Environmental Geology

, Volume 57, Issue 1, pp 91–98 | Cite as

Controlling factors and environmental implications of mercury contamination in urban and agricultural soils under a long-term influence of a chlor-alkali plant in the North–West Portugal

  • A. Cachada
  • S. M. Rodrigues
  • C. Mieiro
  • E. Ferreira da Silva
  • E. Pereira
  • A. C. Duarte
Original Article


This study aims at assessing the extent of total mercury (Hg) contamination in urban and agricultural soils under long-term influence of a chlor-alkali plant, located at about 1 km away from a town centre. Moreover, it aims at identifying the main factors controlling Hg contents’ distribution and associated potential hazards to environment and human health. The median value of total Hg for soil surface layer (0–10 cm) was 0.20 mg/kg (data ranging from 0.050 to 4.5 mg/kg) and for subsurface layer (10–20 cm) 0.18 mg/kg (data ranging from 0.046 to 3.0 mg/kg). The agricultural area showed higher Hg concentrations (ranging from 0.86 to 4.5 mg/kg) than urban area (ranging from 0.05 to 0.61 mg/kg), with some results exceeding target values set by the Dutch guidelines. Mercury concentrations observed in the studied area are more likely to be associated with the influence of the chlor-alkali plant and with the use of historically contaminated sludges and water from a nearby lagoon in agriculture, than to the impacts of urban development. The statistical correlations between Hg concentrations and soil properties suggest that anthropogenic metal sources should influence the spatial distribution more than the geological properties. Although the Hg emissions were drastically reduced 10 years ago, the area under influence of the chlor-alkali plant is still facing potential health and environmental threats arising from soil contamination.


Mercury Urban soils Agricultural soils Chlor-alkali plant 



This work was part of the Portuguese project POCTI/CTA/44851/2002: SOLURB (“Towards a methodology for the assessment of environmental quality in urban soils”) funded by the Portuguese Foundation for Science and Technology (FCT).


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • A. Cachada
    • 1
  • S. M. Rodrigues
    • 1
  • C. Mieiro
    • 1
  • E. Ferreira da Silva
    • 2
  • E. Pereira
    • 1
  • A. C. Duarte
    • 1
  1. 1.CESAM and Department of ChemistryUniversity of AveiroAveiroPortugal
  2. 2.ELMAS, Department of GeosciencesUniversity of AveiroAveiroPortugal

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