Introduction: Soil Pollution is a considered as a major challenge for healthy environment. The weathering of earth’s crust forms, soil over the centuries that supports the variety of microscopic and macroscopic life-forms.
Soil Pollution can consist of anything that contaminates the soil. Thus, it is also referred to as soil contamination. It occurs when pollutants in the soil reduce soil quality and make it inhabitable to organisms such as insects.
Soil Pollution (also soil contamination) refers to the degradation of soil quality either due to human activities or due to natural phenomenon leading to:
- decreased agricultural output,
- deterioration in crop quality,
- exposure to harmful and toxic chemicals
- health risks of people living on it,
- health threats to animals,
- contamination of underground water further resulting in polluted water supply,
- imbalance of the soil ecosystem.
The top most layer of soil is composed of minerals of various sizes and organic matters along with pores filled with air and water. Soil is said to be contaminated when there is the presence of excess chemicals such as nitrate, ammonia, petroleum hydrocarbons, lead, naphthalene, mercury, pesticides, etc.
It is chiefly the lack of human awareness that makes land lose its fertility simultaneously increasing its alkalescency and acidity. As a result, the surface of the soil erodes. This erosion is called soil pollution.
Types of soil pollution.
Soil pollution tends to come from human activity. The key types of soil pollution are enumerated below.
- Acidification of the soil: The acids found in rainwater such as carbonic acid, and in decomposing organic material such as humic and fulvic acids, etc., can stimulate leaching by dissociating into H+ ions and their component anions which then displace or attract base cations from the soil exchange complex.
- Salinization of the soil: It refers to an increase in salt content in the soil. It may lead to soli erosion and may affect the crop output. Although salinization occurs naturally in semi-arid and arid environments, it is often exacerbated as a result of human activity. In India, an extensive portion of desert region in Rajasthan consists of saline soil. In parts of southwest Australia, for example, removal of indigenous eucalyptus forest has resulted in extensive salinization of soils. This has occurred because the deeply rooted trees have been replaced by shallow-rooted grasses and crops, which are less effective in lowering the ground-water level. Capillary action is most intense, and salinity is greatest in soils where the water table is within about 2 meter of the surface.
- Agro-chemical pollution: In recent decades, the use of inorganic fertilizers has increased dramatically at the expense of more traditional organic nutrient treatments. Chemical runoff from pesticides and fertilizers can degrade soil quality, whilst animal manure can change its chemical composition. Inorganic fertilizers are used in preference to organic treatments because the nutrients are in a more readily available form and are released rapidly after applications. Fertilizers are applied in a variety of forms — solution, suspension, emulsion and solid. The solid forms vary in particle size from fine powder to coarse granules and either spread evenly (broadcast) over the soil surface or mechanically placed, by drilling, into the rhizosphere. Generally the rate of nutrient release decreases with increasing particle size. Fertilizers are based on compounds of plant macro-nutrients (e.g. nitrogen, phosphorus and potassium) and micro-nutrients (e.g., Zinc, copper, boron and molybdenum).
- Industrial soil pollution: Industrial development has been associated with both physical degradation and chemical contamination of soils. Problems of physical degradation include erosion, compaction and structural damage resulting from construction activities and opencast mineral extraction. The industry is also responsible for dumping industrial chemicals and heavy metals (such as mercury) onto soil and thus polluting it.
- Urban soil pollution: Human urban activities such as dumping waste, disposing of sewage poorly and emitting greenhouse gases which dissolve into the rain and seep into the soil are some of the main types of urban soil pollution. Chemical problems result from waste disposal activities, discharge and spillage of liquid effluents and atmospheric emission including acid deposition.
Causes of soil pollution.
As is evident from the list below, soil pollution is almost always down to human activity such as agriculture and heavy industry.
- Industrial Pollution: Improper disposal of chemical wastes from industries causes soil contamination. The main human made causes of acidification include certain heavy metals, industrial waste, oil and fuel dumping, toxic chemicals, and acid deposition resulting from industrial pollution.
- Needle-leaf afforestation: Needle-leaf afforestation has been associated with the acidification of soils and surface waters for a number of reasons. First, needle-leaf trees produce litter which is very acidic in comparison with most broad-leaf species. Second, because of their high canopy surface area, needle-leaf trees are able to ‘scavenge’ acid pollutants from the atmosphere, later releasing them into the soil via through fall and stem flow.
