SF Box--a tool for evaluating the effects on soil functions in remediation projects

A method for evaluating the effects of gentle remediation options (GRO) on soil health: Demonstration at a DDX-contaminated tree nursery in Sweden

Healthy soils provide valuable ecosystem services (ES), but soil contamination can inhibit essential soil functions (SF) and pose risks to human health and the environment. A key advantage of using gentle remediation options (GRO) is the potential for multifunctionality: to both manage risks and improve soil functionality. In this study, an accessible, scientific method for soil health assessment directed towards practitioners and decision-makers in contaminated land management was developed and demonstrated for a field experiment at a DDX-contaminated tree nursery site in Sweden to evaluate the relative effects of GRO on soil health (i.e., the 'current capacity' to provide ES). For the set of relevant soil quality indicators (SQI) selected using a simplified logical sieve, GRO treatment was observed to have highly significant effects on many SQI according to statistical analysis due to the strong influence of biochar amendment on the sandy soil and positive effects of nitrogen-fixing leguminous plants. The SQI were grouped within five SF and the relative effects on soil health were evaluated compared to a reference state (experimental control) by calculating quantitative treated-SF indices. Multiple GRO treatments are shown to have statistically significant positive effects on many SF, including pollutant attenuation and degradation, water cycling and storage, nutrient cycling and provisioning, and soil structure and maintenance. The SF were in turn linked to soil-based ES to calculate treated-ES indices and an overall soil health index (SHI), which can provide simplified yet valuable information to decision-makers regarding the effectiveness of GRO. The experimental GRO treatment of the legume mix with biochar amendment and grass mix with biochar amendment are shown to result in statistically significant improvements to soil health, with overall SHI values of 141 % and 128 %, respectively, compared to the reference state of the grass mix without biochar (set to 100 %).

Changes in the health of metal-contaminated soil before and after stabilization and solidification

Stabilization is popularly employed to remediate metal-contaminated soils. It involves the absorption and precipitation of heavy metals to reduce their solubility, movement characteristics, or risk and toxicity. This study aimed to conduct a soil health assessment to determine changes in the health of metal-contaminated soil before and after the application of five stabilizers (acid mine drainage sludge (AMDS), coal mine drainage sludge (CMDS), steel slag, lime, and cement). Soil health assessment, including three soil functions, namely soil productivity, soil stability, and soil biodiversity, evaluated the physical, chemical, and biological indicators (total 16 indicators). Soil health index (SHI) of soil function was calculated by multiplying each indicator score by the weighting factor of each indicator. Total SHI was obtained by summing the three soil-function SHI. Total SHI of the stabilized and test soils followed the order as control soil (1.90) > heavy metal-contaminated soil (1.55) > CMDS-stabilized soil (1.29) > steel slag-stabilized soil (1.29) > AMDS-stabilized soil (1.26) > cement-stabilized soil (0.74) > lime-stabilized soil (0.67). Total SHI of the initial heavy metal-contaminated soil was evaluated as 'normal', before the stabilizer was applied; however, most of the stabilized soils became 'bad' after application of the stabilizers. Furthermore, soils stabilized by cement and lime showed very poor soil health. The results implied that changes in physical and chemical soil properties occurred due to the disturbance caused by the mixing of stabilizers, and ions eluted from the stabilizers could deteriorate soil health further. The findings indicated that soil treated with stabilizers is not suitable for agricultural purposes. Overall, the study suggested that stabilized soil from metal-contaminated sites should be covered with clean soil or monitored for some time before deciding its future agricultural use.

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.

Application of a soil quality assessment system using ecotoxicological indicators to evaluate contaminated and remediated soils

The deterioration of soil quality owing to human activities results in adverse effects on the soil ecosystem. This study developed a systematic method to quantitatively evaluate soil quality based on physical, chemical, biological, and ecotoxicological indicators and proposed the soil quality assessment and management system. This system consists of step-by-step processes, including indicator classification, indicator measurement, scoring and weighting, and soil quality index (SQI) calculation. The novel strategy included the usage of authentic ecotoxicological indicators for realistically interpreting soil quality assessment results. This study used five ecotoxicological indicators, including earthworm survival, enzyme activities, nematode reproduction, plant germination and growth, soil algal biomass, and soil algal photosynthetic capacity. Relatively higher SQI values than those corresponding to the actual soil quality status would be obtained without considering the ecotoxicological indicators. We conclude that the use of ecotoxicological indicator can help in soil quality assessment even under extreme soil quality conditions, such as highly contaminated or physically and chemically remediated soils.

