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Soil Microbiological Activities in Vegetative Buffer Strips and Their Association with Herbicide Degradation
By
C.H. Lin, R.N. Lerch, R.J. Kremer, H.E. Garrett, U. Ranjithand M.F. George
Recent Studies Regarding Herbicides and Health,
Ecological and Social & Economic Impacts • Public Heath ImpactThe men living in the Mid Missouri, as compared to other U.S. urban areas, tend to have poorer
sperm quality and lower sperm counts. (Dr. Swan et al. 2003)The lower sperm quality and counts strongly associated with the higher herbicides residue
levels (alachlor, atrazine) in their urine samples. (Dr. Swan et al. 2003; Center for Disease Control and Prevention 2003)
(None of the men in the study worked at or lived next to farms)
• Ecological ImpactFrogs exposed to atrazine in the reservoir near Midwest states developed reproductive
deformity (hemaphroditic; mixtures of ovaries and testes) (Dr. Hayes et al. 2003).
• Social & Economic ImpactTo comply drink water regulation, St. Louis County estimated the costs of compliance for their
five drinking water treatment plants by the installation of granular activated carbon at a capital cost of $164 million, with operation and maintenance costs of $7 million per year.
Our Mission
• To optimize the riparian buffer designs in agroforestry systems to reduce the herbicide transport from nearby agricultural lands before they reach the reservoirs or drinking water sources
• To develop the recommendations (species selection and biodegradation agents) and cost-effective management plans to enhanced the degradation of trapped herbicides within buffers
Effectiveness of Grass Buffer Designs in Reducing
Herbicides Transport in Surface Runoff
(University of Missouri Bradford Research Center)
Atrazine Transport in Surface Runoff
0
20
40
60
80
100
120
-2 0 2 4 6 8 10
Distance from Source Area (m)
Rel
ativ
e A
traz
ine
Loa
d (%
)
Fallow_Control
Tall Fescue
Hedge+TallFescue
Hedge+Native
Metolachlor Transport in Surface Runoff
0
20
40
60
80
100
120
-2 0 2 4 6 8 10
Distance from Source Area (m)
Rel
ativ
e M
etol
achl
or L
oad
(%) Fallow_Control
Tall Fescue
Hedge+TallFescue
Hedge+Native
Glyphosate Transport in Surface Runoff
0
20
40
60
80
100
120
140
-2 0 2 4 6 8 10
Distance from Source Area (m)
Rel
ativ
e G
lyph
osat
e L
oad
(%) Fallow_Control
Tall Fescue
Hedge+Native
Further Consideration
A robust buffer design needs to rapidly degrade the deposited & intercepted herbicides before they have a chance to be released to surface and subsurface flow.
Site of Lysimeter Project at University of MissouriSite of Lysimeter Project at University of Missouri
Percent of Atrazine Degradation Products in Soil
0
10
20
30
40
50
60
70
80
90
Bare ORCH TALL TIMO SMOO SWITGrass Treatm ents
% o
f Atra
zine
Deg
rada
tion
Prod
ucts
DIHA
DEHA
HA
DIA
DEA
40
50
60
70
80
90
100
0 100 200 300
Microbial Biomass C (gC/g Soil)
Deg
rada
tion
(%)
%Degradation Correlation Coefficient = 0.58 p = 0.015
Microbial Biomass C vs. Atrazine Degradation in Soils
Contour Buffers Watershed Project
Control-traditional corn-soybean rotation
Grass Contour Buffer-redtop, brome grass and birdfoot trefoil
Agroforestry Contour Buffer- pin oak, white oak, bur oak and same mixture of grasses
Objectives (Phase I)
• *To evaluate the effect of vegetation buffers and topographic factors on soil enzymatic activities and their association with herbicides degradation
• To evaluate the effects of the contour buffers on herbicides transport and transformations in sub-surface flow.
NH
N N
N
Cl
NH
NH
N N
N
OH
NH
NH
N N
N
Cl
NH2
NH
N N
N
OH
NH2
NH2
N N
N
OH
NH
NH2
N N
N
Cl
NH
NH2
N N
N
Cl
NH2
NH2
N N
N
OH
NH2
Atrazine Degradation Pathways
Atrazine
Deethylatrazine
Deisopropylatrazine
Didealkylatrazine
Ammeline
Hydroxyatrazine
Deethylhydroxyatrazine
Deisopropylhydroxyatrazine
N-Dealkylation
Chemical orPhotochemical Hydrolysis
(ATR)
(DEA)
(DIA)
(HA)
(DEHA)
(DIHA)
Measured Enzymatic Activities
1. Fluorescein Diacetate Hydrolytic (FDA) Activity (proteases, lipases, and esterases)
2. Dehydrogenase Activity (dehalogenation, biological oxidation)
3. -Glucosidase Activity (carbon utilization efficiency)
Contour Buffers Watershed Project
Control-traditional corn-soybean rotation
Grass Contour Buffer-redtop, brome grass and birdfoot trefoil
Agroforestry Contour Buffer- pin oak, white oak, bur oak and same mixture of grasses
E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope
Control
Grass Buffer Agroforestry
E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope
0
50
100
150
200
250
300
E1 E2 E3 E4 E5 E6
Control (A)Agroforestry (B)Grass (C)
Microbial Enzymatic Potential for Herbicides Degradation[Fluorescein Diacetate Hydrolytic Activity (FDA; mole g-1 h-1)]
E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope
0
2
4
6
8
10
12
14
16
E1 E2 E3 E4 E5 E6
Control (A)Agroforestry (B)Grass (C)
Dehydrogenase Activity (mole g-1 h-1)
E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope
0
0.5
1
1.5
2
2.5
3
3.5
4
E1 E2 E3 E4 E5 E6
Control (A)Agroforestry (B)Grass (C)
-Glucosidase Activity (mole g-1 h-1)
E1, E2: summitE3: shoulder slopeE4: back slope E5: foot slopeE6: toe slope
14CO2 Trap
HPLC-FSA
Microbial Mineralization Rates of Atrazine vs. Microbial Enzymatic Activity
0
1
2
3
4
5
6
7
8
9
10
Mic
robi
al M
iner
aliz
atio
n R
ates
(%
app
lied
14C
))
0
1
2
3
4
5
6
7
8
9
10
Mic
robi
al E
nzym
atic
Act
ivity
14CO2 Evolution
FDA (0.494)*
dehydrogenase (0.763)
B-Glucosidase (0.857)
* correlation coefficient
• Contour vegetative buffer across the landscape showed significantly increased soil enzyme activities compared to cropped control treatment.
• Soils collected from grass buffers showed the highest microbial enzymatic activities and herbicide degradation potential.
• Topographic positions did not significantly affect soil microbial enzymes activities in this study.
• The preliminary results from growth chamber study suggested dehydrogenase and -Glucosidase activities showed promise as useful tools for evaluating the overall herbicide bioremediation potential of various vetetative buffer designs.
Conclusions
Current Efforts
Glyphosate and Its Metabolite
P NHOHO
HO O
O-
P NH2OHO
HO
Glyphosate
Aminomethylphosphonic acid (AMPA)
Turbo-Ion Spray LC-MS/MS
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