ABSTRACT
Pollutants from vehicular emissions can cause negative impact on air quality and the nutrients content of vegetables planted by the road side. This work assessed the impact of vehicular emissions on the proximate composition of roadside Amaranthushybridus and roadside Mangifera indica and the air quality of Zaria. The air pollutants analysed were particulate matter (PM), nitrogen dioxide (NO2), sulphur dioxide (SO2), carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbons (HCs). These pollutants were measured during morning peak, evening peak and off-peak traffic periods. Traffic count was carried out to determine the traffic density at all experimental sites (Rex Junction, PZ Junction, MTD Junction and Kwangila Fly-Over). All the experimental sites were at traffic hot-sports in Zaria. The proximate composition determined were moisture content, fat content, ash content, crude protein content, crude fibre content and carbohydrate content. All the pollutants from vehicular emissions except particulate matter showed high correlation with traffic density at all the experimental sites. The concentrations of all the pollutants at all the experimental sites were higher than the concentrations at the control site. There were also higher concentrations during traffic peak periods than during off-peak. At traffic peak periods, the highest average concentrations of PM (213.00 μg/m2) and CO2 (348.00 ppm) in the air of Zaria were below the Nigerian Ambient Air Quality Standard (NAAQS) limit of 250 μg/m2 and 600 ppm for PM and CO2 respectively. NO2, SO2 and CO average concentrations at traffic peak periods were within the NAAQS limit range of 0.04 – 0.06 ppm, 0.01 – 0.1 and 10 – 20 ppm for NO2, SO2 and CO respectively. The average concentration range of hydrocarbons (0.057 – 0.070 ppm) at traffic peak periods were higher than the NAAQS limit of 0.05 ppm but was below the 0.05 ppm standard limit at traffic off-peak period. This shows that all the air pollutants from vehicular emissions at the
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experimental sites in Zaria were either below or within the NAAQS limit except for HCs. The mean proximate composition determined for Amarathushybridus cultivated at each of the experimental sites was compared to the mean proximate composition of Amarathushybridus cultivated at the control site and there was no significant difference (P = 0.05) between the two, showing that vehicular emission did not have negative impact on the proximate composition of the roadside Amarathushybridus. The proximate compositions of the roadside Mangifera indica were higher than the ones obtained at the Control except for the ash content that was significantly higher (P = 0.05). For the Amarathushybridus, moisture content, fat content, and crude protein content showed high negative correlation with age, crude fibre content and carbohydrate content showed high positive correlation with age while ash content did not correlate with age.
TABLE OF CONTENTS
Title page ……………………………………………………………………………………………………………….. i
Declaration …………………………………………………………………………………………………………….. ii
Certification ………………………………………………………………………………………………………… iiiii
Dedication ……………………………………………………………………………………………………………. iiv
Acknowledgement ………………………………………………………………………………………………….. v
Abstract ………………………………………………………………………………………………………………… vi
Table of Contents …………………………………………………………………………………………………. viii
List of Tables ……………………………………………………………………………………………………….. xv
List of Figures ……………………………………………………………………………………………………… xvi
List of Plates ………………………………………………………………………………………………………. xvii
List of Appendices ……………………………………………………………………………………………… xviii
Abbreviations ……………………………………………………………………………………………………….. xx
CHAPTER ONE …………………………………………………………………………………………………….. 1
1.0 INTRODUCTION …………………………………………………………………………………………….. 1
1.2 Effect of Vehicular Emission on the Environment …………………………………………………. 3
1.3 Composition and Volume of Emission by Individual Vehicle …………………………………. 3
1.3.1 Fuel composition ……………………………………………………………………………………………. 4
1.3.2 Level of engine maintenance ……………………………………………………………………………. 4
1.3.3 Age of vehicle ………………………………………………………………………………………………… 4
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1.3.4 Engine temperature …………………………………………………………………………………………. 5
1.3.5 Nature of road geometry ………………………………………………………………………………….. 5
1.3.6 Types and size of vehicle …………………………………………………………………………………. 5
1.3.7 Speed stability ………………………………………………………………………………………………… 5
1.3.8 Engine operation cycle ……………………………………………………………………………………. 6
1.4 Vehicular Emission Pollutants …………………………………………………………………………….. 6
1.4.1 Carbon dioxide (CO2) ……………………………………………………………………………………… 6
1.4.2 Sulphur oxides (SOX)………………………………………………………………………………………. 7
1.4.3 Nitrogen oxides (NOx) ……………………………………………………………………………………. 7
1.4.5 Particulate matter (PM) ……………………………………………………………………………………. 8
1.4.6 Ground level ozone (O3) ………………………………………………………………………………….. 9
1.4.7 Hydrocarbons (HCs) ……………………………………………………………………………………….. 9
1.4.8 Heavy metals ……………………………………………………………………………………………….. 10
1.5 Effect of Vehicular Emissions on Plants …………………………………………………………….. 10
1.6 Systematic Approaches to Reducing Emissions from Vehicle ……………………………….. 11
1.6.1 Technical strategies ………………………………………………………………………………………. 12
1.6.2 Vehicle technology ……………………………………………………………………………………….. 12
1.6.3 Rate of change of technology in the vehicle fleet ………………………………………………. 13
1.6.4 Vehicle maintenance ……………………………………………………………………………………… 14
1.6.5 Fuel technology ……………………………………………………………………………………………. 14
1.6.6 Systemic strategies ………………………………………………………………………………………… 15
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1.6.7 Behavioural strategy ……………………………………………………………………………………… 15
1.6.8 Accessibility planning …………………………………………………………………………………… 17
1.8 Research Aim/Objectives …………………………………………………………………………………. 18
1.8.1 Objectives ……………………………………………………………………………………………………. 19
1.9 Justification …………………………………………………………………………………………………….. 20
1.10 Scope and Limitation ……………………………………………………………………………………… 21
1.11 Significance of the Research …………………………………………………………………………… 21
