OFFICE OF

CHEMICAL SAFETY AND 

POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

PC Code: 129026

DP Barcode: D423306

Date: February 10, 2015

MEMORANDUM

SUBJECT: Tebufenozide Drinking Water Assessment for Registration Review

TO: Christina Scheltema, Chemical Review Manager

Avivah Jacob, Team Leader

Patricia Parrott, Branch Chief

Pesticide Re-Evaluation Division (7508P)

Mohsen Sahafeyen, Chemist

Donna Davis, Acting Branch Chief

Risk Assessment Branch VI

Health Effects Division (7509P)

FROM: James N. Carleton, PhD, Senior Scientist

Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

REVIEWED Cheryl Sutton, Ph.D., Environmental Scientist

BY: Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

APPROVED Jean Holmes, DVM, MPH Branch Chief

BY: Environmental Risk Branch IV

Environmental Fate and Effects Division (7507P)

EXECUTIVE SUMMARY

A screening-level drinking water assessment (DWA) for tebufenozide was conducted in 

support of registration review. Tebufenozide (benzoic acid, 3,5-dimethyl-1-(1,1-dimethylethyl)-

2-(4-ethylbenzoyl) hydrazide) is an insect growth regulator belonging to the diacylhydrazine 

class of insecticides that interfere with the binding of the endogenous steroidal molting hormone 

20-hydroxyecdysone with its receptor protein complex, inducing a precocious incomplete molt in 

insect larvae, particularly lepidopterans (Dhadilla et al. 1998; Shimizu et al. 1997). 

Tebufenozide is used as an insecticide on a variety of forestry, fruit, vegetable, orchard and 

ornamental crops. Current tebufenozide labels include uses on bushberries, cane berries, canola, 

citrus, tree nut crops (almonds, pecans, walnuts), other nuts, brassica vegetables, cotton, 
2

cranberries, fruiting vegetables, mint, ornamentals, pome fruits, sugarcane, trees/forests/shrubs, 

and pasture/rangeland. 

The maximum annual application rate of tebufenozide is for fruiting vegetables, mint and 

ornamental uses, at 2.0 lbs a.i./A. The maximum chronic and cancer surface water estimated 

drinking water concentrations (EDWCs) are associated with the fruiting vegetables use, however 

the maximum acute EDWC is associated with the use on sugarcane at the lower annual rate of

1.0 lbs a.i./A/yr. The computer models PRZM and EXAMS, as implemented in EFED’s Surface 

Water Concentration Calculator (SWCC), were used to generate surface water EDWCs for use in 

the human health dietary risk assessment, while the Pesticide Root Zone Model for Groundwater 

(PRZM-GW) and Screening Concentration in Ground Water (SCI-GROW) models were used to 

generate groundwater EDWCs. A Provisional Cranberry Model was also used to generate 

surface water EDWCs. 

According to a memorandum from Mohsen Sahafeyen dated October 2, 2014 (DP 

423156), the chairperson (Christine Olinger) and a senior member (Ray Kent) of the Health 

Effects Division’s (HED) Residues of Concern Knowledge-Base Subcommittee (ROCKS) met 

with other members of HED and EFED on September 29, 1014. The group concluded that 

tebufenozide and its major degradates RH-112651, RH-112703 and RH-96595 are Residues of 

Concern (ROC) in surface water-derived drinking water. Although the group could not ascertain 

that any of the three degrades were less toxic than the parent, the group concluded that in 

groundwater only tebufenozide and metabolite RH-112651 are of concern, based upon the 

rationale that because the other two degradates (RH-112703 and RH-96595) were below 10% of 

applied radioactivity specifically in the submitted aerobic soil studies, these entities would not be 

expected to constitute “major” degradates in groundwater. However, after conducting a full 

exposure assessment EFED has included the parent and three degradates in the groundwater 

assessment. A Total Toxic Residues (TTR) approach was employed to model both ground and 

surface water, in which TTR comprises parent tebufenozide plus all three of its major 

metabolites (RH-112651, RH-112703 and RH-96595). In surface water TTR was conservatively 

modeled as a single conceptual entity with SWCC and with the Provisional Cranberry Model, 

using an aerobic soil half-life representing the degradation of parent plus all three degradates, 

and a soil sorption coefficient (KOC) reflecting one of the (more mobile than parent) degradates, 

for which data were available. Unlike surface water, groundwater modeling (using PRZM-GW)

was “refined,” by simulating parent and the three summed degradates as separate entities, then 

combining their resulting EDWCs to represent TTR. 

The maximum EDWC values recommended for use in the human health dietary risk 

assessment are 116.4 μg/L for acute EDWC and 107.2 ug/L for chronic and cancer EDWCs.

For surface water sources of drinking water, the maximum (1-in-10 year return frequency daily) 

acute EDWC, associated with the use of tebufenozide on sugarcane (by ground application), is

51.8 μg/L. The maximum chronic (1-in-10 year return frequency annual mean) and cancer (long 

term mean) EDWCs, associated with the use of tebufenozide on fruiting vegetables (by aerial 

application), are 3.13 μg/L and 2.19 μg/L respectively. The maximum acute groundwater 

EDWC from PRZM-GW is 116.4 μg/L associated with tebufenozide’s use on fruiting 

vegetables, mint and ornamentals. The corresponding chronic and cancer (long-term mean) 

EDWC from PRZM-GW is 107.2 μg/L, and the SCI-GROW EDWC is 1.18 μg/L. Surface water 

EDWCs generated using the Provisional Cranberry Model are strikingly similar to the PRZMGW results, with a chronic value of 105.8 μg/L. These (cranberry model) results are presented 
3

for illustrative purposes only, given the model’s provisional status. The bolded values presented 

in Table 1 are recommended for use in the human health dietary risk assessment. Selected 

model results are provided in Appendix A. 

Table 1. Maximum EDWCs of tebufenozide Total Toxic Residues.

