Risk-based Remediation Research Articles

In situ thermal remediation application in South Africa: a case study incorporating sustainable remediation principles

This paper presents a case study of the first instance in South Africa where in situ thermal remediation (ISTR) was undertaken. The project, completed during 2020 and 2021, is located in Cape Town. The ‘site’ is a former printing facility located in a multistorey building adjacent to an upgradient service station. Petroleum hydrocarbon impacts, identified in subsurface soil and groundwater, originated from leaking underground fuel storage tanks at this service station. Following a sustainability-based options appraisal, ISTR with steam used as the heating source was selected as the most appropriate remedial technology. Based on Environmental Resources Management's (ERM's) international and local expertise, this solution was implemented after due consideration of the site's geological characteristics, the properties of the contaminants of concern and the client's goals of rapidly achieving a risk-based remediation solution. This solution was enhanced by the identification and incorporation, where feasible, of sustainable management practices (SMPs) in the system design and operational phases. Particular focus was placed on resource consumption and the use of alternative power sources, such as reduction of water and energy and the use of biofuel. Other SMPs incorporated into the system's operational phase included temperature tracking to optimize steam usage, which has been successfully applied by ERM at previously completed ISTR sites in other countries. Key lessons learnt from the ISTR application at this site were that the energy source and use, combined with the optimization of water consumption, could be more widely applied to improve the sustainability of ISTR, not only in South Africa but also in other sites worldwide. Supplementary material: Details of sustainable remediation assessments are available at https://doi.org/10.6084/m9.figshare.c.5965339 . Thematic collection: This article is part of the Sustainability in Engineering Geology & Hydrogeology collection available at: https://www.lyellcollection.org/cc/sustainability-in-engineering-geology-and-hydrogeology

A Single Soil Washing with Humic Substance Can Achieve the Risk-Based Remedial Target for Nickel Contaminated Soil.

Risk-based soil remediation and management have become a global environmental issue. Here, a nickel (Ni)-contaminated site was selected to conduct the risk-based remediation strategy. The Health and Environment Risk Assessment Software was used to calculate the human health risk and the remedial target value (RTV) of Ni. Soil highly contaminated with Ni (424.30mgkg-1) could cause an unacceptable carcinogenic risk (1.41 × 10-6), which needs further remediation. Hence, a soluble humic substance (HS) was used as the washing agent to remove Ni. After a single wash at pH 4 and 8, the Ni concentrations in soil were reduced to 278.05 and 288.27mgkg-1, both below the RTV (300mgkg-1). Furthermore, sequential extraction analysis revealed that the residual Ni was maintained stably in the soil after HS washing. These findings suggested that HS is a promising washing agent for Ni-contaminated soil remediation under the guidance of risk control.

A rapid experimental protocol to determine the desorption resistant fraction of sediment-sorbed hydrophobic organic contaminants.

Desorption of hydrophobic organic contaminants (HOCs) from sedimentary materials plays a vital role in dictating the fate and transport of HOCs in the environment. Desorption irreversibility is a commonly observed phenomenon in laboratory sorption/desorption studies of HOCs. A desorption-resistant fraction (DRF) typically exists during the desorption process. To correctly evaluate the DRF of HOCs can considerably contribute to the understanding of availability and bioavailability of HOCs. This can substantially benefit contaminant remediation and cleanup operations. Conventional batch method to measure the DRF replies on repetitive washing of the sediments, which is time-consuming and can be impractical. This study presents an experimental protocol to quantify the DRF of the sediment-sorbed organic contaminants in a rapid manner. This protocol utilizes cosolvent to expedite desorption kinetics and adopts an ultrafiltration/centrifugation combined method to achieve a complete separation of sediment and solution phases. This proposed experimental protocol can facilitate the quantification of the DRF of sorbed contaminants to understand and minimize the uncertainties associated with risk-based pollution remediation approach. This protocol has the potential to be widely used in environmental studies to characterize sorption and desorption properties of HOCs with soil and sedimentary materials.

