• Soil Pollution—Sources of Soil Pollution
Pesticides: It can be classified as:
(i) Insecticide: The most common insecticides are chlorinated hydrocarbons like DDT, BHC etc.
As they are not much soluble in water, they stay in the soil for long time. They are ‘ absorbed by the soil and contaminate root crops like radish, carrot etc.
(ii) Herbicides: These are the compounds used to control weeds, namely, sodium chlorate (NaCl03) and sodium arsenite (Na3As03) are commonly used herbicides but arsenic compounds, being toxic are no longer preferred.
Fungicides: Organo-mercury compounds are the most common fungicides. Its dissociation in soil produces mercury which is highly toxic and harmful for the crops. i Industrial Waste: It has seen that most of the industrial wastes are thrown into water or dumped into the soil. These industrial wastes contain huge amounts of toxic chemicals which are mostly non-bidegradable. For example, metal processing industries, mining cement, glass industries, petroleum industry etc., fertilizer industry produce gypsum.
The disposal of non-biodegradable industrial solid waste is not done by suitable methods i and cause many serious problems.
Strategies to control environmental pollution:
(i) The improper disposal of wastes is one of the major causes of environmental degradation. The management of wastes is very important.
(ii) All domestic wastes should be properly collected and disposed.
Green Chemistry is a way of thinking and is about utilising the knowledge and principles of
chemistry that would control the increasing environmental pollution.
Green chemistry in day-to-day life:
(i) Dry-Cleaning of clothes and laundary:
Tetra chlroroethene was earlier used as solvent for dry cleaning. The compound contaminates the ground water and is also a suspected carcinogen. The process using this compound is now being replaced by a process, where liquefied carbon dioxide, with a suitable detergent is used. Replacement of halogenated solvent by liquid CO2 will result in less harm to ground water. These days hydrogen peroxide (H2O2 ) is used for the purpose of bleaching clothes in the process of laundary, which gives better results and makes use of lesser amount of water.
(ii) Bleaching of Paper:
Chlorine gas was used earlier for bleaching paper. These days, hydrogen peroxide (H2O2 ) with suitable catalyst, which promotes the bleaching action of hydrogen peroxide, is used.
(iii) Synthesis of Chemicals
Ethanal is now commercially prepared by one step oxidation of ethene in the presence of ionic catalyst in aqueous medium with a yield of 90%.
(iv) ‘Green Solution’ to Clean Turbid Water
Powder of kernel of tamarind seeds has been found to be an effective material to make municipal and industrial waste water clean. It is non-toxic, biodegradable and cost effective material. This powder is usually discarded as agricultural waste. The present practice is to use alum to treat such water. It has been found that alum increases toxic ions in treated water and can cause diseases. Green chemistry, in a nutshell, is a cost effective approach which involves reduction in material, energy consumption and waste generation.