Monitoring the degradation of atropine and scopolamine in soil after spiking with naturally contaminated organic millet.

The spread of Datura sp. in European countries influences crop management and implies continuous food safety issues because of tropane alkaloids, atropine and scopolamine, the most relevant natural toxic compounds of this weed. These alkaloids can contaminate cereals to such a level that hampers food/feed related use and diverts batches of contaminated raw materials towards ultimate disposal such as burning. As no unambiguous information has been available on the fate of tropane alkaloids in soils, our study focused on the quantification and follow-up of these toxic residues in a soil experiment where the tropane alkaloids were mixed to the soil in the form of naturally contaminated unhulled millet in 1:40 millet:soil ratio - this approach provides a more realistic scenario compared to standard solution based spiking. To achieve accurate results, soil and millet extraction processes have been validated and a liquid chromatography - mass spectrometry set-up was addressed to provide selective and quantitative analysis. The initial concentration of atropine (75ngg-1) and scopolamine (47ngg-1) in the soil decreased with >90% in 15days and reached a high level of elimination (>97%) in 29days. This observation opens an option for the use of tropane contaminated millet or millet waste other than burning, as these toxic alkaloids can be significantly degraded in the soil system. On the other hand, the persistence of intact tropane alkaloids in soils might be questioned to the extent that calls the attention to the (re)assignment of their supposed allelopathic effects.