SPARTIAL DISTRIBUTION OF CADMIUM AND LEAD OF ROAD SIDE IN NIGERIAN SOILS
BY
AHAMEFULE WILSON
ACKNOWLEDGEMENT
First of all, I want to render my sincere appreciation to God, for his infinite mercy and the gift of life
In the course of this work, so many people contributed immensely to the success of it, first of all I want to appreciate my parents for their wonderful love and care, my siblings and my relatives too numerous to mention who contributed one way or the other to ensure my success in this academic pursuance.
I appreciate Prof Martin Onuh, Dr C.C Njoku (mrs) for your support and advices, Prof N.N Oti (mrs), Prof E.U. Onweremmadu, Dr C.C. Onyeanuforo, Dr Larry Amajuoyi, Dr N.N Nwawuike, also thank Prof Jude Uwalaka, Dr Patrick Nze, Mrs Jane Njoku, Dr Chis Igbozuruike, Dr Urban Osuji and for their support and encouragement
ABSTRACT
The Research was embarked to evaluate the heavy metals (Cd and Pb) in the selected soil areas (Owerri, Mbaise, and Obowo) of Owerri-Umuahia highway, Imo State. The aim is to educate and guide citizens of such area on how to make use of the areas near the highway in harnessing and producing edibles for human consumption. The soils amples were collected at horizontal spread of 0-15, 15-30, 30-45, and 45-60 in all areas. The three represented locations are Owerri 0-60, Mbaise (0-60), and Obowo 0-60. the total of 54 samples were collected including six control samples from a non-high way road. The levels of Cd and Pb varies and they were decreasing in sequence as the movement increases off the mobility road as 2/3 results. The mean value of Cadmium ranges from (2.2 mg/kg – 2.03 mg/kg). the mean value of Lead ranges from (24.67 mg/kg – 21.17 mg/kg). The pH levels ranges from (6.41) to (5.23), with the highest content as (6.41) in Owerri. The Phosphorus level ranges from (4.53) to (15.67), with the highest content in Mbaise at (16.06). The Nitrogen ranges from (0.11) to (0.73) with the highest level at Obowo at (0.73). The Organic Carbon levels are tiny different as it ranges from (1.28) to (1.31) with the highest level in Obowo. In Obowo, the Organic Matter is higher with (2.50) as its content, but lowest in Owerri at (1.86).The base saturation ranges from (75.90) to (82.07) as the highest is in Obowo. The calcium level ranges from (2.40) to (3.56) as the highest content is in Obowo with (3.56). The trend is similar in the other properties like Magnessuim, Potassium, Sodium, Exchangeable Acidity, and CEC where the contents increases from Owerri to Obowo along the high way. In the case of Exchangeable Acidity the content is a higher in Mbaise at (1.42) than the other locations, with lowest occurring at Owerri (1.27).
TABLE OF CONTENT
ABSTRACT I
TABLE OF CONTENTS II
CHAPTER ONE
1.1 Introduction 1
1.2 Objectives Of Study 2
Chapter two: Literature review
2.1 Heavy Metals In The Soil 3
2.2 Factors Affecting Heavy Metals Availability And Mobility 5
2.3 Behaviour of Cd and Pb in the Soil 6
2.4 Toxicity Of Cd AND Pd in the Soil 7
2.5 Critical Levels of Nutrients For Plant Growth Stages 8
CHAPTER THREE: MATERIALS AND METHOD
3.1 Study Area 11
3.2 Field Operations 13
3.3 Post Field Operation 14
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 The Results Of Heavy Metal Levels Are Presented In Tables 17
4.2 Result Discussion
CHAPTER FIVE
5. Conclusion 26
5.2 Recommendation
REFERENCES
APPENDIX
CHAPTER ONE
1.1 INTRODUCTION
The presence of toxic metals in the environment continues to generate a lot of concern to environmental scientists; Heavy metals are widely distributed in the environment with source mainly from soils and weathering of rocks. However, levels of these metals in the environment have increased tremendously as a result of human inputs, such as heavy vehicles oil leakage, wear-off tyres and smoke from cars, motorcycle and other automobiles.
