Contaminated land and extreme weather conditions
Meeting report by Rowena Fletcher-Wood (Science Oxford)
rowena.fletcherwood@gmail.com
ECG Bulletin January 2016
rowena.fletcherwood@gmail.com
ECG Bulletin January 2016
A one-day meeting on “Contaminated Land and Extreme Weather Conditions” was held in the CIRIA (Construction Industry Research and Information Association) offices in London on 29 June 2015. Attended by ca. 35 scientists and policymakers, the meeting highlighted key concerns about contaminated land that had been overlooked in the past and showed that fundamental changes must be made to industry structure and the paradigm of safety assessment.
The meeting began with a talk by the CIRIA chairman, Mike Ellis, who spoke about the urban soils of central London. He examined the difficulty found separating “soil” from “dust” and considered how the spatial distribution of contaminants varied with the nature of contaminants. For example, lead and arsenic correlate not only with urban density, but also with the natural background, determined by rock types in the area. He further mentioned a 1:1 observed correlation between bioavailability and bioaccessibility of contaminants, and queried the validity of separating these concepts. Other points included the difficulty found in assessing hazard on a reasonable time scale. For example, a New Orleans study has shown a 22-year lag between atmospheric lead pollution and its consequences upon human health and behaviour—in this example, an increased aggravated assault rate.
The meeting began with a talk by the CIRIA chairman, Mike Ellis, who spoke about the urban soils of central London. He examined the difficulty found separating “soil” from “dust” and considered how the spatial distribution of contaminants varied with the nature of contaminants. For example, lead and arsenic correlate not only with urban density, but also with the natural background, determined by rock types in the area. He further mentioned a 1:1 observed correlation between bioavailability and bioaccessibility of contaminants, and queried the validity of separating these concepts. Other points included the difficulty found in assessing hazard on a reasonable time scale. For example, a New Orleans study has shown a 22-year lag between atmospheric lead pollution and its consequences upon human health and behaviour—in this example, an increased aggravated assault rate.
Subsequent speakers discussed contaminated land in the context of sustainable development and highlighted the reasons why predicting environmental changes and minimising the detrimental effects of development are not straightforward. For example, they touched on the uncertainty in model predictions of future CO2 emissions and the different drivers for fossil fuel reduction at regional and national scales, such as local flood risk and the cost of technological changeover. Correct identification of catchments for remediation treatment requires knowledge of factors such as wind speed and direction, historical land use (e.g. mining legacy), and pH-dependent soil leaching. This highlights the intricacy of integrated risk analysis. Good sources of information include the research-policy partnership LWEC (Living with Environmental Change) (1) and the European IPPC bureau (Integrated Pollution Prevention and Control) (2).
Briony Turner (ARCC, UKCIP) and Joanne Kwan (CIRIA) highlighted the absence of contaminated land and remediation strategies in the government’s Climate Change Risk Assessment (CCRA) report (3). They called for a statutory reporting process to develop a body of data, as well as shared learning and guidance documents. With funding from the EPSRC, the UKCIP ARCC network aims to fill these gaps. For example, increasing river erosion under climate change may release more contaminants. Yet, contaminant mobility is not currently monitored in the field and is in fact very difficult to monitor, because contaminants cross river catchments and require very sensitive detection as they are diluted and dispersed. The speakers also reported on STEM workshops in schools that educate pupils about the impacts of climate change.
