Understanding scalar transport in turbulent boundary layer flows involving mass flux injection forms an essential part in the analysis of various technical applications and physical phenomena, such as flame retardants influencing a flame boundary layer's development, ocean-driven melting of ice shelves, or film cooling of turbine blades. In the present work we aim to quantify the transport of passive scalars from a surface into a turbulent flow field with and without a mass injection through this surface. For this purpose we perform direct numerical simulations of a spatially developing zero-pressure-gradient turbulent boundary layer over a flat plate. The plate surface contains a heated section such that a heat flux into the turbulent boundary layer is generated. In a second step, this heated section is made porous and a small mass flux through the surface actively carries heated fluid into the boundary layer. The wall-normal blowing velocity of this “active” wall section is set to 0.5% of the free-stream velocity. The two cases, i.e. with and without mass flux through the heated surface sections, are compared for two configurations that differ in terms of the length of the heated surface section. The long heated section is four times longer than its short counterpart. First results show that for the cases with the shorter heated section, blowing enhances the total mean specific scalar flux by approximately a factor of 2.0. For cases with a longer heated section, a factor of 2.3 is observed. After the heated section, over which an internal thermal boundary layer starts growing, the mean temperature distribution resembles profiles known for the velocity distribution in wall-jets. Future work will focus on the analysis of moments of second order. Through the present work, a dataset for turbulent boundary layers involving scalar transfer is generated, which, for example, can support the development and validation of turbulence models.