BEHAVIOR OF CO, FE, MN AND NI IN THE PO ESTUARY (ITALY)

The behaviour of Co, Fe, Mn, and Ni was investigated in the mixing are a of the Po fiver in six surveys over the period March 1992 to June 19 95 during low-to-medium solid load and flow conditions. The concentrat ions (nM) of dissolved elements for the riverine and marine end-member s respectively were in the ranges 0.09 to 0.93 and 0.24 to 0.98 for Co , 10 to 53 and 5 to 20 for Ni, 12 to 87 and 5 to 33 for Fe, and 10 to 155 and 26 to 105 for Mn. Co and Mn behave non-conservatively in the P o estuary: an addition to the dissolved phase occurred for these eleme nts that was more marked in the summer period. The concentrations of d issolved and particulate Ni decreased almost linearly with increase in salinity, with more marked variations in dissolved Ni concentration i n winter than summer. The concentrations of dissolved and particulate Fe also varied conservatively with salinity. This unusual behaviour fo r disserved Fe is attributed to the analytical procedure which exclude d kinetically inert colloidal species.