SOIL Pollution and THERMAL pollution, causes and effects

A fertile soil is capable of producing a large variety of plants, which are so important for supporting animal life. But soil has been subjected to various types of pollutants such as

(i) Pollutants that are washed out of atmosphere that are washed out of atmosphere

(ii) pesticides, insecticides and biocides, sprayed over the crops may find their way along with water to the soil

(iii) Nitrogenous fertilizers, mixed with soil to increase its productivity may sometimes have negative effect on the soil. Such soil pollutants destroy the natural structure and alter the chemical nature of the soil.

Soil erosion, unplanned irrigation, and deforestation also affect adversely the soil productivity. Soil Effect of heavy metal pollution on man

Metal Toxic effects

Fertility increases by absorption of water bound nutrients soil also helps the purification of water bound nutrients soil also helps the purification of waste water. Some of the solid wastes, such as garbage, trash, ashes, sludge, building materials rubble, empty bottles, etc. dumped on land may cause problems and some sort of soil pollution.

Pollutants that Contaminate Soil:

Some of the most hazardous soil pollutants are xenobiotics – substances that are not naturally found in nature and are synthesized by human beings. The term ‘xenobiotic’ has Greek roots – ‘Xenos’ (foreigner), and ‘Bios’ (life). Several xenobiotics are known to be carcinogens. An illustration detailing major soil pollutants is provided below.

Heavy Metals

The presence of heavy metals (such as lead and mercury, in abnormally high concentrations) in soils can cause it to become highly toxic to human beings. Some metals that can be classified as soil pollutants are tabulated below.These metals can originate from several sources such as mining activities, agricultural activities, electronic waste (e-waste), and medical waste.

Polycyclic Aromatic Hydrocarbon Polycyclic aromatic hydrocarbons (often abbreviated to PAHs) are organic compounds that:

• Contain only carbon and hydrogen atoms.
• Contain more than one aromatic ring in their chemical structures.
• Common examples of PAHs include naphthalene, anthracene, and phenalene. Exposure to polycyclic aromatic hydrocarbons has been linked to several forms of cancer. These organic compounds can also cause cardiovascular diseases in humans.
• Soil pollution due to PAHs can be sourced to coke (coal) processing, vehicle emissions, cigarette smoke, and the extraction of shale oil.

Industrial Waste:

The discharge of industrial waste into soils can result in soil pollution. Some common soil pollutants that can be sourced to industrial waste are listed below.

• Chlorinated industrial solvents
• Dioxins produced from the manufacture of pesticides and the incineration of waste.
• Plasticizers/dispersants
• Polychlorinated biphenyls (PCBs)
• The petroleum industry creates many petroleum hydrocarbon waste products. Some of these wastes, such as benzene and methylbenzene, are known to be carcinogenic in nature.

Soil pollution can be broadly classified into two categories –

• Naturally caused soil pollution
• Anthropogenic soil pollution (caused by human activity)

Natural Pollution of Soil:

• In some extremely rare processes, some pollutants are naturally accumulated in soils. This can occur due to the differential deposition of soil by the atmosphere. Another manner in which this type of soil pollution can occur is via the transportation of soil pollutants with precipitation water.
• An example of natural soil pollution is the accumulation of compounds containing the perchlorate anion (ClO4–) in some dry, arid ecosystems. It is important to note that some contaminants can be naturally produced in the soil under the effect of certain environmental conditions. For example, perchlorates can be formed in soils containing chlorine and certain metals during a thunderstorm.

Anthropogenic Soil Pollution:

• Almost all cases of soil pollution are anthropogenic in nature. A variety of human activities can lead to the contamination of soil. Some such processes are listed below.
• The demolition of old buildings can involve the contamination of nearby soil with asbestos.
• Usage of lead-based paint during construction activities can also pollute the soil with hazardous concentrations of lead.
• Spillage of petrol and diesel during transportation can contaminate soils with the hydrocarbons found in petroleum.
• Activities associated with metal casting factories (foundries) often cause the dispersion of metallic contaminants into the nearby soils.
• Underground mining activities can cause the contamination of land with heavy metals.
• Improper disposal of highly toxic industrial/chemical waste can severely pollute the soil. For example, the storage of toxic wastes in landfills can result in the seepage of the waste into the soil. This waste can go on to pollute groundwater as well.
• Chemical pesticides contain several hazardous substances. Excessive and inefficient use of chemical pesticides can result in severe soil pollution.
• Sewage produced in urbanized areas can also contaminate soil (if not disposed of correctly). These wastes may also contain several carcinogenic substances.

