Aquatic Pesticide Monitoring Program 

Final Report 

Geoffrey S. Siemering 

Jennifer Hayworth 

Aroon Melwani 

San Francisco Estuary Institute 

7770 Pardee Lane, 2nd Floor 

Oakland, CA 94621 

February 2005 
This report should be cited as; 

Siemering, G., Hayworth, J., and Melwani, A. 2005. Aquatic Pesticide 

Monitoring Program Final Report. SFEI Contribution Number 392. San 

Francisco Estuary Institute, Oakland, CA. 
i

TABLE OF CONTENTS 

EXECUTIVE SUMMARY .............................................................................................. 1

INTRODUCTION............................................................................................................. 5

BACKGROUND.................................................................................................................. 5 

MANAGEMENT AND ASSESSMENT QUESTIONS................................................................. 7 

ORGANIZATION................................................................................................................ 9 

MONITORING PROGRAM......................................................................................... 11

TARGET PESTICIDES....................................................................................................... 11 

SITE SELECTION............................................................................................................. 13 

SAMPLING STRATEGY.............................................................................................. 14

ANNUAL GOALS............................................................................................................. 15 

REFERENCE LOCATIONS................................................................................................. 17 

SAMPLE COLLECTION METHODS ................................................................................... 20 

DATA MANAGEMENT..................................................................................................... 20 

APPROACH TO RISK ASSESSMENT.................................................................................. 21 

Sediment Quality Triad Approach ............................................................................ 21

Risk Quotient Calculation......................................................................................... 22

RESULTS ........................................................................................................................ 24

2,4-D ............................................................................................................................. 24 

COPPER SULFATE........................................................................................................... 27 

CHELATED COPPER........................................................................................................ 32 

DIQUAT DIBROMIDE ...................................................................................................... 34 

FLURIDONE .................................................................................................................... 36 

GLYPHOSATE ................................................................................................................. 40 

METHOPRENE ................................................................................................................ 41 

TRICLOPYR .................................................................................................................... 43 

CONCLUSIONS ............................................................................................................. 44

MANAGEMENT AND ASSESSMENT QUESTIONS REVISITED........................ 48

REFERENCES................................................................................................................ 50

LIST OF TABLES 

Table 1. Steering Committee Organization Member List................................................. 10 

Table 2. Science Advisory Committee Members ............................................................. 10 

Table 3. Pesticide Ranking Table ..................................................................................... 13 

Table 4. Sampling frequency, collection order, and locations.......................................... 18 

Table 5. APMP Sampling Sites ........................................................................................ 18 

Table 6. Threshold Values Applied in Chemistry Evaluation after Siemering (2004).... 22 

Table 7. Aquatic Animal and Plant Levels of Concern .................................................... 23 

Table 8. Peak Concentration Risk Quotient Calculations for 2,4-D Application............. 25 
ii 

Table 9. Peak Concentration Risk Quotient Calculations for Surfactant (R-11) during 2,4-

D Application............................................................................................................ 25 

Table 10. Sediment Quality Trend Calculations for 2, 4-D (DMA)................................. 26 

Table 11. Summary of 2, 4-D (DMA) Sediment Quality Trend Data .............................. 26 

Table 12. Water Risk Quotient Calculations for Copper Sulfate Applications (Reservoir 

System) ..................................................................................................................... 27 

Table 13. Sediment Quality Trend Calculations for Copper Sulphate ............................. 29 

Table 14. Summary of Copper Sulphate Sediment Quality Trend Data........................... 30 

Table 15. Water Risk Quotient Calculations for Chelated Copper Applications (Irrigation 

Canal Systems).......................................................................................................... 32 

Table 16. Sediment Quality Trend Calculations for Chelated Copper ............................. 33 

Table 17. Summary of Chelated Copper Sediment Quality Trend Data .......................... 33 

Table 18. Water Risk Quotient Calculations for Diquat Dibromide Applications........... 35 

Table 19. Peak Risk Quotient Calculations for Fluridone Application at MID Main Canal

................................................................................................................................... 37 

Table 20 Sediment Quality Trend Calculations for Fluridone.......................................... 38 

Table 21 Summary of Fluridone Sediment Quality Trend Data....................................... 38 

Table 22. Risk Quotient Calculations for Surfactant (R-11) during Glyphosate 

Application at Doris Drain........................................................................................ 40 

Table 23. Peak Concentration Risk Quotient Calculations for Methoprene Application. 42 

Table 24. Risk Quotient Calculations for Surfactant during Triclopyr Application......... 43 

LIST OF FIGURES 

Figure 1. APMP Sampling Locations. .............................................................................. 19 

Figure 2. Typical Sampling Plan for an Individual Site ................................................... 20 
Aquatic Pesticide Monitoring Program 

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EXECUTIVE SUMMARY 

The APMP collected data during three aquatic pesticide application seasons 

which indicated that widespread acute ecosystems impacts will not occur from aquatic 

pesticides applied according to their label requirements. However, risk quotient 

exceedances and sediment quality triad calculations indicate that significant questions 

remain concerning potential localized acute impacts and chronic impacts. For most 

pesticides, further risk characterization is indicated. 

