The effect of vegetation on soil polluted with galligu: phytostabilisation and novel approaches to evaluate soil galligu concentration

The Sighthill area, situated north of the River Clyde in Glasgow, is polluted with the waste product galligu as a consequence of past activities associated with the alkali industry. As this area is planned for redevelopment, it is necessary to explore feasible ways of polluted soil decontamination. An experimental laboratory survey was conducted to assess whether phytostabilisation could be a suitable strategy to limit the mobilisation of galligu within contaminated soil. For this purpose, two different types of vegetation were tested-namely, a male dwarf fern (Dryopteris affinis (Lowe) Fraser-Jenk) and alfalfa (Medicago sativa L.). Laboratory experiments were conducted using readily available materials to study both the axial and vertical movements of galligu in the soil as a result of heavy-rainfall events. In addition to this research, original and simple methods were tested to assess whether it was possible to estimate galligu content within a soil volume. The results showed that sediment loss was reduced by 84 and 94% under fern and alfalfa covers, respectively, compared with fallow soil. The concentrations of galligu in the sediments from fern and grass treated soil were 59 and 62% lower, respectively, than that under fallow soil conditions. Furthermore, alfalfa was observed to be more effective in containing galligu, since the fern root systems may have allowed the contaminant to percolate towards the bottom of the soil. Turbidity- A nd colour-based analyses were able to give an estimation of the concentration of galligu in the soil effectively. The results of this research are directly applicable to phytoremediation actions on polluted soils and to the assessment of synthetic soil pollutants using simple and inexpensive methods.