The reduction of Cr(VI) by humic substances from leonardite and peat was investigated by capillary zone electrophoresis at various pHs. Both humic materials reduced Cr(VI) at pH 5.4, but not at basic pH. The capacity of leonardite humic substances to reduce Cr(VI) was lower than that of peat humic substances. Fe(III) accelerated the reduction of Cr(VI) by peat humic substances, but not by leonardite humic substances. Cr(VI) reduction mechanisms are proposed. The coal humic substances seem more suitable for remediation of Cr(VI)-contaminated sites.

Abstract:A new concept for the mediating action of humic substances (HS) in the contaminated environment is developed. It defines three scenarios of mitigating activity of HS in the system "living cell-ecotoxicant". The first scenario refers to deactivation of ecotoxicants (ET) by HS due to formation of non-toxic and non-bioavailable complexes. It takes place outside of the cell and is defined as "exterior effects". The second scenario refers to deactivation of ET due to HS adsorption onto the cell wall or membrane and is defined as "boundary effects": sorption takes place on the cell surface and implies changes in permeability and structure of the cell membrane. The third scenario refers to amelioration of contaminant toxicity due to activation of systemic resistance to chemical stress. This implies HS participation in immune response activation and is defined as "interior" effects. Viability of this concept was confirmed by the results of detoxification experiments. It was shown that chemical binding ("exterior effects") played a key role in ameliorating toxicity of ecotoxicants (Hg(II) and PAHs) strongly interacting with HS, whereas enhanced immune response ("boundary and interior" effects) was much more operative for a decrease in toxicity of atrazine weakly interacting with HS. The formulated concept provided satisfactory explanations for a vast pool of reported findings of mitigating activity of HS reviewed in the chapter. Few cases of amplified toxicity reported for weakly interacting contaminants in the presence of low molecular weight HS were related to facilitated penetration and follow up dissociation of humiccontaminant complexes in the cell interior. It is concluded that the developed concept can be used as a prospective tool for both predictive modelling of 249I. Twardowska et al. (eds.), and Water Pollution Monitoring, Protection and Remediation, 3-23.

Nano- and microgels are promising soft polymer materials for different application fields: stabilizers, sensors, catalysts, selective sorbents, drug delivery carriers etc. They are composed of cross-linked polymer chains swollen with a solvent. The building blocks, synthesis approaches and architecture of nano- and microgels are reviewed. The mechanisms of responsiveness to various stimuli are described, examples of applications are provided. Micro- and nanogels are good objects for learning projects and the ideas for learning projects with microgels are described.

A large syringe can be used as a vacuum source in vacuum filtration.