Additionally, surfactants (frequently added to pesticides by the applicator 

immediately prior to application) may be an order of magnitude more toxic than the 

active ingredient pesticide and may possibly be endocrine disrupting substances. Little 

information is required for registration of surfactants by either USEPA or California 

Department of Pesticide Regulation. In some cases, surfactants of the same chemical 

class are sold premixed with the active ingredient pesticide for terrestrial formulations, 

but for aquatic uses the surfactant is removed from the product. There is a significant 

need for additional risk characterization of surfactants. 

The three years of data gathered by the APMP should only be used for screening 

purposes in order to identify where further risk characterization or research may be 

needed. Definitive conclusions cannot be drawn from this data due to the small sample 

number, the variety of application scenarios, and the disparate water body types 

monitored. APMP generated chemical characterization, toxicity, and bioassessment data. 

The chemical characterization and toxicity data generated can be used for screening 

purposes. In complex field situations, bioassessments require multiple years of data 

before preliminary conclusions can be drawn from them. Concurrent data collection and 

analysis of all three data types (chemical, toxicity, and biological) provides important 

integrative information for ecosystem risk evaluation. 

Specific conclusions concerning individual pesticides: 

2,4-D

Monitoring of 2,4-D (in the 2,4-D dimethylamine salt formulation) with added 

surfactant showed no toxicity to standard EPA three species was observed nor did risk 
Aquatic Pesticide Monitoring Program 

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quotients indicate the need for further information. Vitellogenin induction laboratory 

experiments indicate that 2,4-D may cause endocrine disruption at legal application rates. 

The vitellogenin induction studies indicate the need for further study of the 

aquatic 2,4-D formulations and their primary breakdown products. This level of research 

should not be expected from entities conducting compliance monitoring. 

Acrolein

Because of acrolein’s rapid volatilization, work focused on development of a field 

sampling method that would allow for accurate determination of the pesticide in water. 

Current standard environmental sampling methods are inadequate for sampling of 

acrolein treated water and result in unreliable analytical results. 

Refinement of the sampling methodology began in 2003. Results indicate that the 

method developed performs well at low acrolein water concentrations, making it possible 

to determine acrolein residue values. 

Due to acrolein’s rapid volatilization, it is currently not possible to conduct 

standard water toxicity tests on it. Because of its’ extremely low Lowest Observable 

Effect Concentration (LOEC) values, the detectable presence of acrolein indicates that 

very high mortality to EPA water and sediment toxicity test species can be assumed. 

The development of diagnostic response tests (i.e. phytomonitoring, sentinel 

bivalves and fish, etc.) were explored and additional work is warranted. These tests have 

the potential to provide a low cost, low tech method of detecting acrolein outside of 

designated treatment areas. 

Copper Sulfate

Copper sulfate applications were monitored in three reservoirs. Toxicity to 

juvenile trout and Ceriodaphnia following application was observed. Peak concentration 

risk quotients showed acute and chronic U.S. EPA Office Pesticide Programs Levels-ofConcern (LOC) exceedances. 

In the reservoir treated with granular copper sulfate applications, significant 

mortality was observed in Ceriodaphnia and juvenile trout water toxicity tests 

immediately after application within the treatment area. Mortality and growth inhibition 
Aquatic Pesticide Monitoring Program 

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was also observed in a number of the sediment samples. Sediment copper concentrations 

at many sites exceeded a published Hyallela LC50 value. However, the variable toxicity 

results observed in the sediments indicates that the majority of the copper is not 

bioavailable. 

These findings indicate the need for further risk characterization associated with 

copper sulfate applications. 

Chelated Copper

Chelated copper pesticides were monitored during applications in two irrigation 

canal systems. One system used a product of mixed copper ethanolamines and the other 

the same product of mixed copper ethanolamines in an emulsified formulation. Chelated 

copper formulations are likely to have distinct behavior from each other and copper 

sulfate in aquatic environments based on the chelating agent as well as other adjuvants. It 

should be noted that copper carbonate is the active ingredient in other chelated copper 

pesticide products and no monitoring of copper carbonate based pesticides was 

conducted. 

