The major pollution event caused by the breach of a dam containing red mud (a by-product of bauxite ore processing for alumina manufacture) at Kolontár in Hungary received widespread international media attention in early October 2010. This is the first event of its type and scale in Europe. While there have been similar events where dams holding mine wastes have failed, which are often acidic or rich in cyanide and ecotoxic metals, there have not previously been documented large scale releases of waste material with the extremely alkaline nature such as that released at Kolontár. Initial environmental monitoring at the site was focussed on the immediate impacts of the hyperalkaline (pH up to 13) water on the receiving streams, which had a major effect on instream organisms for over 50 miles. Beyond this short-term impact and given the lack of precedent for such events, we know relatively little about the longer-term behaviour of the potential contaminants released in the red mud. At other sites affected by hyperalkaline waters from red mud (albeit on a far smaller scale), such contaminants of concern include aluminium, arsenic, molybdenum and vanadium. This study aims to undertake a detailed analysis of the sediments and waters downstream of the spill to assess the nature and form of these, and other trace contaminants. This information is crucial to (a) characterise the spatial extent and severity of the polluted area, (b) assess which specific contaminants are present in the waters and sediments at levels of environmental significance and (c) understand the long-term prospects for mobility and availability of trace elements in the river systems downstream of Kolontár. Detailed sampling of the different phases (e.g. suspended in water, dissolved in water, settled on streambed) of contaminants along the impacted areas of the Marcal, Raba and Mosoni-Duna rivers will be undertaken. The field sampling will be coupled with laboratory tests on the mobility of contaminants in the sludge. Together, these data will help us understand the spatial trends in nature and form of contaminants and how key variables such as pH and the particle size distribution of the released materials are likely to affect their long term mobility in the environment. The work will be undertaken in liaison with scientists in Hungary and the outputs of the work will directly inform long-term management of the pollution spill. Beyond the direct relevance to management of the situation in Hungary, the improved understanding on how trace contaminants from caustic waste materials behave in the environment after such a major event will be useful for informing environmental management at other polluted sites.