The effects of climate change on land contamination and selected contaminants
Laura Thain
The Environment Agency
laura.thain@environment-agency.gov.uk
Joanne Kwan
CIRIA
joanne.kwan@ciria.org
ECG Bulletin July 2022
The Environment Agency
laura.thain@environment-agency.gov.uk
Joanne Kwan
CIRIA
joanne.kwan@ciria.org
ECG Bulletin July 2022
Climate change provides new and enhanced challenges for chemical regulation. The Environment Agency’s Chemicals Programme is working to identify key evidence gaps and commission research to improve our understanding of chemical and climate risks and actions we can take to reduce environmental impacts.
Like all countries around the world, the UK’s climate is changing and will continue to change because of greenhouse gas emissions. Even with global action, further climate change is now inevitable. Changing rainfall patterns are predicted, resulting in wetter winters, increases in winter runoff and mobilisation of contaminants, drier summers, and more extreme rainfall events. Hotter temperatures may result in increased wildfires and associated use of foams and fire suppressants as well as use of perfluorinated alkyl substances (PFAS)-containing ground source cooling schemes. Under drought scenarios, less water is available for attenuation and dilution or dispersion, resulting in higher concentrations of contaminants. Climate change impacts can lead to increased mobilisation of hazardous chemicals, as well as affecting their fate and transport.
Agricultural land use patterns, pest control requirements and human behaviour are all likely to alter in response to climate change. As a result, chemical use and associated risks will also change, as will treatment technologies and energy demands
Like all countries around the world, the UK’s climate is changing and will continue to change because of greenhouse gas emissions. Even with global action, further climate change is now inevitable. Changing rainfall patterns are predicted, resulting in wetter winters, increases in winter runoff and mobilisation of contaminants, drier summers, and more extreme rainfall events. Hotter temperatures may result in increased wildfires and associated use of foams and fire suppressants as well as use of perfluorinated alkyl substances (PFAS)-containing ground source cooling schemes. Under drought scenarios, less water is available for attenuation and dilution or dispersion, resulting in higher concentrations of contaminants. Climate change impacts can lead to increased mobilisation of hazardous chemicals, as well as affecting their fate and transport.
Agricultural land use patterns, pest control requirements and human behaviour are all likely to alter in response to climate change. As a result, chemical use and associated risks will also change, as will treatment technologies and energy demands
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Project scope and findings
The Environment Agency worked with the Construction Industry Research and Information Association (CIRIA) on a literature review and industry consultation looking at the effects of climate change on land contamination and the behaviour and remediation of selected contaminants, specifically polychlorinated biphenyls (PCBs), brominated flame retardants (BFRs), poly- and perfluorinated alkyl substances (PFASes) (1, 2) mercury, volatile organic compounds (VOCs), and asbestos. Changes in ambient, soil or groundwater temperature, or in soil moisture and composition, could change the behaviour of contaminants, compromising quantitative risk assessments and the effectiveness of remediation approaches such as bioremediation, cover systems, permeable reactive barriers and monitored natural attenuation (Figure 1). |
Figure 1. Visual summary of extreme weather events and climate impacts on selected contaminants (P. Nathanail, paul@lqm.co.uk).
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Extreme weather events, such as heatwaves, cold snaps, storms, droughts, exceptionally intense precipitation, and wildfires, can affect all land remediation techniques during the implementation phase. Wet weather with intense rainfall and flooding are seen as the biggest climate change concerns for land contamination projects.
Remediation solutions which break the contaminant linkage by removing the contaminant source, destroying, detoxifying or relocating the contaminants, are a permanent solution, and therefore less vulnerable to climate impacts. However, remediation solutions that operate over a longer time period, such as pathway interruption, which involves either stopping the pathway (e.g. capping or hydraulic containment) or gradually removing the contaminant (e.g. permeable reactive barrier) are more vulnerable to climate impacts. Remediation solutions that depend on the physical integrity of a barrier are also vulnerable to extreme weather events, especially erosion of cover systems. Long-term pathway interruption techniques are additionally susceptible to the chronic effects of climate change and associated environmental changes, such as sea level rise.
Remediation solutions which break the contaminant linkage by removing the contaminant source, destroying, detoxifying or relocating the contaminants, are a permanent solution, and therefore less vulnerable to climate impacts. However, remediation solutions that operate over a longer time period, such as pathway interruption, which involves either stopping the pathway (e.g. capping or hydraulic containment) or gradually removing the contaminant (e.g. permeable reactive barrier) are more vulnerable to climate impacts. Remediation solutions that depend on the physical integrity of a barrier are also vulnerable to extreme weather events, especially erosion of cover systems. Long-term pathway interruption techniques are additionally susceptible to the chronic effects of climate change and associated environmental changes, such as sea level rise.
The study found that remediation techniques for PCBs, PFAS, BFRs, asbestos and mercury often involve erodible cover systems, including soils, which are vulnerable to extreme weather events such as flash flooding or compromising the integrity of capping material.
PFAS remediation techniques may also be vulnerable to changing groundwater conditions caused by extreme weather events, which could bypass or overwhelm groundwater and surface water management systems. The solubility of many PFAS means that reducing water infiltration should also be a design requirement.
Mercury requires different remediation and containment techniques depending upon whether it is in contaminated sediment, groundwater or soils. These techniques could be compromised by extreme weather events, leading to erosion from brief but significant increases in surface water velocity, changes in groundwater flow velocity, periods of extreme precipitation and climate impacts on soil chemistry.
