LEVEL OF HEAVY METALS IN YAM, CASSAVA AND COCOYAM

TUBERS IN NIGER DELTA NIGERIA – A SURVEY

BY

UDEZE ANTHOINA OGECHUKWU

FPO/IND/SLT/04/3158-02

DEPT. OF SCIENCE LABORATORY TECHNOLOGY

SCHOOL OF APPLIED SCIENCES AND TECHNOLOGY

FEDERAL POLYTECHNIC,

OKO

SEPTEMBER, 2006

LEVEL OF HEAVY METALS IN YAM, CASSAVA AND COCOYAM

TUBERS IN NIGER DELTA NIGERIA – A SURVEY

BY

UDEZE ANTHOINA OGECHUKWU

FPO/IND/SLT/04/3158-02

A PROJECT WORK PRESENTED TO THE DEPARTMENT OF

SCIENCE LABORATORY TECHNOLOGY, SCHOOL OF

APPLIED SCIENCE AND TECHNOLOGY, FEDERAL

POLYTECHNIC, OKO ANAMBRA STATE IN PARTIAL FULFILLMENT OF

THE REQUIRMENT

FOR THE AWARD

OF THE HIGHER NATIONAL DIPLOMA (HND) IN SCIENCE

LABORATORY TECHNOLOGY (CHEMISTRY OPTION)

SEPTEMBER 2006

CERTIFICATION

This is to certify that UdczeAnthoniaOgechukwu with Reg. No.

FPO/HND/SLT/04/3158-02 Presented this Project to the Department of Science

Laboratory Technology, Federal Polytechnic, Oko. Anambra State.

………………………………………

Mr Vin Okonkwo

(Supervisor)

………………………………………

Date

…………………………….

Mr Vin Okonkwo MrOkeke 3,1,

(SW80?) ' (Head of Department) EM»

I8) wig Date Date

MrOkeke 3,1, (SW80?) ' (Head of

Department) EM» I8) wig Date Date

External Exammer

Dedication

This work is dedicated to God, the delight of My heart and my immeasurable

parent Mr. and Mrs. Udeze Slyvanus.

Acknowledgement

A good academic work can never be the sole effort of an individual.

Firstly, my gratitude goes to the God, the delight of my heart, the cause of

my joy, who gratedme the enablement, grace and skill in writing this project paper.

And the way He prepared manypeople as a vessel in getting this work ready.

I expressed my gratitude to my supervisor, Mr Vin Okonkwo, who denied

himself so many things to see the completion of this work.

My sincere happiness goes to my head to department Mr. Okeke S. l for his

assistance and fornot leaving any stone unturned for the betterment of the

department Keep it up.

My special thanks goes to the project co-ordinator Mr Ezeobele, who acted

like a father to all of us.

I express my sincere gratitude to all the lecturers in the department

ofScience lab. Tech, more especially Mrs. Ogbuka, the head of chemistry unit.

Indeed, a mother, Mr. Allen Nwosu, Mr. Chidi Nzekwe, Mr.I. G Onygekwe, Mr.

M.K.O Onuabuchiwho always like to see smile on my face others are Mr. Chuke

L. U former HOD Sec. Studies Department Mr. Obiora Udeh, Mr. Daniel Ezeh,

Mrs. Makwe, Mr. and Mrs. Macdonald, John Macdonald, Mr. Nnoye C, Mr. Paul

O.

No word of gratitude is sufficient to appreciate the encouragement I have

been receiving from time to time from my caring parents Mr. and Mrs, S. Udeze

and my siblings Uche, Ifeanyi, Chioma and Emeka.

Although, it is very impossible to mention everybody’s name but cannot forget to

mention these people so dear to my heart more especially my classmates Nkiru,

Cecilia, Geraldine Ifesinachi, Onyedika, Ogheneyurumeno, Elochukwu, and

others. Others are Nnawuke Chizoba and Amaefuna Fabian, Ifeoma Nkriu Udeze.

Finally, it is my sincere prayers that God grants allthose mentioned and

those did not mention with immeasurable blessings and to crown their effort with

abundant success in different field of endeavour.

