Seasonal and spatial variations of magnetic susceptibility and potentially toxic elements (PTEs) in road dusts of Thessaloniki city, Greece: A one-year monitoring period.

A one-year sampling campaign of road dusts was carried out at 10 distinct sites in the broader area of the city of Thessaloniki, Greece and concentrations of heavy metals (HMs) along with magnetic susceptibility were evaluated. The concentrations of HMs in road dusts were higher than their local background values, while magnetic parameters indicated a significant anthropogenic load. Principal component analysis (PCA) identified non-exhaust vehicular emissions, oil/fuel combustion and industrial activities as major sources of heavy metals accounted for approximately 73% of the total variance. A significant seasonal variability for Cr, Cu, Mn, and χlf was observed with constantly higher values during summer. Moreover, variations among urban and industrial sites were more pronounced for Cr, Cu, Zn, and χlf, while they displayed insignificant variations across all urban sites. On the contrary, concentration peaks in the urban cluster were observed for Cd, Mn, and Ni coinciding with the port area. Based on multiple pollution indices, a severe polluted area was revealed, while potential ecological risk index (RI) indicated a high potential ecological risk with Cd being regarded as the pollutant of high concern. The health risk assessment model indicated ingestion as the major exposure pathway. For both adults and children, Cr and Pb had the highest risk values, mainly recorded in the urban cluster underscoring the need of potential measures to reduce road dust in urban environments.

Pesticide residues in fruit samples: comparison of different QuEChERS methods using liquid chromatography-tandem mass spectrometry.

Acetate- and citrate-buffered quick, easy, cheap, effective, rugged, safe (QuEChERS) pretreatment methods were evaluated for the determination of various pesticides in peaches, grapes, apples, bananas, pears, and strawberries from various regions of Greece, using LC-MS/MS. The purposes of this study were (i) to evaluate which type of QuEChERS method was the most appropriate and effective for each matrix; (ii) to apply the selected QuEChERS method for each matrix, in order to detect and quantify pesticide residues in various fruit samples using UPLC-MS/MS; (iii) to examine the concentration distribution of pesticide classes among fruit originating from various areas; and (iv) to assess pesticide concentration distribution between peel and flesh of fruit in order to evaluate the penetration of pesticide residues in the fruit flesh. Acetate-buffered QuEChERS was found to be the most suitable technique for most of the fruit matrices. According to the recovery values at two different concentration levels, peaches should preferably be treated by the citrate-buffered type, whereas grapes, bananas, apples, pears, and strawberries are best treated by the acetate-buffered version, although the differences in efficiency were small. The addition of graphitized carbon black significantly decreases the recovery of specific pesticides in all matrices except for strawberries. The majority of values do not exceed the official maximum residue levels set by the European Commission. Organophosphates proved to be the most commonly detected category along with triazines-triazoles-conazoles group and by carbamates. Apples and pears seem to be the most contaminated fruit matrices among those tested. Distribution of pesticide classes shows variations between different regions, suggesting different pesticide application practices. In the case of peaches and pears, there is an equal distribution of detected pesticides between peel and flesh, indicating penetration of contaminants into the fruit flesh.

Photocatalytic degradation of molinate in aqueous solutions.

In this study, the degradation of molinate through heterogeneous photocatalysis, using two different types of the semiconductor TiO2 as photocatalyst, as well as through homogeneous treatment, applying the photo-Fenton reaction, has been investigated. As far as heterogeneous photocatalysis is concerned, the degradation of the pesticide follows apparent first-order kinetics, while the type of the catalyst and the pH value of the solution affect the degradation rate. The effect of the addition of electron scavengers (H2O2 and K2S2O8) was also studied. In the case of photo-Fenton-assisted system, the degradation also follows pseudo-first-order kinetics. Parameters such as iron's and electron scavenger's concentration and inorganic ions strongly affect the degradation rate. The extent of pesticide mineralization was investigated using dissolved organic carbon (DOC) measurements. The toxicity of the treated solution was evaluated using the Microtox test based on the luminescent bacteria Vibrio fischeri. The detoxification and mineralization efficiency was found to be dependent on the system studied, and although it did not follow the rate of pesticide disappearance, it took place in considerable extent. The study of the photodegradation treatment was completed by the determination of the intermediate by-products formed during the process, which was carried out using LC-MS/MS technique and led to similar compounds with both processes.

Photo-Fenton decomposition of ß-blockers atenolol and metoprolol; study and optimization of system parameters and identification of intermediates.

