Photodegradation of sertraline by solar radiation and influencing factors

Photodegradation is considered to be one of the most important processes of elimination of pharmaceutical drugs from natural water matrices. The high consumption and discharge of these substances, in particular antidepressants, to the aquatic environment supports the need to study degradation processes. This dissertation aimed at studying the direct and indirect photodegradation of sertraline, an antidepressant known for its persistence in the environment, and the evaluation of the influence of environmentally relevant factors in its photodegradation. The photodegradation experiments were developed under simulated solar light and the irradiation times converted to summer sunny days (SSD), an equivalent time in natural environmental conditions. The direct photodegradation was evaluated in solutions of sertraline prepared in ultrapure water and the indirect photodegradation was studied through the addition of photosensitizers (humic substances, Fe(III), nitrates and oxygen). Further irradiation studies were perfomed in aqueous samples collected from two wastewater treatment plants, Vouga river and Ria de Aveiro. The samples were chemically characterized (dissolved organic carbon, nitrates and nitrites and iron determination and UV/Vis spectroscopy). The quantification of sertraline was done by HPLC-UV and photoproducts from direct photodegradation were identified by electrospray mass spectrometry. An observed direct photodegradation rate of sertraline of 0.0062 h-1 was determined, corresponding to a half-life time of 111 h (equivalent to 29 SSD). A significant influence of photosensitizers was observed, the best results being achieved in irradiations of sertraline with humic acids, obtaining a half-life time of 12 h. This was attributed to the hydrophobicity of this substance and higher absortivity in the UV/Vis wavelength, which promote processes of indirect photodegradation. The degradation of sertraline in natural samples was also enhanced comparatively to the direct photodegradation, achieving half-life times between 10 and 25h; the best results were achieved in samples from the primary treatment of a wastewater treatment plant and Ria de Aveiro, with half-life times of 10 and 16 h, respectively. A total of six photoproducts formed during the direct photodegradation of sertraline were identified, three of which were not yet identified in the literature. The main factors contributing to the degradation of sertraline were analysed but this was not fully accomplished, requiring further studies of the composition of the natural matrices and the combined influence of distinct photosensitizers during the irradiation. Nevertheless, it was concluded that the photodegradation of sertraline is greatly influenced by indirect photodegradation processes, promoted by the presence of photosensitizers.

Environmental occurrence and fate of psychiatric pharmaceuticals

Os fármacos são importantes contaminantes ambientais. Nas últimas duas décadas, o número de estudos sobre a ocorrência destes poluentes emergentes em matrizes ambientais aumentou significativamente. Esta ocorrência generalizada preocupa a comunidade científica devido a evidências que comprovam a sua capacidade de interferir nos ecossistemas, mesmo em concentrações muito baixas. No caso particular dos fármacos psiquiátricos é expectável que constituam um risco ecológico significativo. Para uma melhor compreensão do impacto real destes poluentes é essencial que se proceda a uma avaliação extensiva da sua persistência e destino em matrizes ambientais. Os estudos apresentados nesta tese pretendem contribuir para melhorar o conhecimento acerca da ocorrência, persistência e destino ambiental de fármacos psiquiátricos. Para este efeito, foram seleccionados, como objecto de estudo, dois grupos de fármacos: anti-epilépticos (carbamazepina) e fármacos com efeitos ansiolíticos e sedativos (as benzodiazepinas diazepam, oxazepam, lorazepam e alprazolam). A fotodegradação é o principal processo que afecta a persistência de poluentes orgânicos em ambientes aquáticos. Consequentemente, a persistência dos cinco fármacos seleccionados foi avaliada através de estudos de fotodegradação directa e indirecta, tendo em consideração a influência de parâmetros relevantes tais como pH, nível de oxigenação e matéria orgânica dissolvida. Os estudos de fotodegradação aqui descritos foram seguidos por cromatografia micelar electrocinética com a aplicação de um capilar com revestimento dinâmico. Adicionalmente, os fotoprodutos resultantes de fotodegradação directa foram identificados por espectrometria de massa. O estudo da carbamazepina no ambiente é particularmente relevante uma vez que esta foi proposta como um potencial marcador de poluição antropogénica. A sua ocorrência em água superficiais, de sub-solo e residuais foi investigada através da implementação de um ensaio imunológico (ELISA), optimizado para a aplicação a triagens ambientais e amostras com matrizes complexas. O destino deste fármaco na interface água/solo foi também investigado usando solos agrícolas submetidos a fertilizações de longo prazo; este estudo permitiu tirar conclusões acerca da contaminação de águas adjacentes por solos contaminados. O trabalho aqui descrito constitui uma abordagem multidisplinar à problemática da ocorrência de fármacos psiquiátricos no ambiente, contribuindo de forma relevante para esta área de estudo.

