Gentle Remediation Options (GRO): A Literature Review (Part 1/2)

Soils are a non-renewable resource and comprise a key component of the world\u27s stock of natural capital. Due to industrialisation, urbanisation and other patterns of unsustainable development, widespread land degradation in the form of contamination, soil sealing, compaction, etc. has impaired the capacity of soils to perform their essential functions and provide humans with vital ecosystem services. Brownfields are typically urban or peri-urban sites that have been affected by the former uses of the site, are or are perceived to be contaminated, and require intervention to bring them back to beneficial use. They also constitute an important and underutilised land and soil resource to provide ecosystem services in urban areas as an element of green infrastructure through the use of nature-based solutions such as gentle remediation options (GRO). Within the scope of the Ph.D. project " Enhancing ecosystem services by innovative remediation using gentle remediation options (ECO-GRO)", an in-depth but inexhaustive literature review has been carried out to build a theoretical understanding of GRO for the overall research project. This literature review report (part 1 of 2) will present a compilation of the main findings by beginning with A) core concepts of GRO including the background of their usage and development as well as key physiological mechanisms and processes; then B) mechanisms for the gentle remediation of organic (i.e. degradation and volatilisation) and inorganic contaminants (i.e. extraction and stabilisation) are reviewed, including the various strategies for implementation, practical aspects, key limitations, the possibilities to enhance effectiveness by combining with soil amendments and compilations of field studies demonstrating successful application. GRO mechanisms that are more specific in use like rhizofiltration and phytohydraulics are also briefly discussed as well as other remediation techniques included under the GRO umbrella such as bioremediation, mycoremediation and vermiremediation; C) the development in the field towards applying GRO to both manage risks and provide wider economic, social and environmental benefits, i.e. phytomanagement, is discussed at some length while considering its broader implications; and finally D) suitable plants for the various GRO mechanisms are discussed throughout the report but a specific section is set aside to discuss methods for selecting the most suitable plants as well as summarising the most applied plants

Soil Functions and Ecosystem Services: A Literature Review (Part 2/2)

Soils are a non-renewable resource and comprise a key component of the world\u27s stock of natural capital. Due to industrialisation, urbanisation and other patterns of unsustainable development, widespread land degradation in the form of contamination, soil sealing, compaction, etc. has impaired the capacity of soils to perform their essential functions and provide humans with vital ecosystem services. Brownfields are typically urban or peri-urban sites that have been affected by the former uses of the site, are or are perceived to be contaminated, and require intervention to bring them back to beneficial use. They also constitute an important and underutilised land and soil resource to provide ecosystem services in urban areas as an element of green infrastructure through the use of nature-based solutions such as gentle remediation options (GRO). Within the scope of the Ph.D. project " Enhancing ecosystem services by innovative remediation using gentle remediation options (ECO-GRO)", an in-depth but inexhaustive literature review has been carried out to build a theoretical understanding of soil functions and ecosystem services for the overall research project. This literature review report (part 2 of 2) will present a compilation of the main findings by continuing with E) core concepts of soil biology, functioning and linkages to ecosystem services including how they can be delivered in healthy soils by functional assemblages of soil biota; then, F) methods for assessing soil quality are reviewed including potential physical, chemical and biological indicators, how they can be selected using a logical sieve approach, which standardised analyses exist to measure certain parameters as well as how they can be interpreted to give an indication of the status of certain aspects of soil functioning; G) quantitative, semi-quantitative and qualitative methods for assessing ecosystem services are also discussed, primarily within the context of urban or brownfield soils, and noteworthy examples are presented at some length as well as considerations for economic valuation of ecosystem services; and finally H) broader implications for land management and planning are considered in terms of managing soils to improve their quality and adaptive management and monitoring approaches to iteratively evaluate soils for their capacity to function and deliver ecosystem services over time. Also, how the breadth of information presented in this report can be transferred and applied at contaminated sites and marginal land to improve soil quality and provide much-needed ecosystem services, particularly in urban areas, is discussed

Gentle Remediation Options (GRO) for Managing Risks and Providing Ecosystem Services at Contaminated Sites

Soils are a non-renewable resource and comprise a key component of the world\u27s stock of natural capital. Due to industrialisation, urbanisation and other patterns of unsustainable development, widespread land degradation in the form of contamination, soil sealing, compaction, etc. has impaired the capacity of soils to perform their essential functions and provide humans with vital ecosystem services. Brownfields are typically urban or peri-urban sites that have been affected by the former uses of the site, are or are perceived to be contaminated, and require intervention to bring them back to beneficial use. They also constitute an important and underutilised land and soil resource to provide ecosystem services in urban areas as an element of green infrastructure through the use of nature-based solutions such as gentle remediation options (GRO). Gentle Remediation Options (GRO) are remediation measures involving plants, fungi, bacteria, and soil amendments that can be applied to manage risks at contaminated sites. Several studies and decision-support tools promote the wider range of benefits provided by GRO, including improving soil function to provide ecosystem services, but there is still scepticism regarding GRO implementation. Interviews with a small group of experts have elucidated some of the main possibilities and challenges for GRO implementation in Sweden. As a result, a risk management framework for GRO has been developed to strengthen the decision basis for GRO implementation in practice and address some of the key issues that need to be better communicated, including the various risk mitigation mechanisms, the required risk reduction for an envisioned land use, and the time perspective associated with the risk mitigation mechanisms. The framework is envisioned to be used as a tool for risk communication with stakeholders, decision-makers and regulatory agencies to identify GRO strategies for managing risks at contaminated sites and supporting phytomanagement for sustainable remediation and development. Two case studies are used to demonstrate the application of the risk management framework: Polstj\ue4rnegatan and Kolleberga

