R7 AM Soil Ecotoxicology and Risk Assessment
Thursday, 17 November 2005: 8:00 AM - 11:40 AM in 327-329

(ALL-1117-734858) Development of Terrestrial Biotic Ligand Models for Copper and Nickel Toxicity in Soils: Application for Plant, Invertebrate, and Microbial Tests.

Thakali, S¹, Allen, H¹, Di Toro, D.¹, Ponizovsky, A¹, Rooney, C², Zhao, F², McGrath, S², Criel, P³, Janssen, C³, Oorts, K⁴, Smolders, E.⁴, ¹ Center for the Study of Metals in the Environment, University of Delaware, Newark, DE, USA² Agriculture and Environment Division, Rothamsted Research, Harpenden, Hertfordshire, UK³ Ghent University, Laboratory of Environmental Toxicology and Aquatic Ecology, Ghent, Belgium⁴ Laboratory for Soil and Water Management, K.U.Leuven, Faculty of Agricultural and Applied Biological Sciences, Leuven, Belgium

ABSTRACT- Terrestrial Biotic Ligand Models (TBLM) were developed based on data for Cu and Ni speciation and bioassays carried out on non-calcareous soils (11 for Cu and 10 for Ni) of the European Union. Metal activity was calculated using the WHAM VI model with total (added + background) Cu or Ni, soil organic matter, pH and soil solution concentrations of alkali and alkaline earth metals as inputs. The TBLM approach considers Cu²⁺ or Ni²⁺ in soil solution to be in equilibrium with metal in the soil. The metal ions react with the biotic ligand, the receptor site for the organism. Other ions, principally H⁺, Ca²⁺ and Mg²⁺, compete with the Cu²⁺ or Ni²⁺ to ameliorate their toxicity. The same extent of biological effect is exerted for a specific bioassay test endpoint and metal at the same fraction of biotic ligand sites occupied by the Cu or Ni, irrespective of the soil chemistry. A comparison of the TBLM approach to that of considering total metal or free metal ion activity indicates that the TBLM provides an appropriate means to normalize and compare toxicological results among soils.

Key words: terrestrial biotic ligand model, copper, nickel, soil