Recently, studies have shown that heavy metals and metalloids with atomic density greater than 6g/cm3 can accumulate and persist in soils at environmentally hazardous level. Farmers often cultivates vegetable (Pumpkins, Cabbage, Garden Egg and fruits and other crops very close to the roads, some farmers even plant very close to the road asphalt, when particulate matters from smoky vehicles passing through the road, the particulate matter settle later through dew and dust on agricultural crops; These can cause serious chronic effect to the human health such as high blood pressure, kidney infection etc (Basta, N.T. Patone, P.S. and Tabatabia, M.A., 2008).
Heavy metals are defined as metallic elements that have relative high density compare to water. Examples are Mercury (Hg), Cadmium (Cd), Arsenic (As), Chromium (Cr), Thallium (Ti), Nikel (Ni), Iron (Fe) and Lead (Pb). These heavy metals are concerned with the relative high density, and its toxicity or poison at low concentrations. Meanwhile, Hg, Pb, Cd, Cr, and As have been the most common heavy metals that induce human poisonings.
Due to their persistence and non-biodegradation, these metals accumulate in soil (Abidal et al.,2009) their concentration on the surface and soil close to the highways are often high. Some may migrate to the surface, ground and underground water system, through infiltration and percolation thereby causing contamination.
1.2 OBJECTIVES OF STUDY
The main objective of this study is to evaluate the concentrations of heavy metals, Cd and Pb in the roadside soils along Owerri-Umuahia highway in Imo state.
Specific objectives includes
To determine the horizontal spread of these metals off the road
To determine the physicochemical proper ties of the soil.
CHAPTER TWO
LITERATURE REVIEW
2.1 Heavy Metals in the soil
Heavy metal pollution of soils affects the quality of the environment leading to serious consequences. Many studies have reported data for the transfer of heavy metals from soil to plants and vegetables through the roots and shoots. Therefore, toxic metals can be taken up from cereal crops and transferred to their grains. Toxic metals may be classified according to their capabilities of being transferred from soil to plants as mobile metals, such as Cd and poorly mobile metals such as Pd. This property may affect their bioaccumulation in plants. Heavy metals group includes Ag, Ba, Cd, Co, Cr, Mn, Hg, Mo, Ni, Pb, Cu, Sn, Ti, Zn, and some metalloids such as As, Sb, Bi and Se.
Arsenic for example is often considered as heavy metal due to the similarity of it’s chemical properties and behavior with other heavy metals. Meanwhile, when one talks about metals and their accumulation in soils and environment in general, we look into the phenomenon of bio-accumulation ability of living organisms due to the food chain and many other activities of human being. The irrigation especially with sewage, solid waste disposal example composts refuge and sludge, the fertilizer and pesticides usage and other atmospheric depositions are all example or sources of heavy metal pollution ion the soil (Emmerich, W.E. et al.,).
2.1.1 IMPLICATIONS OF HEAVY METALS
Soil is a complex medium comprising aqueous gaseous components as well as mineral clay colloid organic solid. The minerals in the soil come from weathered rock particles on secondary clay minerals oxide of Fe, Al, Mn and carbonates. The organic solids consist of living organisms, dead plants materials and colloidal humus generated by microbial activity on the dead plant litter (Harrison J.B. 1990).
The particle of organic matter from aggregates that creates pores of different sizes, which are interconnected and filled either with air or water. The organic solid are capable of absorbing ions but of course this differs between various materials owing to the influence of redox conditions, pH and ion concentration in the soil solution. When carbonate with a pH >7 are present in the soil, they cause an increase in its heavy metal retention capacity ( Ufot, U.O., 2012 ).
Heavy metals in the soil introduced by anthropogenic activities fall into several types of pool, those associated with insoluble soil organic matter, precipitation (mixed solids), those occupying exchange sites on inorganic soil constitutes those dissolved in soil solution and specifically those absorbed on inorganic soil constitutes.
2.2 FACTORS AFFECTING HEAVY METALS AVAILABILITY AND MOBILITY
2.2.1 Organic Matter
All soils that contain organic matter vary in the amount and type of organic component which gives marked differences in chemistry of the soil. The colloidal organic matter can be categorized into humic and non humic substances. The non humic category consists of carbohydrates, organic acids, waxes and fat, while the humic comprises acidic polyelectrolytes which are yellow to black in color. The soil humus consists predominantly of humic substances and biochemical which are bound to humic polymers.
2.2.2 Soil pH
Due to chemical behaviors of heavy metals in the soil, certain reactions take place and therefore affect it, because soil is complex in heterogeneity. The soil pH is also affected by changes in redox reactions which means under reducing conditions, the pH increase and under oxidizing conditions it decreases. Heavy metals are generally most mobile under acid polymer conditions.
