Sources

Methods

Petroleum Products

Manufacture of plastics

Manufacture of lubricants

Fractional distillation of crude oil

Vehicle fuel

Manufacture of solvents

Refinery gases for domestic cooking

Paraffin wax

Bitumen for road surfacing and roofing 

Manufacture of synthetic fabrics; nylon, terylene

Accidental spills from ships, tanker trucks, pipelines and  leaky underground storage tanks.

Old and faulty machineries in industrial factories which are inefficient

Improper refinery processes with the production of toxic byproducts

Synthetic Agricultural Chemicals

Pesticides

Herbicides

Insecticides

Fungicides

Accumulation of chemicals in plants and animals when die, will not decompose which will spread to water sources during rainfall, increasing toxicity of water source.

Heavy Metals

Mining

Automobile exhaust

Metallurgy

Manufacture of semiconductors

Manufacture of batteries

Leak pipelines

Unfiltered industrial discharge which flows into water sources

Emission of oxides of lead from tractors and machineries used during mining or in industries which dissolves in water

Improper storage of heavy metals in storage containers

Hazardous Wastes

Radioactive  materials

Corrosive materials

Reactive materials

Ignitable materials

Improper treatment of waste which are still toxic upon release 

Excess Organic Matter

Chemical fertilizers

Sewage sludge

Animal waste

Stimulate algae growth and during decomposition of algae it consumes oxygen which dissolves in the water, decreasing the level of oxygen in aquatic ecosystem and increase the mortality rate (death rate) of flora and fauna. At the same time, decaying material will turn the water murky. This is called eutrophication.

Sediment

Soil erosion and soil

particulates washed by storms and floodwaters from croplands, unprotected soils, strip mines, roads and bulldozed urban areas 

Accumulation of sediments will turn the water murky

Mass flow of mud into water source system will alter the clarity of water

Infectious Organisms

Microbes (virus, bacteria, protozoan) 

Host for growth of these microorganisms, consuming nutrients in lakes, rivers, oceans

Infect plants and animals in the aquatic ecosystem, which die and upon decomposition which accumulates sediments and organic matters which turns the water source murky thereby polluting it.

Air Pollution

Acid rain

Emissions of greenhouse gases

Dissolves into rainwater which alters the pH of water

Dissolves into water sources which affects the aquatic ecosystem  

Thermal Pollution

Drawn from rivers and lakes to be used as coolants in factories and power plants

Warmer water returned to rivers and lakes will alter the species makeup of the aquatic ecosystem, introducing infectious organisms and others which are adaptable to warmer temperature, which will alter the water composition in the lake or river

Level of oxygen in water sources will be reduced, threatening the aquatic ecosystem which will lead to the death of many species and in turn make the water murky

Soil Pollution

Accumulation of sediments -accumulation of sediments

Non-biodegradable chemical fertilizers

Seeping of  rainwater     containing chemical                        pollutants from soil surface through underground soil which flows into water systems