Centre for Environmental Contaminants Research, CSIRO Land and Water Locked Bag 2007, Kirrawee, NSW 2232, Australia.
Centre for Medical and Molecular Biosciences, School of Chemistry, University of Wollongong, Australia.
Environ Pollut. 2018 Jul;238:607-616. doi: 10.1016/j.envpol.2018.03.095. Epub 2018 Mar 31.
Intermittent, fluctuating and pulsed contaminant discharges may result in organisms receiving highly variable toxicant exposures. This study investigated the toxicity of continuous and pulsed exposures of a complex, neutralised drainage water (NDW) and dissolved copper-spiked dilute NDW to the green alga, Pseudokirchneriella subcapitata. The effects of single pulses of between 1 and 48 h duration and continuous exposures (72 h) on algal growth rate inhibition were compared on a time-averaged concentration (TAC) basis. Algal growth rates generally recovered to control levels within 24-48 h of the pulse removal. Continuous exposures to NDW resulted in similar or marginally higher toxicity to the algae when compared to pulsed exposures of equivalent TAC (% NDW). The toxicity of the NDW was attributed mostly to the metals, with the major cations potentially causing effects that are both additive (direct toxicity) and antagonistic (lower bioavailability of trace metals). For dissolved copper in dilute NDW, the pulsed exposures caused slightly higher toxicity than continuous exposures of equivalent dissolved copper TAC, with much of the difference explained by differences in labile copper concentrations between treatments. The results indicate that water quality guideline values for toxicants derived from continuous chronic exposures may be relaxed for pulsed exposures by a factor related to the TAC with the intent to provide an adequately protective but not overly-conservative outcome. The study highlights the influence that natural water quality parameters such as water hardness and DOC can have metal speciation and toxicity, and indicates that these parameters are particularly important for site-specific water quality guideline value derivation where, on a TAC basis, pulsed exposures may be more toxic than continuous exposures typically used in guideline value derivation.
间歇性、波动和脉冲污染物排放可能导致生物受到高度变化的毒物暴露。本研究调查了连续和脉冲暴露于复杂中和排水（NDW）和溶解铜加标稀释 NDW 对绿藻 Pseudokirchneriella subcapitata 的毒性。比较了持续时间为 1 至 48 小时的单一脉冲和连续暴露（72 小时）对藻类生长率抑制的影响，基于时间平均浓度（TAC）。在脉冲去除后 24-48 小时内，藻类生长率通常恢复到对照水平。与等效 TAC（%NDW）的脉冲暴露相比，NDW 的连续暴露对藻类的毒性相似或略高。NDW 的毒性主要归因于金属，主要阳离子可能导致相加（直接毒性）和拮抗（痕量金属生物利用度降低）的影响。对于稀释 NDW 中的溶解铜，脉冲暴露比等效溶解铜 TAC 的连续暴露略高毒性，差异的大部分原因是处理之间可利用铜浓度的差异。结果表明，对于脉冲暴露，源自连续慢性暴露的有毒物质的水质基准值可以根据 TAC 放宽一个与 TAC 相关的因子，目的是提供足够的保护但不过于保守的结果。该研究强调了天然水质参数（如水硬度和 DOC）对金属形态和毒性的影响，并表明这些参数对于特定于地点的水质基准值推导尤为重要，因为基于 TAC，脉冲暴露可能比通常用于基准值推导的连续暴露更具毒性。
