Chemical constituents in effluent from the caustic extraction stage of the bleach plant at a western Canada kraft pulpmill were fractionated to identify factors responsible for their toxicity to juvenile rainbow trout (Salmo gairdneri). At all stages in the fractionation procedure bioassays were carried out to monitor toxicities of the isolated materials. Five toxic compounds, separated in a pure state from the effluent, were characterized by chromatography, spectroscopy, and chemical synthesis. The compounds and their 96-h median lethal concentrations (LC50) measured in static bioassays were: 3,4,5-trichloroguaiacol (0.75 mg/liter), 3,4,5,6-tetrachloroguaiacol (0.32 mg/liter), monochlorodehydroabietic acid (0.6 mg/liter), dichlorodehydroabietic acid (0.6 mg/liter), 9,10-epoxystearic acid (1.5 mg/liter).The same compounds were shown to be present in caustic extraction effluents collected from six other western kraft mills. For two samples, the concentration–toxicity graphs from bioassays of solutions containing only the pure toxicants in the amounts found by analysis were similar to those of the actual effluents produced by the mills. Concentrations of the toxic constituents in samples from six different mills were equivalent to 2.3–24 TU (toxic units), confirming that they are important factors in the toxicity of caustic extraction effluents.

No abstract

Easier method for recalling the filling order of orbitals.

Median lethal concentrations (LC50) of four insect juvenile hormone analogues (IJHA) for juvenile rainbow trout (Salmo gairdneri) were measured in bioassays with 4-h solution renewal. The most toxic compound tested was Δ4′-dehydrojuvabione, with a 48-h LC50 of 1.4 mg/liter and an estimated 96-h LC50 of approximately 0.8 mg/liter. Juvabione, epimeric mixtures of dihydrojuvabiones, and epimeric mixtures of juvabiols had 96-h LC50’s of 1.5, 1.8, and 2.0 mg/liter, respectively. All fish, including those that survived for 96 h, became lethargic soon after exposure to solutions of the IJHA, and their skins darkened. The toxicants were unstable in aqueous solution.

No abstract