  We formulate an extended linear $\sigma$ model of a quarkonia nonet and a
tetraquark nonet as well as a complex iso-singlet (glueball) field to study the
low-lying scalar meson. Chiral symmetry and $U_A(1)$ symmetry and their
breaking play important role to shape the scalar meson spectrum in our work.
Based on our study we will comment on what may be the mass of the lowest
possible scalar and pseudoscalar glueball states. We will also discuss on what
may be the nature of the sigma or $f_0(600)$ meson.
