Environmental Engineering Reference
In-Depth Information
Particle Density
The particle density of soil was determined by pycnometer method described by Blake
(1965b) using electric balance, pycnometer (specific gravity bottle), vacuum desiccators,
vacuum pump and thermometer. Particle density (Dp) was calculated as follows:
dw
(
Ws
Wa
)
Dp=
(
Ws
Wa
)
(
Wsw
Ww
)
Where,
dw
= density of water at temperature observed.
Ws
= weight of pycnometer+ soil sample corrected to oven-dry condition.
Wa
= weight of pycnometer filled with air.
Wsw
= weight of pycnometer+soil+water.
Ww
= Weight of pycnometer+water at temperature observed.
Porosity
Porosity or percentage pore space was determined using the ratio of bulk density to
particle density (Brady, 1974; Lewis 1979) as follows:
Db
Porosity (%) =100-
x100
Dp
Where
Db
=Bulk density.
Dp
= Particle density.
Exchangeable Cations (Ca, Mg, K)
The exchangeable cations (Ca
2+
, Mg
2+
, K
+
) were determined after extraction with 1N
NH
4
OAc (pH 7.0) as followed by Huq and Alam (2005). The exchangeable cations were
measured in the extract by Atomic Absorption Spectrophotometer (AAS).
Total Nitrogen
Total nitrogen was determined by kjeldahl procedure on oven dried soil by the
conversion of amino nitrogen to ammonium in the presence of sulfuric acid, potassium sulfate
and cupric sulfate. After addition of a base, the ammonia was distilled from an alkaline
medium and absorbed in sulfuric acid, and the ammonia determined by an ammonia-selective
electrode (APHA, 1999).
The following formula described by Huq and Alam (2005) modified from APHA, 1999
was used to calculate total nitrogen of soil.
(
T
B
)
f
0
014
250
100
% of nitrogen in soil=
W
V
Where
B
= Amount in ml of N/100 H
2
SO
4
required in titration of the blank experiment.
T
= Amount in ml of N/100 H
2
SO
4
required in titration of the experiment with soil.
