Bio 430: Chemicals in the environment - Oregon State University
Transcript of Bio 430: Chemicals in the environment - Oregon State University
Bio 430: Chemicals in the environment
Jeffrey JenkinsDepartment of Environmental and
Molecular ToxicologyOregon State University
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Chemical fate: transformation and transport within and between
Soil-Air-Water-Biota
Source: U.S. Geological Survey
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leach toward groundwater
plant uptake microbial or chemical
degradation
photodegradation
runoff
sorption to soil particles
volatilization
Chemical fate processes
wind erosion
washoff
interception
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sediments
water
atmosphere direct + indirect
photolysis
air/water exchange
wet + drydeposition
groundwaterinfiltration/exfiltration
sediment/waterexchange
chemical + biologicaltransformation
photodegradation
sorption to sediment and particleschemical + biological
transformation
runoff outflow
Chemical fate processes
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Chemical fate in the environment
Molecular interactions(physical-chemical properties, reactivities)
Environmental factors(Temperature, pH, light intensity, ion composition and strength,
microbial activity, natural organic matter, etc.)
Environmental processes(e.g. air/water exchange, sorption/desorption, chemical,
photochemical and biological transformation)
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Chemical fate in the environment
Transport and mixing processes
Dynamic behavior in a natural system(mathematical models and field investigations)
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Chemicals in the Environment
Initial distribution to environment (manufacture and use):emission in: air-soil-water-biota compartments
Transformation: degradation/metabolism
Redistribution- transport in and between compartments:
diffusion/advection-dispersion/mass transport
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Chemicals in the Environment
Understanding chemical fate, what scale?
Local scale: site-specific inputs, potential for off-site transport.
Watershed scale: integration of site-specific inputs and transport, particular emphasis on water quality.
Regional scale: integration of watershed-airshed chemical inputs and redistribution, long range transport of persistent compounds.
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Pesticides in the EnvironmentInitial distribution in the environment:method of applicationtiming of applicationfrequency of applicationamount of active ingredientformulation (other ingredients)
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Environmental Behavior of Pesticides in Soils
Initial distribution
Persistenceand
Mobility
Environmental Fate
temperature
soil pH
soil texture
sunlight
organic matter
moisture
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Pesticide Fate and Transport
Physical-chemical properties:
• Water solubility• Vapor Pressure• Kd (soil/water partition coefficient)• Henrys Law Constant• Soil half-life• Foliar half-life
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Soil sorption
soil particlesoil water
K
K describes the relationship between pesticide sorbed to soil particles and pesticide dissolved in soil water.
concentration of pesticide sorbed to soil
concentration of pesticide in solution
d
d
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Soil sorption
To account for different soil types and organic matter content the Kd is normalized for % organic carbon.
doc *
KK% organic carbon
=
* decimal equivalent
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Soil Properties that Influence Leaching and Runoff
• Permeability • Water table conditions• Organic matter content• Clay content
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Course textured soils and other soil conditions thatresult in preferential flow paths must also be considered.
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Pesticides in surface water
Mass transfer primarily in the dissolved phase, will vary with pesticide’s solubility in water and soil sorption.
soil particlewater
concentration of pesticide sorbed to soil
concentration of pesticide in solution
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Partitioning between soil compartments(soil, water air)
soil particle
soil water
K
K describes the relationship between pesticide concentration in soil water and pesticide concentration in air.
K
air
chemicalin air
Chemical in water
h
h
d
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Volatile loss as Percent Applied
Pesticide Application Rate(kg a.i./Ha)
Vapor Pressure(mPa @ 25 oC)
24 hr Volatile lossas % Applied
Chlorpyrifos 1.9 2.50 16.5
Ethofumesate 2.5 0.650 6.3
Triclopyr (acid) 1.1 0.170 4.5
Triadimefon 3.1 0.060 2.1
Propiconazole 2.2 0.056 1.1
Cyfluthrin 0.2 0.004 ND
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Pesticide Fate
• Field dissipation: sum of chemical and biological processes including:
– Chemical degradation1
– Biological degradation (microbial + plant)1
– Photodegradation2
– Volatilization
1Approximated with a 1st order rate constant2Approximated with a psuedo 1st order rate
constant
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Pesticide degradation half-life
Half-life = the amount of time it takes the parent compound to decay to half its original amount
Half-life in an environmental compartment: (soil-air-water-biota) sum of all degradation and transport pathways
