Metal Ions, Element Speciation Forms Retained on Wet Chitin: Quantitative Aspects of Adsorption and Implications for Biomonitoring and Environmental Technology

Abstract

Analyses of mosses and lichens provide some information on the contents of both particulate and dissolved (from hydrometeors including snow and flooding) metal ions and other elements like As and Sb in the local environment. However, this information is compromised by rarity (and thus duly legal protection) of suitable species (particularly lichens) for regular sampling and also by poorly understood mechanisms of binding. Hence, it is crucial to find an alternative that does not harm or kill rare and/or protected organisms for sampling purposes while providing data that can be traced to environmental levels (e.g., metal ions in water) in a comprehensible way. Studying the coordination of aq. metal ions on some biogenic surface which can form ligating bonds to these ions provides such information. The most abundant and thus cheap such biopolymer acting as both a possible ligand and a water- (or environment-)biomass interface is chitin. Data from chitin exposed in either water, common sandy sediments, and ferric gels delivered by Fe-oxidizing bacteria are processed to understand adsorption in quantitative terms depending on local conditions, accounting for observed BCFs >> 1 for certain elements (Bi, V, LREEs). Slopes of functions that describe the increase of retention of some element upon increasing aq. concentrations allow us to construct (a) some function giving BCF by numerical integration, (b) predict the behavior of other elements for which certain parameters guiding complex formation are known as well. It turns out that top sensitivities (maximum BCF- or partition factor) values are reached with different elements depending on the environment the chitin sample was exposed to. PF can extend the detection and determination of many elements below levels directly observable in water or sediments. The detection of fallout radionuclides on chitin is even more sensitive (by a factor of 20–25) because of omitting dilution in workup by direct observation of γ radiation.