2.2.3 Clay Minerals
These products of rock weathering affect both the physical and chemical properties of the soil. Clay minerals have a large surface area and a permanent surface negative charge. Their mobility is greater than that of heavy metals in soils. The reasons could be that the absorption capacity of heavy metals is limited and that its mobility depends on behavioral interactions with other solid phase. Some of the sorption surfaces are clay particles Fe, Al, Mn, hydro oxides and organic matter (Jalahi and Khanlari, 2008).
2.3 BEHAVIOUR OF CADMIUM AND LEAD IN THE SOIL
2.3.1 Cadmium (Cd)
Among many heavy metals polluting the soil, Cadmium is of concern because of its harmful effects on not only humans and animals, but also the most adverse effects on microbial biomass and its activity which play an important role in the cycles of almost all the major plant nutrient cycling, soil nutrient and soil microorganisms.
2.3.2 Lead (Pb)
It is an element that is toxic to both plants and animals. When it is exposed to the environment, Lead has long resident times as a pollutant owing to its low solubility and freedom to microbial degradation. All these factors make it bio-available. Lead is immobile in soils because it tends to adsorb specifically to other solid phase which renders it the least mobile heavy metal in the soil.
Lead precipitates as highly stable compounds and it also form complexes or chelates that results from interaction with soil organic matter. The presence of Mn and Fe oxides plays a vital role in Pb adsorption and carbonates content in a soil affects the behavior of Lead.
2.4 TOXICITY OF Cd AND Pd IN THE SOIL
2.41 Cadmium: long term exposure of cadmium through air, water, soil, and food leads to cancer and organ system toxicity such as skeletal, urinary, reproductive, cardiovascular, central and peripheral nervous and respiratory systems. Cadmium levels are measured in blood, urine, hair, nail, and saliva samples.
2.4.4 Lead: lead poisoning may be caused by prolonged or exposure intensively to this metal which may result to strokes, heart attacks, hypertension and kidney disease at low level, it is harmful to adult blood.
Why are heavy metals a concern?
Heavy metals are considered as hazardous chemicals in the environment. Nonessential heavy metals are toxic to plants, animals, and humans at very low concentrations. Even the essential heavy metals also cause adverse health effects at high concentrations.
TABLE 1.1: CRITICAL LEVELS OF NUTRIENTS FOR PLANT GROWTH STAGES
ELEMENTS
Corn
Grain sorghum
Soybean
Small grains
Peanuts
Alfalfa
Bermuda grass
Nitrogen %
2.7-3.5
3.3-4.0
4.2-5.5
1.7-3.0
3.5-4.5
4.5-5.0
2.5-3.0
Phosphorus%
.25-.40
.20-.35
.26-.50
.20-.50
.20-.35
.26-.70
.26-.32
Potassium%
1.7-2.5
1.4-2.5
1.7-2.5
1.5-3.0
1.7-3.0
2.0-3.5
1.8-2.1
Calcium %
.21-1.0
1.7-2.5
.36-2.0
.20-.50
1.3-1.8
.50-3.0
-
Magnesium%
.21-.60
.36-2.0
.26-1.0
.15-.50
.30-.80
.30-1.0
-
Lead mg/kg
2.0-3.5
1.1-5.0
3.0-5.0
2.0-2.8
3.9-4.5
7.0-10
12-30
Cadmium mg/kg
.10-.33
.18-.35
1.0-2.0
.08-22
2.0-3.0
-
.03-5
TABLE 1.2: Sufficient levels of elements
Nutrients
Plants
Low
Marginal
Sufficient
High
Excess
Spring
1.5
1.5-2.0
2.0-3.0
3.0-4.0
4.0
Nitrogen%
Winter
1.25
1.25-1.75
1.75-3.0
3.0-4.0
4.0
Phosphorus%
0.15
0.15-0.25
0.25-0.5
0.5-0.8
0.8
Potassium%
1.0
1.0-1.5
1.5-3.0
3.0-5.0
5.0
Calcium%
Barleys
0.10
0.10-0.20
0.20-1.0
1.0-1.5
1.5
Lead mg/kg
Wheat
1.0
1.0-2.8
2.8-3.5
3.5-7
7.0
Cadmium mg/kg
0.9
0.9-1.1
1.1-2.0
2.0-3.0
3.0
CRITICAL VALUE OF CADMIUM AND LEAD (Cd, Pb)
TABLE 1.3 Critical value of Cadmium and Lead
Heavy metals
Cd
Pb
Low
0.15
2
Moderate
1.1 - 2.0
12.5 - 16.2
High
2.0 - 5.0
16.2 - 85
Excess
> 5.0
> 85
Source: The research gate publication, department of chemistry Imo State University; Wim De Vries, Gudrun Shutze, Steve Lots in NERC centre for Ecology and Hydrology of soils; Assesement of Pb, Zn, As, Ni, Cu, Cr and Cd in Agricultural soils around South East Nigeria
CHAPTER THREE
MATERIAL AND METHODS
3.1 Study Area
The study was conducted along Owerri-Umuahia Highway. The highway connects to Umuahia from fire service station round-about Owerri municipal through Owerri north, to Aboh Mbaise, Ahiazu Mbaise, Obowo and Umuahia south as boundary.
