Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu, Matsue, Shimane, 690-8504, Japan.
Arch Environ Contam Toxicol. 2010 Apr;58(3):605-12. doi: 10.1007/s00244-010-9466-9. Epub 2010 Jan 22.
To determine the potential impact of contaminants on the aquatic vascular plants Lemna sp., toxicity tests are usually conducted for a 4- to 14-day exposure, and the toxicity is usually expressed as EC50. However, the effects of longer exposure and the recovery potential after exposure to chemicals are other important factors which should be considered. We present the relative risks of a variety of exposure scenarios and recovery potentials from damage, using herbicides with different modes of action. Toxicity was assessed on the basis of both EC50 and relative growth rate (RGR) compared with untreated controls in exposure and recovery. The EC50 of atrazine was found to be 89 ppb, and its phytostatic concentrations were 1600 and 800 ppb for exposure periods of 14 and 28 days, respectively, and no phytocidal effects were observed up to 3200 ppb for a 28-day exposure. The RGR in recovery was not affected by the RGR in exposure, and regrowth was possible even after complete inhibition of growth for 28 days at the highest concentration tested. Alachlor, with an EC50 of 31 ppb, was phytostatic at 400 ppb for a 14-day exposure and phytocidal at 200 ppb for 21- and 28-day exposures. Paraquat, with an EC50 of 31 ppb, showed phytocidal rather than phytostatic effects. All phytostatic fronds could not grow in the recovery period, and the phytocidal concentration decreased with exposure period, from 80 ppb for a 7-day exposure to 20 ppb for 21- and 28-day exposures. The RGR of alachlor and paraquat in recovery was dependent on the RGR in exposure. In the case of cyclosulfamuron, phytostatic concentrations were 100 and 50 ppb for 7- and 14-day exposures, respectively. In the case of exposures longer than 21 days, however, it exhibited phytocidal activity at 10 ppb. The results of this study suggest that it is important to examine the effects of chemicals over a longer exposure period as well as the recovery potential from damage for reliable ecological risk assessment.
为了确定污染物对水生维管束植物浮萍的潜在影响，通常进行 4-14 天的暴露毒性测试，毒性通常表示为 EC50。然而，更长时间的暴露和暴露后化学品恢复潜力等其他重要因素也应加以考虑。我们使用具有不同作用模式的除草剂来评估各种暴露情况和恢复潜力的相对风险。在暴露和恢复过程中，根据 EC50 和相对生长率（RGR）与未经处理的对照进行毒性评估。发现莠去津的 EC50 为 89 ppb，其暴露 14 天和 28 天的植物抑制浓度分别为 1600 和 800 ppb，在 3200 ppb 下未观察到植物杀伤作用。恢复期间的 RGR 不受暴露期间 RGR 的影响，即使在最高浓度下完全抑制生长 28 天后也可以重新生长。乙草胺的 EC50 为 31 ppb，在 14 天暴露时表现为植物抑制，在 21 天和 28 天暴露时在 200 ppb 时表现为植物杀伤。百草枯的 EC50 为 31 ppb，表现出植物杀伤作用而不是植物抑制作用。所有的植物抑制叶片在恢复期都不能生长，而植物杀伤浓度随暴露时间而降低，从 7 天暴露的 80 ppb 降低到 21 天和 28 天暴露的 20 ppb。乙草胺和百草枯在恢复期的 RGR 取决于暴露期的 RGR。在环丙磺隆的情况下，7 天和 14 天暴露的植物抑制浓度分别为 100 和 50 ppb。然而，在暴露时间超过 21 天的情况下，它在 10 ppb 时表现出植物杀伤活性。本研究结果表明，在进行可靠的生态风险评估时，不仅要检查较长暴露时间的影响，还要检查从损伤中恢复的潜力。
