The ability to (i) characterize the fate of contaminants or to (ii) engineer the behaviour of soil and rock is reliant on a thorough understanding of the physical, chemical and microbial processes which may occur naturally or which may be actively enhanced in the subsurface for engineering purposes. The transport and transformation of pollutants and microbially mediated processes for ground improvement are strongly influenced by flow, groundwater chemistry, microbial activity, heterogeneity in the subsurface, and by mineral/geochemical interface properties. Two aspects are of particular interest: (i) assessing contaminant fate in the subsurface and (ii) engineering the hydraulic and mechanical properties of the subsurface using microbially mediated processes.

(i) Serious pollution due to the release of contaminants in the subsurface remains of great concern. A thorough understanding of the processes governing the transport and transformation of contaminants is needed to predict aquifer vulnerability, to improve remediation strategies of soil and groundwater contaminations, and to address sustainable use of our water resources. This session encourages presentations of recent developments, state-of-the-art tools and techniques, and innovative instrumentation, sampling techniques and measurement / monitoring approaches to assess vulnerability, sustainability, risk and remediation approaches in the unsaturated and/or saturated zone. Of particular interest are studies on flow, microbial activity and reactive transport, as well as the use of isotope signatures and analogue compounds as tracers for contaminant source / provenance and for process identification / quantification.

(ii) In recent years there has been a significant increase in research related to the control of microbially mediated processes for the purpose of altering the hydraulic and mechanical properties of soil, rock and groundwater systems. A major focus of this research has been on microbially induced calcite precipitation (MICP) as a technique for reducing permeability in porous and fractured media, for soil stabilisation and for inhibiting the migration of both contaminants in groundwater and CO2 from underground storage sites. In order to design successful engineered systems for application in the field, it is important that the fundamental physical, chemical and biological processes governing these microbially mediated reactions are understood. Nevertheless, there are also many challenges related to the upscaling of these processes from the laboratory to the field scale which also demand attention from researchers for the successful application of these processes to real world engineering problems. Of interest are studies covering experimental testing, constitutive and numerical modelling and particularly contributions related to field trials and case studies.