8 minute read
Contamination and remediation
Aerial view of abandoned copper mine. © Ashley Hampson
Soil contamination requires a multidisciplinary approach and a willingness to explore innovative techniques to address both current and future challenges.
Soil: generally taken for granted, yet such a precious asset that requires significant effort to protect from contamination and negative human influence. As an environmental consultant, I have spent almost two decades attempting to understand and address soil contamination. This is a multifaceted and critical issue that impacts our ecosystems, our health, and our efforts towards sustainable development.
Sources of soil contamination
Where does soil contamination come from? Contamination types have changed over time and encompass a wide variety of pollutants: pesticides and herbicides used in agricultural practices; the introduction of large quantities of heavy metals and chemicals into soils during the Industrial Revolution; an accumulation of high concentrations of naturally occurring substances such as metals; the widespread use of synthetic chemicals; and those arising from mine workings, urbanisation, and improper waste management and disposal. Emerging contaminants, such as PFAS (per- and polyfluoroalkyl substances, or ‘forever chemicals’ as they are often called) and microplastics are revealed all the time, as our lifestyles change and new technologies are developed. Each contaminant requires a thorough understanding of its provenance, management, and mitigation options. Additionally, every site may have a unique mix of contaminants associated with its use and history. It is worth mentioning that some chemicals and materials were once considered safe (for example asbestos) but scientific advancement has since disproven this and exposed the extent of potential harm. In the UK, as a relatively small country formed of islands, there are few places that haven’t been influenced by the people who have colonised and lived here, so virgin soils are limited.
This article focuses on contamination in soil, but consideration is also given to the impact on the water environment, including contamination of soil leachate, groundwater, and surface water.
Consequences
Contaminated soil disrupts natural ecosystems by affecting the health and diversity of soil organisms. Microorganisms, fungi, and plants play crucial roles in maintaining soil structure and fertility. Contaminants can inhibit their growth and function, leading to reduced soil productivity and altered nutrient cycles. Contaminated soil also directly impacts the safety of our food crops since plants can absorb harmful chemicals from the soil, which then enter the food chain and pose risks to human and animal health. This is particularly concerning for communities that rely on locally grown produce for their sustenance.
Exposure to contaminated soil arises through direct contact, inhalation of dust, or consumption of contaminated food and water. Associated health risks include respiratory problems, skin irritations, neurological disorders, and an increased risk of cancers. Vulnerable populations, such as children and the elderly, are particularly at risk and assessment of contamination should take into account the sensitivity of the environment, inhabitants and visitors. Soil contamination can have far-reaching consequences for our environment and health.
How do we decide whether land is contaminated or not?
At this point, it is pertinent to distinguish between land contamination (land that may be affected) and contaminated land (when harm has been proven or there is the significant possibility of significant harm to either human health or controlled waters); as defined by Part 2a of the Environmental Protection Act 1990.
For Part 2a, an assessment of the potential for harm should be undertaken where contaminants are present. An equivalent assessment for pollution is undertaken for controlled waters. In both scenarios, consideration should be given to potential sources of contamination, pathways, and receptors so that a viable pollutant linkage may be identified between all three components.
Contamination assessment
Assessment of contamination may be undertaken for a variety of reasons, such as:
– Managing existing issues, perhaps associated with the site’s history
– Dealing with new pollution events, for example spills and leaks
– To determine liability
– In support of a planning application for redevelopment or to comply with building regulations
– At the instigation of regulating authorities, for example under Part 2a of the Environmental Protection Act 1990 or Environmental Damage (Prevention and Remediation) Regulations (EDR)
– For voluntary action to remediate a site or situation
Conducting a thorough assessment and quantifying risk is crucial to understanding the land. The assessment generally requires the identification of the types and extent of contamination and unacceptable risks through the development of a Conceptual Site Model (CSM). The CSM guides further investigations and evaluates potential sources of contamination, their severity, and how they may behave with available exposure pathways (routes) to something that could be affected, known as a receptor. If a complete pollutant linkage, with a viable source, pathway, and receptor, is identified, this is usually the point at which consideration is given to further investigation and assessment, with the potential for subsequent remediation or mitigation.
