This is the third special issue of the Bulletin of Environmental Contamination and Toxicology (BECT) dedicated to soil and groundwater contamination and remediation. As was also the case for the previous two special issues, the studies included herein were the best presented in a special session of the 15th International Conference on Environmental Science and Technology (CEST2017) took place in Rhodes Island, Greece in September, 2017.

Soil and groundwater contamination is one of the most complex environmental problem faced nowadays by researchers and field engineers. The main problem characterizing this discipline is the heterogeneity of the environmental setting, where air, water and soil coexist with contaminants that are typically complex chemical substances with different fate and transport properties. Consequently, the cost of remediating contaminated sites is very high and close cooperation of practitioners and researchers is imperative to prioritize the most important of these, set the right remedial goals and choose sustainable remediation technologies. However, this is not always the case and most of times research and practice do not communicate in the most efficient way. The main reason for that is the different challenges that researchers and field engineers face in their professional life. In particular, researchers work under mostly ideal conditions where everything can be under control, while field engineers should investigate and work under the very complex site-specific field conditions, where little is really known and the costs of decisions that they should make are, most of the times, very high. On the other hand, the ideal laboratory conditions provide an environment appropriate to investigate complex subjects such as the contaminant mechanisms transformation, new remediation materials etc., which are impossible to be thoroughly studied under site-specific field conditions, where soil heterogeneity is the common situation.

Regarding the above challenges our aim is to make this CEST special session attractive not only for researchers but for practitioners as well, where they can share their views and field experiences and present interesting case studies. Therefore, not only researchers but practitioners as well are encouraged to present their sound scientifically works in CEST2019 (http://www.cest2019.gnest.org) and also publish their findings in BECT.

The Guest Editors would like to specially thank Dr Erin Bennett, the Editor-in-chief of BECT, for his help and co-operation and of course the authors and the reviewers participating.