Data/hora: 07/06/2024 11:04:30

Provedor de dados: | 5
País: | France
Título: | Mesure de la demande chimique en oxygène dans l'eau de mer.
Autores: | Michel, Pierre.
Data: | 1972-03
Ano: | 1972
Palavras-chave: | Methodology; Organic matter; Oxygen demand; Seawater.
Resumo: | Introduction: Measuring the chemical oxygen demand (COD) is a way of determining the organic matter in water based on its oxidisibility by bichromate. The presence of organic matter in sea water is one of the factors that determines the productivity of the oceans: whether this organic matter will be absorbed directly or must first be transformed into nutritive substances by bacteria. This beneficial action also has its limits. On the one hand, consumption of organic matter remains limited; when it exceeds a certain rate, there is no longer any increase in productivity. On the other hand, the excess organic matter deteriorates by consuming the dissolved oxygen and thus competes with marine life. In extreme cases, this excess can cause the eutrophication of the environment, that is, its practically irreversible deterioration. Finally, organic matter can be considered as a pollution indicator since it normally accompanies urban wastewater and most industrial wastewater. It is therefore of interest to proceed with its dosage during the physicochemical examination of the environment. In the case of fresh water, the problem has long since been resolved, their dosage being carried out by oxidising them using either permanganate or sulphuric bichromate. This last method has been standardised (1); it gives a completely satisfying result for river water and gives the Financial Basin Agencies a basis for calculating taxes. For estuary or sea water, these methods are not directly applicable. The presence of easily oxidisable chlorides in significant quantity renders measurements meaningless. Oxidisation by permanganate was adapted by Giral (1927) and Gomez Ibanez (1928). The oxydisation of chlorides was at that time avoided by adding manganese sulphate, which, in a low-acid environment, transforms permanganate into manganese dioxide, which serves as an oxidising agent. But this oxydisation's yield is weak and causes a levelling of the results. Their expert interpretation would therefore require an accuracy that they achieve with difficulty. Some new apparatuses can perform an automatic analysis of organic matter in water. All that is needed is to insert a micro-sample, which is instantly vaporized. The organic matter is then oxidised by the oxygen at a very high temperature and the carbonic gas or the carbon oxide that is formed is measured out by infrared absorption. The method is applicable to sea water. It therefore resolves in an elegant way the problem that is posed, but it is also very costly. Many small coastal laboratories, such as shellfish farms, need this information. They have the immense advantage of being able to analyse, rapidly and on site, instable samples whose processing by a larger centralised laboratory would not give completely satisfying results. It is therefore useful to develop for this use a reliable method that allows serial dosing without the need for special equipment.
Tipo: | Text
Idioma: | Francês
Identificador: | http://archimer.ifremer.fr/doc/1972/publication-2060.pdf
Editor: | ISTPM
Relação: | http://archimer.ifremer.fr/doc/00000/2060/
Formato: | application/pdf
Fonte: | Revue des Travaux de l'Institut des Pêches Maritimes (0035-2276) (ISTPM), 1972-03 , Vol. 39 , N. 3 , P. 361-365
Fonte: | Ifremer