VOC plume pathway interruption strategies, such as monitored natural attenuation and permeable reactive barriers, are susceptible to environmental changes in groundwater velocity and composition. Changes to the chemistry of groundwater as a direct or indirect result of long-term climate change may alter the ability of indigenous microorganisms to degrade contaminants. Climate impacts which result in fluctuating groundwater levels, saline intrusion, and rising soil temperatures, may impact volatilisation. Some bioremediation techniques are vulnerable to strong winds and intense precipitation.
Climate change is expected to lead to increased release of asbestos fibres during very strong winds and periods of prolonged drought or extreme heat. However, wet conditions would significantly suppress fibre release.
PFAS remediation techniques may also be vulnerable to changing groundwater conditions caused by extreme weather events, which could bypass or overwhelm groundwater and surface water management systems. The solubility of many PFAS means that reducing water infiltration should also be a design requirement.
Mercury requires different remediation and containment techniques depending upon whether it is in contaminated sediment, groundwater or soils. These techniques could be compromised by extreme weather events, leading to erosion from brief but significant increases in surface water velocity, changes in groundwater flow velocity, periods of extreme precipitation and climate impacts on soil chemistry.
VOC plume pathway interruption strategies, such as monitored natural attenuation and permeable reactive barriers, are susceptible to environmental changes in groundwater velocity and composition. Changes to the chemistry of groundwater as a direct or indirect result of long-term climate change may alter the ability of indigenous microorganisms to degrade contaminants. Climate impacts which result in fluctuating groundwater levels, saline intrusion, and rising soil temperatures, may impact volatilisation. Some bioremediation techniques are vulnerable to strong winds and intense precipitation.
Climate change is expected to lead to increased release of asbestos fibres during very strong winds and periods of prolonged drought or extreme heat. However, wet conditions would significantly suppress fibre release.
How seriously is the industry considering climate change?
Although climate change is recognised as a concern by many in writing contaminated land reports, this is mainly qualitatively, and only a small minority carried out sensitivity analyses to assess the effects of climate change on contaminant physical chemical properties. There is currently no consistent approach to the ‘shelf’ life of either land contamination risk assessments or remediation design.
Excavation and disposal to landfill are still commonly used remediation techniques for some contaminants. There is almost no documented experience of the UK industry remediating BFRs and PFASes and relatively little experience of PCBs and mercury. This reflects the emerging nature of BFRs and PFASes as contaminants of concern and how relatively rarely PCBs and mercury are encountered on UK sites.
There is currently limited practical guidance on how to consider climate change, and what guidance there is seems to be not widely known. Advice is needed on the design, construction and long-term maintenance of cover systems, and how to predict and assess their resilience to soil erosion and degradation caused by climate change. There is a need to raise awareness, promote further discussion and carry out research, to enable remediation design that accommodates potential future conditions or is adaptable as the climate continues to change.
CIRIA has been running a climate change and contaminated land interest group for a few years, and has developed a proposal to produce a good practice guidance report on climate change risk management in contaminated land projects. For more information, please contact Joanne Kwan at CIRIA (joanne.kwan@ciria.org).
Although climate change is recognised as a concern by many in writing contaminated land reports, this is mainly qualitatively, and only a small minority carried out sensitivity analyses to assess the effects of climate change on contaminant physical chemical properties. There is currently no consistent approach to the ‘shelf’ life of either land contamination risk assessments or remediation design.
Excavation and disposal to landfill are still commonly used remediation techniques for some contaminants. There is almost no documented experience of the UK industry remediating BFRs and PFASes and relatively little experience of PCBs and mercury. This reflects the emerging nature of BFRs and PFASes as contaminants of concern and how relatively rarely PCBs and mercury are encountered on UK sites.
There is currently limited practical guidance on how to consider climate change, and what guidance there is seems to be not widely known. Advice is needed on the design, construction and long-term maintenance of cover systems, and how to predict and assess their resilience to soil erosion and degradation caused by climate change. There is a need to raise awareness, promote further discussion and carry out research, to enable remediation design that accommodates potential future conditions or is adaptable as the climate continues to change.
CIRIA has been running a climate change and contaminated land interest group for a few years, and has developed a proposal to produce a good practice guidance report on climate change risk management in contaminated land projects. For more information, please contact Joanne Kwan at CIRIA (joanne.kwan@ciria.org).
References
1. P. Nathanail, I. Ross, G. Williams, J. Nathanail, Good practice guidance for perfluoroalkyl and polyfluoroalkyl substances (PFAS) in soil and the water environment, CIRIA Report, 2022. In preparation.
2. Environment Agency, Poly- and perfluoroalkyl substance (PFAS): sources pathways and environmental data. (2021) Poly- and perfluoroalkyl substances (PFAS): sources, pathways and environmental data - report (publishing.service.gov.uk) Accessed 9th July 2022.
1. P. Nathanail, I. Ross, G. Williams, J. Nathanail, Good practice guidance for perfluoroalkyl and polyfluoroalkyl substances (PFAS) in soil and the water environment, CIRIA Report, 2022. In preparation.
2. Environment Agency, Poly- and perfluoroalkyl substance (PFAS): sources pathways and environmental data. (2021) Poly- and perfluoroalkyl substances (PFAS): sources, pathways and environmental data - report (publishing.service.gov.uk) Accessed 9th July 2022.
