Potential contaminant release from agricultural soil and dredged sediment following managed realignment

Purpose Laboratory experiments were conducted to examine the potential for metal (Cu, Ni and Zn) and herbicide (simazine, atrazine and diuron) release from agricultural soil and dredged sediment in managed realignment sites following tidal inundation. Materials and methods Column microcosm and batch sorption experiments were carried out at low (5 practical salinity units, psu) and high (20 psu) salinity to evaluate the changes in the partitioning of metals and herbicides between the soil/sediment and the aqueous phase, and the release of metals and herbicides from soil/sediment to the overlying water column. Results and discussion For both the metals and herbicides, the highest contaminant loads were released from the sediment within the first 24 h of inundation suggesting that any negative impacts to overlying water quality in a managed realignment scheme will be relatively short term following tidal inundation of soil and sediment. The release of metals was found to be dependent on a combination of salinity effects and the strength of binding of the metals to the soil and sediment. In the case of the herbicides, salinity impacted on their release. Particulate organic carbon was found to control the binding and release of the herbicides, highlighting the importance of assessing soil and sediment organic matter content when planning managed realignment sites. Conclusions Our research demonstrates that metals and herbicides may be released from contaminated sediments and agricultural soils during initial periods of flooding by seawater in managed realignment sites.