Katalin Lányi

In the soil, pesticides undergo various abiotic and biotic transformation reactions. The effect of soil constituents can be modelled by several additives. TiO2, clay minerals, humic materials and other photosensitizers have been used in several studies for this purpose. The aim of this study was to assess the possible degradation pathways of methabenzthiazuron occurring within natural circumstances by means of laboratory model experiments. The additives used for this purpose were a photosensitizer (TiO2), benzophenone for studying charge transfer (sensitising) effects, and materials naturally occurring in the soils (montmorillonite, humic acid). The charge transfer complex formed between the herbicide molecule and benzophenone was expected to promote the degradation, because it increases the efficiency of energy transfer. The results of experiments supported this expectation, since the degradation methabenzthiazuron was the fastest in the presence of benzophenone. The overall effect of humic acid was moderate inhibition. Since the humic acid – herbicide ratio occurring in soils falls to the same magnitude as utilised in these experiments; presumably, this kind of effect can take place in the soil, too. TiO2 and montmorillonite have slightly increased the rate of degradation, however, in the case of TiO2 this effect cannot be considered significant.

The study was performed on 20 (10 males, 10 females) roe deer (Capreolus capreolus) to investigate the concentration of cadmium, lead, mercury, and arsenic in the muscle tissue. They reside in forest and meadow, about 50 km distance from industrial activities and traffic. Samples were taken from the musculus biceps femoris of each deer without external contamination after shooting during the regular hunting season on a hunting area close to Eger in Hungary. The determination of heavy metal contents was carried out by inductively coupled plasma optical emission spectrometry (ICP-OES). The statistical analysis was performed by statistical package for the social sciences (SPSS) version 11.0. The measured residue concentration of cadmium was below the limit of detection in the roe deer meat indicating no health risk for the consumers. The average lead concentration (0.48±0.21 mg/kg wet weight) exceeded the regulated maximum limit, but its calculated weekly intake was below the provisional tolerable weekly intake (PTWI). The residue level of mercury is not regulated and the average mercury content of roe deer meat (0.87±0.40 mg/kg wet weight) was about half of PTWI, but the consumption of meat with the highest detected concentrations results in higher PTWI than recommended. The measured concentration of arsenic (0.27±0.20 mg/kg wet weight) in the roe deer meat may not pose any health risk for the human consumers according to the PTWI set by theWorld Health Organization.

ABSTRACT By means of electrospray, matrix-assisted laser desorption/ionization time-of-flight and high resolution fast-atom bombardment mass spectrometric techniques some new components have been found in crude desertomycin complex and their molecular mass and characteristic structural features determined.

The aim of this research was to study the way the humus content of the soils affects the adsorption of particular organic pollutants. We used five different media during the experiments: two different soils (sandy soil, coherent soil), humic acid extracts extracted from these soils, and a commercially available humic acid product. We studied the adsorbed amount of the given compounds at the particular media, the role of humic materials in the observed adsorption ratios, and whether the co-existence of the different compound changes the adsorption–desorption conditions.The inorganic components of the soils play an important role also in the absorption of the apolar compounds, and as the polarity (or polarizability) of the organic compound increases, the humic materials of the soil, or rather their polar functional groups take the dominant role in the absorption of the pollutant. The absorption and desorption of three apolar compounds were practically not influenced by the presence of other pollutants in the soil, and this phenomenon was also independent from the extracting agent. However, in the case of polar diuron, the presence of other pollutants can result in decrease of mobility.

The objective of this study was to assess the characteristics of the in vitro phototransformation of the urea-type herbicides diuron, fenuron, chloroxuron, and methabenzthiazuron to obtain information about their possible fate, and about their derivatives, in the environment. Loss and oxidation of the alkyl chains are the dominant processes occurring during degradation of the ureas; substitution of halogen atoms by hydroxyl groups and hydroxylation of the aromatic ring are secondary processes. The large amounts of dimers suggest that radical processes dominate in the photodegradation of ureas. The well known carcinogenicity of azo compounds makes this of outstanding importance.

