Major types of water pollution
Organic wastes that is largely untreated human waste, sewage, and industrial waste from processing various food roducts, from the pulp and paper industry, and from animal feedlots. Inorganic pollutans that is salt brines, acids, phospates, heavy metals, asbestos, PCBs, radioactive chemicals.
Toxic substances Hazardous or toxic substances are those that can cause an increase in mortality rates or irreversible or incapacitating illness or those that have other seriously adverse health or environmental effects. Toxic substances that have been released on land include acidic chemicals, inorganic metals (such as mercury or arsenic) flammable solvents, pesticides, herbicides, phenols, explosives, and so on. For example benzene is a common industrial chemical that is also used in plastics, as well as dyes, nylon, food additives, detergents, drugs, fungicides, and gasoline. Benzene is a toxic and can cause of a anemia, bone marrow damage, and leukimia. Studies have shown that benzene workers are several times more likely than the general population to get leukimia. Solid wastes come from residential garbage, industrial wastes, agricultural wastes, mining wastes. The most common one we usually meet is residential garbage.
Only about a third residential wastes are recovered through recycling. A low proportion that is due to the lack of financial backing for recycling operations, the small size of markets for recycled products, and toxic chemicals present in recyclable garbage. City garbage dumps are significant sources of pollution, containing toxic substances such as cadmium (from rechargeable battery), mercury, lead (from car battery, and TV pictures tube), vanadium, copper, zinc, and PCBs. Nuclear wastes Light water nuclear reactors contain radioactive materials, includeing known carcinogens such as strontiums 90, cesium 137, barium 140, and iodine 131. Extremely high levels of radiaton from these elements can kill a person, lower dosages (especially if radioactives dust particles are inhaled or ingested) can cause thyroid, lung, or bone cancer as well as genetic damage that will be transmitted to future generations.
Depletion of Species and Habitats
Human activity has rendered dozens of plants and animal species extinct. Since 1600 at least 96 known pecies of mammals and 88 major identifiable species of birds are known to have become extinct. Several hundred more species such as whales and salmon today find themselves threatened by commercial fishing. Forest habitats on which the bulk of species depend are also being decimated by the timber industry.
Depletion of Fossil Fuels
Until the early 1980s, fossil fuels were being depleted at an exponentially rising rate. That is, the rate at which they were being used had doubled with the passage of a regular fixed time period. Some early predictions of resources depletion assumed that fossil fuels would contiinue to be depleted at these exponentially rising rates. If continued, an exponentially rising rate of depletion would end with the complete and catastrophic depletion of the resource in a relatively short time. Estimated world resources of coal would be depleted in about 100years, estimated world reserves of oil would be exhausted in about 40years and estimated reserves of natural gas would last only about 25years.
Depletion of Minerals
If earlier exponentially rsing rates of depletion continued then alumunium would have been scheduled for exhaustion in the year 2003, iron in 2025, manganese in 2018, molybdenum in 2006, nickel in 2025, tungsten in 2000, zine in 1990, and copper and lead in 1993. World resources are also limited, and the depletion rates of the world’s supplies of minerals will also eventually peak and then gradually decline as remaining supplies become harder and more expensive to mine.
The precise impact the limitation of worlds supplies will have on us exceedingly difficult to predict. Miningtechnologies may continue to develop , which will reduce the difficulty and cost of mineral extraction and extend the period of decline. This has in fact been the case for most mineras up to the present. Increased recycling may reduce the need for intensive mining of remaining minerals reserves. Substitutes may be found for many of the minerals whose supply is limited, and technological development may make many current uses of these minerals obsolete.