Monitoring of Persistent Organic Pollutants (POPs) in marine biota from the Catania Gulf (Sicily, Italy) and development of new sensitive analytical methods for their detection

This PhD thesis focus on the development of new analytical strategies, using either the common gas-chromatography mass spectrometry (GC-MS) methodologies and the fluorescence spectroscopy, to assess the distribution of different classes of Persistent Organic Pollutants (POPs), including polychlorinated biphenyls (PCBs), organochlorine pesticides (POCs), and polycyclic aromatic hydrocarbons (PAHs), in environmental matrices (biota, volcanic ashes and seawater), as well as on the monitoring of these pollutants in Mullus Surmuletus of the Catania Gulf (Sicily, Italy) and on the evaluation of the potential human health risks associated to the consumption of fish. As concerns the development of more sensitive analytical methods to detect POPs in fish muscle using GC-MS, after preliminary investigations on different extraction and clean-up techniques to remove potential interferences, a modified QuEChERS extraction and GC-MS methodologies were developed and implemented for the quantification of 16 priority PAHs, 29 PCB and 23 OCPs in muscle fish and the developed methods were validated according to UNI ENI ISO 17025. The methods for PAHs and PCBs show good linearity and optimal recoveries for almost all analytes, as well as satisfactory accuracy, yielding percent deviations within the range 100 ± 15%. All experimental CV% were lower than 15% for PAHs and PCBs, proving that the methods have good within-run precisions. On the other hand, since the quantification of OCPs was carried out without IS, only recoveries were tested, and this method was used only with external calibration and mainly for qualitative purposes. The developed methods were used to assess the distribution of POPs in Mullus Surmuletus from Catania Gulf (Sicily), as well as the potential human health risks associated to the consumption of fish. The determined PAHs concentration values ranged from 0.25 to 6.10 ng/g wet weight, whereas for the other classes of pollutants some PCBs (PCB 028, PCB 138 and PCB 153) and only the pesticides 4,4′-DDE were detected in trace. The most abundant PAHs detected were lower molecular weight (LMW) compounds with 2 to 3 rings. Relying on the PAHs concentration values, on the consumption data and on the total Toxic Equivalent (TEQ), the incremental lifetime cancer risk (ILCR) was assessed and its calculated value (2.97×10-7) is far below the “maximum acceptable risk level” (ARL), suggesting a low potential carcinogenic risk on consuming M. surmuletus for local population. Even though the study shows a quite low contamination level in M. surmuletus, intensive monitoring programmes are still highly needed in order to provide a better picture of the PAHs distribution in Catania Gulf and of the human health risk linked to fish consumption. Considering the natural pressures to which the area investigated is subjected, an ultrasonic extraction followed by an SPE clean-up, and GC-MS methodology was optimized and developed to detect PAHs in Etna volcanic ashes in order to identified a potential baseline of natural sources of these pollutants and to evaluate the potential impact of volcanic eruptions to the marine environment. Experiments carried out spiking the samples with 10 µg/Kg provided recovery ranged from 70 to 120% for almost analytes. Preliminary characterization of Etna volcanic ashes, sampled at high altitude (~3000 m), showed the presence of the three- to six-ring PAHs, suggesting a mixture of petrogenic and pyrogenic sources. Considering that the data reported in literature are very few and controversial, the results obtained by this preliminary study clearly indicate the need of additional and in-depth investigations. Finally, a new method for the detection of pyrene in ultrapure water has been developed by using an aromatic anion highly fluorescent, i. e. fluorescein. Preliminary results suggest an efficient energy transfer from pyrene donor to fluorescein acceptor, which probably occurs via the stacking interactions of the two aromatic systems that result to be an important driving force in solution. In order to evaluate if the presence of a metal core could enhance this effect, novel fluorescent nanoparticles capped with fluorescein (Fluo-AgNps) were synthetized and characterized by TEM and UV-Vis spectroscopy. The efficiency of energy transfer was measured by monitoring both the quenching of the pyrene emission and the enhancement of the fluorophore emission, which is greater with the free ligand fluorescein than that observed with Fluo-AgNPs. The developed method allows to detect pyrene in aqueous solutions at ppt level, using a very simple system, without additional preconcentration of the samples, obtaining a sensitivity much better than that reported with the direct fluorescence methods. The method for the quantitative determination of pyrene in seawater is still ongoing and the preliminary data showed that a pre-treatment of the seawater sample is required to remove potential interferences and to optimize the efficiency of the transfer. The data here reported are preliminary and further investigations, among which fluorescence lifetime measurements and thermodynamic investigations in order to assess the nature and the entity of the non-covalent binding are highly needed.