Evaluation of innovative and gentle in situ remediation strategies to manage risks and improve ecosystem services (PILOT-GRO)

Research Project, 2021 – 2024

Gentle remediation options (GRO) involve plants, fungi, bacteria and soil amendments and are found to be feasible for contaminated sites with medium and low ecological and human health risks1,2,3,4, and can improve ecological soil functions and in turn provide ecosystem
services vital for human well-being4,5,6. Stakeholders’ confidence in GRO has suffered due to e.g. their application at unsuitable sites but their credibility has increased with research advances and potentially strong community acceptance4,9,10. GRO are often promoted as low-cost, innovative, nature-based and sustainable strategies but seldom used in Sweden as regulators may still be hesitant to approve GRO as remediation strategies because of real or perceived uncertainties, time requirements or when the contamination is
left in place as legal frameworks often predicate contaminant removal or destruction to reach the contaminant concentration targets4,11. There is a need to better understand and
communicate the potential of different GRO strategies to properly manage risks, the time perspectives of GRO as well as their benefits. PILOT-GRO is a separate initiative aimed to complement the PhD project ECO-GRO through a practical field trial to reach the
following specific objectives of PILOT-GRO: a) to plan and implement a field scale trial of GRO at a former forest nursery using plants and biochar; b) to evaluate the results from the field trial in terms of i) GRO effectiveness to manage risks, including time perspectives, as
well as ii) GRO effects on soil quality and restoring or preserving ecosystem services; c) to evaluate the wider societal benefits of GRO at the field trial site; and d) to develop a generic working process to identify suitable GRO strategies based on site-specific
conditions and the relevant risk mitigation mechanisms different GRO strategies provide. A former forest nursery will be used for field trials as this type of site: 1) is a good example of sites contaminated above generic soil guideline values over large areas (several hectares), potentially posing human health and ecological risks12; 2) are usually contaminated with organic pollutants in the upper soil layers within the root zone; 3) in general possesses high values in terms of high quality soils which can provide provisioning, regulating and cultural ecosystem services and which are difficult, or impossible to recreate by traditional excavation remediation; 4) represent a large scale problem in Sweden of which former forest nurseries account for several hundreds of hectares of soil with similar geological type settings, contaminated with DDT and its metabolites DDE and DDD (henceforth DDX).
Together with other plant nurseries, of which many are DDX contaminated, these sites account for about 750 sites of risk class 1 and 212.