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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 Qtranspiration and inflow rate Qinflow with concentration of Cinflow, the outflow rate Qoutflow = Qinflow – Qtranspiration, and its concentration in the outflow Coutflow = (QinflowCinflow)/(Qoutflow) > Cinflow. 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: QN – 1 = CNQN/CN – 1; QN – 1t = QN – 1 – QN; Qi – 1 = CiQi/Ci – 1; Qi – 1t = Qi – 1 – Qi. 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; QN – 1 is the inflow rate of layer N – 1, QN – 1 is the outflow rate of layer N – 1, and QN – 1t represents the transpiration rate in layer N – 1.
