Estimation of diffusive boundary layer thickness in studies involving diffusive gradients in thin films (DGT)

Recent laboratory experiments and field investigations involving diffusive gradients in thin films (DGT) have shown that the thickness (δ) of the diffusive boundary layer (DBL), which can affect the accuracy of the technique, is generally not negligible. Accordingly, the determination of δ has become a matter of considerable practical importance. Though the problem has been addressed in the recent literature, there is room for some improvement. An expression for estimation of δ is presented here, and a practical procedure for determining 6 and the concentration of DGT-labile species from sparse experimental data is proposed and illustrated by analyzing data from four experiments with DGT samplers of different diffusive gel thicknesses.