TABLE 2.1 GEOGRAPHICAL CORDINATES
Location
Owerri
Mbaise
Obowo
Latitude
5.48910N
5.53790N
5.60270N
Longitude
7.01760E
7.28690E
7.32200E
3.1.1 CLIMATE
Owerri-Umuahia highway area is a humid tropical forest ecosystem. The rainy season usually occurs from the month of March to mid or late days of October and often interrupted by short spell in the month of August to early September. It may last 7-14 days. It is usually cold during rainy season, also the dry season often comes from early November month to February
The annual rainfall values ranges between 2000mm to 3000mm while mean annual rainfalls ranges from 1950 to 2200mm. the rainfall pattern is bimodal with heavy experience from July to September (Enwezor, 1990).
The mean temperature is transmitted from sun through radiation. The temperature ranges from the sun 36oc to 370c.
3.1.2 VEGETATION
The area is a vegetative area of the tropical rainforest. It is characterized by multiple plant species ranging from Shrubs (Hibiscus, Dog rose, Aloe vera, Pistachio, Magnolia Liliflora etc), Herbs ( Alfalfa, scent leaf, marijuana), and Trees like Palm trees, Mango, Mahogany, Obeche, and Pear trees etc.
3.1.3 EXISTING SOIL
The Ultisols is mainly the dominant soil there (Ufot 2012), derived from weathering of major geologic materials, coastal plain sand. Although, Entisols and Inceptsisols are scantly distributed in agro-ecology, the lacteric soil type predominates and soil derived from coastal plain sand ( Ofotomata J.I., 1994)
Entisols are soils of recent origin. The central concept is soils developed in unconsolidated parent materials with no genetic horizon. Many Entisols are found are found in rocky and steep settings. Inceptisols are soils formed through alteration of parent materials. They are more developed than Entisols. The have no accumulation of clays, iron oxides, aluminum oxide or organic matter.
3.1.4 SOCIAL ECONOMIC ACTIVITIES
Marketing, tourism and agricultural practices are major social economic activities of the area. There are cultivated lands for agriculture, forestry and other natural science engagements such as fermentation of palm wines, fish farming and rearing of animals; they people has many cultural activities and outings.
3.2 FIELD OPERATIONS
3.2.1 FIELD STUDY
In owerri, Mbaise, and Obowo locations samples were collected from 0-15 from the express highway is 0-15 ft, 15-30 ft, 30-45 ft and 45-60 ft with spread. 3 locations were sampled for Owerri, 3 locations were sampled for Mbaise, and 3 locations were sampled for Obowo (100m) away. In each a total of 12 bulked control samples were collected from a non-highway road side. the total sample 54 were collected using predetermined distances 100 meters away.
3.3 POST FIELD OPERATION
Sample preparation
Samples were air dried, sieved with 2mm sieve and crushed.
Samples were stored in the polythene bag
Laboratory operations: Physicochemical analysis, heavy metals extraction, and rooting analysis.
3.3.0 THE LABORATORY OPERATIONS
3.3.1 Chemical Properties Of The Soil
Soil pH (pH) was in 1:2.5 soil/water or in Kcl ratio using pH meter.
Organic carbon (OC) was determined by wet oxidation method, while organic matter was calculated by 1.724 ie Van Bamellens factor.
Total Nitrogen (TN) was determined by regular micro Kjeldhal method (Bremmer and Mulvane, 1982)
Available Phosphorous (AP) was determined using Bray II solution (Olsens et al., 1990).
