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| Titel |
Influence of dry-wet cycles on the water-extractability of aged 14C-pesticide residues in soils |
| VerfasserIn |
Nicolai David Jablonowski, Andreas Linden, Stephan Köppchen, Daniel Goebbels, Björn Thiele, Diana Hofmann, Peter Burauel |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048157
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| Zusammenfassung |
| Due to future climate predictions, an increase in droughts, followed by heavy rain events can
be estimated. Soil drying and rewetting may have a considerable impact on an increased
release of pesticides present in agricultural soils, representing a potential risk by pulse inputs
to deeper soil layers or aquifers after rain events. Laboratory studies using soil containing
environmentally long-term aged (9-17 years) 14C-labeled residues of the herbicide
ethidimuron (ETD), methabenthiazuron (MBT) and the fungicide anilazine (ANI) showed a
significant increase of 14C-activity in the water-extract after soil drying. The total
water-extracted 14C-activity (the amount of residual 14C-activity in the sample equals 100%)
accounted for 44% (ETD), 15% (MBT), and 20% (ANI) after 20 alternating dry-wet cycles.
The amount of water-extracted 14C-activity from the constantly moistured soil
remained significantly lower at 16% (ETD), 5% (MBT), and 6% (ANI) after 20
cycles, respectively. LC-MS/MS analyses of the raw water extracts of the dried and
rewetted soils revealed the parent compound ETD and MBT in detectable amounts
(15.0 μg ETD kg-1 and 0.23 μg MBT kg-1in total, calculated per kg soil (0-10 cm
ETD-soil / 0-30 cm MBT-soil), accounting for 1.83% and 0.01% of total applied parent
compound per soil layer, respectively), but neither ANI nor the main ANI metabolite
dihydroxy-anilazine could be detected. In comparison, the constantly moistened soil
released significantly smaller amounts of residual pesticide fractions (1.87 μg ETD
kg-1 in total, calculated per kg soil (0-10 cm ETD-soil), accounting for 0.23% of
total applied parent compound, respectively, but no MBT or ANI residues were
detected).
For all soils the water-extracted dissolved organic carbon (DOC) was significantly higher
in the previously dried soils, compared to the constantly moistened soils (ETD-soil: 10.8 vs
4.8%; MBT-soil: 8.4% vs 3.7%; ANI-soil: 9.8% vs 4.6% of total organic carbon in the soil).
In case of the previously dried soils, the DOC content correlated with the measured
14C-activity in the aqueous liquids (ETD-soil: r=0.80; MBT-soil: r=0.81; ANI-soil:
r=0.91).
The overall finding demonstrates a readily water-extractable pesticide residue fraction
which can easily be removed from the soil, representing a potential risk for leaching.
The data suggest that an increase in environmentally relevant dry-wet cycles may
result in an increased remobilisation and release of aged pesticide residues in soils. |
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