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| Author(s): |
Adnívia Santos Costa Monteiro
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Araraquara. 2017-05-03. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara |
| Defense date: | 2017-04-07 |
| Advisor: | André Henrique Rosa; José Paulo Soares Pinheiro |
| Abstract | |
The study of speciation in natural waters are crucial to understand the behaviour and fate of metal ions in the environment, since these elements can be found in different chemical forms (complexed or free). The mobility, bioavailability and transport of these ions can be influenced by natural organic matter (NOM) and aquatic humic substances (AHS), which are the main ligands in aquatic environments. The objective of this thesis was to develop electroanalytical methods using the techniques stripping chronopotenciometry (SCP) and absence of gradients and nernstian stripping (AGNES), which are able to determine the concentration of total (TCd) and free (FCd) cadmium directly in water samples from the rivers Itapanhaú (RI) and Sorocabinha (RS), located in the state of São Paulo. It would make possible a future on-site measurement applications. This study also aimed to evaluate the influence of NOM and AHS extracted from these rivers in the interactions with Cd(II) and Pb(II). Water samples were taken in march and november/2014 in order to investigate the effect of seasonality. These samples were characterised using water quality parameters, dissolved organic carbon (DOC), UV/VIS spectroscopy and concentrations of total, dissolved and free metal (ultrafiltered through 1 kDa membrane with tangential flow- TUF). AHS and their fractions (humic, HA, and fluvic acid, FA) were characterised by elemental analysis, NMR 13C. They were fractionated through TUF through membranes 100, 30, 10, 3 and 1 kDa. The methods developed of SCP (TCd determination) and AGNES (CdL determination) applied in the in natura and ultrafiltered (1 kDa) samples were validated using graphite furnace atomic absorption spectrometry (GFAAS). The results showed that the main differences between the waters from RI and RS are related probably to the influence of seawater and seasonality. The structural composition of AHS and FA presented higher content of aliphatic compounds. The distribution of DOC after size fractionation showed that the predominant fractions in the AHS and FA were between 10 and 1 kDa. On the other hand, 50% of the material was higher than 100 kDa in the HA. The results of SCP (LoD: 1.6x10-9 mol L-1) and AGNES (LoD: 1.9x10-9 mol L-1) revealed their potential in quantification of total and free Cd(II), respectively, in the samples analysed. The study of interactions of Cd(II) and Pb(II) with FA and HA showed that both materials from RI and RS presented higher complexation with Pb(II). The complexation increases with the pH for both materials. (AU) | |
| FAPESP's process: | 13/14122-0 - SPECIATION DYNAMICS OF TRACE METALS (Cd and Pb) IN AQUATIC SYSTEMS: EXPERIMENTS IN LABORATORY AND "ON-SITE" |
| Grantee: | Adnivia Santos Costa Monteiro |
| Support Opportunities: | Scholarships in Brazil - Doctorate |