Remediation of soil and water contaminated with petroleum hydrocarbon: A review

Abstract The global use of petroleum hydrocarbons for energy and raw materials in various applications has increased with extensive release of a wide variety of contaminants into the environment, affecting soil, surface water and groundwater. The effect results to numerous health, ecological and environmental issues. However, treatment of contamination and pollution caused by petroleum hydrocarbons is a huge and laborious work. It involves several in situ or ex situ treatments comprising containment, separation and destruction which include biological, chemical, physico-chemical, thermal and heat, electric and electromagnetic, acoustic and ultrasonic treatment methods. These treatment methods involve several other techniques and strategies as listed in this review. The health risks pose by petroleum hydrocarbon pollution have driven scientists to research, develop and implement risk-based remediation strategies for restoration and reclamation of affected environments. To select the best treatment option for remediation, it is important to comprehend the nature, composition, properties, sources of pollution, type of environment, fate, transport and distribution of the pollutants, mechanism of degradation, interaction and relationships with microorganisms, the intrinsic and extrinsic factors affecting remediation. It helps to evaluate and predict the chemical behaviour of the pollutants with the short and long-term effects and mitigate the effects of pollution and limit exposure to the pollutants. Despite the available remediation options for petroleum hydrocarbon management and removal, sufficient and complete remediation can be implemented by adoption of proper approach derived from risk-based management procedure that can be practical, scientifically defensible, widely adapted, sustainable, non-invasive, eco-friendly and cost-efficient. This paper provides an overview of the various remediation and treatment technologies derived from risk-based approaches that are used for isolation, containment, separation, restoration reclamation and remediation of soil, sediments, surface water and groundwater contaminated by petroleum hydrocarbons and organic compounds.

Uncertainty analysis of remediation cost and damaged land value for brownfield investment

Flexible land management that allows risk-based remediation approaches can increase local financial assistance in brownfield development investments. The evaluation of brownfields investment has always been mired in uncertainty because of the complexity of contamination and land policy. To clarify the uncertainty in investment costs resulting from a flexible risk-based land management, this research analyzes the uncertainty of remediation costs (Ir) and damaged land value (Ip). Sizable statistical data for 30,000 abandoned factories in Taiwan are used to derive the uncertainty of investment cost. The results show that the range and value of the uncertainty of Ip is more than Ir because the present land value and the change in flexible land management are the main sensitivity factors. The saved investment costs at the 90% confidence interval ranges five orders of magnitude. Moreover, investors could have saved approximately 5.74E+13 USD resulting from Ip and Ir. The study's two major findings with regard to investment risk in brownfield redevelopment are: (1) an explanation of the extent to which investment costs are to be reduced for investors by adjusting remediation goals depending on different land types; (2) characterization of the uncertainty of brownfields in the real investment market for brownfield redevelopment.

Petroleum hydrocarbons (PH) in groundwater aquifers: An overview of environmental fate, toxicity, microbial degradation and risk-based remediation approaches

Abstract Petroleum hydrocarbon (PH) contamination of soil and aquatic ecosystems is a serious global issue. PH are classified as xenobiotics and emerging priority pollutants. When released into the environment, fate and behavior of PH varies widely with the particular composition and physicochemical properties. Usually, PH with higher molecular weight are toxic and seldom mobilizes in subsurface plumes when compared to their low molecular weight counterparts. Due to the toxic, mutagenic and carcinogenic nature of PH, various remediation approaches are currently employed for their clean-up from the environment. Degradation of PH by the activity of native microbes is considered as a significant eco-friendly and cost effective approach for the remediation of PH contaminated sites. Changes in the microbial adaptations and dynamics are important indicators for monitoring the effects of PH contamination. Several analytical techniques are available for the identification and quantification of PH present in contaminated sites. Also, toxicity tests are widely employed to monitor the effect of remediated sites where analytical techniques fall short to identify certain PH due to the lack of standardized methods and low concentrations. Consequently, this review provides an overview of environmental fate, toxicity, and remediation of PH with particular emphasis on risk-based remediation which considers the use of both analytical and toxicological studies for effective management and remediation of PH contaminated sites.

