Leaching Properties of Estuarine Harbor Sediment Before and After Electrodialytic Remediation

Electrodialytic remediation (EDR) can be used to extract heavy metals from a variety of different media. In this work, contaminated harbor sediments from two locations in the United States and one in Norway were subjected to EDR, and were compared with batch extractions conducted with the sediment. pH-dependent leaching tests were used to evaluate changes in leaching properties of treated and control sediments. Significant fractions of total concentrations were removed during treatment (35–95% with an average of 75% for all sediments and elements investigated). The release of elements in pH-dependent leaching tests, however, demonstrated equal or greater leaching from treated sediments in the neutral pH range. Dissolved organic carbon appears to be a significant contributor to post-treatment increases in leaching, and dissolution of significant iron and aluminum sorption sites is hypothesized to also play a role. This research highlights the importance of understanding contaminant speciation and availability, as total metals concentrations, in this particular case, do not relate to estimates of the environmental availability of metals (total concentrations were typically two to three orders of magnitude greater than concentrations released during pH-dependent leaching)