Determination of uptake kinetics and sampling rates for 56 organic micropollutants using "pharmaceutical" POCIS

Abstract

The literature increasingly reports sampling rates (Rs) for Polar Organic Chemical Integrative Samplers (POCIS) but the data obtained come from various calibration systems that are not always well-defined (agitation, temperature, measured micropollutant concentrations in water,…). In order to obtain accurate laboratory Rs for priority and emerging substances, POCIS need to be exposed in a robust and well-defined calibration system. Thus, we built a flow-through calibration system containing tap water spiked with 56 organic micropollutants (alkylphenols and phenols, hormones, pesticides, pharmaceuticals, UV filter). POCIS were immersed for up to 28 days. Tap water micropollutant concentrations and additional parameters (temperature, pH, conductivity, dissolved organic carbon, flow velocities) were kept constant and controlled throughout the calibration experiment. Based on the observed uptake kinetics, we distinguished four types of micropollutant accumulation patterns: curvilinear accumulation (30 molecules, group 1), accumulation with an inflexion point (13 molecules, group 2), random accumulation (eight molecules, group 3), and no or very low accumulation (five molecules, group 4). Rs was calculated for 43 out of 56 micropollutants (groups 1 and 2). Calculated Rs values ranged from 0.030 L/d to 0.398 L/d. POCIS can supply TWA concentrations for hormones, pesticides, several pharmaceuticals, a few alkylphenols, and the UV filter. Our Rs results are generally less than two fold-different (higher or lower depending on target molecule) to the literature data using the same type of calibration system or for micropollutants with log Kow>2.65. We found a quadratic correlation between Rs and log D for betablockers, herbicides and hormones.