Table of Content

Title page i

Certification ii

Dedication iii

Acknowledgement iv

Table of Content v

List of Tables vi

List of Plates vii

List of Appendix viii

Abstract x

Chapter one

Introduction 1

Chapter two

Literature review 7

General description of cassava and its uses 7

General description of yam and its uses 12

General description of cocoyam and its uses 15

Oil pollution, sickness and death 18

Chapter three

Material and Method 22

Collection of samples 24

Sample preparation 24

Digestion of samples using dry aching method 24

Chapter four

Result 26

Chapter five

Discussion 27

Conclusion 29

Recommendation 30

References 31

List of table

Table l: different species of yam, common name, origin, tubers

number and shape 34

Table 2: The weight of the samples coco yam and cassava in gram

before drying after air drying and after grinding 35

Table 3: level of heavy metals concentration in Mg 1kg found in

Cocoyam and cassava 36

Table 4: The source of exposure, acid effect in humans, chronic

effects inhuman and treatment of the metals found in cassava,

cocoyam and yam 36

Table 5: WHO standard concentration of metal 38

List of plates

Plate 1: showing the samples used in experiment 23

List of Appendix

Result of Coco yam, yam and cassava in mg/kg

Tables used in the work

Abstract

A total of seven heavy metals, Pb, Cd, Zn, Fe, Ni, Cu, Mn, Na, were determined in cassava, yam and cocoyam using atomic absorption spectrophotometer model schimadzu AA 6701 in airacetylene flame. The samples were cut, peeled, washed, sliced very light, air dried and ground into powder. 5g of the powered samples were ashed, digested using 2ml of 36.5g/dm Hydrochloric acid, 2ml conctrioxonitrate (V) acid and distilled water, to remove all the organic matters and leave behind the trace metals. These Endings showed that some metals like Fe (16.23mg/kg in yam), 18.26mg/kg in cassava, 31.36 mg/kg in cocoyam and Zn, 19.77 mg/kg m coco yam have higher values compared with W.H.O standard. The most toxic ones, lead <0.01 mglkg and cadmium 0.02 mg/kg in the samples analyzed were insignificant.

CHAPTER ONE

INTRODUCTION

Cassava, the plant Manihotesculeta also called Manioc is one of the 10 most

important food plants and the most important starch root or tuber of the tropics. It

is originated in central or south America, possibly Brazil and was domesticated and

widely distributed well before the time of Columbus. The cassava plant is a

slightly woody, perennial shrub reaching 10ft (3m) in height. The leaves as deeply

palmately lobed. The flowers are inconspicuous and the prominent capsules are

three seeded and explosive at maturity. The roots are enlarged by deposition of

starch and constitute the principal source of food from the plant normal yields are

about (4.5kg) per plant. The leaves are also eaten (after cooking) and are

noteworthy for their high protein content. The plant is propagated from mature

stems, which are planted without special treatment. Tuberlization occurs gradually

about 10-12 months from planting to harvest. Cassava can be grown for 2 or more

years, however and this is a food that can be used at any season. Once it is

harvested, the root deteriorates within a few days.

The chief use of cassava is as to boiled vegetable. It is a source of flour

called garri in Western Africa and of toasted starch granules the familiar tapioca. It

can be processed into maconi and a rice-like food. In the form of died chips,

cassava root is an important animal feed in spite of popularity; cassava root is a

poor food. Its protein content is extremely low and its consumption as a staple food

is associated with protein deficiency disease kwashiorkor. In addition, part of the

plant contain glycosides of hydro cyanic acid substance which on decomposition

yield the poisons hydro cyanic acid (CHCN) prussic acid chronic disease including

goiter are common in regions where cassava is a staple food. (Frankin, 1997).

Several species of yams are grown in the tropics and subtropics of the edible

species, DioscoreaalataL, known as the greater yam, D.rotundataPoir, the white

yam,are the most common. D alata originated in South East Asia and the

lattertwoarenativetoAfrica.Allareherbaceousvineswhichmustbe trellised - (a light

frame made of long narrow pieces of wood that cross each other- used to support

climbing plant) for maximum yield. Yams are grown asannuals at planting

densities of 10,000 plants/ha and produce a tuber which is harvested to 12months

after planting. Tuber flesh varies from white to yellows and is from 15 to 40%

starch.Tubers have a distinct dormancy period, which can be extended with curing

and the application

of gibberellic acid. This makes yams ideal for long distance shipment and export.

Alternatively,this causes large fluctuations in availability of fresh yam since the

crop is not planted until thedormancy period which coincides with the dry season,

has ended.

Once sproutingbegins, tuber quality decreases rapidly. Thus, good quality yams are

inshort supply until the next harvest begins.

