Download Natural Organic Matter

Stochastic Synthesis of
Natural Organic Matter
Steve Cabaniss, UNM
Greg Madey, Patricia Maurice, Yingping Huang,
Xiaorong Xiang, UND
Laura Leff, Ola Olapade KSU
Bob Wetzel, UNC
Jerry Leenheer, Bob Wershaw USGS
ASLO 2004 - Savannah, GA
June 2004
NOM Questions:
• How is NOM
produced &
transformed in the
environment?
• What is its structure
and reactivity?
• Can we quantify NOM
effects on ecosystems
& pollutants?
Environmental Synthesis
of Natural Organic Matter
Cellulose
Lignins
Proteins
Cutins
Lipids
Tannins
O2
light
bacteria
H+, OHmetals
fungi
NOM
Humic substances
& small organics
CO2
Simulating NOM Synthesis
Probabilistic Reaction Kinetics
For first or pseudo-first order reaction
P = k’ Δt
P = probability that a molecule will react
with a short time interval Δt
k’ = first or pseudo-first order rate constant
units of time-1
Based on individual molecules
Stochastic Algorithm:
Advantages
• Computation time increases as # molecules,
not # possible molecules
• Flexible integration with transport
• Product structures, properties not predetermined
Stochastic synthesis: Data model
Pseudo-Molecule
Elemental
Functional
Structural
Composition
Calculated
Chemical
Properties
and Reactivity
Location
Origin
State
Stochastic synthesis:
Environmental Parameters
Chemical:
Water
pH
[O2]
Physical:
Temperature
Light Intensity
Duration
Biological:
Bacterial Density
Oxidase Activity
Protease Activity
Decarboxylase Activity
Model reactions transform structure
Ester Hydrolysis
O
H
+
R
O
C
O
+
R
R
H+
+
R
HO
O
R
R
C
+
H
H
Enzyme
O
C
H+
Dehydration
Microbial uptake
H2N
OH
+
H
H
O
R
R
R
+
O
R
+
R
R
OH
H
O
H
N
H
H
O
O
R
R
+
OH
Amide Hydrolysis
HO
OH
O
Ester Condensation
O
H+ or OH-
H
NOM
R
NOM
R
Specify Starting
Molecules
Set Environmental
Parameters
Set time = 0 and calculate initial
reaction probabilities (all molecules)
For each molecule, test:
Does a reaction occur?
Stochastic
Synthesis:
Algorithm
Yes
No
When all molecules tested:
Calculate and store
aggregate properties
(at specific times)
No
Increment time step.
Simulation complete?
Yes
DONE
Transform molecule
Calculate new properties
and reaction probabilities
Hydrolysis and consumption of a protein
O
etc.
CH3
HN
NH
O
O
H2C
H3C
OH
HN
CH3
NH
O
O
pH 7.0, 0.1 mM O2, 24.8 oC, dark
Standard enzyme activities and
bacterial density
1000 molecules,
1000 hour simulation
HN
NH2
HO
O
O
8000
7000
# Molecules
6000
5000
# molecules
4000
3000
2000
Mn
1000
0
0
200
400
600
800
1000
Time (hours)
Simulation of protein hydrolysis and consumption
Triplicate runs, random seed = 1, 2, 3
1200
Mass C Consumed
3000000
2500000
2000000
1500000
1000000
500000
0
0
200
400
600
800
1000
Time (hours)
Simulation of protein hydrolysis and consumption
Triplicate runs, random seed = 1, 2, 3
1200
Reaction Count
3000
Hydrolysis
2500
2000
1500
Consumption
1000
500
0
0
200
400
600
800
1000
Time (hours)
Simulation of protein hydrolysis and consumption
Triplicate runs, random seed 1, 2, 3
1200
Can we convert terpenes, tannins
and flavonoids in soil into NOM ?
CH3
CH3
OH
O
OH
HO
O
CH3
H3C
O
OH
O
OH
OH
abietic acid
HO
O
O
OH
OH
HO
meta-digallic acid
OH
2000 molecules each
Atmospheric O2 (0.3 mM)
Acidic pH (5.0)
High oxidase activity (0.1)
~5.5 months
Bacterial density 0.01
dark
fustin
1600
1400
Mw
1200
MW
1000
800
Mn
600
400
200
0
0
1000
2000
3000
4000
Time (hours)
Evolution of NOM from small natural products in oxic soil
Final Mn = 612 amu, Mw = 1374 amu
5000
Elemental Composition
0.7
0.2
0.6
C
0.18
0.16
O
0.14
0.12
0.5
0.4
0.1
0.3
0.08
0.06
H
0.2
0.04
0.02
0.1
0
0
0
1000
2000
3000
4000
5000
Time (hours)
Evolution of NOM from small natural products in oxic soil
Final composition 54% C, 41% O, 5% H
0.6
0.5
Eq. Wt.
0.4
0.3
Aro.
0.2
0.1
0
1000
2000
3000
4000
0
5000
Time (hours)
Evolution of NOM from small natural products in oxic soil
Final Eq. Wt. = 247 amu, 11% aromatic C
Aromaticity
Equivalent Weight
500
450
400
350
300
250
200
150
100
50
0
600
30
Oxidations
Reaction Count
500
25
400
Condensations
20
300
15
200
10
Consumption
100
5
0
0
0
1000
2000
3000
4000
5000
6000
Time (hours)
Evolution of NOM from small natural products in oxic soil
Oxic soil incubation
of small natural products
increases Mw by 4X, acidity 2X, O content 30%
decreases aromaticity 57%  11%
oxidations enable consumption, condensation
Final composition similar to fulvic acid:
54% C, 41% O, 5% H
Mn = 612 amu, Mw = 1374 amu
Eq. Wt. = 247 amu, 11% ‘aromaticity’
How is this conversion to NOM affected by
lowering the O2 and oxidase levels?