1.12 The Study Area ……………………………………………………………………………………………… 22
1.13 Amaranthus hybridus ……………………………………………………………………………………… 22
1.14 Mangifera indica …………………………………………………………………………………………… 23
CHAPTER TWO ………………………………………………………………………………………………….. 26
2.0 LITERATURE REVIEW …………………………………………………………………………………. 26
2.1 Impact of Vehicular Emissions on the Level of Heavy Metals in …………………………… 26
2.2 Impact of Vehicular Emissions on Air Quality ……………………………………………………. 32
2.3 Impact of Vehicular Emissions on Plants ……………………………………………………………. 34
2.4 Effect of Fuel Type on Quality and Volume of Vehicular Emissions ……………………… 37
2.5 Effect of Time and Seasons on the Quality and Volume of Vehicular Emissions …….. 38
2.6 Effect of Vehicular Emissions on Health ……………………………………………………………. 38
CHAPTER THREE ………………………………………………………………………………………………. 40
3.0 EXPERIMENTAL METHODS ………………………………………………………………………… 40
3.1 Reagents …………………………………………………………………………………………………………. 40
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3.2 Preparation of Solutions …………………………………………………………………………………… 40
3.2.1 Sulphuric acid (0.023 M) ……………………………………………………………………………….. 40
3.2.2 Hydrochloric acid (0.10 M) ……………………………………………………………………………. 40
3.2.4 Sodium hydroxide (40.00 % w/v) ……………………………………………………………………. 41
3.2.5 Boric acid (4.00 % w/v) …………………………………………………………………………………. 41
3.3 Sampling Sites ………………………………………………………………………………………………… 41
3.4 Cultivation of Amaranthus Hybridus………………………………………………………………….. 45
3.5 Traffic Count ………………………………………………………………………………………………….. 45
3.6 Measurement of Growth Rate of the Amaranthus hybridus …………………………………… 45
3.7 Measurement of Air Pollutants from Vehicular Emission …………………………………….. 46
3.8 Sample Collection ……………………………………………………………………………………………. 46
3.8.1 Amaranthus hybridus sample collection …………………………………………………………… 46
3.8.2 Mangifera indica sample collection ………………………………………………………………… 47
3.9 Preparation of Sample ………………………………………………………………………………………. 47
3.10 Determination of Proximate Composition …………………………………………………………. 47
3.10.1 Determination of moisture content ………………………………………………………………… 48
3.10.2 Determination of ash content ………………………………………………………………………… 48
3.10.3 Determination of fat content …………………………………………………………………………. 48
3.10.4 Determination of crude fibre ………………………………………………………………………… 49
3.10.5 Determination of crude protein (Kjeldahl Method, A.O.A.C, 1980) ………………….. 50
3.10.6 Determination of carbohydrate (nitrogen free extract NFE) ……………………………… 51
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CHAPTER FOUR ………………………………………………………………………………………………… 52
4.0 RESULTS ………………………………………………………………………………………………………. 52
4.1 Concentration of Air Pollutants from Vehicular Emissions …………………………………… 52
4.3 Correlation analysis for Traffic Density with Air Pollutants ………………………………….. 58
4.4 Average Proximate Composition ……………………………………………………………………….. 60
4.5 Comparing the Proximate Composition of Amaranthus hybridus to that of Mangifera indica….……………………………………………………………………62
4.6 Comparing the Mean Proximate Composition at Control to those at Experimental Sites ……………………………………………………………………………………………………………………… 63
4.7 Proximate Composition as Age Increases in Weeks …………………………………………….. 64
4.8: Relationship between Age and Proximate Composition ………………………………………. 65
4.9 Growth Rate of the Amaranthus hybridus …………………………………………………………… 65
4.10: Comparing the Growth Rate at Control with that at Experimental sites for
Amaranthus hybridus………………………………………………………………….……..66
CHAPTER FIVE ………………………………………………………………………………………………….. 67
5.0 DISCUSSION …………………………………………………………………………………………………. 67
5.1 Impact of Vehicular emission on Air Quality ………………………………………………………. 67
5.1.1 Particulate matter (PM) ………………………………………………………………………………….. 68
5.1.2 Nitrogen dioxide (NO2) …………………………………………………………………………………. 69
5.1.3 Sulphur dioxide (SO2)……………………………………………………………………………………. 70
5.1.4 Carbon monoxide (CO) …………………………………………………………………………………. 71
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5.1.5 Carbon dioxide (CO2) ……………………………………………………………………………………. 72
5.1.6 Hydrocarbons (HCs) ……………………………………………………………………………………… 74
5.2 Traffic Density ………………………………………………………………………………………………… 74
5.2.1 Traffic count for individual class of vehicles ……………………………………………………. 75
5.2.2 Total Average traffic density at each experimental site ……………………………………… 76
5.3 Impact of Traffic Density on Air Pollutants Concentration …………………………………… 77
5.4 Proximate composition …………………………………………………………………………………….. 78
5.4.1 Proximate composition of Amaranthus hybridus ………………………………………………. 78
5.4.2 Proximate composition of Mangifera indica …………………………………………………….. 81
5.5 Proximate Composition of Amaranthus hybridus compared to that of Mangifera indica ……………………………………………………………………………………………………………………… 83
5.6 Impact of Vehicular Emissions on Proximate Composition …………………………………… 84
5.6.1 Impact on proximate composition of Amaranthus hybridus ……………………………….. 84
5.6.2 Impact on proximate composition of Mangifera indica ……………………………………… 85
5.7 Proximate Composition of Amaranthus hybridus as Age increases in Weeks ………….. 87
5.8 Growth Rate of Amaranthus hybridus ………………………………………………………………… 88
5.9 Impact of Vehicular Emission on the Growth Rate of Amaranthus hybridus …………… 89
CHAPTER SIX …………………………………………………………………………………………………….. 91
6.0 SUMMARY CONCLUSION AND RECOMMENDATIONS………………………………. 91
6.1 Summary ………………………………………………………………………………………………………… 91
6.2 Conclusion ……………………………………………………………………………………………………… 94
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6.3 Recommendations ……………………………………………………………………………………………. 95
REFERENCES …………………………………………………………………………………………………….. 96
APPENDICES ……………………………………………………………………………………………………. 103
CHAPTER ONE
1.0 INTRODUCTION
The emission of pollutants by vehicles into the atmosphere as a result of traffic density emanating from high fleet growth, increased population, increased urbanization and economic improvement have caused serious damage to the environment. These pollutants affect plants, animals and man and by extension crops cultivated on places exposed to this emissions especially those areas close to road sides. The negative effects of vehicular emission on roadside crops have been illustrated by Naveed et al., (2010). The main products of the combustion of motor fuels are carbon dioxide and water but inefficiencies and high temperature inherent in engine operation encourages the production of many other pollutants of varying effect. 1.1 Concept of Vehicular Emission and Systemic Effect
