Triantafyllos A. Albanis

Photocatalytic transformation of pesticides in aqueous titanium dioxide suspensions using artificial and solar light: intermediates and degradation pathways

It has been shown that a wide range of organic compounds in aqueous solutions is photocatalytically oxidized to carbon dioxide in the presence of titanium dioxide with artificial and solar light. The photocatalytic mineralization of the most important classes of pesticides in water by illuminated TiO2 has been reviewed. The study focuses on the determination of the nature of the principal organic intermediates and the evolution of the mineralization as well as on the degradation pathways followed during the process. The photocatalyzed degradation of pesticides does not occur instantaneously to form carbon dioxide, but through the formation of long-lived intermediate species. Their detection and identification are required in order to determine which kind of chemical structures are left at the end of the process. Various analytical techniques such as liquid–liquid extraction and solid phase extraction followed by gas chromatography-mass spectrometry (GC–MS), liquid chromatography–mass spectrometry (LC–MS) or 1 H-NMR were used for the determination of organic intermediates. Gas chromatography, ion chromatography, spectrophotometry, titration and other techniques were used for the monitoring of the so-called end-products such as CO2 ,C l − ,S O 4 2− ,N H 4 + ,N O 3 − , etc. The main intermediates of pesticide degradation are of five types: (a) hydroxylated products and derivatives usually after dehalogenation of the parent pesticide, if halogen substituents are present (b) products of oxidation of the side chain, if present (c) ring opening products for aromatic pesticides (d) decarboxylation products and (e) isomerization and cyclization products. The identification of possible formation of highly toxic compounds even at low concentrations is essential for the assessment of treated water. Therefore, toxicity tests for the irradiated samples are also important to be conducted in combination with the identification of the intermediates.

Investigation of PPCPs in wastewater treatment plants in Greece: Occurrence, removal and environmental risk assessment

In the present work, an extensive study on the presence of eighteen pharmaceuticals and personal care products (PPCPs) in eight wastewater treatment plants (WWTPs) of Greece has been conducted. The study covered four sampling periods over 1-year, where samples (influents; effluents) from eight WWTPs of various cities in Greece were taken. All WWTPs investigated are equipped with conventional activated sludge treatment. A common pre-concentration step based on SPE was applied, followed by LC-UV/Vis-ESI-MS. Further confirmation of positive findings was accomplished by using LC coupled to a high resolution Orbitrap mass spectrometer. The results showed the occurrence of all target compounds in the wastewater samples with concentrations up to 96.65 μg/L. Paracetamol, caffeine, trimethoprim, sulfamethoxazole, carbamazepine, diclofenac and salicylic acid were the dominant compounds, while tolfenamic acid, fenofibrate and simvastatin were the less frequently detected compounds with concentrations in effluents below the LOQ. The removal efficiencies showed that many WWTPs were unable to effectively remove most of the PPCPs investigated. Finally, the study provides an assessment of the environmental risk posed by their presence in wastewaters by means of the risk quotient (RQ). RQs were more than unity for various compounds in the effluents expressing possible threat for the aquatic environment. Triclosan was found to be the most critical compound in terms of contribution and environmental risk, concluding that it should be seriously considered as a candidate for regulatory monitoring and prioritization on a European scale on the basis of realistic PNECs. The results of the extensive monitoring study contributed to a better insight on PPCPs in Greece and their presence in influent and effluent wastewaters. Furthermore, the unequivocal identification of two transformation products of trimethoprim in real wastewaters by using the advantages of the LTQ Orbitrap capabilities provides information that should be taken into consideration in future PPCP monitoring studies in wastewaters.

Photocatalytic degradation using design of experiments: A review and example of the Congo red degradation

The use of chemometric methods such as response surface methodology (RSM) based on statistical design of experiments (DOEs) is becoming increasingly widespread in several sciences such as analytical chemistry, engineering and environmental chemistry. Applied catalysis, is certainly not the exception. It is clear that photocatalytic processes mated with chemometric experimental design play a crucial role in the ability of reaching the optimum of the catalytic reactions. The present article reviews the major applications of RSM in modern experimental design combined with photocatalytic degradation processes. Moreover, the theoretical principles and designs that enable to obtain a polynomial regression equation, which expresses the influence of process parameters on the response are thoroughly discussed. An original experimental work, the photocatalytic degradation of the dye Congo red (CR) using TiO(2) suspensions and H(2)O(2), in natural surface water (river water) is comprehensively described as a case study, in order to provide sufficient guidelines to deal with this subject, in a rational and integrated way.

