Phytoremediation as a sustainable technology for the rehabilitation and greening of former gasworks

Abstract

Gasworks are often contaminated with various contaminants such as organics, metals and cyanides. For the removal and/or control of these pollutants phytoremediation can offer a sustainable solution. Phytoremediation is the use of plants and their associated bacteria and fungi for the degradation, extraction or immobilization of soil and / or groundwater contamination. In case of natural phytoremediation, the degradation capacity remains uncontrolled. The degradation efficiency is affected by the plant species as well as by the present microorganisms. In order to ensure an efficient degradation, bacteria with the appropriate characteristics are enriched inside the plant by means of inoculation. Bacteria assisted phytoremediation can optimize the degradation process and prevent the spread of organic pollutants through evapotranspiration. In this work, we focus on the opportunities of phytoremediation on former gasworks, with particular attention to the phytoremediation of cyanide. Based on field observations on a contaminated site in Flanders we have learned that plants can grow on cyanide-contaminated soil. Different academic results confirm that grasses, herbaceous plants and trees, together with their associated microorganisms, are able to degrade free cyanides without accumulating cyanide in the leaves. There is no significant volatilization of cyanide from the leaves. These plant-microbe partnerships are able to degrade the free cyanides and provide stabilization of the contaminated soil. Moreover, percolation of rainwater through the contaminated soil is strongly reduced. Phytoremediation can be used as a soil remediation technique. Moreover, phytoremediation is useful for greening of contaminated sites. This can be of great value for people and ecosystems, not least in industrial and in residential areas. This means that phytoremediation is a very sustainable technology for the rehabilitation and / or greening of former gasworks.