Vehicular emission leads to the accumulation of both primary and secondary pollutants in the atmosphere. The primary pollutants from vehicular emission includes carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOx), sulphur oxides (SOx), hydrocarbons (HCs), heavy metals and particulate matter (PM). These primary pollutants usher in secondary pollutants such as smog, fog, ground level ozone (O3) and peroxyacetylnitrate (PAN) which arise from the chemical reaction of primary pollutants possibly involving the natural component of the atmosphere especially water and oxygen. Road vehicle emission comes from both light duty vehicle (gasoline powered vehicles) and heavy duty vehicles (diesel powered), the light duty vehicles emit more of hydrocarbons otherwise known as volatile organic compounds (VOCS), CO and NOx whereas the heavy-duty vehicles emit more of NOx and particulate matter PM (Sawyer, 2010).
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Health effect of vehicular emission pollutants can cause serious health problem to people living in such environments. High level of carbon monoxide can cause harmful health effect by reducing oxygen delivery to the body organs and tissues. When CO enters the blood system, it binds with the haemoglobin since haemoglobin has more affinity for CO than O2; hence oxygen delivery to the body will be hindered thus depriving the body of an essential for life. The health threat from ambient CO is most serious for those having cardiovascular disease; high level of CO can lead to impairment of vision, headache and nausea (Sabo, 2009). Ground level ozone (O3) can reduce lung function and scarring of lung tissue, it can aggravate asthma and other respiratory diseases. SO2 causes a wide variety of health problems especially in people with lung disease, at high concentration in the ambient air; SO2 can cause breathing difficulty for people with asthma who are active outdoors. Nitrogen dioxide (NO2) can irritate the lung and lower the resistance to respiratory infections. Particulate matter can cause lung infection when inhaled in large amount leading to pre-mature death (Sabo, 2009). Lead as a pollutant from vehicular emission can affect learning ability (Sabo, 2009). This negative effect in learning is caused by the fact that lead can affect many organs including the brain causing neurodevelopment problems. Evidence from Cross-sectional and prospective studies of populations with lead levels generally below 25ug/decilitre in blood relates to decrement in intelligence quotient (Lon, 2003).
Other heavy metals also cause health problems, for instance cadmium can damage the kidney, liver and brain,m chromium is toxic to body tissues with high tendency of
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causing ulceration of the skin, nickel creates respiratory problem while zinc fume have corrosive effect on skin and can cause irritation and damage mucous membrane (Dara, 2008). 1.2 Effect of Vehicular Emission on the Environment Pollutants from vehicular emission bring adverse effect to the environment. Pollutants like NO2 play a major role in the atmospheric reactions that produce ground level ozone. It also contributes to the formation of acid rain. SO2 reacts with other chemicals in the atmosphere to form secondary pollutants such as sulphuric acid and sulphates. These sulphate particles reduce visibility, SO2 also form acid rain, fog, snow or dry particles, it also accelerates the decay of building materials, and it reduces aesthetic value of monuments, Statues and Sculptures which are part of the environment. This acid rain from SO2 and NO2 changes the Composition of our soil and also make our water acidic and unsuitable for aquatic life (Dara, 2008).
Particulate matter creates visibility impairment as a result that fine particles scatter and absorb light creating a haze that limit the distance we can see and that degrade the colour, clarity and contrast of view. Carbon monoxide emitted by vehicles contributes to global warming after being oxidized to CO2 which is a greenhouse gas. Vehicles also release CO2 directly into the atmosphere during complete combustion (Dara, 2008). 1.3 Composition and Volume of Emission by Individual Vehicle The volume and composition of emission from individual vehicle is determined by many factors. These factors are:
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1.3.1 Fuel composition
The amount of sulphur, metals, benzene, toluene and other components in fuel used by vehicles has a significant influence on the composition and concentration of those pollutants in the emissions (Faizet al., 1996). 1.3.2 Level of engine maintenance
Inadequate maintenance, poorly adjusted timing, dirty air cleaners, dirty and contaminated oil, blocked air filter, malfunctioning fuel supply system and wrong tempering with pollution control devices can increase emission, primarily through incomplete combustion (Tsunokowa and Hoban, 1997). 1.3.3 Age of vehicle Old vehicles lack the modern emission control technology mounted on vehicles today, and since there is close relationship between the age of automobile engine and exhaust technology which determines the quality of exhaust emission, those vehicles with old engines produce higher level of emissions than do newer fleets of the same size. As illustrated by Ndokeet al., (2006), vehicular emission pollutant like CO2 was more in the atmosphere of some part of Kaduna than in Abuja even when more number of vehicle were being used in Abuja, this could be as a result of the quality of vehicles used in Abuja. In the future,the Abuja situation mentioned here could also be obtainable in Zaria if newer and good quality vehicles are used on its roads through proper regulation and enforcement.
