Evaluating Effectiveness of Species Selection and Grass Buffer Designs in Herbicides Mitigation

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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. Ranjith and M.F. George
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Recent Studies Regarding Herbicides and Health,
Ecological and Social Economic Impacts

• Public Heath Impact
• The 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 Impact
• Frogs 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 Impact
• To 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.

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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

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Effectiveness of Grass Buffer Designs in Reducing
Herbicides Transport in Surface Runoff
(University of Missouri Bradford Research Center)
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Atrazine Transport in Surface Runoff
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Metolachlor Transport in Surface Runoff
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Glyphosate Transport in Surface Runoff
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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.

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Site of Lysimeter Project at University of
Missouri
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Microbial Biomass C vs. Atrazine Degradation in
Soils
Correlation Coefficient 0.58 p 0.015
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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.

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(ATR)
(DEA)
(HA)
(DIA)
(DEHA)
(DIHA)
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Measured Enzymatic Activities

• Fluorescein Diacetate Hydrolytic (FDA) Activity
  (proteases, lipases, and esterases)
• Dehydrogenase Activity (dehalogenation,
  biological oxidation)
• b-Glucosidase Activity (carbon utilization
  efficiency)

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Control
E1, E2 summit E3 shoulder slope E4 back slope
E5 foot slope E6 toe slope
Grass Buffer
Agroforestry
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Microbial Enzymatic Potential for Herbicides
Degradation Fluorescein Diacetate Hydrolytic
Activity (FDA mmole g-1 h-1)
E1, E2 summit E3 shoulder slope E4 back slope
E5 foot slope E6 toe slope
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Dehydrogenase Activity (mmole g-1 h-1)
E1, E2 summit E3 shoulder slope E4 back slope
E5 foot slope E6 toe slope
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b-Glucosidase Activity (mmole g-1 h-1)
E1, E2 summit E3 shoulder slope E4 back slope
E5 foot slope E6 toe slope
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14CO2 Trap
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HPLC-FSA
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Microbial Mineralization Rates of Atrazine vs.
Microbial Enzymatic Activity
correlation coefficient
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Conclusions

• 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 b-Glucosidase
  activities showed promise as useful tools for
  evaluating the overall herbicide bioremediation
  potential of various vetetative buffer designs.

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Current Efforts
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Glyphosate and Its Metabolite
Glyphosate
Aminomethylphosphonic acid (AMPA)
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Turbo-Ion Spray LC-MS/MS
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