Comparison of international approaches to sustainable remediation

Since mid-to-late 2000s growing interest for sustainable remediation has emerged in initiatives from several international and national organisations as well as other initiatives from networks and forums. This reflects a realisation that risk-management activities can about bring environmental, social, and economic impacts (positive or negative) in addition to achieving risk-based remediation goals. These ideas have begun to develop as a new discipline of “sustainable remediation”. The various initiatives have now published a number of frameworks, standards, white papers, road maps and operative guidelines. The similarities and differences in the approaches by these outputs and general trends have been identified. The comparison is based on a set of criteria developed in discussion with members of these various initiatives, and identifies a range of similarities between their publications. Overall the comparison demonstrates a high level of consensus across definitions and principles, which leads to the conclusion that there is a shared understanding of what sustainable remediation is both across countries and stakeholder groups. Publications do differ in points of detail, in particular about the operational aspects of sustainable remediation assessment. These differences likely result from differences in context and legal framework. As this analysis was carried out its findings were debated with members of the various international initiatives, many of whom have been included as authors. Hence the outcomes described in this paper can be seen as the result of a sort of multi-level debate among international experts (authors) and so can offer a starting point to new sustainable remediation initiatives (for example in other countries) that aim to start developing their own documents.

Assessment of Human Health Risk for an Area Impacted by a Large-Scale Metallurgical Refinery Complex in Hunan, China

ABSTRACTDue to accelerated urbanization and reform of industrial structure in China, polluting industries in major cities have been closed or relocated. Consequently, large numbers of industrial sites were generated and the contaminated soils on and around these sites may pose risks to humans. This case study presents an estimation of human health risks for an area that is mainly impacted through air dispersion and deposition from a large-scale metallurgical refinery complex in Zhuzhou city, Hunan Province, China. Carcinogenic and non-carcinogenic risks posed by the contaminants were estimated under future industrial and residential land use scenarios. The result shows that adverse health effects may occur primarily through ingestion of soils contaminated with As, Cd, and Pb. The total carcinogenic risks of multiple contaminants for a large area exceed the acceptable risk level of 1 × 10−5, and several localized hotspots, where the total hazard index exceeds 1 were identified. Soils in the Tongda site pose the highest carcinogenic risks and non-carcinogenic hazards. It is concluded that potential human health risks exist under the proposed redevelopment scenarios, and development of risk-based remediation strategies is recommended.

The Development of Risk-Based Remediation Target Value for Lead Contaminated Soils

With the rapid economic development, China is experiencing increased land contamination and lead poisoning problem in recent years, which is no longer restricted to isolated incidents and locations. There is an urgent need to remediate the lead contaminated soils to protect the publics health. However, contaminated land remediation and determination of remediation target value has been neglected for years. In order to accommodate uncertainties within the conservative point estimation of remediation target value for lead contaminated soils, Monte Carlo simulation technique is integrated into the traditional calculation model from a probabilistic perspective. Risk-based remediation target values for lead contaminated soils of different land use types (including school/hospital, residential, business and industrial use) are developed preliminarily. Furthermore, this study highlights the necessity to determine the remediation target value on the basis of actual (i.e. site-specific) risks to humans and, besides, actual risks due to contaminant migration.