Propagules are portions of the tuber, with large propagules producing

operations aremechanized. Yams are usually baked or bailedand mashed.

(Olayemi, 2006).

TanniaCxanthosomasagittifoluim (L) Scott), also known as cocoyam,malanga or

yantia,originated in the wet valleys of NorthenEastern South American is common

only in wetter areasbut is also grown in fadamas in the north. It does best with high

humidity and copious watersupply throughout growth and good soil. It is grown

extensively in the eastern states andCameroon as a ‘compound’ crop on land

heavily manured with household refuse. It canwithstand shade. Although grown

primarily for its edible corms, the leaves are also eaten as agreen vegetable, and

used for wrapping prepared food.

There are two main types (a) Tannia (xanthosoma) the most commonly

cultivated (b) Taro (colocasia), planting. In the height of the rains, may – June.

Planted like yams on low mounds andcovered well to avoid sun damage, 20-30cm

is usual depth. On setter stand. Spacing of1-2m2 is allowed per stand spending on

the growth expected. Colocasia is usually spacedmore widely Xanthosoma.

Propagated by small corms oroff shoots up 300g in weight. Its germination

dependon the conditions ofthe “seed” sprouted setts in about 7 days, others up to

15 days. The maturity and harvest 6-8 months are required for maturation, the crop

being dug by hand in Decanter-January.(Kay-1973).

There is much confusion within this genus, with addition, tannin

isottenconfusedwithtaro. Inpartsof Africa,both are knownascocoyam and inother

places botharelistedas taro.There are onlyafewvarieties

oftanniaandmosthavewhiteflesh. Pink and yellows fleshedtypesare less common

and occasionallyclassified as X. Violaceum. Schott and X.atroviras C. Koch,

respectively. Flowering are rare and handpollinations are required for seed

production. (Thompson, (1982).

Heavy metals focuses on toxic heavy metals, cadmium, lead and

mercuryandtheseheavymetalshave causedharmtoourhealthandthe environment.

These metalsare well known pollutants that have caused severe damage in some

part of the world and morewidespread chronic effects in some populations.

Mercury for instance is pollutant that can travelvery long distances and high levels

of mercury, attributed to man-made emissions, have beenfound in fish, especially

in some parts of Northern Europe and North America making it unsafefor human

consumption. Heavy metals can cause blood disorders and affect vitalorgans such

as the liver and the kidneys (Genoga, 2003).

Pollution is the fouling of theenvironment with undesirable andnoxious

substances.Pollution therefore is an undesirable change in the physical, chemical

and biologicalcharacteristics of our air, land and water and which harmfully affect

human life as well as otherliving things. The substances that cause drastic change

in the environment are termedpollutants. Over 200,000 different organic

compounds are synthesized commercially and manyeventually find their way into

soil ecosystems, usually without incident. In some cases such aspetroleum spills,

the compounds are toxic to soil organisms, when present at

significantconcentrations and thus produce large shifts in microbial community

structure. Oil spills appearto cause moredamage fragileecosystem. Suchassoilof

tundra. Spillageofothertoxic chemicalscancausesimilarlongterm effects on

microbiology. Eventually, microorganismspresent in the soil degrade most organic

contaminants thus alleviating toxic effects. The timerequiredfor degradation

depends onthe compoundsandtheorganism involved, as in some causesorganism

originating from other sites can be usedas inoculato enhance degradation (Gerald,

1992).

Pollutioncausedbytheoilandnaturalgasindustryhas beenmind

bogglingandextensive. It has ledtoground waterpollution,whichin

turnhascausedoutbreaksof diarrheaepidemics. Birthdeformities are on the rise as

are certain soft

tissue cancers. Environmental pollution hasledtothedisplacement offarmersandtheir

families into surrounding urban centers already ill-equipped to deal withthe

economics social and health requirement of their burgeoningpopulations. Most of

the new migrams in these urban centers become trapped in cycles ofpoverty and

penury.

One of the major causes of the “rural flight” is the pollution of the soil and

land and theconcomitant reduction in crop yields in the Niger Delta. The oil

industry has caused soildegradation through multiple mechanisms. Soil pollution

has led to a decline of soil fertilitythrough the dumping and buildup of toxic

substances. There has been a deterioration of soilphysical properties as a result of

reduced organic matter (the structure aeration and waterholding capacity of soil is

affected) and reduction of soil organisms. There has also been anassociated decline

on soil biological activity. Other devastating affects of polluting activitiesincluding

water logging, increases in salt or starch soil content sedimentation. The aim of

thisproject is embarked upon for the sole purpose of determining the level of heavy

metals in

cassava (Mannihotesculenta), yam (Dioscoreaspp), and cocoyam (Xanthosoma

spp) found in Niger Delta area of Nigeria.