Drinking Water

Source (Model Used)

Use (rates 

modeled)

Maximum Estimated Drinking Water Concentration

(EDWC) 

Acute (μg/L) Chronic (μg/L) Cancer (μg/L)

Surface water

(SWCC; 

LAsugarcaneSTD 

scenario, ground 

application for acute; 

FLpeppersSTD 

scenario, ground 

application for chronic 

and cancer)

Sugarcane (4 apps at 

0.25 lbs a.i./A, 10 

day RTI); fruiting 

vegetables (8 apps at 

0.25 lbs a.i./A, 10 

day RTI)

51.8 3.13 2.19

Surface water

(Provisional Cranberry 

Model)

Cranberries

(4 apps at 0.25 lbs 

a.i./A, 7 day RTI)

279.3 105.8  ̄

Groundwater (PRZMGW)

Fruiting vegetables, 

mint, ornamentals 

(WI sands) 

(2.0 lb a.i./A/yr: 8 

apps at 0.25 lbs 

a.i./A, 10 day RTI)

116.4 107.2 107.2

PROBLEM FORMULATION

This is a screening-level drinking water assessment (DWA) that uses modeling to 

estimate surface water and groundwater concentrations of pesticides in drinking water source 

water (pre-treatment), resulting from pesticide use on sites that are contamination-vulnerable. 

Screening-level DWAs are designed to eliminate the need for further scrutiny of chemicals with 

low potential for posing a drinking water concern. This assessment is based on available 

environmental fate data. There are no significant data gaps in the environmental fate database. 

There is little existing monitoring data for tebufenozide in water or sediment, and no detections 

above quantitation limits.

ANALYSIS

Use Characterization

Tebufenozide was initially registered for use on walnuts and pecans in 1994 (USEPA 

1994). In February 1999, the Agency completed a screening-level ecological risk assessment 

(USEPA 1999) in support of the Section 3 Registration on pome fruit, cotton, walnuts, cole 

crops and leafy vegetables, sugarcane, fruiting vegetables, forests, trees, shrubs and ornamentals. 

Following the Section 3 registration in 1999, additional new uses resulted in risk assessments for 

a special local need (Section 24c) use of tebufenozide on pasture/rangeland (D259984) in Texas 
4

in 1999, a Section 3 registration for use on tree nuts and almond hulls (D255779) in 1999, a 

Section 3 registration for use on tree nuts (D255795) in 2000, and on citrus (D270058) in 2004. 

Three Inter-regional 4 (IR-4) minor use registrations have been evaluated for tebufenozide on 

blueberries, cranberry, turnip, mint, canola and cane berries (D247304) in 1998, on sweet 

potatoes (D285367) in 2003, and on grapes (D285026; D285365) in 2003. Additionally, Section 

18 emergency use exemptions have been granted to control lepidopterous pests on cotton in 

Arkansas (D216767), Texas (DP Bard D216754) and Tennessee (D216767) in 1995; leafy 

vegetables in Texas (D231454) and sugarcane in Louisiana (D226011) in 1996; peppers in 

Georgia (no DP Barcode) in 1997; cranberries in New Jersey (D244220), Washington 

(D243302) and Massachusetts (D245577) in 1998- and grapes in Virginia (D274766) in 2001. A 

comprehensive list of currently registered tebufenozide uses, along with their application rates

and retreatment intervals, is given in Table 2.

Table 2. Methods and rates of application of currently registered uses of tebufenozide.

Use Scenario Application 

Type

Maximum 

Single 

Application 

Rate

(lbs a.i./A)

Maximum # 

of apps/yr

RTI

(days)

Maximum 

Annual 

Application 

Rate

(lbs a.i./A)

Bushberries, Cane 

berries Ground, aerial 0.25 Not specified 10 1.0

Canola Ground, aerial 0.25 Not specified 10 1.0

Citrus Ground, aerial 0.25 Not specified 14 1.25

Brassica vegetables Ground, aerial 0.12 Not specified 10 1.8

Cotton Ground, aerial 0.25 Not specified 10 1.0

Cranberry Ground, aerial 0.25 4 7 1.0

Fruiting vegetables Ground, aerial 0.25 Not specified 10 2.0

Mint Ground, aerial 0.25 Not specified 10 2.0

Ornamentals Ground, aerial 0.25 Not specified 10 2.0

Pome fruit Ground, aerial 0.31 Not specified 10 1.875

Sugarcane Ground, aerial 0.25 Not specified 10 1.0

Almonds, Walnuts Ground, aerial 0.47 Not specified 10 1.9

Pecans Ground, aerial 0.26 Not specified 8 1.9

Other nuts Ground, aerial 0.47 Not specified 10 1.9

Trees, Forests, Shrubs Ground, aerial 0.12 Not specified 5 0.25

Pasture, rangeland Ground, aerial 0.125 4 10 0.5

Environmental Fate Characterization

Parent tebufenozide is characterized as persistent to very persistent1, with laboratory halflives that range up to 179 days. Based upon limited data tebufenozide’s major degradates (RH112651, RH-112703 and RH-96595) appear to be somewhat less persistent than the parent, with 

calculated half-lives for summed degradates ranging from 29.3 to 123.8 days in aerobic soil 

studies conducted using applied parent chemical (under which conditions the decay of degradates 

is confounded by their simultaneous formation from the parent compound). Microbially-

 

1 Based on the Toxic Release Inventory classification system where half-lives greater than 60 days in water, soil, 

and sediment are considered persistent and half-life greater than 6 months are considered very persistent (USEPA, 

2012a)
5

mediated degradation is the primary dissipation pathway for parent tebufenozide. Parent 

tebufenozide is stable to hydrolysis (pH 5-9) and is expected to be stable to aqueous photolysis

based on its UV absorbance spectrum. The compound is also relatively stable to indirect 

photolysis in pond water (t1⁄2 = 67 days) and on soil (t1⁄2 = 98 days). No abiotic degradation data 

are available on any of the major degradates. In an aged soil column leaching study, the parent 

compound was present in four soils at approximately 52-71% of the applied after 30 days of 

aerobic aging. In terrestrial field studies, parent tebufenozide dissipated with half-lives of 39-53 

days. Bioaccumulation studies show that the BCF for tebufenozide in fish was 151X for wholefish tissue and showed 90% depuration within 15 days.