Assessing costs and benefits of improved soil quality management in remediation projects: A study of an urban site contaminated with PAH and metals

Contaminants in the soil may threaten soil functions (SFs) and, in turn, hinder the delivery of ecosystem services (ES). A framework for ecological risk assessments (ERAs) within the APPLICERA - APPLICable site-specific Environmental Risk Assessment research project promotes assessments that consider other soil quality parameters than only contaminant concentrations. The developed framework is: (i) able to differentiate the effects of contamination on SFs from the effects of other soil qualities essential for soil biota; and (ii) provides a robust basis for improved soil quality management in remediation projects. This study evaluates the socio-economic consequences of remediation alternatives stemming from a Tier 1 ERA that focusses on total contaminant concentrations and soil quality standards and a detailed, site-specific Tier 3 Triad approach that is based on the APPLICERA framework. The present study demonstrates how Tier 1 and Tier 3 ERAs differ in terms of the socio-economic consequences of their remediation actions, as well as presents a novel method for the semi-quantitative assessment of on-site ES. Although the presented Tier 3 ERA is more expensive and time-consuming than the more traditional Tier 1 ERA approach, it has the potential to lower the costs of remediation actions, decrease greenhouse gas emissions, reduce other environmental impacts, and minimise socio-economic losses. Furthermore, the remediation actions stemming from the Tier 3 ERA were predicted to exert far less negative ES effects than the actions proposed based on the results of the Tier 1 ERA.

Assessing Impacts of Soil Management Measures on Ecosystem Services

Only a few studies have quantified and measured ecosystem services (ES) specifically related to soil. To address this gap, we have developed and applied a methodology to assess changes in ecosystem services, based on measured or estimated soil property changes that were stimulated by soil management measures (e.g., mulching, terracing, no-till). We applied the ES assessment methodology in 16 case study sites across Europe representing a high diversity of soil threats and land use systems. Various prevention and remediation measures were trialled, and the changes in manageable soil and other natural capital properties were measured and quantified. An Excel tool facilitated data collection, calculation of changes in ecosystem services, and visualization of measured short-term changes and estimated long-term changes at plot level and for the wider area. With this methodology, we were able to successfully collect and compare data on the impact of land management on 15 different ecosystem services from 26 different measures. Overall, the results are positive in terms of the impacts of the trialled measures on ecosystem services, with 18 out of 26 measures having no decrease in any service at the plot level. Although methodological challenges remain, the ES assessment was shown to be a comprehensive evaluation of the impacts of the trialled measures, and also served as an input to a stakeholder valuation of ecosystem services at local and sub-national levels.

A model for prioritizing landfills for remediation and closure: A case study in Serbia

The existence of large numbers of landfills that do not fulfill sanitary prerequisites presents a serious hazard for the environment in lower income countries. One of the main hazards is landfill leachate that contains various pollutants and presents a threat to groundwater. Groundwater pollution from landfills depends on various mutually interconnected factors such as the waste type and amount, the amount of precipitation, the landfill location characteristics, and operational measures, among others. Considering these factors, lower income countries face a selection problem where landfills urgently requiring remediation and closure must be identified from among a large number of sites. The present paper proposes a model for prioritizing landfills for closure and remediation based on multicriteria decision making, in which the hazards of landfill groundwater pollution are evaluated. The parameters for the prioritization of landfills are the amount of waste disposed, the amount of precipitation, the vulnerability index, and the rate of increase of the amount of waste in the landfill. Verification was performed using a case study in Serbia where all municipal landfills were included and 128 landfills were selected for prioritization. The results of the evaluation of Serbian landfills, prioritizing sites for closure and remediation, are presented for the first time. Critical landfills are identified, and prioritization ranks for the selected landfills are provided. Integr Environ Assess Manag 2018;14:105-119. © 2017 SETAC.