Biomedical subjects

Triantafyllos A Albanis

Publications and source records attributed to Triantafyllos A Albanis.

25 records · Page 2Linked to original sources

PubMed2002

Adsorption-desorption studies of alachlor, metolachlor, EPTC, chlorothalonil and pirimiphos-methyl in contrasting soils.

Five soils with different organic matter contents ranging from 0.48 to 10.4% were used to study the adsorption and desorption of alachlor, metolachor, EPTC, chlorothalonil and pirimiphos-methyl in batch experiments. The isotherm shapes according to Giles classification were S-type for alachlor, metolachlor and chlorothalonil, changing to L-type for the latter as the level of soil organic matter increased, and L-type for EPTC and pirimiphos-methyl. The adsorption isotherms fitted the Freundlich equation x/m = KfCe1/n. The Kf values increased with the increase of organic matter content. The amounts of pesticides adsorbed over a range of concentrations of 0.1-20 mg litre-1 reached 63.1% for alachlor, 69.2% for metolachlor, 89.3% for EPTC, 98.4% for chlorothalonil and 96.3% for pirimiphos-methyl. The increase of the amounts desorbed with acetone indicated that the sorption of organic compounds onto organic matter occurred principally via weak London-type induction forces, or dispersion forces which are characteristics of the physical adsorption process.

Acetamides↗

PubMed2002

Pirimiphos-methyl and benalaxyl losses in surface runoff from plots cultivated with potatoes.

Abstract: Losses of pirimiphos-methyl and benalaxyl in runoff water from clay soil plots cultivated with potatoes and of differing soil surface slopes were determined over approximately 120 days (1 October 1999-28 January 2000). The plot slopes were 0, 1, 2.5 and 5%, and soil erosion increased with the slope from 610 to 1760kgha(-1). The runoff of surface water was between 3.1 and 16.6% of the rainfall. Surface runoff was highest for the fifth and seventh runoff events due to rainfall, 51 days and 72 days after the first pesticide application. The maximum concentrations of the two pesticides in runoff occurred in the plots with the greatest slope (5%) during the fifth runoff event, November 21, 1999 reaching 8.4 and 12.3 microg litre(-1) for pirimiphos-methyl and 17.8 and 20.2 microg litre(-1) for benalaxyl in tilled and untilled plots respectively. The cumulative losses of pirimiphos-methyl in surface runoff from tilled and untilled plots with a slope 5% were estimated at only 0.37 and 0.59% of the initial applied active ingredient, respectively, while for plots with a slope 0% the percentages were 0.013 and 0.018%. For benalaxyl the corresponding values from tilled and untilled plots were 1.69 and 1.76% (slope 5%), and 0.062 and 0.085 (slope 0%). Degradation of the pesticides in the topsoil was monitored from October 1999 and May 2000. Cultivation of potatoes decreased the half-life of the two pesticides compared to the untilled fields, for pirimiphos-methyl from 16.7 to 9.2 days and for benalaxyl from 26.7 to 12.6 days. The slope of soil surface and the different sorption capacities for the compounds are the main parameters which influenced the transportation of studied pesticides, pirimiphos-methyl and benalaxyl residues via surface water in soil-water systems.

Adsorption↗

PubMed2002

Survey for the occurrence of antifouling paint booster biocides in the aquatic environment of Greece.

Since the restriction imposed by European Union regulations on the use of TBT-based antifouling paints on boats below 25 m in length, new terms have been introduced in the 'small boat' market. Replacement products are generally based on copper metal oxides and organic biocides. Several studies have demonstrated the presence of these biocides in European ports and marinas of Spain, France, Germany and the United Kingdom. An extended survey of the antifouling biocides chlorothalonil, dichlofluanid, irgarol 1051 and sea-nine 211 was carried out in Greek ports and marinas of high boating activities from October 1999 to September 2000. The sampling sites were: Piraeus, Elefsina, Thessaloniki, Patras, Chalkida, Igoumenitsa, and Preveza (Aktio). The extraction of these compounds from the seawater samples was performed off-line with C18 solid phase extraction (SPE) disks while the determination was carried out with gas chromatography coupled to electron capture (ECD), thermionic (FTD) and mass spectroscopy (MS) detectors. The concentration levels of biocides were higher during the period from April to October. This seasonal impact depends on the application time of antifouling paints and mimic trends in the seasonal distribution of biocides in other European sites.

Environmental Monitoring↗

PubMed2002

Photocatalytic degradation of propachlor in aqueous TiO2 suspensions. Determination of the reaction pathway and identification of intermediate products by various analytical methods.

