very bright colours. In
India and China, it is known as a troublesome weed (Grant, 1954).
Celosia argentea is a leafy vegetable commonly found in traditional intercropping
system of the tropics (Olufolaji and Ayodele, 1988; Rehm and Espig, 1991) and it is
popular in South Western Nigeria (Schippers, 2000). The leaves and young shoots
which are rich in protein, calcium, phosphorus and iron are used in soup and stews. It
thrives in well-drained soil with a pH of 6.0 to 6.4 (Gill and Burke., 1999). Yields of
the crop is low on Nigerian farmers’ fields (16-28 t ha-1
) (Tindall, 1984; Schippers,
2000), unlike higher yield of up to 59 t ha-1
obtainable under research conditions
(Olufolaji and Ayodele, 1988). Chiefs among the factors that result in the crop low yield
include poor soil fertility. Fertilization practices and increased population undoubtedly
increase yields of crops.

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Plate 1: A Growing Celosia argentea

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1.2 Cultivation
Celosia argentea is grown on raised beds, ridges or flat beds. It may be seeded directly
into the soil at a depth of 0.75 cm (0.25 in) or started in a seedbed. Seedbeds should be
well-manured and kept moist. Germination can be expected at 5-7 days. Seedlings are
thinned to 15-30 cm (6-12 in) apart, or transplant them into the field when 10-15 cm (4-
6 in) tall, at 2-3 weeks, using the same spacing. For an once-over harvest (uprooting the
whole plant), seed may be mixed with sand or loose soil at a ratio of 1:20 and broadcast
onto the prepared soil. Mixing with sand helps to obtain a more even distribution.
The seeding rate is 6-9 g per 10 m2
whether broadcast or seeded directly into rows. With
a fertile soil and sustained harvest, wider plant spacing is recommended. Celosia
argentea germinates very readily; so readily in fact, that when a mature seed-bearing
plant is harvested and hauled to the compost pile, seedlings often emerge along the path
taken.
For a sustained harvest and higher yields via successive pruning, it is better to transplant
than direct seed. Transplanting also requires less seed, gives more uniformity of stand
and better vigour. Because it prefers rich, moist soil, flat beds are often preferred over
raised beds and ridges. The best production has been obtained from flat beds that have
been manured and well-worked prior to transplanting.
Irrigation is optional during the rainy season. During the dry season, depending on the
severity of heat and evapotranspiration, two irrigations per week are recommended.
Celosia argentea tolerates dry soil, but doesn’t like to get its feet wet.
Celosia argentea responds well to fertilizer application. As a rule of the thumb, for a –
once - over harvest, a complete NPK fertilizer (such as 10-10-10 or 15-15-15) at
400kg/ha (40kg/1000 m2
) in a single application (normally at soil preparation) is
recommended. If the harvest will be by successive cuttings, two applications of
300kg/ha each are recommended - one as “plow-down”; the other as a side dressing.
Organic manures may substitute for, or augment inorganic fertilizers at a rate of 24-40
T/ha.

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Such manures, (including compost and green manure crops) will not only increase
growth, but will also help keep nematodes in check. For a sustained harvest, after
rationing the crop, an additional NPK fertilizer should again be applied at rates of 400
to 600 kg/ha around the plants or between rows.
Getting a good, properly spaced stand can be difficult and weed competition may be
serious for a while because the C. argentea seeds and resulting seedlings are so small.
A rich organic soil is the best for growing C. argentea, although as a roadside weed it
grows in poor acidic laterite soils without organic matter. It tolerates full sun but will
produce best under partial shade. This makes C. argentea ideal for kitchen gardens
partially shaded by trees or buildings. C. argentea is killed by standing water or freezing
temperatures, and although temperatures below 20o
C (68° F) will severely restrict
growth, it withstands high temperatures well. Optimal daytime temperatures range
between 30 and 35o
C (86-95° F) with optimal night-time temperatures between 23 and
28o
C (73-82° F). C. argentea has also produced well at altitudes as high as 1700m
(5400 ft.).
Celosia argentea and other members of the amaranth family tend to reseed themselves
abundantly leading to potential weed problems. In places where few plants will grow
without special care, that might be an advantage. However, caution should be taken that
it does not become weedy.
1.3 Harvest and Storage
Celosia argentea is harvested either by uprooting or by repeated pruning of the stem
which encourages production of side shoots for further cuttings. Growers at times
combine the two methods, first uprooting as a thinning operation to encourage vigorous
growth among the remaining plants, which are then harvested by repeated cutting.
Depending on soil fertility and moisture, the crop is ready for uprooting 4–5 weeks after
direct seeding or about 4 weeks after transplanting. The first cutting is carried out at a
height of 10–15 cm leaving a sufficient number of axillary buds for the production of
lateral shoots. Subsequent cuttings are carried out at 2-weekly intervals, allowing 4–5
harvests before the start of flowering. Flowering is delayed by regular cutting.