Bioavailability and ecotoxicity of arsenic species in solution culture and soil system: implications to remediation

In this work, bioavailability and ecotoxicity of arsenite (As(III)) and arsenate (As(V)) species were compared between solution culture and soil system. Firstly, the adsorption of As(III) and As(V) was compared using a number of non-allophanic and allophanic soils. Secondly, the bioavailability and ecotoxicity were examined using germination, phytoavailability, earthworm, and soil microbial activity tests. Both As-spiked soils and As-contaminated sheep dip soils were used to test bioavailability and ecotoxicity. The sheep dip soil which contained predominantly As(V) species was subject to flooding to reduce As(V) to As(III) and then used along with the control treatment soil to compare the bioavailability between As species. Adsorption of As(V) was much higher than that of As(III), and the difference in adsorption between these two species was more pronounced in the allophanic than non-allophanic soils. In the solution culture, there was no significant difference in bioavailability and ecotoxicity, as measured by germination and phytoavailability tests, between these two As species. Whereas in the As-spiked soils, the bioavailability and ecotoxicity were higher for As(III) than As(V), and the difference was more pronounced in the allophanic than non-allophanic soils. Bioavailability of As increased with the flooding of the sheep dip soils which may be attributed to the reduction of As(V) to As(III) species. The results in this study have demonstrated that while in solution, the bioavailability and ecotoxicity do not vary between As(III) and As(V), in soils, the latter species is less bioavailable than the former species because As(V) is more strongly retained than As(III). Since the bioavailability and ecotoxicity of As depend on the nature of As species present in the environment, risk-based remediation approach should aim at controlling the dynamics of As transformation.

PRELIMINARY INVESTIGATION AND RISK ASSESSMENT OF CONTAMINATION ON AN INDUSTRIAL SITE IN MARAMURES COUNTY

Sites contaminated with hazardous material are a topical and urgent problem all over the world. Risk based remediation is used to develop maximum safety cost effective sanitation methods for future land users. The analyzed site lays within the North Western region of Romania, in the vicinity of Baia Mare, the main city in Maramures County. Taking into account the former activities conducted on the site, as well as future demolishing works and future developments, analyses to certain contaminants in soil, groundwater and building materials were performed. The level of pollution based on Romanian regulations was established. The paper further presents a human health risk assessment and determines the contaminated area on the site. Two most suitable risk-based remediation actions for the site were proposed.

Containment of groundwater pollution (methyl tertiary butyl ether and benzene) to protect a drinking-water production site in Belgium

The subsurface migration of methyl tertiary butyl ether (MTBE) and benzene towards a drinking-water production site in Belgium was monitored for 9 years. A large gasoline spill at a nearby fuel station had caused a 500-m long and 50-m-wide pollution plume of MTBE (10−30 mg/L) and benzene (2−10 mg/L). In order to prevent any intrusion of pollutants into the drinking-water supply, a conceptual model was used to design a pump-and-treat system that intercepted the gasoline-contaminated groundwater emanating from the spill. The contaminated soil in the spill zone was excavated. A numerical mass transport model was developed to evaluate the ongoing plume containment. The model describes the subsurface MTBE migration and was regularly updated, based on groundwater monitoring data and the measured mass of MTBE extracted with the pump-and-treat system. With continued interception pumping, the MTBE plume can be remediated in 14 years. Without it, MTBE and benzene concentrations up to 600 μg/L could have reached the drinking-water production site and the plume would persist for 9 years longer. Source zone treatment combined with plume interception pumping is a suitable risk-based remediation strategy for the containment of MTBE and benzene groundwater pollution.

Sub‐Saharan African Ground Water Protection—Building on International Experience

Sub-Saharan Africa faces significant challenges in dealing with ground water pollution. These countries can look to successes and missteps on other continents to help choose their own individual paths to ensuring reliable and clean supplies of ground water. In the large view, sub-Saharan Africa can define specific levels of acceptable risk in water quality that drive cleanup efforts and are amenable to acceptance across national and geographic boundaries. Ground water quality databases must be expanded, and data must be available in an electronic form that is flexible, expandable, and uniform, and that can be used over wide geographic areas. Guidance from other continents is available on well construction, sampling and monitoring, interim remediation, technical impracticability, monitored natural attenuation, and many specific issues such as how to deal with small waste generators and septic contamination of water supply wells. It is important to establish a common African view on the appropriateness of other nations' ground water quality guidance for African issues, economic conditions, and community circumstances. Establishing numerical, concentration-based, water quality action levels for pollutants in ground water, which many neighboring African nations could hold comparable, would set the stage for risk-based remediation of contaminated sites. Efforts to gain public, grass-roots understanding and support for stable and balanced enforcement of standards are also key. Finally, effective capacity building in the region could be an eventual solution to ground water quality problems; with increased numbers of trained environmental professionals, ground water throughout the region can be protected and contaminated sites cleaned up.

