Ion specificity in determining physico-chemical properties of drinking water

Drinking water plays a key role in regulating the daily salt intake, thus potentially affecting (either in positive or in negative direction) the incidence of diet-related pathologies, including nephrolithiasis. Being regarded as wholesome, bottled water is increasingly preferred to tap water. However, its physico-chemical characterization, as reported on the label, is usually limited to pH and conductivity measurements, along with ion content. Other parameters, which also are likely to influence the processes in which water is involved in the body, are usually neglected. In this work, the surface tension and density of tap water and two bottled mineral waters produced in Italy are investigated. These parameters are critically determined by the ion content. Density is connected to the total ion amount, while surface tension is differentially affected by the presence of specific ions: sulfate increases its value, while bicarbonate keeps it almost constant. These results furnish a reliable scientific basis for future investigation on the connection between the physico-chemical properties of drinking water and its effect on health. Particularly, since interfacial phenomena play a key role in kidney stone formation, our results suggest that dietary enrichment of selected ions due to water intake could affect nephrolithiasis.