Calibration of silicone rubber rods as passive samplers for pesticides at two different flow velocities: Modeling of sampling rates under water boundary layer and polymer control

Abstract

There is a need to determine time-weighted average concentrations of polar contaminants such as pesticides by passive sampling in environmental waters. Calibration data for silicone rubber-based passive samplers are lacking for this class of compounds. The calibration data, sampling rate (R ), and partition coefficient between silicone rubber and water (K ) were precisely determined for 23 pesticides and 13 candidate performance reference compounds (PRCs) in a laboratory calibration system over 14 d for 2 water flow velocities, 5 and 20 cm s . The results showed that an in situ exposure duration of 7 d left a silicone rubber rod passive sampler configuration in the linear or curvilinear uptake period for 19 of the pesticides studied. A change in the transport mechanism from polymer control to water boundary layer control was observed for pesticides with a log K of approximately 3.3. The PRC candidates were not fully relevant to correct the impact of water flow velocity on R . We therefore propose an alternative method based on an overall resistance to mass transfer model to adjust R from laboratory experiments to in situ hydrodynamic conditions. We estimated diffusion coefficients (D ) and thickness of water boundary layer (δ ) as adjustable model parameters. Log D values ranged from -12.13 to -10.07 m s . The estimated δ value showed a power function correlation with water flow velocity. Environ Toxicol Chem 2018;37:1208-1218. © 2017 SETAC.

Passive Sampler Exchange Kinetics in Large and Small Water Volumes Under Mixed Rate Control by Sorbent and Water Boundary Layer

“…Sorbent resistance is sometimes incorporated in the sampling rate model by adopting a time‐independent δ s because this simplifies modeling efforts (McDonough et al 2016; Martin et al 2018). Adopting δ s = L /3 seems to be a fair estimate for this purpose in the case of fixed C w exposures.…”

Development and Calibration of the Polar Organic Chemical Integrative Sampler (POCIS) for Neonicotinoid Pesticides

“…In recent years, various passive samplers have been devised for monitoring neonicotinoid pesticides in aquatic environments; these include Chemcatcher (Schäfer et al 2008; Sánchez-Bayo and Hyne 2014), a silicone rubber rod (Martin et al 2018), and the polar organic chemical integrative sampler (POCIS;Ahrens et al 2015;Challis et al 2018;Sultana et al 2018;Noro et al 2019;Xiong et al 2019). The collected amounts for Chemcatcher increased linearly for 20 d (Sánchez-Bayo and Hyne 2014).…”

“…The collected amounts for Chemcatcher increased linearly for 20 d (Sánchez-Bayo and Hyne 2014). The sampling rate (R s ) of the silicone rubber rod has been relatively low, at 0.04 mL/d at a flow rate of 5 cm/s (Martin et al 2018). The POCIS sampler has been used for field tests (Challis et al 2018;Sultana et al 2018;Xiong et al 2019), even though the linear range was relatively short, 3 to 14 d (Noro et al 2019), or the collected amount increased nonlinearly for 26 d of deployment (Ahrens et al 2015).…”

Development and application of an in-house library and workflow for gas chromatography–electron ionization–accurate-mass/high-resolution mass spectrometry screening of environmental samples

“…In the case of the POCIS, this SDL was 2.5 ng (the lowest level tested) for most compounds, except for 2-ethylhexyl salicylate and pyrene (SDL: 25 ng), where triclosan could only be identified in the derivatized samples. Considering typical values of sampling rate (R s ) ranging between 0.01 and 1 L/day [42][43][44][45], that would translate into SDLs referring to water in the 0.18-35 ng/L range, depending on the actual R s value and deployment time of the passive sampler (1 or 2 weeks). Reported SDL values in screening studies of surface waters, most of them based on LC-HRMS, were in the range 1.25-500 ng/L [46][47][48].…”