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INEP: We now hear that even soil can get polluted. Whatis the scientific definition of soil?Mr. Srinivas: The top portion of the earth is called soil. Itis a product of disintegration of rocks. Over severalthousand years, the rocks get emaciated, then break andover a long period time reduce to a powder state whichcan be called soil. It is as important as water and air.

INEP: What does it contain?Dr. Bakul Rao: It contains sand, pieces of rocks andwhatever nutrients the parent rock contained.

INEP: So, over a period of years rocks have become soildue to climatic and chemical reaction. How come it hasdifferent colours?Mr. Srinivas: Broadly it can be classified as red soil, redsand soil, clay and black soil. The last one, available inNorth Karnataka region, is conducive to grow cotton. Claysoil is mostly available in Dakshina Kannada and coastalregions and is used to make idols.

Red soil is available in Bangalore, Kolar, Tumkur andMysore districts and in parts of Hassan, Chikmagalur andChitradurga. These regions get a rainfall of 600-900 mm

and this aspect largely decides the colour of the soil. Redsand soil is available in Mandya district, especially in theVisvesvarayya canal region, portions of Bangalore, Kolar,Tumkur, Chitradurga, and Bellary and in the borderregions of Karnataka- Andhra Pradesh.

Clay soil is visible in Malnad regions like Kodagu,Chikmagalur and a part of Hassan where the annualrainfall is around 2000 to 8000 mm.

Black soil is available in North Karnataka regions likeBidar, Bijapura, Belgaum, Dharwad, Raichur, Bellary,northern portions of Chitradurga, portions of Mysore andChamarajnagar, where the rainfall varies between 300to 500mm.

INEP: Thank you very much for the vital information. Nowtell us, how does soil get polluted?Dr. Bakul Rao: There are two types of soil pollution. Oneis the natural process- the degradation of soil over millionsof years. Seawater infiltration in coastal region,acidification of soil, siltation and soil erosion are thenatural process of degradation of soil.

Soil pollution

Soil pollution like the pollution of air and water, can be dangerous.Dr. Bakul Rao and Mr. V Srinivas, Environment Policy Research Institute,explain the phenomenon and suggest remedies.

Great need to avoid soil pollution

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The second one isthe man-madepollution. Defor-estation is a majorfactor of man-madepollution of soil.Sewage can pollutethe soil. Use ofinorganic manureand pesticides canpollute the soil.Quarrying andtransport of sand canpollute the soil.

INEP: We know the factors that pollute the soil. Howexactly does pollution occur?Mr. Srinivas: Soil erosion and siltation are interlinked.Wind can cause erosion and so also the rain. Soil losesits top layer and it reaches ponds, tanks and lakes. Thefine soil is called silt. This is a natural process ofdegradation. Coming to man-made pollution,indiscriminate deforestation makes soil lose its protectionfrom sun, wind and water. When the topsoil is lost thearea loses its precious nutrition that is developed overcenturies. Trees and plants would have absorbed thesenutrients. When trees are cut, nutrients are washed awayto water bodies. This results in unwanted weeds, whichif unchecked, can cover the entire tank and suffocate it.

Constant infiltration of salt water from sea can makecoastal regions infertile. The ground water in theseregions becomes unpotable due to salinity.

Effluents and sewage can pollute the inner layers of soil.The topsoil acts like a sponge. It absorbs and retains

water. When it cannot hold the water any longer, the watersinks deeper into the soil, leaving only the toxins in thetop layer of soil.

The solids in sewage have the same effect on soil aseffluents. Effluents have cancer-causing properties. Whenit reaches subsoil it is difficult to eliminate such toxins.The sewage waste can carry harmful bacteria that maypollute both water and soil.

Then there are products like plastics and unwanted solidwastes. Plastic is non-bio-degradable and survives in soilfor years. Plastic prevents a suitable aeration of soil. Thiskills useful bacteria and the soil around that regionbecomes useless.

INEP: So, soil erosion and soil pollution are interlinked.Dr. Bakul Rao: The purpose of soil is to provide nutrientslike calcium, magnesium and micro-nutrients to plantsand trees. If the topsoil is blown away by wind or washedaway by water, we lose nutrients where we need thembut it goes to tank beds where it is not desired. This leadsto acute shortage of precious top soil.

INEP: Do you differentiate between the pollution in ruraland urban regions?Mr. Srinivas: This is a very relevant question. There isthis feeling that pollution is less in rural areas. In urbanareas the sewage from City Corporation and effluentsfrom industries can be traced to one region, which canbe called as a One Point Source. If the point source isidentified it is easy to treat it.

In rural regions everyone uses fertilisers and pesticidesand they are all over the place. It is spread over a largearea. The source of pollution is not at one point. Hence,

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it is difficult to treat pollution in rural regions. But we cannotdifferentiate between urban and rural regions’ pollution.We have to consider it as a major problem and tackle it.