The light-induced degradation of propachlor (2-chloro-N-isopropylacetanilide) under simulated solar irradiation has been investigated in aqueous solutions containing TiO2 suspensions as photocatalysts. The study focuses on the identification of possible intermediate products and the determination of inorganic ions formed during the process, using several powerful analytical techniques such as gas chromatography mass-spectrometry (GC-MS) and ion chromatography. The primary degradation of propachlor has been a fast process with a half-live time of 2.3 min and followed pseudo-first-order kinetics according to the Langmuir-Hinshelwood model. The mineralization of the organic carbon to CO2 after 240 min of irradiation was found to be < 63%. The corresponding stoichiometric transformation of organic chlorine into chloride ion was reached in 30 min, whereas oxidation of nitrogen to nitrate ions took place at delayed irradiation times. Various aromatic intermediates have been identified by GC/MS techniques during the treatment, which were involved into three tentative degradation routes. One, was based on the dechlorination through positive holes or solvated electrons to form the hydroxy or aliphatic derivative. The second route consists of the rupture of amide bond or the N-C bond via nitrogen ionization by positive holes and through the ring hydroxylation, respectively. Finally, the third possible degradation route was based on hydrogen abstraction by the hydroxyl radicals or positive holes, followed either by the addition of oxygen to the alkyl radical or the decomposition of the peroxyl radical formed. From the analytical data, a possible multi-step degradation scheme was proposed. This work points to the necessity of extended knowledge of the successive steps in a solar-assisted detoxification process.

Acetanilides↗

PubMed2002

Study of chlorothalonil photodegradation in natural waters and in the presence of humic substances.

Photodegradation of chlorothalonil was studied in different natural waters (sea, river and lake) as well as in distilled water under natural and simulated solar irradiation. The effect of dissolved organic matter (DOM) such as humic and fulvic substances on the photodegradation rate of chlorothalonil was also studied in simulated sunlight. The presence of DOM enhanced the photodegradation of chlorothalonil with the exception of seawater. The kinetics were determined through gas chromatography electron capture detection (GC/ECD) and the photodegradation proceeds via pseudo-first-order reaction in all cases. Half-life ranged from 1 to 48 h. In natural and humic water chlorothalonil photodegradation gave rise to two different intermediates compared to distilled water demonstrating that the transformation of chlorothalonil depend on the constitution of the irradiated media and especially from DOM. The byproducts identified by GC/MS techniques were: chloro-1,3-dicyanobenzene, dichloro-1,3-dicyanobenzene, trichloro-1,3-dicyanobenzene and benzamide.

Fungicides, Industrial↗

PubMedDate not supplied

Surface retention and photochemical reactivity of the diphenylether herbicide oxyfluorfen.

The photochemical behavior of oxyfluorfen [2-chloro-1-(3-etoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] on two Greek soils was investigated. Soils were sampled from Nea Malgara and Preveza regions, characterized by a different organic matter content. Soils were spiked with the diphenyl-ether herbicide and irradiation experiments were performed either in the laboratory with a solar simulator (xenon lamp) or outside, under natural sunlight irradiation; other soil samples were kept in the dark to control the retention reaction. Kinetic parameters of both retention and photochemical reactions were calculated using zero-, first- and second- (Langmuir-Hinshelwood) order equations, and best fit was checked through statistical analysis. The soil behaviors were qualitatively similar but quantitatively different, with the soil sampled from the Nea Malgara region much more sorbent as compared with Preveza soil. All studied reactions followed second-order kinetics and photochemical reactions were influenced by retaining capability of the soils. The contributions of the photochemical processes to the global dissipation rates were also calculated. Two main metabolites were identified as 2-chloro-1-(3-ethoxy-4-hydroxyphenoxy)-4-(trifluoromethyl)benzene and 2-chloro-1- (3-hydroxy-4-nitrophenoxy)-4-(trifluoromethyl)benzene.

Environmental Monitoring↗

PubMedDate not supplied

Factors affecting multiresidue determination of priority herbicides when using solid-phase microextraction.

A solid-phase microextraction (SPME) procedure was developed for the determination of 10 selected organonitrogen herbicides (s-ethyl dibropylthiocarbamate [EPTC], molinate, propachlor, trifluralin, simazine, atrazine, propazine, terbuthylazine, alachlor, and prometryn) and was tested with various natural waters. Gas chromatography coupled with flame thermionic and mass spectrometric detection was used for quantitation. For this purpose, polydimethylsiloxane and polyacrylate fibers were used and the factors affecting the SPME process such as pH, ionic strength, methanol content, memory effect, stirring rate, and adsorption-time profile were investigated and optimized. By using spiked liquid chromatography water, optimal factors were determined to be 25% salt, <0.5% methanol, stirring rate of 960 rpm, pH 4, and an equilibrium time of 30 min. These conditions were used in further studies of the fibers and in analysis of natural water samples. The method was applied to spiked natural waters such as ground water, sea water, lake water, and river water at a concentration range of 0.5-10 microg/L. Limits of detection ranged from 5 to 90 ng/L, and precision ranged from 5 to 15% (as relative standard deviation), depending on the pesticide, fiber, and detector used. The recoveries of herbicides were 70.2-118.4%, and the average r2 values of the calibration curves were >0.99 for all analytes. The results demonstrate the suitability of the SPME method to determine these organonitrogen herbicides in various natural waters. River water samples originating from the Epirus region (Northwestern Greece) were analyzed to verify the performance of the optimized method by comparing the results obtained by SPME with those obtained by using conventional solid-phase extraction of the selected herbicides.

Calibration↗