Implications of natural organic matter binding heterogeneity on understanding trace metal complexation in aquatic systems

Abstract
A comprehensive collection, critical analysis and interpretation of the data published for complexation of trace metals by natural organic matter (refractory humic-type substances and non degraded biota material) and filtered whole natural waters have been undertaken. Our interpretation framework considers the role of metal loading conditions and analytical detection windows on the complexation data in a systematic way. Its application has shown that the same patterns are observed for complexation of a range of trace metals with different types of natural organic matter: apparently stronger binding sites are utilised at lower metal ion loadings, progressively weaker sites contribute to metal complexation at higher loadings. Taking into account the detection window of the technique employed greatly improves the internal consistency of the overall data.