Environmental Studies

Dr Anupam Agarwal

Composition of Soil:•Soils are a mixture of different things; rocks, minerals, and dead, decaying plants and animals.•Soil is the thin layer of organic and inorganic materials that covers the Earth's rocky surface. •The organic portion, which is derived from the decayed remains of plants and animals, is concentrated in the dark uppermost topsoil.• The inorganic portion made up of rock fragments, was formed over thousands of years by physical and chemical weathering of bedrock. •Productive soils are necessary for agriculture to supply the world with sufficient food.

Soil pollution • Soil Pollution is the introduction of

substances, biological organism, or energy into the soil resulting in a change in soil quality.

• Any factor which deteriorates the quality, texture and mineral content of the soil or which disturbs the biological balance of the organisms in the soil.

Cause of Soil Pollution:• Pesticides, fertilizers, organic manure, chemicals,

radioactive wastes, discarded food, clothes, leather goods, plastics, papers, bottles, tin cans and car cases all contribute towards causing soil pollution

• Human and animal excreta used as organic manure to promote crop yield, pollute the soil by contaminating the soil and vegetable crops with the pathogens that may be present in the excreta.

• Organic insecticides like DDT, aldrin, benzene hexa chloride etc are used against soil borne pests. They accumulate in the soil as they degrade very slowly by soil and water bacteria.

• Soil Erosion occurs when the weathered soil particles are dislodged and carried away by wind or water.

• Deforestation, agricultural development, temperature, extreme precipitation including acid rain, and human activities contribute to this erosion.

Effects of Soil Pollutant

• Pollution in soil has adverse effect on plant growth • Reduced soil fertility• Reduced nitrogen fixation• Increased erodibility• Larger loss of soil and nutrients• Dangerous chemicals entering underground water• Ecological imbalance• Increased salinity• Reduced vegetation

• Public health problems• crops and fodder grown on polluted soil may

pass the pollutants on to the consumers• Pollution of drinking water sources• Foul smell and release of gases

Control of Soil Pollution

1.Use of pesticides should be minimized.2. Use of fertilizers should be judicious. 3. Cropping techniques should be improved to prevent growth of weeds.4. Special pits should be selected for dumping wastes. 5.Everybody should adopt 3R’s : Reduce, Reuse,

Recycle.

Bioremediation

• Bioremediation defined as the process that uses microorganisms (bacteria, fungi or yeast) to breakdown or degrade, hazardous substances into less toxic or non toxic substances (carbon dioxide or water)

• Bioremediation may be employed in order to attack specific contaminants, such as chlorinated pesticides that are degraded by bacteria, or a more general approach may be taken, such as oil spills that are broken down using multiple techniques including the addition of fertilizer to facilitate the decomposition of crude oil by bacteria.

Types of Bioremediation

• In situ Bioremediation: In situ bioremediation involves treating the contaminated material at the site

• Ex situ Bioremediation: ex situ involves the removal of the contaminated material to be treated elsewhere.

• Some examples of bioremediation technologies are bioventing, land farming, bioreactor, composting, bioaugmentation and biostimulation.

• Condition that favour bioremediation include the following:

• Temperature favorable for organism• Availability of water• Availability of N,P,K• C:N ratio of the contaminant material• Availability of oxygen in sufficient quantity in

the soil

Composition of Soil