The concentration dependences of the ²H spin-lattice relaxation rate in aqueous solutions of certain mineral acids were studied. The relative ¹H and ²H relaxation rates in solutions of equal compositions and concentrations were compared. Bringing the proton and deuteron resonance data into consistency was shown to require the introduction of corrections for changes in the quadrupole coupling constant of deuterons present in different solution substructures. The experimental estimates of the deuteron quadrupole coupling constants in the D₃O⁺ ions and the hydration shells of the D₃O⁺ and SO₄ ^2- ions were compared with the results of quantum-chemical calculations.