Testing the impact of selected pesticides on denitrification

Testing the impact of selected pesticides on denitrification

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Denitrifying bioreactors are devices used to treat agricultural run-off in situ. It is usually a trench filled with wood chips. The bioreactors work very well for their main purpose, which is reducing the concentration of nitrates entering the environment. But agricultural run-off contains not only nitrates, but also significant amount of pesticides and their metabolites, veterinary pharmaceuticals, etc. Fate of five pesticides (metolachlor, metazachlor, tebuconazole, glyphosate and epoxiconazole) during denitrification was tested via 28-day semicontinous laboratory test. Each test was performed in 15 two-litre glass bottles filled with 30 g of poplar woodchips (source of organic carbon for denitrifying bacteria) and 2 L of liquid medium (distilled water with 15 mg.L−1 NO3-N and 0.5 g.L−1 NaHCO3). Five bottles were treated with a pesticide, while another five were exposed to a denitrification inhibitor in conjunction with the pesticide. The remaining five bottles were utilized as controls. Concentrations of the pesticides were determined in the beginning and in the end of the test. Every 7 days pH, dissolved oxygen and NO3-N were measured. The most significant decline in concentration (exceeding 80 %) was observed for epoxiconazole and tebuconazole, with the results indicating adsorption as the predominant mechanism. The mean concentration of metolachlor, metazachlor and glyphosate declined by 32 %, 53 % and 12 % respectively. The impact of the selected pesticides on denitrification was negligible.

Denitrifying bioreactors are devices used to treat agricultural run-off in situ. It is usually a trench filled with wood chips. The bioreactors work very well for their main purpose, which is reducing the concentration of nitrates entering the environment. But agricultural run-off contains not only nitrates, but also significant amount of pesticides and their metabolites, veterinary pharmaceuticals, etc. Fate of five pesticides (metolachlor, metazachlor, tebuconazole, glyphosate and epoxiconazole) during denitrification was tested via 28-day semicontinous laboratory test. Each test was performed in 15 two-litre glass bottles filled with 30 g of poplar woodchips (source of organic carbon for denitrifying bacteria) and 2 L of liquid medium (distilled water with 15 mg.L−1 NO3-N and 0.5 g.L−1 NaHCO3). Five bottles were treated with a pesticide, while another five were exposed to a denitrification inhibitor in conjunction with the pesticide. The remaining five bottles were utilized as controls. Concentrations of the pesticides were determined in the beginning and in the end of the test. Every 7 days pH, dissolved oxygen and NO3-N were measured. The most significant decline in concentration (exceeding 80 %) was observed for epoxiconazole and tebuconazole, with the results indicating adsorption as the predominant mechanism. The mean concentration of metolachlor, metazachlor and glyphosate declined by 32 %, 53 % and 12 % respectively. The impact of the selected pesticides on denitrification was negligible.

pesticides, denitrification, denitrifying bioreactor

pesticides, denitrification, denitrifying bioreactor

NOVOTNÁ, K.

27.12.2025

STEF92 Technology

978-619-7603-91-0

Proceedings of 25th International Multidisciplinary Scientific GeoConference SGEM 2025

167

174

8

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