Ecological remediation of urban legacy pollution: Developing a neosoil for marginal brownfield bioremediation

Canals are increasingly valued as an important green space providing recreational and ecological benefit in urban areas (Williams et al.,2010). However, their industrial past has left a legacy of polluted soils and sediments with associated poor water quality. As a result, large sections of the UK's canal network require significant remediation of heavy metals before being suitable for public use. The principal method of clean-up requires excavation and ex-situ remediation (Bromhead et al.,1994). This is often too costly for marginal public land and therefore an alternative, in-situ, low-cost method is needed to bring these areas back into beneficial use.

Recent advances in composting technology offer an opportunity to improve the environmental sustainability of in-situ bioremediation (Zhou et al.,2022). Natural chelating agents such as amino acids (Dolev et al.,2020) and other low-molecular-weight organic acids (Wang et al,.2019) provide promising new ways to improve remediation efficiency without the negative impacts on soil function and structure afforded by synthetic, non-biodegradable chelators such as EDTA (Jelusic and Lista 2014; Bloem et al.,1917). Similarly, plants with root exudates high in oxalic, galactonic and glyceric acid have been shown to effectively remove lead in contaminated soil (Luo et al,.2017).

Most research into heavy metal remediation is focused on a single or limited number of contaminants. However, this does not reflect in-situ legacy contamination where multiple contaminants are usually present at an individual site. For example, the Grand Union canal in Digbeth, Birmingham has nine heavy metal concentrations in excess of regulatory values (Fig.1). The novelty of this project is to focus on multi-contaminant removal via production of a low-cost "neosoil" that can be utilised at similarly contaminated sites in the UK.

The project's principal aim is to bring contaminated urban marginal land back into public use. Accordingly, the project will: (1) identify the best combination of soil amendments (e.g. natural/chelate/organic) for bio- and phytoremediation of heavy metal contaminants in soils; (2) examine potential negative consequences of remediation including increased mobility via changes in soil chemistry, leaching and partitioning into aboveground biomass; (3) create a neosoil template for low-cost remediation of similarly contaminated sites within the UK.