Soil is  the top layer of the earths surface  in which plant can grow, consisting of  rock and mineral  particles  mixed  with decayed organic  matter and having the  capability  of retaining  water
Soil contamination or soil pollution is caused by the present of venotiotic (human –made) chemicals or other alternation in the natural soil environment. It typically caused by industrial activity, agricultural chemicals or improper disposal of waste.

The main mason why the soil become contaminated  is due  to the presence of man made waste. The waste produced from nature itself such as dead plants, carcasses of animals and rotten fruits and vegetable only add to the fertility of the soil. However, our waste products are full of chemicals that are not originally found in nature and lead to soil pollution
With the rise of concrete buildings and roads, one part of the earth that we rardy see is the soil. It has may different names, such as dirt, mud and ground. However, it is definitely very important to us. The plants that feed us grow in soil and keeping it healthy very important to us.  The plants that feed us grow in soil and keeping it healthily is essential tomaintaming a beautiful plant, however, like all other forms of nature, soil also suffers from pollution.  The pollution of soil is a common thing   these days, and it happens due to the presence of man activities. 
The  waste  produced from nature itself such as dead  produced from nature itself such  as dead  plants, carcasses of animals and rotten fruits and vegetables only adds to the  fertility of soil.  However, our waste products are full of chemicals that are not originally found in nature and  lead to soil pollution.

1.      Industrial Activity: Industrial activity has been the biggest contribution to the problem in the last century, especially since the amount of miming and manufacturing has increased. Most industries are dependent on extracting minerals form the earth.  Whether it is iron over or coal, the by products are contaminated and they   are nod disposed off in a manner that can be considered safe. As a result , the industrial waste  lingers in the soil surface for a long time and makes it  unsuitable  for use
2.      Agricultural Activities:  Chemical utilization has gone up tremendously since technology provided us with modern pesticides and fertilizers. They are full of chemicals that are not produced in nature and cannot be broken down by it. As a result, they seep into the ground after they mix with water and slowly reduce the fertility of the soil. Other chemicals damage the composition of the soil and make it easier to erode by water and air. Plants absorb many of these pesticides and when they decompose, they cause soil pollution since they become a part of  the land.
The three primary textual classes of soils are basically a product of the mineral make-up of the soil. This further depends on the parent materials other factors that influence soils formation includes climate, topography, animals and vegetation (Adams et al, 1999).  
On rocks and rock debris, plant growth begins with mosses and llichens, which help to statulge the loose materials by hiding and reducing wind speed over the surface. Furthermore, dead plants becomes incorporated in the young soil together.
As a young soil deepens, large are able to develop. Their roots help  stahilne the soil further  and  along with carbonic acid they produce, extend the depth of  weathering soils.  Adams et al (1999) added that although the process can take very long time, its speed in increased when the particle becomes finer and living organisms becomes established. Finally, the type of parent material determines the specific type of soil formed, for instance,  guards  mineral forms sand soil while  limestone  forms clay etc  
Legume vegetation cover improve soil phosphorus. This is supported by Agboola (1975) who reported that  in Nigeria, a single   season intensive follow with  crotalorie specie, succeeded in increasing  the available phosphorus content of a field soil from  7.8kg /ha to  12.1kg/ha. In another experiment, under sowing legumes in maize reduced the uptake of available phosphorus by some 50% within four growing seasons. Agbola and Feyemi (1972) concluded that the legumes were able to keep the phosphorus in an increase as the clay content increases. This increase depends on two mechanisms. First, bonds between the surface of clay particles and organic matter retard the decomposition process. Second, soils with higher clay content increase the potential for aggregate formation.
Macro aggregates physically protect organic matter molecules from further mineraligation caused by microtonal attack for example, when earthworm casts and the large soils particles they contain are split by the joint action of several factors. (climate, plant growth and other organisms),  nutrients are released and  made available to other components  of micro-organisms under similar climate conditions, the organic matter accumulation  not only through  its effect on soil texture  (Mcgary, 1996). Soils developed from inherently not material, such as basalt, are more fertile  than soils formed from granitic  material, which contains  less mineral nutrients.
