Short Rotation Intensive Culture of Willow, Spent Mushroom Substrate and Ramial Chipped Wood for Bioremediation of a Contaminated Site Used for Land Farming Activities of a Former Petrochemical Plant

Abstract

The aim of this study was to investigate the bioremediation impacts of willows grown in short rotation intensive culture (SRIC) and supplemented or not with spent mushroom substrate (SMS) and ramial chipped wood (RCW). Results did not show that SMS significantly improved either biomass production or phytoremediation efficiency. After the three growing seasons, RCW-amended S. miyabeana accumulated significantly more Zn in the shoots, and greater increases of some PAHs were found in the soil of RCW-amended plots than in the soil of the two other ground cover treatments’ plots. Significantly higher Cd concentrations were found in the shoots of cultivar ‘SX61’. The results suggest that ‘SX61’ have reduced the natural attenuation of C10-C50 that occurred in the unvegetated control plots. The presence of willows also tended to increase the total soil concentrations of PCBs. Furthermore, we found that many contaminant concentrations were subject to seasonal oscillations, showing average increases throughout the whole experimental site after a growing period, while showing significantly different variations, such as lesser increases or even decreases, after a dormant period. These observations suggest that contaminants may have leached or degraded faster in untreated conditions, and conversely to have mobilized towards trees through water flow driven by plant transpiration during growing seasons.

Willows Used for Phytoremediation Increased Organic Contaminant Concentrations in Soil Surface

“…In past phytoremediation field experiments, our study group has observed stable, but also increased soil pollutant concentrations under a specific willow plantation (Salix miyabeana 'SX61' and 'SX64'), even after almost a decade of cultivation [6,17], contrary to initial hypotheses and objectives. The main findings concerning the establishment (first year) of this plantation can be found in Guidi et al [6].…”

“…At the beginning of the fifth growing season (corresponding to the T0 in Fortin Faubert et al [17]), all analyzed contaminants on the site were found in significantly higher concentration under willows than under the control treatment. We hypothesized that the absence of convincing soil decontamination under the willow plantation could be attributable to the attraction of the dissolved contaminant fraction towards the root zones, facilitated by the high evapotranspiration rate of willow fields under SRIC management.…”

“…(B) the second experimental phase (phase 2) studied by Fortin Faubert et al [17]. Colored areas refer to the experimental plots supplemented with spent mushroom substrates (SMS) and/or with ramial chipped wood (RCW), or simply left as bare ground (BG).…”

“…The second experimental phase (Figure 1B) aimed to investigate the bioremediation impacts of both cultivars ('SX61' and 'SX64') supplemented or not with spent mushroom substrates (SMS) of Pleurotus ostreatus and ramial chipped wood (RCW) of Salix spp. [17]. The effect of RCW was investigated alone, as well as in combination with SMS.…”

“…Regular maintenance was necessary to eliminate regrowth of the trees. All experimental plots were laid where no ground cover treatment had been applied in the previous experimental phase (no soil amendments, referred as bare ground (BG) in Fortin Faubert et al [17]).…”