THE EFFECT OF WOOD SPECIES COMPOSITION ON THE TOXICITY OF SIMULATED MECHANICAL PULPING EFFLUENTS

A series of simulated mechanical pulping (SMP) effluents, prepared from wood species commonly employed in Canada, were analyzed for wood extractives and tested for acute toxicity to fathead minnows (Pimephales promelas) and acute/chronic toxicity to Ceriodaphnia affinis. The acute and chronic toxicities of the SMP effluents were found to vary substantially for the studied wood species. According to wood species, the acute lethal toxicity of the SMP effluents to both fathead minnows and Ceriodaphnia was found to follow the order white pine > balsam fir > hemlock > black spruce > aspen. The chronic effects of the various SMP effluents on Ceriodaphnia reproduction followed the order balsam fir > hemlock > white pine approximately black spruce approximately aspen. The effluent prepared from balsam fir exhibited the lowest chronic toxicity threshold, affecting Ceriodaphnia reproduction at concentrations as low as 0.005%. The compound primarily responsible for this effect was identified as dehydrojuvabione, a naturally occurring sesquiterpenoid ester known to be present in balsam fir. Dehydrojuvabione was found to affect Ceriodaphnia reproduction adversely at concentrations as low as 0.5-mu-g/L.