3. Results and discussion
3.1. Transformation
The results of atrazine transformation in the presence of NaN3 are presented in Fig. 1. Transformation of atrazine was pH dependent; the most drastic changes were found for pH 5.5. The concentration of atrazine was reduced by 22% after 3 d of interaction. After 14 d, only 38% of the initial atrazine concentration (10 mg l−1) was detected in a solution containing 1000 mg l−1 NaN3 at pH 5.5 (Fig. 1, top). Interaction of atrazine with a lower concentration of NaN3 (200 mg l−1) resulted in a less drastic decrease. In these conditions, atrazine concentration did not change up to 6 d and only 25% decrease in atrazine concentration was measured after 14 d of interactions. At pH 6.5 (Fig. 1, middle), 200 mg l−1 NaN3 did not affect atrazine concentration, but a 22% reduction in atrazine concentration was observed for the higher NaN3 concentration (1000 mg l−1) after 14 d of interaction. For these two pH studied (5.5 and 6.5), the reduction in atrazine concentration was enhanced with increase NaN3 concentration (from 200 to 1000 mg l−1). At pH 7.5 (Fig. 1, bottom), no significant decrease in atrazine concentration was observed for both concentration of NaN3. In the two controls (HgCl2 and no biocide), concentration of atrazine did not change during experiment. The concentration of the two other studied triazine herbicides (prometon and ametryn) did not change during the experiment at any pH tested for both loads of NaN3 (data not shown).