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1.3.4 Engine temperature
The fuel burning efficiency of cold engines are very low and the catalytic converters on gasoline engines do not function at all until normal operating temperature is attained hence this will lead to high volume of more toxic emission since at low engine temperature, the catalytic converters will not be able to convert vehicular emissions to more environmentally friendly forms, for instance, the conversion of CO to CO2 which is less toxic in the environment (Tsunokawa and Hoban, 1997). 1.3.5 Nature of road geometry
Automobile engines produce greater emissions while decelerating, accelerating and going up high levels. Roads that are full of up, and down profile will surely encourage high vehicular emissions (Tsunokowa and Hoban, 1997). This is because as the vehicle clutch and brake are applied during deceleration and acceleration more fuel goes into the engine combustion chamber which will burn more giving rise to higher emissions. 1.3.6 Types and size of vehicle
Vehicles with large engines emit more pollutants than vehicles with small engines. For instance big diesel engines produce large amount of NOx and particulate matter while the gasoline engines which are smaller and less powerful produce more of CO and HCs (Black, 2010). 1.3.7 Speed stability
Most Vehicles display fuel burning efficiency at a speed between 80-100km/h steady speed (Tsonokawa and Hoban, 1997). Unstable Speed less than this will definitely lead to engine inefficiency thereby releasing more emission.
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Vehicle kilometres travelled is also a factor affecting vehicle emission, as kilometres travelled increases, so the increase in emission (Abbaspour and Soltaninejad, 2004). 1.3.8 Engine operation cycle
Apart from the type of engine as per the type of fuel used (gasoline, alcohol or gas fuel engines), the numbers of cycle of operation of the engine have a direct influence on the quality and quantity of pollutants released into the atmosphere. The 4-Stroke Cycle engines are more efficient in burning than the 2-Stroke engines making the 4- Stroke engines more environmentally friendly than the 2-Stroke engines (Aminnurul, 2009) 1.4 Vehicular Emission Pollutants
The vehicular emission pollutants that have constituted nuisance to man and the environment include CO2, SOX, NOX, CO, PM, HCs and heavy metals among others. 1.4.1 Carbon dioxide (CO2) This is one of the greenhouse gases. One of the most important human impacts on our environment is the sharp increase in atmospheric CO2 caused by the use of fossil fuel. CO2 is a colourless gas. Its density at 25oC is 1.98 kgm-3 about 1.5 times that of air. It is a linear shape molecule (O=C=O) containing two double bonds having no electrical dipole as it is fully oxidized and it is a non-flammable gas.
The basic process that brings about the emission of CO2 by automobiles is through the combustion of fossil fuel which involves the reaction of alkanes with oxygen to form CO2, water and heat. When there is more complete combustion in the combustion chambers of automobile engine much CO2 is produced and released as emission into the
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atmosphere. The amount of CO2 produced is directly related to the quantity of fuel consumed (Tzirakis et al., 2006)
1.4.2 Sulphur oxides (SOX)
These are produced during combustion process of fuel which usually contains sulphur as impurities. Sulphur (IV) oxide and Sulphur (VI) oxide are the two prominent sulphur oxides associated with vehicular emission. Sulphur (VI) oxide is a colourless toxic gas with characteristic irritating odour. Oxidation of SO2 in the atmosphere produces SO3 which is the precursor of sulphuric acid formation in the presence of NOx, O3 and HCs as catalyst(Dara, 2008). This is responsible for the sulphate particulate matter emission. Since sulphur present in fuel is either released as a Sulphate particle which is an important component of particulate matter or as gaseous Pollutant (Mishra, 2008).
1.4.3 Nitrogen oxides (NOx)
Most of the NOx in vehicle emissions are in the form of NO, which is a by-product of fuel combustion under conditions of extreme heat and pressure which is typical of combustion chambers. Once released from the tailpipe (exhaust), it is oxidized to NO2 which in conjunction with SO2 plays a major role in the formation of acids in the atmosphere. NOx also react with hydrocarbons (HCs) to produce photochemical smog in the atmosphere. Apart from NO other forms of Nitrogen Oxides could also be produced in the combustion chamber of automobile engines. Those other forms include N2O and NO2. NO is extremely reactive. It destroys resistance to respiratory infection. NOx products are increased when an engine runs at it most efficient (i.e. hottest) part of the cycle (Mishra, 2008).
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1.4.4 Carbon monoxide (CO) This is a colourless, odourless, non-irritating but very poisonous gas. It is a by-product of incomplete combustion of fuel. Vehicular exhaust emission is a major source of carbon monoxide especially from substandard vehicles. In the United State of America, CO is emitted by engines more than any other pollutants from vehicular emissions because according to Ronni (2012), CO has 77% of the total emissions from automobile emission used for land transport in USA, other pollutants stood at: NOx 58.37%, VOCs 35.5%, NH3 8.1%, PM10 2.67%, PM2.5 9% and SO2 4.5%. This data shows that incomplete combustion that leads to CO emission is the major player in vehicular emission.
