Before embarking upon the subject of water pollution by pesticides, one must understand water. Water molecules are covalent bonds of two atoms of oxygen and one atom of Hydrogen. Nearly 71% of earth's surface is covered by water. Most of the water is resident in oceans. Only 1.6% water can be found in below ground surface aquifers, 0.6% are available on surface land such as rivers, lakes and ponds and 0.001% in the atmospheric air as clouds, vapour and precipitation. Water is bounded by a cycle of evaporation, precipitation and runoff via storm drains, streams and rivers to ultimately end up into the sea.
Water is an essential component after air for survival and prospering of all flora and fauna of the earth. In human surroundings, water is available in basically four varieties. Drinking water is available naturally in most of the rivers and streams if not contaminated by domestic and industrial effluents. One important point to note is that the moving water gets cleaned by leaving behind its suspended particulates coalescence with bottom muck or silt and further cleaned by sandy particles present in the channels and stream. Moreover, minerals with medicinal and purifying properties encountered in their way forward make the water safe for drinking purpose sometimes better than synthetically cleaned drinking water. The second variety is the process water. This is mechanically cleaned water used for industrial purpose and as domestic water fit for washing, gardening and farming. Next is biodegradable effluent water. This is industrial effluent which gets treated and cleaned to mandatory norms before its release into the land surface or water bodies. The last is non-biodegradable effluent water from factories which are again to be statutorily cleaned and treated before being discharged.. Effluent containing pesticides fall in the bio and non-bio-degradable category.
Pesticide may be a chemical compound, biological virus or bacterium or disinfectant used for preventing, mitigating or repelling pest infestation. Pests such as plant pathogens, insects, weeds, molluses, birds, fish, mammals, nematodes and microbes spread disease or cause loss to the property. Here again, we are faced with advantages of using pesticides as well as disadvantages of causing pollution in almost equal proportion. Only 3-5% pesticides in the form of insecticides and herbicides are effectively administered. The rest 95-97% boomerang upon us through land produce, water bodies and atmospheric fallouts. Some of the identified channels are as under:-
* Manufacturing industries generate solid waste rich with pesticides rejects. Carelessly disposed pesticide waste gets leached with the falling water. Improperly treated effluent also reaches water bodies. Vapour/particulates emissions fall down on earth with rain water and get deposited in water bodies.
* Pesticides treated agricultural fields run off excess pesticides into nearest water bodies.
* Excess or expired pesticides discarded in inappropriate manner without adhering to pollution control norms, either flows with the stream or get leached into the land surface from where it find its way to water bodies..
* Aerial spray drifting with air to unintentional targeted area and species.
* Sprayed into water bodies to destroy algae.
Physical and chemical properties of a particular pesticide is also instrumental in polluting water such as its biodegradability, binding strength, solubility, vapour pressure, texture, water retention characteristic and organic matter content. Apart from its properties, excess pesticides spraying may also lead it to the water bodies. Smaller the route, better are the chances. Pesticides sprayed in excess may percolate or leach through the soil. It may flow with other effluents or storm water as runoff. Accidental or negligence spillage may also have the same fate. Pesticides impregnated in eroding soil may be carried away to the water body.
It has been found that pesticide run off has killed all the fish in a particular pond or stream. Herbicides administered into the water body to mitigate wild growth such as algae are also quite dangerous. Excess destruction of aquatic plants may deplete food resource of the fishes. The dead aquatic plants start rotting depleting oxygen content of water technically termed as "Biological Oxygen demand". If fish does not suffer fatality then there is greater chance that these pesticides may harm indirectly. The fish may abandon their nesting and brooding zone hence reducing population. It may decrease immunity to fight disease. The fish may lose its reflexes and become a predator's delight. The amphibians are also suffering due to effect of pesticides on water bodies. Ponds are the nearest of all the water bodies and is dependent upon "water seeks its own level "mechanism. Therefore, pesticides enriched water from household kitchen garden, farms and agricultural fields and even from washings from grain storage reach nearby ponds. The most comfortable resort of tadpoles is the pond and murky land. It has been found that due to pesticides enriched water in the ponds, tadpoles take more time to transit into frogs and the frogs are losing their size lately.
Effect of pesticides on water can be drastically reduced to a minimum acceptable limit by following the under mentioned guidelines:-
1. Manual removal of weeds and pests.
2. Prevention of pest breeding sites.
3. Applying heat by creating glass room effect.
4. Use of traps and lures to catch pests.
5. Use of compost, vermin-compost to make the soil healthy.
6. Use of green pesticide such as preparations from Neem tree (Azadirachta indica).There are several green pesticides available in the market and online with details such as Wormwood extract, Summer tansy dust, Chive extract, Daffodil extract, Stinging nettle extract, Garlic extract, Rhubarb extract, Onion extract, Stale beer, Sambucus extract and Tobacco extract.
One must understand that each and every action has its opposite reaction. Newton's third law of motion is valid universally. What good, bad and ugly we are doing to the environment, boomerang upon us in equal proportions. Only we, ignorant, presume that these are natural fallout. Pesticides reach us by one way or the other; food that we eat, water that we drink and the air that we breathe. Since majority of synthetically manufactured chemical pesticides are non-bio-degradable, the portion reaching our stomach and the intestine gets permanently deposited in the body. If it contains heavy metals too then our vital organs may get impaired. According to one research, pesticides are 10 of the 12 most persistent and dangerous organic chemicals.
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