Herbicide contamination of Mediterranean estuarine waters: Results from a MED POL pilot survey☆

Abstract The reported data offers the first extensive evidence that significant concentrations of some herbicides persist in marine systems. In the areas studied (the Ebro delta on the Eastern Coast of Spain, the Rhone delta in the South of France, the River Po, Italy/the Northern Adriatic Sea, the Thermaikos and Amvrakikos Gulfs in Greece and the Nile delta in Egypt) the most commonly encountered herbicides were atrazine, simazine, alachlor, metolachlor and molinate. In general, aqueous concentrations encountered in the riverine inputs were comparable to (or below) those reported for rivers in other regions of the World. Concentrations generally declined from freshwater locations through estuaries to marine waters. The distributions of some herbicides (e.g. the triazines) in sediments endorsed the environmental persistence of these compounds. In contrast to the other areas studied, no herbicides were detected in samples from a preliminary survey of the Nile delta.

Polycyclic aromatic hydrocarbons in the bulk precipitation and surface waters of Northern Greece

Bulk (wet and dry) precipitation and surface water sampling was undertaken in the main plain of central Macedonia in Northern Greece. Fourteen polycyclic aromatic hydrocarbons (PAHs) included in the US EPAs priority pollutant list were analysed. The concentrations determined in bulk precipitation were in general within the range of values worldwide reported. Concentrations were highest in the cold months. Deposition fluxes of PAHs were of the same order of magnitude as reported data. The greatest values were found when high concentrations of PAHs in precipitation coincided with large precipitation amounts. The concentrations of PAHs in surface waters (main rivers, tributaries, ditches, etc) were in general lower than those in bulk precipitation, and among the lowest reported for European rivers, excepting Np and Ph. Bulk deposition and domestic effluents are suggested as being the main PAH sources into surface waters.

Occurrence and removal of PPCPs in municipal and hospital wastewaters in Greece

A monitoring study was carried out for the four seasons over 1-year monitoring period (March 2006-March 2007) to investigate the residues of 11 pharmaceuticals and personal care products (PPCPs) belonging to various therapeutic categories. The selected areas of the study were the municipal and hospital wastewater treatment plants (WWTPs) of Ioannina city, located in Western Greece. The most common pre-treatment technique for pharmaceuticals, solid-phase extraction (SPE), was used for the isolation and pre-concentration of the target analytes. The samples were screened using gas chromatography mass spectrometry (GC-MS). The results of the monitoring study, showed the occurrence of all target compounds in the wastewater samples. Concentrations in the municipal WWTP ranged between 0.3 and 164.4 microg/L in the influent and between 0.5 and 13.9 microg/L in the effluent. In the hospital WWTP concentrations ranged between 0.6 and 70.1 microg/L in the influent and between 0.5 and 14.6 microg/L in the effluent. Mean removal efficiencies ranged between 13% and 97% and between 9% and 87% for municipal and hospital WWTPs, respectively. Removal efficiencies were higher in the municipal WWTP than in the hospital WWTP.

Developments on chemometric approaches to optimize and evaluate microextraction

Chemometric experimental design in microextraction plays a crucial role in sustaining the highest quality of analytical data. Making use of the main significant points of chemometric experimental design and microextraction in analytical chemistry we formed the core of this review article. A step-by-step chemometric approach is provided to optimize and validate microextraction-based analytical processes. Significant applications are reported with developments related to microextraction combined with chemometric optimization processes. As it appears from the numerous examples provided in this review, a great number of researchers give credit to the combination of microextraction and chemometrics recognizing that it significantly streamlines sample processing. Moreover, the combination of microextraction with chemometrics addresses problems relating to improvement in detectability and method validation. A worked example on the microextraction of polychlorinated biphenyls is incorporated into the relevant sections of this article and comprehensively provides in a rational and integrated way guidance to people dealing with this subject.