Active pharmaceutical compounds reach the wastewater treatment plants mainly through excretion and improper disposal, and, because of insufficient treating methods, they end up to surface water or even potable water in some cases. Atenolol and metoprolol are ß-blockers, members of cardiovascular pharmaceuticals group. They are generally used in the treatment of disorders such as hypertension, angina and arrhythmias. They have been in long-term use in Europe and North America, and they have also been detected in the aquatic environment. In this study the degradation of atenolol and metoprolol in aqueous solutions by means of the photo-Fenton reaction was investigated. The purpose of this study was: (i) to investigate the influence of the concentrations of iron and hydrogen peroxide, by means of central composite design, (ii) to study the degradation kinetics in aqueous solutions, (iii) to evaluate the mineralization and the toxicity evolution of the target compounds and (iv) to identify the degradation products. It has been found that increase of iron and hydrogen peroxide concentration accelerate the degradation of atenolol and metoprolol, while the kinetics of the process can be characterized as pseudo-first order. In general the photo-Fenton method has proved to be effective in decomposing and mineralizing the target compounds. The determination of the by-products formed during the degradation using LC-MS/MS equipment and the evaluation of the toxicity of the treated solution in different stages of the process would offer significant, innovative information regarding the treatment of water and wastewater containing active pharmaceutical compounds, especially of the ß-blocker group.

Occurrence and distribution of selected heavy metals in the surface sediments of Thermaikos Gulf, N. Greece. Assessment using pollution indicators.

Forty sediment samples and fifteen water samples were collected from the Gulf of Thermaikos and the Bay of Thessaloniki in order to determine the concentration of Zn, Cu, Pb and Cr and measure various seawater parameters. The level of pollution attributed to heavy metals was evaluated using several pollution indicators in order to determine anthropogenically derived sediment contamination. Enrichment Factors, Contamination Factors, Modified Contamination Degree, and Geoaccumulation Indexes for the sediments were used to assess and visualize using GIS. Association with adverse effects to aquatic organisms was determined, using the classification of the sediments according to the Sediment Quality Guidelines (SQGs). The highest metal levels were concentrated along the shoreline of the Bay of Thessaloniki, reflecting long-term exposure to anthropogenic activities. Enrichment Factors reveal the anthropogenic sources for chromium and lead. This is supported by separate Contamination Factors, the mean Contamination Degree, and the Geoaccumulation Index. The majority of the sediment samples can be occasionally and frequently associated to toxic biological effects, according to the effect-range classification for Zn, Cu and Pb. Based on the analysis of the overlying seawater columns it appears that under the present physicochemical conditions, dissolution of the accumulated metals from the sediments is unlikely. Although the total metal content in the sediments has decreased with time, the long-term effect of the industrial and urban activities in the area is still reflected in sediments from the gulf.

Leaching of nitrogen, phosphorus, TOC and COD from the biosolids of the municipal wastewater treatment plant of Thessaloniki.

Biosolids from the WWTP of Thessaloniki were examined for the leaching of phosphorus (as PO4(3-) -P), nitrogen (as NH4+ (-N) and NO3- (-N)), and organic matter (as TOC and COD), using two tests: (1) a pH static leaching test and (2) a characterization test, relating contaminant release to the liquid to solid (L/S) ratio. Moreover, a Microtox toxicity test was conducted, to examine the pH dependency of the toxicity of the sludge leachate on the Vibrio fischeri bacterium. Maximum phosphorus release was observed at pH < 3 and at pH > 10. Ammonium nitrogen exhibited maximum leachability at near neutral pH conditions, while nitrate nitrogen exhibited a mild increase in the leachate, as the leachant pH increased from 2 to 12. Both TOC and COD exhibited an increase in the leachate concentration, as the leachant pH was increased from 2 to 12. Ecotoxicological analysis showed that maximum toxicity occurred at very low and very high pH-conditions. As liquid-to-solid ratio increased, the leachate concentration (in mg/l) of all parameters studied decreased. The results of the study were used to conduct a release assessment estimate for the case of Thessaloniki.

Heterogeneous photocatalytic degradation of prometryn in aqueous solutions under UV-Vis irradiation.