Effect of soil pollution in human beings:

Soil contaminants can exist in all three phases (solid, liquid, and gaseous). Therefore, these contaminants can find their way into the human body via several channels such as direct contact with the skin or through the inhalation of contaminated soil dust.

The short term effects of human exposure to polluted soil include:

• Headaches, nausea, and vomiting.
• Coughing, pain in the chest, and wheezing.
• Irritation of the skin and the eyes.
• Fatigue and weakness.

A variety of long-term ailments have been linked to soil pollution. Some such diseases are listed below.

• Exposure to high levels of lead can result in permanent damage to the nervous system. Children are particularly vulnerable to lead.
• Depression of the CNS (Central Nervous System).
• Damage to vital organs such as the kidney and the liver.
• Higher risk of developing cancer.

It can be noted that many soil pollutants such as petroleum hydrocarbons and industrial solvents have been linked to congenital disorders in humans. Thus, soil pollution can have several negative effects on human health.

Effects on Plants and Animals

Since soil pollution is often accompanied by a decrease in the availability of nutrients, plant life ceases to thrive in such soils. Soils contaminated with inorganic aluminium can prove toxic to plants. Also, this type of pollution often increases the salinity of the soil, making it inhospitable for the growth of plant life.

Soil Pollution can be Controlled:

• Several technologies have been developed to tackle soil remediation. Some important strategies followed for the decontamination of polluted soil are listed below.
• Excavation and subsequent transportation of polluted soils to remote, uninhabited locations.
• Extraction of pollutants via thermal remediation – the temperature is raised in order to force the contaminants into the vapour phase, after which they can be collected through vapour extraction.
• Bioremediation or phytoremediation involves the use of microorganisms and plants for the decontamination of soil.
• Mycoremediation involves the use of fungi for the accumulation of heavy metal contaminants.

Thermal pollution

The term thermal pollution has been used to indicate the detrimental effects of heated effluent discharge by various power plants. It denotes the impairment of quality and deterioration of aquatic and terrestrial environment by various industrial plants like thermal, atomic, nuclear, coal-fired plants, oil field generators, factories, and mills.

Sources of Thermal Pollution:

1. Nuclear Power Plant

2. Coal-fired power Plant

3. Industrial Effluents

4. Domestic Sewage

5. Hydro-electric power

6. Thermal Power Plant

The discharged effluents of these sources have a higher temperature than the intake water that reduces the concentration of oxygen from the water which causes the deleterious effects on the marine ecosystem.

Harmful Effects of the Thermal Pollution:

The harmful effects of the thermal pollution are discussed below:

• Reduction in dissolved Oxygen: The pollutant from various industrial plants are heated decreases the concentration of oxygen with an increase in the temperature of water.
• Change in water properties: The decrease in density, viscosity and solubility of gases in water increases the setting speed of suspended particles which seriously affect the food supplies of aquatic organism.
• Increase in toxicity: The concentrated pollutant causes the rise in the temperature of water which increases the toxicity of the poison present in water. The toxicity in water will increase the death rate in marine life.
• Disruption of Biological activities: Temperature changes disrupt the entire marine ecosystem because changes in temperature causes change in physiology, metabolism and biological process like respiration rate, digestion, excretion and development of an aquatic organism.
• Damage of biotic organism: Aquatic organisms like juvenile fish, plankton, fish, eggs, larva, algae and protozoa which pass through screens and condenser cooling system are extremely sensitive to abrupt temperature changes. They are habitual of warmer water may suddenly face increase or decrease in temperature of water bodies and thus die because of sudden changes in the temperature of water.

Thermal pollution can be prevented

The following measures can be taken to prevent or control high temperature caused by thermal pollution:

• Heated water from the industries can treated before discharging directly to the water bodies.
• Heated water from the industries can be treated by the installation of cooling ponds and cooling towers.
• Industrial treated water can be recycled for domestic use or industrial heating.
• Through artificial lakes: In this lake Industries can discharge their used or heated water at one end and water for cooling purposes may be withdrawn from the other end. The heat is eventually dissipated through evaporation.

Hence, we can say any kind of pollution may directly or indirectly affect humans because the loss of biodiversity causes changes that affect all the aspects of the environment.....