Changing land use

Olympic park development, Stratford, London.
  • How does land use change affect the health of the natural environment (biotic and abiotic)?
  • How do people react to these changes?
  • How does this impact on the quality of the services that it provides?

Rapidly changing human activity within the Thames basin can put huge pressures on the natural environment's ability to adapt and change. This may be further complicated by the influences of climate change, such as extremes in weather. Maintaining a balance between urban development and natural systems is essential to ensure that, for example, soils are still able to buffer potential contaminants or that ground stability is sustainable for buildings and infrastructure.

Whole-system approach

Understanding the full environmental impact of land use change requires a whole-system approach. This may reveal the potential for impacts of land use change on soils and the near surface to affect deeper and distal parts of the system, including groundwater resources and estuarine habitats, i.e. understanding source-receptor-pathway at a range of scales.

An enhanced understanding of the legacy of land use in the region has the potential to support predictions and more effective mitigation strategies relating to anthropogenic contamination.

Establishing these links offers the possibility of identifying and addressing the source of potential problems and more effectively managing those parts of the system that offer natural remediation capacity. Equally, the implications for engineered remediation of land and the restoration of natural processes should be taken into consideration.

Soils and the near sub-surface

Soils and the near sub-surface represent part of the natural environment that is susceptible to the most immediate effects of climate change. Understanding these combined stresses will allow FutureThames to contribute to predictions on the future of the services that the natural environment provides and make a direct contribution to a more sustainable culture of land use through better informed policy and planning.

More specific questions that we are helping to answer:


Where are the contaminants coming from and where are they going?

What are the emerging threats to groundwater quality?

Emerging contaminants come from newly developed compounds and/or newly categorised contaminants that have been newly discovered in groundwater due to analytical developments. For example, in the UK metaldehyde from slug pellets was detected in drinking water. Some potential emerging contaminants include pesticides, pharmaceuticals, 'lifestyle' compounds (caffeine, nicotine), personal care (DEET, parabens), industrial additives and by-products (phthalates, bisphenols), food additives, wastewater treatment by-products, flame/fire retardants, surfactants, hormones and sterols, and nanomaterials (sunscreen). The key sources of emerging contaminants in groundwater are:

  • treated waste water discharge to surface water
  • artificial recharge of treated waste water and surface water
  • those contaminants not completely removed by sewage treatment

Frequently detected groups include antibiotics, lifestyle compounds, pharmaceuticals and preservatives. Although mostly detected in low concentrations in groundwater there are many examples where high concentrations are found. There are hot spots of emerging groundwater contamination in several parts of the UK that warrant further investigation. Overall, there is poor understanding of the occurrence, transport, fate and human and ecological risk of many emerging contaminants on groundwater.

London Earth soil data has provided a valuable baseline that indicates the distribution of more than 50 inorganic elements (many classified as contaminants) across the principal urban area of the Thames basin (Greater London Authority area). This represents the biggest urban geochemical systematic survey ever carried out in the world and has provided extremely useful data for the Defra project to determine normal background concentrations of contaminants in English soil. This is part of government moves to revise and simplify the contaminated land statutory guidance.

The Olympic Park site in London was the research area for an initial screening tool (IST) that has been developed to enable planners to assess potential risks to both ground and surface water due to remobilisation of contaminants by new developments. A key new feature of this tool is the ability to track individual pollutant linkages, from a source of contamination, along multiple possible pathways to potentially susceptible receptors.

IST

The IST is a bespoke built GIS application that improves upon previous tools as it includes 3D geological data and an enhanced scoring methodology.

One major form of pollution affecting the Thames estuary is from treated, and to a lesser extent untreated, sewage. Can the analysis of sewage markers at the molecular level support water quality monitoring and help pinpoint sources of contamination?

