Contents
Evolutionary Biology Topics allow us to trace the history of life on Earth.
Solid Waste Management & Radioactive Waste Management – Types with Methods and Its Effects
Agrochemicals include mainly pesticides, weedicides, and chemical fertilizers. The impact of the environment is much greater than merely killing pests or weeds. Over 98% of sprayed insecticides and 95% of weedicides affect not only their target species but also the non-target species, air, water, groundwater, and food. The benefits of using pesticides get overlooked by the harm they cause. Inappropriate of these chemicals can have long and short-term risks about which awareness is limited among people. These toxic chemicals can contaminate non-target land and water bodies if sprayed aerially or can run off or leach into other sources of water causing pollution.
1. Pesticides
Different types of pesticides are insecticides, fungicides, weedicides, rodenticides, nematicides, etc. Pesticides are generally broad-spectrum and are called biocides. Along with the target organism, they harm many other organisms as well. Many of them are also persistent. They can increase resistance to pests and kill their natural enemies in return. Such an effect is called ecological boomerang or ecological backlash. These pesticides can migrate from the area where it is applied to an unintended area through air, water, or any other means. The pesticides can be of the following types:
- Organochlorines/Chlorinated hydrocarbons i.e., DDT, BHC, Aldrin, Endrin, etc., are persistent and show biomagnification. Their use is therefore restricted.
- Organopesticides i.e., malathion, parathion, carbamates, etc., are degradable but have toxic effects on the workers.
- Inorganic pesticides are compounds containing sulfur, copper, and arsenic. They are persistent hence, their use is highly restricted.
- Weedicides like 2,4-D; and 2,4,5-T are selective metabolic inhibitors.
2. Fertilizers
Fertilizer is any organic or inorganic prepared naturally or artificially that is added to the soil to supply nutrients to the plant. The most widely used fertilizers are super phosphates which provide all the essential nutrients to the plant like nitrogen, magnesium, phosphates, etc. However most people do not have the knowledge of the correct amount of fertilizer to be applied, so the most common effect encountered is the fertilizer burn’ effect, where the leaves show a drying effect when excess fertilizer is applied, which can ultimately lead to death of the plant. Super phosphates, after prolonged use, can also cause sterilization of soil, destruction of soil microflora, depletion of normal nutrients of the soil, salination of soil, and deterioration of soil’s natural qualities.
Effects of Agrochemicals
The agrochemicals if used unjudicially cause great harm to the environment including plants and animals. The major harms caused by these chemicals are:
Effects on Air:
Pesticides contribute a great share of air pollution. Many volatile pesticides when sprayed out the crops drift in the air and are carried away to non-target areas. The velocity of wind, temperature, and relative humidity determine the amount of sprayed pesticide evaporation. Also, droplets of sprayed pesticides and particles of pesticide dust can become suspended in the air and inhaled by animals and human beings. This can cause severe respiratory problems in humans. The pesticides that are applied to the fields to fumigate soil give off volatile organic compounds which react with other chemical reactions to form secondary pollutants like Ozone (O3). Pesticides contribute about 6% to the production of tropospheric ozone.
Effects on Water:
Pesticides and chemical fertilizers are not directly added to any water body, except weedicides. The major routes through which these chemicals reach the water bodies are:
- It may be suspended in air and come down into water bodies along with rain.
- It may run off from the fields where applied along with rain water and eroded soil.
- It may percolate through the soil by leaching.
- It may get spilled accidentally while being transported.
The main effect it has is on aquatic plants and animals. The toxicity of these chemicals not only kills aquatic life but also is transmitted to organisms of higher trophic levels due to the effect of bioaccumulation and biomagnification.
Effects on Soil:
Pesticides mainly contaminate the soil, whose effects may be long-term. It causes severe degradation of soil microflora leading reduction in organic matter content; low organic matter also lowers the water-holding capacity of the soil. Further, bioaccumulation of chemicals causes the depletion of farmer-friendly organisms like earthworms. Thus, the incorporation of pesticides affects the quality of soil and also causes pest resistance.
