Agriculture Reference
In-Depth Information
of Waters & Wastewaters
(Rand et al.,
1976
and later editions, APHA Pub.);
Soil,
Handbook 60
.
7.6.3.1 Solute Transport Study by Tracer
Evidence showed that the diffuse (nonpoint) source of pollution plays a major role
in the degradation of the quality of our soil and groundwater systems. Transport
processes governing soil and groundwater contamination by a diffuse source can be
studied by means of a tracer (e.g., chloride and bromide ion (KCl, KBr), tritium).
7.6.3.2 Sample Examples on Solute Transport Problem
Example 7.1
×
In a lysimeter (4m
2m), maize crop was grown. The leaching amount was col-
lected and the concentration of NO
3
-N of the respective leachate for the growing
season and the fallow period are given below. Find out the total amount of NO
3
-N
leached down during the period.
DAE
20
40
60
80
100
120
140
160
180
200
Drainage (l)
0.8
0.6
0.5
0.7
0.7
0.6
3
2.5
3
4
Conc. of NO
3
-N
in drainage
water (mg/l)
4
5
4.5
3
3
4
6
5
4.5
4
DAE is the days after seedling emergence.
Solution
We know, solute amount, M
s
=
V
d
×
C
s
=
drainage volume (l)
×
concentration of solute in the drainage water (mg/l)
For the 20 DAE, NO
3
-N
=
0.8
×
4
=
3.2 mg
Thus the whole calculation follows as
DAE
20
40
60
80
100
120
140
160
180
200
Drainage (l)
0.8
0.6
0.5
0.7
0.7
0.6
3
2.5
3
4
Conc. of NO
3
-N
in drainage
water (mg/l)
4
5
4.5
3
3
4
6
5
4.5
4
Tot a l NO
3
-N, mg
3.2
3
2.25
2.1
2.1
2.4
18
12.5
13.5
16
Tot a l NO
3
-N for 8 m
2
area during the whole period
=
75.05 mg
Thus, total NO
3
-N per hectare of land
=
0.094 kg
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