  Interfaces between aqueous electrolytes and nanoporous carbons are involved
in a number of technological applications such as energy storage and capacitive
deionization. The disordered nature of the carbon materials makes it
challenging to characterize ion adsorption and relationships between materials
properties and performance. Nuclear magnetic spectroscopy can be very helpful
in that respect thanks to its nuclei specificity and ability to distinguish
between ions in the bulk and in pores. Nevertheless, several factors can affect
the measured chemical shifts making it difficult to interpret experimental
results. We use complementary methods, namely density functional theory
calculations, molecular dynamics simulations and a mesoscopic model, to
investigate various factors affecting the chemical shifts of aqueous
electrolyte species. We show that the relative importance of these factors
depend on the ion nature. In particular, the hydration shell has a much more
pronounced effect for large polarizable ions such as Rb$^+$ and Cs$^+$ compared
to Li$^+$.