Tebufenozide is classified as moderately mobile based on batch equilibrium based Koc

values (351-894 mL/gOC) and using the Food and Agricultural Organization (FAO) soil mobility 

classification scheme. The carboxylic acid metabolite RH-112651 is classified as mobile to 

moderately mobile under the FAO scheme based on its Koc values (76-156 mL/gOC). A second 

carboxylic acid metabolite, RH-112703, and the ketone metabolite RH-96595, are also mobile 

based on column leaching study results. Thus, the parent compound and all three major

degradates have the potential to contaminate surface water via runoff from treated areas after 

application, through subsurface (e.g., tile drain) flow, and as a consequence of spray drift during 

application. Tebufenozide and its degradates also have the potential to leach to groundwater. 

General physical/chemical properties are summarized in Table 3 and submitted environmental 

fate data for tebufenozide and its major degradates are summarized in Table 4.

Table 3. General physical and chemical properties of tebufenozide

Property Value(s) Source

Molecular weight (g/mol) 352.48 MRID 424362-01, 424412-01

Vapor pressure (Pa; at 25C) 3 x 10-6 U.S. EPA, 1993

Water solubility (mg/L; at 

25C) 0.83 mg/L U.S. EPA, 1993

Henry’s Law Constant (atmm3

/mol; at 25C) 4.0 to 5.1 x 10-7 U.S. EPA, 1993

Octanol-water partition 

coefficient (Kow)

17,906 (log Kow 4.25) U.S. EPA, 1993

Fish Bioconcentration Factor 16x (edible)

333x (nonedible)

151x (whole fish)

424362-09

429312-24

Table 4. Environmental fate parameters of tebufenozide

Parameter Value(s) Source/Comments

Persistence (days)

Hydrolysis half-lives (23-25C) (days) stable (pH 5)

stable (pH7)

stable (pH 9)

424362-04

Aqueous photolysis half-life (25C) stable 424362-05
6

Parameter Value(s) Source/Comments

Soil photolysis half-life 

(days; assuming 12 h light/day) (25C) 98 429915-12

Aerobic soil metabolism half-lives, parent (20C

for CA loam and 25C for the rest)

153 (CA loam)

31.1 (Speyer sand)

28.2 (Speyer loamy sand)

27.8 (Speyer sandy loam)

31.4 (SLV sandy loam) 

424362-06

487711-02

Aerobic soil metabolism half-lives, TTR (20C

for CA loam and 25C for the rest)

139 (CA loam)

49.7 (Speyer sand)

41.3 (Speyer loamy sand)

42.1 (Speyer sandy loam)

49.4 (SLV sandy loam) 

424362-06

487711-02

Aerobic soil metabolism half-lives, summed 

degradates (RH-112651 + RH-112703 + RH96595) (20C for CA loam and 25C for the rest)

123.8 (CA loam)

29.3 (Speyer sand)

43.7 (Speyer loamy sand)

34.6 (Speyer sandy loam)

36.3 (SLV sandy loam) 

424362-06

487711-02

Aerobic aquatic metabolism half-lives (days)

(25C)

99 (Arkansas silty clay hydrosoil)

101 (California clay loam hydrosoil) 424362-07

Anaerobic aquatic metabolism half-lives (days)

(25C)

179 429312-16

Mobility

Soil-water sorption coefficients, parent (Kd, 

mL/g) 

7.8 clay

4.4 loam

1.6 loamy sand

8.2 sandy clay loam

5.7 loamy sand

424362-08

Organic-carbon normalized sorption coefficients, 

parent (Koc) (mL/gOC)

894 clay

656 loam

351 loamy sand

391 sandy clay loam

566 loamy sand 

424362-08

Soil-water sorption coefficients, degradate RH112651 (Kd, mL/g)0.68 clay

0.68 clay loam

1.54 loamy sand

0.34 sand

429312-19

Organic-carbon normalized sorption coefficients, 

degradate RH-112651 (Koc)(mL/gOC)

78 clay

111 clay loam

156 loamy sand

76 sand

429312-19

Field Dissipation

Terrestrial field dissipation half-lives (days) 39-53 CA sandy loam

31-52 NY silt loam, WA sand

4229915-14

437977-03
7

Drinking Water Exposure Modeling

Models

Tebufenozide TTR EDWCs for surface water and groundwater were generated using 

EFED’s standard suite of models. The Surface Water Concentration Calculator (SWCC version 

1.106; May 2014) model was used to generate EDWCs of tebufenozide TTR that may occur in 

surface water used as drinking water. SWCC (which essentially comprises updated 

implementations of the PRZM and EXAMS models) simulates pesticide application, movement 

and transformation on an agricultural field and the resultant pesticide loadings to a receiving 

water body via runoff, erosion, and spray drift, and then simulates the fate of the pesticide and 

resulting concentrations in the water body. Standard assumptions for drinking water assessment 

are a watershed of 172.8 ha that drains into an adjacent drinking water “index” reservoir of 5.26 

ha surface area, and average depth 2.74 m. Spray drift (modeled as direct deposition of the 

pesticide into the reservoir) is assumed to be 13.5% of the applied active ingredient for aerial 

application, and 6.6% of the applied for ground application. A Percent Cropped Area (PCA) of 

100% was used because current labels include a multitude of agricultural uses.

Groundwater EDWCs for tebufenozide were derived using the PRZM-GW model 

(Pesticide Root Zone Model for Groundwater, version 1.07, Nov., 2014), with the GW-GUI 

(Graphical User Interface, version 1.0, August 31, 2012). PRZM-GW is a one-dimensional 

leaching model that estimates potential concentrations of pesticides in vulnerable groundwater. 

The model simulates transport through the crop root zone and soil profile, of a pesticide 

following its application to an agricultural field. PRZM-GW was used to simulate 30 to 100

years of repeated tebufenozide application in six standard scenarios: Delmarva, GA coastal, NC 

cotton, WI corn, FL potato and FL citrus. Each scenario represents a different location known to 

be vulnerable to contaminant leaching (e.g., because of sandy soils). SCI-GROW is a regression 

model used as a screening tool to estimate potential pesticide concentrations in vulnerable 

groundwater that might be used as drinking water. SCI-GROW was developed by fitting a linear 

model to groundwater concentrations with the Relative Index of Leaching Potential (RILP) as 

the independent variable. Groundwater concentrations were taken from 90-day average high 

concentrations from Prospective Groundwater studies; the RILP is a function of aerobic soil 

metabolism and the soil-water partition coefficient. The output of SCI-GROW represents 

concentrations that might be expected to occur in shallow unconfined aquifers under sandy soils, 

which is representative of the groundwater most vulnerable to pesticide contamination likely to 

serve as a drinking water source. 

