Initially, iso-shearing transformation was applied by xfshear in order to recover isotropic line shapes in the indirect dimension (F1). Then, individual sites were identified using the maxima of the projections of the spectra into F1 domain and slices were performed along the direct dimension (F2) to obtain 1D spectra of the quadrupolar line shape for each Al site. Finally, with the effects of the chemical shift anisotropy removed by MAS and the pure line shape separated by TQ NMR, the quadrupolar NMR parameters (δiso, CQ, η) were extracted by quadrupolar line shape simulation fitting using the central transition model. The line broadening parameter (LB) was not optimized but carefully enforced in several steps as it strongly interacts with the CQ parameter (both broaden the line shape).