Soil pollution is of two main types
(a) `text(Negative soil pollution)`
(b) `text(Positive soil pollution)`
(a) `text(Negative soil pollution)` -
(i) It includes over use of soil and erosion.
(ii) Soil erosion is caused by water and wind.
(iii) Water erosion of soil is found near the hills where high speed flooding removes top soil.
(iv) Soil erosion also occurs by high speed winds which bring sand particles from dry desert.
(b) `text(Positive soil pollution)`- It is caused by addition of undesirable substances (eg. pesticides, fertilizers, industrial waste, air pollutant washed down from atmosphere through rain)
`text[(A) Pesticides]` -
(i) These include insecticides (kill insects), fungicides (kill fungi), algicides(kill algal blooms), weedicides or herbicides (kill weeds), rodenticides (kill rodents).
(ii) Pesticides are generally broad-spectrum and affect other animals, man and even plants. They are hence, also called `text(biocides)`.
(iii) DDT (dichloro diphenyl trichloroethane), BHC (benzene hexachloride or gamaxine), aldrin, dieldrin, endrin, heptachlor etc. are chlorinated hydrocarbons used as pesticides.
(iv) Dieldrin is five times more toxic than DDT when ingested and `40` times more poisonous when absorbed.
(v) Endrin is the most toxic amongst chlorinated hydrocarbons.
`text[(B) Fertilizers]`-
(i) The fertilizers contain plant nutrients particularly `N`, `P` and `K`, but the soil also gets polluted mainly due to organic pollutants present as impurities.
(ii) Excessive use of fertilizers cause soil deterioration through decrease of natural microflora (nitrogen fixing, nitrifying bacteria).
(iii) Fertilizers added to soil enter the crop plants. Nitrogen fertilizers produce toxic concentration of nitrate in the leaves and fruits. When these leaves and fruits are eaten, nitrates changed into nitrites by the activity of bacteria in the alimentary canal. The nitrites enter the blood and combine with haemoglobin to form methaemoglobin. As a result oxygen transport is reduced. It gives rise to disease known as methaemoglobinaemia. In infants it produces cyanosis (blue baby syndrome)
`text[(C) Industrial wastes]`-
(i) Wastes of the industries are dumped over the soil. They contain a number of toxic substances including cyanides, acids, chromates, alkalies and metals like mercury, copper, zinc, lead, cadmium etc.
(ii) The industrial pollutants increase the toxicity level of the soil.
(iii) Heavy metals destroy useful micro organisms of the soil.
(iv) In `1970` some `200` people died in Japan by `Cd` pollution of soil due to itai-itai disease.
Soil pollution is of two main types
(a) `text(Negative soil pollution)`
(b) `text(Positive soil pollution)`
(a) `text(Negative soil pollution)` -
(i) It includes over use of soil and erosion.
(ii) Soil erosion is caused by water and wind.
(iii) Water erosion of soil is found near the hills where high speed flooding removes top soil.
(iv) Soil erosion also occurs by high speed winds which bring sand particles from dry desert.
(b) `text(Positive soil pollution)`- It is caused by addition of undesirable substances (eg. pesticides, fertilizers, industrial waste, air pollutant washed down from atmosphere through rain)
`text[(A) Pesticides]` -
(i) These include insecticides (kill insects), fungicides (kill fungi), algicides(kill algal blooms), weedicides or herbicides (kill weeds), rodenticides (kill rodents).
(ii) Pesticides are generally broad-spectrum and affect other animals, man and even plants. They are hence, also called `text(biocides)`.
(iii) DDT (dichloro diphenyl trichloroethane), BHC (benzene hexachloride or gamaxine), aldrin, dieldrin, endrin, heptachlor etc. are chlorinated hydrocarbons used as pesticides.
(iv) Dieldrin is five times more toxic than DDT when ingested and `40` times more poisonous when absorbed.
(v) Endrin is the most toxic amongst chlorinated hydrocarbons.
`text[(B) Fertilizers]`-
(i) The fertilizers contain plant nutrients particularly `N`, `P` and `K`, but the soil also gets polluted mainly due to organic pollutants present as impurities.
(ii) Excessive use of fertilizers cause soil deterioration through decrease of natural microflora (nitrogen fixing, nitrifying bacteria).
(iii) Fertilizers added to soil enter the crop plants. Nitrogen fertilizers produce toxic concentration of nitrate in the leaves and fruits. When these leaves and fruits are eaten, nitrates changed into nitrites by the activity of bacteria in the alimentary canal. The nitrites enter the blood and combine with haemoglobin to form methaemoglobin. As a result oxygen transport is reduced. It gives rise to disease known as methaemoglobinaemia. In infants it produces cyanosis (blue baby syndrome)
`text[(C) Industrial wastes]`-
(i) Wastes of the industries are dumped over the soil. They contain a number of toxic substances including cyanides, acids, chromates, alkalies and metals like mercury, copper, zinc, lead, cadmium etc.
(ii) The industrial pollutants increase the toxicity level of the soil.
(iii) Heavy metals destroy useful micro organisms of the soil.
(iv) In `1970` some `200` people died in Japan by `Cd` pollution of soil due to itai-itai disease.