Department of Chemical, Biochemical, and Environmental Engineering, University of Maryland Baltimore County , Baltimore, Maryland 21250, United States.
Environ Sci Technol. 2017 Jun 20;51(12):7018-7027. doi: 10.1021/acs.est.7b01020. Epub 2017 Jun 9.
Although the field of passive sampling to measure freely dissolved concentrations in sediment porewater has been sufficiently advanced for organic compounds in the low- to midrange of hydrophobicity, in situ passive sampling of strongly hydrophobic polychlorinated biphenyls (PCBs) is still challenged by slow approach to equilibrium. Periodic vibration of polyethylene (PE) passive samplers during exposure has been previously shown to enhance the mass transfer of polycyclic aromatic hydrocarbons (PAHs) from sediment into PE. Herein, we used a new vibrating platform, developed based on our earlier platform design, to demonstrate the effectiveness of periodic vibration for strongly hydrophobic compounds such as hexa-, hepta-, and octachloro-PCBs. Uptake of PCBs in PE after 7, 14, 28, and 56 days under different vibration modes was compared to that under static and mixed laboratory deployments. All PCBs reached within 95-100% of equilibrium after 56 days of deployment in the system vibrated briefly every 2 min, while none of the congeners achieved more than 50% of equilibrium in static deployment for the same period. Periodic vibration also increased the dissipation rate of four performance reference compounds (PRCs) from passive samplers. Higher fractional loss of PRCs and closer approach to equilibrium in the vibrated deployment resulted in estimation of corrected porewater concentrations that were statistically indistinguishable from the true equilibrium values even after a short 7-day deployment. Porewater concentrations of the strongly hydrophobic PCB congeners were overestimated by up to an order of magnitude in the static passive sampler after the same deployment time.
尽管被动采样技术在测量低到中等疏水性有机化合物在沉积物孔隙水中的游离溶解浓度方面已经相当成熟，但原位被动采样强疏水性多氯联苯（PCBs）仍然受到平衡缓慢的挑战。先前已经证明，在暴露期间周期性振动聚乙烯（PE）被动采样器可以增强多环芳烃（PAHs）从沉积物向 PE 中的传质。在此，我们使用了一种新的振动平台，该平台是基于我们早期的平台设计开发的，证明了周期性振动对于强疏水性化合物（如六氯、七氯和八氯 PCB）的有效性。在不同的振动模式下，PE 中 PCBs 的吸收在 7、14、28 和 56 天后与静态和混合实验室部署中的吸收进行了比较。在每 2 分钟短暂振动一次的系统中，所有 PCB 在 56 天的部署后都达到了 95-100%的平衡，而在相同的时间内，没有一种同系物在静态部署中达到了 50%以上的平衡。周期性振动还增加了来自被动采样器的四个性能参考化合物（PRCs）的耗散速率。在振动部署中，PRCs 的分数损失更高，并且更接近平衡，从而估算出的校正后孔隙水浓度与真实平衡值在统计学上没有区别，即使在 7 天的短时间部署后也是如此。在相同的部署时间后，静态被动采样器中强疏水性 PCB 同系物的孔隙水浓度高估了多达一个数量级。
