| Popis: |
An extensive sampling campaign was organised in order to investigate the evolution of the mobility ofarsenic and zinc in function of the density of the loose sediments from the central part of the outer port(CDNB) of Zeebrugge (Belgium).For that purpose a newly designed multi-sample device, capable of sampling sediments in a profile witha wide density range , was successfully tested.The mobility of both heavy metals, chosen for their relative high pore water concentrations, was evaluatedby analysing different physico-chemical parameters, the evaluation of the distribution coefficientsand the determination of the SEM/AVS ratio.From the analysis it appears that the variation of most of the physico-chemical parameters of the loosesediment in the CDNB is limited, except in the top layer of the in-situ sediments.Evaluation of the distribution coefficients (Kd) showed that both metals show a sharp decrease of themobility with depth in the upper half meter of the sediment. Deeper in the sediment the mobility ofarsenic increases again with depth. On the contrary, the mobility of zinc decreases further with depth.The variation of the mobility of arsenic and zinc could significantly be correlated to the density. In generalthe mobility of arsenic is much higher compared to zinc.The distribution coefficients for arsenic compare very well with those found during earlier campaigns.For zinc instead there seems to be a large temporal variation of the distribution coefficient.The SEM to AVS ratios are all much smaller than 1, which means that no acute toxicity for heavy metalshas to be expected for bentic organisms. |
