  We use direct numerical simulations to compute structure functions, scaling
exponents, probability density functions and turbulent transport coefficients
of passive scalars in turbulent rotating helical and non-helical flows. We show
that helicity affects the inertial range scaling of the velocity and of the
passive scalar when rotation is present, with a spectral law consistent with
$\sim k_{\perp}^{-1.4}$ for the passive scalar variance spectrum. This scaling
law is consistent with the phenomenological argument presented in
\cite{imazio2011} for rotating non-helical flows, wich states that if energy
follows a $E(k)\sim k^{-n}$ law, then the passive scalar variance follows a law
$V(k) \sim k^{-n_{\theta}}$ with $n_{\theta}=(5-n)/2$. With the second order
scaling exponent obtained from this law, and using the Kraichnan model, we
obtain anomalous scaling exponents for the passive scalar that are in good
agreement with the numerical results. Intermittency of the passive scalar is
found to be stronger than in the non-helical rotating case, a result that is
also confirmed by stronger non-Gaussian tails in the probability density
functions of field increments. Finally, Fick's law is used to compute the
effective diffusion coefficients in the directions parallel and perpendicular
to the rotation axis. Calculations indicate that horizontal diffusion decreases
in the presence of helicity in rotating flows, while vertical diffusion
increases. We use a mean field argument to explain this behavior in terms of
the amplitude of velocity field fluctuations.
