Investigation of Some Heavy Metals in Water, Soil and Spinach Samples From Farmlands Surrounding Kwari Pond, Kwangila Zaria
Chapter One
Aim
This research aims to investigate the levels of Cr, Cd, Pb, Zn, and Mn in water, soil, and spinach samples from farmlands surrounding Kwari Pond and to determine the physicochemical parameters of water samples from Kwari Pond for its stability for irrigation since reports relating to the analyses of water, soil and vegetation around Kwari pond are not available in literature.
OBJECTIVES
The objectives of this research are to:
- Assess the levels of Cr, Cd, Pb, Zn and Mn in the water, soil and spinach samples from and around Kwaripond;
- Compare the levels of Cr, Cd, Pb, Zn and Mn in the samples with the regulatory standards
- Determine the concentration of the relevant physico-chemical parameters for water quality requirement for irrigation; and
- Make recommendations on the suitability or otherwise of Kwari pond water for irrigation farming.
CHAPTER TWO
LITERATURE REVIEW
HEAVY METALS AND THEIR OCCURRENCE
Metals with density or specific gravity greater than 5g/cm3 are known as heavy metals. They are commonly referred to as trace metals because they are present at much lower concentrations in water compared to major ions SO42-, Cl–, NO3-, Mg2+and Ca2+ (Radojevic and Bashkin, 1999). Heavy metals are poisonous to living organisms and are sometimes referred to as toxic metals. Metals most often involved in human poisoning are Pb, Hg, As and Cd. Some heavy metals, such as Zn, Cu, Cr, Fe and Mn, are required by the body in small amounts, but can be toxic in larger quantities (Duffus, 2002).
Heavy metals occur naturally in the ecosystem with large variations in concentrations. In modern times, anthropogenic sources of heavy metals, i.e. pollutions from the activities of humans, have introduced some of these heavy metals into the ecosystem. The presence of heavy metals in the environment is of great ecological significance due to their toxicity at certain concentrations, translocation through food chains and non biodegradability which is responsible for their accumulation in the biosphere (Aekola et al., 2008).
Heavy metals like iron, tin, copper, manganese and vanadium occur naturally in the environment and could serve as plant nutrients depending on their concentrations. Mercury, lead, cadmium, silver, chromium and many others that are indirectly distributed as a result of human activities could be very toxic even at low concentrations. These metals are non- biodegradable and can undergo global ecological circles (Oluyemi et al., 2008).
The problem of environmental pollution due to toxic metals has attracted the attention of researchers worldwide. The toxic heavy metals entering the ecosystem may lead to geoaccumulation, bioaccumulation and biomagnification. Heavy metals like Fe, Cu, Zn, Ni and other trace elements are important for proper functioning of biological systems and their deficiency or excess could lead to a number of disorders (Ward, 1995).
SOURCES OF HEAVY METAL CONTAMINATION
Heavy metals are introduced to environment either by natural means or anthropogenic activities.
- Natural sources: In nature, excessive levels of trace metals may occur by geographical phenomena like volcanic eruptions, weathering of rocks; leaching into rivers, lakes and oceans due to action of
- Anthropogenic sources: In ancient times, heavy metals were released in small amounts while mining and smelting of metal ores in open fires. With the industrial revolution, metals are extracted from natural resources and processed in industries from where heavy metals leak into atmosphere. Similarly, traces of heavy metals get deposited in the environment through discharge; domestic waste, agricultural runoff and automobile
According to Hariprasad and Dayananda(2013) the various sources through which heavy metals reach the environment are:
- Smelting or processing of ores ofmetals,
- Mining
- Dumpsites
- Burning of fossil fuels such as coal, petrol and keroseneoil,
- Storm runoff containing compounds of heavy metals from agriculturalfarmlands
- Discharge of industrial, domestic and hospitalwaste
- Storm runoff of oil spillage from highways and automobile exhaust..
Wastewater from urban area is being used profitably to irrigate crops in the vicinity of cities from time unknown. It is still considered rich in plant nutrients and organic matter. However, the situation has changed now because, in many cities and towns the wastewater is sold for secondary use and it is a good source of income to municipalities (Saleem et al., 2005).Heavy metal is present in diminutive quantities in the water and is further added due to soil erosion and leaching of minerals. However, in the recent past, freshwater pollution due to heavy metals has become a hazard due to discharge of industrial effluents. Heavy metals like Mn, Fe, Ni, Cu, Zn and Cr are essential for the growth of organisms, while Pb, Cd, Hg and Ag are not biologically essential, but definitely toxic. Even the essential heavy metals if beyond optimum threshold levels could be hazardous and toxic. After entering the water, metals may precipitate, gets adsorbed on solid surface, remain suspended in water or taken up by fauna. A very important biological property of metal is its tendency to accumulate (Eralagere and Bhadravathi, 2008).