Effects on Plants and Animals:
Pesticides like DDT, methyl parathion, and pentachlorophenol highly hinder the nitrogen fixation ability of plants. It interferes with the chemical signaling between the Rhizobium bacteria and legumes of roots. Pesticides or fertilizer when sprayed onto bloomed flowers are ingested by the honey bees along with nectar and have resulted in the abrupt decline of the chief pollinator organism, honey” bees. This is termed a colony collapse disorder. This has again resulted in a great reduction in crop pollination and thus yield.
Effects on Humans:
The human body can be affected by pesticides through inhalation of aerosols, vapour, or dust-containing pesticides, through direct contact with these, through foods and vegetables sprayed with these, and by drinking groundwater polluted with them. Children are most susceptible to pesticides as they have weaker immune systems. Children below the age of 6 months can also get exposed through their mother’s milk. The major effects of such toxic chemicals may range from minor skin irritations to tumors, genetic disorders, birth defects, nerve disorders, and even coma or death. Pesticides are genotoxic to humans, causing cancers. These can even cause reproductive sterilization in human males and females.
Pest Resistance and Secondary Pest Outbreaks:
Though pesticides are employed to kill and eradicate pests, prolonged use of these chemicals can induce evolution in the pests and make them resistant to the same. As these chemicals kill and affect many non-target organisms too, predators for the target insect species may also get killed and eradicated. Loss of predators provides a scope for the target pests to proliferate and thus they rebound. These effects are known as secondary outbreaks. In some cases, it was seen that the pest population after they rebounded was higher than it was before the use of pesticides.
Solid Waste Management
The discarded or leftover solid materials from various sources are called solid wastes. The various sources of solid waste are municipal waste, industrial waste, hospital waste, mining waste, electronic waste, and others. They include heavy metals, toxic chemicals, and pathogens. They cause adverse effects on human health, animals, and plants in various ways.
1. Municipal Wastes:
The main sources are homes, shops, schools, and street sweepings. It may include mostly of waste papers, textiles, metals, glass, plastics, food wrappings, etc.
2. Industrial Wastes:
It includes effluents, sludge, scrap, and fly ash. Flyash comes from thermal plants. It contains oxides of silica, aluminum iron, and other heavy metals.
3. Mining Wastes:
Such wastes consisting of mine dust, rock tailings, etc., can cause degradation of the surrounding soil. Open-cast mining produces wastes with toxic metals and chemicals that destroy vegetation and harm human health.
4. Hazardous Wastes:
Heavy metal, pesticides, rubber, dye, and chemical industries generate wastes that are highly toxic, corrosive, and inflammable. Even hospital wastes are equally hazardous as they include swabs infected with pathogens, needles, syringes, and expired medicines which have further effects on the environment.
5. Electronic Wastes:
Damaged computer parts, mobiles, and other electronic goods are called e-waste. These are increasing in amount alarmingly throughout the world. These contain harmful metals like lead, silica, etc, which are often recycled but are operated by hand, which exposes the workers to these chemicals.
Management of Solid Waste
It involves the collection and categorization of wastes, transport to the disposal site, and their disposal. The disposal process consists of recovery and recycling, source reduction, burning, and dumping.
1. Recovery and Recycling:
Tins, cans, and other metal wastes, glass, plastic, polythene, and paper can be recycled. Recycling of metals not only saves the scarce resource but is also cheaper and less polluting. Broken glass is melted to obtain new glass. Waste cotton textiles from paper. Polythene is recycled to obtain new polythene. Broken plastic can be recycled to form inferior-quality plastic.
2. Source Reduction:
Solid wastes are collected, taken out of urban areas, and used in various ways for the formation of biogas, compost, and manure. The application of vermiculture is useful for forming manure and compost.
- Production of Biogas: Cowdung and other organic wastes from farm yards are used profitably in gobar gas plants for the production of fuel gas as well as enriched manure.
- Composting: All types of organic wastes of a city are used to prepare compost. In doing it the sludge obtained after the primary treatment of sewage along with other wastes is allowed to decompose in an open space. In 4-6 months compost is ready for use as a manure. Minerals may also be added to the organic matter to enrich the compost.
- Sludge Burning: Sludge obtained from sewage treatment plants can be mixed with coal and used in thermal power plants as fuel.