Modeling Approach and Input Parameters

Screening-level modeling was conducted to generate EDWCs in surface water and 

groundwater of tebufenozide TTR following tebufenozide’s use on numerous crops and

ornamentals. Surface water modeling for all crops was conducted using SWCC, based on 

application rates presented in Tables 2 and 6. Input fate parameters used in surface water 

modeling are presented in Table 5. Scenarios modeled with SWCC are indicated in Table 6, 

along with key scenario details. For the use on cranberries, surface water modeling was also 

conducted using the Provisional Cranberry Model (v 2.0, December 9, 2010), which is a 

provisional refinement to the Tier I Rice Model (v1.0, May 8, 2007). The Provisional Cranberry 

Model is based on the same assumptions as the Tier I Rice Model, with the addition of 
8

degradation processes in dry and flood conditions and a water depth of twelve inches in the 

flooded cranberry bog. The cranberry bog water depth of twelve inches is a maximum depth 

recommended by the Cape Cod Cranberry Growers Association (2001). Degradation of 

tebufenozide residues of concern is assumed to occur predominantly via aerobic microbial 

metabolism, whether on dry cranberry bog soil or in bog flood water. The equations used in the 

Provisional Cranberry Model are briefly described in Appendix B. Input parameter values used 

in groundwater modeling are presented in Table 7. 

As previously mentioned, groundwater modeling using PRZM-GW was “refined” by 

simulating parent and the three summed degradates as separate entities, then combining their 

resulting EDWCs to represent TTR. In conducting this modeling, application rates were 

adjusted to reflect the maximum percent conversion to any degradate (26.39%) noted in any of 

the fate studies. In terms of parent equivalents, the combined application rate of parent and 

degradates thus equaled the maximum label rate (on an annual basis) of 2.0 lb a.i./A. In running 

SWCC on tebufenozide TTR, and PRZM-GW on the summed major degradates, the mean soil 

sorption coefficient for degradate RH-112651 (KOC = 105 mL/goc) was employed because it is 

lower (more conservative) than the KOC of the parent. The KOC model of sorption was 

determined to apply rather than the Kd model because the coefficient of variation was lower for 

the reported KOC values than for corresponding Kd values. This was true both for parent 

tebufenozide and for RH-112651. In running PRZM-GW on parent tebufenozide, the mean soil 

sorption coefficient for tebufenozide (KOC = 566 mL/gOC) was used. In running SCI-GROW on 

TTR the median KOC for RH-112651 (94.5 mL/gOC) was used, in accordance with EFED’s input 

parameter guidance

(http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm). In running 

SWCC to represent TTR, an aerobic soil metabolism half-life of 93.1 days was used, which is 

the 90 percent upper confidence limit on the mean value for five aerobic soil measurements of 

half-life of parent plus degradates RH-112651, RH-112703, and RH-96595. In running SCIGROW to represent TTR, an aerobic soil metabolism half-life of 49.4 days was used, which is 

the median half-life for the same aerobic soil values.
9

Table 5. Input values for the SWCC modeling of tebufenozide

Input Parameter Value Source/comment

Hydrolysis half-life (t1⁄2 in days) 0 (stable) MRID 424362-04

Aqueous Photolysis half-life (t1⁄2

in days) 0 (stable) MRID 424362-05

Aerobic Soil metabolism half-life 

(t1⁄2 in days) 93.1

MRIDs 424362-06, 478811-02. Represents the 90 

percent upper confidence limit on the mean of 5

aerobic soil metabolism half-life values for parent 

plus degradates RH-112651, RH-112703, and RH96595.

1, 2

Aerobic Aquatic metabolism halflife (t1⁄2 in days) 103.1

MRID 424362-07. Represents the 90 percent upper 

confidence limit on the mean of two half-life values

in aerobic silty clay soil:water and clay loam 

soil:water systems.

Benthic metabolism half-life (t1⁄2

in days) 537

MRID 429312-16. Represents three times the 

single available whole-system half-life (179 days) 

from an anaerobic silt-loam sediment:pond water 

system.

Soil partition coefficient Koc

(mL/g) 105 MRID 429312-19. Mean of four Koc values for degradate RH-112651. 

1 EFED input parameter guidance is located at: http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm

2 Calculation excludes NJ sandy loam soil

Table 6. SWCC scenarios and inputs for tebufenozide modeling

Use SWCC Scenario Single Applic. Rate

(lbs a.i./A) [kg/ha]

Number of 

Applications

First Applic. 

Date

Bushberries, Cane 

berries

ORberriesOP 0.25 [0.28 ] 4 5/15

Canola NDcanolaSTD 0.25 [0.28 ] 4 5/15

Citrus FLcitrusSTD 0.25 [0.28 ] 5 5/15

Brassica FLcabbageSTD 0.12 [0.135 ] 15 2/15

Cotton MScottonSTD, 

NCcottonSTD 0.25 [0.28 ] 4 5/15

Cranberry ORberriesOP 0.25 [0.28 ] 4 5/15

Fruiting vegetables FLpeppersSTD 0.25 [0.28 ] 8 5/15

Mint ORmintSTD 0.25 [0.28 ] 8 5/15

Ornamentals FLnurserySTD_V2 0.25 [0.28 ] 8 5/15

Pome fruit NCappleSTD 0.31 [0.347] 6 5/15

Sugarcane FLsugarcaneSTD, 

LAsugarcaneSTD 0.25 [0.28 ] 8 5/15

Almonds, Walnuts, 

Other nuts

GAPecansSTD 0.47 [0.527] 4 5/15

Pecans GAPecansSTD 0.26 [0.291] 7 5/15

Trees, Forests, 

Shrubs

FLnurserySTD_V2 0.12 [0.135] 2 5/15

Pasture, rangeland RangeBSS 0.125 [0.14] 4 5/15
10

Table 7. Input values for the PRZM-GW Model for Tebufenozide.