Optimization of headspace solid-phase microextraction conditions for the determination of organophosphorus insecticides in natural waters

Headspace solid-phase microextraction (HS-SPME) has been developed for the analysis of seven organophosphorus insecticides, i.e. diazinon, fenitrothion, fenthion, ethyl parathion, methyl bromophos, ethyl bromophos and ethion in natural waters. Their determination was carried out using gas chromatography with flame thermionic and mass spectrometric detection. To perform the HS-SPME, two types of fibre have been assayed and compared: polyacrylate (PA 85 microm), and polydimethylsiloxane (PDMS 100 microm). The main parameters affecting the HS-SPME process such as temperature, salt additives, memory effect, stirring rate and adsorption-time profile were studied. The method was developed using spiked natural waters such as ground, sea, river and lake water in a concentration range of 0.05-1 microg/l. The HS-SPME conditions were optimized in order to obtain the maximum sensitivity. Detection limits varied from 0.01 to 0.04 microg/l and relative standard deviations (RSD <17%) were obtained showing that the precision of the method is reliable. The method showed also good linearity for the tested concentration range with regression coefficients ranging between 0.985 and 0.999. Recoveries were in relatively high levels for all the analytes and ranged from 80 to 120%. Water samples collected from different stations along the flow of Kalamas river (NW Greece) were analyzed using the optimized conditions in order to evaluate the potential of the proposed method to the trace-level screening determination of organophosphorus insecticides. The analysis with HS-SPME has less background interference and the advantage of its non-destructive nature reveal the possibility of the repetitive use of the SPME fibre.

Removal of chlorinated phenols from aqueous solutions by adsorption on alumina pillared clays and mesoporous alumina aluminum phosphates

Abstract Alumina pillared montmorillonite (AIPMt) and mesoporous alumina aluminum phosphates (AAPs) were contacted with aqueous, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol solutions, at a concentration range between 25 and 250 μg/litre, in batch equilibrium experiments, in order to determine their adsorption properties. The removal of chlorophenols by the adsorbents increase with increasing chlorine substitution in their molecules. In the case of pentachlorophenol, the increased affinity allows adsorption to occur much more efficiently than in the case of other compounds. AIPMt material adsorbs 26.3% of 2,4-dichlorophenol, 75.6% of 2,4,6-trichlorophenol and 95.2% of pentachlorophenol at equilibrium. The adsorption of chlorophenols on mesoporous AAPs is much less pronounced as compared to clays but increases with the ratio of P Al , as the surface acidity of those solids also increases. The AAP mixture with a ratio P Al = 0.6 adsorbs 14.8% of 2,4-dichlorophenol, 27.1% of 2,4,6-trichlorophenol and 58.3% of pentachlorophenol. The amounts of chlorophenols decomposed during the treatment increase in AAPs and especially in those with a higher P Al ratio (=0.6).

Environmental monitoring and ecological risk assessment for pesticide contamination and effects in Lake Pamvotis, northwestern Greece

Monitoring of pesticide residues in water and sediments was conducted as a basis for subsequent ecotoxicological risk assessment for the shallow eutrophic Lake Pamvotis, northwestern Greece. During a one-year study period, atrazine, desethylatrazine (DEA), simazine, diazinon, malathion, oxamyl, carbofuran, and ethion were detected in water and atrazine, desethylatrazine, diazinon, and s-ethyl dipropylthiocarbamate (EPTC) in sediments, all at ppb concentration level. Temporal variation in pesticide concentrations was observed. Highest residue levels for most pesticides in both water and sediment matrices occurred in the May to July period with the exception of atrazine and DEA, which show highest levels in water during the September to November period. The ecological risk associated with pesticide contamination was assessed using two different methods: The toxic unit method, which provides a first indication of the relative contribution of detected pesticides to the total toxicity and a probabilistic approach, and the inverse method of Van Straalen and Denneman, which is used to quantify the ecological risk. The maximum percentage of the ecological risk was 10.3 and 51.8% for water and 17.2 and 70.6% for sediment, based on acute and chronic level, respectively. These results show that pesticides exert a significant pressure on the aquatic system of Lake Pamvotis, especially for the chronic-effect level. Simple quotient methods should be coupled with higher-tier risk assessment, especially if restoration activities on lake ecosystems are to be undertaken for sustainable development.