ABSTRACT
Automobile junk markets have been observed to be one of the sources of heavy metal pollution in soil and water. The aim of this study is to assess the level of heavy metal pollution within two acclaimed biggest automobile junk markets at Obosi and Nnewi, Anambra State, Nigeria. Twenty four (24) composite soil samples including the background samples at 0-15cm and 15-30cm depths, and six (6) water samples were randomly collected. Samples were properly digested and subjected to spectroscopic analysis using Atomic Absorption Spectrometer (AAS) for trace metals, Physiochemical and Microbiological analysis. The result shows that trace metals concentration (ppm) in 0-30 cm depth are well above the background values with Ni in excess of international standard. Metal enrichment is in the order of Ni> Fe >> Zn > Cu > Mn > Pb > Cr. The pollution load index and contamination factor reveals that the soil around the automobile junk market is at various stages of pollution with heavy metals, ranging from slight contamination to severe pollution. The geoaccumulation index however suggested that the soil is not contaminated. Result also suggested that water around the automobile junk markets are not advisable for domestic uses, as a result of its heavy metal contents, acidity, high turbidity, high salinity and dissolved oxygen as well as the presence of bacteria such as coliform and e.coli which are connected to the effects of industrial waste accumulation and indiscriminate domestic waste disposal as suggested by the principal component analysis.
CHAPTER ONE: INTRODUCTION
- Background
Study
Heavy metals are
chemical elements that occur naturally and maybe toxic in high concentrations. Excess
heavy metal accumulation in soils is toxic to humans and other animals. Heavy
metals content of soil are of major significance because of their non
degradable nature and ability to accumulate for long period of time (Gallego et
al 2002, Wu and Zhang, 2010). Some of these heavy metals like Iron, Copper,
Zinc, Cobalt and Manganese are essential to life but can be toxic in high doses
(Adepoju-Bello et al, 2009). The environmental pollution concern rises when
they are in higher concentration due to natural mineralizing processes and/or
human activities. The impact of heavy metals on the environment is a concern to
government and the general public (Page and Chang, 1985, Feigin et al 1991,
Tiller 1992). Uncontrollable inputs of heavy metals are undesirable because
once accumulated in the soil, these elements are generally very difficult to
remove and potentially harmful effects that may arise in the future should not
be ignored.
The
concentrations of heavy metals in soils are associated with biological and
geochemical cycles and are influenced by anthropogenic activities such as
agricultural practices, transport, industrial activities, waste disposal
respectively (Lund 1990). Overload of heavy metals ions in soil environment
clearly poses a significant risk to the quality of soils, plants, natural
waters and human health (Adraino, 2001). The bioavailability of metal ion in
soils is influenced by the temperature, cation exchange capacity, organic
matter, competition with other metal ions, composition and quality of soil
(Moon et al.2000, Mapanda et al. 2005, Machender et al. 2010). Exposure to
heavy metals is normally chronic (i.e over a long period of time) due to food
chain transfer. Chronic problems associated with long term heavy metal
exposures are: Mental lapse, Kidney problems, skin poisoning, liver problems,
gastro-intestinal complications amongst others.
Some industries usually discharge their
wastes into the environment with little or no treatment. The automobile
industry is one of the producers of industrial pollutants into the environment
(Ogbuagu and Ajiwe, 1998). Automobile junks are waste auto engines traded and
transferred to developing countries. These waste or knock down engines are
recycled and reused or abandoned giving rise to poor waste management (fig1).
The alarming increase in water pollution
has been reported in a number of cities throughout the world because of its
overwhelming environmental significance. For instance, human exposure to heavy
metals has risen dramatically in the last 50 years as a result of an
exponential increase in the use of heavy metals in industrial processes and
products (Ano et al., 2007). The decomposing nature of industrial discharges,
urban storm water runoff and agricultural drainage can pollute surface and
underground waters. Crude recycling of used engines and transmission is a major
concern to environmental health and safety.
This research work assesses soil and water
contamination by heavy metals and microbiology in the vicinity of auto junk
market causing soil degradation, water contamination and pollution in the soil,
rivers and groundwater across Obosi and Nnewi automobile junk markets in
Anambra State, Nigeria.
