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| Titel |
Distribution of organic carbon and chemicals in agricultural soils (BET method) |
| VerfasserIn |
F. Schnitzler, J.-M. Séquaris, A. E. Berns, P. Burauel |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023599
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| Zusammenfassung |
| Modelling the dynamics of soil organic carbon and chemicals in soils requires
compartmentalisation in pools or fractions. The determination of organic carbon and
chemical concentration in all fractions is often time-consuming or not realisable due to low
amount of soil fractions. Therefore, we developed an analytical method to calculate
distributions of organic carbon and chemicals in soil without any chemical extraction method.
Two sets of experiments were conducted with undisturbed soil columns under field-like
conditions. In the first set, maize straw was incorporated into the topsoil and after three
months incubation, the 14C-labelled chemicals benazolin or benzo[a]pyrene were applied.
The second set was treated equally, but without maize addition. After a total incubation time
of six months, the topsoil layers were fractionated with a physical aggregate size fractionation
procedure[1].
The content of organic carbon and the distribution of the chemicals were detected in the
gained soil fractions. Furthermore, the BET method was used to determine the specific
surface area (SSA) of selected soil fractions.
It can be shown that a fraction of organic carbon and chemicals is dependent on the SSA.
The slopes of these linear relationships have been used for the estimation of the organic
carbon[2]
or chemicals associated to the clay fraction. Thus, mass concentrations of organic carbon or
chemicals located in the clay and silt+sand fraction can be calculated.
It has been found that the influence of the incorporated maize straw on the amount of
organic carbon in the fractions is low due to strong mineralisation processes. In general, the
amount of organic carbon in the silt+sand fraction is higher than in the clay fraction. In
contrary, the 14C-activity of the chemicals is higher in the clay fraction than in the silt+sand
fraction. However, the addition of maize straw increases the amount of 14C-activity in the
silt+sand fraction.
The calculated distribution coefficients Kd and KOC indicate a stronger sorption of
benzo[a]pyrene than benazolin derivates. Furthermore, a stronger binding of chemicals to the
clay fraction than to the silt+sand fraction can be observed. The incorporation of maize straw
increases the Kd values of benazolin and its metabolites in all fractions due to stronger
metabolism of the herbicide[1]. The KOC of benzo[a]pyrene is more or less constant in the
clay fraction after straw incorporation. However, an increase of the KOC value in the
silt+sand fraction is observed, which can be related to the binding capacity of the OC straw
derivates. In dissolved forms (DOC), they can be involved in co-transport processes of
benzo[a]pyrene. |
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