In principle, trees and shrubs can reduce the acidifying effect of   leaching young (1982)  reported that whether tree litter can be a significant means  of raising  PH  on acid  soil is doubtful, owing to the order of longitude involved, expect through the  release of bases that have been accumulated dung  many  years of tree growth, as in forest clearance  or the (Chitemene ) system of  shifting   cultivation. Young (1982) further stated that the situation is different with respect to checking acidification. in  the first place, if the tree  compocont is employed as  the  means l for fertility  maintenance,  then  no trend towards   acidification, this is  in order of  0.1 PH point   per year.  The recycling  of bases in trees litter could quite probably be  sufficient to counteract an effect of this magnitude.
Soil PH or soil units. The PH scale goes from 0 to 14 with  PH7 as the neutral point. As  the amount of hydrogen ions in the soil increases, the soil PH decreases, thus becoming  more  acidic,  and l ;from PH 7  to  14,  the  soil  is  increasingly more alkaline or basic. According to Vermeer (1996), a  soil PH of   6 has  10 times  more hydrogen ion than a soil  PH  lern adrerse   to crop growth ion  occur naturally in some  regions, it can also be indued by acid rain or soil  contamination from acid or bases.   With bread et al,  (1998) supported  this  view by stating that the  role of soil  PH  is to control nutrient  availability   to vegetation
The principal macro nutrients (calcium, phosphours, nitrogen, potassium,,   magnesium, sulphur) prefer neutral to slightly alkaline soils, calcium, magnesium and  potassium are susually made available to palnts through cation exchange  surface of organic  material  and clay soil surface particles
Observation by  veratna )1997) showed  that addition  of one of ground plant material per  20g  of soil raised the organic  content of the oil to  1.86%, PH 6.4 niitegen content  0.18%.  letroy et al (1999) reported  that while  audifiation increases the initial  availability of these cutions, the  residual soil moisture concentrations of nutrients cations could   fall to alarmingly low levels   after initial nutrient up take moreover there is one  simple  relationship of PH to nutrient  availability because of the complex  combination of soil  types,   soil moisture regimes and   meterological factors.  Excess of organic  matter can have a lowering effect on the PH  value  of   most soils  (mbagwu and piccolo,  1990)  

When  plant residues  are returned to the soil, various  organic  compounds undergo  decomposition.  Decomposition is a biology process that includes the physicial breakdown and biochemical transformation  of complex organic molecules   of dead material   into simpler  organic and inorganic mdecules.
Decomposition oforganic matter is largely a biological process that  occurs naturally. Its  speed is determineby  three major  factors soils  organisms, the  physical envieornment and the quantity of  the organic matter (Brussaard,  1994) . in  the decomposition process, different product are released, carbon  compounds 
Successive decomposition of dead material and modified orgnic matter results in the formation of a more  complex organic matter   called l humus. This  process is called humification.  Humus  affect soil properties .  as  it slowly decomposes, it colours the soil darker, increases soil  aggregation and aggregate stability, increases the CES (The  ability to  attract  and retain nutrients),  and  contributes N,P and  other nutrients. Soil organisms,   including micro –organisms, use soil organic   matter  as food.  As they breakdown the organic matter, excess nutrients (N,P  and S)  are released into the soil in forms that plant can use. This  released by micro-organisms are also soil organic  matter.  This  waste materials is  less  decomposable than l the  original  plant and aimal materials,  but  it can be used by a large number of organisms (levelle and spain,  2001). By breaking down carbon  structures and rebuilding new ones or storing  the C into   their  own biomass, soil biota   plays the most important role  in nutrient  cycling  process and, thus,  in the ability of a soil to provides the  crop with  sufficient   nutrients to harvest a healthy product  (FAO,  2002).  The   organic matter   content, especially the more stable  humus, increases the capacity to  store water  and store (Sequester) from  the atmosphere (Linn and Dovan,  1984), organic matter serves as a nuturient store from which basic cations are slowly decomposes, it colours the  soil darker, increase soil aggregation and aggregate stability, increases the  CEC (The  ability to attract and retain nutrients), and  contributes N,P and  other nutrients
Soil organisms, including  micro organisms, are  soil orgnic  matter as  food. As they break down the organic matter, excess nutrients (N, P and S) are  released  into the soil in form that  plant can use. This  release   process is called  mineralization. The  waste material is  less  decomposable than the original plant and animal material, but it can be used by a large  number of o0rgnisms (Lavelle and Spain,  2001).  By breaking down caibon structures and rebuilding new one sor storing the C into  their own biomass, soil biota  plays  the most important role in nutrient cycling process and,  thus, in the ability of a soil to provide the  crop with sufficient nutirients to hearvest a helthy   product (FAO  2002).  The  organic matter content,  especially the more stable humus, increases the  capacity   to store water and store (Sequester ) from  the  atmosphere  (LINN AND Doran,  1984).  Organic  matter serves as a nutrient store from which basic cations  are  slowly   released into the  soil. It  account for  over 80% cation exchange capcity (CEC) OF THE HUMINAL TROPICALsoil (AGBOLA AND  FAGHENRO 1985). The type of  vegetation determines the type of cover and quality  of organic matter in the soil. Legume according to  Brady and Weil (1999), makes riche organic  matter than   grasses and gmelina covers. Mineral colloid and  organic matter   constitute  the  soil exchange  complex being negatively charged (Nwingyi,  1977).
