Fig. 3. Dependence of mass per unit area accumulated by DGT in 24 h on diffusion layer thickness. Diffusion layer thicknesses are shown that correspond to the flux deduced from Michaelis-Menten parameters for Zn accumulated by: Thlaspi arvense (shown by the dotted line) and Thlaspi caerulescens (shown by the solid line) (Lasat et al., 1996).