Soil Organic Matter Management: The Roles of Residue Quality in C Sequestration and N Supply - Sustainable Management of Soil Organic Matter - page 147

extractable

88

55 63

100

Fig. 3.6.4. Relative distribution of [ 14 C]simazine-radioactivity amongst different extracts of
compost material during various stages of composting. Er = extractable radioactivity; NER =
non-extractable residues.

[ 14 C]Simazine

The HPLC analysis showed that the 14 C-radioactivity in the aqueous
extracts and organic extracts consisted of metabolites as well as simazine
(Fig. 3.6.4). Already after the thermophilic phase, NERs comprised up to
64% of the initial 14 C-radioactivity, and this increased slightly with time.
Since metabolites were present in the extracts, it can be assumed that NERs
preferably consisted of metabolites and only to a lower extent of the parent
compound, simazine.
Figure 3.6.4 shows a very slight decrease in the ratio value. However,
considering the deviations of the data, release of NERs cannot be ruled out.
However, if there was a release of 14 C-radioactivity, it is questionable as to
whether it would consist of simazine or its degradation products.

Conclusions

The investigated test substances had a very different fate during compost-
ing and the following long-term study. The formation of NERs could not
be explained by one mechanism alone. The hazard potential of compost
application due to release of NERs under the experimental conditions has
to be discussed:

1. DEHP: NERs were formed to a small extent only. Considering the
large deviations of the data, no clear prediction can be made about release
of NERs. However, a potential release should be expected for small
amounts only.