Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA.
Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts, USA.
Environ Toxicol Chem. 2020 May;39(6):1165-1173. doi: 10.1002/etc.4714. Epub 2020 May 12.
Low-density polyethylene sheets are used as passive samplers for aquatic environmental monitoring to measure the freely dissolved concentration (C ) of hydrophobic organic contaminants (HOCs). Freely dissolved HOCs in water will partition into the polyethylene until a thermodynamic equilibrium is achieved; that is, the HOC's activity in the passive sampler is the same as its activity in the surrounding environment. One way to evaluate the equilibrium status or estimate the uptake kinetics is by using performance reference compounds (PRCs). A fractional equilibrium (f ) can be determined for target HOCs, under the assumption that PRC desorption from the passive sampler occurs at the same rate as for the unlabeled target HOCs. However, few investigations have evaluated how effectively and accurately PRCs estimate target contaminant C under in situ conditions. In the present study, polyethylene passive samplers were preloaded with 6 C-labeled polychlorinated biphenyls (PCBs) as PRCs; deployed in New Bedford Harbor, Massachusetts, USA; and collected after 30-, 56-, 99-, and 129-d deployments. Using this unique temporal sampling design, PRC results from each deployment were fit to a diffusion model to estimate the C of 27 PCB congeners and compare the results between the different deployment times. Smaller PCBs had variable concentrations over the 4 deployments, whereas mid-molecular weight PCBs had consistent C measurements for all deployments (relative standard deviation <20%). High-molecular weight PCBs had the largest C estimates after 30 d; these estimates and their standard deviations decreased with longer deployment times. These findings suggest that when targeting PCBs with more than 6 chlorines or contaminants with a log octanol-water partition coefficient ≥6.5, a deployment time longer than 30 d may be prudent. Environ Toxicol Chem 2020;39:1165-1173. © 2020 SETAC.
低密度聚乙烯片被用作水生环境监测的被动采样器，以测量疏水性有机污染物 (HOCs) 的自由溶解浓度 (C)。水中的自由溶解 HOC 将分配到聚乙烯中，直到达到热力学平衡；也就是说，被动采样器中 HOC 的活性与其周围环境中的活性相同。评估平衡状态或估计吸收动力学的一种方法是使用性能参考化合物 (PRC)。可以确定目标 HOC 的分数平衡 (f)，前提是 PRC 从被动采样器中的解吸速率与未标记的目标 HOC 相同。然而，很少有研究评估 PRC 在现场条件下对目标污染物 C 的估计效果和准确性。在本研究中，聚乙烯被动采样器预先加载了 6 个 C 标记的多氯联苯 (PCBs) 作为 PRC；在美国马萨诸塞州新贝德福德港部署；并在 30、56、99 和 129 天的部署后收集。使用这种独特的时间采样设计，每次部署的 PRC 结果都拟合到扩散模型中，以估计 27 种 PCB 同系物的 C，并比较不同部署时间之间的结果。较小的 PCB 在 4 次部署中的浓度变化较大，而中分子量的 PCB 在所有部署中的 C 测量值都一致（相对标准偏差 <20%）。高分子量 PCB 在 30 天后的 C 估计值最大；这些估计值及其标准偏差随着部署时间的延长而降低。这些发现表明，当目标是具有超过 6 个氯原子的 PCB 或具有 log 辛醇-水分配系数≥6.5 的污染物时，30 天以上的部署时间可能是谨慎的。环境毒理化学 2020；39:1165-1173。 © 2020 SETAC。
