Determining the Fate and 

Transport of Pesticide Emissions 

in the Chesapeake Bay Region

Laura L. McConnell

Cathleen J. Hapeman

Cody J. Howard

U.S. Dept. of Agriculture

Agricultural Research Service

Beltsville, MD

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Beltsville Agricultural Research Center

 Largest, most diversified agricultural research 

complex in the world

 Research laboratories focus on: 

 Plant Sciences

 Animal Science and Health

 Natural Resource Management and Protection

 Human Nutrition

2  National Arboretum (Washington, DC)
Motivation

 Chesapeake Bay Region: 

Ecosystem Health Decrease 

 Eutrophication

 Toxicity

 Decrease in biodiversity

 Restoration: 

Presidential Executive Order 13508

 Use expertise and resources to improve 

health: Local, State, and Federal agencies 

and others

 Adaptive management – utilize more 

effective monitoring and modeling

 Includes milestones

 FLC developed the Strategy for 

Protecting and Restoring the 

Chesapeake Bay Watershed 3
Background – Sources of Air Pollutants

 Urban

NOx, VOCs, and PM

 Rural Animal agricultural operations

PM, VOCs, SVOCs, ammonia

 Pesticide Applications

 Legacy and current use pesticides 

measured in air and rain samples

 Inert – VOCs

 Active ingredient - SVOCS

 Regulated by the CADPR, other states 

to follow

 Biogenic

VOCs, SVOCs, PM

 Forms

Ozone and PM

4
Research – Objective & Approach

Objective - Discern the chemical nature, fate, and transport of 

critical agricultural pollutants emitted to the atmosphere 

and consider the potential risks posed by reactivity and/or 

deposition of these chemicals to sensitive ecosystems. 

Approach

 Measure Ambient Concentrations

 Legacy and current use pesticides

 Urban and rural organic pollutants

 Ozone, NOx, ammonia, and PM10

 Estimate emissions at smaller grid size with Pesticide 

Emissions Model (PEM)

 Determine fate and transport of selected gases using 

- Community Multi-scale Air Quality Model (CMAQ)

- EPAs high performance computer cluster with AMAD (RTP, NC)

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VOC and Pesticide Emissions

 VOCs in formulated 

pesticides are common 

solvents 

 The characterization of the 

formulants is proprietary

 Six different pesticide 

products containing organic 

solvents were analyzed by 

TGA and by GC-MS

 Herbicides H1 & H2

 Fungicides F1 & F2

 Insecticides I2 & I2

TA Instruments

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VOC and Pesticide Emissions

 CA DPR regulating VOC emissions

 Recent manuscript details different methods

Zenali et al. 2010. Atmospheric Environment, in review

0.0

15.0

30.0

45.0

60.0

75.0

H1 H2 F1 F2 I1 I2

VOC or Active Ingredient (%)

Pesticide Product

TGA

GC-MS

Active Ingredient

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VOC and Pesticide Emissions

 Gases emitted during TGA were analyzed in near real-time 

using FTIR

 FTIR spectral intensity were compared to GC-MS data

0

10

20

30

40

50

60

0.00

0.01

0.02

0.03

0.04

0.05

0.06

33 46 58 71 83 96 108 115

FTIR Intensity (mV)

TGA Mass Loss (%)

Intensity

2,2-dimethyl-1,3-dioxolane-4-ethanol

2-Octanone or 2-Nonanone

1,2-Propanediol

Acetophenone

TGA Mass Loss

F1

115

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Methods – Field Measurements 

 Three representative sites

 Pesticides measured using 

high volume samplers

 VOCs measured using 

thermal desorption tubes

 PM measured using filters

 Collaboration

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Methods – What is PEM?

 Developed by M. Trevor Scholtz

 Scholtz 2002a, 2002b and Cooter 2002a, 2002b

 Inputs: soil concentration, soil property, soil 

moisture, and meteorological data

 Calibration

 Multi-year study of pesticide fate data from 

USDA-ARS, Beltsville (J. Prueger, T. Gish)

 Develop emissions inventories for pesticides 

during selected years of study

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Results - PEM

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Results - PEM

Scholtz et al., Interpretation Center Final Report to EPA, March 1999

Results represent 

gridded atrazine

emissions from 

PEM only

36 x 36 km grid cell 

resolution

We will use 4 x 4 or 

8 x 8 km

Smaller Area

Pin point areas 

of interest

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Methods - CMAQ

 Community Multi-scale Air 

Quality Model 

 Inputs

 MET (MM5 or WRF)

 Emissions inputs

 Calibration - Compare against 

observed measurements 

 Determine fate and transport 

of selected chemicals 

- Biogenic and urban emissions will 

be incorporated

Weather Data

Met Model 

(WRF or MM5)

Emission Inventory 

(Including PEM output)

SMOKE 

(Emissions Processor)

CMAQ Model

Hourly Gridded 

Chemical Concentrations

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Conclusions

 TGA analysis can provide pesticide emissions data

 For inert and active ingredients

 Using PEM to predict pesticide emissions in a 

more focused region with smaller grid sizes

 Once PEM is integrated into CMAQ, hourly 

gridded chemical concentrations of pesticide and 

pesticide VOC concentrations will be determined

 Help to determine fate and transport of pesticides

 First year of a five year program underway; 

currently looking for additional funding from our 

collaboration partners

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Thank You! Any 

Questions?

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References

Cooter, E.J. and Hutzell, W.T., 2002. A regional atmospheric fate and 

transport model for atrazine. 1. Development and implementation. 

Environmental Science & Technology 36 (19), 4091-4098.

Cooter, E.J., Hutzell, W.T., Foreman, W.T. and Majewski, M.S., 2002. A 

regional atmospheric fate and transport model for atrazine. 2. Evaluation. 

Environmental Science & Technology 36 (21), 4593-4599.

Scholtz, M.T., Voldner, E., McMillan, A.C. and Van Heyst, B.J., 2002a. A 

pesticide emission model (PEM) Part I: model development. Atmospheric 

Environment 36 (32), 5005-5013.

Scholtz, M.T., Voldner, E., Van Heyst, B.J., McMillan, A.C. and Pattey, E., 

2002b. A pesticide emission model (PEM) Part II: model evaluation. 

Atmospheric Environment 36 (32), 5015-5024.

Scholtz et al., Hourly Gridded Atrazine Emissions from the Canadian Global 

Emissions Interpretation Center, Final Report to the EPA, March 1999

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