what are the causes of water pollution?

Answer 1

Principal sources of water pollution are:
* industrial discharge of chemical wastes and byproducts
* discharge of poorly-treated or untreated sewage
* surface runoff containing pesticides
* slash and burn farming practice, which is often an element within shifting cultivation agricultural systems
* surface runoff containing spilled petroleum products
* surface runoff from construction sites, farms, or paved and other impervious surfaces e.g. silt
* discharge of contaminated and/or heated water used for industrial processes
* acid rain caused by industrial discharge of sulfur dioxide (by burning high-sulfur fossil fuels)
* excess nutrients added by runoff containing detergents or fertilizers
* underground storage tank leakage, leading to soil contamination, thence aquifer contamination.

Contaminants
Contaminants may include organic and inorganic substances.

Some organic water pollutants are:
* insecticides and herbicides, a huge range of organohalide and other chemicals
* bacteria, often is from sewage or livestock operations;
* food processing waste, including pathogens
* tree and brush debris from logging operations
* VOCs (Volatile Organic Compounds, industrial solvents) from improper storage

Some inorganic water pollutants include:
* heavy metals including acid mine drainage
* acidity caused by industrial discharges (especially sulfur dioxide from power plants)
* chemical waste as industrial by products
* fertilizers, in runoff from agriculture including nitrates and phosphates
* silt in surface runoff from construction sites, logging, slash and burn practices or land clearing sites

Transport and chemical reactions of water pollutants
Most water pollutants are eventually carried by the rivers into the oceans. In some areas of the world the influence can be traced hundred miles from the mouth by studies using hydrology transport models. Advanced computer models such as SWMM or the DSSAM Model have been used in many locations worldwide to examine the fate of pollutants in aquatic systems. Indicator filter feeding species such as copepods have also been used to study pollutant fates in the New York Bight, for example. The highest toxin loads are not directly at the mouth of the Hudson River, but 100 kilometers south, since several days are required for incorporation into planktonic tissue. The Hudson discharge flows south along the coast due to the coriolis force. Further south then are areas of oxygen depletion, caused by chemicals using up oxygen and by algae blooms, caused by excess nutrients from algal cell death and decomposition. Fish and shellfish kills have been reported, because toxins climb the foodchain after small fish consume copepods, then large fish eat smaller fish, etc. Each step up the food chain concentrates certain toxins like heavy metals and DDT by approximately a factor of ten.

For several years ocean researcher Charles Moore has been investigating a concentration of floating plastic debris in the Pacific Ocean. His study indicates that ocean currents have added to the mass until it is now about the size of Texas. Many of these long-lasting pieces wind up in the stomachs of marine birds and animals.[1]

Many chemicals undergo reactive decay or change especially over long periods of time in groundwater reservoirs. A noteworthy class of such chemicals are the chlorinated hydrocarbons such as trichloroethylene (used in industrial metal degreasing) and tetrachloroethylene used in the dry cleaning industry. Both of these chemicals, which are carcinogens themselves, undergo partial decomposition reactions leading to new hazardous chemicals.

Groundwater pollution is much more difficult to abate than surface pollution because groundwater can move great distances through unseen aquifers. Non-porous aquifers such as clays partially purify water of bacteria by simple filtration (adsorption and absorption), dilution, and, in some cases, chemical reactions and biological activity: however, in some cases, the pollutants merely transform to soil contaminants. Groundwater that moves through cracks and caverns is not filtered and can be transported as easily as surface water. In fact this can be aggravated by the human tendency to use natural sinkholes as dumps in areas of Karst topography.

There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. Some of these secondary impacts are:
* Silt bearing surface runoff from can inhibit the penetration of sunlight through the water column, hampering Photosynthesis in aquatic plants.
* Thermal pollution can induce fish kills and invasion by new thermophyllic species

You could get more information from the link below...

Answer 2

Causes of Water Pollution


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There are two kinds of water pollution:
Organic
Industrial

Organic includes waste materials such as human and animal excretions and discarded parts of harvested crops
and Industrial includes synthetic chemicals and heavy mateal which are usually toxic.
HUMAN IMPACT:
Humans cause almost all of water pollution, this is caused by using excess fertilizers, sewage, oil
and others.

FERTILIZERS-
The overuse of fertilizers disposed into water bodies cause over growth of algae and leave bo oxygen
for plants and animals to live.

SEWAGE-
From municipal wastewater systems and septic tanks, the sewage in water can cause serious illness to
both the people drinking it and the organisms living in it.

OIL-
At least 1 percent of the world's oil production ends up in the ocean through oil spills. For example
in 1989 Exxon Valdez spilled 11 million gallons of oil in Alaska's Prince William Sound killing thousands
of organisms that lived in or near the sound. That is the kind of damage that the sound will never fully
recover from.

OTHER POLLUTANTS-
Pesticides, bioaccumulative chemical compounds, and garbage are some other contributers to the human
impact on water pollution.

Answer 3

There are many causes for water pollution but two general categories exist: direct and indirect contaminant sources.
Direct sources include effluent outfalls from factories, refineries, waste treatment plants etc.. that emit fluids of varying quality directly into urban water supplies. In the United States and other countries, these practices are regulated, although this doesn't mean that pollutants can't be found in these waters.
Indirect sources include contaminants that enter the water supply from soils/groundwater systems and from the atmosphere via rain water. Soils and groundwaters contain the residue of human agricultural practices (fertilizers, pesticides, etc..) and improperly disposed of industrial wastes. Atmospheric contaminants are also derived from human practices (such as gaseous emissions from automobiles, factories and even bakeries).
Contaminants can be broadly classified into organic, inorganic, radioactive and acid/base. Examples from each class and their potential sources are too numerous to discuss here.

FOR MORE PL. VISIT:
http://edugreen.teri.res.in/EXPLORE/water/pollu.htm

Answer 4

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