Characterizing Attribute Distributions in Water Sediments by Geostatistical Downscaling

Information about attributes such as contaminant concentrations or hydraulic properties in benthic sediments is typically obtained in core sections of varying lengths, and only the average value is measured in each section. However, an estimate of the attribute distribution at a uniform spatial resolution is often required for site characterization and the design of appropriate risk-based remediation alternatives. Because attributes exhibit spatial autocorrelation, geostatistical methods have become an essential tool for estimating their spatial distribution. The purpose of this paper is to optimally infer the spatial distribution of sampled attributes at a uniform resolution from fluvial core sampling data, using a downscaling technique formulated as a geostatistical inverse problem. We compare geostatistical downscaling to the more traditional approach of point-to-point ordinary kriging for a hypothetical case study, and for total organic carbon observations from the Passaic River, New Jersey. Although frequently used to interpolate measurements, ordinary kriging is shown not to be able to estimate the spatial distribution of attributes accurately, because this approach assumes that data are sampled at a uniform resolution. Geostatistical downscaling, on the other hand, is shown to resolve this problem by explicitly accounting for the relationship between the known average measurements and the unknown fine-resolution attribute distribution to be estimated.

Assessment of the sanitary and environmental risks posed by a contaminated industrial site

Sites contaminated with hazardous material are a topical and urgent problem all over the world. In accordance with recent Italian regulations, appropriate risk assessment is required in order to determine health risks associated with contaminated sites. The paper presents a case study regarding a disused industrial plant contaminated with polycyclic aromatic hydrocarbons, heavy hydrocarbons and polychlorinated biphenyls. The site is characterized by three different topographical levels. Therefore both the characterization and the conceptual model had to be adapted to the site conditions: we divided the site into three discrete areas and we developed a separate risk assessment for each area. Besides health risk assessment, we performed ecological risk assessment for both groundwater and surface water targets, as required by Italian regulations. The future reuse scenario has not yet been defined and, consequently, risk assessment results will be useful for the remediation program. Risk assessment was supported by leaching tests and hydrocarbon “finger printing”. Leaching tests allowed us to determine site-specific soil–water partition coefficient. Hydrocarbon “finger printing” allowed us to differentiate the mobility of the different hydrocarbon groups in migration analyses. We found the site required remediation based on Italian standard. We propose a simple risk-based remediation action consisting in the replacement of the upper 1m with “clean” soil and the placement of a barrier to vapors.

Application of current risk-based remediation criteria for the post-closure assessment of a former National Priorities List (NPL) site

Hurricane accelerated erosion and land loss of the Mississippi River coastal zone has necessitated a re evaluation of environmental risk at closed National Priority List (NPL) industrial waste sites in Louisiana, USA. Clean up criteria of a site were evaluated under the Louisiana Risk Evaluation Corrective Action Program (RECAP 2003). An assessment of the closed site using RECAP 2003 indicated that hexachlorobutadiene remained at concentrations greater than allowable soil saturation limits. Several Constituents of Concern (COCs) exceeded RECAP 2003 human health risk standards. The findings support the need for continued assessment and field validation of closed NPL sites in coastal environments.

