Metal Binding Properties of Leaf Litter Extracts: II. A Bioassay Technique

Abstract

AbstractA biological method is proposed to determine the maximum Cu binding ability and the conditional stability constant of leaf litter extracts. Free cupric ions reduce the 14CO2‐uptake of algae. In the presence of complex forming organic substances the observed depression of the relative CO2 uptake can be considered as a measure of the unbound ionic Cu concentration. Comparing the CO2‐uptake response function of solutions, with and without organic constituents spiked with variable amounts of Cu, yields a functional relationship between bound and free Cu. These functions can be interpreted with a sequential form of the Langmuir equation from which the maximum binding ability and the conditional stability constant are obtained. The presence of algae, modifies the complexing parameters, indicating that the values measured with nonbiological methods require careful interpretation when their significance in natural soils is considered.