Comparison of PFAS soil remediation alternatives at a civilian airport using cost-benefit analysis

Contamination of soil and water systems by per-and polyfluoroalkyl substances (PFAS) due to uncontrolled use of aqueous film-forming foams (AFFFs) at firefighting training sites at civilian and military airports is a universal issue and can lead to significant human health and environmental impacts. Remediation of these sites is often complex but necessary to alleviate the PFAS burden and minimise the risks of exposure by eliminating the hotspot/source from which the PFAS spreads. This study presents a probabilistic cost-benefit analysis (CBA) for evaluating PFAS reme-diation alternatives, which includes monetisation of both direct costs and benefits as well as externalities. The method is applied for a case study to compare five remediation alternatives for managing PFAS contaminated soil at Stockholm Arlanda Airport in Sweden. The social profitability, or the net present value (NPV), of each remediation alternative was calculated in comparison to two reference alternatives - 'total excavation' of the site (Alt 0) or 'do nothing'. Sensitivity analyses and model scenarios were tested to account for uncertainties, including small or large PFAS spreading and simulating different values for the magnitude of annual avoided cost of inaction (i.e., aggregate benefit) from PFAS re-mediation. In comparison to total excavation, four of the five studied remediation alternatives resulted in a positive mean NPV. Excavation and stabilization/solidification of the hotspot on-site combined with stabilization using acti-vated carbon for the rest of site (Alt 2) had the highest NPV for both spreading scenarios, i.e., Alt 2 was the most so-cially profitable alternative. Simulations of the annual avoided cost of inaction enabled estimation of the breakeven point at which a remediation alternative becomes socially profitable (NPV > 0) compared to 'do nothing'. Alt 2 had the lowest breakeven point: 7.5 and 5.75 millions of SEK/year for large and small spreading, respectively

Comparison of PFAS soil remediation alternatives at a civilian airport using cost-benefit analysis

Contamination of soil and water systems by per- and polyfluoroalkyl substances (PFAS) due to uncontrolled use of aqueous film-forming foams (AFFFs) at firefighting training sites at civilian and military airports is a universal issue and can lead to significant human health and environmental impacts. Remediation of these sites is often complex but necessary to alleviate the PFAS burden and minimise the risks of exposure by eliminating the hotspot/source from which the PFAS spreads. This study presents a probabilistic cost-benefit analysis (CBA) for evaluating PFAS remediation alternatives, which includes monetisation of both direct costs and benefits as well as externalities. The method is applied for a case study to compare five remediation alternatives for managing PFAS contaminated soil at Stockholm Arlanda Airport in Sweden. The social profitability, or the net present value (NPV), of each remediation alternative was calculated in comparison to two reference alternatives – ‘total excavation’ of the site (Alt 0) or ‘do nothing’. Sensitivity analyses and model scenarios were tested to account for uncertainties, including small or large PFAS spreading and simulating different values for the magnitude of annual avoided cost of inaction (i.e., aggregate benefit) from PFAS remediation. In comparison to total excavation, four of the five studied remediation alternatives resulted in a positive mean NPV. Excavation and stabilization/solidification of the hotspot on-site combined with stabilization using activated carbon for the rest of site (Alt 2) had the highest NPV for both spreading scenarios, i.e., Alt 2 was the most socially profitable alternative. Simulations of the annual avoided cost of inaction enabled estimation of the breakeven point at which a remediation alternative becomes socially profitable (NPV > 0) compared to ‘do nothing’. Alt 2 had the lowest breakeven point: 7.5 and 5.75 millions of SEK/year for large and small spreading, respectively

A risk management framework for Gentle Remediation Options (GRO)

Gentle Remediation Options (GRO) are remediation measures involving plants, fungi, bacteria, and soil amendments that can be applied to manage risks at contaminated sites. Several studies and decision-support tools promote the wider range of benefits provided by GRO, but there is still skepticism regarding GRO implementation. Key issues that need to be better communicated are the various risk mitigation mechanisms, the required risk reduction for an envisioned land use, and the time perspective associated with the risk mitigation mechanisms. To increase the viability and acceptance of GRO, the phytomanagement approach implies the combination of GRO with beneficial green land use, gradually reducing risks and restoring ecosystem services. To strengthen the decision basis for GRO implementation in practice, this paper proposes a framework for risk management and communication of GRO applications to support phytomanagement strategies at contaminated sites. The mapping of the risk mitigation mechanisms is done by an extensive literature review and the Swedish national soil guideline value model is used to derive the most relevant human health exposure pathways and ecological risks for generic green land use scenarios. Results indicate that most of the expected risk mitigation mechanisms are supported by literature, but that knowledge gaps still exist. The framework is demonstrated to support the identification of GRO options for the case study site given two envisioned land uses: biofuel park and allotment garden. A more easily understandable risk management framework, as proposed here, is expected to act as a communication tool to educate decision-makers, regulatory bodies and other stakeholders for better understanding of risk mitigation mechanisms and preliminary timeframes of various GRO, particularly in the early stages of a brownfield redevelopment project