Environmental risk assessment on aquatic-terrestrial gradients in a freshwater tidal area

Environmental risk assessments are generally performed for either terrestrial or aquatic systems, while these systems sometimes exist in close proximity. The objective of this study is to compare environmental risks along gradients from aquatic to terrestrial conditions. The assessment involved chemical analysis (including bioavailable fractions), as well as bioassays and bioaccumulation experiments using aquatic and terrestrial organisms. The results demonstrate that sediments and soils from neighbouring aquatic and terrestrial systems may render different assessments in terms of environmental risks. Metal availability for oligochaetes appeared to be limited in the aquatic environment as compared to the terrestrial environment, while the reverse was observed for organic contaminants. This paper aims to illustrate the use of various assessment techniques within a framework to compare ecological risks in aquatic and terrestrial environments. The obtained results are useful when considering (a prioritisation of) remedial actions.