natural lake water: 3.2E-8 M H+, 4.9E-7 M OH-, 1E-4 M SO42-, 1E-6 M H2PO4-, 5E-4 M H4SiO4 (in [SS80] and [SKS80] 5E-5 M), 5E-3 M HCO3-, 2E-4 M Mg2+, 1E-3 M Ca2+, 1E-8 M Pb2+; SCM \"ligand exchange model\", cited in [SKS80] and [SS80]; original reaction equation in the study: »Fe-OH + H3PO4 = »Fe-HPO4<1-> + H<1+> + H2O with logK = 7.2, formation constant in aqueous solution: PO4<3-> + 3H<1+> = H3PO4 logK = 21.702 [GFFGN03]