Silva Camila R, Masini Jorge C
CETESB - Environmental Company of São Paulo State, Av. Prof. Frederico Hermann Jr 345, 05459-900, São Paulo, SP, Brazil.
Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-000, São Paulo, SP, Brazil.
Environ Pollut. 2023 Apr 15;323:121258. doi: 10.1016/j.envpol.2023.121258. Epub 2023 Feb 10.
There is a growing demand for assessing the concentrations of Hydrophobic Organic Contaminants (HOCs) in aquatic environments, including Persistent Organic Pollutants (POPs). The hydrophobicity of POPs challenges their quantification in waters due to the sub-trace concentrations, especially when using conventional spot sampling. The results from the conventional samples are only a "snapshot" of the concentrations (if detected) at the specific sampling moment. Contrary, passive sampling provides average concentration levels over weeks or months from the quantification of accumulated pollutants during the deployment period. The present work compared ethylene vinyl acetate (EVA) and silicon rubber (SR) as monophasic passive samplers to measure dissolved concentrations of HOCs. Four classes of POPs were studied: (i) polychlorinated dibenzo-p-dioxins (PCDDs), (ii) polychlorinated dibenzofurans (PCDFs), (iii) polychlorinated biphenyls (PCBs), including the dioxin-like congeners, and (iv) the polybrominated diphenyl ethers (PBDEs). The polymer-water partition coefficients (K), determined by the cosolvent and crossed calibrations, were, on average, one logarithmic unit larger in EVA than in the SR. The diffusion coefficients (D) estimated by the "film-stacking" method were, on average, two orders of magnitude smaller in the EVA than in the SR. For both polymers, the theoretical model of mass transfer resistance confirmed that the water boundary layer controlled the absorption, thus allowing the use of Performance Reference Compounds (PRCs) to estimate the in-situ sampling rates. Larger K's in EVA may be an advantage because they imply longer time scales to reach equilibrium, higher absorption capacities and hence a higher absorbed contaminant mass, especially for compounds that reach equilibrium relatively faster (log K < 5). In addition, the longer times to attain equilibrium for EVA maintain this sampler longer in the linear phase of absorption, and the time-weighted average concentration may only be assessed in this phase when the compounds have not yet reached equilibrium.
对评估包括持久性有机污染物（POPs）在内的水生环境中疏水性有机污染物（HOCs）浓度的需求日益增长。由于痕量浓度较低，尤其是在使用传统的定点采样时，POPs的疏水性给其在水中的定量分析带来了挑战。传统样品的结果仅仅是特定采样时刻浓度（如果检测到）的一个“快照”。相反，被动采样通过对部署期间累积污染物的定量分析，可提供数周或数月内的平均浓度水平。本研究比较了乙烯醋酸乙烯酯（EVA）和硅橡胶（SR）作为单相被动采样器来测量HOCs的溶解浓度。研究了四类POPs：（i）多氯二苯并 - p - 二恶英（PCDDs），（ii）多氯二苯并呋喃（PCDFs），（iii）多氯联苯（PCBs），包括类二恶英同系物，以及（iv）多溴二苯醚（PBDEs）。通过助溶剂和交叉校准确定的聚合物 - 水分配系数（K），EVA中的平均比SR中的大一个对数单位。通过“膜堆叠”方法估算的扩散系数（D），EVA中的平均比SR中的小两个数量级。对于这两种聚合物，传质阻力的理论模型证实水边界层控制着吸收过程，因此可以使用性能参考化合物（PRCs）来估算原位采样速率。EVA中较大的K值可能是一个优势，因为这意味着达到平衡所需的时间尺度更长、吸收能力更高，从而吸收的污染物质量更高，特别是对于相对较快达到平衡的化合物（log K < 5）。此外，EVA达到平衡所需的时间更长，使得该采样器在吸收的线性阶段保持更长时间，并且只有当化合物尚未达到平衡时，才可以在这个阶段评估时间加权平均浓度。
