硫化物及び亞硫酸塩の鯉に對する有害度に及ぼすpHの影響

抄録

By using an apparatus of the running water-type reported by one of the authors (TOMIYAMA), determinations have been made of the resistance of young carp to the solution of sodium sulfide and of sodium sulfite at different pH's in concentrations varying between 0.5 and 4mg/l and between 36 and 268mg/l, respectively. The lethal concentration of sodium sulfide has been found to be of variance to a great extent depending on pH's of the solution, namely, the critical lethal concentration being 0.55mg/l at pH 5.2, 0.95mg/l at pH 6.1, 3.3mg/l at pH 7.4, and 8.0mg/l Na₂S-S at pH 8.2. (Fig. 2).
In case of sodium sulfite, any weakness in the experimental fish has not been observed between pH 5-9 in concentration up to 268mg/i. By calculating the amount of S0₃" and HSO₃" in sulfite solution at different pH's, it has been shown that sulfite and bisulfite ion may be considered not to be poisonous below concentration of 268mg/l and 134mg/l, respectively.
The relationship between dying time and lethal concentration, of sodium sulfide conforms to Freundlich's adsorptions isotherm. Two linear lines having different slopes have been obtained in plotting logarithm of reciprocal of the dying time against logarithm of the corresponding lethal concentration of Na₂S solution (Fig. 3). Similar two linear lines have been obtained in plotting logarithm of reciprocal of the dying time against the concentration of hydrogen sulfide contained in the lethal concentrations of Na₂S solution at different pH's (Fig. 5). The slopes of the latter two lines, n, have been shown to be 0.70 and 1.6 over the concentration below and above 1mg/l, respectively. The explanation for the fact that two values for n have been obtained, can be made by supposing that the poisonous effect of hydrogen sulfide may be chronic below 1mg/l and acute above 1mg/l. The intercept of the line, k, has been found to be 0.47, irrespective of the range of concentration of hydrogen sulfide.