According  to Ekpe (2002), Orgaic  matter is  a  store house   for plant nutrients  is also  the cementing in soil  structure  and aggregate formation. Ekpe (2002)  also noted   that  soil organic  matter help to improve the soil water  holding  capacity and hydraulic  conductivity.  Excess of organic  matter can have a lowering effect of the PH    value  of most  soils
Furthermore, with  time iron oxides of the soil are soluvilized and leached specially in the   tropic where activities of  micro organism are  high

Organic  mater  from vegetation cover  contain exchangeable  bases in varied quantities. These mineral nutrients  are important  components of the vegetation  bio-system which   it releases   to the soil on death and decomposition.  The  efficiency of  the use of  vegetation to  improve  on soil properties is dependent on the stage  of  growth of  the vegetation.  In legume, maximus effect is  achieved at flowering   stage while in grasses it is   somewhat earlier (MULLERN  SAMANN AND KOTSCHI 1994) Gmelina cover is reported to be effective   only when it is about  12  month old.
The exchangeable incorporated in soil by organic  matter resulting form vegetation cover are similar  to those from any   other form of  organic matter.   The  exchangeable bases    content   of  soil  differ depending on the parent   material  vegetation  cover, cropping history and soil management practices employed  finally, economic  justification of the use of organic  fertilizer lies in the necessary to cope  with prevalent  increase in  the cost of mineral fertilizer and reduction in the waste of nutrient  result from on under utilization of  organic  residue  (FAO  2002). 
organic matter affect both the chemical and physical properties of the soil and its overall health  (FAO, 2000) properties influenced by organic  matter include: soil structure, moisture holding capacity, diversity and  captivity of  soil organisms, both those that are beneficial and harmful to crop production and nutrient availability (Vieria and Van Wambeke  2002).
However, it also influence the effect of chemical  amendments, fertilizers pesticides and herbicides. Organic  matter has been known to be a major  natural source of both macro and micronutrient. Organic matter has many benefits in the  and  porosity and  increase in  the  number of macropores, and thus to greater infiltration rates. Increased levels of  organic  mater and  associated  soil  fauna lead to greater pore space  with the immediate result that water infiltrates  more readuy biotur batting  activities of earth worms  and other macro organism and channels  left  in the soil by  decayed  plant roots. Rainwater  infiltration increased from  20mm/h under conventional  tillage to  45mm in under  no  tillage’s. Over  a long period,  improved organic matter promotes good  soil  structure and macroporsity , water   infiltrates   easily similar to forest soils
In addition organic  matter contribute to the stagility of soil  aggregates and pores through the bounding  or adhesion properties of organic  matrials, such  as   bacterial waste    products, organic gls, fungal hyphas and worm secreteions  and casts (tate et al,  2004) 
Moreover organic matter intimately mixed with mineral   soil materials has a considerable influence in  increasing moisture holding  capacity. Especially  the  topsoil, where the organic  matter stoe form which  basic  cations  are  slowly   released into the soil. Ortanic  matter accounts for over  80%  cation exchange  capacity (CEC) of the  humed tropical soils (Agboola and faghenro,  1985) .  the  quantity of organic matter in the soil at any given time is an indication of  the capacity of  the soil to renew  the supply when  the  nutrient  in solution have been  utilized. Mineral   colloid  and organic  matter constitute and soil  exchange complex, being negatively charged (Nwiniyi,  1977)   organic matter contributes very significantly  to the soil cation   exchange  capacity.  Through  exchange  processes plant can take up exchangeable cation  which  are important  as nutrient  (Wezel et al  2000)