In both systems where monitoring occurred, the water samples were almost 

uniformly toxic in pre-application and post application. Therefore, no definitive 

conclusions can be drawn about the toxicity of mixed copper ethanolamines. The 

sediment quality triad calculations indicate the possibility of copper impacts to the 

system. 

Further risk characterization associated with chelated copper applications is 

warranted. 

Glyphosate

Glyphosate was monitored at several locations. No toxicity was found to be 

associated with glyphosate applications. Glyphosate is very often applied with a 

surfactant, which may have much higher toxicity than the active ingredient. 

Based on risk quotient calculations and toxicity data, no further risk 

characterization associated with glyphosate only applications is warranted. Risk 
Aquatic Pesticide Monitoring Program 

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characterizations are warranted when a surfactant is used in conjunction with the 

glyphosate. 

Diquat Dibromide

Diquat dibromide was sampled at two locations, one small pond and a Delta 

slough. Diquat risk quotients almost uniformly exceeded LOC’s at all sampling periods 

in the Delta slough (including preapplication) and at one hour after application in the 

pond. Diquat may be applied with a surfactant which may exhibit much higher toxicity 

than the active ingredient. Diquat sediment concentrations were not considered as diquat 

is irreversibly adsorbed to sediments and is thereafter not bioavailable. 

Toxicity test and risk quotient results indicate the need for further risk 

characterization. 

Fluridone

Fluridone (applied in pellet or liquid form) was not found to be definitively toxic 

to or have LOC exceedances for the standard USEPA three species water or sediment 

amphipod organisms. The peak concentration risk quotient for Stonewort did exceed an 

acute LOC. Fluridone was found to cause sublethal toxicity (decreased shoot and root 

length) to Typha latifolia. This would indicate a potential for impacts to nontarget plants. 

Further risk characterization of fluridone impacts on nontarget plants is 

warranted. There is also cause for concern over development of genetic resistance to 

fluridone which is emerging in plant populations in Florida. 

Methoprene

Monitoring for methoprene is challenging because it is commonly applied to 

environments that do not lend themselves to traditional water and sediment sampling and 

testing methods. These systems usually have extremely shallow water and highly anoxic 

sediments which impede standard toxicity tests. In situ and laboratory toxicity tests were 

completed, but the results were inconclusive. From the one site monitored for 

methoprene, water and porewater risk quotients did not exceed criteria. However, further 

risk characterization is needed. Methoprene was persistent in marsh sediments, up to the 
Aquatic Pesticide Monitoring Program 

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ppm level, for several weeks. Little methoprene sediment toxicity data could be located 

in the literature. 

Future work is warranted to further characterize the risk of methoprene in 

sediments. Additional studies may also be warranted due to the common simultaneous 

application of methoprene and Bti. 

Triclopyr

Triclopyr was monitored at one application. Triclopyr peak concentration risk 

quotients show no LOC exceedances. Triclopyr is often applied with a surfactant, which 

may exhibit higher toxicity than the active ingredient. Further risk characterizations are 

warranted since a surfactant was used with triclopyr. 

Nonionic surfactants

The most commonly used surfactants at APMP monitoring sites were Target 

Prospreader Activator and R-11. Both are nonylphenolethoxylate based surfactants. 

Peak concentration risk quotients indicate exceedances of LOCs for a wide range of 

animal species including Delta Smelt and Sacramento Splittail. Vitellogenin induction 

experiments in Rainbow trout indicate that these nonylphenol surfactants can be an 

endocrine disruptor at application rates. There are a wide range of surfactants available, 

each one having a different toxicological profile. Due to their classification as an 

adjuvant, very little data is required for registration. However, our results suggest that 

further risk characterizations are warranted for all surfactants. 

INTRODUCTION 

Background 

In January 2002, the San Francisco Estuary Institute (SFEI) began the 

development and implementation of a statewide aquatic pesticide monitoring program 

(APMP) with funding from the California State Water Resources Control Board 

(SWRCB). The APMP was funded to evaluate the potential water quality impacts 

associated with the application of aquatic pesticides because of a series of court decisions 

and a legal settlement. Aquatic pesticides fall into two distinct groups, herbicides and 

mosquito vector control compounds. These are compounds that have registration labels 
Aquatic Pesticide Monitoring Program 

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that explicitly allow direct application to waterbodies. Pesticides applied for terrestrial 

use that reach waterbodies (i.e. through runoff or spray drift) were not studied as part of 

this project. 

