Spatial and time variation influence of some heavy metal ion species contents on the evolution of ecological risk

Environmental authorities are more and more involved in planning of the evaluation strategies for the ecological risks implied by sediments contamination. Nevertheless, the estimation of the long term effects of the sediments contamination is still difficult and implies a high degree of uncertainty. Sediments represent an important pollution source for the aquatic environment, because are the final accumulation medium for a multitude of organic or inorganic contaminants. This paper presents the investigations carried out on the quality of surface water and sediments collected from Abrud hydrographic basin affected by long lasting activity extraction of minerals. Investigations carried out have as purpose to establish the water quality Abrud river upstream and downstream of the pollution sources including Foiesu river (right tributary of Abrud) and also the changes induced upon them along investigated time period. It was also evaluated the partition of some metals (Cu, Cd) within all fractions defined by sequential extraction operations using the BCR (Community Bureau of Reference). Metal distribution in those fractions offers information on their bio-availability, which in turn allows aquatic environmental risk assessment. It is found that the risks induced by the two analyzed metals are changing according to the conditions of surface water flow, sediment composition punctual and weather conditions. It highlights for both heavy metals the positive evolution of environmental risk over time.