Silva, Ricardo Jorge Neves Bettencourt da, 1971-Vrana, BranislavGomes, Luís Gonçalo Brás2018-12-032018-12-0320182018http://hdl.handle.net/10451/35568Tese de mestrado, Química (Química Analítica) Universidade de Lisboa, Faculdade de Ciências, 2018It is of greatest importance to preserve and safeguard the remaining water resources, and to ensure their sustainable management. Hence, environmental monitoring of water is becoming increasingly important and policy programs on water management have been adopted by authorities around the globe with ambitious goals and approaches that can be used for preserving quality of water. Therefore, there is a growing interest in assessing the concentration and distribution of new nonregulated organic contaminants (emerging contaminants) in the environment. The measurement of freely dissolved concentrations using conventional approaches is challenging due to the low concentrations that may be encountered and their temporally variable concentrations. The subsequent laboratory analysis of the sample provides only a snapshot of the levels of pollutants at the time of sampling and episodic pollution events can be missed. Passive sampling technology has been developing very quickly for the past 20 years and, today, these methods represent a viable alternative to traditional sampling methods as they have shown to be promise as tools for measuring concentrations of a wide range of priority pollutants. Depending on sampler design, the mass of pollutant accumulated by a sampler should reflect either the concentration with which the device is at equilibrium or the time-averaged concentration to which the sampler was exposed enabling the estimation of freely dissolved concentrations of contaminants of emerging concern in water. The use of passive sampling method for estimation of freely dissolved concentrations of emerging contaminants requires the calibration of the passive sampler device. The partition coefficients of a target compound between the passive sampler and water is one of the needs for a successful calibration of the passive sampler device. Measurement of partition coefficients between silicone rubbers and water, Kpw, becomes more difficult as the hydrophobicity of the compound increases. Experimental challenges include long extraction times, sorption to various surfaces and materials, and incomplete dissolution of the compound in the aqueous phase. In order to avoid these artifacts and to shorten experimental time, a series of equilibration experiments of target compounds between the sampler and water in a closed system were performed. For polycyclic aromatic hydrocarbons (PAHs) and personal care products (PCPs), polymer-water partition coefficients were determined in ultra-pure water for AlteSil™ silicone rubbers using equilibration by both compound release and uptake kinetics. The direct contact method is used to equilibrate polymers under enhanced pressure. A spiked silicone rubber sheet is sandwiched between two other unspiked sheets to decrease its concentration and perform new equilibration process for polymer-water partition coefficients estimation. Estimated polymer-water partition coefficient values are in good agreement with the values from different experimental methods and with the literature values. Also, a study of temporal evolution of the concentration of target compounds in the aqueous phase and the wall of the bottles was performed. However, only sampling rates from equilibration experiments were estimated. The Monte Carlo method is used to evaluate the uncertainty of the complex determination of partition coefficients. For Monte Carlo simulation, a mathematical model is built to describe all interactions between input quantities that affect partition coefficients determination. From that model, mathematical samples from each parameter are generated, which represent estimated values of the input variables, and combined to estimate the distribution of the measurement result. Probability density functions are used to represent the statistical distribution of each input parameter. The results from the 105 Monte Carlo trials are used to estimate the output quantity value and its associated uncertainty.engAmostragem passivaCoeficientes de partiçãoHPAsPCPsMétodo de Monte CarloTeses de mestrado - 2018master thesis202190994