1.4.5 Particulate matter (PM)
Particulate matter (PM) represent a broad class of chemically and physically diverse substances that exist as discrete particles (liquid droplet or solids) over a wide range of sizes. Particle matter may be emitted directly into the atmosphere or may be formed by transformation of gaseous emissions such as sulphur dioxide, nitrogen oxides and volatile organic compounds (VOCs). Some particulate matter occurs naturally originating from volcanoes, dust storm, forest and grass land fires, and sea spray. Particulate matter is a core emission by automobile especially diesel engine vehicles. Vehicular emission is connected to two types of particulate matter, the fine particulate matter (PM2.5) and the coarse particular (PM10). PM2.5 consist of particles less than one-tenth the diameter of human hair and possess the most serious threat to human health (Ronni, 2012). The size of particle is directly linked to their potential for causing health problems.
Particles that are ten micrometre (PM10) in diameter generally pass through the nose into the lungs. Once inhaled these particles can affect the health and lungs and cause serious health effect. Particles less than 2.5 micrometres in diameter are termed “fine particle or
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PM2.5 as mentioned before, they are so small that they can be inhaled deeper into the lungs than the PM10, hence it causes more health problem than PM10 (Walsh, 2001).
1.4.6 Ground level ozone (O3)
Ozone is an extremely reactive gas unlike other gaseous pollutants associated with vehicular emissions; O3 is not directly emitted into the atmosphere. Instead, ground level ozone is formed when vehicular emission like NOx chemically reacts with volatile organic compounds (VOCs) through series of complicated chemical reactions in the presence of strong sunshine (Ultra violet light) as reported by (Tsunokawa and Hoban, 1997; Sabo, 2009).
1.4.7 Hydrocarbons (HCs)
Hydrocarbons also known as volatile organic compounds (VOCs) are made up of unburned or partially burned fuel and are the major contributors to urban smog. Hydrocarbons are volatile organic compounds which includes benzene, toluene, naphthalene etc, we should bear in mind that vehicular emission is divided into two categories; exhaust (tailpipe) emission and evaporative (vapour) emissions (Agyemang –Bonsuet al., 2010). It is the evaporative that gives rise to VOCs. This evaporative emission includes running losses which occurs when the vehicle is operating in a hot stabilized mode; hot soak emission resulting from fuel evaporation from still hot engine at the end of the trip; diurnal emissions; which result from evaporation of fuel from gasoline tank whether the vehicle is driven or in steady state (Agyemang- Bonsuet al., 2010). All these emissions from evaporation of fuel especially gasoline contribute to the concentration of volatile organic compounds in our atmosphere.
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1.4.8 Heavy metals
Heavy metal pollutants are also associated with vehicular emissions. These metals range from cadmium, zinc, lead, chromium, nickel, and many others. There has been evidence of heavy metal pollution on roadside as a result of vehicular emission (okunolaet al., 2011). The most abundant heavy metal associated with vehicular emission before now was lead metal. Because it was used as additive to prevent engine knock in automobile fuel which the lead compound known as tetra-ethyl lead (TEL) was used. But with oxygenated blending technology of fuel today, lead additive is no more used, hence reducing the amount of lead emission to almost zero. There has been some evidence of lead and other metal pollution from automobile emission in Nigeria many years ago (Ndiokwere, 1984). But a recent study has also showed that lead pollution still relates to vehicular emission (Naveedet al., 2010). This might arise from the use of adulterated or fuel that is not well refined common among underdeveloped nations.
1.5 Effect of Vehicular Emissions on Plants
Vehicular emissions have some effect on plants especially those plants on the road side which are exposed to it. Some pollutants like the photochemical oxidants (ozone and peroxyacetyl nitrate) which are formed by sunlight acting on products of fuel combustion particularly the nitrogen dioxide and hydrocarbons that come from vehicle exhausts are very dangerous to plants since plant leaves are sensitive to them (Rejini and Janardhanan, 1989). Ozone causes many irregular lesions called fleck or stipple on the upper surface of broad – leaves plants (Mishra, 2008). Yellowing of leaves also occurs (chlorosis). Peroxyacetyl nitrate (PAN) as well as ozone cause collapse of tissues, silvering, glazing
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or bronzing occurring usually on the lower leaf surface with more effect on younger leaves (Butz, 2012). Excessive NO2 in the atmosphere damages leaves of plants, reduce photosynthetic activity and also causes chlorosis (Durraniet al., 2004). SO2 can inhibit or promote stomata closure depending on its concentration coupled with other pollutants in the environment (Viskarriet al., 2000).These stomata response create variation in the uptake of pollutants by plants. SO2 as well as other pollutants changes the morphology, physiology and biochemistry of sensitive plants. It can also cause bleaching of leave pigments due to conversion of chlorophyll to phacophytin and this reduces plant productivity. NOx, VOCs and particulate matter released by vehicles enter the plant through the stomata in the leaves and damage them. These pollutants may abrade theepicuticular wax and thereby reducingcuticular resistance to air and to gas diffusion and also affectingstomatal response (Babu, 1993). NO2 suppresses plants growth without marking the leaves when concentration is low (Butz, 2012). These pollutants interfere with plants normal respiration leading to the destruction of chlorophyll and the reduction inphotosynthetic activity. Other damages to plants by vehicular emission range from reduction in growth rate, pale look, reduction in yield to complete death (Uchegbu, 1998).