3. Burning:
Solid wastes are burnt in open spaces. However, it results in air pollution and produces an offensive odour. Two better methods for burning are
- Incineration: Wastes are burnt aerobically at 900-1300°C in incinerator chambers in a controlled way so as to reduce the degree of environmental pollution.
- Pyrolysis: Wastes are burnt anaerobically inside chambers at a temperature of 1650°C. It does not yield pollutants but industrial gas and other useful substances are produced.
4. Construction Material:
Flyash obtained from thermal power plants is used for the production of bricks, the construction of roads, and dams, and as cementing material. Fly ash is also used in filling lowlands.
5. Dumping:
Dumping is the piling of waste materials in selected low-lying land away from the locality. It is of two types, open and sanitary.
- Open dumping: Piling of waste materials is done on uncovered low-lying areas. The accumulated waste is periodically burnt or compressed to reduce its bulk.
- Sanitary dumping: The waste is pulverized and spread over low-lying land. It is compacted and covered by a layer of earth.
Radioactive Waste Management
Management of radioactive wastes is one of the major problems in using radioactive materials. Depending upon the amount of radioactivity the wastes are of three types: low level, intermediate level, and high level.
1. Low Level Wastes:
They can only be discharged into sewage. They can be stored for some time to further reduce their activity before disposal.
2. Intermediate Level Wastes:
Intermediate-level wastes do not produce heat and other environmental problems. Small amounts of these radioactive wastes occur in all ores. They are separated during refinement. They may be dumped in safe places inside proper containers.
3. High Level Wastes:
They should not be discharged as it is, but require special protective shields during handling and transport. They must be cooled prior to disposal. They are first concentrated to reduce their bulk, kept in special protective shields, and then placed in small ponds for 50-100 years, generally in the premises of nuclear reactors. This storage reduces emissions of radioactivity and heat. The weakened wastes kept in shielded containers are buried in rocks some 500 m deep inside the earth. The sea bottom is also used for it. However, environmentalists have objections to both methods.
Control of Radioactive Pollution
The following preventive measures can help to control radioactive pollution:
- Leakage of radioactive materials from nuclear reactors, industries, and laboratories using them should be totally stopped.
- Radioactive waste disposal must be safe. They should be changed into a harmless form or stored in safe places where they may gradually decay in a harmless manner.
- Radioactive wastes having only very low radiation can be discharged into sewers.
- Preventive measures should be adopted so that natural radiation level does not rise above the permissible limits.
- Safety measures should be taken against accidents in nuclear power plants.
- Workers using radioactive materials should wear protective garments and should be screened from radioactive materials by radiation-resistant walls.
- They should use radiation indicators to know the total amount of radiation to which they have been exposed.
- Atomic explosions and the use of atomic weapons should be given up.
Sources & Methods of Radioactive Pollution:
| Sources | Methods of Radioactive Pollution |
| 1. Nuclear Power Plants | The waste results in the form of radioactivity brings hazards when unsafely maintained. In Nuclear power plant accidents, if a radioactive core is exposed and a meltdown occurs releasing a high amount of radioactivity that will endanger life and the surrounding environment. |
| 2. Nuclear Weapon | Nuclear weapon tests are conducted above the ground or underwater. Nuclear bombings, such as what happened in Hiroshima & Nagasaki will create a vast and thorough devastation in a short time. |
| 3. Transportation | Transportation of nuclear wastes from one place to another place by any form of transportation (air, land, water) will possibly bring serious hazards to the environment if they are not maintained carefully and/or will cause accidents. |
| 4. Disposal of Nuclear Waste | The decaying process of radioactive wastes takes a very long time to progress. Some radioactive substances have a half-life of more than 10000 years which means they are dangerous in that great amount of time. There are common ways to dispose of nuclear waste buried underground very deeply or buried under the sea, and even an idea to send them to outer space. However, all of these are still dangerous and expensive. Science is still on its way to finding a better way to solve this problem. |
| 5. Uranium Mining | Uranium or any radioactive element mining results in radioactive waste that pollutes the surrounding environment. |
| 6. Radio Isotopes and Radiation Therapy | Many radioactive isotopes, such as C14, I125, and P32, and their compounds are used in scientific research. Wastewater containing these radioactive materials reaches water sources and returns to the human body through the food chain. |
