MIT/WHOI Joint Program in Chemical Oceanography, USA.
Environ Sci Process Impacts. 2018 Jan 24;20(1):220-231. doi: 10.1039/c7em00501f.
Passive sampling is becoming a widely used tool for assessing freely dissolved concentrations of hydrophobic organic contaminants in environmental media. For certain media and target analytes, the time to reach equilibrium exceeds the deployment time, and in such cases, the loss of performance reference compounds (PRCs), loaded in the sampler before deployment, is one of the common ways used to assess the fractional equilibration of target analytes. The key assumption behind the use of PRCs is that their release is solely diffusion driven. But in this work, we show that PRC transformations in the sediment can have a measurable impact on the PRC releases and even allow estimation of that compound's transformation rate in the environment of interest. We found that in both field and lab incubations, the loss of the C 2,4'-DDT PRC from a polyethylene (PE) passive sampler deployed at the sediment-water interface was accelerated compared to the loss of other PRCs (C-labeled PCBs, C-labeled DDE and DDD). The DDT PRC loss was also accompanied by accumulation in the PE of its degradation product, C 2,4'-DDD. Using a 1D reaction-diffusion model, we deduced the in situ degradation rates of DDT from the measured PRC loss. The in situ degradation rates increased with depth into the sediment bed (0.14 d at 0-10 cm and 1.4 d at 30-40 cm) and although they could not be independently validated, these rates compared favorably with literature values. This work shows that passive sampling users should be cautious when choosing PRCs, as degradation processes can affect some PRC's releases from the passive sampler. More importantly, this work opens up the opportunity for novel applications of passive samplers, particularly with regard to investigating in situ degradation rates, pathways, and products for both legacy and emerging contaminants. However, further work is needed to confirm that the rates deduced from model fitting of PRC loss are a true reflection of DDT transformation rates in sediments.
被动采样正成为评估环境介质中疏水性有机污染物游离溶解浓度的广泛应用工具。对于某些介质和目标分析物，达到平衡所需的时间超过了部署时间，在这种情况下，性能参考化合物（PRC）的损失是评估目标分析物部分平衡的常用方法之一，这些化合物在部署前加载在采样器中。使用 PRC 的关键假设是它们的释放仅受扩散驱动。但在这项工作中，我们表明沉积物中 PRC 的转化会对 PRC 的释放产生可测量的影响，甚至可以估计该化合物在感兴趣环境中的转化速率。我们发现，在现场和实验室孵育中，与其他 PRC（C 标记 PCB、C 标记 DDE 和 DDD）相比，部署在水-沉积物界面的聚乙烯（PE）被动采样器中 C 2,4'-DDT PRC 的损失速度加快。DDT PRC 的损失伴随着其降解产物 C 2,4'-DDD 在 PE 中的积累。使用一维反应-扩散模型，我们从测量的 PRC 损失中推断出 DDT 的原位降解速率。原位降解速率随沉积物深度的增加而增加（0-10 cm 处为 0.14 d，30-40 cm 处为 1.4 d），尽管这些速率无法独立验证，但与文献值相比具有可比性。这项工作表明，被动采样器用户在选择 PRC 时应谨慎，因为降解过程会影响一些 PRC 从被动采样器中的释放。更重要的是，这项工作为被动采样器的新应用开辟了机会，特别是在调查痕量和新兴污染物的原位降解速率、途径和产物方面。然而，需要进一步的工作来确认从 PRC 损失的模型拟合中推断出的速率是否真实反映了沉积物中 DDT 的转化速率。
