Physicochemical and Heavy Metal Analysis of Soil Samples From Selected Rural and Urban Locations


The focus of this research is to investigate by chemical analysis and the physiochemical characteristics of soil samples from urban and rural areas in Abuja. Cities and urban processes have had dramatic but varying impacts on the physical and biochemical properties of soil, all of which affect the life-supporting services of soils. As developing countries continue to industrialize, soil pollutant contamination in their cities continues to increase to levels warranting immediate action. Five (5) soils samples each were obtained from both rural and urban areas in Abuja and subjected to both physical and chemical analysis. The soil characteristics to be analyzed will be properties such as particle size distribution, pH, C-content (%) and Moisture-content (%), the ratio of silt/clay and C/N, Organic Matter, Exchangeable acidity and basicity, as presence and level of heavy metal in soil samples. Physical properties were analyzed by putting the samples through routine laboratory analysis using specified reagents and equipment. Extracts of digested soil samples from both areas were analyzed using the Atomic Absorption Spectrophotometer for heavy metals. The findings of the research reveal that soil samples from both areas differs in their physical properties as mean values for soil pH, Moisture content and organic matter were 6.97+0.49, 2.23+0.67, 3.58+0.75 with SCL textural and 6.39+1.14, 2.85+3.37, 7.18+2.10 with both SL and SCL textural for rural and urban areas in Abuja respectively. The study was able to compare mean values of heavy metals for soils sampled from rural and urban areas, heavy metal presence was recorded, more for urban soil samples than for rural soil samples, both in the order; Fe>Zn>Pb>Cu>Cd. The concentration of Pb exceeded WHO limits for the Apo automobile site and Area 3 Motor Park, putting surrounding environment at risk of pollution. The findings of this research will expose the dangers posed to the soil by the rapid urbanization taking place in Nigeria and proffer suitable recommendations on how to save the soil from losing its mineral values and importance in the ecosystem.



1.1 Background to the Study

Soil is a naturally occurring body consisting of different layers known as soil horizons, which differ from the parent materials in their morphology, physical, chemical, and mineralogical characteristics (Stutz, et al 1986). Soil gives plants a place to sink their roots and anchor themselves. It is also a community with billions of organisms, and contains organic matter (decaying or decayed living things) as well as minerals (broken down rock). When it contains a partly decayed organic matter is called humus. Soil is composed of particles of broken rock that have been altered by chemical and environmental processes that include weathering and erosion (Manahan, 2017).

According to Chesworth (2007), “Soil differs from its parent rocks due to interactions between the lithosphere, hydrosphere, atmosphere and the biosphere” Only a very limited amount of information can be gained from looking at the soil surface. It will be necessary to evaluate a vertical cross-section of the soil; this is known as the soil profile, each soil type is distinguished by its profile, almost like a fingerprint. A soil profile is divided into a number of distinct layers, which are called horizons. Although we can use these horizons to identify many complicated subdivisions within the soil, a much simpler approach is to split the profile into topsoil, subsoil and parent material (Hanesch and Scholger, 2005).

Soil is a vital part of the natural environment and also plays a vital role to both the living and non-living things in the ecosystem and thus “it is just as important as plants, animals, rocks, landforms, lochs and rivers. It influences the distribution of plant species and provides a habitat for a wide range of organisms, as well as controls the flow of water and chemical substances between the atmosphere and the earth, and acts as both a source and store for gases (like oxygen and carbon dioxide) in the atmosphere” (Asadi et al., 2017).

Soils not only reflect natural processes but also record human activities both at present and in the past. They are therefore part of our cultural heritage. The modification of soils for agriculture and the burial of archaeological remain good examples of soil use as described above. According to Mishra et al. (2016), soil together with the plant and animal life it supports, the rock on which it develops, its position in the landscape and the climate it experiences, form an amazingly intricate natural system; more powerful and complex than any machine that man has created. Soil may look still and lifeless, but this impression couldn’t be further from the truth. It is constantly changing and developing through time. Soil is always responding to changes in environmental factors, along with the influences of man especially through urbanization as a result of land use.