Nitrogen is one of the macro nutrient needed for  maximum growth production      and  yield of crop.  Nitrogen is very important  for protein synthesis and nuclicic acids sysnthesis. Nitrogen is one of the essential elements. It is utilized by plant   for making  proteins and chlorophy   (Watkins et al  2006). Overation by  agbooola (1982) showed that  organisms cannot use gaseous nitrogen except   some  few  species of bacteria and blue green alge that are capable of utilizing the gaseous nitrogen form the soil. Gaseous nitrogen bacterial called Azotobacter  Clostridum   and Rhospirllum  living in the soil, nitrogen fixing  bacteria (Sysmbiotic bacteria),  the species   of phizobuim such  as R leguminosarium have  symbiotic association  with  roots of  some leguminous plant such as groundnut , beans  and crotalaria, furthermore, these sysmbiotic bacteria enter  the root hair walls of the  lequmes and multiply  thus causing swellings or  nodules in the  infected  cells   karl  and  Johannes (1994)  noted that the most  glaring  effect of grass   cultivation on nutirient  economy of the soil is  ntitrogen enrichment. Gasser (1964)  asserted that organic    nitrogen not only   increase  tutrifying   activities  of   micro organism   but also   decreases nitrogen losses by  increasing  cation exchange  capacity.  Crop reside added  to  the soil   fixed nitrogen in soil during  the early state of decomposition of  solube carbohydrate.  This is that  succeeding crop suffered. Nitro  deficiency  (Agboola,  1982.  Ahmed  et al, 1969) and   Azevedo and stout,  1979) . they recommended  supplemental  nigtrogen to achieve a C.N   ration of  less   than  15:1  this  organic  source according to their  report  could also   come  from  animal  droppings .

3.      Waste  disposal: finally, a  growing  cause for concern is how we dispose of our waste  while industrial waste is another way in which we are adding to   the population  every  human  produces a  certain  amount of peronsal waste products by way or  urine  and feces
While much of it mores into the sewer the system, there is  also   a large amount that is dumped directly into landfills in the form of diapers. Even the swer system ends  at the landfill, where the biological waste pollutes the soil and water. This is because  our bodies are full of   toxins  and chemicals which are now seeping  into   the  land and  causing pollution  of soil  

4.        Accidental  oil  spills:  Oil  leaks can happened during  storage and transport of chemicals. This   can be seen at most of the fuel stations/.   The chemicals present in the fuel deteriorates  the quality of soil and make them unsuitable   for cultivation. These chemicals can enter into  the ground water through soil and make the water undrinkable  
5.      Acid rain:  acid rain is caused when pollutants present in the air mixes up with  rain and fall back on the ground.  The polluted   water could dissolve away some of the important nutrients found in soil  and change the structure  of the soil    
1.  On health of human
Considering  how soil is the reason we are able to sustain  ourselves, the contamination of it has maor consequences on our health. Crops and plants  grown on polluted soil absorb much of the pollution and  then pass these on to us. This  could  explain the   suddn surge in small  and terminal  illnesses long term exposure to such soil can affect the gentic  make up of the body causing  congential illnesses and   chronic health problems that cannot  be cured easily. In fact, it can sicken the livestock to  a  considerable  extent and cause food  poisioning over a long period   of time .  the soil polluation can even bad  to wide spread famines   if the plants are unable  to grow in  it
2.  On growth of plants:  the  ecological balance  of any system gets affected due to the widespread  contamination to the soil. Most  plants are unable to  adapt when the chemistry of the  soil changes so   radically  in a short period of time.  Fungi and bacteria found  in the soil that  bind   together  begin to  decline, which   creates an additional problem on soil  erosion
The  fertility slowly  diminishes,   making  land unsuitable   for  agriculture and any local  vegetation  to survive. The  soil pollution causes large  tracts   of  land to become  hazardous   to health  unlike deserts, which are  suitable for  its native  vegetation,   such land  cannot  support  most form of  life.
3.  decreased soil  fertility  : the toxic  chemicals l  present in the soil  cand  decrease soil  fertility  and therefore decrease in the yield  then   contaminated soil  is then used to  produce fruits and vegetables which lacks quality ad nutrients    and may contain some poisonous substance to cause   serious health problems in people  consuming them.
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