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Marine bivalves (Mytilus galloprovincialis) were exposed to titanium dioxide (10 mg L(-1)) either as engineered nanoparticles (nTiO2; fresh, or aged under simulated sunlight for 7 days) or the bulk equivalent. Inductively coupled plasma-optical emission spectrometry analyses of mussel tissues showed higher Ti accumulation (>10-fold) in the digestive gland compared to gills. Nano-sized TiO2 showed greater accumulation than bulk, irrespective of ageing, particularly in digestive gland (>sixfold higher). Despite this, transcriptional expression of metallothionein genes, histology and histochemical analysis suggested that the bulk material was more toxic. Haemocytes showed significantly enhanced DNA damage, determined by the modified comet assay, for all treatments compared to the control, but no significant differences between the treatments. Our integrated study suggests that for this ecologically relevant organism photocatalytic ageing of nTiO2 does not significantly alter toxicity, and that bulk TiO2 may be less ecotoxicologically inert than previously assumed.

This review discusses and compares the methods given for the determination of rare earth elements (REE) in natural water samples, including sea, river, lake, tap, ground and waste waters as well as Antarctic ice. Since REE are at very low concentrations in natural waters, numerous different preconcentration methods have been proposed to enable their measurement. These include liquid liquid extraction, dispersive liquid-liquid micro-extraction and solidified floating drop micro-extraction. In addition to liquid-liquid extraction methods, solid phase extraction using commercial resins, resins made in-house, silica-based exchange materials and other solid media is also discussed. These and other techniques such as precipitation/co-precipitation and flotation are compared in terms of speed, preconcentration factors achieved, precision, accuracy and limits of detection (LOD). Some papers have discussed the direct determination of REE in these sample types. Some have used specialised sample introduction systems such as ultrasonic nebulization whereas others have used a standard sample introduction system coupled with inductively coupled plasma mass spectrometry (ICP-MS) detection. These direct methods have also been discussed and compared.

The uptake of platinum group elements (PGE) by different preparations of estuarine sediment suspended in filtered river water has been examined. For a given PGE, adsorption time courses to untreated sediment and to sediment whose hydrous metal oxides or organic matter had been removed by appropriate chemical treatments were similar. Adsorption of Rh(lll) and Pt(IV) proceeded via a first-order reversible reaction. For Rh, forward rate constants were 1 order of magnitude greater than reverse rate constants, but for Pt, forward and reverse constants were comparable. Respective system response times, required to attain 63% of the new equilibrium, ranged from about 10 to 30 h and 2 to 20 h. In contrast, rapid, initial uptake of Pd(ll) was succeeded, in most instances, by a protracted period of desorption, requiring a more complex mechanistic interpretation. In all cases, adsorption was reduced following a period of PGE equilibration with filtered river water, suggesting that complexation with natural organic ligands exerts a significant control on the adsorption process by, for example, stabilizing PGE in solution. Exchangeability of adsorbed PGE, evaluated by ammonium acetate extraction, decreased in the order Pd > Pt > Rh, in qualitative agreement with the proposed or modeled adsorption mechanisms. Experimental results, together with independent assessments of PGE mobility from secondary sources (e.g. road dust), indicate that Pd has the greatest potential for long-range transport and bioaccumulation in the aquatic environment.

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