  Venus clouds host a convective layer between roughly 50 and 60 km that mixes
heat, momentum, and chemical species. Observations and numerical modelling have
helped to understand the complexity of this region. However, the impact on
chemistry is still not known. Here, we use for the first time a
three-dimensional convection-resolving model with passive tracers to mimic
SO$_2$ and H$_2$O for two latitudinal cases. The tracers are relaxed towards a
vertical profile in agreement with measured values, with a timescale varying
over several orders of magnitude. The vertical mixing is quantified, it is
strong for a relaxation timescale high in front of the convective timescale,
around 4 hours. The spatial and temporal variability of the tracer due to the
convective activity is estimated, with horizontal structures of several
kilometres. At the Equator, the model is resolving a convective layer at the
cloud top (70 km) suggested by some observations, the impact of such turbulent
activity on chemical species is accounted for the first time. From the resolved
convective plumes, a vertical eddy diffusion is estimated, consistent with past
estimations from in-situ measurements, but several orders of magnitude higher
than values used in 1D chemistry modelling. The results are compared to
observations, with some spatial and temporal variability correlation,
suggesting an impact of the convective layer on the chemical species.