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Traditional cultivars flower earlier than improved ones and are therefore not suitable
for harvesting by repeated cutting.
Harvested plants are bundled and tied after washing of soil from the roots. They are
then sprinkled with water to keep them fresh for marketing. If harvested late in the
evening, the plants are spread on a roof overnight and kept fresh by the night dew. In
the market, the plants are tied into small-sized bundles of 0.5–1.0 kg for sale. They are
kept covered by jute cloth and regularly watered. Shelf life of uprooted plants is
extended by 2–3 days by keeping the roots in a basin with water
1.4 Uses
Celosia argentea is primarily used as a leafy vegetable. The leaves and tender stems are
cooked into soups, sauces or stews with various ingredients including other vegetables
such as onions, hot pepper and tomato, and with meat or fish and palm oil. C. argentea
leaves are tender and break down easily when cooked only briefly. The soup is
consumed with the staple food of maize, rice, cassava or yam. The young inflorescences
are also eaten as a potherb.
In Kenya, the Masai use the liquid extract from the leaves and flowers as a body wash
for convalescents. The whole plant is used as an antidote for snakebites and the roots to
treat colic, gonorrhoea and eczema. In Ethiopia and DR Congo the seeds are used as
medicine for diarrhoea, and in Ethiopia the flowers are used to treat dysentery and
muscle troubles. In China, the leaves are used as medicine in the treatment of infected
sores, wounds and skin eruptions, and in China and Japan seed extracts have
traditionally been used as a therapeutic drug for eye and hepatic diseases. In India, the
leaves mixed with honey are applied to inflated areas or abscesses, and the seeds are
widely used for the treatment of diabetes mellitus. In South-East Asia, the flowers are
used as medicine for dysentery, haemoptysis and menstruation problems. In DR Congo
the plant is associated with occult and witchcraft beliefs. Celosia argentea can also be
used as a livestock feed. Forms with fasciated, yellow to red inflorescences are widely
grown as a bedding plant in gardens and also used as cut flowers. These are also planted
in Africa.

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1.5 Health Benefits
The leaves of Celosia argentea are high in protein, vitamins A and C, and are good
sources of calcium and iron. The flavour is pleasant, spinach-like and mild, with no
trace of the bitterness sometimes found in amaranth. Young shoots and older leaves are
cooked by boiling for about five minutes to soften the tissue and remove oxalic acid and
nitrates, potentially toxic anti-nutrients. The water may also be discoloured by red and
yellow plant pigments (anthocyanins, betalains, betacyanins and betaxanthins). These
are harmless, but should be discarded because of the dissolved oxalates and nitrates.
The leaves themselves will not discolour during the cooking process. In fact, they
become an attractive green colour looking much like cooked spinach. Lengthy cooking
will reduce the vitamin content.
The nutrient content in C. argentea varies between cultivated varieties, and apparently
with time of harvest. It has also been noted that green-leaved varieties generally are
more palatable and have higher protein and ascorbic acid (vitamin C) content than red
varieties. (Omueti, 1980).
Celosia argentea is best eaten as a vegetable before it begins flowering. Most sources
recommend harvesting 5-7 weeks after sowing for optimal nutritional value. The
highest total marketable and edible yields and total crude protein yield, however, occurs
at 15 weeks after sowing. After flowering, the new leaves are too small and unappealing
to be worth eating. (Schippers, 2000).
1.6 Pests & Diseases
Although relatively pest-free in temperate regions, C. argentea sustains damage from a
number of diseases and pests in the tropics. Spider mites and nematodes tend to be the
biggest pest problems. Reported in Nigeria are the variegated locust and a beetle, Baris
planetes, which attack and feed on immature seed capsules causing seed loss. Larvae
(caterpillars) of Hymenia recurvalis and Psara bipunctalis feed on the foliage, and
grasshoppers and aphids can cause minor damage. Nut grass (Cyperus rotundus) is a
serious weed problem.

