The nitrates are the salt S of the nitric Acid . The formula of the ion nitrates is NR O − .
The nitrate of Potassium (Salpetre) is used in the black Poudre
The nitrates of Sodium (Salpetre of Chile) and of ammonium are used like Engrais.
The nitrate of Ammonium mixed with Fioul constitutes a powerful explosive. Very stable, it must be started to explode.
Not to confuse nitrates and Nitrite S NR O − salts of the Nitrous acid , or result of the Reduction of nitrates by specific Bacterium S. The Nitrite S are regarded as Poison S and, according to the authors, like having actions Tératogène S and/or Cancérigène S.
The presence of nitrates in the Eau is an index of agricultural Pollution of origin (Engrais), urban (dysfunction of the networks of Assainissement) or industrial.
In many countries, the water intended for human consumption must respect limiting values (for example 50 mg/l in France) to be described as drinkable S.
Water pollution by nitrates
Nitrates and eutrophication
As that was indeed shown in the lakes , the Phosphate S are the independent factor of Eutrophisation fresh water on long steps of time. The nitrates are the second important cause, and they intervene often together; in fresh water, but also in water Brackish S and salted closed or little renewed.
According to the Ifremer, with the beginning of the year 1900, the nitrate rates of the Breton rivers were not to exceed 3 with 4 mg/L. They were multiplied by 10 on average over a century.
According to Ifremer always, eutrophications of the bays of Saint-Brieuc, Mount Saint Michel, of Lannion, Douarnenez or Rade of Brest, noted since the end of the 20th century are typical situations of relatively confined and not very major water masses, victims of recent nitrate contributions. The estival Biomasse grows there after the nitrate contributions of spring. When these contributions decrease in summer, the nitrate rate in the Ulve S also decreases, at the point to block the estival growth of these algae whereas the phosphorus rate remains almost stable.
Les mathematical modelings of Ifremer indicates that to decrease the agricultural nitrate contributions is the only means of limiting the pullulations of ulves to spring (the nitrate rates of the rivers having at least to be divided by four, to pass from 40 mg/L with less 10 mg/L), which should be possible by husbandries adapted, including the networks of enherbées bands protecting the courses from eau.
Paradoxalement, brutal a Carence out of nitrogen of an aquatic environment before eutrophic or dystrophe can lead initially to Inflorescence S of Cyanobactérie S (or blue algas) able to assimilate nitrogen of the atmosphere directly and of living in condition Anaérobie.
The measurement most adapted to a fight against the appearance or the development of the phenomena of eutrophication of stagnant fresh water consists in reducing as much as possible the phosphorated contributions. At sea, and in bays, the nitrate contributions must also be the subject of a reduction.
Toxicity for the Amphibians
The necessary nitrate concentrations to kill 50% of tadpoles of certain species of Amphibians (studies made in North America) are from 13 to 40 parts per million (ppm). Weak concentrations (from 2 to 5 ppm) have at certain species of Amphibians of the chronic effects: reduced stroke, malformations during the development.note: 1 ppm is equivalent to 1mg per kg, (comparable with Mg per liter if the density of water is worth 1)
Discusses on the toxicity of nitrates
Many studies blame a toxic effect of nitrates, by correlating in several countries mortality by gastric cancer with the daily nitrate ingestion. However, in 1996, a bibliography written by Jean the hirondel and coll, highly criticized, tries to make a summary of the supposed beneficial effects of nitrates.-
Effect anti-infectieux
La secretion by salivary glands and of the transformation of salivary nitrates into nitrites would make it possible to use the bactericidal property of nitrites, in acid medium. This one is known for a long time in the agro-alimentary sector for the conservation of food. The antibactérien effect of acidified nitrites is checked artificially for various enterobacteries: salmonella, escherichia coli, shigella. - Effect on the Blood-pressure and pathologies cardio-vasculaires
L' increase of the blood rates of s-nitrosothiols the nitrate food supplies mainly made up of ingestions of drink vegetables and water could exert an influence on the functions of the organization depend on nitric oxyde. It is in this manner that the nitrates of solid food and the drink water could reduce at the man the risk of cerebral vascular pathology and of arterial hypertension (Bockman and coll, 1997). - Effet on cancers gastriques
L' assumption of the hirondel is that the nitrates of feed water could play a part anticarcinogenic. Complementary work is necessary to confirm or cancel this assumption. - Autres
Lors of the intragastric chemical synthesis of nitric oxyde, the nitrate food supplies would play a beneficial part by releasing the smooth musculature of the stomach and by protecting its mucous membrane.
The bibliographical synthesis of Jean the hirondel was however called in question by association Eau & Rivières showing it to be made the spokesperson of the industrialists wishing an easing of the standards about nitrates. It was reproached to him for forgetting references which disturbed its thesis, to be itself wrongly claimed support of Professor Hamon, to have seen its theses refuted by a report/ratio of the Section of Water of the Superior council of public health of France before even the publication of its book. Its work was also criticized by the scientific community at the time of the Regional conference of the environment of 1997 which reproached the lightness of its study. The Institute of the Environment which financed the publication of the book of Jean the hirondel, tackled association Eau & Rivières for public insults and slanderings and was débouté by the court of Rennes on November 3rd, 1998.
Another article criticizing the standard which fixes the acceptable nitrate threshold in the drink water was published in the review Research, extract of a work published under the direction of Marian Apfelbaum, professor of nutrition at the medical college Xavier-Bichat (Paris). One can read there that “the standard which fixes the acceptable nitrate threshold in the drink water is the fruit of an expertise carried out in the years 1960, that the new scientific elements contradicted”. It also states that “the consumption of nitrate is completely inoffensive at the man. ”
The Péroxyacetylnitrate (SIDE) is one of the photochemical pollutants of the air (irritant) which acts a little like the Ozone, but to some extent in a complementary way. (In polluted zone, and exposed to UV solar (or of artificial origin) its rate often increases when that of Ozone decreases)
References
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