Metrological Needs for Monitoring Aquatic Environments: From the Demonstration of Metrological Traceability to the Decision Making Process

Abstract

In Europe, the implementation of the Water Framework Directive WFD, in 2001, marks a strong standpoint. In addition to its objectives of a return to good chemical and good ecological status by the year 2015, it fixes the achievement of trends over space and time. The new requirements that arise from the WFD put considerable financial pressure on water management authorities. Because the overall decision-making process relies most of the time on acquired data, it puts considerable pressures on the display of high quality biological as well as chemical environmental measurements. However, performing measurements implies that i) the demonstration of their metrological traceability ii) the evidence of their achievement thanks to accurate and sensitive analytical methods and iii) their statement with a reliable estimate of expanded uncertainty is thoroughly addressed. Moreover, the measurement representativeness, especially in highly dynamic environment, is of prime interest in a context where comparability over space and time is needed. As a consequence, considerable challenges are dwelt on metrologists with great emphasis on parameters that are under regulation. This paper will discuss a panorama of the unavoidable metrological questions that have to be addressed: from the definition of the measurand to the final estimation of uncertainty; from the initial performances demonstration of methods to the final demonstration of mastery and capabilities through inter comparison laboratories and reference materials. A focus will be made on upcoming alternative monitoring approaches that are seldom addressed from a metrological point of view.