1.6 Systematic Approaches to Reducing Emissions from Vehicle
The development of a strategy involves the selection of a logical and rational set of measures which, when implemented, will help to reduce vehicular emissions. These measures can be technology-oriented, aimed at the vehicles and fuels used and maintenance practices within transport system, or they can be behavioural, seeking to reduce (or prevent increases in) the amount of activity of the most polluting vehicles. They may also focus on systemic aspects of the transport system which is the ways in
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which the transport network influences either the number of vehicle used or the emission intensity of individual vehicles. It should be borne in mind that emission control strategies should be determined in the wider context of improving outdoor air quality in traffic environment. This involves important economic technical analysis in the context of an air quality management programme. These programmes, such as the World Bank’s Air Quality Management System, are useful in identifying the most efficient use of scarce resources to address an air quality problem. However, the process of carrying out such an assessment tends to be difficult (Gorham, 2002).
1.6.1 Technical strategies
Technical approaches aims at reducing the emissions produced by road vehicles by intervening with the quality of vehicles being used and the fuels they are burning. By definition, these approaches address per unit emissions rather than the amount of activity causing the emissions. An exclusively technological approach may be insufficient to address the growth in emissions, for a number of reasons. First, growth in activity continuously puts pressure on technology gains. Secondly, technological improvements can intensify the growth in activity; thirdly an exclusively technological approach to addressing the problem of emissions may result in significant over-investment in technology compared with a socially optimum solution like introduction and implementation of tax (Gorham, 2002).
1.6.2 Vehicle technology
These strategies may involve improvements in conventional technologies already in the system, and acceptable for use, such as improvements in engine and fuel systems,
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changes and improvements to transmission systems (to increase efficiency and reduce CO2 emissions), treatment for fuel supply and crankcase systems (to reduce evaporative emissions), or improvements to overall vehicle or tyre design to reduce friction. Technological improvements might also involve the adoption and use of alternative fuel or alternative propulsion vehicles. In developing countries like Nigeria, the most commonly discussed alternative vehicle fuel strategies include compressed natural gas (CNG), liquefied petroleum gas (LPG), alcohol-based fuels and biodiesel, but Nigeria lacks technical know-how for actual implementation. Other alternative fuels showing potential long-term promise in the reduction of vehicular emission in the transport sector include hydrogen fuel and various synthetic fuels for use in compression-ignition engines (Aminurul, 2009).
1.6.3 Rate of change of technology in the vehicle fleet
In the under developed world such as our country Nigeria, the adoption or response to new technology is far too slow if not impossible. There has been an extensive review of appropriate technologies in the emissions-reduction literature and at conferences but no adequate implementation. The rate of change is more important than the technology itself for reducing transport emissions, particularly for fleets where baseline emission control mechanisms are minimal or non-existent. In assessing any technology, therefore, the analysis of technological options needs to move beyond a narrow assessment of the relative emissions and energy consumption capabilities of each technology; rather, the analysis should focus on how rapidly the different technologies can be deployed and widely used in the fleet. Policy on rate of change of technology should contain strategies which allows older vehicles to benefit from more recent technology, like in the case of
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marine vehicles, where dedicated ballast tank is assigned on board to old tankers that did not have clean ballast tank when built in effort to fight marine pollution from ships.
1.6.4 Vehicle maintenance
Vehicle maintenance is a very important aspect of any technical strategy to reduce per kilometre emissions of pollutants from each vehicle because we have more number of old vehicles than new in any system, hence thorough maintenance of these vehicles should be carried out. Effective strategies focusing on vehicle maintenance have three key elements: (i) emissions testing, which provides a mechanism to identify vehicles that are not performing according to regulations standard, (ii) driver and fleet manager education and training, which help to facilitate the acceptance of emissions testing components, (iii) a programme of on-going product liability, for either manufacturers or importers, which also helps to ensure better maintenance by creating a market incentive for suppliers to follow up on their products.
1.6.5 Fuel technology
Research and improvement to the specifications of fuels or composition of fuel are as important as improvements to vehicles. Fuel improvements can affect emissions in three ways. First, changes to fuel content can directly bring about a reduction in emissions of certain pollutants, such as lead, sulphates, oxides of sulphur (SOx), or volatile organic compounds (VOCs). Unlike changes to vehicle technology, the effects of these types of fuel content changes are immediate. Secondly, changes in fuel content can facilitate the use of certain exhaust after-treatment technologies–particularly those using platinum -based catalysts–which would not have been usable before. Thirdly, the costs of these improvements are passed on to the consumer but, unlike the costs for technical
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improvements to vehicles, these costs are passed on as variable rather than fixed costs which makes it acceptable without people feeling much impact (Gorham, 2002).
1.6.6 Systemic strategies
Systemic approaches to air quality improvement in connection to vehicular emission is also very important in emission reduction, this strategy tries to adjust driving conditions so as to enable vehicles to operate in the least emissions-intensive manner possible. Such a goal can involve increasing average speeds to an optimal level (ordinarily between 65 and 90 kilometres per hour for most pollutants, including CO2), as this favours engine efficiency (Abbaspour and Soltanninejad, 2004). To achieve this speed, systematic approach such as building good roads and modern round-about should be on ground. Systematic approach could also include good traffic management strategies such as proper road marking and creation of dedicated lane for mass transit vehicles to reduce hold- up on the road, as is obtainable in Lagos bus rapid transport (BRT) in Nigeria.
1.6.7 Behavioural strategy
Behavioural approaches seek to reduce the amount of vehicular travel undertaken, either by substituting alternative modes, changing the structure of accessibility for large segments of society, so as to reduce the need to travel, for instance spreading social amenities and industries to provide employment to the rural people instead of every one coming to look for employment in the urban centres. Behavioural strategies are most effective when focused on the future adaptive behaviour of travellers rather than on current patterns. Strategies involving mode shifts usually focus on displacing or reducing car, taxi, or micro-bus trips with either conventional public transport or non-motorised modes. The – none motorised mode could be the encouragement for the use of bicycles.
