Utilization of PCB-contaminated Hudson River sediment by thermal processing and phytoremediation

The need to dispose of dredged sediments and development of appropriate technology for their safe utilization has become a growing problem in recent years. It has been proposed that dredged, fresh sediments can be utilized in agriculture or environment; however there is also growing interest in the use of thermally-treated sediments. Hence, the aim of this study was threefold: 1) to evaluate the effect of two incineration temperatures (300 °C and 600 °C) on the chemical and ecotoxicological properties of sediment; 2) select the appropriate treatment for further phytoremediation experiments with zucchini; and 3) assess the impact of sediment admixture on the physico-chemical parameters of soil, based on the responses of Aliivibrio fischeri and growth of zucchini (Cucurbita pepo L. cv 'Black Beauty'). A range of chemical (inductively-coupled plasma optical emission spectrophotometry for macro- and trace elements; gas chromatography for polychlorinated biphenyls (PCBs)), ecotoxicological (Microtox assay), and plant morphology (biomass measurement) as well as physiological analyses (spectrophotometry for chlorophyll) were applied. River sediments incinerated at 600 °C resulted in better chemical and ecotoxicological properties than incinerated at 300 °C or no incinerated. Incineration at 600 °C removed PCBs from sediment. In culture experiments conducted with zucchini, sediment treated at 300 °C demonstrated a 51-81% reduction in PCB concentrations compared to untreated sediment. After four weeks of growth, the raw sediment showed a significant increase in K, Fe, Cr, Pb, Zn concentrations, whereas the thermally-processed sediment showed a decrease in Ca, Na, P, Cd, Cu, Ni, and Zn concentrations. Both the fresh and thermally-treated sediment types influenced plant growth positively: they demonstrated higher biomass production than plants grown in control soil; however, plants grown on soil with thermally-processed sediment demonstrated lower biomass than those grown in raw sediment. Chlorophyll content was affected negatively by admixtures of soil with treated or untreated sediment, while a lower chlorophyll a/b ratio was observed in plants grown on an admixture of thermally-treated sediment with soil. Our findings suggest that the use of sediments as a growth medium component may be a promising way for their utilization and transformation from waste material to a valuable resource enhancing the benefits to the environment.