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Pesticide degradation half-life
No of ½ lives
% amount remaining
3.3 106.6 110 0.1
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Sunlight photolysis of an aqueous suspension of nitrofen
OCl
Cl
NO2
OHCl
Cl
OHCl
OH
OCl
Cl
NH2 OH NH2 OH NH2
OH
OCl
Cl
O
Cl
ClN N
OH OH
OH OH
OH
POLYMER
nitrofen
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Chemical and microbial degradation of chloroanilines
NH2
Cl
NH2
Cl
OH
Cl
OH
OHCl
CHOCOOH
OHCl
COOHCOOH
Cl
CO2
OH2
COOH
COOH
Cl
OO COOH
O
HOOC
COOH
O2
O2
A. faecalis
Ps. diminuta
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Aldicarb degradation pathways and LD50 values (rat acute oral)
NO
O NSCH3
CH3
CH3CH3
NO
O NSCH3
CH3
CH3CH3
O
NO
O NSCH3
CH3
CH3CH3
O
O
NS
CH3
CH3
CH3OH N
SCH3
CH3
CH3
NS
CH3
CH3
CH3
O
OH NS
CH3
CH3
CH3
O
NS
CH3
CH3
CH3
O
OOH
NS
CH3
CH3
CH3
O
O
Aldicarb0.9 mg/kg
sulfone24 mg/kg
sufoxide oxime8060 mg/kg
sulfone oxime1590 mg/kg
oxime2380 mg/kg
nitrile570 mg/kg
sulfoxide0.9 mg/kg sulfone nitrile
4000 mg/kg
sulfone nitrile350 mg/kg
H20
H20
H20
O2 , fast
O2
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Pesticide Properties used to evaluate fate in the Environment
water solppm
Kocml/g
Vaporpressure
mm Hg
soil 1/2 life
days
foliar 1/2 life
days
Atrazine 33 100 2.90E-07 60 5
Diuron 42 480 6.90E-08 90 30
MCPA ester 5 1000 1.50E-06 25 8
pendimethalin 28 5000 9.40E-06 90 30
triclopyr ester 23 780 1.26E-06 46 15
carbaryl 120 300 1.20E-06 10 7
chlorpyrifos 0.4 6070 1.70E-05 30 3
malathion 130 1800 8.00E-06 1 3
esfenvalerate 0.002 5300 1.10E-08 35 8
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Chemical fate determines exposure to humans and aquatic life
leach toward groundwater
plant uptake microbial or chemical
degradation
photodegradation
runoff
sorption to soil particles
volatilization
Chemical fate processes
wind erosion
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13.4 million lbs of pesticides used annually in OregonWhat are the risks and who decides?
Federal Insecticide, Fungicide, and Rodenticide Act regulates pesticide manufacture, use, storage, and disposal (benefit-risk balancing statute.)
Under Authority of the Clean Water Act, ODEQ has the authority to set pesticide water quality standards for waters of the state (TMDLs).
Under the Endangered Species Act NMFS and USFWS have the authority to set rules deemed necessary to prevent more species declines under a provision called “Four D.”
EPA, NMFS, and USFWS have “overlapping” jurisdiction with regards to pesticide use and the Endangered Species Act.
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EPA Risk Assessment
Risk = f (exposure, toxicity)
Source: Purdue University Pesticides Program
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Pesticide Risk Assessment
RFD: The Reference Dose is the amount of a pesticide residue a person could consume daily for 70 years with no harmful non-cancereffects.
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Pesticide Risk Assessment
The RFD is determined by dividing the NOAEL by a safety factor, usually between 100 and 1000,
to account for uncertainty in extrapolating from animal studies and to protect sensitive individuals, including infants and children.
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Quantitative Assessment of Health Risks of Pesticides in Drinking Water
MCL - The Maximum Contaminant Level permissible in water which is delivered to any user of a public water system (Safe Drinking Water Act; ~50 pesticides have MCLs)
HA - Health Advisory: EPA guidance for drinking water contaminants based on lifetime exposure and non-carcinogenic endpoints. HA is derived from the DWEL.
DWEL - Drinking Water Equivalent Level, based on the Reference Dose (RfD) and assuming 70 Kg person drinks 2 liters per day over a lifetime. The DWEL has been adjusted assuming that drinking water comprises 20% of the allowable daily intake.
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Pesticide Risk Assessment: Wildlife
What is the toxicity of the pesticide and it’s degradates to wildlife?
Acute toxicity (high dose-short exposure)
Chronic toxicity (low dose-long exposure)
Most sensitive adverse effect
Sensitive sentinel species
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EPA Pesticide Aquatic Risk: Wildlife Toxicity Assessment
• Laboratory tests are used to determine the NOAEL in representative species.
• The hazard quotient is the ratio of the NOAEL to the expected environmental concentration.
• If the hazard quotient is greater than 1.0, the potential exists for adverse ecological effects.
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Use of models for evaluating hazards associated with chemicals in the
environment
Models use a systems approach to understanding complex phenomenon.
Computer based environmental models present a conceptual framework and a mathematical formulation of fate and transport between compartments (soil, air, water, biota) based upon scientific principles.
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Environmental fate models
PRZM and EXAMS (EPA)CalTOX (California EPA)Fugacity Model Levels I, II, III (Mackay)Gaussian plume models (EPA, NOAA)
http://www.lanl.gov/orgs/d/d4/movies.shtml
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How Do We Assess Risk?Follow the National Academy of Sciences (NAS)
four-step risk assessment paradigm*:
HazardIdentification
Risk Characterization
ExposureDose-
Response Assessment
* From the National Research Council’s Risk Assessment in the Federal Government: Managing the Process, 1983.