1.2 Heavy Metal Availability
Soils naturally contain trace
levels of metals and heavy metals also occur naturally, but rarely at toxic
levels (Estifanos, 2013). The
presence of metals in soils, therefore, is not indicative of contamination
(Nwachukwu et al, 2013). The concentration of metals in uncontaminated soil is
primarily related to the geology of the parent rock material from which the
soil was formed. Depending on the local geology, the concentration of metals in
a soil may exceed the acceptable ranges. A catchment area containing
mineralized rocks will usually have elevated metal levels as the trace metal
content of rivers in the catchment area and by their mobility (Olajire and
Imeokparia, 2001; Adekola and Eletta, 2007, Nwachukwu et al, 2013). However,
mining, manufacturing, and the use of synthetic products (e.g. pesticides,
paints, batteries, industrial waste, and land application of industrial or
domestic sludge) can result in heavy metal contamination of urban and
agricultural soils (Ogbuagu and Ajiwe, 1998). The heavy metals threatening the
ecosystem include mercury, arsenic, copper, barium, cadmium, antimony,
chromium, lead and zinc (Estifanos,
2013).
Immobilization
of metals by mechanisms of adsorption and precipitation will prevent movement
of the metals to groundwater. Metal-soil interaction is such that when metals
are introduced at the soil surface, downward transportation does not occur to
any great extent unless the metal retention capacity of the soil is overloaded,
or metal interaction with the associated waste matrix enhances mobility.
Changes in soil degradation of the organic waste matrix, change in pH, redox
potential, or soil solution composition due to remediation and weathering
processes enhance metal mobility (Mclean and Bledsoe, 1992). The concentration
of metals in the soil solution, at any given time, is governed by a number of interrelated
processes, including inorganic and organic complexes. These processes are
oxidation/reduction reactions, precipitation/dissolution reactions, and
adsorption/desorption reactions.
In aquatic ecosystems, contaminants are
often rapidly removed from the water column via adsorption processes (Opuene,
and Agbozu, 2008). Given that heavy metals are not subjected to degradation
processes, they tend to accumulate in benthic sediments (Baeyens et al, 1998).
However, heavy metals are not necessarily fixed permanently to sediments;
rather they may be remobilized via chemical, physical, and biological
processes. The geochemical processes that control the metal mobility and its
availability are dissolution, adsorption into mineral and organic particles,
mineralization, complexation by biogenic or non-biogenic ligands, and
subsequent uptake by biota (Kraemer, and Hering, 2004). Once deposited, metals
become subject to a variety of physical, chemical and biological processes that
could potentially rework them back into the water column. The processes can be
both natural (e.g. bioturbation, erosion) and anthropogenic (e.g. land
reclamation, dredging) (Lee and Cundy, 2000). Anthropogenic factors are of
particular significance in this present study due to indiscriminate large scale
dumping of automobile junks.
1.3 Global Perspective
One of the keys to understanding the
spatial and temporal distribution of heavy metals within automobile junk
markets and their environmental significance is to understand the process within
a global context. Heavy metal pollutants are a problem for developing nations
across the globe, and as such they have become the focus of a number of studies
in recent years; with some key advances in our understanding. Pollution and
particularly heavy metal pollution is a serious problem in many parts of the
world; whether they are the result of ongoing industrial development such as
that in Africa, or a relic signature of industrialization in the west and south
China. If informed mitigation policies are to be proposed to deal with the
potential future environmental impact of these ‘indiscriminate’ pollutants
discharge, it is imperative that we understand not only the concentrations
present, but the actual effect they have on the ecology.
Following the wave
of global economic recession, automobile wastes, particularly knockdown engines
are continually transferred from industrialized nations to developing countries
for recycling and reuse. Much as this business has exceeded the permits of the
World Trade Organization (WTO) as a type of waste transfer, it has found a
place in Nigeria (Nwachukwu et al, 2013).
As new genuine automobile spare parts become more and more expensive or
unavailable, motorist in developing countries have resorted to the use of fairly
used parts sold in junk markets. Container loads of used engines classified as
waste in many industrialized nations are now transferred to developing
countries where they are refurbished and sold in junk markets. Over the last
three decades there has been increasing global concern over the public health
impacts attributed to environmental pollution, in particular, the global burden
of disease (Laniyan et al, 2011, Onwukeme
et al, 2013).
The
unprecedented increase in transfer of junk automobile engines and transmissions
from industrialized to developing nations of the world may be reciprocated by
more automobile junk markets and mechanic villages. As a result, the
environmental impacts of automobile junk markets may cause greater concern to
land use planning, water resources management, and public health. Topsoil
within and around automobile junk markets become heavily contaminated by toxic
heavy metals in many parts of Nigeria. Storm water from automobile junk markets
gets into the waterways untreated, and there is no protection to both surface
and groundwater within and around automobile junk markets. There is also no
form of groundwater monitoring wells for safety either by government
establishments or by non governmental agencies.