A spatial risk assessment methodology to support the remediation of contaminated land

When soil and groundwater contaminations occur over large areas, remediation measures should be spatially prioritised on the basis of the risk posed to human health and in compliance with technological and budget constraints. Within this scope, the application of human health risk assessment algorithms in a spatially resolved environment raises a number of methodological and technical complexities. In this paper, a methodology is proposed and applied in a case study to support the entire formulation process of remediation plans, encompassing hazard assessment, exposure assessment, risk characterisation, uncertainty assessment and allocation of risk reduction measures. In the hazard assessment, it supports the selection of Contaminants of Concern (CoC) with regard to both their average concentrations and peak concentrations, i.e. hot spots. In the exposure assessment, it provides a zoning of the site based on the geostatistical mapping of contaminant. In the risk characterisation, it generates vector maps of Risk Factors on the basis of the risk posed by multiple substances and allows the interrogation of most relevant CoC and exposure pathways for each zone of the site. It also supports the Monte Carlo based probabilistic estimation of the Risk Factors and generates maps of the associated uncertainty. In the risk reduction phase, it supports the formulation of remediation plans based on the stepwise spatial allocation of remediation interventions and the on-time simulation of risk reduction performances. The application of this methodology is fully supported by an easy-to-use and customized Geographical Information System and does not require high expertise for interpretation. The proposed methodology is the core module of a Decision Support System (DSS) that was implemented in the DESYRE software aimed at supporting the risk-based remediation of megasites.

Assessment of Health Protectiveness of the Risk-Based Soil Remediation Standards of the Midwestern States

ABSTRACT In the last decade, risk-based remediation following a framework similar to risk-based correction action (RBCA) has gained acceptance across the country and generic/Tier 1 Risk-Based Action Limits (RBALs) for hundreds of chemicals have been tabulated. However, there have been only a few studies that focused on understanding the causes of discrepancy among cleanup standards and policies of the hazardous waste programs among the states. This study aims to fill this critical need by examining the basis of generic (i.e., Tier 1) residential RBALs developed by the states, which are within the regulatory domain of U.S. Environmental Protection Agency's Region 5. Specifically, we seek to investigate the approaches/methodologies and the policy/technical rationale used in establishing RBALs, along with degree of inconsistency, and the causes and implications of inconsistencies. In addition, we developed RBALs for a case study site using both deterministic and probabilistic risk assessment approaches and compared these against RBALs developed by the states to infer about public health-protectiveness of the state-specific RBALs. We found three- and four-order-of magnitude difference among state RBALs for PAHs and VOCs, respectively. The degree of clean up deemed appropriate under Tier 1 evaluation by the midwestern states significantly differ from one another, which has both public health and economic implications.

Risk-based remediation of a former MGP site in Italy

Risk-based remediation of a former MGP site in Italy

Challenges in Monitoring the Natural Attenuation of Spatially Variable Plumes

Monitored natural attenuation may be applied as a risk-based remediation strategy if it can be established that contaminants are or will be reduced to some acceptable level at or before a compliance point. Contaminant attenuation is often attributed to intrinsic biodegradation, which in some circumstances may occur only at the plume fringes where electron acceptors from the surrounding uncontaminated zones mix by dispersion and diffusion with the plume. However, due to the common spatial and temporal variability exhibited by many plumes, the centreline monitoring approaches advocated in many natural attenuation protocols may be unable to detect natural attenuation occurring primarily by fringe processes. Snapshot data from a multilevel sampling well transect across an MTBE plume at Vandenberg Air Force Base, CA, USA, illustrate the difficulty of centreline monitoring and the challenge of providing sufficient detail to detect attenuation processes that may be occurring primarily at plume fringes. In a study of a phenols plume in Wolverhampton, UK, high-resolution multilevel wells demonstrated that the key biodegradation processes were restricted spatially to the upper fringe of the plume and were rate-limited by transverse dispersion and diffusion of electron acceptors into the plume. Thus the overall extent of biodegradation was considerably less than suggested by a plume-scale analysis of total electron acceptor and contaminant budgets. These examples indicate that more robust and cost-effective MNA assessments can be obtained using monitoring strategies that focus on the location of key biodegradation processes.