Thiram in the environment: effect of humic substances and Cu(II) ions

Em Portugal, o tirame é um dos fungicidas mais utilizados, cujas vendas aumentaram significativamente nos últimos anos, sendo também um dos fungicidas mais utilizados em todo o mundo. No entanto, em comparação com outros pesticidas, existe falta de informação na literatura sobre o seu comportamento em sistemas ambientais, nomeadamente, no que diz respeito à sua degradação no solo ou em águas e produtos a que dá origem. Neste contexto, o objetivo deste trabalho foi estudar a influência das substâncias húmicas e iões cobre no comportamento e destino do tirame no meio ambiente. Foram realizados vários estudos para analisar o comportamento do tirame em solos com diferentes conteúdos de matéria orgânica e de iões cobre, e em águas naturais, estudando como as substâncias húmicas, os iões cobre e a luz solar podem afetar a sua degradação. Os estudos de adsorção-desadsorção do tirame nos solos revelaram que a matéria orgânica do solo e o conteúdo de cobre afetavam os processos de adsorção-desadsorção do tirame, influenciando a sua lixiviação e persistência no solo. De facto, verificou-se que o teor de cobre do solo tinha um efeito bastante marcante no processo de adsorçãodesadsorção do tirame. Verificou-se a ocorrência de reações entre o tirame e os iões cobre, cuja extensão durante os estudos de adsorção pode ser fortemente dependente do teor de cobre do solo e da concentração inicial de tirame em solução. Assim, a escolha do tempo de equilíbrio em estudos de adsorção e a determinação das isotérmicas de adsorção ao solo torna-se uma tarefa difícil. Além disso, os complexos formados com o cobre existente no solo são persistentes, não sendo facilmente lixiviados para as águas subterrâneas. Conclui-se que os iões cobre(II) podem contribuir para a imobilização do tirame no solo e o aumento da persistência dos seus resíduos ligados ao cobre. A partir de estudos de recuperação do tirame em águas naturais verificou-se a ocorrência de uma rápida degradação do tirame, devido provavelmente aos iões metálicos, nomeadamente, iões cobre. Verificou-se que dependendo da razão tirame:Cu podiam ocorrer dois processos: (i) complexação entre o tirame e o cobre, quando não há excesso de iões cobre, sendo o complexo formado mais persistente que o tirame; (ii) ou, quando há um grande excesso de iões cobre, a degradação do tirame e a estabilização dos produtos de degradação por complexação, podendo formar-se complexos que permanecem sem alteração em solução durante pelo menos dois meses. No geral, foi possível, pela primeira vez, identificar alguns dos complexos de cobre formados ao longo do tempo. Por fim, estudou-se a cinética de fotodegradação do tirame em solução aquosa sob a ação da luz solar e identificaram-se, pela primeira vez, três fotoprodutos. Verificou-se um aumento da velocidade de fotodegradação do tirame na presença de substâncias húmicas. Assim, podemos concluir que a matéria orgânica, os iões cobre(II) e a luz solar têm um efeito importante no comportamento do tirame no meio ambiente. Contudo, os iões cobre têm um efeito mais marcante na degradação e persistência dos produtos que são formados.

Occurrence and fate of estrogens and antibiotics in the environment evaluated by low-cost analytical methodologies

