Thesis

Geochemical changes, plant growth and ecosystem recovery in soils after high temperature remediation

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Awarding institution
  • University of Strathclyde
Date of award
  • 2014
Thesis identifier
  • T13844
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Abstract
  • Thermal and smouldering remediation can effectively remove toxic organic compounds from contaminated sites, opening them up for re-development or environmental enrichment. However, these treatments generate elevated temperatures in the soil (40-1200°C) that may impact its quality, particularly its ability to support plant growth and microbial activity. This thesis demonstrates the effects of such heating on soil properties, the impact on plant and microbial systems, and potential methods for rehabilitating soils to improve plant growth after remediation. Soils subjected to heating underwent a number of changes including losses of organic carbon (>250°C), nitrogen (>500°C), and clay sized particles (>500°C). These changes resulted in significantly lower plant growth, microbial abundance, and microbial activity in soils heated above 500°C indicating that remediation techniques operating above this temperature will require additional soil improvement steps. In addition, soil toxicity was generated at temperature regimes of 105-250°C and >750°C in some soils. For two soils subject to smouldering remediation, organic soil conditioners (compost and anaerobic digestate) were used to improve the yield of biomass crops. In a calcium-rich topsoil, toxic conditions generated during smouldering (pH>11) were too severe and biomass crop growth could not be established. In a nutrient-poor soil, higher levels of productivity were established with compost amendment, but high levels of zinc in the anaerobic digestate proved toxic. A tipping point was identified (500°C), due to losses of nitrogen and labile carbon, above which soil conditioning will be required to facilitate biological activity. Soil conditioners can be used to improve biological activity, but interactions between soil type, remediation temperature, and soil conditioner will be significant in developing soil conditioning programmes. Thermal and smouldering remediation can mitigate toxicity of contaminated sites; however, soil conditions after remediation need to be taken into account to facilitate desired land use, including additional treatment steps when required.
Resource Type
DOI
Date Created
  • 2014
Former identifier
  • 1039451

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