INEP: What sort of activities in rural regions cause soilpollution?Dr. Bakul Rao: Agricultural activities in rural regions arethe main cause for pollution. Use of inorganic manuresand pesticides destroys the fertility of soil and makes ituseless. Plants retain the toxins in fertilisers andpesticides. When plants die and decompose the toxiccontents remain in the soil making it unusable foragriculture.

Pesticides are found mostly in three formats: herbicides,insecticides, and fungicides. Fungicides can destroy bigweeds. Herbicides destroy bigger weeds. Insecticides areused to destroy unwanted insects, flies and othercreatures.

Plants absorb only 5% of the pesticides and sprays. Therest is absorbed by the soil. The toxic contents of thesepesticides remain in soil for years because they are notbiodegradable. They can affect human beings also.

INEP: How do mining activities pollute soil?Mr. Srinivas: Even before mining activities begin, thetopsoil is removed. This topsoil, which is a very importantlayer of the earth, is not preserved in one place butdumped all over. Thus the soil nutrients are wasted.

INEP: Can’t we use that dumped topsoil?Dr. Bakul Rao: Afforestation can help. Trees can begrown on this displaced topsoil. Otherwise, the topsoil isjust wasted during the rains and other natural calamities.

INEP: It is said that road accidents too pollute soil. Is ittrue?Mr. Srinivas: There are two types of accidents. The firstone is when petrol- or diesel-run vehicles are involved inan accident. The petrol or diesel falls on soil and damagesthe soil. Even the leak of the tank can damage the soil.The second category is tankers carrying chemicals andother inflammable substances. In case of an accident,the chemicals can burn the soil, as they are highlyconcentrated. Once the soil is burnt it is useless for anypurpose. Not even grass can grow on such places.

Once, a tanker turned turtle on the high way near Mumbai.Residents rushed to the spot assuming that it carriedpetrol which they could salvage. But the tanker carriedconcentrated sulphuric acid and many persons werecharred to death when the tanker burst. In such casesalso soil gets charred. This is a very high level of pollution.

INEP: How strange! We always worry about humanbeings dying or getting injured during accidents. We donot worry about damage to the environment.Dr. Bakul Rao: You can notice that the soil in and aroundpetrol bunks are black due to splash of oil, petrol anddiesel. You do not notice even a blade of grass in thoseregions. Moreover the surroundings of petrol bunks areconcretised. This is also one of the reasons why wecannot see any greenery near petrol bunks.

INEP: It is heartening that the owner of a petrol bunk inDharwad town has created a separate ‘Green House’near the bunk. People can contribute their mite to protectenvironment even if it is a small gesture. Can this pollutedsoil be treated and used again?Mr. Srinivas: Construction of check dams or earth damsis one way of preventing soil erosion. Trenches can bedug on sloppy regions and afforestation programme can

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be taken up in these regions. Water and the top soil canbe retained with the help of such programmes.Another way is to adopt organic farming method wherenatural manure is used. We have a tradition of not usingchemicals and fertilisers, but in the last 50 years we havelost the indigenous knowledge. This has causedimmense pollution of the soil and suffering to humans.We have to return to our traditional way of farming. Wecan control pests by methods like crop rotation and inter-cropping.

We are using inorganic materials in such large proportionsthat farmers in Punjab feel that they cannot grow anythingwithout the use of fertilisers. Crops grown with the useof chemicals and fertilisers are sold to the market. Forpersonal consumption farmers use the grains that aregrown the organic way!

In urban areas we can adopt waste management method.Segregation of waste in the primary level itself is a verygood method. The biodegradable waste can beseparated from paper, plastic, glass and metals bykeeping them in two dustbins. The organic waste canbe turned into compost manure that is highly useful forthe plants. The inorganic wastes can be recycled andused. This segregation helps the Mahanagara Paliketoo. We can also prevent choking of sewage pipes,especially during rainy season if we segregate wastes.The inorganic material can be used for filling up the pitsand other uneven surfaces. This becomes ourcontribution and duty towards saving the environment.

But the general public cannot prevent industrial effluentsreaching tanks. The process is highly technical andneeds guidance.

Student: Howcan we preventsoil erosion?Dr. Bakul Rao:Largely bya g r i c u l t u r a lactivities and byc o n s t r u c t i n gcheck dams.Mining andquarrying shouldbe a pre-plannedactivity andshould becarried out withinthe permissiblelimits.

Student: What happens to soil when we throw plasticmaterials?Mr. Srinivas: Plastics are non-biodegradable objects thatdo not decompose and merge with the soil. They preventaeration of soil that kills useful bacteria. Some of themare cancer-causing chemicals, which severely affect thesoil.

Student: How does change takes place in soil?Dr. Bakul Rao: It takes centuries and largely dependson rainfall. As rainfall varies from place to place, thechange also varies from place to place.

Soil erosion