Fig. 2. Conceptual graph showing the mechanism by which plant transpiration concentrates conservative dissolved species. For a thin layer of sediment with transpiration rate of Q_{transpiration} and inflow rate Q_inflow with concentration of C_inflow, the outflow rate Q_outflow = Q_inflow – Q_{transpiration}, and its concentration in the outflow C_outflow = (Q_inflowC_inflow)/(Q_outflow) > C_inflow. With the known drainage rate and the vertical concentration profile of a conservative species, the transpiration and inflow rates for a specific layer can be estimated: Q_{N – 1} = C_NQ_N/C_{N – 1}; Q_{N – 1}^t = Q_{N – 1} – Q_N; Q_{i – 1} = C_iQ_i/C_{i – 1}; Q_{i – 1}^t = Q_{i – 1} – Q_i. Here N represents total number of layers, while i is the sequential number of one specific layer; i = 0 for the sediment right beneath the water–sediment interface; Q_{N – 1} is the inflow rate of layer N – 1, Q_{N – 1} is the outflow rate of layer N – 1, and Q_{N – 1}^t represents the transpiration rate in layer N – 1.