Total Exchangeable Bases were determined and extracted with NH4OAC, the calcium and magnesium in the extract was determined by EDTA titration.
Exchangeable Acidity were determined by leaching the soil with 1mkcl and titration with 0.05 NaOH.
Cation exchangeable capacity (CEC) was determined by calculating the sum of exchangeable cations [k, Na, Ca2+ and mg2+] and exchangeable acidity [H+ and Al2+].
CHAPTER FOUR
RESULTS AND DISCUSSION
4.1 The results of heavy metals Cadmium and Lead as presented in Tables 3.1, 3.2, 4.1, 4.2, and 5.0
4.1.1 CADMIUM LEVELS
Cadmium content increases horizontally in Owerri with the highest content at 0-45 feet (2.75), and the lowest is at 0-15 feet (2.25). In Mbaise, the Cadmium levels decreases as the movement off the road horizontally increases, with the highest content at 0-15 feet (2.2), while the lowest content is at 0-30 feet (1.75). The trend is similar in Obowo where cadmium levels decreases with increase in movement off the road horizontally. The highest content is at 0-15 feet (2.2), and the lowest content is at 0-30 feet.
4.1.2 LEAD LEVELS
The Lead levels decrease horizontally as the movement off the road increases with the highest content at 0-30 feet (23.5), and the lowest is at 0-45 feet and 0-60 feet. In Mbaise, Lead level varies horizontally as the movement off the road increases. The highest content is at 0-45 feet (26.0), while the lowest content is at 30-45 feet (21.5). In Obowo, the trend is similar with Owerri as the lead level decreases horizontally. The highest content is at 0-15 feet (30.5) near the express, while the lowest is at 0-60 feet (19.0).
TABLE 3.1 Levels of Cd and Pb as influenced by vehicular movement along Owerri-Umuahia highway.
Locations
Horizontal
Distance Away
From Road
Edge
0 – 15 ft
15 – 30 ft
30 – 45 ft
45 – 60 ft
Cd Pb
Cd Pb
Cd Pb
Cd Pb
Owerri
2.25 20.5
2.40 23.5
2.75 19.0
2.35 19.0
Mbaise
2.2 23.0
1.55 26.0
1.75 21.5
1.90 25.5
Obowo
2.2 30.5
1.65 23.5
1.75 24.0
1.85 19.0
Control
2.19 26.22
2.19 26.22
2.19 26.22
2.19 26.22
Cd = Cadmium Pb = Lead
4.1.4 The physicochemical properties of the soil
The physicochemical properties of the soil as shown in the table 3.2 below denotes; the pH levels ranges from (6.41) to (5.23), with the highest content as (6.41) in Owerri.
The Phosphorus level ranges from (4.53) to (15.67), with the highest content in Mbaise at (16.06). The Nitrogen ranges from (0.11) to (0.73) with the highest level at Obowo at (0.73). The Organic Carbon levels are tiny different as it ranges from (1.28) to (1.31) with the highest level in Obowo.
In Obowo, the Organic Matter is higher with (2.50) as its content, but lowest in Owerri at (1.86).The base saturation ranges from (75.90) to (82.07) as the highest is in Obowo. The calcium level ranges from (2.40) to (3.56) as the highest content is in Obowo with (3.56). The trend is similar in the other properties like Magnessuim, Potassium, Sodium, Exchangeable Acidity, and CEC where the contents increases from Owerri to Obowo along the high way. In the case of Exchangeable Acidity the content is a higher in Mbaise at (1.42) than the other locations, with lowest occurring at Owerri (1.27).
TABLE 3.2 : Physicochemical properties of the soil as influenced by vehicular movements
Textural
class
Ph
P
N
OC
OM
BS
Ca
Mg
K
Na
EA
ECEC
Mg/kg
%
%
%
%
Cmol.kg-1
Cmol.kg-1
Cmol.kg-1
Cmol.kg-1
Cmol.kg-1
Cmol.kg-1
Owerri
SiL
6.41
4.53
0.11
1.28
1.86
75.90
2.40
1.43
0.18
0.15
1.27
5.49
Mbaise
SiC
6.28
16.06
0.16
1.16
1.99
75.76
2.80
2.00
0.19
0.10
1.42
6.15
Obowo
SiL
5,23
15.67
0.73
1.31
2.50
82.07
3.56
2.31
0.27
0.13
1.40
7.84
Control
SCL
5.89
23.74
0.54
1.98
3.41
84.60
4.29
3.72
1.15
0.40
1.51
10.79
4.2 DISCUSSION OF CD AND PB HORIZONTAL SPREAD
According to the Table 4.1, the Cadmium levels decreases horizontally with increase in movement off the road in Mbaise and Obowo along Owerri–Umuahia highway. The trend is similar in the Lead (Pb) levels, it decreases horizontally as the distant increases off the road horizontally along the highway. The mean value for Cadmium ranges from (2.2mg/kg – 2.03mg/kg). The mean value for Lead ranges from (24.67mg/kg – 21.17mg/kg).