Input Parameter Value Source/comment

App. Rate (lb a.i./A/yr),

parent

1.472

(8 applications at 0.184 lb/A each)

Max rate (2.0 lb/A/yr) minus max 

conversion fraction to RH-112651 

(26.39%) observed in fate studies

App. Rate (lb a.i./A/yr), RH112651 + RH-112703 + RH96595

0.528

(8 applications at 0.066 lb/A each)

Max conversion fraction to RH112651observed in fate studies 

(26.39% in MRID 42436207) 

times max app. rate (2.0 lb/A)

Hydrolysis half-life (t1⁄2 in 

days) 0 (stable) MRID 42436204

Aerobic Soil metabolism 

half-life (t1⁄2 in days)

92.1 (parent)

80.7 (RH-112651 + 

RH-112703 + RH-96595)

MRIDs 42436206, 47881102. 

Represent the 90 percent upper 

confidence limit on the mean of 

five aerobic soil metabolism halflife values for parent and summed 

degradates, respectively2. 

Soil partition coefficient Koc

(mL/g)

566 (parent)

105 (RH-112651 + 

RH-112703 + RH-96595)

MRID 42436208: mean of four 

values for parent

MRID 42931219: mean of four

values for degradate RH-112651 

1 TTR refers to parent + RH-112651 + RH-112703 + RH-96595

2 EFED input parameter guidance is located at: http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm

Table 8. Input values for the SCI-GROW model for tebufenozide

Input Parameter Value Source/comment

App. Rate (lb a.i./A/yr), TTR 2.0

(0.25 lb a.i./A, 8 apps/yr)

Label max rate (annual) for fruiting 

vegetables, mint and ornamentals

Hydrolysis half-life (t1⁄2 in days) 0 (stable) MRID 42436204

Aerobic Soil metabolism halflife (t1⁄2 in days) 49.4 (TTR) MRIDs 42436206, 47881102: median of 

five half-lives for TTR

Soil partition coefficient Koc

(mL/goc)

94.5 (RH-112651 + 

RH-112703 + RH-96595)

MRID 42931219: median of four values

for degradate RH-112651 

Modeling Results

Surface water EDWCs for tebufenozide TTR are presented in Table 9. Groundwater

EDWCs are presented in Table 10. Values in bold are recommended for use in the human health

dietary risk assessment. Outputs from the model runs that produced the highest EDWCs are 

provided in Appendix A. Output concentrations reported in Appendix A for surface water have 

not been modified for percent cropped area since the PCA adjustment factor is 1.0, as multiple 

uses are included in the DWA. Output concentrations for groundwater are never adjusted using a 

PCA, since PCAs represent watershed-scale dilution effects that cannot be presumed to apply to 

groundwater.
11

Table 9. Tebufenozide TTR Screening Level EDWCs for Surface Water1

Use Scenario Application 

Method

1-in-10 year 

acute (μg/L)

1-in-10 year 

chronic (μg/L)

30-year mean 

cancer (μg/L)

Bushberries, 

Cane berries

ORberriesOP aerial 4.00 0.396 0.316

ground 2.98 0.269 0.181

Canola NDcanolaSTD aerial 12.7 0.784 0.413

ground 12.3 0.707 0.327

Citrus FLcitrusSTD aerial 28.4 1.75 1.22

ground 28.7 1.72 1.16

Brassica FLcabbageSTD aerial 25.5 2.87 2.00

ground 26.2 2.81 1.90

Cotton MScottonSTD aerial 32.7 1.68 0.853

ground 32.9 1.64 0.776

NCcottonSTD aerial 27.7 1.78 1.13

ground 28.0 1.74 1.06

Cranberry ORberriesOP aerial 4.22 0.398 0.316

ground 3.69 0.260 0.179

Fruiting 

vegetables

FLpeppersSTD aerial 41.8 3.13 2.19

ground 42.5 3.10 2.11

Mint ORmintSTD aerial 9.89 0.934 0.672

ground 9.68 0.700 0.407

Ornamentals FLnurserySTD_V2 aerial 28.5 2.27 1.62

ground 28.5 2.19 1.51

Pome fruit NCappleSTD aerial 34.1 2.88 1.50

Sugarcane FLsugarcaneSTD aerial 41.8 2.00 1.29

ground 42.5 1.99 1.26

LAsugarcaneSTD aerial 50.9 2.68 1.58

ground 51.8 2.68 1.54

Almonds, 

Walnuts, Other 

nuts

GAPecansSTD aerial 43.0 2.17 1.32

ground 42.3 2.03 1.14

Pecans GAPecansSTD aerial 27.3 1.88 1.22

ground 27.2 1.70 1.03

Trees, Forests, 

Shrubs

FLnurserySTD_V2 aerial 10.8 0.438 0.204

ground 10.7 0.432 0.190

Pasture, 

rangeland

RangeBSS aerial 19.2 1.13 0.608

ground 19.4 1.14 0.583

Cranberry Provisional 

Cranberry Model2

NA 279.3 105.8 105.83

1Bolded values are the highest surface water concentrations. 

2 Not a SWCC scenario

3Reflects a 21-day holding time, post-flood.
12

Table 10. PRZM-GW and SCI-GROW groundwater EDWCs based on tebufenozide use on fruiting 

vegetables, mint and ornamentals.

PRZM-GW Results

Scenario

Simulated 

Chemical 

Entity

Annual 

Appl. Rate 

(lbs a.i./A)1

Max. Daily 

Conc. 

(μg/L)

PostBreakthrough 

Mean Conc. 

(μg/L)

Simulation 

Breakthrough 

Time (days)

Delmarva Tebufenozide 1.472 9.79 8.85 7967

Major degs 0.528 34.6 31.4 2359

TTR 2.0 44.4 40.2 NA

FL (citrus) Tebufenozide 1.472 23.7 22.4 6473

Major degs 0.528 50.8 43.2 1772

TTR 2.0 74.5 65.6 NA

FL 

(potato)

Tebufenozide 1.472 0.0041 0.0026 13058

Major degs 0.528 2.59 1.59 2834

TTR 2.0 2.59 1.59 NA

GA 

(coastal)

Tebufenozide 1.472 3.31 2.99 10667

Major degs 0.528 16.0 14.8 2954

TTR 2.0 19.3 17.8 NA

NC 

(coastal)

Tebufenozide 1.472 5.09 4.8 7245

Major degs 0.528 35.9 29.7 2924

TTR 2.0 41.0 34.5 NA

WI (corn) Tebufenozide 1.472 40.4 38.1 10027

Major degs 0.528 76 69.1 3777

TTR 2.0 116.42 107.22 NA

SCI-GROW Results

Simulated Chemical Entity Application Rate EDWC (μg/L)

TTR 0.25 lb a.i./A, 8 apps/yr 1.18

1 Of parent equivalents.

2Bolded values are recommended for use in the human health dietary risk assessment

The PRZM-GW and SCI-GROW results represent groundwater concentrations that might 

be expected in shallow, unconfined aquifers under sandy soils. The SWCC model results 

represent concentrations that might occur in untreated surface water in runoff-vulnerable 

locations. The simulated concentrations provided in this assessment are expected to represent 

conservative estimates of concentrations in drinking water. 

