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Section 4: Pollutant behaviour on field sites |
1 Department of Environmental Science and Engineering, Technical University of Denmark, Denmark
2 Department of Environmental and Civil Engineering, University of Bradford, Bradford, U.K.
3 AB Jacobson & Widmark, Water and Environment, Lidingö, Sweden
The Rexco coal carbonization plant near Mansfield in the UK East Midlands produced coke by the process known as ‘Rexco’ in the 1950s to early 1960s. In the process gas and coal-tar were also produced. The gas was cooled with water whereby ammonia and coal-tar in the gas were dissolved/condensed. Ammonia liquor and coal-tar are known to have leaked into the subsurface from cracked tanks at the site. Based on this, a large plume of ammonium and coal-tar compounds was expected to be present in the aquifer. Effluent compositions have been determined, and an extensive reconnaissance study of the groundwater contamination in the sandstone aquifer has been carried out. The coal-tar contained phenols, naphthalenes and BTEXs, and low levels of PAHs. The ammonia liquor contained very high concentrations of phenols and ammonium. Extensive contamination with ammonium has been encountered, indicating the ammonia liquor as the primary source of contamination. No significant contamination with specific organic coal-tar compounds is present today in spite of the extensive leaks of coal-tar and ammonia liquor in the past. The organic coal-tar compounds released with the ammonia liquor have likely been degraded/transformed in the saturated part of the aquifer as well as in the vadose zone.