In this study, the heterogeneous photocatalytic degradation of prometryn using TiO(2) as photocatalyst was investigated. The main objectives of the study were: (I) to evaluate the kinetics of the pesticide disappearance, (II) to compare the photocatalytic efficiency of two different types of TiO(2), (III) to examine the influence of various parameters such as initial concentration of pesticide or catalyst and presence of oxidants (H(2)O(2) and K(2)S(2)O(8)), (IV) to evaluate the degree of mineralization and (V) to assess the detoxification efficiency of the studied processes. The experiments were carried out in a 500 ml pyrex UV reactor equipped with a 125 W high-pressure mercury lamp surrounded by a pyrex filter blocking wavelengths below 290 nm. Prometryn concentration was determined using HPLC. It was found that the degradation of the pesticide follows the first order kinetics according to the Langmuir-Hinshelwood model. Parameters like the type and concentration of the catalyst affect the degradation rate. A synergistic effect was observed when an oxidant was added in the TiO(2) suspensions increasing the reaction rate of photodegradation. In order to examine the extent of pesticide mineralization, DOC measurements were carried out. After 6h of illumination, mineralization was achieved up to almost 70%. The toxicity of the treated solution was evaluated using the Microtox test based on the luminescent bacteria Vibrio fisheri, in order to compare the acute toxicity of prometryn and its photoproducts. The detoxification efficiency was found to be dependent on the studied system and it did not follow the rate of pesticide disappearance.

Oxidation of two organophosphorous insecticides by the photo-assisted Fenton reaction.

The photocatalytic degradation of two selected insecticides (dimethoate and methyl parathion) has been studied using the photo-assisted Fenton reaction. The degradation kinetics were studied under different conditions such as iron's and oxidant's concentration, temperature and inorganic ions. The degradation rates proved to be strongly influenced by these parameters. The replacement of hydrogen peroxide with peroxydisulfate was also tested in a photo-Fenton-like reaction. This system achieved high degradation rates of the selected compounds. Intermediate products formed during photocatalytic treatment were identified by means of solid-phase extraction (SPE) coupled to gas chromatography-mass spectroscopy techniques (GC-MS). Eight possible by-products were identified for parathion methyl and three for dimethoate formed through mainly oxidation and dealkylation reactions. Mineralization studies showed also that the photo-Fenton and the photo-Fenton-like systems are able to achieve mineralization of the insecticides. However, complete detoxification is achieved only in the presence of the photo-Fenton reagent.

Assessment of the quality characteristics of two lakes (Koronia and Volvi) of N. Greece.

Quality parameters from 17 sampling stations from Lake Koronia and 18 from Lake Volvi were determined during sampling period of one year. Physicochemical parameters (pH, conductivity, DO) did not show remarkable differences neither between sampling sites nor between sampling periods. Nutrient concentrations (nitrogen and phosphorus compounds) were higher in lake Koronia than in Volvi showing relatively small temporal and spatial variations. As far as heavy metals in sediments, lake Koronia is considerably more polluted than Volvi lake especially with the metals Fe, Mn, Zn, Pb and Cd. The mean total concentrations of metals in lake Koronia decrease in the order Mn > Zn > Cr > Pb > Cu > Fe > Cd. The mean total concentrations of metals in lake Volvi decrease in the order Mn > Zn > Cr > Cu > Pb > Fe > Cd.

Solid phase microextraction applied to the analysis of organophosphorus insecticides in fruits.

Trace amounts of organophosphorus pesticides (OPs) were determined in various fruits by headspace solid phase microextraction (HS-SPME) and gas chromatography-nitrogen phosphorous detection (GC-NPD). Sampling from the headspace enhanced method selectivity, whereas at the same time improved fiber life time and method sensitivity. Diazinon, parathion, methyl parathion, malathion and fenithrothion were determined in various fruits: more than 150 samples of 21 types of fruits were studied. SPME-GC-NPD provided a useful and very efficient analytical tool: method linearity ranged from 1.2 to 700 ng/ml. Limits of detection (LODs) and quantitation (LOQs) ranged from 0.03 to 3 ng/ml and 0.12 to 10 ng/ml respectively, values well below the residue limits set by the EU. Less than 2% of the samples were found positive containing amounts higher than the EU limits. The effect of fruit peeling and washing was also investigated.

Study of the removal of dichlorvos and dimethoate in a titanium dioxide mediated photocatalytic process through the examination of intermediates and the reaction mechanism.

The photocatalytic oxidation of two selected organophosphorous insecticides (dichlorvos and dimethoate) has been investigated. The aim of the study was the identification of the intermediates that are formed during photocatalytic treatment. Intermediate products from the slurry system were identified by means of solid-phase extraction (SPE) coupled to gas chromatography-mass spectroscopy techniques (GC-MS). Nine possible by-products were identified for dimethoate and three for dichlorvos. A proposed degradation pathway for each insecticide is presented, involving mainly oxidation and dealkylation reactions. The results demonstrated that some of the transient intermediates formed (oxon derivatives, disulfide, chlorinated fragments), were more toxic compared to parent compounds whereas most of them are less toxic than the parent compounds.

Photocatalytic decolorization and degradation of dye solutions and wastewaters in the presence of titanium dioxide.