Oliver Lancaster (Wales & West Utilities Ltd) focussed on extreme weather, the implications of intense flooding and protection, and policy and practices involving groundwater. Lancaster expressed concern over how we assess contaminated land and classify contaminants and develop conceptual site models. Safety assessments generally include the caveat “based on current site use and land conditions,” but these sites may be subject to variation under continuing climate change and varying weather patterns. Future increases in rainfall may even invalidate safety assessments, although, Lancaster added, “Given the uncertainty, it would be a very bold consultant to suggest climate change-driven remediation measures”
Oliver Lancaster (Wales & West Utilities Ltd) focussed on extreme weather, the implications of intense flooding and protection, and policy and practices involving groundwater. Lancaster expressed concern over how we assess contaminated land and classify contaminants and develop conceptual site models. Safety assessments generally include the caveat “based on current site use and land conditions,” but these sites may be subject to variation under continuing climate change and varying weather patterns. Future increases in rainfall may even invalidate safety assessments, although, Lancaster added, “Given the uncertainty, it would be a very bold consultant to suggest climate change-driven remediation measures”
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Taking the aspect of flooding further, Chris Meakin (WorleyParsons) argued that flooding causes and exacerbates contamination. Predictions of future climate change include the possibility of an increase in extreme weather events. He cited the winter of December 2013 to February 2014 as a warning example; the wettest winter on record, it saw storms and floods throughout the country. To address and mitigate the risk of flooding contaminated land, Meakin called for a change in perception of conceptual models, such that risk assessments become flexible, living documents, rather than pre-set standards, and greater uncertainty is managed with incremental improvements as more data become available. For this to be successful, integrating knowledge and expertise across industries is vital. Potential problems with this approach include the need to risk-assess changing methods, essentially producing risk assessments of risk assessments, and the sparsity of current research and guidance. CL:AIRE (Contaminated Land: Applications in Real Environments), the Forestry Commission and CIRIA are existing bodies that are pursuing this work.
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Winter flood. Flood waters threaten the surrounding roads and housing as the Afon Teifi river bursts its banks in December 2013. Floods like this can mobilise contaminants. Credit: i4lcocl2/Shutterstock
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Stephen Kidley (Celtic Ltd.) explained that knowledge of groundwater in the UK is patchy, with research lagging years behind that on surface water. The study of groundwater is more complicated than that of surface water and cannot be simplified to two dimensions. Rock permeability plays a key role in the three-dimensional movement of water. Not only does groundwater affect the flow, temperature and volume of surface water, but also its "rebound time" for recovery after contamination. Previous estimations of hydrological behaviour have been proven erroneous. In one example, the estimated time for contaminated water to recover was 1 year, but the actual recovery time was only 6-8 weeks. It is questionable whether we can validate any predictions without greater knowledge of why this occurred. Small errors in one set of predictions can make huge differences in the premises of another, leading to disjointed models between industries and academic experts.
Trevor Howard (EA) provided the regulator’s point of view, highlighting additional outcomes of climate change on contaminated land that are worthy of consideration. Under elevated temperatures and increased rainfall, organic matter breaks down faster and may produce different degradation products; the concentration of metal toxins in plants may also vary, as may the fixation of metals in soil, which depends on soil pH and relative humidity. On the streets, tar is more likely to melt, and toxic metals such as mercury may vaporise from contaminated sources. Biotic and chemical processes will also change, but the extent to which this will occur has not yet been estimated with any confidence. Because climate change increases variability, the most variable climates – like that in the UK – remain the hardest to model.
This meeting is part of a series of events organised by CIRIA. For future CIRIA events visit: www.ciria.org/
Trevor Howard (EA) provided the regulator’s point of view, highlighting additional outcomes of climate change on contaminated land that are worthy of consideration. Under elevated temperatures and increased rainfall, organic matter breaks down faster and may produce different degradation products; the concentration of metal toxins in plants may also vary, as may the fixation of metals in soil, which depends on soil pH and relative humidity. On the streets, tar is more likely to melt, and toxic metals such as mercury may vaporise from contaminated sources. Biotic and chemical processes will also change, but the extent to which this will occur has not yet been estimated with any confidence. Because climate change increases variability, the most variable climates – like that in the UK – remain the hardest to model.
This meeting is part of a series of events organised by CIRIA. For future CIRIA events visit: www.ciria.org/
References
1. www.rcuk.ac.uk/research/xrcprogrammes/lwec
2. http://eippcb.jrc.ec.europa.eu/reference/
3. www.gov.uk/government/publications/uk-climate-change-risk-assessment-government-report
2. http://eippcb.jrc.ec.europa.eu/reference/
3. www.gov.uk/government/publications/uk-climate-change-risk-assessment-government-report
