STUDY OF THE SORPTION OF HERBICIDES IN DIFFERENT SOIL SOLUTION SYSTEMS. Ph.D. Theses. Tímea Ertli

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1 STUDY OF THE SORPTION OF HERBICIDES IN DIFFERENT SOIL SOLUTION SYSTEMS Ph.D. Theses Tímea Ertli University of Veszprém Doctoral School of Environmental Sciences 2005.

2 INTRODUCTION The clarification of the environmental impact of pesticides is an important and urgent task due to their soil and water contamination. Their fate is influenced by many biotic and abiotic factors like the adsorption on the soils. The adsorption of isoproturon and prometryn being weakly polar and moderately soluble herbicides was studied in different soil solution systems. Static equilibrium experiments were carried out on three soils with different organic matter content (chernozem, brown forest and sandy soil) and in the present of soil constituents (quartz and extra humic substance content). The variable factors of the experiments were the quality of electrolytes, the ph (ph=5, ph=7, ph=8) and the dissolved organic matter (DOM) content. To get to know the role of the additives in the process the adsorption experiments were carried out at neutral ph with the herbicide Glean 75DF with its active ingredient chlorsulfuron and with mixtures made of chlorsulfuron and two different additives (Supragil and Borresperse). The analytic methods used were mainly liquid chromatography (HPLC) and in certain cases total organic carbon determination and UV-spectrophotometry. The adsorption isotherms were fitted with a special equation which represents the steps very well. The parameters of this equation having exact physicochemical meaning were used for the interpretation of the adsorption. Special attention was paid to the role of the dissolved organic matter. The degradation of isoproturon was studied, too. It was investigated by GC-MS whether the different conditions lead to different degradation products.

3 NEW SCIENTIFIC RESULTS 1. Measuring the specific adsorbed amount of the same samples by different analytical techniques (i.e. high-pressure liquid chromatography, UV spectrophotometry and total organic carbon determination) resulted in remarkable difference. This is caused not simply by the methods but also by the disturbing effects of the humic substances as well as of the associates between the solute and the dissolved humic substances. In the case of soil adsorbents the higher is the equilibrium concentration the more remarkable is this difference. Despite the altering results of the analytical methods it s worth to use more of them since they show different sides of the mechanisms of the processes. 2. The adsorption and the mobility of the investigated herbicides (isoproturon, prometryn) are ph-dependent. The measure of this dependency is the function of the properties of the sorbent (soil, quartz), the changes of the surface as well as of the solute molecules. 3. In acidic solutions the specific adsorbed amount of isoproturon and prometryn is generally higher than in alkaline solutions. It is caused by the protonation of the solute molecules at low ph and this can result in H-bonding and electrostatic interactions. In environmental systems the temporary acidification of the soils or the acid rain can fix the herbicide on the soils but later it can be released as the buffer capacity of the soils acts. In the adsorption of isoproturon and prometryn the hydrophobic interaction plays the major role. If the insoluble organic content of the soils is high the immobilization of these compounds is more likely. 4. The dissolved organic matter (DOM) whose concentration is the function of ph form a colloid system helping the solubilization and the association of slightly polar organic pollutants. The mobilization of the herbicides isoproturon and prometryn plays a special role in their distribution between the sorbent and the liquid phase.

4 5. The adsorption of chlorsulfuron is independent or slightly dependent on the organic matter content of the soils and its specific adsorbed amount is very similar to that of its formed herbicide Glean 75DF. The additives (wetting agent and dispersant) having various role resulted in different adsorbed amounts of chlorsulfuron: the dispersant led to the lowest adsorbed amounts. 6. The isotherms fitted by the special equation which describes consecutive adsorption of the herbicides consist of at least two steps. The diffuse environmental pollution whose concentration range can be modelled with the first step of the adsorption isotherms is weakly influenced by the ph. In case of higher concentrations (point-like pollutions) ph plays the main role in the processes of the adsorption. The higher steps can be interpreted with the effect of binding places with the another kind of interaction or with the effect of surface complexes with different association degree which appear in the parameters of the equation. The dissolving humic substances play an important role in the determination of the shape of the higher steps. 7. The degradation experiment of isoproturon showed that on soils having higher organic matter content the rate of the degradation is faster but it was independent from ph. On chernozem which had the highest degradation rate two metabolites of isoproturon (N-methyl-N -(4-i-propyl-phenyl)urea and N- (4-i-propyl-phenyl)acetanilide) were identified by GC-MS which were only known before as degradation products formed during UV irradiation.

