In 2016, the US Environmental Protection Agency (USEPA) issued revised aquatic life water quality criteria for selenium (Se). The criteria (“elements”) consisted of threshold concentrations applicable to fish tissue (three tissue types, though the egg and ovary tissue takes precedence over the whole-body and muscle tissue thresholds), and water column. The agency rationalized that measured concentrations of Se in fish tissue were more predictive of potential adverse reproductive effects than those measured in external media. The agency provided two mechanisms for derivation of site-specific Se water criteria: a bioaccumulation factor (BAF) approach, and a partitioning-based bioaccumulation model approach. The use of either approach assumes that fish tissue concentrations exceed one or more of the tissue criteria. We compared the two approaches using fish tissue samples from various species in the Ohio River to evaluate resulting similarities and differences in the calculated Se water quality criteria. Fish (five species) were collected near two coal-fired power plants at sites unaffected by Se from wastewater discharges. Using results for all species and all sites combined, the resulting site-specific Se criteria for the BAF and partitioning-based model approach (median values) were 2.0 and 1.5 µg/L, respectively. Considering all species, resulting criteria differed little between the two power plant locations. Resulting criteria for both methods were strongly influenced by a small (less than detection) background Se water concentration. At least for the upper Ohio River, the BAF approach (requiring less input data) seems adequate for derivation of site-specific Se water criteria. In the current study, however, none of the tissue samples exceeded USEPA's tissue criteria. Thus, the decision to derive site-specific Se water quality criteria should be evaluated on a case-by-case basis, because the process may result in either a more stringent or less stringent value, wholly dependent on local factors. Integr Environ Assess Manag 2021;17:1255–1262. © 2021 SETAC

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特定地点硒水质标准的推导：两种方法的比较和监管影响

2016 年，美国环境保护署 (USEPA) 发布了硒 (Se) 的修订水生生物水质标准。标准（“要素”）包括适用于鱼类组织的阈值浓度（三种组织类型，尽管卵和卵巢组织优先于全身和肌肉组织阈值）和水柱。该机构解释说，与在外部介质中测量的结果相比，在鱼组织中测量的硒浓度更能预测潜在的不利生殖影响。该机构提供了两种推导特定地点的硒水标准的机制：生物累积因子 (BAF) 方法和基于分区的生物累积模型方法。使用任一方法都假定鱼组织浓度超过一个或多个组织标准。我们使用俄亥俄河中不同物种的鱼组织样本比较了两种方法，以评估计算出的硒水质标准的异同。在两个燃煤发电厂附近收集了鱼类（五种），这些地点不受废水排放中硒的影响。综合使用所有物种和所有地点的结果，BAF 和基于分区的模型方法（中值）的特定地点硒标准分别为 2.0 和 1.5 µg/L。考虑到所有物种，两个发电厂位置之间的结果标准差异不大。两种方法的结果标准都受到小的（低于检测值）背景硒水浓度的强烈影响。至少在俄亥俄河上游，BAF 方法（需要较少的输入数据）似乎足以推导特定地点的硒水标准。然而，在目前的研究中，没有一个组织样本超过 USEPA 的组织标准。因此，应根据具体情况对确定特定地点的硒水质标准的决定进行评估，因为该过程可能导致更严格或不那么严格的值，完全取决于当地因素。Integr Environ Assess Manag 2021；17:1255-1262。© 2021 SETAC