Evaluation of mobile metals in sediments of Burullus Lagoon, Egypt

•Lagoons and coastal lakes act as contamination basins for pollutants.•Heavy metal distribution and its mobility in Burullus lagoon.•Concentration of metals is not sufficient to assess their environmental impact.•The total impact and the estimation of the bioavailable fraction are necessary.•Burullus Lagoon suffers from Zn and Cu accumulation and bioavailability.

The Burullus Lagoon north Nile Delta of Egypt is a UNESCO-protected area. Recently it has become a sediment sink which led to shrinking in its area and depth accompanying with increasing contaminant levels. In this study we attempt to explore the spatial distribution and their mobility of heavy metals (Zn, Cu, Ni, Cr and Pb) based on 21surface sediment samples recovered from Burullus lagoon basin and nine drains. The risk assessment code of the studied heavy metals can be arranged as Zn > Cu > Pb > Cr > Ni for all the samples collected from the lagoon basin and nine different drains. The heavy metals tend to accumulate in fine sediments and human activities promote the accumulation of contaminated sediments in water courses.