However, the
global community is becoming increasingly aware of the values of an ecosystem,
as well as the implications of man’s activities on sustainable development; an
advocate of a balanced and quality environment (Onwughara et al, 2011). A
balanced and quality environment in-turn sustains biodiversity, healthy
biophysical domain, promotes socio-economic and public health sectors. In high
concentrations, trace metal ions react to form toxic compounds in both flora
and fauna cells (Nies, 1999). They are potentially extremely toxic and not only
would they affect the biota at a water soluble concentration at less than 1
part per million (ppm), humans can be grossly affected (Asonye et al., 2007).
What is yet to be fully known by a generality of the society particularly in
the developing world are the ecological and toxicological implications of
increased releases and discharges of heavy metals into the environment. The
World Health Organization (WHO) estimated that about a quarter of the diseases
facing mankind today occur due to prolonged exposure to environmental pollution
(WHO, 2006).
Nigeria has
begun to place a high priority on environmental matters, particularly
water-related issues. This is reflected in recent environmental policy,
legislation, action plans and programs introduced by the Government. In all
these programs, environmental monitoring activities, especially water quality
aspects, are given strong consideration. With the creation of the Federal
Environmental Protection Agency (FEPA) as the central coordinating body for all
environmental matters within the country, Nigeria has evolved a mechanism that
will monitor adequately and will keep records of all relevant environmental
variables. The new integrated water resources management concept adopted by the
government will without doubt, improve all aspects of water use and
conservation within the country if the political will and financial resources
for the implementation are sustained. Specific regulations to protect
groundwater from pollution have also been issued by the FEPA (FEPA, 1991b,c).
Industrial sites have to meet concentration limits for their effluents.
For the protection of human health,
guidelines for the presence of heavy metals in water have been set by different
International Organizations such as United States Environmental Protection
Agency (USEPA), World Health Organization (WHO), Environment Protection Agency
(EPA), European Union Commission (Marcovecchio et al, 2007; Jim et al, 2004),
thus, heavy metals have maximum permissible level in water as specified by
these organizations. Maximum contaminant level (MCL) is an enforceable standard
set at a numerical value with an adequate margin of safety to ensure no adverse
effect on human health (Onwughara
et al, 2010). It is the highest level of a contaminant
that is allowed in a water system.
1.4 Research Hypothesis
The ever
increasing number of automobile junk markets and knockdown engines over a wide
geographical spread will constitute a severe environmental problem this
millennium, if not properly addressed. For example, the Obosi automobile junk market
is situated at about 1Km from the Idemili River at a slope of 10% which
facilitates the quick transport of deleterious contaminants to the residential
area and the Onitsha urban waterway which on the other hand serve as the
primary source of water and aquatic food to Onitsha metropolis (Nwachukwu et
al; 2013).
Poor
development of automobile junk market is possible to cause significant
ecological impact relating to depth, degree, and distance of distribution of
metal contaminants in the soil. It is obvious, that trace metal concentration
in soils might usually be high near the point source, which will always dispel
with both distance and depth owing to increasing limits in mobility and
physical dilution. Depth of dispersion accounts for the tendency to groundwater
pollution.
1.5 Study
Area Description
The study area covered two semi urban towns of
Obosi and Nnewi located in Idemili North and Nnewi North local government areas
of Anambra state which are faced with the risk of soil and water
pollution. Both
towns have a high population density of more than 1000 persons per
hectare. The population has continued to
grow making the city to sprawl toward surrounding villages and smaller
towns. The government established
automobile junk markets in these villages to reduce the pollution from the
activities of mechanics in the city. However, urban development and growth have
made the erstwhile isolated automobile junk markets to be crowded by
residential buildings. Migrant
workers and civil
servants working in
various institutions and
establishments have moved close to the automobile junk markets and the
people are now faced with the potential risk of contaminants released from the
area.
Obosi is located between latitude 6o 06’ 23.78’’N and longitude 06o 47’57.00’’E while Nnewi is located between 6o 01’13.62’’N and 6o 52’ 52.58’’E as shown in Figures 2 and 3. Obosi is a town in Idemili North Local Government Area and Nnewi is in Nnewi North Local Government Area of Anambra state. The area lies within the humid tropical rainforest belt (Iloeje, 1965). Obosi and Nnewi are influenced by two major trade winds: the warm moist southwest trade winds during the rainy season (April-October) and the north east trade winds during the dry and dusty harmattan (November-March). The average annual rainfall is 1500mm. The temperature is generally high (maximum monthly temperatures varies between 27.2°C and 35°C, the highest between February and March, and minimum temperature varies between 18.2°C to 23°C, the coolest between August and September). The daily mean humidity of the area varies between 40% and 92%.
HEAVY METALS AND MICROBIOLOGICAL CONTAMINATION IN SOILS AND WATER AT AUTOMOBILE JUNK MARKET IN OBOSI AND NNEWI, ANAMBRA STATE: A COMPARATIVE ANALYSIS
