Background water quality defining

Commission, 2008). In this projected modification to the Directive, only 4 trace elements are listed Cd, Ni, Pb and Hg. For these elements, the values obtained in this study were compared with the maximum allowable concentrations (MAC-EQS) for inland surface waters when available (Table 4.5.2). In France, a Circulaire (2007) defines NQEp (which are the French translation of the European MAC-EQS). However, since there is still a need to evaluate the geochemical background for many trace elements in surface waters, it has to be borne in mind when comparing water quality data with NQEp values, that these are not yet the definitive values. Finally, data were compared with limits fixed for drinking waters (Decree, 2001). 

It is essential to know better the natural fluxes (anthropogenic fluxes are rather well estimated) and their variations, but even more important is knowledge about the biosphere-atmosphere interaction What processes control the environmental parameters that themselves maintain life on earth We can then ask another question What is the threshold of quantitative change (of any parameter) leading to a new quality of life Finally, we have to answer (or to define) what changes in air, soil and water quality humankind can even accept in future against the background of sustainable development. 

The limit of detection (LOD) is one of the most important terms used for comparing various analytical procedures, techniques, or instruments. It is defined as being the lowest concentration of the analyte that can be distinguished with reasonable confidence from the blank or background. In water quality laboratories the confidence level of 95% is adopted as a standard for LOD for all analytes. 

Various normalization techniques are available to achieve the first objective [ 1,2,10,76-78]. For example, environmental quahty is scaled from 0 (very bad) to 1 (very good) by the use of value functions. Very bad and very good can be defined in various ways. For a qualitative variable such as water clarity that has been ranked from 1 to 5 or from 1 to 10 by the environmental impact assessor, the scales are simply transformed arithmetically to the range from 0 to 1. For quantitative variables such as water or air quality, very bad could be the maximum permissible concentrations established by law, while very good could be the background concentrations found at great distances from sources. 

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