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Several conditions affect how successful this strategy can be. The travel on the alternative mode must be a shift (substitution), and not a new trip (addition). Policy must support the separation of vehicle ownership growth rates from vehicle use growth rates. The link between car ownership and use is not unbreakable, and careful attention to pricing can reinforce this. This could be achieved by imposing higher tax on private vehicle usage within the town to discourage private car owners, this changes their behaviour and ideologies. The synergies created by combinations of measures are significantly more effective than any of the measures on their own. The behaviour of travellers should be fine-tuned towards public transport system as emission control strategy, because one bus under mass transit scheme could transport the number of people ten cars could, thereby reducing the number of vehicles on our roads drastically and in turn checks vehicular emission possibly because common sense will let one know that this one mass transit bus cannot burn or consume the quantity of fuel as the ten cars in question; suggesting a decrease in emission bearing in mind that the quantity of emissions is proportional to the amount of fuel burned (Enemari, 2001) and fuel consumption is also a function of vehicle density (Odhiamboet al., 2010). A primary goal of a public transport intervention involves the targeting of service improvements and enhancements in corridors and for socio-economic groups that would otherwise be expected to adopt widespread car use. Since these groups tend to be more priced than time-sensitive, service enhancements are more effective than fare restraint or fare subsidies. For many jurisdictions, this strategy may conflict with another fundamental goal of public transport policy: providing low-cost transport services to the poor. Secondary air quality goals would involve reducing the number of vehicles required to service a given market for a given level of service reliability, and improving the cash flow of vehicle operators to enable them invest in better equipment. These goals all point
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to the need to commercialise public transport service delivery and establish functioning regulatory frameworks. An effective non-motorised transport (NMT) strategy for developing countries needs to be oriented towards the gradual substitution of non-motorized transport system (Gorham, 2002).
1.6.8 Accessibility planning
Transport is a demand derived from the need for access. By better addressing directly the accessibility needs of populations, the need for transportation might be reduced. This could involve better attention to land-use planning and urban development, or better application of telecommunications technology as a strategic substitute for particular trips. A number of best-practice principles in land-use/urban planning to improve accessibility can be identified as follows:(i)recognising that the designation of primary rights of way and movement corridors will have an impact on location, land-use and building-pattern decisions for decades, and take this impact into account in the early planning stages· (ii) recognising the cumulative impact of land-use and transport decisions. (iii) Correcting pricing distortions in the transportation system before they are “capitalised” into land through particular urban forms or densities. (iv) Ensuring the inclusion of full infrastructural costs in land prices through the development process. Increase the liquidity and transparency of real estate to allow markets to respond adequately and fairly to public policy signals and accelerate demand-driven changes in land use. (v) Avoiding inappropriate regulations and excessive reliance on regulatory measures to influence land use without commensurate, compatible and supportive infrastructural investments and transportation policy, but enforce appropriately scaled and applied regulations with heartiness. (vi) Fostering amenity and access in urban design as counterweights to the demand for space as incomes grow. (Vii) Experimenting on a small scale with new or
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innovative ideas shifting the costs associated with travel. Innovations in a number of transport delivery options in developed countries–including car-sharing, road or congestion pricing, variable-priced insurance, cash-out of free parking are coalescing around an increasingly recognized element of transport pricing: shifting the overall lifetime cost burden associated with auto mobility from fixed to variable costs (Gorham, 2002). A policy goal of varying costs associated with motorisation can help better to align the costs and the benefits of individual trips, leading to a more efficient allocation of trip-making, chaining (combining or sequencing trips throughout the day), and mode choice (Gorham, 2002) 1.7 Research Problem There is uncertainty arising from whether the quality of road side vegetables could be as good as those cultivated far away in terms of nutritional values. This has created doubt in the minds of concerned people making them to be curious about knowing which level of air pollutant could course a change in the nutritional value of road side vegetable crops and whether the concentration of these pollutants from vehicular emission in Zaria metropolis have reached that level.
1.8 Research Aim/Objectives
This research aimed at determining the impact of vehicular emissions on the proximate composition of roadside Amaranthus hybridus (African spinach or green amaranth), roadside Mangifera indica(Mango) and air quality in Zaria. It also aimed at: -establishing whether vehicular emission could affect the proximate composition of Amaranthus
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hybridus and Mangifera indica, determining whether the air quality in Zaria has been reduced by vehicular emissions below the recommended standard and to make recommendations on how any possible negative effect on the crops and air quality could be handled.
1.8.1 Objectives
The aim of this research was achieved through the following objectives:-
1 Determination of the pollutants loads [Carbon monoxide (CO), Carbon dioxide (CO2), Nitrogen dioxide (NO2), Sulphur dioxide (SO2), Hydrocarbons (HCs) and Particulate matter ( PM)] in Zaria atmosphere at strategic points with high traffic density.
2 Determination of these pollutants at peak and off-peak periods.
3 Carrying out traffic count in order to determine the traffic density at chosen sampling sites.
4 Correlating the amount of pollutants with traffic density.
5 Determination of proximate composition of the Amaranthus hybridus.
6 Determination of the impact of these pollutants on the proximate composition of road side Amaranthus hybridus.
7 Determination of the impact of these pollutants on the growth rate of the roadside Amaranthus hybridus.
8 Comparing the impact of vehicular emission on air quality and the roadside crops at experimental sites with control site.
9 Comparing the proximate composition of Amaranthus hybridus to that of a perennial crop (Mangifera indica).
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10 Comparing the concentration of these pollutants with the Nigerian Ambient Air Quality Standard (NAAQS) limit.
