Computer simulations in modeling interfacial phenomena : from polymer solutions to the troposphere =

Ce travail a pour objectif de montrer la capacité des simulations numériques à modéliser les phénomènes aux interfaces solides et liquides. Dans le travail sur les interfaces solides, la méthode GCMC a été utilisée pour simuler l'isotherme d'adsorption de !'acétaldéhyde sur la glace dans les conditions de la haute troposphère, puis l'adsorption de composés organiques bi-fonctionnalisés sur la glace a été caractérisée par dynamique moléculaire avec pour objectif d'interpréter des résl1ltats expérimentaux de la littérature. Une partie de ce travail a été consacrée à la circulation du diagramme de phase (p,T) d'aérosols organiques (acide oxalique et malonique) clans les conditions troposphériques afin d'étudier la capacité de ces aérosols à jouer le rôle de noyaux de condensation pour les particules de glace. Le travail sur les interfaces liquides a concerné tout d'abord l'adsorption compétitive de polymères et de smfactants à la surface de l'eau. Il s'appuie sur une description très précise, par simulation, de la structure et de la dynamique de la surface des systèmes considérés. La deuxième partie des travaux sur les interfaces liquides s'est intéressée à la caractérisation du transfert d'ions à travers une interface liquide/liquide par le biais du calcul des variations de l'énergie libre du système au cours du transfc1i. Afin d'obtenir une description très rigoureuse des détails des processus mis enjeu, une méthode spécifique a été développée dans cette thèse pour calculer le profil d'énergie libre en tenant compte directement du caractère très dynamique de l'interface.This work aims to demonstrate the ability of numerical simulations to mode] solid · and liquid interfaces. In the work on the solid interfaces, the GCMC method was used to sin:rnlatc the ads011Jtion isotherrn of acetaldehyde on ice under the conditions of the ·upper tropospherc and the molecular dynamics method was usecl to characterize the adsorption of difünctionalized organic compounds on ice, aiming at interpreting experimental results. Part of this work was devotcd to the simulation of the phase diagrarn (p, T) of organic aerosols (oxalic acid and malonic) in tropospberic conditions to study the ability of aerosols to act as condensation nuclei for icc particlcs. The work: on liquid interfaces concerned firstly the competitive adsorption of polymcrs and surfactants at the water surface. It is based on a very precise desc1iption, by mnncrical simulation, of the structure émd dynamics cif the surface of the considered systems. The second pari of the work on liquid interfaces bas focused on the characterization of ion transfer across a liquid/liquid interface through the calculations of the free energy variations of the system during the transfo·. To obtain a rigorous desc1iptio11 of the details of the corresponding processes, a specific method was developed in this thesis to calculate the free energy profile while taking into account tbe dynamics of the interface

Determination of DDT and its metabolites in soil, tree bark and earthworm samples near the Budapest chemical works

An abandoned industrial site of the former Budapest Chemical Works (BVM) company has been found to contain 2000-3000 tonnes of leaking industrial waste and dangerous chemicals in corroded barrels on bare ground. The waste lot includes general industrial reagents and intermediates, some 100-200 tonnes of sulphuric acid, several hundred tonnes of 1.2 dichlorobenzene and isopropanol, and numerous other substances falling into toxicity categories from toxic to very toxic or carcinogenic, such as dinitrobenzoic acid, as well as chemical wastes from the pesticide production of the company. BVM used to manufacture numerous pesticide active ingredients, including chlorinated hydrocarbons. Thus, it produced the insecticide DDT in large quantities until the ban of the compound in 1968 and derogated approval for sales until 1974. The premises of the company has been reported previously to be contaminated, therefore, in the scope of our pesticide residue monitoring surveys between 2015 and 2019, we carried out sampling in its immediate vicinity. In our study, soil (8 samples), surface water (2 samples), tree bark (Robinia pseudoacacia, Sambucus nigra, Populus nigra) and common reed (Phragmites australis, (6 samples), as well as earthworms (Lumbricus terrestris; 1 sample) sampled next to BVM were analyzed for DDT and metabolite (~DDT) levels. Exceedingly high ~DDT levels above the accepted limit (0.1 mg/kg) were detected in soil samples: nearly 1.5 mg/kg in one sample and 0.11-0.484 mg/kg in other 5 cases. Among the biological samples (tree bark, common reed and earthworm) 0.184 and 0.190 mg/kg concentrations of ~DDT were determined in a black poplar and in an earthworm sample. These findings indicate that the wellknown persistency problem related to chlorinated hydrocarbon insecticides, particularly to DDT remains actual to our days

Reprint of “Role of the fluidity of a liquid phase in determining the surface properties of the opposite phase”

