Results obtained for decreasing pore size systematically reveal lower values of T 1 in the case of Na 2 SO 4 solid surfaces, as compared with NaCl (insert in Fig. ). Moreover, for both NaCl and Na 2 SO 4 slit pores, 1/T 1 decreases for decreasing pore size h, as is expected from the increase in surface-to-volume ratio (Eq. ( )). For both salts, the scaling of 1/T 1 with the pore size h is in between 1/h (surface-limited regime) and 1/h 2 (diffusion-limited regime) . For the smallest pore size considered here (h ≈ 0.3-0.4 nm), for which the water film has a thickness similar to a single molecular layer, T 1 is about one order of magnitude larger than in bulk in the case of NaCl, and about 2 orders of magnitudes larger than in bulk in the case of Na 2 SO 4 . For such narrow pores, the value of T 1 is likely affected by the exotic effects displayed by fluids confined within sub-nanometer pores that can be linked to the breakdown of the continuum Navier-Stokes formulation . Similar trends have been reported from previous MD studies. of Lennard-Jones liquids confined in slit pores , and Mutisya et al. showed a decrease in the spin-spin relaxation time T 2 as the pore size decreases for water confined in calcite pores .