In this work, the studies describing the use of attenuated total reflection -infrared spectroscopy to obtain information on the sorption mechanism of inorganic ions on metal oxy-hydroxides are reviewed. ATR-IR is amongst the rare techniques which allow to analyze the sorption phenomena in situ and led to several results about the speciation of sorbed anions (sulfate, carbonate, phosphate, perchlorate, ...) or ternary inorganic complexes since it is able to distinguish outer-sphere and inner-sphere complexes. The principles of this method are summarized, and the experimental protocols, the results and the limitations are detailed. The sample deposition method, initially based a paste or a concentrated suspension, have evolved towards the coating of the ATR crystal by a colloid layer, increasing the sensibility and the reproducibility of the measurements. Observed absorption frequencies of ions sorbed on metal oxy-hydroxides (goethite, hematite, alumina, silica, TiO 2 , ...) are reported to help the identification of peaks in new experimental works. This method, characterized by an in situ analysis performed with a special cell used in a widespread instrumentation (IR spectrometer), is very recent but its advantages suitable for the current problems in the sorption field should help its rapid development for the next years.

The stability of γ-alumina suspensions in water has been investigated by long-duration experiments (1 day to 6 months). Several complementary methods were used to characterize the solid (acid-base titration and dissolution rate measurements, X-ray photoelectron spectroscopy, X-ray diffraction, gravimetric/ differential thermal analysis, infrared spectroscopy, and scanning electron microscopy). It appears that γ-alumina, which is widely used as a model oxide in sorption experiments, thanks mainly to its high specific surface area and to the presence of aluminol groups on its surface, is progressively transformed to bayerite (β-Al(OH)3). This transformation was characterized by an induction period of about 4 days, corresponding to the formation of a transient amorphous hydrated phase, followed by an increase in the bayerite concentration, which levels off after about 2 months. This transformation results in a dramatic decrease in the surface density of sites reactive to protons. Thermodynamical calculations predict the hydration reaction of γ-alumina leading to a more stable phase (bayerite, gibbsite, or boehmite). Since the surface reactivity and sorption properties of solids are factors controlling the transport of elements in water, it is necessary to take into account the stability of solids when modeling sorption experiments. These factors are important for the long-term prediction of the effectiveness of barriers placed around radioactive waste depositories.

The review examines literature relevant to environmental fate, transformation, and toxicity, and human exposure and health risks of neonicotinoid insecticides.