Monitoring Data

Only limited monitoring data are available for tebufenozide. EFED conducted a search 

(January 27, 2015) of the USGS National Water Quality Assessment (NAWQA) Program 

database (http://cida.usgs.gov/nawqa_queries_public/), the USGS Community Water System 

(CWS) data (http://pubs.usgs.gov/ds/544/), the CDPR surface water and sediment database

(http://cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm), and the USEPA/USGS/NWQMC (National 

Water Quality Monitoring Council) Water Quality Portal database

(http://www.waterqualitydata.us/). The CWS, CDPR and Water Quality Portal databases do not 

include any records of tebufenozide as a sampled constituent. The NAWQA database lists 

tebufenozide as a constituent, and includes records of 11 “filtered” samples collected from the 

Rio Grande River, near Brownsville, TX, on various dates in 2013. All results are listed as “< 2

ng/L”, which presumably reflects the analytical method limit of quantitation. 
13

Drinking Water Treatment Effects

No specific information on the effects of drinking water treatment on the removal of 

tebufenozide or its degradates is currently available. The EDWCs in this assessment are 

representative of concentrations in drinking water source water (pre-treatment) and are derived 

from daily instantaneous peak concentrations. For surface water, the conceptual model assumes 

that pesticide reaches surface water via spray drift and runoff, and is then instantaneously mixed 

within the water column and reversibly sorbed to benthic sediments. As tebufenozide residues 

are stable to hydrolysis and appear to be stable to abiotic oxidation, the compound is not 

expected to degrade during the time that elapses from drinking water intake through distribution 

to the consumer’s tap. Because organic carbon mediates the sorption of tebufenozide to soils, 

treatment methods such as sedimentation, flocculation, and activated carbon, that are designed to 

capture contaminants via sorption, may remove some tebufenozide and/or its degradates. 

Tebufenozide does not degrade via aqueous photolysis; therefore, where ultraviolet light is used 

as a means of disinfection, degradation is not expected to be enhanced. 

Uncertainties and Data Gaps

This assessment is based on available environmental fate data. There are no significant 

data gaps in the environmental fate database submitted by the registrant. The drinking water 

assessment is a screening-level assessment based on simple models and assumptions. The 

modeling assessment relies on maximum use patterns and national default PCAs to reflect 

potential surface and groundwater concentrations. To the extent that actual use patterns involve 

application of less a.i. than the permissible (labeled) maxima, aquatic concentrations could be 

lower than EDWCs reported herein.

CITATIONS

Cape Cod Cranberry Growers Association. 2001. Cranberry Water Use: An Information Fact 

Sheet. June, 2001. Online at: http://www.cranberries.org/pdf/wateruse.pdf. Accessed 

Mar. 17, 2010.

Dhadialla, T. S., G. R. Carlson, and D. P. Le. 1998. New insecticides with ecdysteroidal and 

juvenile hormone activity. Annual Reviews in Entomology 43: 545 - 569.

Shimizu, B., Y. Nakagawa, K. Hattori, K. Nishimura, N. Kurihara, and T. Ueno. 1997.

Molting hormonal and larvicidal activities of aliphatic acyl analogs of 

dibenzoylhydrazine insecticides. Steroids 62 (10): 638 - 642.

U.S. Environmental Protection Agency. 1993. Review of data to support EUP use in forests. 

February 8, 1993 (DP Barcode D182683).

U.S. Environmental Protection Agency. 1994. EEB Branch Review Section 3 Registration of 

Tebufenozide Use on Walnuts (Scan Bar Code 2072743).

U.S. Environmental Protection Agency. 1999. EFED risk assessment for Section 3 registration of 

tebufenozide (ConfirmTM 2F & 70WSP). February 26, 1999 (DP Barcode D232998).
14

U.S. Environmental Protection Agency. 2008. Registration Review – Preliminary Problem 

Formulation for Ecological Risk and Environmental Fate, Endangered Species, and 

Drinking Water Assessments for Tebufenozide. Office of Pesticide Programs. 

Environmental Fate and Effects Division. 4 November 2008. DP Barcodes D352989, 

D352987, D352988.

U.S. Environmental Protection Agency. 2009. Guidance for Selecting Input Parameters in 

Modeling the Environmental Fate and Transport of Pesticides, Version 2.1. U.S. 

Environmental Protection Agency, Office of Prevention, Pesticides and Toxic 

Substances, Office of Pesticide Programs, Environmental Fate and Effects Division, 

October 22, 2009. Online at: 

http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm

U.S. Environmental Protection Agency. 2012. Criteria Used by the PBT Profiler. 

September 4, 2012. Office of Chemical Safety and Pollution Prevention. United States 

Environmental Protection Agency. Available at http://www.pbtprofiler.net/criteria.asp

(Accessed January 23, 2015)

U.S. Environmental Protection Agency. 2012. Guidance for Selecting Input Parameters for 

Modeling Pesticide Concentrations in Groundwater Using the Pesticide Root Zone 

Model, Version 1.0. U.S. Environmental Protection Agency, Office of Pesticide 

Programs, Environmental Fate and Effects Division. Health Canada, Pesticide 

Management Regulatory Agency, Environmental Assessment Directorate. October 15, 

2012.

U.S. Environmental Protection Agency. 2014. Tebufenozide: Residues of Concern in Drinking 

Water. Memo from Mohsen Sahafayen to Jim Carleton and Sarah Winfield. Office of 

Pesticide Programs, Health Effects Division. DP Barcode 423156.
15

Appendix A

SELECTED SURFACE WATER AND GROUNDWATER MODELING 

OUTPUT FILES

SWCC Output

Summary of Water Modeling of tebufenozide TTR (sugarcane) and the 

USEPA Standard Reservoir

Estimated Environmental Concentrations for tebufenozide are presented in Table 1 for the 

USEPA standard reservoir with the LAsugarcaneSTD field scenario. A graphical presentation of 

the year-to-year peaks is presented in Figure 1. These values were generated with the Surface 

Water Calculator (Version 1.101). Critical input values for the model are summarized in Table 2.

