Aquatic integrative passive sampling is a promising approach to measure the time-weighted average concentration, yet our understanding for the sampling mechanisms of polar organic contaminants should be further advanced to fully exploit the potential of the method for real-world applications. This study aimed to characterize the sorption and permeation properties of poly(ether sulfone) (PES) and poly(tetrafluoroethylene) (PTFE) membrane filters (MFs) used for passive samplers. Batch sorption experiments with 14 probe chemicals showed that the sorption by PES was generally strong, with the respective sorption coefficients greater than the octanol-water partition coefficients by 2-3 log units. In contrast, the PTFE filter exhibited no significant sorption for all tested chemicals, representing a promising candidate MF that avoids lag-times and slow responses to fluctuating concentrations. Permeation experiments in a glass cell system and successive modeling demonstrated that, if no sorption to the MF occurs, the MF permeation of a chemical can be fully described with a first-order model that considers the transfer through the aqueous boundary layers and the diffusion in water-filled MF pores. Significant sorption to the MF coincided with substantial delay of permeation, which was successfully modeled with the local sorption equilibrium assumption. These findings have implications for improved sampler configurations and successful models for the chemical uptake.

20Aquatic integrative passive samplers are used for determining aqueous concentrations of polar 21 organic pollutants, yet their uptake mechanisms are poorly understood. We introduce a one-22 dimensional model to simulate uptake by a passive sampler, Chemcatcher. The model considers the 23 uptake as molecular diffusion through a series of the aqueous boundary layer (ABL), the membrane 24 filter (MF), and the sorbent disk with concurrent sorption by matrix of the MF and the disk. Uptake 25 profiles of ca 20 polar chemicals measured over a week and a month were accurately modeled. 26Characteristic behavior such as lag-times, linear and curved uptake, and equilibrating behavior were 27 well-explained by the model. As the model is mechanistically based, it was able to show the 28 combined influences of the MF/water (KMF/w) and disk/water (Kdisk/w) partition coefficients, diffusion 29 coefficients, and the ABL thickness on the sampling rates. On the basis of the model results, we offer 30 three concrete recommendations to achieve linear uptake needed for measuring time-weighted 31 average concentrations: (i) Use a MF that does not significantly sorb chemicals (e.g., log KMF/w < 3) 32 to avoid lag times. (ii) Use a sorbent with strong sorption properties (e.g., log Kdisk/w > 6) for 33 effective trapping of chemicals on the disk top layer. (iii) Make the ABL and/or the MF thicker so 34 that the diffusion toward the disk slows down. 35 36

No abstract

No abstract