DETERMINATION OF HEAVY METALS IN SOME SELECTED VEGETABLES IRRIGATED WITH POLLUTED WATER IN KABALA WEST AREA OF KADUNA STATE
ABSTRACT
This study was carried out to assess the levels of different heavy metals such as Lead, Cadmium and Zinc in Vegetables like cabbage, lettuce, spinach, Bitter leaf and pumpkin irrigated with polluted water in different farms in Kabala West area of Kaduna state, the concentrations of the heavy metals were determined using Atomic absorption spectrophotometric analysis, the result shows that lead (2.130-9.075 mg/kg), Cadmium (1.365-1.735 mg/kg) and Zinc (2.720-6.765 mg/kg) were detected in all the samples except for Zinc which was not detected in lettuce and cabbage. The concentration of lead (9.075 mg/kg) detected in spinach was the highest and that of cadmium (1.365 mg/kg) detected in bitter-leaf was the lowest in all the samples analyzed. The result also indicated that Lead and cadmium detected in all the samples analyzed in this project were above the permissible limit of (0.3 mg/kg) and (0.10 mg/kg) respectively with the exception of Zinc which was below the permissible limit of (100 mg/kg) set by FAO/WHO in 2001.
CHAPTER ONE
1.0 INTRODUCTION
The consumption of vegetables as food offer rapid and least means of providing adequate vitamins, supply minerals and fibers. Vegetables that are used as food include those used in making soups or served as integral parts of the main sources of a meal. Leafy vegetables occupy a very important place in the human diet (Zurera et al., 1999), but unfortunately constitute a group of food which contributes maximally to nitrate and other anions as well as heavy metal consumption. Heavy metals deposition are associated with a wide range of sources such as small scale industries (including battery, Metal smelting and cable coating industries); vehicular emissions, and diesel generator sets. Heavy metals such as cadmium, lead and zinc are important environmental pollutant, particularly in areas where vegetables are irrigated with waste water, consumption of vegetables such as spinach, cabbage, lettuce, Bitter leaf and pumpkin by humans and animals pose serious health hazards, Although some heavy metals as Lead, Cadmium and Magnesium are important in plant nutrition, many of them do not play any significant role in the plant’s physiology. The uptake of these heavy metals especially into the human food chain is done through these leafy vegetables and they have harmful effects on health (Jarup, 2003).
Vegetables act as neutralizing agents for acidic substances formed during digestion, as human activities increases especially with the application of modern technology, pollution and contamination of human food chain has become inevitable. Heavy metals cannot be underestimated as these food stuffs are important components of human diet, they are very rich and comparatively cheaper sources of vitamins, Consumption of these items provides taste and palatability increases appetite and provides fibre for digestion and prevent constipation (Agrawal, 2011). Heavy metal contamination of food item is one of the most important aspect of food quality assurance; International and national regulation on food qualities have lowered the maximum permissible levels of toxic metals in food items due to an increased awareness of the risk these metals pose to food chain contamination.
Rapid and Unorganized industrialization and Urbanization has contributed to the elevated levels of metals in the urban environment in developing countries, Heavy metal are non bio- degradable and persistent environmental contaminants which may deposited on the surfaces and then absorbed into the tissues of the vegetables; Plants take up heavy metals by absorbing them from deposits on the parts of the plant exposed to the polluted water (Amoah, 2008) Waste water from industries of mining electroplating paints or chemical laboratories often contains high concentrations of heavy metals, These elements at concentration exceeding the physiological demand of vegetables, not only could administer toxic effects in them but also could enter food chain, get biomagnified and pose a potential threat to human health. Heavy metal contamination in agricultural soils from waste water irrigation is of serious concern due to its implications on human health.
1.1 EFFECTS OF HEAVY METALS ON HUMAN HEALTH
Small amounts of heavy metals are needed in our environment and diet and are actually necessary for good health, but large amount of any of them may cause acute or chronic toxicity (poisoning). Heavy metal toxicity can result in damaged or reduced mental and central nervous function, lower energy levels and damage to blood composition, lungs, kidneys, liver, and other vital organs. Long term exposure may result in slowly progressing physical, muscular, and neurological degenerative processes, allergies are not uncommon, and repeated long-term contact with some metals (or their compounds) may cause cancer (WHO, 2006). For some heavy metals, toxic levels can be just above the background concentrations naturally found in nature. Therefore, it is important to learn about heavy metals and take protective measures against excessive exposure. The association of symptoms indicative of acute toxicity is not difficult to recognize because they are usually severe, rapid in onset, and associated with a known ingestion or exposure. Symptoms include: cramping, nausea and vomiting; pain; sweating; headache difficulty in breathing impaired cognitive motor, and language skills, mania and convulsions symptoms of chronic exposure (impaired cognitive and language skills, learning difficulties; nervousness and emotional instability; and insomnia, nausea, lethargy, and feeling ill) are also usually recognized; however, they are much more difficult to associate with their cause(Jarup, 2003). Symptoms resulting from chronic exposure are very similar to symptoms of other health conditions and often develop slowly over mouths or even years. Sometimes, symptoms of chronic exposure subside; thinking the symptoms are related to something else people postpone seeking treatment. (Khillare et al., 2004).
1.2 BENEFITS OF HEAVY METALS
In small quantities, certain heavy metals are nutritionally essential for a healthy life. Those elements, or some form of them, fruits and vegetables and in commercially available multivitamin products (WHO, 2006), this research work focuses on vegetables because it is widely consumed in Nigeria, so it is important to know about their relationship with heavy metals. Diagnostic medical application include direct injection of gallium during radio logical procedures dosing with chromium in parent nutrition mixtures, and the use of lead as x-ray shield (Jassir, M.S., et al , 2005). Heavy metals are also common in industrial applications such as the manufacture of pesticides, batteries, alloys, electroplated metal parts, textile dyes, steel, and so forth (WHO, 2006). Many of these products are in our homes and add to the quality of life when properly used.
1.3 AIMS AND OBJECTIVES
The aim of this project work is to determine heavy metals in some selected vegetables in Kabala West, Kaduna, Nigeria..
Objectives
· The objective of this work is to ascertain the level of heavy metals in analyzed samples
· To determine the concentration of heavy metals in the selected vegetables
1.4 SCOPE OF WORK
The scope of this project work covers the determination of the presence of heavy metals in vegetables grown in kabala west area of Kaduna state, and also to determine the various concentrations of the heavy metals in the selected vegetables.
JUSTIFICATION
Previous projects have been carried out to ascertain different levels of heavy metals in soil and water samples, but this project specifically targets heavy metals in vegetables grown and irrigated with polluted water in Kabala area of Kaduna state.