SYMPOSIA PAPER Published: 01 January 1997

Graphical Determination of Metal Bioavailability to Soil Invertebrates Utilizing the Langmuir Sorption Model


A new method of performing soil toxicity tests with free-living nematodes exposed to several metals and soil types has been adapted to the Langmuir sorption model in an attempt at bridging the gap between physico-chemical and biological data gathered in the complex soil matrix. Pseudo-Langmuir sorption isotherms have been developed using nematode toxic responses (lethality, in this case) in place of measured solvated metal, in order to more accurately model bioavailability. This method allows the graphical determination of Langmuir coefficients describing maximum sorption capacities and sorption affinities of various metal-soil combinations in the context of real biological responses of indigenous organisms. Results from nematode mortality tests with zinc, cadmium, copper, and lead in four soil types and water were used for isotherm construction. The level of agreement between these results and available literature data on metal sorption behavior in soils suggests that biologically relevant data may be successfully fitted to sorption models such as the Langmuir. This would allow for accurate prediction of soil contaminant concentrations which have minimal effect on indigenous invertebrates.

Author Information

Donkin, SG
Sciences International, Inc., Alexandria, VA
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Developed by Committee: E47
Pages: 28–43
DOI: 10.1520/STP12231S
ISBN-EB: 978-0-8031-5370-7
ISBN-13: 978-0-8031-2474-5