Therefore, the need to re-orientate human beings to take seriously the management of soil cannot be over emphasized. In fact, soil management and protection is an integral part environmental protection and this is why “human development since prehistoric times has been closely linked with an increasing ability to manage soil and other parts of the natural environment” (Nortcliff et al., 1998). According to an online publication by Scottish Natural Heritage, early attempts at soil management, areas of land were cleared of natural vegetation and cultivated for short periods. Once soil fertility started to decline, the site was abandoned and left to revert slowly to natural vegetation and activity now shifted to a newly cleared site. Increases in population and the development of towns and villages into urban cities encouraged people to remain at a single place for longer periods. This meant that some way of restoring soil fertility had to be found. One approach was to clear more land than was required and leave a part of it uncultivated or fallow. Another common practice was the addition of organic waste, from households or animals, directly to the soil.

These remained the normal methods of land management until about 100 years ago, this time, they have been less widely used, as inorganic fertilizers have developed.

In Nigeria for instance there is an obvious different between soil in the urban and rural area. The soil type could be the same but in terms of chemical composition they vary because the activities that goes on in the soil at the urban region most often differs from that of the rural area and a “sound knowledge of the relationship between urbanization as a result of land use and soil behavior (i.e. natural properties) can guide our choice of appropriate land use and soil management practices” (Olowolafe, 2008). Urbanization and land management practices therefore have major impact on natural resources, including water, soil, nutrients, plants and animals. They affect the amount or level of soil nutrients available to keep the soil healthy and efficient. It therefore leads to soil erosion, soil degradation, salinization and desertification (Dregne and Chou, 1992).

Industrialization is a major feature of urbanization and is vital to a nation’s socio-economic development as well as its political stature in the international committee of nations. It provides employment opportunities for a good percentage of the population in medium to highly developed economies however, industries vary according to products, characteristics by complexity of waters discharged. In developing countries such as Nigeria, citing industries is determined by various criteria, some of which are environmentally unacceptable threat posing serious threat to public health (Lundgren and McMakin, 2018).

Although industrialization is inevitable, various devastating ecological and human disaster, which have continuously occurred over the last three decades or so implicate industries as major contributors to environmental degradation and pollution problems of various magnitudes. Industrial waste and emissions contain toxic and hazardous substances most of which can be detrimental to human health. These include heavy metals such as lead, cadmium, mercury, and toxic organic chemicals such as pesticides, polychlorinated biphenyis (PCBS) dioxins, polyaromatic hydrocarbons (PAHS), petrochemicals and phenolic compounds. For instance, there was the case of the “Minamata disease” in Japan, which the patient has received untreated effluents from the low level of environmental awareness in developing countries such as Nigeria, coupled with the non-existence of environmental protection laws, and the abject poverty of these nations the developed countries have within the last decade, embarked upon “toxic waste trade or illegal dumping of toxic wastes in poor, debt-strapped developing countries (Ekhaise and Oni, 2012).

Land or soil pollution destroys the thin layer of fertile top soil, which covers the surface of earths land. This layer is very important for growth in plants which could be sometimes called soil pollution, resulting from the pollutant derived mainly from agricultural and mining activities, causes of land pollution includes refuse dump, animal waste, pesticides bush burning and also, improper disposal of industrial waste constitutes the major causes of land pollution. The truth of the matter is that it appears that “Industrialization is inevitable with various devastating ecological and human disaster, which have continuously occurred over the last three decades or so, this implicates industries as major contributors to environmental degradation and pollution problems of various magnitudes” (Ekhaise, 2012).

Industrial wastes and emissions contain toxic and hazardous substance most of which can be detrimental to human health. These includes heavy metals such as lead, cadmium, mercury, and toxic organic chemicals such as pesticides, polychlorinated iripheyls (PCBS), dioxins, polyaromatic hydrocarbons (PHS), petrochemicals and phenolic compounds. For instance, there was the case of the Minamata disease in Japan which the patient had received untreated effluents from a plastic factory. Even in Nigeria, the oil spillages that are highly toxic with harmful chemical have to a large extent destroyed the soil and the ecosystem of the Niger-Delta region.