This model estimates that about 3.4% of tebufenozide TTR applied to the field eventually 

reaches the water body. The main mechanism of transport from the field to the water body is by 

runoff (91% of the total transport), followed by spray drift (5.9%), and erosion (2.9%).

In the water body, pesticide dissipates with an effective water column half life of 8.6 days. (This 

value does not include dissipation by transport to the benthic region; it includes only processes 

that result in removal of pesticide from the complete system.) The main source of dissipation in 

the water column is volatilization (effective average half life = 12.1 days), followed by washout 

(37.9 days), and metabolism (139.6 days).

In the benthic region, pesticide dissipates very slowly (727.2 days).The main source of 

dissipation in the benthic region is metabolism (effective average half life = 727.2 days). The 

vast majority of the pesticide in the benthic region (91.9%) is sorbed to sediment rather than in 

the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for tebufenozide TTR.

Peak (1-in-10 yr) 51.8

4-day Avg (1-in-10 yr) 43.8

21-day Avg (1-in-10 yr) 28.7

60-day Avg (1-in-10 yr) 14.8

365-day Avg (1-in-10 yr) 2.68

Entire Simulation Mean 1.54

Table 2. Summary of Model Inputs for tebufenozide.

Scenario LAsugarcaneSTD

Koc (ml/g) 105

Water Half Life (days) @ 25 °C 103.1
16

Benthic Half Life (days) @ 25 °C 537

Photolysis Half Life (days) @ 40 

°Lat

0

Hydrolysis Half Life (days) 0

Soil Half Life (days) @ 25 °C 93.1

Foliar Half Life (days) 0

Molecular Wt 352

Vapor Pressure (torr) 2.25e-4

Solubility (mg/l) .83

Figure 1. Yearly Peak Concentrations
17

Summary of Water Modeling of tebufenozide TTR (fruiting vegetables) and 

the USEPA Standard Reservoir

Estimated Environmental Concentrations for tebufenozide are presented in Table 1 for the 

USEPA standard reservoir with the FLpeppersSTD field scenario. A graphical presentation of 

the year-to-year peaks is presented in Figure 1. These values were generated with the Surface 

Water Concentration Calculator (SWCC Version 1.106). Critical input values for the model are 

summarized in Tables 2 and 3.

This model estimates that about 2.9% of tebufenozide applied to the field eventually reaches the 

water body. The main mechanism of transport from the field to the water body is by runoff 

(85.6% of the total transport), followed by spray drift (14.3%) and erosion (0.07%).

In the water body, pesticide dissipates with an effective water column half-life of 6.6 days. (This 

value does not include dissipation by transport to the benthic region; it includes only processes 

that result in removal of pesticide from the complete system.) The main source of dissipation in 

the water column is volatilization (effective average half-life = 8.6 days) followed by washout 

(37.9 days) and metabolism (112.9 days).

In the benthic region, pesticide dissipates slowly (192.5 days). The main source of dissipation in 

the benthic region is metabolism (effective average half-life = 192.5 days). The vast majority of 

the pesticide in the benthic region (91.9%) is sorbed to sediment rather than in the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for tebufenozide TTR.

Peak (1-in-10 yr) 41.8

4-day Avg (1-in-10 yr) 36.1

21-day Avg (1-in-10 yr) 21.2

60-day Avg (1-in-10 yr) 12.0

365-day Avg (1-in-10 yr) 3.13

Entire Simulation Mean 2.19

Table 2. Summary of Model Inputs for tebufenozide TTR.

Scenario FLpeppersSTD

Cropped Area Fraction 1.0

Koc (ml/g) 105

Water Half-Life (days) @ 25 °C 105

Benthic Half-Life (days) @ 25 °C 179

Photolysis Half-Life (days) @ 40 

°Lat

0

Hydrolysis Half-Life (days) 0
18

Soil Half-Life (days) @ 25 °C 93.1

Foliar Half-Life (days) 0

Molecular Wt 352

Vapor Pressure (torr) 2.25e-4

Solubility (mg/l) .83

Table 3. Application Schedule for tebufenozide.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

5/15 Foliar 0.28 .95 .135

5/25 Foliar 0.28 .95 .135

6/4 Foliar 0.28 .95 .135

6/14 Foliar 0.28 .95 .135

7/15 Foliar 0.28 .95 .135

7/25 Foliar 0.28 .95 .135

8/4 Foliar 0.28 .95 .135

8/14 Foliar 0.28 .95 .135

Figure 1. Yearly Peak Concentrations
19

PRZM-GW Output

Groundwater Analysis for tebufenozide (parent) and the Wisconsin Corn -

WI Central Sands Scenario

Estimated groundwater concentrations and breakthrough times for tebufenozide are presented in 

Table 1 for the Wisconsin Corn - WI Central Sands groundwater scenario. A graphical 

presentation of the daily concentrations in the aquifer is presented in Figure 1. These values were 

generated with the PRZM-GW (Version 1.07). Critical input values for the model are 

summarized in Tables 2 and 3.

Table 1. Groundwater Results for tebufenozide and the Wisconsin Corn - WI Central 

Sands Scenario.

Peak Concentration (ppb) 40.4

Post-Breakthrough Mean 

Concentration (ppb)

 38.1

Entire Simulation Mean 

Concentration (ppb)

 29.1

Average Breakthrough 

Time (days)

10026.81

Throughputs 3.606532

Table 2. Chemical Properties for Groundwater Modeling of tebufenozide.

Koc (ml/g) 572

Surface Soil Half Life (days) 92.1

Hydrolysis Half Life (days) 0

Diffusion Coefficint Air (cm2/day) 0

Henry's Constant 0.0

Enthalpy (kcal/mol) 0.0

Table 3. Pesticide application scheme used for tebufenozide. This application scheme was 

applied every year of the simulation.