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Celosia argentea is quite susceptible to root-knot nematode (Meloidogyne spp.)
infection causing the formation of galls on the roots, stunted growth, small brown-
coloured leaves and reductions in yield of up to 40%. If nematodes are a problem, plant
in soil amended with lots of organic matter, topped off as well with organic mulch. In
some studies, the green varieties have been observed to be more susceptible to nematode
damage than the red varieties (Schippers, 2000).
White rust and crown blight are considered the most serious fungal diseases affecting
C. argentea. During the rainy season and when there is high humidity these and several
other fungal diseases can cause problems in C. argentea, which in turn cause poor leaf
quality. Appropriately spaced plant stands, clean fields (free of diseased and dead
plants) and resistant varieties can help to significantly reduce fungal disease damage to
your crop.
White rust (Albugo blitii) causes white pustules on the undersides of the leaves with
chlorotic lesions on top, and seriously damages Nigerian-grown plants. It is
recommended to rogue out and destroy infected plants to reduce the incidence of
infection in subsequent crops. Crown blight (Choanephora cucurbitarum) is a wet rot
fungus that can become a problem in dense plots with insufficient aeration. This is the
main disease of amaranth during rainy season, and can sometimes affect C. argentea in
the same way.
A virus causing mosaic and leaf-curl has been isolated from vegetable farms producing
C. argentea near Lagos and Tejuoso, Nigeria. It is transmitted in a non-persistent
manner by two aphid species (Aphis spiraecola and Toxoptera citricida). On the basis
of the available information, this virus is different from other viruses infecting
vegetables in Nigeria. The name Celosia mosaic virus (CIMV) has been suggested for
this virus (Owolabi, 1998).
Other diseases include Rhizoctonia solani, Pithium aphanidermatum and
Thatatephorus cucumeris, which cause damping-off of seedlings, and collar rot
(Phytophthora cryptoge) which causes similar symptoms on older plants as well.
Cercospora leaf spot (Cercospora Celosiae) causes red-rimmed grey spots on the
leaves. Alternaria leaf spot (Alternaria spp.) and charcoal rot (Macrophomina
phaseolina and Curvularia spp.) cause dark spots on the leaves.

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CHAPTER TWO
MATERIALS AND METHODS
2.1 Methods
Samples of mature Celosia argentea were purchased from four (4) different market sites
viz. Iyana – Ipaja market, Ikotun market, Oko – efo, Alakija market. The four markets
were selected randomly giving priority to the urban market sites and roadside market
sites.
The samples collected from the Lagos State University, Ojo Greenhouse served as
control experiment. The seeds were collected from National Horticultural Research
Institute, Idi – Ishin, Ibadan and the seed were sown in the greenhouse at the LASU
Botanical Garden in order to eliminate all forms of contamination. In preparation of the
control experiment, several steps were made. The steps made include; procurement of
needed materials like buckets, manure, shovels. Holes were then penetrated in the
buckets. This was done to enhance aeration in the soil to be used.
Before preparation of the soil for planting, the soil was sieved thoroughly to remove
contaminants or impurities. Four (4) buckets containing humus soil were then prepared.
Then, manure was added to the soil in the ratio 1:4. The soil was then left for about a
week to enable the manure incorporate properly in the soil. On 15th
June, the seeds were
sown. The seeds were sown randomly on the soil considering that they were very tiny.
About 5-7 days later, germination had begun.
After about 5-6 weeks of continuous watering and weeding, the plant had already
undergone maturation and the samples were ready for conduction of heavy metals
analysis. The mature plants were then uprooted and place in sterile zip – lock bags
before the levels of heavy metals concentration are determined.

