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Mogens Humlekrog Greve

Water and solute transport in agricultural soils predicted by volumetric clay and silt contents

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Solute transport through the soil matrix is heterogeneous and
greatly affected by soil texture, soil structure, and macropore networks.
This study examined the relationship between tracer breakthrough
characteristics, soil hydraulic properties, and basic soil properties.
Hundred-and-eighty-seven undisturbed soil columns 20 cm in height and 20
cm in diameter were sampled from six conventionally managed agricultural
fields in Denmark. The soils exhibited a wide range in texture, with clay
contents and organic carbon (OC) contents ranging from 0.03 to 0.41 kg
kg-1 and 0.01 to 0.08 kg kg-1, respectively. All experiments were carried
out under the same initial and boundary conditions using tritium as a
conservative tracer. The breakthrough characteristics ranged from being
normally distributed to having more preferential characteristics along
with an increase in the content of the mineral fines (particles ≤ 50 μm).
The results showed that the mineral fines content was strongly correlated
to functional soil structure and the derived tracer breakthrough curve
(BTC), whereas the OC content appeared less important for the shape of
the BTC. Organic carbon was believed to support the stability of the soil
structure rather than the actual formation of macropores causing
preferential flow. The arrival times of 5 % and up to 50 % of the tracer
mass were found to be strongly correlated with volumetric fines content.
The hereby predicted tracer concentration breakthrough points up to 50%
of applied tracer mass could be well fitted to an analytical solution to
the classical convection-dispersion equation. Both cumulative tracer mass
and concentration as a function of time were hereby reasonable well
predicted from the simple inputs of bulk density, clay and silt contents,
and applied tracer mass. The new concept seems promising as a platform
towards more accurate proxy functions for dissolved contaminant transport
in intact soil.
TidsskriftJournal of Contaminant Hydrology
Sider (fra-til)194-202
StatusUdgivet - 2016

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