CHAPTER TWO

LITERATURE REVIEW

Cassava is commonly known as Maniac, Scientific name Manihotesculenta belong

to the familyEuphorbiaceae is originated in Brazil and Paraguay. (Stephen, 1995).

Cassava root isanatomically a true root, not a tuberous root. The root cannot server

for vegetative propagation.Root size and shape depend on variety and environment

conditions. Variability in size within avariety is greater than that found in other

root crops. Cassava roots are generally from 15-l00cmlong and 3-15cm wide. They

are cylindrical, conical or oval, with a coffee, pink orcream-coloured peel which is

covered by a thin brown bark. The parenchyma is generally white,cream or yellow.

The root is composed of three distinct tissue bark (periderm) peel andparenchyma.

The parenchyma is the edible potion of the fresh root, and comprisesapproximately

85% of the total weight, the parenchyma consists of xylem vessels radially

distributed in a matrix of starch-containing cells. A central fibrous vascular bundle

becomesprogressively large as the root mature. Other fibrous bundles may develop

throughout the root.The peel layer comprises sclerenchhyma, cortical parenchyma

and phloem, and constitutes12% of the root weight, with the periderm layer

comprising another 20%. The cassava plant is ahighly efficient production of

carbohydrate mainly in the form of starch.It is the fourth most important source of

calories in human diet in tropical region of the world. (Wheathey, 1995).

The crop status of cassava is a perennial woody shrub, grown as an annual.

Cassava is a majorsource of low cost carbohydrates for populations in the lucid

tropics. (Onwueme, 1995).

The nutritional value and uses of cassava. Cassava is grown for its enlarged

starch-filled roots,which contains nearly the maximum theoretical concentration of

starch on a dry weight basisamong food crop fresh roots contain about 30% starch

and very little proteins. Roots areprepared much like potation. They can be peeled

and boiled, baked or fried. It is notrecommended to eat cassava uncooked because

of toxic concentration of cyanogenicglycosides that are reduced to innocuous

levels through cooking. In traditional settings of theAmericas, roots are grated and

the sap is extracted through squeezing or pressing. Thecassavaisthen

furtherdriedovera firetomakeamealorfermentedand cooked.

Themealcanthenbedehydrated with wateroraddedtosoupsor stews. In Africa, roots

are processed inseveral different ways. They may be first fermented in water. Then

they are either Sun-dried forstorage orgratedandmade into a dough that iscooked.

Alcoholic beveragescan be made from the roots. Youngtender leavescan beusedasa

potherb, containing high levels of protein(8-10%) prepared in asimilar manner as

Spinach, care should be taken to eliminate toxiccompound during the cooking

process. One clone with variegated leaves is planted as an, ornamental (cock,

l985).

Toxicities in cassava is famous for the presence offree and bound

cyanogenic glycosides,Linamarin and lotausualin. They are converted to HCN in

the presence of Linamarase anaturally occurring enzyme in cassava. Linamarase

acts on the glycosides when the cells areruptured. All plant parts contain

cycinogent glycoside with the leaves having the highestconcentration. In the roots,

the peel has a higher concentration than the interior: in the past,cassava was

categorized as either sweet or bitter, signifying the absence or presence of

toxiclevels of cyanOgenic glycosides. Sweet cultvars can produce as little as 20mg

of HCN per kg of

fresh roots, while bitter ones may produce more than 50 times as much. The

bitterness is

identified through taste and smell. This is not a totally valid system, since

sweetness is not

absolutely correlated with HCN producing ability. in case of human malnutrition,

where the diet

lacks protein aid iodine, under processed roots of high HCN cultivars

may result in serious health problems (Stephen, 1995).

According to coursey (1973) among others have reported chronic and

aculacyaaicde toxicity in

humans and animals in cassava diets. Ecology of cassava is a tropical root crop,

wquixing at

least 8 Months of warm wealth to produce a crop. It is traditionally grown in a

savanna

climate but can be grown to extremes of rainfall. in most areas, it does