Organic and inorganic nutrient pollution in water, - Sources and effects

Inorganic nutrient pollution

The main sources of inorganic nutriant pollution are nitrates and phosphates.

=Sources

Nitrates are very soluble and may wash off farmland as artificial fertiliser, manure, ploughing or as silage fluid. They may also be ingested in food where they were used as a presevative.

Phosphates are not very soulable. They are not washed off farmland in large quantities but do get into rivers or lakes in sewage effluent unless they are removed by tertiary treatment. Inorganic nutrients are released during the breakdown of dead organic matter such as sewage and manure.

=Effects

Effects of nitrates on babies

Nitrates are not very toxic but bacteria in the gut convert them to nitrates. Nitrites react with haemoglobin in the blood and reduce its abilityto carry oxygen. This can lead to 'blue baby syndrome'. Infants are especially at risk as they have more of the necessary bacteria and their haemoglobin reacts more rapidly with nitrites. This is usually only a problem with water from shallow wells that drain water from arable farmland.

Nitrates and cancer

Gut bacteria convert nitrates to nitrites. These may then be converted in the gut to nitrosamines, which are carcinogenic and may cause stomach cancer. Most reasearch has been carried out on rats and links between nitrates in human food or water remain inconclusive.


Euthrophication

Euthrophication is a natrual process as a water body ages and changes from an oligotrophic to a eutrophic lake. Nutrient levels build up as nutrient-rich water and sedimants are gradually washed in. This rarley causes problems. However, cultrual eutrophication involves the addition of nutrients by humans, and normally in large quantities. Main nutrients include nitrates and phosphates. The disolved nutrients are absorbed by blue-green algae directly from the water. There growth causes problems:

*Release toxins.
*Shade subbmerged plants so they can't get sunlight for photosynthesis.
*Unreliable food source, as if requirements for life are not right they die. This limits biodivercity.

Deaths caused by deoxygenation are most likely to occur at the end of summer. Dead vegitation and warm tempretures will allow bactria to thrive in mass quantitys, using oxygen as they multipley. This is a particular problem at night.

Organic nutrient pollution

= Sources:

Liquid effluent containing organic nutrients such as carbohydrates, Lipids and proteins are produced by a variety of processes involving animal and plant products. These include sewage works works, manure, silage fluids, leather tanneries, paper mills and food processing plants.

= Effects:

Deoxygenation

This involves untreated organic nutrients being released and micro-organisms feeding on them. Their aerobic digestion will reduce oxygen levels in the water, suffocating many other aerobic organisms such as fish and insects.

The bacteria can also cover the river or lake bed, which prevents light reaching the normal water plants. Photosynthesis is reduced, the plants die and food webs are disrupted.

Release of inorganic nutrients

Organic matter may decay and release inorganic nutrients (e.g Nitrates and Phosphates) which could then cause cultural euthrophication (inorganic and organic nutrient pollution are interconnected).

Pathogens

Sewage may contain pathogens from infected people, which may spread disease through contaminated food and water. Diseases spread via sewage include cholera, typhoid and dysentery.

Edited by ex nihilo - 9/2/2012, 01:28