  According to observations and numerical simulations, the Milky Way could
exhibit several spiral arm modes with multiple pattern speeds, wherein the
slower patterns are located at larger Galactocentric distances. Our aim is to
quantify the effects of the spiral arms on the azimuthal variations of the
chemical abundances for oxygen, iron and for the first time for neutron-capture
elements (europium and barium) in the Galactic disc. We assume a model based on
multiple spiral arm modes with different pattern speeds. The resulting model
represents an updated version of previous 2D chemical evolution models. We
apply new analytical prescriptions for the spiral arms in a 2D Galactic disc
chemical evolution model, exploring the possibility that the spiral structure
is formed by the overlap of chunks with different pattern speeds and spatial
extent. The predicted azimuthal variations in abundance gradients are dependent
on the considered chemical element. Elements synthesised on short time scales
(i.e., oxygen and europium in this study) exhibit larger abundance
fluctuations. In fact, for progenitors with short lifetimes, the chemical
elements restored into the ISM perfectly trace the star formation perturbed by
the passage of the spiral arms. The map of the star formation rate predicted by
our chemical evolution model with multiple patterns of spiral arms presents
arcs and arms compatible with those revealed by multiple tracers (young upper
main sequence stars, Cepheids, and distribution of stars with low radial
actions). Finally, our model predictions are in good agreement with the
azimuthal variations that emerged from the analysis of Gaia DR3 GSP-Spec [M/H]
abundance ratios, if at most recent times the pattern speeds match the Galactic
rotational curve at all radii.
