Biomonitoring of palladium in the environment using different accumulation indicators

Abstract

Palladium and its chemical compounds are primarily used by autocatalyst manufacturer, the electrical industry, dental laboratories, and the chemical and jewellery industry. Whilst the demand of most sectors remained at the same level during the last 20 years the demand of the autocatalyst sector has increased more than tenfold (Hoppstock and Sures 2004) due to the change-over from Platinum/Rhodium-converters to Palladium/Rhodiumconverters in the last decade (Helmers et al. 1998). The fact that Pd emitted by catalytic converters shows a higher water solubility and chemical mobility in the environment (Beyer et al. 1999, Claus et al. 1999) than Pt and Rh leads to the assumption that also the biological availability of this noble metal is higher. This assumption has been confirmed in a number of laboratory studies (see Zimmermann and Sures, in this book). Furthermore, the uptake of Pd by plants and animals has been demonstrated in field studies (reviewed in Ek et al. 2004a, Zimmermann and Sures 2004). Nevertheless, only very scarce information exists about the distribution of Pd in the biosphere, in particular in the fauna. For the assessment of the environmental risk of Pd we have to know the status of Pd contamination in the environment. To evaluate the exposure of natural ecosystems to Pd, environmental indicators (bioindicators) as a direct or indirect measure of environmental quality are used. Bioindicators can be used either as effect indicators or as accumulation indicators on the level of single species, populations or natural communities. Effect indicators can provide valuable information about the chemical state of their environment through changes of their physiology and/or behaviour (Sures 2004). Effect indication in its widest sense is also possible on cellular and subcellular levels. Then we talk about biomarkers which are defined as a change induced by a contaminant in the biochemical or cellular components of a process, structure or function that can be measured in a biological system" (NRC 1989). Until now, there is only little information available on effect indicators or biomarkers for platinum group metals (PGM). However, recent exposure studies with zebra mussels indicated that the induction of heat shock proteins and metallothioneins are promising parameters for effect indication (see Sures et al. in this book). In contrast to effect indication, more investigations are related to the accumulation potential of different organisms for Pd. Consequently, this chapter focuses on the use of different organisms as accumulation indicators with emphasis on animals. The ability to concentrate environmental pollutants inside their tissues makes accumulation indicators suitable for gaining information about the status and trends of environmental pollutants in the habitat investigated. The use of accumulation indicators is advantageous compared with direct analysis (e.g. in water or sediments) because only the fractions that are biologically available are taken up and concentrated by the test organism. Furthermore, accumulation indicators are able to integrate pollutants over time. Finally, the pre-concentration in sentinels enables the detection of very low concentration of pollutants in ecosystems and can facilitate the chemical analysis. In respect of Pd, this point is of high interest as the (ultra) trace analysis of Pd is still often challenging.