In the UK, we have the Land Contamination Risk Management (LCRM) guidance, which is advocated as an iterative and phased process to capture sufficient contamination information. This enables a robust assessment of risks and the provision of a scheme for their remediation and mitigation.
Regulatory compliance, ensuring that all activities comply with local, regional and national regulations, is vital and can entail obtaining necessary permits and adherence to environmental standards. The effectiveness of soil contamination management depends on the regulatory framework in place: policies and regulations must be strict enough to prevent contamination and ensure proper remediation of contaminated sites. However, inconsistencies in regulations across regions can complicate efforts to address soil contamination on a global scale.
Challenges in soil contamination management
The challenges of managing soil contamination, from identifying contamination sources to implementing effective remediation strategies, are numerous.
Selecting the appropriate remediation techniques is crucial for successful soil contamination management. LCRM includes an options appraisal to assess the suitability of the site to minimise or remedy the effects of the identified risks. Traditional methods, including soil excavation and landfilling, can be disruptive and costly and are not finite solutions. Innovative approaches, such as bioremediation, phytoremediation, and soil washing offer more sustainable alternatives but require further research and development to optimise their efficacy.
An effective remediation strategy should be tailored to the specific conditions of the site and requires the selection of appropriate technologies. The feasibility, cost, and potential impact of each option must be considered in addition to a sustainability cost-benefit appraisal.
The Sustainable Remediation Forum UK (SuRF UK) is an initiative to evolve sustainable land management and remediation. Remediation activities themselves can sometimes cause environmental disturbances and unintended consequences that must be carefully managed. Hence it is often difficult to design a one-sizefits-all remediation plan. Consideration should also be given to both the potential effects of climate change and the use of chemical or biological additives to soil and groundwater that may treat specific contaminants but have uncertain longevity. In some circumstances, synergies between treatment and development may be exploited, such as stabilisation and solidification, where contaminants in the soil matrix are treated and the soil is consequently geotechnically improved.
Remediating contaminated soil often involves significant financial investment. The costs associated with site assessment, remediation technologies, and long-term monitoring can be prohibitive, particularly for developing countries and small-scale industries. Balancing economic feasibility with environmental protection is a persistent challenge.
Plans for the future
Continued research and the development of innovative remediation technologies are crucial to the sustainable treatment of soil contamination. Collaborative efforts between academia, industry, and government can accelerate the advancement and deployment of effective remediation methods. In the UK there are several professional bodies that further the efforts of those working in industry and produce a wide range of supporting documents and resources for sustainable development. The Remediation Society (RemSoc) is one such group, established by a group of professionals and practitioners working in the remediation sector and focused on addressing related environmental challenges.
RemSoc aims to promote best practice, share knowledge, and drive innovation in land regeneration through collaboration with like-minded organisations.
The focus of RemSoc’s 2024 conference was ‘Rethinking Remediation’ and its aim was to explore alternatives to engineered or chemical technologies for contaminated soils. We were fortunate to be joined by eminent professionals for a discussion around soil science and the Reconstructed Soils from Waste Project. This considered the potential for nature-based solutions to balance the needs of carbon mitigation, biodiversity, flood management, and water supply.
Conclusion
Soil contamination presents a complex and multifaceted challenge that requires coordinated efforts from many stakeholders. By understanding the sources, impacts, and management strategies associated with soil contamination, we can develop effective solutions to protect our environment and ensure the wellbeing of future generations. It is our responsibility to advocate for sustainable practices and contribute to the global efforts in combating soil contamination.
Elizabeth Beers is a Chartered Environmentalist with over 18 years’ experience in land contamination, geotechnics, and remediation. She is the current Chair of the Remediation Society and Regional Director for Ground and Water at WSP in the UK.