In 2001, a ruling by the U.S. Ninth Circuit Court of Appeals, in Headwaters, Inc. 

v. Talent Irrigation District, stated that registration and labeling of aquatic pesticides 

under the federal pesticide law (Federal Insecticide, Fungicide, and Rodenticide Act or 

FIFRA) does not preclude the requirement to obtain coverage under a National Pollutant 

Discharge Elimination System (NPDES) permit prior to discharging such pesticides into 

waters of the United States (243 F.3d 526 (9th Cir. 2001). Headwaters, Inc. v. Talent 

Irrigation District, the U.S. Court of Appeals for the Ninth Circuit). The SWRCB issued 

an emergency NPDES permit in July 2001. This permit was challenged in California 

state court by the environmental advocacy group Waterkeepers of Northern California on 

the grounds that it did not provide sufficient protection of the environment (Waterkeepers 

Northern California v. State Water Resources Control Board, Alameda County Superior 

Court No. 2001-022050). This legal challenge coupled with that of the Talent decision 

rendered the legal application of aquatic pesticides in California impossible for the 2001 

application season (generally April-September). This legal challenge was settled with an 

agreement that the SWRCB would fund aquatic pesticide research and monitoring to 

provide the state with rigorously reviewed scientific information to develop an acceptable 

general NPDES permit upon expiration of the emergency permit in January 2004. In the 

settlement SFEI, a non-profit organization with a Board of Directors including scientists, 

environmentalists, regulators, and dischargers to the Bay, was designated as the scientific 

entity responsible for the implementation of the APMP. The settlement mandated that 

$1,950,000 be spent on aquatic pesticide monitoring and research and $600,000 exploring 

nonchemical alternatives to the use of aquatic pesticides. The contract funding this 

program states that, 

“the objective of the APMP is to implement comprehensive monitoring 

and special studies to evaluate the water quality impacts associated with 

the application of aquatic pesticides and the non-chemical alternatives to 

the use of aquatic pesticides. The primary focus shall be to provide 

information to the SWRCB and Regional Water Quality Control Boards 

(RWQCBs) to enable to SWRCB and RWQCBs to effectively regulate 

discharges of aquatic pesticides to surface waters.” 
Aquatic Pesticide Monitoring Program 

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In addition, the contract with SFEI specified that the follow studies be 

undertaken: 

1) Fate and transport of applied materials and breakdown products, including 

residence time in the environment, mass loading of the pesticide, evaluation of 

bioaccumulation. 

2) Assessment of impacts to beneficial uses including: potential routes of 

exposure, life cycle bioassessments on a range of species, biochemical and/or 

physiological testing of sublethal effects including reproduction and growth. 

3) Characterization of accumulation in sediments where a pesticide is suspected 

of sediment accumulation. 

4) Characterization of accumulation in organisms where persistence or 

bioaccumulation of suspected. 

5) Conduct community monitoring surveys including evaluation of nontarget 

plants or animals, organism diversity and ecosystem integrity. 

Management and Assessment Questions 

While the legal settlement and initial contract gave general guidance, the exact 

natural of the monitoring and research efforts were not detailed. To help direct the 

monitoring effort development, Management and Assessment questions were derived at 

the outset of the APMP. Management questions are overarching questions that need to 

be answered in order to accomplish the project goals. Assessment questions are second 

tier questions that address specific knowledge items that need to be determined to 

adequately answer the Management questions. This Management and Assessment 

question model for developing the program was used in order to provide a theoretical 

framework that would keep the scientific work on track. These questions were referred 

to throughout the project at all stages of planning and development. 

The Management and Assessment questions developed for the APMP are as 

follows (management questions in italic): 

1. Which aquatic pesticides used in California have the highest “risk” of impacts to 

people and the environment? 
Aquatic Pesticide Monitoring Program 

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a. What is the amount of each aquatic pesticide used? 

b. What is the aquatic toxicity of each compound? 

c. Where are the compounds being used? 

d. When are the compounds being used? 

e. What is their environmental fate and persistence? 

2. What are the concentrations of the target aquatic pesticides in the environment 

(water, sediment, and biota) adjacent to their application point? 

a. What are the concentrations in the dissolved fraction and particulate 

fraction (45 micron) of water? 

b. What are the concentrations in sediment pore water? 

c. What are the concentrations in bulk sediments? 

d. What are the concentrations in the gonads of native fish? 

e. What are the concentrations in the muscle tissue of native fish and 

bivalves? 

f. Are there wet-dry seasonal differences in concentrations? 

