Soil pollution

Soil pollution is defined as the presence of toxic chemicals (pollutants or contaminants) in soil, in high enough concentrations to pose a risk to human health and/or the ecosystem. In the case of contaminants which occur naturally in soil, even when their levels are not high enough to pose a risk, soil pollution is still said to occur if the levels of the contaminants in soil exceed the levels that should naturally be present.

Main Causes of Soil Pollution

1. Industrial Activity: Industrial activity has been the biggest contributor to the problem in the last century, especially since the amount of mining and manufacturing has increased. Most industries are dependent on extracting minerals from the Earth. Whether it is iron ore or coal, the by products are contaminated and they are not 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.

3. Waste Disposal: Finally, a growing cause for concern is how we dispose of our waste. While industrial waste is sure to cause contamination, there is another way in which we are adding to the pollution. Every human produces a certain amount of personal waste products by way or urine and feces.

While much of it moves into the sewer the system, there is also a large amount that is dumped directly into landfills in the form of diapers. Even the sewer 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 happen 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 groundwater through soil and make the water undrinkable.

5. Acid Rain: Acid rain is caused when pollutants present in the air mixes up with the 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.

Effects of Soil Pollution

1. Effect on Health of Humans: Considering how soil is the reason we are able to sustain ourselves, the contamination of it has major 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 sudden surge in small and terminal illnesses.

Long term exposure to such soil can affect the genetic make-up of the body, causing congenital illnesses and chronic health problems that cannot be cured easily. In fact, it can sicken the livestock to a considerable extent and cause food poisoning over a long period of time. The soil pollution can even lead to widespread famines if the plants are unable to grow in it.

2. Effect on Growth of Plants: The ecological balance of any system gets affected due to the widespread contamination of 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 it together begin to decline, which creates an additional problem of 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 forms of life.

3. Decreased Soil Fertility: The toxic chemicals present in the soil can decrease soil fertility and therefore decrease in the soil yield. The contaminated soil is then used to produce fruits and vegetables which lacks quality nutrients and may contain some poisonous substance to cause serious health problems in people consuming them.

4. Toxic Dust: The emission of toxic and foul gases from landfills pollutes the environment and causes serious effects on health of some people. The unpleasant smell causes inconvenience to other people.

5. Changes in Soil Structure: The death of many soil organisms (e.g. earthworms) in the soil can lead to alteration in soil structure. Apart from that, it could also force other predators to move to other places in search of food.

A number of ways have been suggested to curb the current rate of pollution. Such attempts at cleaning up the environment require plenty of time and resources to be pitched in. Industries have been given regulations for the disposal of hazardous waste, which aims at minimizing the area that becomes polluted. Organic methods of farming are being supported, which do not use chemical laden pesticides and fertilizers. Use of plants that can remove the pollutants from the soil is being encouraged. However, the road ahead is quite long and the prevention of soil pollution will take many more years.

Soil amendments:

Soil amendments are anything mixed into topsoil to promote healthy plant growth. They function in a number of ways. For example, they may change the pH of soil or supply nutrients.

Soil amendment includes all inorganic and organic substances mixed into the soil for achieving a better soil constitution regarding plant productivity. Soil amendment does not include mulching, which includes substances lying on top of the soil. There are different substances for different soils and plants to optimise the soil conditions. A very common amendment is the addition of organic matter like compost, due to its low production costs.

Advantages:

? Soil amendments improve the physical properties resulting in better conditions for water storage, root development and soil ecosystems

? Soil amendments enhances soil aeration

? Soil amendments can be produced locally, especially organic amendments (e.g. compost), which are cheap to produce

? Soil amendments can be applied almost everywhere by almost anybody

Methods of Amendments:

Both inorganic and organic substances can be added into the soil. Organic substances consist of material derived from living things (e.g. plants), whereas inorganic substances are mined or man-made.

Inorganic Amendments

Inorganic substances are vermiculite, perlite, tire chunks, pea gravel and sand. In general, they must be bought, which makes them more expensive than organic amendments. Additionally, the industrial production process needs a great deal of energy. Therefore, these substances do not have the same degree of sustainability as organic amendments. Most are relatively sterile (with regard to plant pathogens) and many are relatively inert. Inorganic amendments are used to (REED 2007):

? increase aeration

? increase drainage

? decrease excessive water holding capacity

? decrease or increase weight.

Organic Amendments

Organic growing medium amendments usually are derived from plants or plant products that occur naturally (peat moss from peat bogs), or are the by-products of processing plants or mills (sawdust, cedar chips, bark, bagasse, rice hulls) or waste disposal plants (compost, processed sewage sludge, biosolids). The main purpose of using organic amendments is to loosen the soil and create large pores to increase (REED 2007):

? aeration

? drainage

? usable water holding capacity

? nutrient holding capacity

? decrease growing medium weight (compared to soil)

By far, the most important organic soil amendments worldwide are compost and animal dung (e.g. chicken, cow). Compost and animal dung are most often easily available and economically affordable.

In professional agriculture, the most commonly used organic amendment is peat moss (e.g. sphagnum peat moss which is the highest quality, but also hypanaceous or domestic peat). Other organic amendments include wood chips, grass clippings, straw, compost in general (produced in large or invalid link facilities), manure (see also use of compost, use of dehydrated faeces or terra preta), processed sewage sludge (biosolids), sawdust, etc. Normally, there are more organic substances available than inorganic substances and generally they are cheaper (REED 2007; GIZ 2010). Practising good crop rotations and choosing the correct crop improves soil amendment.

Before incorporating into ground beds, most organic amendments, especially sawdust, cedar chips, bark and bagasse, should be composted or aged, and sterilised before use if possible. All of these amendments have a high C:N ratio. Use of amendments which are not composted and have a high C:N ratio will deplete N from the soil, may cause a salt or an ammonia/ammonium burn, or may cause damage due to heat buildup.

Amendments with a low C:N ratio will release N upon further decomposition, thus act as an organic fertiliser. However, organic matter with a low C:N ratio also should be composed to avoid rapid ammonia/ammonium release and toxicity .