TITLE:
An Integrated Geochemical and Mineralogical Approach for the Evaluation of Zn Distribution in Long-Term Sludge-Amended Soil
AUTHORS:
Dominique Proust
KEYWORDS:
Weathering, Soil, Clay Minerals, Heavy Metal, Zinc
JOURNAL NAME:
Open Journal of Soil Science,
Vol.5 No.11,
November
23,
2015
ABSTRACT: This
research work was designed to compare the Zn distribution in a long-term
sludge-amended soil with that in a control soil. Two complementary approaches
were performed: 1) a geochemical approach at the metric scale of the bulk soil
horizons and 2) a mineralogical approach at the micrometric scale of the
primary minerals weathering microsites. The geochemical approach revealed that
Zn in the control soil was inherited from the weathering parent-rock. Its
concentration was always lower than in the amended soil where Zn was supplied
at the surface by the spread sludges and moves downwards. The mineralogical
approach showed that the clay minerals, produced by the weathering of the
primary minerals (amphiboles and plagioclases), or filling the fissure network were
made up of smectites (saponite and montmorillonite) at the bottom and kaolinite
at the top of the two soil profiles. Each clay mineral, with its specific
sorption capacity, controlled the Zn distribution within the soil: the
smectites produced by the amphiboles had high sorption capacity and favored Zn
retention in the upper horizons of the soil. Conversely, the kaolinites
produced by the plagioclases had lower sorption capacity, did not retain Zn in
the surface horizons, and allowed it to migrate to deeper horizons where it was
sorbed onto the montmorillonites.