Describe the causes, effects and control of water, air and soil pollution.

a)Water pollution.
Causes and effects
-Release of untreated sewage into water bodies; it contains faeces and nitrogenous wastes; Sewage contains pathogens that cause water borne diseases e.g. cholera, Typhoid, amoebic dysentery; Sewage also contains nitrogenous wastes/ nitrates that cause eutrophication which reduces oxygen in water thus causing death of aquatic organisms through suffocation;
-Oil spillage in water bodies from oil tankers and offshore oil refineries from oil tanker accidents, offshore oil wells and damaged warships; Oil spreads on the surface of water reducing oxygen supply into the water leading to suffocation and death of aquatic organisms; Oil also blocks the stomata thus affecting photosynthesis and gaseous exchange of phytoplanktons thus killing them; Oil layer leads to reduced light penetration thus affecting photosynthesis; Oil also stick together feathers of aquatic birds making it difficult for the birds to fly; Oil clogs the respiratory surfaces of aquatic animals killing them.
 Release of domestic and industrial wastes into water bodies; they contain poisonous substances/ chemicals that kill the aquatic organisms; and enter the food chain and accumulate to toxic levels;
 Hot water -from industries discharged into water bodies; Heat reduces the amount of dissolved gases e.g. oxygen and carbon (IV) oxide killing the organisms due to lack of oxygen or lack of photosynthesis; Heat raises the respiratory rate to abnormal levels causing malfunctioning in the organisms; Hot water may kill the living organisms by denaturing enzymes.
-Agro-chemicals- e.g. fertilizers, herbicides, pesticides. Fertilizers contain nitrates and phosphates while pesticides contain heavy metals e.g. mercury and copper and Chlorofluorocarbon which is not easily broken down/ non-biodegradable; The heavy metals affect respiratory activities of aquatic organisms; accumulate in bodies of organisms and affect functioning of body organs e.g. brain, kidney and liver; enter the food chains and accumulate along the chains becoming poisonous at higher trophic levels; Nitrates and phosphates in fertilizers cause eutrophication and change in water pH;
-Lead from pipes and tanks in domestic water supply systems; Lead affects the physiological functioning of body organs; and damages the nervous system resulting in mental problems.
-Soil erosion; It causes siltation of water bodies making water unfit for human consumption and unsuitable habitation for certain animals; Silt/ soil particles clog the respiratory surfaces of plants and animals thus affecting gaseous exchange; Soil particles/ silt reduce light penetration thus reducing the rate of photosynthesis in aquatic plants;
Control of water pollution.
-Treatment and proper disposal of sewage;
-Treatment of industrial waste before disposal and cooling of hot water from the industries before discharging it into water bodies;
-Caution when transporting oil in ships and when mining petroleum found in ocean deposits;
-Biological and cultural control of weeds, pests and diseases;
-Use of organic manure instead of inorganic fertilizers;
-Prevent soil erosion through terracing, construction of gabions and reforestation;
-Disposal of litter/ garbage in designated places but not/ away from water bodies;
-Use of biodegradable herbicides and pesticides;
-Educate farmers on the use of correct amounts of agro chemicals;
-Banning the use of phosphate –based detergents;
-Replacing lead pipes with plastic pipes;
b)Air pollution.