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Plate 2: The germinating Celosia argentea after 2 weeks

25. 25
2.1.1 Sample Treatment
The samples were placed in a clean acid – washed porcelain crucibles and oven – dried
at 105o
C for 24 hours in a drying oven. The dried samples were then grounded into a
fine powder form using acid washed mortar and pestle and passed through a 2.0 mm
sieve. The powdered samples were kept in polythene packets for further analysis.
2.1.2 Sample Digestion
5g of the grounded plant sample was weighed into a quartz beaker and 10ml of HNO3
was added and gently heated on a hot plate. Heating was continued until the brown
fumes turn to white. The beaker was then brought down to cool to room temperature.
The mixture was then diluted with 20ml of deionized water and filtered into a standard
25ml volumetric flask and made up to mark in readiness for Atomic Absorption
Spectrophotometry (AAS) using Whatmann filter papers.
2.1.3 Preparation of Atomic Absorption Spectrophotometry (AAS) Stock
Standard
The stock standard was prepared by weighing 1.299g of PbNO3 salt and dissolving it in
1 litre of 5% HNO3. The salt was initially dissolved in a beaker after which it was diluted
into a 100ml volumetric flask with 5% HNO3 and made up to mark.
2.1.4 Serial Dilution of Stock Standard
The stock standard was serially diluted to concentrations of 1ppm, 2ppm, 3ppm, 4ppm,
5ppm. These different calibration levels were used to generate a suitable curve which
was used to calibrate the instrument using the serial dilution formula;
C1V1 = C2V2

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Where
C1 represents the initial concentration
C2 represents the final concentration
V1 represents the initial volume
V2 represents the final volume
After the serial dilution of the stock standard, the different calibrants were fed into the
Atomic Absorption Spectrometer as standard samples. These were used by the AAS to
generate a suitable calibration curve,
Other standards were prepared in the same manner using their appropriate reagents.

27. 27
CHAPTER THREE
RESULTS
The results of the analysis of the concentration of heavy metals present in the soil and
study area samples is presented in Table 1.
Figure 1 shows the concentration of Fe, Cu, Zn, Mn, Cr, Co, Hg, and Pb (in mg/kg)
respectively in plant samples collected from control and study areas.
Figure 2 shows the concentration of Fe, Cu, Zn, Mn, Cr, Co, Hg, and Pb (in mg/kg)
respectively of Celosia argentea samples obtained from roadsides and the market areas.
The level of concentrations in the market and roadside samples are seen to be higher
than the control samples.
Table 1 shows the results of the chemical analysis of Fe, Cu, Zn, Mn, Cr, Co, Hg, Pb
(in mg/kg) in the various samples of Celosia argentea which comprises samples from
Iyana – Ipaja, Ikotun and Alakija markets, Oko – efo and the control samples planted at
the LASU Botanical Garden.

28. 28
TABLE 1: ANALYSIS OF THE MEAN±SD OF THE HEAVY METALS CONCENTRATION IN PLANT SAMPLES OF
CELOSIA ARGENTEA IN mg/kg
Note: ND = Not Detected.
Location Fe (mg/kg) Cu (mg/kg) Zn (mg/kg) Mn (mg/kg) Cr (mg/kg) Co (mg/kg) Hg (mg/kg) Pb (mg/kg)
Control 0.607±0.006 0.161±0.00220 0.056±0.0005 0.092±0.0007 0.297±0.001 0.0921±0.0004 ND 0.034±0.0003
S1: Oko – Efo 1.657±0.023 0.195±0.005 0.365±0.005 0.349±0.002 0.679±0.001 0.311±0.013 0.0013±0.0006 0.232±0.019
S2: Iyana – Ipaja 0.790±0.007 0.218±0.009 0.1891±0.001 0.1614±0.0006 0.7790±0.005 0.201±0.0005 ND 0.199±0.001
S3: Alakija 0.665±0.006 0.229±0.005 0.4101±0.008 1.192±0.0007 0.385±0.007 0.156±0.0004 ND 0.149±0.0004
S4: Ikotun 0.857±0.002 0.191±0.001 0.261±0.005 0.142±0.0006 0.669±0.019 0.175±0.001 ND 0.164±0.002
FAO/WHO Limit 425.5 73.3 99.4 500 2.3 50 0.5 2.0

