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Measuring available concentrations of Nanomaterials in contaminated soils
Pouran, Hamid Lofts, Steve McGrath, Steve Zhang, Hao
Pouran, Hamid
Lofts, Steve
McGrath, Steve
Zhang, Hao
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2015-10-01
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Nanoscience is facing a turning point, after years of research it has entered commercialization stage and a number of nanotechnology products are expected to enter the market. Apart from environmental impacts of emerging products there are a number of nanomaterials that are already widely used in different industries namely, ZnO, Ag and TiO2 nanoparticles. These nanomaterials could enter into the environment through different paths including the production stage, waste management and recycling or accidents. It is known that these nanomaterial have adverse environmental impacts. However, a major challenge that still exists is to better understand their fate and behaviour in the environment, which is not possible without access to proper and reliable sampling techniques. Here we present application of a modified DGT device known as Nano-DGT, which in combination with standard DGT devices could provide a reliable approach to measure available concentrations of zinc oxide, silver and titanium dioxide nanoparticles in the environment. In this research, as part of TINE (Transatlantic Initiative for Nanotechnology and the Environment) collaborations, soil samples were spiked with different concentrations of ZnO, Ag and TiO2 nanoparticles and their respective ionic forms were studied. For each soil sample a Nano- DGT, with 1000 MWCO (molecular weight cut off) dialysis membrane in the front of the diffusive gel layer, and a standard DGT device (DGT Total) were deployed in triplicates. The deployment times were approximately 18 hours. As it has been difficult to obtain accurate diffusion coefficients of those nanomaterials due to their variable nature, average mass accumulated (M) by DGT was used as a reliable measure to reveal differences between available metals in their nanoparticle and ionic forms. Among three different metals used in these studies, ZnO NP and ionic zinc seem to be the most available ones. Average concentrations of accumulated metal (M) are significantly lower for TiO2 NP and its ionic form followed by Ag NP and Ag+. This could be attributed to retention of these metallic spices by active surfaces in the soils samples (e.g. organic matter), which make them less available for DGT measurements. Interestingly the samples, even those that were spiked by ionic metals only, showed considerably higher accumulated metals for the DGT devices compared to Nano-DGT. This indicates notable fraction of freely available ions formed high molecular weight complexes in the soil.
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en
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DGTConference2015 28th September to 1st October 2015 Donostia-San Sebastian (Spain)