Summary  In this paper we report our research in developing a simple and reliable method for determination of various anions in aqueous samples. Among the several methods existing for determining ions in aqueous samples, ion chromatography is becoming more and more important, due to its reliability and ability to determine the concentration of more ions from one sample. Although several detection methods are available, in this work we used conductivity detection, and indirect UV photometric detection. Because in some cases it can be important to gather more detailed information on the composition of a sample, we present a way to meet this demand by using double channel detection.

ABSTRACT The photodegradation behaviour of 12 nitrogen-containing herbicides (atrazine, cyanazine, terbuthylazine, terbutryn, EPTC, buthylate, molinate, cycloate, vernolate, fenuron, chloroxuron, and methabenzthiazuron) has been examined. The compounds were degraded completely when exposed to a mercury-vapour lamp; the degradation process was followed by consecutive GC measurements. All the compounds studied had measurable photochemical activity, although actual and average degradation rates varied significantly. All the compounds except terbutryn furnished more than one major degradation product, in different ratios.

Various biotic or abiotic factors influence the fate of pesticides in the natural environment, of which ultraviolet (UV) component in the sunlight is one of the most powerful forces. Studies on the photodegradation of pesticides have not only significance from the point of view of environmental science, but also very important in researching and developing new, safer, and effective pesticides. Previously we have studied the photodegradation of triazine- and urea-type herbicides in details. This paper is intended to outline the photodegradation pattern of some commonly used N-containing herbicides that belong to the groups of the mentioned triazines (atrazine, cyanazine, terbuthylazine, terbutryn) and ureas (chloroxuron, methabenzthiazuron, diuron, fenuron), as well as thiolcarbamates (butylate, cycloate, EPTC, molinate, vernolate), in order to gain information about their possible fate and derivatives in the environment.The most significant processes of photodegradation of triazines are the partial or complete loss of side-chains, or rather the substitution of the heteroatom-containing side-chain to hydroxyl-group. The chemical characteristics of the side chains determines basically the speed of the degradation. It can be concluded that the C–S bond breaks down much easier than C–Cl bond, and the chlorine atom remaining on the triazine-ring promotes the loss of alkyl-chains to a higher extent than that the hydroxy-group. In the case of ureas, the chemical properties of groups in both the N and N′ position can influence the degradation process. It could be stated the proximity of large aryl-substituent and methyl-group in the N position is unfavorable and instabilizing, promoting the further degradation of compound, at the same time, loss of these groups is the preferred degradation route. In the case of thiolcarbamates, the most frequent processes are the α- and β-oxidation of alkyl-groups connecting to the nitrogen atom. In the most cases, the N-formyl and N-dealkylated products were identified in the degradation mixture. The thioalkyl-group showed fair stability under the circumstances of photodegradation. Its partly or completely degraded products cannot be detected, and represent only very small part of the mixture.

Triazines are amongst the most widely used herbicides. Since triazines can be found in many environmental compartments, their fate in ecosystems and the characterization of their degradation pathways in the environment are to be determined. In this paper we report on a study intended to investigate the photodegradation of some triazine-type herbicides: atrazine, cyanazine, terbuthylazine and terbutryn. The rate of photodegradation process was determined, and degradation schemes were outlined for the compounds studied. Moreover, experiments with different degrading energies were carried out in order to gain information about the effect of total degrading energy on the photodegradation process. The most significant processes of photodegradation of triazines are the partial or complete loss of side-chains, or rather the substitution of the heteroatom-containing side-chain to hydroxyl-group. Besides consecutive processes, loss of the different side-chains takes place parallely also, thus, different metabolites will be formed having mixed side-chains, until the cyanuric acid and 2-amino-4,6-dihydroxy-1,3,5-s-triazine are formed by losing all the side-chains. The presence of the dimer products could be detected during the degradation of all triazines. This proves the radical character of processes occurring during the photodegradation. Increasing the degradation energy (15 to 125 W) has raised the degradation rate by 2–5, and the chlorine containing metabolite—which was still present in the completely degraded mixture during the low-energy experiments—has completely disappeared from the mixture, thus, the increased degrading energy is favorable to the formation of less dangerous, nature identical metabolites.