29. 29
Figure 1: Total Fe, Cu, Zn, Mn, Cr, Co, Hg, and Pb concentration in Celosia argentea
collected from four locations.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Fe Cu Zn Mn Cr Co Hg Pb
Concentration(mg/kg)
Control
Oko Efo
Iyana - Iba
Alakija
Ikotun

30. 30
Figure 2: Total Fe, Cu, Zn, Mn, Cr, Co, Hg, and Pb concentration in Celosia argentea
grown by the roadside.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Fe Cu Zn
Concentration(mg/kg)
Control
Oko Efo
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
Fe Cu Zn Mn Cr Co Hg Pb
Concentration(mg/kg)
Control
Oko Efo

31. 31
Figure 3: Total Fe, Cu, Zn, Mn, Cr, Co and Pb concentration in Celosia argentea
collected from markets.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Fe Cu Zn Mn Cr Co Pb
Concentration(mg/kg)
Control
Iyana - Iba
Alakija
Ikotun

32. 32
CHAPTER FOUR
DISCUSSION, CONCLUSION AND RECOMMENDATION
Discussion
Table 1 shows the concentration of these heavy metals in the plant samples of the
control and the study areas. The value are given as mean ± SD and the results are means
of three replicates. The heavy metals determined were based on plants dry weight. The
levels of Iron were found to be the highest while the levels of Lead were found to be
the lowest. Heavy metals affect the nutritive values of agricultural materials and also
have deleterious effect on human beings. National and international regulations on food
quality set the maximum permissible levels of toxic metals in human food; hence an
increasingly important aspect of food quality should be to control the concentrations of
heavy metals in food (Radwan and Salama, 2006; Sobukola et al., 2008).
Iron is an essential element in man and plays a vital role in the formation of
haemoglobin, oxygen and electron transport in human body (Kalagbor and Diri, 2014).
Iron was found to have the highest concentration in all of the samples analysed with an
average value of 0.607mg/kg in the control sample and 0.607 to 1.657mg/kg in the study
area. The FAO/WHO (2001) maximum limit for Iron concentration in food is 425.5
mg/kg. The result obtained in this study is lower than the recommended limit.
Copper is an essential micronutrient which functions as a biocatalysts, required for body
pigmentation in addition to iron, maintain a healthy central nervous system, prevents
anaemia and interrelated with the function of Zinc and Iron in the body (Akinyele and
Osibanjo, 1982). However, most plants contain the amount of copper which is
inadequate for normal growth which is usually ensured through artificial or organic
fertilizers (Itanna, 2002). In this study, the concentrations of Copper in all the tested
samples varied between 0.161mg/kg in the control and 0.1909mg/kg to 0.2299mg/kg in
the study areas. The FAO/WHO (2001) maximum limit for Copper concentration in
food is 73.3mg/kg. The result obtained in this study is lower than the recommended
limit.

33. 33
One of the most important metals for normal growth and development in human beings
is Zinc (Divrikli et al., 2006). Its deficiency may be due to inadequate dietary intake,
impaired absorption, excessive excretion or inherited defects in zinc metabolism (Colak
et al., 2005; Narin et al., 2005). Zinc deficiency due to consumption of plant foods that
have inhibitory components for Zinc absorption is of growing concern in developing
countries. Concentration of Zinc in the samples reported in this study varied between
0.0563mg/kg in the control and 0.1891mg/kg to 0.4101mg/kg in the study areas. This
may be as result of high vehicular emissions and oil leakage along these roads. Zinc is
known to be one of the most used complementary compound of hydrocarbon in fuel
and engine components in vehicles (Landsberger et al., 1999). Zinc is an essential
element in human diet as it helps in maintaining the functioning of the immune system.
Its deficiency or excess in diets may be detrimental to human health. The concentration
of Zinc in both the control and the study areas is lower than the 99.4mg/kg standard
recommended by the World Health Organization (2007).
Manganese is essential element required for various biochemical processes. The kidney
and liver are the main storage places for the manganese in the body. Manganese is
essential for the normal bone structure, reproduction and normal functioning of the
central nervous system. Its deficiency causes reproductive failure in both male and
female (Saraf and Samant, 2013). The concentration of Manganese in all tested samples
in this study vary from 0.0922mg/kg in the control and 0.1422mg/kg to 1.1924mg/kg
in the study areas. The concentration of Manganese in both the control and the study
areas is lower than the 500mg/kg standard recommended by the World Health
Organization (2001).
Chromium is an essential element required for normal sugar and fat metabolism. It is
effective to the management of diabetes and it is a cofactor with insulin. Chromium (III)
and its compounds are not considered a health hazard, while the toxicity and
carcinogenic properties of Chromium have been known for a long time (Kalagbor et al.,
2014). The concentration of Chromium in all of the tested samples range from
0.297mg/kg in the control and 0.385mg/kg to 0.779mg/kg in the study areas. These

