Agriculture Reference
In-Depth Information
Chapter 2
E
NVIRONMENTAL
I
MPACT OF
P
HOSPHATE
F
ERTILIZERS AND
B
Y
-P
RODUCTS
ON
A
GRICULTURAL
S
OILS
Lina Nafeh Kassir
*
University of Holly Spirit Kaslik, Faculty of Sciences,
URA GREVE (CNRS/USEC/UL), Lebanon
A
BSTRACT
Soil amendment with phosphate fertilizers and by-products such as phosphogypsum
becomes of an increasing importance in agriculture. This may lead, however, to soil,
plant and groundwater contamination with trace elements inherently present in both
products. Monitoring of selected trace elements (Cu, Pb, Zn and Cd) distribution and
mobility in a Mediterranean red soil profile has been performed in soil and plant samples
collected from various depth intervals at different points in time. Trace elements
sequential extraction was conducted on collected samples. Samples were examined under
a Scanning Electron Microscopy (SEM) coupled with an Energy Dispersive X-ray
spectrometer (EDX). Phosphogypsum increased the solubility of the studied trace
elements where they were bound to exchangeable and acid-soluble fractions in higher
percentages than reference soil. After the period study of phosphogypsum amendment
(16 months), Pb, Zn and Cu were sorbed into mineral soil phases while Cd was mainly
found in the exchangeable form. On the contrary, Pb, Zn and Cu were transferred from
residual to exchangeable fraction except for Cd in fertilizers application. Cichorium
intybus accumulated higher trace elements concentrations than the reference plants, but
they remained within normal reported levels except for Cd where it exceeded the
recommended tolerable levels in phosphogypsum application, thus signifying potential
health threats through contaminated crops. Evidence of fluorine was detected by SEM in
the fertilizers amended soil which should be a matter of concern in phosphate fertilizers
application.
Keywords
: Soil amendment, trace elements, mobility, plant uptake
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