澳大利亚海上石油和天然气活动产生的采出水(PW)通常在处理后排放到海洋。这些有机和无机化合物的复杂混合物可能对接收水造成重大的环境风险,如果管理不当。澳大利亚的石油和天然气运营商必须证明其活动对环境的影响被管理到合理可行的尽可能低的水平(ALARP),例如,通过风险评估,将PW的预测无影响浓度(PNEC)与预测环境浓度(PEC)进行比较。概率物种敏感性分布(SSD)方法越来越多地用于得出PWPNEC,并随后计算保护接收环境中指定百分比的物种所需的PW稀释(称为“安全”稀释)(例如,95%或99%,或分别为PC95和PC99)。与SSD相关的限制包括将单个模型拟合到小型(6-8种)数据集,导致与PC99和PC95结果相关的区域存在很大的不确定性(非常宽的95%置信区间)。SSD方法的最新进展,以模型平均的形式,声称通过将多个模型的平均模型拟合应用于数据集来克服这些限制中的一些。我们评估了四种不同的SSD软件包的优势和局限性,这些软件包用于确定来自澳大利亚西北大陆架外的天然气/凝析油平台的五个PWs的PNEC值。与单一模型拟合相比,模型平均减少了PC95和PC99值周围极端不确定性的发生,并且由于缺乏拟合单一模型而导致的过于保守的PC99和PC95值的推导不太容易。我们的结果支持使用模型平均来提高推导的PNEC和随后的“安全”稀释值的鲁棒性,以用于PW排放管理和风险评估。此外,考虑到同行评审文献中缺乏此类信息,我们介绍并讨论了PW的毒性。
Produced water (PW) generated by Australian offshore oil and gas activities is typically discharged to the ocean after treatment. These complex mixtures of organic and inorganic compounds can pose significant environmental risk to receiving waters, if not managed appropriately. Oil and gas operators in Australia are required to demonstrate that environmental impacts of their activity are managed to levels that are as low as reasonably practicable, for example, through risk assessments comparing predicted no-effect concentrations (PNECs) with predicted environmental concentrations of PW. Probabilistic species sensitivity distribution (SSD) approaches are increasingly being used to derive PW PNECs and subsequently calculating dilutions of PW (termed \"safe\" dilutions) required to protect a nominated percentage of species in the receiving environment (e.g., 95% and 99% or PC95 and PC99, respectively). Limitations associated with SSDs include fitting a single model to small (six to eight species) data sets, resulting in large uncertainty (very wide 95% confidence limits) in the region associated with PC99 and PC95 results. Recent advances in SSD methodology, in the form of model averaging, claim to overcome some of these limitations by applying the average model fit of multiple models to a data set. We assessed the advantages and limitations of four different SSD software packages for determining PNECs for five PWs from a gas and condensate platform off the North West Shelf of Australia. Model averaging reduced occurrences of extreme uncertainty around PC95 and PC99 values compared with single model fitting and was less prone to the derivation of overly conservative PC99 and PC95 values that resulted from lack of fit to single models. Our results support the use of model averaging for improved robustness in derived PNEC and subsequent \"safe\" dilution values for PW discharge management and risk assessment. In addition, we present and discuss the toxicity of PW considering the paucity of such information in peer-reviewed literature. Integr Environ Assess Manag 2024;20:498-517. © 2023 Commonwealth Scientific and Industrial Research Organisation. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).