Traceability of oxidized mercury measurements in air

The direct measurement of gaseous Hg(II) has become a major focus of international research programmes for continuous source emission and ambient measurement and monitoring. These measurements are dependent on the availability of reliable Hg(II) gaseous reference standards and materials to assess and verify the quality of data. The EURAMET has approved a project in the framework of the European Metrology Programme for Innovation and Research related to comparability of oxidized Hg measurements - MercOx. The overall objective is a traceable on-line and sorbent-based measurement for the monitoring and control of mercury in its different oxidized forms in emission sources and in the atmosphere in order to achieve significant improvements in measurement uncertainty and comparability. The specific objectives are: (1) To develop, establish and implement a traceable calibration methodology for the most important oxidized mercury species. (2) To study, develop and compare different methods of measuring oxidized mercury and to validate high accuracy bulk and species-specific [e.g. Hg(0) and Hg(II)] isotope ratio measurements for origin discrimination and to determine migration pathways of mercury and mercury species interconversion in air. (3) To compare, develop and establish conversion and sample transportation methods employing traceable reference standards developed for Hg(0) and oxidized mercury. Species inter-conversion methodologies are based on enriched stable isotopes methods as well as radiotracer techniques based on the use of highly specific 197-Hg radiotracer prepared from 196-Hg enriched stable isotope. (4) To apply the developed methodologies in order to test and validate new and existing methods for on-line mercury measurement under field conditions. The aim of the presentation is to provide an overview and up-date of the main results achieved so far and invite participants to collaborate as stakeholders.