Comparing the spectra T 1 (ν) over the entire frequency range for both bulk solutions and slit pores, and for 2 different salt concentrations (c s = 0 and 3 mol/kg), two clear effects of the salt can be noted. First, at high frequencies, where molecular motions dominate, an increase of c s leads to systematically lower values of T 1 as expected for the increased bulk viscosity (area II in Fig. ). This effect is observed both for slit nanopores and bulk systems. Second, at lower frequencies, T 1 (ν) shows clear variations with ν only in the case of a slit pore with c s > 0, and is flat otherwise (area I in Fig. ). This low frequency regime resembles the observation previously made also for Na 2 SO 4 slit pores with c s = 0 (Fig. ), as well as results obtained for Na 2 SO 4 slit pores with c s > 0 (Fig. ) and will discussed in more depth in the discussion section.