الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
This study aimed at evaluting the influence of sewage sludge (as an
organic amendment) and the commonly used gypsum (as an inorganic
amendment) on distribution and transport of some trace elements (Fe,
Mn, Cu and Zn), cations (Ca, Mg, Na, and K) and anions in saline sodic
soils throught period of continuous leaching of these soils.
To fulfill the purposes of this study, three surface soil samples
differing in their contents of salts, exchangeable Na percentages (ESP),
texture and cation exchange capacities were collected from three different.
localities . A column experiment, was conducted. In this experiment, soil
samples were mixed with either sewage sludge (at rates of 3 % and 6%)
or gypsum (CaS04.2H20) at rates of 100 % or 200 ~Ioof the gypsum
requirements. The soils were packed uniformly in columns of PVC. A
constant head of water was kept above the soil surface throughout the
period of the experiment. Leachate was collected in 200mI fractions.
Period of collecting each leachate fraction was :recorded. Also, soluble
, cations and anions as well as soluble (leached) trace elements (Fe, Mn,
Cu, and Zn) of each leachate fraction were determined. At and of leaching, each soil column was cut into 4 segments, each of them was analysed for total Ca, Mg, Na and K as well as total andavailable trace elements(Fe, Mn , Cu and Zn).A fractionation experiment was conducted to find out the
distribution of Fe, Mn , Cu and Zn among the different soil components.
In this experiment, fractions of the studied trace elements were extracted
using a modified version of sequential fractionation scheme proposed by
Me Laren and Crawford(1973).
The obtained results could be summarized in the following:
I-Percentages of total cations (Ca,Mg, Na and K) remained in the
different segments of the investigated soils were reduced markedly due
to continuous leaching.
Application of sludge or gypsum enhanced transportation ofNa
and K from the surface layers to the layers below. On the other hand,
percentages of Ca and Mg remained in the different segments of the soils
received sludge or gypsum were, in most cases, higher than the
corresponding values of the soils received distilled water only.
2-A very limted transport of total Fe occurred within the soil columns,
being more obvious in the few surface centimeters. Available Fe was,
generally, highest in the surface layer and tended to decrease
depthwise. In all the investigated soils ~total as well as available Mn
did not show a certain pattern of distribution with depth.
Total and AB-DTPA-extractable Ca were almost constant within
the different depths of each.studied soil.
Total Zn as well as AB-DTPA extractable Zn followed patterns of
distribution differed from a soil to another.
The effect of suldge or gypsum on distribution of the above
mentioned trace elements in the different segments of the amended soils
seemed dependent on type of the applied amendment and its rate of
application.
Briefly, application of sewage sludge or gypsum seemed to
improve physical properties of the investigated soils and thus maximized
the effect of leaching on transport of trace metals in the studied soils.
3-The leaching process resulted in decrease in E¢ values of the leached
soil reflected on EC values of the leachate fractions , the effect was
highest in the second leachate fraction w~ere a sharp decrease
occurred. Also, the time required to receive this leachate fraction
seemed to be obviosly decreased.
The pH values of the different leachate fractions fluctuated slightly
about neturality. Number of the leachate fraction did not show a marked
effect on values of leachate pH.
Ca,Mg, Na and K concentrations were highest in the first leachate
fraction and tended to decrease thereafter to almost;constant values.
The above mentioned trends characterized the soils leached with
water only as well as the soils leached and received sewage sludge or
gypsum simulatneously.
Concentrations of the soluble trace elements i.e. Fe, Mn, Cu and
Zn in the leachate fractions were variable and dependent on number of
leachate fraction, type of soil amendment and characteristics of the
concerned soils.
4-Fractionation of iron revealed that Fe was distributed among the
different soil components in the following descending order :
Residual Fe> occluded Fe > organically bound F~> inorganically bound
Fe > soluble +exchangeable Fe.
This pattern of Fe distribution was noticed in the soils reclaimed by ,
leaching only as well as in those leached ard amended with sewage
sludge or gypsum at any of their application rate,
Manganese fractions were found to be arranged in different orders
according to soil type and soil treatment
The main pattern ofMn distribution was:
Residual Mn > occluded Mn > inorganically bound Mn > organically
bound Mn > soluble +exchangeable Mn.
This pattern of Mn distribution among the different soil
components characterized soils of Abo-Soltan and El-Kassasen whether
they were leached with water only or received sewage sludge also at any
rate of its application. Mn followed the same pattern of distribution in El-
Kassasen soil that was leached and received gypsum similtaneously.
However, some other patterns were detected such as
a-Occluded Mn > Residual Mn > inorganically bound Mn > organically
bound Mn > soluble + exchangeable Mn .
b- inorganically bound Mn > occluded Mn :> organically bound Mn >
residual Mn > soluble + exchangeable Mn Variations in characterestics of the investigated soils and type of the used
amendment may account for such findings.
Copper fractions were found in the following order :
Occluded Cu > residual Cu > organically bound Cu > inorganically
bound Cu > soluble + exchangeable Cu .
Zinc fractions followed mainly the order : Residual Zn > occlouded Zn > organically bound Zn > inorganically
bound Zn> soluble + exchangeable Zn .
However, the following orders were also detected : Residual Zn > organically bound Zn > inorganically bound Zn>
Occluded Zn > soluble + exchangeable Zn Residual Zn > organically . bound Zn > occluded Zn > inorganically
bound Zn> soluble + exchangeable, Zn.
The different distribution patterens of Zn seemed dependent on soil
characteristics , amendment type and rate of application .