In this study, the photocatalytic degradation of two commercial azo dyes in the presence of TiO(2) suspensions as photocatalyst has been investigated. The degradation of the dyes follows a pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. Under the certain experimental conditions, in the presence of TiO(2) P-25 decolorization is achieved within 100 min of illumination, while in the presence of TiO(2) Hombikat UV-100 complete color disappearance is accomplished in less than 50 min of light exposure. The influence of various parameters, such as the type and mass of the catalyst, the initial concentration of the dye, etc. on the degradation process was examined. The mineralization of organic carbon was also evaluated by measuring the dissolved organic carbon (DOC) of the dye solutions. Moreover, the toxic properties of the dye solutions treated by photocatalysis were examined by the use of a Microtox bioassay (Vibrio fischeri). Finally, experiments using real textile wastewater were also carried out, in order to examine the effectiveness of the method to a more complex substrate.

Sequential fractionation of phosphorus in lake sediments of Northern Greece.

The amounts and forms of potentially mobile P in surface sediments from two lakes, Volvi and Koronia, located in Northern Greece were evaluated using a sequential chemical extraction. Five sedimentary P reservoirs were separately quantified: loosely sorbed P (NH4Cl-P); iron associated P (BD-P); calcium bound P (HCl-P); metal oxide bound P (NaOH-P) and residual P (organic and refractory P). Samples were taken in two seasons and the average concentration of the fractions of phosphorus were calculated. The results indicated that the TP content and chemically extractable phosphorus in the sediments of Koronia Lake were higher than those of Volvi Lake. Sediment TP was also strongly and positively correlated with sediment Fe. Fine-sized sediments exhibited significantly higher concentrations for both lakes than the sand fraction. The P in the surface sediment mainly consisted of HCl-P and Res-P, while NH4Cl-P and BD-P only constituted a minor part. The rank order of the different P extracts was the same for the two lakes and was Residual-P > HCl-P > NaOH-P > BD-P > NH4Cl-P.

Speciation of elements in sediment samples collected at lakes Volvi and Koronia, N. Greece.

A five-step sequential extraction procedure was applied for the determination of the distribution of seven elements (Cd, Pb, Cr, Cu, Mn, Zn, Fe) in sediment samples collected at two lakes, Volvi and Koronia, located in N. Greece. Samples were taken in two seasons, and the average concentration of the elements was calculated. The accuracy evaluated by comparing total trace metal concentrations with the sum of the five individual fractions proved to be satisfactory. Based on the results determined at one sampling point in Koronia and two sampling points along the lake Volvi, it seems that the two lakes have not yet been polluted. There were no significant changes in the individual seasonal concentrations of elements in this monitoring period. Cd, Pb, Cu and Cr are associated with the oxidizable, carbonates and residual fractions. Zn and Fe are associated with residual and reducible fractions. The metals that we most easily extracted in the samples analysed in both lakes are Pb, Cr, Cd, Cu and also Mn in the case of Koronia lake.

Photodegradation of triazine herbicides in aqueous solutions and natural waters.

The photodegradation of three triazines, atrazine, simazine, and prometryn, in aqueous solutions and natural waters using UV radiation (lambda > 290 nm) has been studied. Experimental results showed that the dark reactions were negligible. The rate of photodecomposition in aqueous solutions depends on the nature of the triazines and follows first-order kinetics. In the case of the use of hydrogen peroxide and UV radiation, a synergistic effect was observed. The number of photodegradation products detected, using FIA/MS and FIA/MS/MS techniques, suggests the existence of various degradation routes resulting in complex and interconnected pathways.

Speciation analysis of heavy metals in natural waters: a review.

Metal speciation in natural waters is of increasing interest and importance because toxicity, bioavailability, environmental mobility, biogeochemical behavior, and potential risk in general are strongly dependent on the chemical species of metals. This paper provides an overview of the need for speciation of heavy metals in natural waters, the chemical and toxicological aspects of speciation, and the analytical procedures for separation and the different techniques for final determination that are used today. The trends and developments of speciation are also discussed. Finally, the case of chromium (Cr) was selected for a detailed presentation because the speciation of this metal has attracted a great deal of interest in view of the toxic properties of Cr(VI).

Sorption-desorption behaviour of 2,4-dichlorophenol by marine sediments.

Batch kinetic and isotherm experiments were conducted to determine the sorption-desorption behavior of 2,4-dichlorophenol from seawater solutions by marine sediments containing various amounts of organic carbon (from 1.02% to 12.72% dry weight). The results indicated linear type isotherms for sorption and desorption in all marine sediments studied. The observed difference in linear sorption coefficients between sorption and desorption was indicative of sorption hysteresis. The kinetic experiments showed that equilibrium was established in less than 20 h. The study is significant with respect to sediment remediation in contaminated harbors and coastal areas.