Transfer, pathways, enrichment and discharge of trace elements in the pulp industry measured by means of neutron activation analysis

Abstract

In Norway trace elements are transferred from terrestrial ecosystems to coastal sea water via the forest industry. Raw materials (wood, bark and freshwater) contain relatively low concentrations of trace elements, but due to the high volume, processed wood and bark are the main sources of element input to the industrial pulp production process. Up to 80% of the elements enter the pulp process via wood. Thus, the annual flux of trace elements can be regarded as substantial. The purpose of this investigation is to study transfer, redistribution, enrichment and discharges of trace elements from the pulp industry. Instrumental neutron activation analysis (INAA), is used to determine the concentrations of Cd, Ce, Co, Cs, Eu, Fe, La, Rb, Sc, Sm, Sr and Zn in samples of the different raw materials, process liquors, waste and waste water and products from processing. Lead, Cu and Ni were measured by means of atomic absorption spectroscopy with graphite furnace (GFAAS) and inductive coupled plasma atomic emission spectroscopy (ICP-AES). Recycling of chemicals leads to enrichment of trace elements. Corrosion of tubes and tanks gives increased concentration of Pb, Cu and transition elements in the re-cycling circles. For all other elements the process reaches a `steady state'; hence the annual input is equal to the annual output (kg/year). The products contained very low levels of trace elements. For all the trace elements<20% of the total output from the process and for some elements only 5%, were found in the products. Discharges of trace elements from the investigated pulp production plant to the fjord reached 70% of the annual trace element output in 1993 while the remaining fraction was stored as waste.