<image>Quadrilateral ABCD is a right trapezoid, AB ∥ CD, AB ⊥ BC, and BC = CD = 2, AB = 3. When the trapezoid ABCD is respectively rotated around the lines AB and CD for one full turn, the surface areas of the resulting geometric solids are S_{1} and S_{2}, respectively. Then, |S_{1} - S_{2}| = _____ (square units) 