Liquid densities, heat capacities, refractive index and excess quantities for {protic ionic liquids plus water} binary system

Densities, rho, of aqueous solutions of the room temperature protic ionic liquid (PIL), pyrrolidinium nitrate are determined at the atmospheric pressure over the temperature range from (283.15 to 323.15) K and within the whole composition range. The molar isobaric heat capacities, C(p), and refractive index, n(D), of {PIL + water} binary system are measured at 298.15 K. The excess molar volumes V(E), excess molar isobaric heat capacities C(p)(E), and deviation from ideality of refractive index Delta(phi)n, of pyrrolidinium nitrate aqueous solutions were deduced from the experimental results as well as apparent molar volumes V(phi), partial molar volumes (V) over bar (m,i), and thermal expansion coefficients alpha(p). The V(E) values were found to be positive over the entire composition range at all temperatures studied therein, whereas deviations from ideality were negative for refractive index Delta(phi)n. The volumetric properties of binary mixtures containing water and four other protic ionic liquids, such as pyrrolidinium hydrogen sulfate, pyrrolidinium formiate, collidinium formate, and diisopropyl-ethylammonium formate were also determined at 298.15 K. Results have been then discussed in terms of molecular interactions and molecular structures in these binary mixtures. (C) 2009 Elsevier Ltd. All rights reserved.

Evaluation of effective groundwater recharge of freshwater lens in small islands by the combined modeling of geoelectrical data and water heads

In small islands, a freshwater lens can develop due to the recharge induced by rain. Magnitude and spatial distribution of this recharge control the elevation of freshwater and the depth of its interface with salt water. Therefore, the study of lens morphology gives useful information on both the recharge and water uptake due to evapotranspiration by vegetation. Electrical resistivity tomography was applied on a small coral reef island, giving relevant information on the lens structure. Variable density groundwater flow models were then applied to simulate freshwater behavior. Cross validation of the geoelectrical model and the groundwater model showed that recharge exceeds water uptake in dunes with little vegetation, allowing the lens to develop. Conversely, in the low-lying and densely vegetated sectors, where water uptake exceeds recharge, the lens cannot develop and seawater intrusion occurs. This combined modeling method constitutes an original approach to evaluate effective groundwater recharge in such environments.
[Comte, J.-C., O. Banton, J.-L. Join, and G. Cabioch (2010), Evaluation of effective groundwater recharge of freshwater lens in small islands by the combined modeling of geoelectrical data and water heads, Water Resour. Res., 46, W06601, doi:10.1029/2009WR008058.]