The sufficient levels of the heavy metals Cd and Pb shows that plants need very low content of Lead and Cadmium.
TABLE 4.1: The mean Levels of Cd and Pb as influenced by vehicular movement along Owerri-Umuahia highway.
Locations
Horizontal
Distance Away
From Road
Edge
0 – 15 ft
15 – 30 ft
30 – 45 ft
45 – 60 ft
Cd Pb
Cd Pb
Cd Pb
Cd Pb
Owerri
2.25 20.5
2.40 23.5
2.75 19.0
2.35 19.0
Mbaise
2.2 23.0
1.55 26.0
1.75 21.5
1.90 25.5
Obowo
2.2 30.5
1.65 23.5
1.75 24.0
1.85 19.0
Control
Mean
2.19 26.22
2.22 24.67
2.19 26.22
1.87 24.33
2.19 26.22
2.08 21.5
2.19 26.22
2.03 21.17
4.2. 1 CRITICAL VALUE OF CADMIUM AND LEAD (Cd, Pb)
In Table 4.2, the critical level of the heavy metals Cadmium (Cd) and Lead (Pb) shows that the mean value of the Cadmium is high in accumulation compared with the sufficient limit needed in plants along Owerri-Umumahia highway. Because, no value is below the moderate level of the critical value which is 1.1 – 2.0 except the horizontal distance 15-30 feet which is 1.87 mg/kg. Horizontal distance 0-15 ft, 30-45ft and 45-60 ft are all above the critical limit (moderate) to a high limit range.
The cadmium levels are on moderate value at 15-30 ft to 45-60 ft except the 0-15 ft that falls in high limit. The mean values of Lead is high from 0-15ft to 45-60 ft as the distance spread horizontally.
In reference to Tables 1.1 and 1.2, the sufficient levels of plants varies with elements. In the case of heavy metals, Cd, and Pb are needed by plants in small quantities. The Cadmium (Cd) ranges from 0.10-5.0 mg/kg in the soils, and Lead (Pb) ranges from 2.0-12.0 mg/kg.
TABLE 4.2. Critical value of Cadmium and Lead
Heavy metals
Cd
Pb
Low
0.15
2
Moderate
1.1 - 2.0
12.5 - 16.2
High
2.0 - 5.0
16.2 – 85
Excess
> 5.0
> 85
Source: The research gate publication, department of chemistry Imo State University; Wim De Vries, Gudrun Shutze, Steve Lots in NERC centre for Ecology and Hydrology of soils; Assesement of Pb, Zn, As, Ni, Cu, Cr and Cd in Agricultural soils around South East Nigeria
TABLE 5.0: Physicochemical properties of the soil as influenced by vehicular movements
Textural class
pH
P
N
OCs
OM
BS
Ca
Mg
K
Na
EA
ECEC
Mg/kg
%
%
%
%
Cmol.kg-1
Cmol.kg-1
Cmol.kg-1
Cmol.kg-1
Cmol.kg-1
Cmol.kg-1
Owerri
SiL
6.41
4.53
0.11
1.28
1.86
75.90
2.40
1.43
0.18
0.15
1.27
5.49
Mbaise
SiC
6.28
16.06
0.16
1.16
1.99
75.76
2.80
2.00
0.19
0.10
1.42
6.15
Obowo
SiC
5,23
15.67
0.73
1.31
2.50
82.07
3.56
2.31
0.27
0.13
1.40
7.84
Control
Mean
SCL
5.89
5.97
23.74
12.08
0.54
0.53
1.98
1.25
3.41
2.12
84.60
77.91
4.29
2.92
3.72
1.91
1.15
0.21
0.40
0.13
1.51
1.36
10.79
6.49
pH= power of hydrogen, P= phosphorous, N= nitrogen, OC= organic carbon, OM= organic matter, BS= base saturation, Ca= calcium, Mg= magnesium, K= potassium, Na= sodium, Ea= exchangeable acidity, CEC= effective cation exchange-capacity.
