HYDROLOGICAL AND HYDROCHEMICAL CONTROLS ON FE, NOM AND AS MOBILITY

Fe and natural organic matter (NOM) are known to be important controls on the mobility of arsenic in natural waters (Bauer and Blodau 2009), both through alteration of chemical speciation and particle size. Because of the many conditions in which interaction between Fe, NOM and toxic metals can occur in a natural setting prediction of the mobility of toxic metals remains uncertain (Gaffney, White et al. 2008). This project aims to determine the influence of Fe and NOM on toxic metals under environmentally relevant conditions. This will involve an iterative process of laboratory simulation and field monitoring. In the laboratory the mixing order of Fe, NOM, As and O2 will be controlled so as to simulate the possible hydrological pathways of these components from the subsurface to streamwater. The pH of the system will be both controlled and used to monitor the interactions. Various other parameters will be monitored in real time and the end products will be analysed by ultrafiltration and subsequent TOC analysis, ICP-AES, ICP-MS, HPLC-ICP-MS. A field monitoring programme will be run in parallel in an upland peat catchment in which Fe, NOM and As are known to be components of runoff. The aim being to identify environmentally relevant mixing regimes and to collect samples from a known hydrological context for comparison to the laboratory simulations. Furthermore, the distribution of As within and the magnitude of its flux from this environment will be determined. The student working on this cross-disciplinary project will gain training in field monitoring techniques, tangential flow ultra filtration and/or size exclusion chromatography, UV absorption, UV fluorescence, (pyr) GC-FID and will have access to world-class facilities in the Williamson Research Centre for Molecula