US Environmental Protection Agency (USEPA) Procedures for the Derivation of Equilibrium Partitioning Sediment Benchmarks (ESBs) for the Protection of Benthic Organisms: Metal Mixtures are based on the principle that metals toxicity to benthic organisms is determined by bioavailable metals concentrations in porewater. One ESB is based on the difference between simultaneously extracted metal (SEM) and acid volatile sulfide (AVS) concentrations in sediment (excess SEM). The excess SEM ESBs include a lower uncertainty bound, below which most samples (95%) are expected to be “nontoxic” (defined as a bioassay mortality rate ≤24%), and an upper uncertainty bound, above which most samples (95%) are expected to be “toxic” (defined as a mortality rate >24%). Samples that fall between the upper and lower bounds are classified as “uncertain.” Excess SEM ESBs can, in principle, be improved by normalizing for organic carbon (OC). OC is a binding phase that reduces metals bioavailability. OC normalization should improve the accuracy of bioavailable metal concentration estimates, thus tightening uncertainty bounds. We evaluated field-collected sediments from 13 studies with excess SEM, OC, and bioassay data (n = 740). Use of the OC-normalized excess SEM benchmarks did not improve prediction accuracy. The ESB model predicts OC-normalized excess SEM exceeding the upper benchmark even when toxicity is not observed, because error in the OC normalization model increases at low OC concentrations. To minimize the likelihood of incorrectly identifying nontoxic samples as toxic, we recommend that OC normalization of excess SEM should not be considered for sediments with an OC concentration <1% and is questionable for sediments with an OC concentration of 1%–4%. Additional focused studies are needed to confirm or refine the minimum sediment OC concentrations that are applicable for reducing uncertainty in toxicity predictions due to excess SEM. Integr Environ Assess Manag 2022;18:174–186. © 2021 SETAC

中文翻译：

---

沉积物毒性数据和过量同时从现场收集的样品中提取金属：与美国环境保护署基准的比较

美国环境保护署 (USEPA)用于保护底栖生物的平衡分配沉积物基准 (ESB) 推导程序：金属混合物是基于金属对底栖生物的毒性由孔隙水中的生物可利用金属浓度决定的原理。一种 ESB 基于沉积物中同时提取的金属 (SEM) 和酸性挥发性硫化物 (AVS) 浓度之间的差异（过量 SEM）。过量的 SEM ESB 包括一个不确定性下限，低于该下限，大多数样品 (95%) 预计为“无毒”（定义为生物测定死亡率 ≤24%），以及一个不确定性上限，高于该上限，大多数样品（95% ) 预计是“有毒的”（定义为死亡率>24%）。落在上限和下限之间的样本被归类为“不确定”。原则上，过量的 SEM ESB 可以通过对有机碳 (OC) 进行归一化来改善。OC 是降低金属生物利用度的结合相。OC 标准化应提高生物可利用金属浓度估计的准确性，从而收紧不确定性界限。我们用多余的 SEM、OC 和生物测定数据评估了 13 项研究中现场收集的沉积物（n  = 740)。使用 OC 归一化的超额 SEM 基准并没有提高预测准确性。即使没有观察到毒性，ESB 模型也预测 OC 归一化过量 SEM 超过上限基准，因为 OC 归一化模型中的误差在 OC 浓度低时会增加。为了尽量减少错误地将无毒样品识别为有毒样品的可能性，我们建议对于 OC 浓度 <1% 的沉积物不应考虑对过量 SEM 进行 OC 归一化，而对于 OC 浓度为 1%–4% 的沉积物是有问题的。需要额外的重点研究来确认或完善适用于减少由于过量 SEM 导致的毒性预测不确定性的最低沉积物 OC 浓度。2022 年整合环境评估管理；18:174–186。© 2021 SETAC