Application Date

(Month/Day)

Application Method Application Rate

(kg/ha)

5/15 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.206
20

5/25 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.206

6/4 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.206

6/14 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.206

6/24 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.206

7/4 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.206

7/14 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.206

7/24 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.206

Figure 1. Aquifer Breakthrough Curve for tebufenozide and the Wisconsin Corn - WI 

Central Sands Scenario
21

Groundwater Analysis for tebufenozide degradates (RH-112651 + RH-112703 

+ RH-96595) and the Wisconsin Corn - WI Central Sands Scenario

Estimated groundwater concentrations and breakthrough times for tebufenozide degradates are 

presented in Table 1 for the Wisconsin Corn - WI Central Sands groundwater scenario. A 

graphical presentation of the daily concentrations in the aquifer is presented in Figure 1. These 

values were generated with the PRZM-GW (Version 1.07). Critical input values for the model 

are summarized in Tables 2 and 3.

Table 1. Groundwater Results for tebufenozide degradates and the Wisconsin Corn - WI 

Central Sands Scenario.

Peak Concentration (ppb) 76

Post-Breakthrough Mean 

Concentration (ppb)

 69.1

Entire Simulation Mean 

Concentration (ppb)

 46.7

Average Breakthrough 

Time (days)

3777.435

Throughputs 2.90144

Table 2. Chemical Properties for Groundwater Modeling of tebufenozide degradates.

Koc (ml/g) 105

Surface Soil Half Life (days) 80.7

Hydrolysis Half Life (days) 0

Diffusion Coefficint Air (cm2/day) 0

Henry's Constant 0.0

Enthalpy (kcal/mol) 0.0

Table 3. Pesticide application scheme used for tebufenozide degradates. This application 

scheme was applied every year of the simulation.

Application Date

(Month/Day)

Application Method Application Rate

(kg/ha)

5/15 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.074

5/25 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.074
22

6/4 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.074

6/14 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.074

6/24 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.074

7/4 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.074

7/14 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.074

7/24 Ground application with mass 

distribution increasing 

proportionally with depth to 4 cm

0.074

Figure 1. Aquifer Breakthrough Curve for tebufenozide degradates and the Wisconsin 

Corn - WI Central Sands Scenario
23

SCIGROW Output

 SCIGROW

 VERSION 2.3

 ENVIRONMENTAL FATE AND EFFECTS DIVISION

 OFFICE OF PESTICIDE PROGRAMS

 U.S. ENVIRONMENTAL PROTECTION AGENCY

 SCREENING MODEL

 FOR AQUATIC PESTICIDE EXPOSURE

SciGrow version 2.3

chemical:tebufenozide TTR

time is 2/ 3/2015 8:41:44

------------------------------------------------------------------------

 Application Number of Total Use Koc Soil Aerobic

 rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------

 0.250 8.0 2.000 9.45E+01 49.4

------------------------------------------------------------------------

groundwater screening cond (ppb) = 1.18E+00 

************************************************************************
24

Appendix B

PROVISIONAL CRANBERRY MODEL EQUATIONS

The Provisional Cranberry Model is a refinement of the Tier I Rice Model v1.0 

(Equations 1 and 2), which is a simple equilibrium partitioning equation that calculates a single, 

screening-level concentration in rice paddy water and released tailwater based on a compound’s 

application rate and soil mobility.

Equations 1-2: Tier I Rice Model v1.0 (USEPA, 2007b).

  w sed sed b d

a i

w

d d K

m

C

 

3

2

0

10

10 '



 



(1)

and, if appropriate:

Kd01KOC  0.

(2)

where,

Cw0 = initial water concentration [μg/L]

mai' = mass applied per unit area [kg/ha]

Kd = water-sediment partitioning coefficient [L/kg]

KOC = organic carbon partitioning coefficient [L/kg]

dw = water column depth = 0.10 m

dsed = sediment depth = 0.01 m

θsed = porosity of sediment = 0.509

ρb = bulk density of sediment = 1300 kg/m3

First, the Tier I Rice Model was provisionally modified (Equation 3) to include as inputs 

degradation rate constants in order to estimate single, screening-level concentrations in paddy 

water or tailwater at a given time after application.

Equation 3: Provisional Modified Rice Model (Jones, 2006).

d

kt

a i

w

K

m e

C

0.00105 0.00013

'







(3)

where,

Cw = water concentration [μg/L]

t = interval since last application [d]

k = upper 90th percentile degradation rate constant [1/d]
25

Then, the Provisional Modified Rice Model water column depth was 

increased to a depth that is used to flood cranberry bogs (i.e., 12 inches; Cape Cod 

Cranberry Growers Association, 2001).

i.e.,

dw = water column depth = 0.305 m

In order to model degradation prior to the flood at harvest, the 

application rates for n number of pre-harvest applications were independently 

degraded over the interim until flooding and then summed (Equation 4).

Equation 4: Degradation in a Dry Bog.





 

n

k t

ai ai n

n m m e

1

2

' '

(4)

where,

mai' = mass per unit area at flood [kg/ha]

mai'n = mass applied per unit area on the nth application [kg/ha]

k2 = upper 90th percentile degradation rate constant on dry bog [1/d]

tn = interval from the nth application to harvest [d]

n = number of pre-harvest applications

These four equations and parameter sets constitute the Provisional 

Cranberry Model (Equations 1-4).

Equations 2, 4, and 5: Provisional Cranberry Model.





 

n

k t

ai ai n

n m m e

1

2

' '

(4)

where,

mai' = mass per unit area at flood [kg/ha]

mai'n = mass applied per unit area on the nth application [kg/ha]

k2 = upper 90th percentile degradation rate constant on dry bog [1/d]

tn = interval from the nth application to harvest [d]

n = number of pre-harvest applications

followed by:

  w sed sed b d

kt

a i

w

d d K

m e

C

 

3

2

10

10 '





 



(5)
26

and, if appropriate:

Kd01KOC  0.

(2)

where,

Cw = water concentration [μg/L]

t = interval since flood [d]

k = upper 90th percentile degradation rate constant [1/d]

Kd = water-sediment partitioning coefficient [L/kg]

KOC = organic carbon partitioning coefficient [L/kg]

dw = water column depth = 0.305 m

dsed = sediment depth = 0.01 m

θsed = porosity of sediment = 0.509

ρb = bulk density of sediment = 1300 kg/m3