Causes and effects
-Release of chemical substances containing Sulphur (IV) oxide, hydrogen sulphide, nitrogen (IV) oxide from volcanic activities; they cause acid rain which alters/ changes/ lowers the soil pH thus affecting plants and other living organisms in the soil and causes leaching of minerals/ nutrients, Sulphur (IV) oxide causes respiratory infections e.g. bronchitis, Pneumonia and heart failure, nitrogen (IV) oxide is carcinogenic thus causes cancer, they interfere with gaseous exchange in animals. Hydrogen sulphide is poisonous when inhaled hence it causes death;
-Carbon (IV) oxide and carbon (II) oxide from the combustion of garbage and organic fuels; they cause green-house effect/ global warming; Carbon (II) oxide causes respiratory poisoning / suffocation;
-Smoke and fumes from factories and engines;
-They reduce visibility on the roads, block the stomata of leaves affecting photosynthesis and transpiration, cause eye irritation, headaches and breathing difficulties and contain carbon (IV) oxide which is a respiratory poison;
-Dust from cement and lime factories, quarries and road construction; it blocks the stomata of leaves hence affecting photosynthesis and transpiration, cause respiratory diseases/ affects respiratory system and reduces visibility and irritates the eyes;
-Chlorofluorocarbons (CFCs) from aerosols (e.g. pesticides, herbicides, dry cleaning agents); they cause irritation to respiratory organs and poisoning of water plants, deplete ozone layer leading to more penetration of ultraviolet (UV) rays which cause skin cancer and affect crops;
-Lead from combustion/ burning of leaded petrol by motor vehicles; It enters the blood stream thus damaging the body organs e.g. brain, liver and kidneys, affects the nervous system causing mental disorders/ poor mental development and blocks the stomata hindering gaseous exchange and photosynthesis causing death of the plant;
-Aerosols; (e.g. pesticides, insecticides, fungicides, perfumes, air freshener and spray paints). They contain heavy metals (e.g. copper, lead) and chlorofluorocarbons (CFC). Copper causes irritation of respiratory organs and poisoning of water plants and fish. Chlorofluorocarbons deplete ozone layer leading to increased penetration of ultra violet (UV) rays that cause skin cancer in humans.
-Noise from vehicles, machines in factories, aeroplanes; it interferes with hearing in animals and causes stress, headache and abortion; Control of air pollution.
-Use of CFC free aerosols, perfumes and appliances;
-Use of unleaded fuels in vehicles;
-Use of ear muffs in factories and industries;
-Use of renewable sources of energy e.g. biogas and electricity;
-Use of biological methods instead of using pesticides and herbicides;
-Legislation i.e. enforcement of laws on environmental pollution;
-Exhaust pipes should have filters to remove impurities/ solid particles from the released gas;
-Educating the public on the need of and how to control air pollution;
-Scrubbing the gases emitted from factories to remove acidic gases e.g. nitrogen (IV) oxide and Sulphur (IV) oxide;
-Ban smoking in public places;
c)Soil pollution.
Causes and effects
-Acid rain; increases the soil pH thus affecting plants and other organisms in the soil, causes leaching leading to loss of soil fertility.
-Aerosols; they contain heavy metals (e.g. lead and mercury), the chemicals kill micro-organisms in the soil thus reducing soil fertility, the heavy metals enter the food chain and accumulate to high levels causing death;
-Solid wastes e.g. plastics, glass, rubber, metals and non-biodegradable materials; they form breeding grounds for mosquitoes, rats and flies which are disease vectors, they limit soil aeration and microbial activity thus making soil infertile, some e.g. glass bottles can injury to animals, they also destroy the aesthetic value of land.
-Inorganic fertilizers; they reduce the pH of soil thus affecting plants and soil organisms thus reducing microbial activity reducing soil fertility;
-Oil from overturned oil tankers, burst oil pipelines, garages and oil refineries; It covers the ground thus affecting soil aeration thus reducing the microbial activities.
-Chemicals e.g. acids and strong bases/ alkalis; they cause changes in soil pH thus affecting plants and soil micro-organisms which thus lowers rate of decomposition/ fertility, also cause leaching of nutrients/ mineral salts thus lowering fertility;
-Radioactive emissions; they cause cancer, mutations and death;
Control of soil pollution
-Famers to use organic manures instead of inorganic fertilizers.
-Use of biological methods to control pests and diseases;
-Recycling of solid wastes e.g. plastics;
-Biodegradable wastes e.g. plant materials and food remains should be disposed in a compost pit;
-Transporting petroleum products using pipeline to prevent spillage;
-Enactment of laws on land pollution;
-Proper handling and deposition of non-biodegradable wastes e.g. controlled burning, burying deep in the soil;
-Wastes e.g. clothes and papers should be burned in incinerators;
-Control of radioactive emissions;