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| Titel |
Compound-specific isotope analysis (CSIA) for assessing pesticide dynamics in soil and vadose zone |
| VerfasserIn |
Clara Torrentó, Rani Bakkour, Aileen Melsbach, Violaine Ponsin, Christina Lihl, Volker Prasuhn, Thomas B. Hofstetter, Martin Elsner, Daniel Hunkeler |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150378
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| Publikation (Nr.) |
 EGU/EGU2017-14833.pdf |
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| Zusammenfassung |
| A lysimeter facility was used to study long-term pesticide fate and transport through two
different soils. The present investigation focuses on some commonly and worldwide used
herbicides for weed control on corn (atrazine, acetochlor and metolachlor) and sugar beet
(chloridazon), together with their main degradation products. Since some degradation
products are found more frequently and at higher concentrations that their parent compounds,
there is growing environmental concern. The fate of these metabolites is, however, not
well-understood.
Twelve weighing lysimeters filled with two typical arable soils in Switzerland (a
well-drained sandy loam cambisol developed from a stony alluvium-“gravel soil”- and a
poorly-drained loam cambisol developed from moraine deposits -“moraine soil”-) were
cropped with corn in the first and third seasons, and sugar beet in the second one. Three types
of experiments were performed: (1) herbicides application at the surface simulating the
common application scenario, (2) herbicides injection at a depth of 40 cm for simulating high
preferential transport through the topsoil and assessing the dynamics below the root zone, and
(3) metabolites (2,6-dichlorobenzamide, desphenylchloridazon and desethylatrazine)
application at the surface to simulate rapid generation of transformation products from the
parent compounds. Leachate was collected and the concentration of the applied substances
and main degradation products was determined. Since assessing transport and fate of
micropollutants in the environment is extremely difficult because transformation
processes are slow and may not become evident from analysis of concentrations,
multi-element (C, N, Cl) compound-specific isotope analysis (CSIA) is also being
used.
With both surface application and depth injection, compound breakthrough by
preferential as well as matrix flow was observed. A few days after their application,
significant infiltration of the herbicides took place by preferential flow, bypassing the sorption
and degradation capacity of the soil matrix. Thereafter, the main movement was through the
soil matrix and thus, the longer residence time of the herbicides in the soil zone enhanced
degradation and due to the high mobility of the metabolites, they were detected in the
leachates. Breakthrough of the applied metabolites was also observed. For most of the cases,
concentrations were higher in the leachates of the gravel soil than in the moraine soil.
Preliminary results of C and N isotope signatures of the target compound in the
leachates show significant isotope enrichment trends in acetochlor and metolachlor
and less evident in atrazine, confirming the occurrence of degradation processes. |
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