1.9 Justification The daily increase in number of vehicles in Zaria metropolis has certainly increased the volume of vehicular emissions in Zaria environment and research to determine the amount of these pollutants in the atmosphere and their impact on roadside Amaranthus hybridus have not been adequate since it is not readily available in literature. Based on this, there is need for a research work such as this in order to determine the impact of these emissions on the atmosphere and roadside Amaranthushybridus within Zaria metropolis to compliment the few existing data bearing in mind that any negative impact on crops may have direct influence on the nutritional need of man who depends on these crops. Available evidence shows that vehicular emissions have adverse effect on crops and air quality and this have been illustrated by some researchers, for instance, Lowry et al.,(1951) showed that pollutants from vehicular emission can reduce plant protein content. A reduction in the amount of plant proteins, chlorophyll pigments and adverse effect on morphology were also shown by Andrew et al., (2007) while the negative impact of vehicular emissions on air quality was shown by Utang and Peterside (2011). Based on these, there is a need to further determine the impact of vehicular emission in Zaria atmosphere to ascertain the level of pollutants coming out from the tailpipe and its impact on a major vegetable the Amaranthus hybridus widely consumed in Zaria metropolis.
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1.10 Scope and Limitation
Four traffic hotspots were used as experimental points and another point 250 metres away from the nearest major road was used as control point. Only one kind of vegetable crop, the Amaranthus hybridus was cultivated at all sampling sites. The impact of vehicular emissions was determined considering only the effect on air quality and proximate composition (moisture content, ash content, fat content, crude fibre content, crude protein content and carbohydrate content) of the crop. Air quality was measured considering only the gaseous pollutants [carbon monoxide (CO), carbon dioxide (CO2), nitrogen dioxide (NO2), sulphur dioxide (SO2), hydrocarbon (HCS)and particulate matter (PM)] and they were all determined at each sampling points. 1.11 Significance of the Research Research carried out on vehicular emissions shows that vehicular emissions can cause adverse health effect on plants, reduce crop quality, affect plant morphology and also have negative impact on air quality as reported by Andrew et al., 2007 and Dara, 2008. Based on this, it becomes appropriate that a work of this nature is needed to establish whether there could be negative impact from vehicular emissions on air quality and the crops under study so as to help regulatory bodies to reduce the volume of emissions in Zaria on time by enforcing the laws which help to check traffic emissions. Result obtained from this research will contribute to knowledge and help other researchers that will be interested in this area of research.
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1.12 The Study Area
The study area, Zaria is in Kaduna State of the Federal Republic of Nigeria. It is the second largest city in kaduna state, it is located between longitude 7o 36’ to 7o 42’E and latitude 11o 00’ to 11o 10’ N of the equator and found on the high plains of northern Nigeria, in sub-Saharan Africa (Uboguet al., 2011). Zaria metropolis contains two local government areas, Zaria and Sabon-Gari. The major drainage systems in Zaria metropolis are the River Galma which is a major tributary of River Kaduna having a drainage basin of about 6902 km2 area, the River Kubani, the River saye among others (Mortimore, 1970). It has two major soil types, the red laterite soil of northern Zaria and the heavier and more fertile blackish soil which occurs further south of the region (klinkenbera, 1970). The space economy of Zaria comprises of commercial, residential, educational, transportation, agricultural and industrial land use with the industrial activities presently dominated by small-scale informal sector (Uboguet al., 2011).
1.13 Amaranthus hybridus
Amaranthus hydridus according to Integrated Taxonomic Information System of North America is commonly known as green amaranth, smooth pigweed and smooth amaranth having the taxonomy serial number TSN20735. It is a member of the Amaranthaceae family. In Nigeria, it is generally and commonly called spinach although not of the same species with the real spinach plant (Spinacia oleracea). It is also known as green in southern part of Nigeria, alefo in northern part and effo in the west. An annual herbaceous plant of 1 – 6 feet (0.3 – 1.83 meters) high with petiole alternate light green leaves Akubugwoet al., (2007). Amaranthus hydridus is a leafy vegetable widely consumed in Nigeria especially in the north. It is probably the most widely occurring leafy vegetable in Africa (Mordi, 2007). Apart from being used as vegetable, it is also
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used as herbal medicine since it has medicinal values for the treatment of intestinal bleeding, diarrhea and excessive menstruation (Foster and Duke, 1990). Classification of Amaranthus hydridus Kingdom ——- Plantae Phylum ——— tracheophyta Class ———– magnoliopsida Order ———– Caryophyllates Family ———- Amaranthaceae Genius ———- Amaranthus Species ——— Amaranthus hybridus Source: Integrated taxonomic information system of North America (2013)
1.14 Mangifera indica
Mangifera indica according to Integrated Taxonomic Information System of North America is commonly known as mango having the taxonomy serial number TSN 28803. It is a member of the Anacardiaceae family. It originated from southern Asia, more precisely from India where it has been cultivated for more than 4,000 years from the Malay Islands (Sauer, 1993). Mangifera indica fruit is widely consumed in Nigeria and other part of the world. The fruit is a berry whose pulp is low in acid, rich in sugars and considerable quantities of Vitamins and Minerals (Alveset al., 2002). Classification of Mangifera indica Kingdom ——- Plantae Phylum ——— Magnoliophita Class ———– Magnoliatae Order ———– Sapindales Family ———- Anacardiaceae Genius ———- Mangifera Species ——— Mangifera indica Source: Integrated taxonomic information system of North America (2013)
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Plate I: Amaranthus hybridus plant showing seeds
Plate II: Amaranthus hybridus plant
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Plate III: Mangifera indica plant Plate IV:
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