OH
CH3
CH3
OH
O
OH
HO
H3C
O
O
CH3
O
OH
OH
abietic acid
HO
O
O
OH
OH
HO
meta-digallic acid
OH
2000 molecules each
Reduced O2 (0.1 mM)
Acidic pH (4.0)
Low oxidase activity (0.03)
~5.5 months
Bacterial density 0.01
dark
fustin
1400
1200
Mw
MW
1000
800
Mn
600
400
200
0
0
1000
2000
3000
4000
5000
Time (hours)
Evolution of NOM from small natural products in low-O2 soil
Final Mn = 528 amu, Mw = 1246 amu
Elemental Composition
0.8
0.08
C
0.7
0.075
0.6
H
0.07
0.5
0.065
0.4
O
0.3
0.06
0.2
0.055
0.1
0
0
1000
2000
3000
4000
0.05
5000
Time (hours)
Evolution of NOM from small natural products in low O2 soil
Final composition 67% C, 26% O, 7% H
1200
0.6
% Aromatic
0.5
800
0.4
600
0.3
Eq. Wt.
400
0.2
200
0.1
0
0
0
1000
2000
3000
4000
5000
Time (hours)
Evolution of NOM from small natural products in low O2 soil
Final Eq. Wt. = 1075 amu, 37% aromatic C
% Aromatic
Equivalent Weight
1000
100
Reaction Count
90
80
Consumption
70
60
50
40
30
20
Oxidation
Condensation
10
0
0
1000
2000
3000
4000
5000
Time (hours)
Evolution of NOM from small natural products in low O2 soil
Consumption ~30% lower, oxidation 7X lower,
condensation 30X lower than in oxic soil.
Low O2 soil incubation
of small natural products
increases Mw by 4X, H content 25%
decreases aromaticity 57%  37%
Final composition more reduced, higher UV ,
less charged (soluble) than fulvic acid:
67% C, 26% O, 7% H
Mn = 612 amu, Mw = 1374 amu
Eq. Wt. = 1075 amu, 37% ‘aromaticity’
Trial: Can we convert lignin and protein
molecules into NOM ?
CH3
O
O
O
O
HO
lignin fragment
H3C
O
etc.
O
H3C
Atmospheric O2 (0.3 mM)
Neutral pH (7.0)
Lower enzyme activity (0.01)
4 months reaction time
Moderate light (2x10-8 E cm-2 hr-1)
24.8 oC
Moderate bacterial density (0.02)
400 molecules lignin and protein
7000
6000
MW
5000
4000
3000
Mw
2000
1000
Mn
0
0
1000
2000
3000
Time (hours)
Evolution of NOM from lignin and protein in surface water
Final Mn = 902 amu, Mw = 1337 amu
(Mass distribution is log normal.)
4000
0.8
0.08
0.7
0.07
MW
0.6
0.06
C
0.5
0.05
0.4
0.04
O
0.3
0.03
N
0.2
0.02
0.1
0.01
0
0
0
1000
2000
3000
4000
Time (hours)
Evolution of NOM from lignin and protein in surface water
Final composition 45% C, 48% O, 5.2% H, 1.8% N
2500
0.6
2000
0.5
Aromaticity
0.4
MW
1500
0.3
Eq. Wt.
1000
0.2
500
0.1
0
0
0
1000
2000
3000
4000
Time (hours)
Evolution of NOM from lignin and protein in surface water
Final composition Eq. Wt. = 772 amu, 15% aromatic C
250
1200
C=C Oxidations
Reaction Counts
1000
C-OH Oxidation
200
800
150
600
100
400
Aldehyde Oxidation
50
200
0
0
1000
2000
3000
4000
0
5000
Time (hours)
Evolution of NOM from lignin and protein in surface water
Surface water degradation of biopolymers
Decreases Mn by 6X, aromatic C by 3X
Increases acidity 3X, O content 100%
Final composition similar to ‘hydrophilic’ NOM:
45% C, 48% O, 5% H, 1.8% N
Mn = 902 amu, Mw = 1337 amu
Eq. Wt. = 772 amu, 15% ‘aromaticity’
Stochastic synthesis
•Produces heterogeneous mixtures of
‘legal’ molecular structures
•Bulk composition (elemental %, acidity,
aromaticity, MW) similar to NOM
•Both condensation and lysis pathways
of NOM evolution are viable
Next Steps• Property prediction algorithms
– pKa, Kow, KCu-L
– UV, IR, nmr spectra
• Spatial and temporal controls
– Diurnal and seasonal changes
– ‘continuous reactor’
– Spatial modeling of soils, streams
• Data mining capabilities
Stochastic Synthesis of NOM
Cellulose
Lignins
Proteins
Cutins
Lipids
O2
light
bacteria
H+, OHmetals
fungi
NOM
Humic substances
& small organics
CO2
Tannins
Goal: A widely available, testable, mechanistic model
of NOM evolution in the environment.
Financial Support
NSF Division of Environmental Biology and
Information Technology Research Program
Collaborating Scientists
Steve Cabaniss (UNM)
Greg Madey (ND)
Jerry Leenheer (USGS)
Bob Wetzel (UNC)
Bob Wershaw (USGS)
Patricia Maurice (ND)
Laura Leff (KSU)