A Mass Balance Approach Updating the SWAT Pesticide Module for Applications to EMCONs 6/15/2011 1 K. BRASSETT AND L.J. THIBODEAUX Cain Department Chemical Engineering, Louisiana State University, Baton Rouge, LA USA [email protected];[email protected]Platform presentation at 2011 SWAT, University of Castilla La Mancha, Toledo, SPAIN. June 15-17, 2011.b
24
Embed
A Mass Balance Approach Updating the SWAT … Mass Balance Approach Updating the SWAT ... degradation, evaporation ... Forced Inputs Particle(soils) erosion
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
A Mass Balance Approach Updating the SWAT
Pesticide Module for Applications to EMCONs
6/15/2011 1
K. BRASSETT AND L.J. THIBODEAUX
Cain Department Chemical Engineering, Louisiana State
1) Reaction; 2) Solute Transport; 3) Pesticide in Runoff
Results : Glyphosate
6/15/2011 12
-40
-20
0
20
40
60
80
100
120
0 200 400 600 800% D
iffe
ren
ce M
ass
Bal
ance
Time[days]
Glyphosate (t1/2=197d)
A
B
C
D
E
0
20000
40000
60000
80000
100000
120000
140000
160000
180000
0 200 400 600 800Pe
stic
ide
Re
mai
nin
g[kg
/ha]
Time[days]
Glyphosate (t1/2=197d) MassBalance
A
B
C
D
E
F
A B C D E F
123 132 231 312 213 321
1) Reaction; 2) Solute Transport; 3) Pesticide in Runoff
Results: Trenbolone
6/15/2011 13
0
2
4
6
8
10
12
14
16
30 35 40 45 50
Pes
tici
de
Rem
ain
ing[
kg/h
a]X
10
00
Time[days]
Trenbolone[~40 -50 days] MassBalance
A
B
C
D
E
F-4500
-4000
-3500
-3000
-2500
-2000
-1500
-1000
-500
00 10 20 30 40 50
% D
iffe
ren
ce M
ass
Bal
ance
Time[days]
Trenbolone
A
B
C
D
E
F
A B C D E F
123 132 231 312 213 321
1) Reaction; 2) Solute Transport; 3) Pesticide in Runoff
Results
6/15/2011 14
-200
-150
-100
-50
0
50
100
0 5 10 15
% D
iffe
ren
ce M
ass
Bal
ance
Time[days]
Malathion
A
B
C
D
E
F
-600
-500
-400
-300
-200
-100
0
100
200
0 0.5 1 1.5 2 2.5 3
% D
iffe
ren
ce M
ass
Bal
ance
Time[days]
Dibromochloropropane
A
B
C
D
E
F
A B C D E F
123 132 231 312 213 321
1) Reaction; 2) Solute Transport; 3) Pesticide in Runoff
Results Continued
6/15/2011 15
-60
-50
-40
-30
-20
-10
0
0 50 100 150 200%
Dif
fere
nce
Mas
s B
alan
ce
Time[days]
Methoxychlor
A
B
C
D
E
F
A B C D E F
123 132 231 312 213 321
1) Reaction; 2) Solute Transport; 3) Pesticide in Runoff
Conclusion
• The present SWAT pesticide module is the appropriate place for developing an EMCON module
• Transforming the sequential process code to a simultaneous process code that reflects the[Lavoisier] mass balance on the HRU is recommended
• Further research EMCON reaction, transport and thermodynamic partitioning and update pesticide algorithms
• Extend application of mass balance approach to deeper soil layers and other sub-units on the HRU 16
Questions
6/15/2011 17
Questions?
SWAT Model Assumptions/Characteristics
18
User defined Watershed divided into 2-5 sub
layers
Chemical concentration and properties
assumed constant in control volume(HRU)
Model time series
1 time step=1day
Growing seasons
Rain, temperature, water content,
concentration in layers, etc. updated daily
Model tracks chemodynamics in HRU
Model computes the mass of chemical, soil in
runoff ,from HRU
6/15/2011 19
The evaporation half life ( ) is the ratio of the overall mass transfer coefficient for pesticide vapor transport from the soil –to-atmosphere ( to the soil-to-air pesticide partition coefficient (, soil thickness ( and bulk density of the soil (. The units respectively are day-1, meters/day, m3/kg, meters, and kg/ m3. The overall mass transport coefficient, depends on the air side mass transfer coefficient ( [meters/day]), the
chemical’s molecular diffusivity in air ( [m2/day]) the volumetric air content of the soil (, and the soil thickness.