The risk assessment of heavy metals in the ecosystem of urban creeks

This paper is focused on risk assessment of heavy metals in freshwater ecosystems of urban creeks. The paper reports changes in an aquatic ecosystem leading to remobilization of heavy metals and consequently to changes of bioavailability. Concentrations of metals in water, bed sediment and benthic organisms from several small urban streams are monitored and evaluated. In the small urban streams studied copper, zinc and lead were determined as the most significant hazard metals. Although concentrations of these metals in water are very low (often below the detection limit of analytical equipment), concentrations in sediment were found in risky levels mainly in sampling sites affected by CSOs and SSOs from industrial and heavy traffic areas. The benthic organisms showed different ability to accumulate heavy metals (HM). The feeding type collector gatherer had in most cases the highest body concentration of HM and the predator species cumulate, to a high level, only zinc which has a high tendency to release from sediment, hence it is the most bio-available. The collector-filterer had mostly low values. The differences among species are due to the different feeding habits of each trophic level.