Arsenic Transfer from As-Rich Sediments to River Water in the Presence of Biofilms

Figure 4

Global balance of As in systems C and B. Blue arrows indicate As extractable with 0.05 M (NH₄)₂SO₄, while red arrows show the As extractable with 0.05 M NH₄H₂PO₄. For the calculation of this balance, the following parameters have been employed: the density of the sediment (1.5 g cm⁻³), the area occupied by sediment (55.9 cm²), the depth of sediment (1.5 cm), the mass of sediment (125 g), the sediment-water content (0.2 kg H₂O/kg wet solid), the depth of the layer of biofilm-enriched sediment (0.3 cm), together with the total As content in sediments, the As concentrations detected in the overlying waters at the end of the experiment, and the As mobilized by 0.05 M (NH₄)₂SO₄ and 0.05 M NH₄H₂PO₄.