The main sources of heavy metals to vegetable crops are their growth media (soil, air and water) from which these are taken up by the roots or foliage. Most of our water resources are gradually becoming polluted due to the addition of foreign materials from the surroundings. The foreign materials, according to Karnataka State Pollution Control Board (KSPCB) (2002), include organic matter of plant and animal origin, land surface washing, and industrial and sewage effluents. Rapid urbanization and industrialization with improper environmental planning often lead to discharge of industrial and sewage effluents into lakes. The lakes have a complex and fragile ecosystem, as they do not have self cleaning ability and therefore readily accumulate pollutants (Akinola et al. 2006).
CHAPTER THREE
MATERIALS AND METHODS
The reagents and equipment used in order to achieve the objectives of this research work are listed in Appendix I. All reagents used were of analar grade.
Description of the Study Area
Kwari pond is located near Kwangila, Zaria, along Kaduna-Kano highway on latitude 110 08.127‘N and longitude 007042.404‘E. The pond is surrounded by Kaduna-Kano Highway to the North, Kwangila residential houses and their dumpsites to the West, Maraba Clinic and Farmlands to the South and hollow block producing factories to the East. The surrounding farmlands rely entirely on the pond for irrigation farming during dry season. Substantial quantities of vegetable crops such as tomatoes, spinach (Amaranth caudatus), lettuce (lactucasativa), pepper and Onion (Allium cepa) are produced annually from the irrigation practice.
By virtue of its location, the pond is subjected to various forms of pollution from anthropogenic sources. The following were identified as possible sources of heavy metal pollution of the pond:
- Domestic Liquid Waste from Kwangila residentialhouses
- Leachate from dumpsites near thepond
- Storm runoff from hollow block producingindustries
- Maraba HospitalWaste
- Storm runoff containing compounds of heavy metals from agriculturalfarmlands
- Contaminated Storm Washed off of Kaduna-Kano RoadHighway
CHAPTER FOUR
RESULTS
Physico-chemical Parameters of the Pond Water (IrrigationWater)
The physico-chemical parameters of the pond water from February to July 2014 are presented in Table 4.1. The temperature ranges from 27.58oC (July) and 32.97oC (May) and the average value was found to be 29.04oC.The pH values varied between 5.80 (May) and 9.17(February) and the mean concentration recorded was 7.72.Generally the pH of the pond water tended to be alkaline in February, March, June and July except for April and May where the pH were acidic. The conductivity varied between 675.33µʃ/cm (July) and 1855.83µʃ/cm (May) and the average conductivity was found to be 680.50µʃ/cm as shown in Table 4.1. The salinity of the pond ranges from 0.30%to 0.87 % and the mean salinity was found to be 0.44%. The dissolved oxygen values fluctuated between 0.80mg/L (May) and 2.25 mg/L (June) and the mean concentration was 1.30mg/L. Turbidity was found to vary between 14.00NTU (July) and 64.33NTU (May) and the average turbidity of the pond water was found to be 28.19NTU. The total dissolved solid concentration in the pond water was found to vary between 309.00mg/L (June)and 868.33mg/L (May) and mean concentration was found to be 450.8.
CHAPTER FIVE
DISCUSSION
Physico-chemical Parameters and Levels of Heavy Metals in the Pond Water (Irrigation Water)
The mean temperature of the pond throughout the period of the research was 29.04oC with the highest recorded temperature of 32.97oC in the month of May and the least,27.58oC, in the month of July (Table 4.1). Eneji et al., (2014)reported similar values(29.8oC – 31.0oC) for river Mada Nasarawa Nigeria. Temperature influences the amount of dissolved oxygen in water, the higher the temperature the lower the dissolved oxygen content.
The pH range for the period was 5.80 in May to 9.17 in February with mean pH of 7.72. These values are slightly above the limits of 6.0-9.0 set by FAO (1985) for irrigation water; the values implies that the pond is alkaline in the months of February, March, June and July and acidic in April and May which may likely lead to the high concentration of the metals in the pond. This is higher than the pH of 6.81 reported by Aremu etal., (2010) in the physico-chemical parameters of a pond from derelict udege mines of Nasarawa state, Nigeria. The pH is a function of the dissolved material in water and should be less than 8.5 (USEPA, 2002).
Conductivity range of 675.83μmhos/cm- 1855.83μmhos/cm observed falls within the permissible limits of 750 – 2250μmhos/cm(Camberato, 2001). The higher conductivity recorded from February – May (842.83 – 1855.83μmhos/cm) could be attributed to reduced water volume and high rate of evaporation during the period, while the relatively lower conductivity values (675.33– 680.50μmhos/cm) might be due to water dilution. These values indicate high salinity level that.