Some factors affect the heavy metal levels Cd, Pb in the soil. pH affects the heavy metal mobility because when pH reduces it is acidic, and according to Alloway 1995, heavy metals are generally most mobile under acid polymer conditions.
In Table 5.0, the mean value of pH along Owerri-Umuahia highway is at 5.97, it is acidic. Although, the availability of nutrient elements like Nitrogen, Phosphorus, Potassium (NPK), Calcium, Mg, OC, ECEC can lead to heavy metals mobility and accumulation in the soils Steinman 2011, but the values in the Tables 1.1, 3.2, and 5.0 shows that the other physicochemical properties are all at moderate levels. This means the Ph is the only factor that lead to the heavy metals (Cd, Pb) accumulation. According to Raymond A. Wuana., 2008, when heavy metals are not caused by high level of nutrient elements in soil, it could be as a result of fumes from heavy duty vehicular movements. Heavy metals are toxic to plants, animals, and humans, also the heavy metals cause adverse health effects
The soils along the highway has Cadmium and Lead levels at high levels due to the steady and massive vehicular movements. Vehicular stress can cause heavy metal accumulation and also change the physicochemical characteristics of a road side soils.
CHAPTER FIVE
CONCLUSION AND SUMMARY AND RECOMMENDATIONS
5.1 CONCLUSION
Based on the research, the availability of these metals Cd and Pb in Owerri soils ranges from 2.25-2.35, and 20.5-19.0 respectively. At Mbaise, Cd and Pb ranges from 2.2-1.90 and 23.0-25.5, Obowo Cd and Pb ranges 2.2-1.85 and 30.5-19.0. The heavy metals Cd and Pb varied with horizontally spread along the various areas in Owerri-Umuahia highway with levels of the metals decreasing horizontally as the movement increases off the road. This simply means, they are not mobile elements. The increased in distant off the roadside decreased the spread of metals follows 0-15 ft, 15-30 ft, 30-45 ft to 45-60 ft horizontally. Although ,the physicochemical properties are only used to study their impact on Cd and Pb and the general soil fertility along the road. pH decrease affects the level of CEC to be low. Soils with low CEC can develop low K, Mg, Na, and other cations, according Brown and Lemon 2008, and CEC decrease is caused by acidifying N fertilizer, Nitrate leaching and Agricultural practices. OM is low in the study area, which means it will reduce the release of nutrients in available plant form Eg Nitrogen, Phosphorus etc.
Note: The result show high Cd and Pb levels at the edge of the roadside compare to control. Therefore, vehicular movement increase Cd and Pb content at 0-15 ft when compared to control. But the increase did not spread horizontally and did not show high level of Cd and Pb compare to control from 15-30ft to 45-60ft, this means that the element is not mobile. This was supported by many that opinioned with emission control systems in car automobile emissions, heavy metals are controlled.
5.2 RECOMMENDATIONS
Liming materials should be added to enhance decomposition and to degrade and neutralize the effect of Lead and Cadmium levels, because it improves the beneficial microbe populations in the soil solution by reducing P immobilization Fe and Al in acid soils.
Phyto extraction should be applied on the farmlands along this mobility road which involves growing plants (Hyper accumulators) that take up heavy metal contaminants from the soil at the edge of the road. These plants are heavy metal tolerant, and when harvested should be burnt and ashes carefully disposed.
I recommend that plant tissues are sampled to evaluate the uptake. Also, study should be done on 30-60 cm depth to check if these heavy metals can be subsoil accumulators. Farmers should grow plants and crops at least 20 feet off the edge of the road to avoid contaminating these levels of Cd and Pb
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APPENDIX
BULK DENSITY
Bulk density = mass of dry soil/volume of soil= Ms/Vt
Volume of soil= volume of cylinder= 2h
R= radius, H= height of cylinder
MOISTURE CONTENT
Θ =Mw/Ms
Mc = Mw/Ms X 100/1 or
ΘM = (Mt-Ms) Ms = Mt-1/Ms
Mc = (Mt/Ms-1) X 100/1
EFFECTIVE CATION EXCHANGE CAPACITY
CEC = Ca2+ + Mg2+
Exchangeable acidity = H+ +Al2+
Ca = calcium, Mg = magnesium, H= hydrogen, Al = aluminum
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