Abstract

Heavy metals are generally referred to as those metals which possess a specific density of more than 5 g/cm3 and adversely affect the environment and Living organisms (Jarup L, 2006) They, without doubt, are important constituents for plants and humans, when present only in small amount. Some micronutrient elements may also be toxic to both animals and plants at high concentrations. For Instance, copper (Cu), chromium (Cr), fluorine (F), molybdenum (Mo), nickel (Ni), Selenium (Se) or zinc (Zn).

Waterleaf (Talinum triangulare) is a non-conventional vegetable crop of the Portulaea family which originated from tropical Africa and is widely grown in West Africa, Asia and South America Based on its persistent and cumulative nature, as well as the probability of potential toxicity effects of heavy metals as a result of consumption of leafy vegetables and fruits, there is a need to test and analyse this food item to ensure that the levels of these trace elements meet the agreed international requirements.It is on this basis that this study was designed to determine the concentrations of heavy metals in Waterleaf(Talinum triangulare) as well as analyse it’s growth parameters.

The waterleaves were planted following a line transect with S1 being the point source. S2 was at 3.5m,S3 at 6.5m and S4 at 9m. S1, the point source produce the tallest waterleaf with a height of 27.2cm and it had a lower temperature of 26.1°c. S2 recorded the highest electrical conductivity as well as total dissolved solids value with 170S/m and 85ppm respectively. The height of the water leaves are seen to decrease from the point source downwards. No branches nor flowers were produced. Based on this, the point source tend to be more favourable for the plant growth. It is recommended that an analysis of heavy metals concentration in the soil be carried out.

CHAPTER ONE

INTRODUCTION

Heavy metals are generally referred to as those metals which possess a specific density of more than 5 g/cm3 and adversely affect the environment and Living organisms (Jarup L, 2006) They, without doubt, are important constituents for plants and humans, when present only in small amount.

Some micronutrient elements may also be toxic to both animals and plants at high concentrations. For Instance, copper (Cu), chromium (Cr), fluorine (F), molybdenum (Mo), nickel (Ni), Selenium (Se) or zinc (Zn). Other trace elements such as arsenic (As), cadmium (Cd), mercury (Hg) and lead (Pb) are toxic even at small concentrations. Heavy metals, being persistent and non-biodegradable, can neither be removed by normal cropping nor easily leached by rain water (Kadeeja et al,2013)

Adverse human health effects of these toxic Elements have been documented. Lead may cause Birth defects, abnormality in behavior and learning Problems in children, decreased kidney function, a Reproductive disorder, cardiovascular problems, etc. Human health effects of cadmium include Genetic disorders, cancer, impairment of renal Function, bronchiolitis, a decrease in hemoglobin Level, etc. Cadmium may cause nasal irritations, Cancer, bronchitis and ulcerations of the septum, Decreased pulmonary function, etc

They might be transported from soil to ground waters or may be taken up by plants, including agricultural crops. For this reason, the knowledge of metal plant interactions is also important for the safety of the environment however there has been increasing interest in determining heavy metal levels in public food supplied. However, their concentration in bio-available form is not necessarily proportional to the total concentration of the metal (Opaluwa et al, 2012; Nwachukwu et al 2010).

Most plants and animals depend on soil as a growth substrate for their Sustained growth and development. In many instances the sustenance of life in the Soil matrix is adversely affected by the presence of deleterious substances or Contaminants. The entry of the organic and inorganic form of contaminants results From disposal of industrial effluents (Gowd et Al,2010) The source of the organic And inorganic elements of the soil of contaminated area was mainly from unmindful Release of untreated effluent on the ground.

The Contamination of soils with heavy metals or micronutrients in phytotoxic Concentrations generates adverse effects not only on plants but also poses risks to Human health (Murugesan et Al,2008).

World Health Organization (WHO) estimates that about a quarter of the diseases facing mankind today occur due to prolonged exposure to environmental pollution.   Heavy metal pollution of the environment, even at low levels, and their resulting long-term cumulative health effects are among the leading health concerns all over the world. Heavy metals are known as non-biodegradable, and persist for long durations in aquatic as well as terrestrial environments. They might be transported from soil to ground waters or may be taken up by plants, including agricultural crops (Oluyemi EA et Al,2008).

It  is well known that high industrial and traffic activities contribute high levels of heavy metals to the environments. Plants grown around such areas are likely to absorb these metals either from the soil through the roots or from atmospheric contaminants through the leaves (Fifield W & Haina I, 1997). The soil contamination by heavy metals can transfer to food and ultimately to consumers. For instance, plants accumulate heavy metals from contaminated soil without physical changes or visible indication, which could cause a potential risk for human and animal (Osman E et Al,2012).

Waterleaf (Talinum triangulare) is a non-conventional vegetable crop of the Portulaea family which originated from tropical Africa and is widely grown in West Africa, Asia and South America (Schippers,2000). Waterleaf as a vegetable has Some inherent characteristics which makes it attractive to small-holder farmers and Consumers.

Firstly, it is a short duration crop which is due for harvest between 35-45 days after planting (Rice et al., 1986). Secondly, in the study area it is used as a “softer” when cooking fibrous vegetables such as Eru (Gnetum africanum). It also has some medical values in humans and acts as green forage for rabbit feed management (Ekpenyong, 1986) (Aduku et al.,1990). In addition, waterleaf production provides a complementary source of income to small scale farming households (Udoh, 2015).

Waterleaf (Talinum triangulare), like many other leafy vegetable is cultivated in home gardens to improve nutritional quality for the family and may provide additional income for female farmers. However, the role of Talinum cultivation is often counteracted by declining soil fertility (Billa et al., 2017). As seen in (Aja et al., 2010) waterleaf is an excellent source of tannins, alkaloids, saponins and flavonoids which suggests its potential medicinal and dietary benefits. These results show that the leaves contain considerable proportions of bioactive compounds essential for preventing and treating various ailments

Based on its persistent and cumulative nature, as well as the probability of potential toxicity effects of heavy metals as a result of consumption of leafy vegetables and fruits, there is a need to test and analyse this food item to ensure that the levels of these trace elements meet the agreed international requirements.It is on this basis that this study was designed to determine the concentrations of heavy metals in Waterleaf(Talinum triangulare).

1.1 Statement Of The Problem.

Soils around the world are contaminated with heavy metals such as Copper (Cu), Flourine (F),Nickel(Ni), Selenium(Se), Cadnium(Cd),Mercury(Hg)… Even in small concentrations, these heavy metals are toxic to all life forms since they are non-biodegradable, persistent and can not be removed neither by normal cropping nor leaching by rain water (Kadeeja et Al,2013).

High concentration of bioavailable forms of heavy metals causes production of free radicals and reactive oxygen species in plant cells which leads to altered metabolism, growth reduction, and reduced biomass production hence reduced yield(Manara,2012). As such, knowledge of metal plant interaction is very necessary.

Here, a faculative Crassulacean Acid Metabolism (CAM) species, Talinum   triangulare which has evolved it’s water saving strategy and improved their efficiency of water usage, is used as a model to carry out this research on the impacts of heavy metals on plants. This is because it has a short life cycle, it servers as a softener for fibrous vegetables like eru and okongobon and it is also commonly eaten.

1.2 Research Questions

1. What are the physiochemical parameters of the garage soil?
2. What are the growth parameters of waterleaf?
3. What chemicals are mostly used in these garages?
4. What are the different heavy metals found in the area?
5. What is the concentration of different heavy metals from the garage in the waterleaf?

Read More: Environmental Science Project Topics with Materials