Interactions of toxic and essential trace elements with periphyton in natural waters

Some trace elements are essential to aquatic organisms, such as copper and zinc, whereas other elements mostly exert toxic effects, such as cadmium. Bioavailabillity of trace elements to freshwater benthic algal communities (periphyton) under natural water conditions is investigated to evaluate the impact of these elements to aquatic organisms. Recent projects have aimed at examining metal accumulation (copper, zinc, cadmium) in periphyton as a function of metal speciation in natural freshwaters. Experiments have been carried out in microcosms (experimental channels) and in the field in small streams. Metal speciation has been determined using DGT (diffusion gradients in thin films), by which labile metal species are measured, and equilibrium models of metal binding to natural organic matter.

During rain events, dynamic variations of metal concentrations and speciation are observed in small streams, typically with concentration increases due to resuspension of sediments and increased inputs from wastewater. Metal content in periphyton closely follows the variations of metal concentrations in the dissolved phase and may be related to the free metal ions or to labile metal species.

This project yields important information for the evaluation of water quality criteria for metals.

Experimental channels with periphyton on glass slides.

References

Meylan, S., R. Behra, and L. Sigg. 2003. Accumulation of copper and zinc in periphyton in response to dynamic variations of metal speciation in freshwater. Environ. Sci. Technol. 37: 5204-5212.

Meylan, S., R. Behra, and L. Sigg. 2004. Influence of metal speciation in natural freshwater on bioaccumulation of copper and zinc in periphyton: a microcosm study. Environ. Sci. Technol. 38: 3104-3111.

Bradac, P. 2008. Interactions of cadmium with periphyton in natural freshwaters. PhD thesis Nr. 18155. ETH Zurich.

Bradac P., Navarro E., Odzak N., Behra R., and Sigg L. (2009) Kinetics of cadmium accumulation in periphyton under freshwater conditions Environ. Toxicol. Chem. 28(10), 2108-2116.

Bradac P., Behra R., and Sigg L. (2009) Accumulation of cadmium in periphyton under various freshwater speciation conditions Environ. Sci Technol. 43, 7291-7296.

Bradac P., Wagner B., Kistler D., Traber J., Behra R., and Sigg L. (2010) Cadmium speciation and accumulation in periphyton in a small stream with dynamic concentration variations. Environ. Poll. 158, 641-648.