Distribution of arsenic species in environmental samples collected in Northern Chile

Gradient ion chromatographic separation coupled with ICP-MS was used to resolve and determine the most common arsenic species in environmental and biological samples of carrots, trout, soil, sediment and river water from Region II of Chile. The carrot and trout samples showed a concentration of 49 and 168 µg g^?1, respectively, of total As. Both concentrations are high considering the basal level. In the carrots, percentage of 45 and 31% of total As were found for As(III) and As(V) species, respectively. In the trout, the higher concentration related to AsB at 39% of the total As. As(III) and DMA were also present in relatively high concentrations. The River Loa and the soil in which the carrots are growing also present very high As(V) concentrations of 100 and 17 µg g^?1, respectively. The ratio between the concentration for the same As species found in the living organisms (carrots and trout) and the environment in which they grow (soil and water) can provide important information about the possible absorption or biotransformation of As species in living beings. As(III) and DMA are the species in which the greatest accumulation occurs with respect to the medium in which they are present, and biotransformation also appears to take place.     

Theoretical study of stratospheric relevant anions: nitrate-nitric acid complexes

The ion complexes NO3-(HNO3)n, n = 1-3, have been studied by means of ab initio calculations at the B3LYP/aug-cc-pVTZ level of theory. These systems are the most abundant anionic clusters below approximately 30 km altitude in the stratosphere and also in the upper troposphere. These complexes display short strong hydrogen bonds, which should be considered to explain their abundance in the atmosphere. Equilibrium geometries, harmonic frequencies, relative energies, and thermochemical data have been calculated for these anions for the first time. The calculations indicate small differences of energy in the variation of the two nitrate groups from planarity to an almost perpendicular form for n = 1. Planar geometries are found for n = 2 and 3 to give rise to a highly symmetric C(3h) NO3-(HNO3)3. In all the cases, binding energies close to those of covalent compounds are estimated. When experimental data are available, good correlations are found with our results.