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Implications of pulsed chemical exposures for aquatic life criteria and wastewater permit limits

机译：脉冲化学暴露对水生生物标准和废水的影响允许限值

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Subacute effects of pulsed copper, zinc, or ammonia exposures were examined, including a range of pulse concentrations, durations, frequencies, and recovery times between pulses, using short-term chronic Pimephales promelas and 21-d Daphnia magna tests. Sublethal effects were rarely observed independent of mortality. Effects were observed only at concentrations near the species continuous exposure 48 h LC50 for each chemical. Daphnia often rebounded from temporary reproduction effects, meeting or exceeding control responses by the end of the test. Effects of 24 h ammonia or copper pulses were diminished soon after the pulse was removed, while 24 h zinc pulses caused continued effects for several days following removal of the pulse, indicating a slower uptake and/or depuration rate for zinc. D. magna exhibited less mortality as copper pulses were spaced further apart, while fish were equally or more affected with longer recovery times between copper pulses, indicative of different adaptation mechanisms between the two species. Responses were not predictable based on either average concentration or a combination of duration and concentration. Chronic water quality criteria and effluent permit limits, expressed as a 4- or 30-d average concentration, respectively, may not be appropriate for protecting against effects of pulsed exposures, depending on the frequency, magnitude, and duration of pulses, as well as the recovery period between events.
机译：使用短期慢性Pimephales promelas和21天的Daphnia magna测试，检查了脉冲铜，锌或氨暴露的亚急性效应，包括一系列脉冲浓度，持续时间，频率和脉冲之间的恢复时间。很少观察到亚致死效应与死亡率无关。对于每种化学品，仅在接近物种连续暴露48 h LC50的浓度下才观察到影响。水蚤经常从暂时的繁殖效应中反弹，到试验结束时达到或超过对照反应。去除脉冲后不久，24 h氨或铜脉冲的影响减弱，而去除脉冲后24 h的锌脉冲引起连续几天的持续影响，表明锌的吸收和/或净化速率较慢。 D. magna表现出较低的死亡率，因为铜脉冲之间的距离更远，而鱼类受到铜脉冲之间更长的恢复时间同等或更多地影响，这表明两种物种之间的适应机制不同。基于平均浓度或持续时间和浓度的组合，反应是不可预测的。分别根据4或30 d平均浓度表示的慢性水质标准和污水排放许可限值可能不适用于防止脉冲暴露的影响，具体取决于脉冲的频率，大小和持续时间，以及事件之间的恢复期。

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