CHAPTER SIX
SUMMARY, CONCLUSION AND RECOMMENDATION
Summary
Levels of Cd, Zn, Mn, Cr and Pb were investigated in spinach plant irrigated with pond water using Atomic Absorption Spectroscopy. The physico-chemical parameters and the levels of the metals in the pond water samples were analyzed also. The temperature, salinity, conductivity and dissolved oxygen of the pond water were within permissible limits; however, the pH was slightly above the permissible limit which leads to the high concentration of the metals in the pond. The values of 0.53, 0.94 and 5.22mg/L for Cd, Mn and Cr respectively (all through the months) in the pond water were higher than the US permissible limits for irrigation water (0.01, 0.2 and 0.1mg/L respectively), while the levels of Zn was higher in the month of May only and Pb was higher in the months of May and April. The trend in metal concentration in the pond water is Pb>Cr>Mn>Zn>Cd. The high levels of these metals is a clear indication that the pond water used on farm lands around the pond for irrigation is polluted and crops cultivated on those farms may be harmful for human consumption. The high levels of these metals in the pond water is likely due to waste water discharge from a clinic nearby. A similar report was been made (Sunday and Agbaji, 2012). A block moulding industry whose source of water is the pond where and all washings of tools and equipment is done in the pond is a possible source of the metals. Runoffs from the farmlands and a dumpsite close to the pond may have also significantly contributed to these metals which is in agreement with earlier reports (Suhendan et al., 2010; Tulay, 2010).
The concentrations of the metals in the soil samples from the three farmlands were generally of the order Mn>Cr>Pb>Zn>Cd and the mean concentrations of Cr (26.8mg/kg), Pb (20.3mg/kg) and Zn (12.7mg/kg) were below the WHO/FAO recommended maximum limits of 100, 85 and 200mg/kg respectively except for Mn(91.9mg/kg) and Cd(1.7mg/kg) with allowable limits of 80 and 0.8mg/kg. The general trend of the metals in the spinach samples was observed to be Mn>Zn>Cr>Pb>Cd, the mean concentrations of Cd(1.52mg/kg), Cr (17.37mg/kg) and Pb (13.73mg/kg) were higher than the WHO/FAO allowable limits of 0.30mg/kg, 1.50mg/kg and 10.0mg/kg for Cd, Cr and Pb respectively. These high concentrations might be due to concentration effect, atmospheric deposition from urban and agricultural areas and also the use of fertilizers and metal based pesticides in agriculture.
On the other hand, the mean concentrations of Zn (21.8mg/kg) and Mn (40.0mg/kg) were below the WHO permissible limits (50.0, 200.0mg/kg).Transfer factor of the metals from the soil to the spinach plant in farm 1 followed the order Zn>Cd>Cr>Mn>Pb while orders of Zn>Cd>Pb>Cr>Mn and Cd>Zn>Pb>Cr>Mn were observed for farms 2 and 3 respectively. Since the metals in the spinach were higher than permissible limits, consumption over time might present problems as the tendency for the soil to accumulate and transfer metals to the spinach cultivated increases which will subsequently get to man through the food chain.
Conclusion
The following conclusions were arrived at based on this research:
- The Water, spinach and soils contained variable levels of heavy metals (Cr, Cd, Mn, Pb and Zn).
- Agronomic practices such as application of fertilizers and use of waste water can affect bioavailability and crop accumulations of heavy
- Consumption of these vegetables as food may constitute possible health hazards to humans at the time of the
- The results obtained in this study would go a long way in providing a baseline data for the assessment of the distribution of these metals in spinach grown in the surrounding of Kwari pond Kwangila,
- Since in this research the mean concentrations of most metals were above the WHO permissible thresholds, they pose serious health threat as consumption over time could accumulate the metals in the human body. Consumers of vegetables irrigated with polluted water are at a very high risk of poisoning by these toxic metals over
Recommendation
- As much as possible, polluted water should be avoided for use as irrigation water. Where necessary, some form of treatment could be introduced before being used for
- Continuous monitoring is very important to ascertain the safety of consumption of such irrigated
- Farmers should be educated on the problems associated with excessive usage of fertilizers and other chemicals, as well as irrigating the crops with waste polluted water and the need to grow crops with safe levels of heavy metals and the adverse health implications in consuming polluted
- Consumers of the spinach and other crops cultivated via irrigation with polluted water should be monitored to assess the bioaccumulation of the metals in their body over
- Fish and sediment should be analyzed for heavy
- Occasional application of low salinity water is required forleaching
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