Terrestrial biotic ligand model (TBLM) for copper, and nickel toxicities to plants, invertebrates, and microbes in soils

Contamination of soils with metals is a world-wide problem that could threaten the sustainability of essential soil functions. Therefore, risk assessments utilizing appropriate and prudent soil quality criteria are needed. Although it is widely recognized that the total metal concentration in soils does not represent its bioavailability, soil quality criteria and risk assessment of metals continue to be predominantly based on the total metal concentrations. This study provides a theoretical model, the Terrestrial Biotic Ligand Model (TBLM), based on which ecotoxicities of metals in soil systems can be assessed.; For the development of the TBLM, a speciation study was conducted in up to nineteen soils spiked with different levels of Cu, and Ni in the laboratory under field moisture conditions. The soils cover nine countries in the European Union and represent seven major soil groupings. A whole soil approach with Windermere Humic Aqueous Model (WHAM VI) using the total metal concentration, the organic carbon (OC) content, the solution pH, and dissolved concentrations of major cations, as inputs was developed to predict speciation of Cu, and Ni in soil solutions of the non-calcareous soils (pH < 7 and CaCO 3 content ≅ 0%).; A comparison of the TBLM predictions to the predictions based on models employing as the dose the total metal concentration or solution free metal ion activity in the solution shows that the TBLM is consistently able to achieve a better normalization of the wide variation in toxicological results in the non-calcareous soils.; This study, which incorporates Cu, and Ni toxicities to six different endpoints associated with higher plants, invertebrates, and microbes for up to eleven non-calcareous soils of disparate properties is, to my knowledge, the first one to use a single theoretical framework for modeling metals' toxicities in terrestrial systems. Its encouraging performance in the majority of the soils considered in this study suggests that the TBLM provides a reasonable theoretical approach for insights into the competitive interaction of the cations, and assessing metal toxicities in a complex and heterogeneous soil system. Therefore, this study has achieved a significant advancement in assessing the bioavailability and toxicities of metals in terrestrial systems, which is a significant part of environmental risk assessment. (Abstract shortened by UMI.)...