Atrazine under denitrifying conditions

The use of pesticides has negative effects on the quality of groundwater. The triazine pesticide atrazine has not been applied to soil in agriculturally used areas of the Czech Republic for many years, yet atrazine and its metabolites are detected in groundwater throughout the country. The effect of these substances on the denitrification process that takes place in groundwater is unclear. This study aims to examine the behavior of atrazine under denitrifying conditions and the pesticide�s effect on the denitrification process. 7-day and 28-day laboratory tests at a concentration of 100 ?g/L atrazine were performed to simulate such conditions. A single dose of atrazine was introduced to the samples at the beginning of the tests. No inhibition of the denitrification process was detected in any of the tests. Stimulation of denitrification was measured in the last week of the 28-day test. Adsorption on poplar shavings was the dominant process of the decrease in atrazine concentration during both the 7- and 28-day tests. The biotic loss was 3.9% for the 7-day test. In the 28-day test, there was a total biotic loss of 12.1%. A similar biotic loss of 9.8% was measured also in a 7-day test performed at higher pH. At the end of the 28-day test, the transformation product atrazine-2-hydroxy was detected in the supernatant in very low concentrations. A significant effect of the HgCl2 inhibitor on the instantaneous adsorption rate was observed for all tests.