The bioavailability and mobility of potentially toxic trace metals largely determine the environmental impact of metal-contaminated soils and aquatic systems. The first aim of the present work was the assessment of metals bioavailability in both soils and river waters through the comparison of the most widespread techniques used to infer metals mobility in the environment and its uptake by biota. Concerning soils, traditional techniques as leaching and extraction tests has been used in parallel to a relatively recently developed technique known as Diffusive gradients in thin films technique (DGT) capable of in situ measurement of labile metal species in natural waters, sediments and in soils. Selected leaching and extraction tests and DGT were applied to a range of metals contaminated Italian soils and their limits and field applicability were discussed. In this work, leaching tests provided an estimation of the maximum availability of metals for release from the soil matrix offering a base of reference for the chemical extractions results. pH dependence leaching curves provided also useful information to interpret DGT results, underlying the potential of parallel measurements to assess metals bioavailability. The distinguishing feature of the DGT measurement is that incorporates the kinetics of metal supply from solid phase to solution and for this reason could simulate metals uptake by plants. DGT capabilities of measuring flux of available metals from solid phase to solution has been investigated through a direct comparison with the uptake of different plant species. Our results indicated that this supply may be important for Zn uptake by wheat and lupine in well-equilibrated and amended soils. Plant Pb concentrations were highly related to both soil pore water concentrations and to the effective concentration (Ce) measured by DGT indicating that supply from the solid phase may not be so important for Pb. The present study has reported the ability of DGT to potentially predict metal phytoavailability for lupine and wheat within metals contaminated soils. The second part of the present study focused on metals bioavailability in river waters. The main aim was to compare the bioavailable fraction of metal measured by DGT and by on site filtration. In this way it was possible to investigate metal complexation and speciation focusing on the fraction of metal potentially available to aquatic organisms. In general, the two technique agreed quite well for most metals, indicating an absence of colloids and negligible complexation by organic matter. Substantial differences between DGT and on site filtration were found for Cu and Cd and were consistent with strong complexation. Metals bioaccumulation in fish was recognized to be an interesting topic of investigation in correlation with metals bioavailabilty in waters. A specific experiment was designed to study metals bioaccumulation in Ciprinus Carpio fish and a method to accurately determine metals accumulated in fish tissues was standardized. In this work, fish show bioaccumulation of Cd and Pb in their tissues under the test conditions while for Co, As and Cu other processes like excretion seem to significantly influence the net metal accumulation in fish.
Galas, C. (2008). Assesment of trace metals bioavailability in soils and river waters using different analytical techniques to predict metals uptake by biota.
|Titolo:||Assesment of trace metals bioavailability in soils and river waters using different analytical techniques to predict metals uptake by biota|
|Data di pubblicazione:||14-mag-2008|
|Anno Accademico:||A.A. 2007/2008|
|Tipologia:||Tesi di dottorato|
|Citazione:||Galas, C. (2008). Assesment of trace metals bioavailability in soils and river waters using different analytical techniques to predict metals uptake by biota.|
|Appare nelle tipologie:||07 - Tesi di dottorato|