Molecular dynamics simulations of the water-CCl4 interface have been done in two different ways. In the first simulation the CCl4 phase has been frozen in an equilibrium configuration, and only the water molecules have been allowed to move, whilst in the other one no such artificial freezing has been done. This way the effect of the fluid-like structure and fluid-like dynamics of the CCl4 phase on the surface properties of the aqueous phase could be investigated separately. Due to the separate thermostatting of the two types of molecules in the simulations all the differences seen between the interfacial properties of water in the two systems can indeed be attributed to the rigid vs. fluid nature of the organic phase, and not to the thermal contact with a phase of zero temperature. The obtained results reveal that the rigidity of the opposite phase introduces an ordering both in the layering structure and orientation of the surface water molecules. The enhanced orientational ordering leads to a stronger lateral hydrogen bonding structure of the molecules within the subsequent molecular layers beneath the surface, and hence also to a slower exchange of the water molecules between the surface and the bulk aqueous phase

The effect of anaesthetics on the properties of a lipid membrane in the biologically relevant phase: A computer simulation study

Molecular dynamics simulations of the fully hydrated neat dipalmitoylphosphatidylcholine (DPPC) membrane as well as DPPC membranes containing four different general anaesthetic molecules, namely chloroform, halothane, diethyl ether and enflurane, have been simulated at two different pressures, i.e., at 1 bar and 1000 bar, at the temperature of 310 K. At this temperature the model used in this study is known to be in the biologically most relevant liquid crystalline (Lα) phase. To find out which properties of the membrane might possibly be related to the molecular mechanism of anaesthesia, we have been looking for properties that change in the same way in the presence of any general anaesthetic molecule, and change in the opposite way by the increase of pressure. This way, we have ruled out the density distribution of various groups along the membrane normal axis, orientation of the lipid heads and tails, self-association of the anaesthetics, as well as the local order of the lipid tails as possible molecular reasons of anaesthesia. On the other hand, we have found that the molecular surface area, and hence also the molecular volume of the membrane, is increased by the presence of any anaesthetic molecule, and decreased by the pressure, in accordance with the more than half a century old critical volume hypothesis. We have also found that anaesthetic molecules prefer two different positions along the membrane normal axis, namely the middle of the membrane and the outer edge of the hydrocarbon region, close to the polar headgroups. The increase of pressure is found to decrease the former, and increase the latter preference, and hence it might also be related to the pressure reversal of anaesthesia. © the Owner Societies 2015

Ínfű fajok és a lucerna másodlagos kémiai anyagai és hatástani vizsgálatai rovarokon = Allelochemicals from alfalfa and Ajuga plants and those of biological activity on different insect orders

Különböző Ajuga fajok teljes növényi őrleményét (Plodia interpunctella), teljes és frakcionált metanolos kivonatait (Acyrthosiphon pisum, Dysdercus cingulatus, Aedes aegypti, Daphnia magna), valamint tisztított ekdiszteroidok hatékonyságát vizsgáltuk. A Plodia-teszben az A. reptans 8 %-os dózisa azon túl, hogy kétszeresére növelte a posztembrionális kifejlődéshez szükséges időt és csökkentette a bábok súlyát - számottevő mortalitást (77 %) is okozott. Az A. aegypti esetében jelentős hatékonyságot csak az A. reptans 100%-os metanolos frakciója mutatott (0,1 %-os dózisban ~80 %-os mortalitás). A szívó szájszervű rovaroknál (A. pisum, D. cingulatus) A. chamaepitys 100%-os és az A. bracteosa 60%-os frakciói bizonyultak a leghatékonyabbak (0,1 %-os koncentrációban 100 %-os mortalitás). A tisztított ekdiszteroidok közül a 20E és a Polipodin B voltak hatékonyak a levéltetű tesztben (LC50 = 1,07 és 0,21 ppm). Az A. reptans-ból 10 különböző ekdiszteroidot (20-hidroxiekdizon, 20-hidroxiekdizon 3-acetát, ciaszteron, ciaszteron 3-acetát, 29-nor-ciaszteron, ajugaszteron B', ajugalakton, szengoszteron, 23-hidroxi-kapitaszteron, 24-etil-24,26-dihidroxi-taxiszterol 26-metilát) sikerült izolálnunk. Ezek közül két vegyület (23-hidroxi-kapitaszteron, 24-etil-24,26-dihidroxi-taxiszterol 26-metilát) új természetes ekdiszteroidnak bizonyult. Az A. reptans-ból eddig izoláltak közül a 20-hidroxiekdizon 3-acetátot és a ciaszteron 3-acetátot elsőként nyertük ki ebből az Ajuga fajból. | We studied the efficacy of whole plant grist (Plodia interpunctella), crude and fractionated methanolic extracts (Acyrthosiphon pisum, Dysdercus cingulatus, Aedes aegypti, Daphnia magna) as well as pure ecdysteroids from different Ajuga spp. In the Plodia-test the strongest effects were found at 8% concentration of A. reptans grist, which reduced the pupal weight, doubled the postembryonic developmental time, and caused 77% mortality until emergence of adults. In the Aedes-test the crude as well as the 100% methanolic fraction from A. reptans showed high efficacy (80% mortality at 0.1% concentration). In the case of sucking insect species (A. pisum, D. cingulatus) the 100% methanolic fraction of A. chamaepitys and the 60% methanolic fraction of A. bracteosa were highly effective on A. pisum (100% mortality at 0.1% concentration) Polipodine B and 20-hydroxyecdysone were the most effective pure phytoecdysteroids on aphids (LC50 = 0.21 ppm and 1.07 ppm). We have identified 10 different ecdysteroids from the Ajuga reptans var. reptans (20-hydroxyecdysone, 20-hydroxyecdysone acetate, cyasterone, cyasterone 3 acetate, 29-nor-cyasterone, ajugasterone B', ajugalactone, sengosterone, 23-hydroxi-kapitasterone, 24-ethyl-24,26-dihydroxi-taxisterol 26-metilat). Among these 23-hydroxi-capitasterone and 24-ethyl-24,26-dihydroxi-taxisterol 26-metilat are new phytoecdysteroids while, 20-hydroxyecdysone acetate and cyasterone 3 acetate were firstly isolated from A. reptans