34. 34
values are lower than the maximum permissible limit of 2.3mg/kg by FAO/WHO
(2001).
Cobalt is an integral component of the vitamin B-12 molecule. It is required in the
manufacture of red blood cells and in preventing anaemia. An excessive intake of cobalt
may cause the overproduction of red blood cells (Kalagbor et al., 2014). ). The
concentration of Chromium in all of the tested samples ranged from 0.092/Kg in the
control and 0.156mg/kg to 0.311mg/kg in the study areas. The concentration of Cobalt
in both the control and the study areas is lower than the 50mg/kg standard recommended
by the World Health Organization (2001).
Mercury is more toxic than Cadmium and Lead and causes serious health problems such
as loss of vision, hearing and mental retardation and finally death occurs. Mercury was
not detected in most of the samples analysed. However it was detected in only one
location and its concentration was averaged at 0.001mg/kg. This is considerably lower
than the 0.5mg/kg WHO recommended standard (2001).
The level of concentration of Lead ranges between 0.0334mg/kg in control and
0.164mg/kg to 0.232mg/kg in the study areas. This is considerably lower than 2.0mg/kg
WHO recommended standard (2007). The high level of concentration of Lead in the
study areas may be due to the effect of dust, oil spillage from the roads and exhausts
from vehicles. The high level of Lead in some plants may be attributed to pollutants in
irrigation water and farm soil (Qui et al., 2000). Lead is a serious cumulative body
poison which enters the body system through air, water and food. It cannot be removed
by washing the fruits or vegetables but by blanching. The toxicity effects include;
learning disabilities, behavioural problems and mental retardation in children. In
extreme cases, it may lead to seizure, coma and even death (Divrikli et al., 2000).
Nickel plays some roles in body functions including enzyme functions. In very trace
amounts it may be beneficial to activate some systems, but its toxicity at higher levels
is more enzyme prominent (Onianwa et al., 2000). The concentration of Nickel was
recorded as non-detectable in all of the samples.

35. 35
Cadmium is highly toxic non-essential heavy metal and it does not have a role in
biological process in living organisms. Thus even in low concentration, cadmium could
be harmful to living organisms (Ambedkar and Muniyan, 2012). Cadmium poisoning
in man could lead to anaemia, renal damage, bone disorder and cancer of the lungs
(Edward et al., 2013).
It was however observed that the concentration of heavy metals in roadside samples is
higher. This may be as a result of emissions from motor vehicles. The concentration in
the market samples are however found to be lower.

36. 36
Conclusion
The results obtained from this study have shown that the level of heavy metals
concentration in the study areas samples are generally of higher concentration than the
control samples. This may be attributed to pollutants which can be sourced from
emissions from vehicles, fertilizers and pesticides. The concentrations of heavy metals
determined were in sequence Fe > Mn > Cr > Zn > Co > Pb > Cu > Hg. However, the
concentration of Nickel and Cadmium were not detected in any of the samples and
Mercury was detected in only one of the samples.
Recommendation
This study emphasizes the need that regular monitoring should be conducted to detect
increasing levels of heavy metals not just in vegetables but also fruits and other edible
foods which exposes consumers to various health risks through ingestion.

37. 37
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