Groundwater is the primary source of potable water in southeast England and so it is of paramount importance to protect it in urban environments. BGS has developed an initial screening tool (IST) to assist the planning community in the assessment of the potential risk to ground and surface waters from contaminants mobilised as a consequence of redevelopment. The tool has been especially designed in the context of Part IIa of the UK Environmental Protection Act (1990). The IST incorporates significant refinements to scoring methodologies and takes the prioritisation approach into the 3D environment. As a customised GIS that utilises surfaces extracted from 3D geological modelling, the tool collates and interrogates a range of geoscientific information, including:

  • contaminant scale
  • geological and historic land use
  • groundwater levels
  • hydrological domain data

The IST facilitates the ranking of various proposed development scenarios through a semi-quantitative assessment of contaminant potential via a number of pollutant linkages, providing planners with reports on the type, spatial distribution and hazards associated with potential contaminant sources within their area.

The geochemical baseline shows the anthropogenic impact on the natural geochemical baseline and can be used to inform land management to help protect and monitor environmental change (Appleton et al. In Prep (addressing reviewers comments). Geogenic signatures detectable in topsoils of urban and rural domains in the London region, UK, using parent material classified data. Applied Geochemistry).

How do anthropogenic processes impact on land and water quality?

The London Earth soil data has been the principal dataset used to define the normal background concentrations (NBCs) of English soils in the urban domain.

Humans have played a major part in changing the landscape by the deliberate movement of soil and rock for large scale and rapid urbanisation, waste disposal and mineral exploitation. Some estimate that the material moved annually by humans exceeds that transported by rivers to the oceans by a factor of almost three. This means that the global impact of humans on landscape evolution and the sedimentary cycle is significant. Evidence for this landscape transformation and anthropogenic sedimentation is commonly left behind in the geological and archaeological record, in the form of anthropogenic landforms and artificial ground. Artificial ground provides evidence for human impact and modification of the sedimentary record in the subsurface; however, it is also associated with rapid thickness changes, variable geological and geotechnical properties and contaminated land that create potential hazards to development. Artificial ground may also be considered a resource. In the UK, BGS represents artificial ground on its geological maps and increasingly in 3D geological models using a five tier classification system. This system is designed to provide a framework for the characterisation of anthropogenic landscape impact and the creation of man-made strata.

The soil geochemical survey of the Greater London area, comprising over 6400 sample sites, is the most detailed and comprehensive urban mapping project carried out to date in order to give insight into the environmental impacts of urbanisation and industrialisation, as well as to characterise the geochemical baseline of the UK's most populous city. Anthropogenic modification to soil baseline concentrations is evident across the urban area. In the cases of lead and antimony for example, high density traffic is a likely source. Despite these anthropogenic controls, a strong geological control on soil chemistry is observed for many elements. This is particularly evident in south London where high baseline concentrations of, for example calcium, caesium, iodine, lanthanum, manganese, neodymium, phosphorus, strontium, yttrium and zirconium, relate to the influence of the Cretaceous Chalk Group bedrock.

What are the impacts of urbanisation on soil chemistry and quality? How will these changes — along with increased surface sealing — reduce the soil's ability to buffer or adapt to climate change? How do the levels of change due to urbanisation observed within the Thames basin compare to other urban soil chemistry datasets in the UK?

Measurement of individual arsenic (As) species provides valuable information on the varied toxicity of inorganic and organic forms of arsenic. As(III) is considered the most toxic and mobile of As species in soil and sediment. Information regarding the chemical forms of As is useful to understand possible mobilisation from sediment into aqueous phase, since soil and sediments cannot be isolated from geochemical cycles. The aim of this work was to determine total and measureable As species in the mobilisable fraction of 36 sediment cores from the Thames estuary. The research concluded that individual sediments influence As recovery because of varying chemical and physical parameters with depth and between cores. Overall, an indication of As species present is given for a comprehensive study of River Thames sediments.

High levels of lead in central London are of particular interest for contaminated land and human health risk studies. (see Lark and Scheib, In Press. Land use and lead content in the soils of London. Geoderma (accepted for publication 12 June 2013)).

How can we model future mobility of contaminants and how will these be affected by climate change?

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