Environmental analytical aspects of mosquito control practice

Aerial application of insecticides was monitored by determination of the active ingredient (deltamethrin) using a gas chromatograph coupled to an electron capture detector. The amount of pesticide active ingredient settled to trays after an hour indicated uneven distribution patterns influenced by micrometeorological conditions as well. Maximum half and typically about 30% of the applied insecticide settled in one hour after the treatment. Pesticide drift observed 50 meters away from the target treatment zone was significant in all cases. The measured values ranged between 7% and 31% of the applied deltamethrin and the highest value was observed for K-OTHRIN 10 ULV formulation. Parallel determination of the spray droplet size distribution and specific droplet numbers also confirmed that the drops reach the soil surface and indicated a substantial spray drift

Application rates of neonicotinoids in seed coating as sources of environmental contamination

To assess technical variability in actual dosages, the application rates of neonicotinoid insecticide active ingredients in seed coatings were determined and compared for commercial seeds of different maize varieties. Theeffect oflong storage and coating by unique equipment were assessed. Application rates in different pesticide treatment modes (seed coating, spray or soil granule applications) were also compared. Results indicate that the three technologies utilize similar amounts of the active ingredients per hectare

Study on Soil Mobility of Two Neonicotinoid Insecticides

Movement of two neonicotinoid insecticide active ingredients, clothianidin (CLO) and thiamethoxam (TMX), was investigated in different soil types (sand, clay, or loam) and in pumice. Elution profiles were determined to explore differences in binding capacity. Soil characterized by high organic matter content retained the ingredients, whereas high clay content resulted in long release of compounds. Decrease in concentration was strongly influenced by soil types: both CLO and TMX were retained in loam and clay soils and showed ready elution through sandy soil and pumice. Elution capability of the active ingredients in sandy soil correlated with their water solubility, indicating approximately 30% higher rapidity for TMX than for CLO. Soil organic carbon-water partitioning coefficients (Koc) determined were in good agreement with literature values with somewhat lower value for CLO in sandy soil and substantially higher values for TMX in clay soil. High mobility of these neonicotinoid active ingredients in given soil types urges stronger precautionary approach taken during their application

Neonicotinoid insecticide uptake by maize and appearance in guttation liquid

Movement of clothianidin (CLO) and thiamethoxam (TMX) applied as maize seed dressing or spray application has been investigated in different soil types (sandy, clay or loam), and subsequent appearance of these compounds in the guttation liquid of maize are presented. Elution profiles for different soil types were determined in order to explore differences in binding capacity. Soil characterized by high organic matter content retained the ingredients, whereas high clay content resulted in delayed release of the compounds. Neonicotinoid uptake by non-coated maize plants was also determined via guttation liquid measurements after the neonicotinoid ingredients had been applied in spray format. The highest peak concentrations of TMX and CLO (0.546 and 1.83 µg/ml, respectively) were measured from plants planted in sandy soil, but these levels were still substantially lower than levels in samples taken from plants emerged from neonicotinoid-coated seeds (above 100 µg/ml). Moreover, the time of ingredient appearance in guttation liquid was also strongly influenced by soil type. Cross-contamination was established by measuring neonicotinoid concentrations in guttation liquid in plants emerged from differently coated (CLO and TMX) seeds potted near to each other and the effect of soil type has also been explored. Results for coated (CLO or TMX) and non-coated plants also confirmed that cross-contamination may occur by uptake through soil from neighboring seeds. Differences between non-coated and coated seeds gradually disappeared. This is the first record of neonicotinoid levels in guttation liquid of plants emerged from non-coated maize seeds

Environmental monitoring of glyphosate and assessment of its combined cytotoxicity with adjuvants

Pesticide toxicology currently focuses mainly on two areas: long-term effects of given compounds and cocktail effects of chemicals, including combined effects of pesticide active ingredients with their adjuvants, as seen in the case of glyphosate-based herbicides. In this study surface water pollution in an agricultural region of Hungary by glyphosate was determined by ELISA method, and cytotoxic effects on HEK293 and NE-4C cells by glyphosate, its formulated herbicide (ROUNDUP® ) and adjuvant (polyethoxylated tallowamine, POEA) were compared. ROUNDUP and POEA were found to be equitoxic at short exposures (LC50: 10-15 ng/ml in 6 hrs), while glyphosate occurred to be of 500-750-fold less toxicity