Endocrine disruptors and pharmaceuticals are considered to be concerning environmental contaminants. During the last two decades, studies dealing with the occurrence and fate of these emerging contaminants in the aquatic environment have raised attention and its number is constantly increasing. The presence of these contaminants in the environment is particularly important since they are known to induce adverse effects in the ecosystems even at extremely low concentrations. Estrogens and antibiotics, in particular, are identified as capable of induce endocrine disruption and contribute for the appearance of multi-resistant bacteria, respectively. A better assessment and understanding of the real impact of these contaminants in the aquatic environment implies the evaluation of their occurrence and fate, which is the main aim of this Thesis. Two estrogens (17-estradiol and 17-ethinylestradiol) and an antibiotic (sulfamethoxazole) were the contaminants under study and their occurrence in surface and waste waters was assessed by the implementation of enzyme linked immunosorbent assays (ELISAs). The assays were optimized in order to accomplish two important aspects: to analyze complex water samples, giving special attention to matrix effects, and to increase the sensitivity. Since the levels of these contaminants in the environment are extremely low, a pre-concentration methodology was also object of study in this Thesis. Dispersive liquid-liquid microextraction (DLLME) was developed for the preconcentration of E2 and EE2, subsequently quantified by either highperformance liquid chromatography (HPLC) and the previously optimized ELISAs. Moreover, the use of anthropogenic markers, i.e. indicators of human presence or activity, has been discussed as a tool to track the origin and type of contamination. An ELISA for the quantification of caffeine, as an anthropogenic marker, was also developed in order to assess the occurrence of human domestic pollution in Portuguese surface waters. Finally, photodegradation is considered to be one of the most important pathways contributing for the mitigation of pollutants’ presence in the aquatic environment. Both direct and indirect photodegradation of E2 and EE2 were evaluated. Since the presence of humic substances (HS) is known to have a noticeable influence on the photodegradation of pollutants and in order to mimic the real aquatic environment, special attention was given to the influence of the presence and concentration of different fractions of HS on the photodegradation of both hormones.

Assessing the effectiveness of chemical treatment with nanomaterials in improving the quality of different industrial effluents

Industrial activities are the major sources of pollution in all environments. Depending on the type of industry, various levels of organic and inorganic pollutants are being continuously discharged into the environment. Although, several kinds of physical, chemical, biological or the combination of methods have been proposed and applied to minimize the impact of industrial effluents, few have proved to be totally effective in terms of removal rates of several contaminants, toxicity reduction or amelioration of physical and chemical properties. Hence, it is imperative to develop new and innovative methodologies for industrial wastewater treatment. In this context nanotechnology arises announcing the offer of new possibilities for the treatment of wastewaters mainly based on the enhanced physical and chemical proprieties of nanomaterials (NMs), which can remarkably increase their adsorption and oxidation potential. Although applications of NMs may bring benefits, their widespread use will also contribute for their introduction into the environment and concerns have been raised about the intentional use of these materials. Further, the same properties that make NMs so appealing can also be responsible for producing ecotoxicological effects. In a first stage, with the objective of selecting NMs for the treatment of organic and inorganic effluents we first assessed the potential toxicity of nanoparticles of nickel oxide (NiO) with two different sizes (100 and 10-20 nm), titanium dioxide (TiO2, < 25 nm) and iron oxide (Fe2O3, ≈ 85x425 nm). The ecotoxicological assessment was performed with a battery of assays using aquatic organisms from different trophic levels. Since TiO2 and Fe2O3 were the NMs that presented lower risks to the aquatic systems, they were selected for the second stage of this work. Thus, the two NMs pre-selected were tested for the treatment of olive mill wastewater (OMW). They were used as catalyst in photodegradation systems (TiO2/UV, Fe2O3/UV, TiO2/H2O2/UV and Fe2O3/H2O2/UV). The treatments with TiO2 or Fe2O3 combined with H2O2 were the most efficient in ameliorating some chemical properties of the effluent. Regarding the toxicity to V. fischeri the highest reduction was recorded for the H2O2/UV system, without NMs. Afterwards a sequential treatment using photocatalytic oxidation with NMs and degradation with white-rot fungi was applied to OMW. This new approach increased the reduction of chemical oxygen demand, phenolic content and ecotoxicity to V. fischeri. However, no reduction in color and aromatic compounds was achieved after 21 days of biological treatment. The photodegradation systems were also applied to treat the kraft pulp mill and mining effluents. For the organic effluent the combination NMs and H2O2 had the best performances in reduction the chemical parameters as well in terms of toxicity reduction. However, for the mine effluent the best (TiO2/UV and Fe2O3/UV) were only able to significantly remove three metals (Zn, Al and Cd). Nonetheless the treatments were able of reducing the toxicity of the effluent. As a final stage, the toxicity of solid wastes formed during wastewater treatment with NMs was assessed with Chironomus riparius larvae, a representative species of the sediment compartment. Certain solid wastes showed the potential to negatively affect C. riparius survival and growth, depending on the type of effluent treated. This work also brings new insights to the use of NMs for the treatment of industrial wastewaters. Although some potential applications have been announced, many evaluations have to be performed before the upscaling of the chemical treatments with NMs.