Urban impact on water bodies in the Luleå area, northern Sweden, and the role of redox processes

Sediment and water from urban water bodies in the Luleå area, northern Sweden, were studied to determine the degree of contamination from metals and PAHs (polycyclic aromatic hydrocarbons). The heavy metals Cd, Cu, Pb and Zn, which are of main concern in urban stormwater, are enriched in all investigated bays. PAH concentrations were also found to be enriched. The water and sediment quality of the investigated water bodies depends on catchment area characteristics and emission impact, from point sources in particular. Water volume and turnover rate in the water bodies with low water levels and no surface runoff during wintertime, and ice covering during winter, contribute to anoxic conditions in the water column and sediments. The present redox conditions in the water bodies predominantly cause fixation of pollutants in the sediment due to formation of sulphides and slow oxidation of organic pollutants. Postglacial land uplift implies continuous changes in the environment, which can lead to changing redox conditions, thereby necessitating new risk assessments.