Evaluation Of A Passive Sampling Device Psd To Sequester Pesticides From Irrigation Water PDF Download

The primary goal of this dissertation was to develop and evaluate an improved aquatic passive sampling device (PSD) for measurement of polar organic contaminants. Chemical uptake of current polar-PSDs (e.g., POCIS - polar organic chemical integrative sampler) is dependent on the specific environmental conditions in which the sampler is deployed (flow-rate, temperature), leading to large uncertainties when applying laboratory-derived sampling rates in-situ. A novel configuration of the diffusive gradients in thin-films (DGT) passive sampler was developed to overcome these challenges. The organic-DGT (o-DGT) configuration comprised a hydrophilic-lipophilic balance® sorbent binding phase and an outer agarose diffusive gel (thickness = 0.5-1.5 mm), notably excluding a polyethersulfone protective membrane which is used with all other polar-PSDs. Sampler calibration exhibited linear uptake and sufficient capacity for 34 pharmaceuticals and pesticides over typical environmental deployment times, with measured sampling rates ranging from 9-16 mL/d. Measured and modelled diffusion coefficients (D) through the outer agarose gel provided temperature-specific estimates of o-DGT sampling rates within 20% (measured-D) and 30% (modelled-D) compared to rates determined through full-sampler calibration. Boundary layer experiments in lab and field demonstrated that inclusion of the agarose diffusive gel negated boundary layer effects, suggesting that o-DGT uptake is largely insensitive to hydrodynamic conditions. The utility of o-DGT was evaluated under a variety of field conditions and performance was assessed in comparison to POCIS and grab samples. o-DGT was effective at measuring pharmaceuticals and pesticides in raw wastewater effluents, small creeks, large fast-flowing rivers, open-water lakes, and under ice at near-zero water temperatures. Concentrations measured by o-DGT were more accurate than POCIS when compared to grab samples, likely resulting from the influence in-situ conditions have on POCIS. Modelled sampling rates were successfully used to estimate semi-quantitative water concentrations of suspect wastewater contaminants using high-resolution mass spectrometry, demonstrating the unique utility of this o-DGT technique. This dissertation establishes o-DGT as a more accurate, user-friendly, and widely applicable passive sampler compared to current-use polar-PSDs. The o-DGT tool will help facilitate more accurate and efficient monitoring efforts and ultimately lead to more appropriate exposure data and environmental risk assessment.