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 (SR)-based passive samplers are lacking for this class of compounds. The calibration data, sampling rate (Rs) and partition coefficient between SR and water (Ksw) were precisely determined for 23 pesticides and 13 candidate performance reference compounds (PRCs) in a laboratory calibration system over 14 d for two water flow velocities, 5 cm s−1 and 20 cm s−1. Results showed that an in situ exposure duration of 7 d left a SR 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 Ksw of around 3.3. The PRC candidates were not fully relevant to correct the impact of water flow velocity on Rs. We therefore propose an alternative method based on an overall resistance to mass transfer model to adjust Rs from laboratory experiments to in situ hydrodynamic conditions. We estimated diffusion coefficients (Ds) and thickness of water boundary layer (δw) as adjustable model parameters. Log Ds values ranged from −12.13 to −10.07 m2 s−1. The estimated δw value showed a power function correlation with water flow velocity. This article is protected by copyright. All rights reserved
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