Speciation of trace elements in discharges from the pulp industry

The concentrations and size distribution pattern of trace elements in wastewater discharged from a pulp industry located at Oslo Fjord, Norway, have been studied. The annual discharge to the fjord amounts to approx. 34 kg Cd, 18 kg Ce, 15 kg Co, 10 kg Cs, 1500 kg Cu, 8200 kg Fe, 150 kg Ni, 420 kg Pb, 1100 kg Rb, 1.2 kg Sc, 3 kg Sm, 5100 kg Sr and 3500 kg Zn. Information on the size-distribution pattern of the trace elements in discharged waste water was obtained using the tangential cross-flow ultrafiltration technique. Instrumental neutron activation analysis, INAA, was employed to determine the concentration levels of Cd, Ce, Co, Cs, Eu, Fe, La, Rb, Sc, Sm, Sr and Zn. Lead, Cu and Ni were measured by atomic absorption spectroscopy with graphite furnace, GFAAS, and inductively coupled plasma atomic emission spectroscopy, ICP-AES. Almost all of the alkali metals Cs and Rb, the alkaline earth metal Sr and also Ni in discharged waste water were found to be present in the low molecular weight fraction. A major fraction of Co, Cu and Pb was present in the low molecular weight fraction, while a significant fraction was found as colloids, particles or both. Cadmium, Fe and Zn in discharge waste water were predominantly present as colloids. Approx. 50% of Sc was present as particles, 100% of Ce was present as particles, and most of the Sm was found as colloids. Due to coastal currents and trace element background levels in coastal water, the contribution of mobile trace elements to Norwegian coastal sea water is probably of minor importance provided that wood from highly contaminated areas is not utilised in the pulp industry. If the particle fraction accumulates outside the outlet, however, a local environmental impact over the years should be expected.