No wonder Adebis et al. (2010) stated that “realizing the low level of environmental awareness in developing countries such as Nigeria, coupled with the nonexistence of environmental protection have within the last decade, embarked upon “Toxic waste trade or illegal Dumping of toxic wastes” in poor debt-strapped developing countries”. Nigeria has been a victim of this illegal act, when in 1988 about 8,880 tens of toxic and hazardous wastes were dumped in Koko in the part of Delta state by an Italian company. In order to stem the tide to toxic wastes dumping in third world countries, the united nations environment programme (UNEP), passed the resolutions on the trans boundary movement of toxic and hazardous wastes at the 1989 Basel convention, Appendix, a document to which Nigeria is a signatory, i.e. At Rio’ 89 convention held in Brazil. The major causes of land pollution areas follow:

i. Erosion:- This is usually caused by careless methods of farming and extensive cropping. It normally washes off soil and its nutrients.

ii. Refuse:- Usually from house hold, markets offices and factories. They lead to space occupation, cause odour after decaying and is an eye sore example of refuse includes: papers, garbage’s etc.

iii. Sewage:- This originates from household offices and industries. Gives off bad odour, may contain disease carrying organism which could find their way to water bodies, air or food.

iv. Metal scraps and old vehicle bodies originate from unused machines and vehicles:- Causes land pollution, occupies space and obstructs the use of land used for recreational and farming activities.

v. Glass:- From bottling company and glass industries and occupy spaces.

vi. Insecticides:- Used for crop protection, control of diseases vectors example mosquitoes. They cause the rate of photosynthesis to be lowered and can kill the consumers.

vii. Radioactive waste:- From nuclear plant, accident, explosion of nuclear and atomic bombs causes mutation in living things.

viii. Atomic Radiation:- Pollution by atomic radiation is as a result of nuclear exposing, leakages from nuclear power stations. This type of pollution damages living cells as well causes mutilation of plants and animals and loss of memory. Thus, these types of pollution have their aftermath effect on man.

It is in view of this that this research work “Physiochemical and Heavy Metal Analysis of Soil Samples from Selected Rural and Urban Areas” examines the soil samples from selected urban and rural to provide further information and data on the effect of industrialization on the environment with close emphasis to soil.

1.2 Statement of the Research Problem

Pollution of soil by chemical leachate from surrounding municipal waste dumps has been recognized for a long time. In Nigeria, like in other developing countries, open dump is the popular and available option for solid waste disposal in the cities. Studies have shown that soil and groundwater system can be polluted due to poorly designed waste disposal facilities, leakage from underground storage tanks, industrial effluents, and technological, domestic and agricultural wastes. Soil and groundwater acidification and nitrification have been linked to waste dumps Bacud et al., (1994) as well as microbial contamination of soil and groundwater system Awomeso et al., (2010). Sia Su (2008) attributed cancer, heart diseases and teratogenic abnormalities to groundwater contamination via leachate from waste dumps.

Increase in population and rapid expansion of cities has resulted in the generation of huge waste and the manner these wastes are disposed constitutes serious health and environmental problems. Particularly in the Federal Capital Territory, several dump sites and chemical leachate now litter around markets and workshops. A typical example is the Apo Auto-Mobile Workshop and several dumpsites in different locations in Abuja. The chemical deposits from these sites pose serious dangers to the health of those around such environment. Hence the need for this research is to ascertain the heavy metal situation of selected environments and detect if the levels of these heavy metals are below or above safety limits.

1.3 Aim and Objectives of the Study

The aim of this research is to evaluate the physiochemical and heavy metal analysis of soil in selected areas within the city and rural communities. The aim of this study will be achieved through the following objectives:

i. Determine the concentration of selected heavy metals in the selected soil areas.

ii. Determine pH, Electrical Conductivity, Organic Carbon, Total Carbon and Exchangeable Cation.

iii. Compare Physiochemical values obtained between rural and urban communities sampled.

1.4 Significance of the Study

It is possible that some analysis may have been done in this area generally; however, this work will focus specifically on worksites such as (mechanic workshop and dumpsites) that are close to residential areas which will be susceptible to leaching process. The study will serve as an important contribution to the cause of sustainable development, natural resources management and a significant understanding of the ecosystem.