- Use of Inorganic fertilizers: Excessive use of inorganic nitrogen fertilizers in agricultural systems has also been associated with soil acidification, partly through the process of nitrification. This also reasults in agrichemicals pollution.
- Poor irrigation practice: An important cause of soil salinity is poor irrigation practice. Over-watering leads to a rise in the water table which, in turn, causes enhanced capillary action. Similarly, poor maintenance of irrigation channels and canals results in leakage of water into adjacent agricultural land. Further, intensive farming and the lack of crop rotation have an adverse effect on the quality of soil over time.
- Urban activities: Urban activities such as improper waste disposal, and building constructions pollute the soil by preventing proper drainage and increasing surface run-off. Some of the wastes include chemical wastes from residential areas and leaking sewerage systems. Human sewage and animal manure can pollute soil by changing its chemical composition.
- Solid waste: Plastics, cans and other solids count as soil pollution, too. Batteries and electrical goods can be particularly harmful as they contain chemicals such as lithium that leach into the soil.
- Burning fossil fuels: Air pollution can become soil pollution when greenhouse gases such as CO, SO, nitrous oxide and CO2 dissolve into the rain and then fall onto the soil, contaminating it with sulfides and nitrates.
Effects of soil pollution.
Soil pollution is a very serious problem throughout the world. Soil contamination has several negative impacts on the soil and the environment. These are some of the effects soil pollution:
- Poor crop output: Increased use of inorganic fertilizers, chemical fertilizers, as well as pesticides, eventually decreases the soil fertility at a faster rate. It also alter the soil structure. Reduced soil quality will lead to poor crop output. Soil can become less productive for growing crops in when it is heavily polluted.
- Unstable chemical composition: Different soil types naturally have different chemical compositions that are carefully balanced. The introduction of pollutants such as mercury or sulfides can destabilize this balance.
- Effect on ecosystem and biodiversity: Soil pollution can lead to the lack of biodiversity in an ecosystem. The life of bird, insect, mammal and reptile species who live in the soil can get affected by pollution. The soil is an important habitat.
- Effect on Human health: Living, playing or working on polluted soil can cause skin complaints, respiratory issues and other ailments. Drinking contaminated water as a result of surface run-off can also cause health problems.
- Contamination of water sources: When it rains, surface run-off carries contaminated soil into water sources causing water pollution. The contaminated water is thus unfit for both animal and human consumption. It will also affect aquatic life since the organisms that live in these water bodies will find their habitats inhabitable.
Soil pollution can have a devastating impact on plant and animal life, and as such it should be halted. If we act now, we can prevent soil pollution from taking hold. Some useful preventative measures that we can take to this end are listed below.
- Go organic: Organic agriculture uses much fewer chemical fertilizers and pesticides, preventing chemicals from seeping into the soil.
- Proper farming methods: Finding alternatives to chemical fertilizers and pesticides is an ideal way to avoid soil erosion. Rotational and mixed farming are also encouraged.
- Dispose of household waste responsibly: Recycling waste and not dumping it in landfill will keep the soil free of pollution. Not throwing batteries and electrical items into household waste bins will help to keep the soil free of dangerous chemicals.
- Prevent or Manage industrial waste: Properly managing industrial and domestic waste can help prevent soil erosion. Solid waste treatment is also a good preventive measure. Regular health and safety checks and adequate waste disposal methods will ensure that industrial chemicals and other waste are not allowed to contaminate our precious soil.
- Community Awareness: Creating awareness about the effects of soil pollution can help prevent its occurrence.
- Burn fewer fossil fuels: Cleaner air makes it easier for us to have cleaner soil. Fresh, pure rain will keep the soil free of pollutants.
Thus, we find that soil pollution is caused almost exclusively by human activity. Humans carelessly drop waste (which in itself tends to be a result of over-consumption: buying things that we do not need) and use harmful agricultural chemicals (such as pesticides and fertilizers) which can very easily (for instance as a result of rain or rivers flowing) soak into areas of land where they can cause harm to biodiversity.
Conserving the environment is important. Preventing soil erosion will contribute to a cleaner and healthier planet for this generation and those to come. It is vital for both businesses and private individuals to act now in order to prevent the phenomenon of soil pollution from driving beautiful plant and animal species to extinction and putting our supplies of food in jeopardy.
Updated with inputs from various contributors.