Turbulence is one of the key processes influencing planet formation, hence we are investigating the mechanism driving it by studying its vertical structure. We have been working with the disk around DM Tau, since it is so far the only system where significant non-zero turbulence has been robustly detected in its upper layers using molecular line emission. To estimate turbulence near the midplane in the outer disk, we used N2H+(3-2) and DCO+(4-3) emission alongside a ray-tracing radiative transfer code with a parametric model of the disk structure and Bayesian statistics to find a best fit model. Our preliminary results show N2H+ emission inside the previously determined CO snowline. Moreover, the DCO+(4-3) emission is depleted between ∼ 104 and ∼ 156 au; which could be explained by CO freeze-out, non-thermal desorption and radial migration of dust grains.