Nitrogen naturally has two stable isotopes. There are also six instable isotopes. The human body consists of approximately 2. This means nitrogen is a dietary requirement.
Nitrogen is the main constituent of the air we breathe. Increased nitrogen concentrations in air may cause asphyxiation, but mainly because it results in a lower oxygen concentration. We mainly absorb nitrogen as proteins. These cannot be stored and are therefore directly converted to energy when not required. Nitrogen is excreted through the kidneys as urea. We also release nitrogen through the skin and the intestinal tract.
When kidney failure occurs, one is incriminated with protein decomposition products. The calculation factor from nitrogen to protein in 6. This value does not represent protein digestibility. Nitrates are not generally considered toxic, but at high concentrations the body may convert nitrate to nitrite. Nitrites are toxic salts that disrupt blood oxygen transport by disrupting haemoglobin to methemoglobin conversion.
This causes nausea and stomach aches for adults. For young infants it may be extremely risky, because it rapidly causes blood oxygen deprivation. Nitrites and amines from protein-rich food form so-called nitrosamines, which are carcinogenic substances. This reaction may be prevented by the reducing and anti-oxidant properties of vitamin C. Examples of toxic nitrogen compounds are PAN-compounds, which are fifty times more toxic than the nitrogen compounds these are converted from nitriles and nitrilo compounds.
NTA is not absorbed in the stomach, because it is complexed with heavy metals. It may however still disrupt electrolyte metabolism. Nitrogen oxides play a more significant role in air than in water. These can cause breathing disorders. Nitrogen hydrogen acid fumes may cause irritations, heart problems and collapsing.
Which water purification technologies can be applied to remove nitrogen from water? For further treatment, lime and HOCl addition were attempted. This however turned out not to be very effective. Consequently, the third step of wastewater treatment includes biological nitrogen removal. This means a combination of nitrification and denitrification processes, carried out by various micro organisms. Nitrification means ammonium oxidation from protein decomposition processes by bacteria, and subsequent conversion to nitrates.
This requires oxygen, which is added by aeration. The water must be aerated for a sufficient period of time. Ammonium is converted to nitrite, and subsequently to nitrate. The reaction mechanism is a follows:. This does not require aeration, as it is an anaerobic process. Nitrogen is eventually released into air. A carbon source is often added to speed up the decomposition process. One example of a possible reaction mechanism is:. Consequently, wastewater treatment requires both aeration, and the presence of oxygen-pour spaces.
In countries such as Brazil, water hyacinths are applied as a third water purification step. These remove both nitrogen and phosphorus from water. Helophyte filters can be applied in water purification of small surface waters. Ammonia can be removed from water by the so-called stripping process.
This means removing ammonia from wastewater by means of air or steam, by gasifying it. Other nitrogen compounds that generally occur in small amounts may be removed by various methods. For example, NTA can be decomposed under aerobic conditions in aeration tanks. Phosphorus P is created through the natural weathering of rocks and soil and rainfall runoff transports it from the land into waterways. For healthy waterways, the complex and important process of nutrient cycling is vital.
Nutrients in waterways are absorbed by aquatic microorganisms e. When these organisms die, they decompose and the nutrients are released back into the water where they can be absorbed by other organisms. This is nutrient cycling. Cycling of nutrients may repeat many times until the nutrients are buried in the stream sediment or nitrogen is released to the atmosphere in the form of gas.
Nutrients in waterways also move through the food chain. Phytoplankton absorb the nutrients. Zooplankton may then be eaten by small fish, which are eaten by larger fish, and so the nutrient uptake continues through the food chain.
Light, nitrogen, and phosphorus are the main factors that control the growth of aquatic plants. Nitrogen and phosphorus are often found in fertilisers because they stimulate plant growth. These nutrients may become an environmental problem, and a form of pollution, when they enter waterways at a faster rate than they can be used in the food chain and cycled through the system. High nutrient levels can lead to excessive plant growth, sometimes creating algal blooms. Too much nitrogen in the water appears to be the main cause of algal blooms, particularly in South East Queensland SEQ marine and estuarine waters.
Eutrophication can cause fish kills and other problems because aquatic animals and plants need a certain level of dissolved oxygen in the water to survive. Point source pollution comes from a single point such as from a pipe. Diffuse sources of pollution come from many places within a wide area.
Diffuse sources of pollution can include sediment or nutrients from catchment runoff, groundwater, rain, or when airborne pollutants fall to the ground. Some algal blooms are harmful to humans because they produce elevated toxins and bacterial growth that can make people sick if they come into contact with polluted water, consume tainted fish or shellfish, or drink contaminated water.
Nutrient pollution in ground water - which millions of people in the United States use as their drinking water source - can be harmful, even at low levels. Infants are vulnerable to a nitrogen-based compound called nitrates in drinking water. Excess nitrogen in the atmosphere can produce pollutants such as ammonia and ozone, which can impair our ability to breathe, limit visibility and alter plant growth.
When excess nitrogen comes back to earth from the atmosphere, it can harm the health of forests, soils and waterways. To learn more, read about the sources and solutions of nutrient pollution. Skip to main content. Nutrient Pollution. Contact Us.
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