Characterization of fundamental adsorption behavior of pesticides on polar organic chemical integrative sampler (POCIS).

Determination of accurate time weighted average concentrations (TWACs) of chemicals in water using polar organic chemical integrative sampler (POCIS) is still unsatisfactory, due to the limited understanding of environmental factors impact on POCIS uptake. The objective of this research was to improve understanding of environmental factors effects on POCIS uptake by performing laboratory POCIS exposure experiments. The research mainly focused on 12 pesticides, including common types of pesticides used in the US, with a range of physico-chemical properties. A UPLC-MS/MS method was developed for water and POCIS extract samples analyses of select pesticides. The effects of change in hydrodynamic conditions as well as change in temperature on POCIS sampling rate (Rs) were investigated. Flow velocities at the surface of POCIS devices were determined using a novel method based on the measurement of mass transfer coefficients of the water boundary layer near the surface of POCIS devices. Hydrodynamic conditions effects on POCIS Rs were mainly observed between stagnant flow conditions and 6 cm/s. An Arrhenius model was used to describe the linear relationship between temperature and Rs and the use of temperature-corrected Rs to accurately calculate TWAC was evaluated in field settings. The investigation of suspended sediment effects on POCIS uptake suggested that suspended sediment do not have an effect on POCIS Rs for most compounds, but it may affect transport processes across POCIS membrane for compounds with relatively high hydrophobicity and relatively high affinity to POCIS membrane. The investigation of concentration exposure effects on POCIS uptake demonstrated that concentration exposure has no effect on POCIS Rs or POCIS integrative capability for concentrations ranging from 3 to 60 µg/L over a 21-day exposure period. However, POCIS integrative capabilities may be shortened for POCIS exposures to concentrations higher than 60 µg/L. Additionally, there was an interesting increase in POCIS Rs observed between constant concentration and pulse concentration exposures.