5 SCIENTIFIC PUBLICATIONS 1. Földényi, R., Ertli, T., Mód, R.: The fate of the herbicides prometryn and metolachlor in the soil/soil solution system, Central European Journal of Occupational and Environmental Medicine (Budapest), 2002, 8 (2-3), pp Földényi, R., Czinkota, I., Ertli, T.: Presentation of multistep isotherms formed at the adsorption of herbicides, Progr Colloid Polym Sci, 2004, 125, pp Ertli, T., Marton, A., Földényi, R.: Effect of ph and the role of organic matter in the adsorption of isoproturon on soils, Chemosphere, 2004, 57, 8, pp

6 SCIENTIFIC LECTURES 1. Ertli, T., Polyánka, H., Váradi, Gy., Darkó, É., Lehoczki, E.: Lowered xanthophyll cycle capacity accompanying triazine resistance of weeds, XIth International Congress on Photosynthesis (Budapest, 1998) In: Photosynthesis: Mechanisms and Effects, (ed. G. Garab) Vol. III, pp Kluwer Academic Publishers 2. Polyánka, H., Makrai, L., Ertli, T., Lehoczki, E.: Comparison of sensitivity of triazine-resistant and susceptible biotypes of several weeds to UV-B exposure, XIth International Congress on Photosynthesis (Budapest, 1998) In: Photosynthesis: Mechanisms and Effects, (ed. G. Garab) Vol. III, pp Kluwer Academic Publishers 3. Ertli T., Polyánka H. (1999): Investigations on the stress effects of sunlight and UV-B light on D1 protein mutant weeds (in Hungarian), Proceedings of XXIV. OTDK, Term.tud. Szekció II., Debrecen, ed. Dr. Bazsa György KLTE, p Ertli, T., Földényi, R.: The possibility of application of the instrument liquitoc in the analysis of soils having high salt concentration (in Hungarian), Proceedings of 7 th Symposium on Analytical and Environmental Problems, SZAB, Szeged, 2 Oct. 2000, pp Ertli, T., Földényi, R.: The ph dependency of the adsorption of isoproturon on different adsorbents (in Hungarian), Proceedings of 8 th Symposium on Analytical and Environmental Problems, SZAB, Szeged, 1 Oct. 2001, pp Ertli, T., Földényi, R.: The fate of herbicide isoproturon in the environment A study on the sorption of the herbicide on Hungarian soils (in Hungarian), XXIV. Kémiai Előadói Napok, Szerves-, Gyógyszer- és Biokémiai Szimpózium, Okt , SZAB, Szeged, MKE conference issue, pp

7 7. Ertli, T., Földényi, R.: Effect of the ph on the adsorption of isoproturon herbicide on Hungarian soil types and quartz, Proceedings of Symposium of Risk Assessment and Management of Large Contamination Sites, Halle (Saale), Saxony Anhalt, Germany, Feb Ertli, T., Földényi, R., Décse, Zs.: Effect of the ph on the adsorption of prometryn on Hungarian soils, Abstracts Book of SETAC Europe 12 th Annual Meeting (Challenges in Environmental Risks Assessment and Modelling: Linking Basic and Applied Research), Vienna, Austria, May, 2002, p Ertli, T., Földényi, R.: The role of humic substances in the adsorption of isoproturon and prometryn on soils, Abstracts Book of 8 th Conference on Colloid Chemistry, Keszthely, September, 2002, p Földényi, R., Czinkota, I., Ertli, T.: Presentation of multi-step isotherms formed at the adsorption of herbicides, Abstracts Book of 8 th Conference on Colloid Chemistry, Keszthely, September, 2002, p Földényi, R., Ertli, T., Lengyel, Zs., Rauch, R.: Retention of Selected Herbicides in Soils, Proceedings of the MTA-OTKA-NSF project Natural attenuation of metals along the Tisza river floodplain - wetlands continuum, Eds.: Adriano, D. C., Németh, T., Győri, Z., University of Debrecen, Centre of Agricultural Sciences, 2003, pp