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| Titel |
Microbial adaption to a pesticide in agricultural soils: Accelerated degradation of 14C-atrazine in field soils from Brazil and Belgium |
| VerfasserIn |
Nicolai David Jablonowski, Rosane Martinazzo, Georg Hamacher, Cesare Accinelli, Stephan Köppchen, Ulrike Langen, Andreas Linden, Martina Krause, Peter Burauel |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035257
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| Zusammenfassung |
| An increasing demand for food, feed and bioenergy, and simultaneously a decline of arable
land will require an intensive agricultural production including the use of pesticides. With an
increasing use of pesticides the occurrence of an accelerated degradation potential has to be
assessed.
Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] is one of the most
widely used herbicides in the world. Even though its use was banned in several countries it is
still widely used throughout America and the Asia-Pacific region. Atrazine is the most widely
used herbicide in maize plantations in Brazil and the US. The use of atrazine in Belgium and
all EU member states was banned in September 2004, with the permission to consume
existing stocks until October 2005.
Atrazine and its residues are still regularly detected in soil, ground and surface
waters even years after its prohibition. Its persistence in soil and in association
with organic particles might become crucial in terms of erosion due to climate and
environmental changes. Due to its potential microbiological accessibility, the microbial
mineralization of atrazine competes with chemical/physical interaction such as sorption and
binding processes of the chemical molecule in the soil matrix. Binding or intrusion of
the chemical on soil components results in a decrease of its accessibility for soil
microbes, which does not necessarily exclude the molecule from environmental
interactions.
In the present study the accelerated atrazine degradation in agriculturally used soils was
examined. Soil samples were collected from a Rhodic Ferralsol, Campinas do Sul, South
Brazil, and Geric Ferralsol, Correntina, Northeastern Brazil. The sampling site of the Rhodic
Ferralsol soil has been under crop rotation (soybean/wheat/maize/oat) since 1990. The Geric
Ferralsol site has alternately been cultivated with maize and soybean since 2000. Both areas
have been treated biennially with atrazine at recommended doses of 1.5 – 3.0 kg ha-1.
Additionally, samples were taken from a Belgian field which was used for corn-plantations
and which was regularly treated with atrazine for the last 30 years in varying doses of 0.5 –
3.0 kg ha-1.
The experiment was performed using 14C-labelled and unlabelled atrazine in accordance
to a field application dose of 3 mg kg-1 for the Brazilian soils, and 1 mg kg-1 for the Belgian
soil, equaling approximately 3.0 and 1.0 kg ha-1, respectively.
All soils with atrazine application history showed a high extent of atrazine mineralization,
indicating a highly adapted microbial community being able to mineralize this
pesticide.
After 15 days of incubation, about 75 % of the initially applied 14C-atrazine was
mineralized in the Rhodic Ferralsol, while in the Geric Ferralsol it did not exceed 15
% of the total applied 14C-activity. After a total incubation time of 85 days, the
amount mineralized reached 82 % in the Rhodic Ferralsol and 74 % in the Geric
Ferralsol.
In the Belgian soil, after a total incubation time of 92 days, the mineralized amount of
atrazine reached 83% of the initially applied 14C-activity in the atrazine treated soil for the
slurry setup. A maximum of atrazine mineralization was observed in the treated field soil
between 6 and 7 days of incubation for both, 50% WHCmax and slurry setups. The total
14C-atrazine mineralization was equally high for 50% WHCmax in the atrazine treated soil,
totaling 81%.
The formation of desorbable metabolites as well as the formation of unextractable,
bound atrazine residues during the incubation process was monitored by desorption
and accelerated solvent extraction, and successive LC-MSMS and LSC analyses,
subsequent to sample oxidation. With increasing incubation time the presence of atrazine
metabolites increased in the extracts, with hydroxyl-atrazine as the main metabolite. |
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