  The drift wave in the presence of impurity ions was investigated numerically
in reversed field pinch (RFP) plasmas, using the gyrokinetic integral eigenmode
equation. It was found that in RFP plasmas with hollow density profiles, an
increase in $k_\theta \rho_s$ increases the growth rate of the ion temperature
gradient (ITG). Comparing the results of regular and hollow plasma density
profile shows that the ITG mode under the hollow density profile is much harder
to be excited. For the impurities' effects, when the impurities' density
gradient is opposite to the primary ions, namely when $L_{ez}$ is negative,
impurities could enhance the instability. On the contrary, when $L_{ez}$ is
positive, the instability is stabilized. Regarding the trapped electron mode
(TEMs), the growth rate under the plasma with hollow density profile remained
minor than that for the standard density gradient. There exists a threshold of
$L_{ez}$. When $L_{ez}$ is less than this value, impurity destabilizes TEMs,
while as $L_{ez}$ is greater than this, impurity stabilizes TEMs. The effects
of $L_{ez}$ on TEM also depend on both the plasma density gradient and the
impurity species. In addition, the influence of collisionality on TEMs was also
studied.
