Design and deployment of automated FI instrumentation for in the situ determination of mercury in natural waters Keywords: Mercury speciation; atomic fluorescence; preconcentration; Tamar estuary. Personnel: Paul Worsfold and |Mike Foulkes (supervisors), Kirsten Leopold (Postdoctoral Fellow) Funding body: Bayerische Forschungsstiftung Project duration: April 2008 – November 2008-05-20 The worldwide risk assessment of mercury in the environment is of great interest. The European Union lists mercury as one of the 33 priority pollutants and therefore its monitoring in the hydrosphere is regulated by law. However, analytical methods used for the routine determination of mercury at the ultra-trace level (pg l-1 to ng l-1 range) in natural waters (cold vapour – atomic fluorescence / absorption spectrometry; CV-AFS, CV-AAS) have significant drawbacks: They are time consuming, require a lot of manual process steps, use many reagents, some of which are extremely toxic and have high blank values due to reagents, storage and sampling procedures. Therefore, the aim of this research project is to develop a flow-injection analysis system (FIAS) for the simple and rapid determination of total dissolved mercury in natural waters. It is based on the separation and enrichment of mercury on a catalytically active nano-gold surface directly from the aqueous sample. For sensitive detection of mercury the enrichment column is dried and heated to release mercury vapour into the flow-through cell of an atomic fluorescence spectrometer (AFS). The direct enrichment of dissolved mercury species from the aqueous sample has several advantages compared with standard methods: No reagents are necessary for decomposition or cold vapour generation; low contamination risk; fully automated system and therefore useful for shipboard and other in situ monitoring. First investigations of real seawater samples with the newly developed FI method are very promising. The emphasis will be on the construction and deployment of automated FI instrumentation for the in situ determination of mercury in natural waters, i.e. outside the laboratory. A second aim will be to map the distribution of mercury in the Tamar catchment by shipboard and/or bankside deployments in order to provide immediate, high quality analytical information with good temporal and spatial resolution. This could enable detection of trends in the distribution of mercury and transient events such as pollution incidents. The obtained set of data – dissolved mercury concentrations in seawater, estuary, rivers and other freshwaters – could be enhanced by measuring in addition other important parameters, e.g. temperature, salinity, dissolved organic carbon, mercury bound to particles/colloids, etc. Interpretation of the data sets should help to increase our knowledge of mercury biogeochemistry in the aquatic system.
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