Introduction

Understanding and manipulating the microbial ecology of contaminated land are increasingly critical steps towards meeting the challenge of remediating the considerable legacy of industrial pollution in the UK and worldwide.

Understanding the microbial ecology of contaminated land is key to its remediation in two ways. First, the microbial community in the soil, occasionally enhanced through inoculation, can be exploited to bioremediate (through either in situ or ex situ approaches) contaminated sites (Alexander 1999; Atlas & Philp 2005). This is an increasingly attractive, environmentally sustainable option as excavation and landfill of contaminated site waste become both increasingly expensive (both through landfill tax increases, ever-increasing transport costs and the introduction of the aggregrate levy on material brought in as fill), fewer landfill sites are available (in Scotland, for example, there are no hazardous landfills and material must be transported great distances, further adding to disposal costs) and environmental regulators rightly press for more sustainable approaches to site clean-up. Second, the indigenous microbial communities of sites are often impacted by the contamination, particularly where toxic contaminants such as free phase solvents and available heavy metals are present, and part of the remediation challenge is to restore soil/aquifer biological function. Because of the wide range of microbial functions carried out in the soil, in particular, this restoration may be linked, for example, to carbon and nutrient (N, P and S) cycling or to the wide range of plant–microbe interactions on which ecosystem health depends.