3. Are the measured concentrations above existing effects thresholds? 

a. Is the water or sediment toxic using Standard Bioassay Protocols? 

b. Are there human health risks associated with water contact or eating fish 

or shellfish? 

4. Which locations have the highest “risk” of beneficial use impairment? 

a. Should a sample of systems using pesticides be monitored? 

b. Are there sensitive areas (i.e. wildlife refuges, wilderness areas, etc) 

particularly at risk? 

5. What is the degree of biological impacts to non-target biota from application and 

exposure to aquatic pesticides? 

a. Are population mortality rates elevated compared to a reference 

population in ‘clean’ waters? 

b. Is growth impaired? 

c. Is reproduction impaired? 

The Management and Assessment questions, generated through numerous 

discussions, were used to develop a plan of action for monitoring aquatic pesticide use. 
Aquatic Pesticide Monitoring Program 

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The monitoring plan ultimately developed attempted to address as many of the 

assessment questions as possible within the fiscal and logistical constraints of the project. 

The studies performed to evaluate potential pesticide impacts will hereafter be 

referred to in general as monitoring. Monitoring to many in the scientific community 

means to test or sample on a regular or ongoing basis. However, to avoid overly length 

descriptive terms for the various studies conducted, this report will use the word 

monitoring to mean “to keep track of systematically with a view to collecting 

information.” The ‘monitoring’ performed during the APMP could be more precisely 

described as case study investigations performed with a wide variety of scientific tools to 

help inform the development of aquatic pesticide NPDES permits. 

Organization 

Due to the politically charged environment, SFEI established a consensusbuilding, stakeholder-driven process to oversee the work By having all interested parties 

involved from the inception of the project and giving input throughout, it was possible to 

achieve acceptance both of the methods used and data generated from the project. 

To ensure scientific rigor, an external scientific peer review committee was 

established to provide review and guidance for the project. Several focused workgroups 

were formed to address questions relating to chemistry, toxicity, modeling and 

bioassessments. The members of these workgroups were drawn from local academic 

institutions, government laboratories, and private firms. Contract laboratories were 

identified to perform the sample testing necessary. A mixture of university, government, 

and private labs were selected according to their expertise. 

Since the driving impetus for this project came from within the legal system, a 

project Steering Committee composed of individuals from Federal and State agencies, 

stakeholder groups, and public interest groups was assembled (Table 1). Early in the 

project, the monthly steering committee meetings focused on creating an organizational 

structure for the APMP and guiding the development of the monitoring plans, later 

quarterly meetings focused on discussing and resolving programmatic development 

issues. The meetings were open to all interested parties as well as steering committee 

members. 
Aquatic Pesticide Monitoring Program 

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Table 1. Steering Committee Organization Member List 

Central Valley Regional Water 

Quality Control Board 

California Farm Bureau 

Federation 

California Department of Fish & 

Game 

US Dept. of Agriculture Monsanto Contra Costa Mosquito Vector 

Control District 

South San Joaquin Irrigation 

District 

DeltaKeeper US Fish & Wildlife Service 

US EPA, Region 9 (WTR 5) Syngenta National Marine Fisheries Service

Association of CA Water 

Agencies 

Ventura County Water Protection 

District 

Orange County Public Facilities 

Department 

Bay Area Stormwater 

Management Agencies 

Association 

San Joaquin County Mosquito 

Vector Control District 

EMC Environmental Consulting 

Services. 

California Dept. of Pesticide 

Regulation 

Metropolitan Water District of 

Southern California 

Solano Irrigation District 

California Dept. of Boating and 

Waterways 

Marin Municipal Water District State Water Resources Control 

Board 

San Francisco Baykeeper Sutter County Agriculture California Dept of Health Services 

Vector-Borne Disease Section 

Los Angeles Dept of Water & 

Power 

Marin Municipal Water District California Dept of Food and 

Agriculture 

USEPA Region 9 California Water Quality Coalition

The external peer review panel, hereafter referred to as the Science Advisory 

Committee (SAC), was composed of five scientists who are recognized as experts on 

pesticides and their effects. This committee provided independent peer review for APMP 

workplans and findings. This committee met at the outset of the project and then annually 

to review the results and upcoming plans. The SAC members were also consulted 

periodically as technical questions arose and received written updates quarterly. SAC 

members are listed in Table 2.

Table 2. Science Advisory Committee Members 

Name Affiliation 

John H. Rodgers Clemson University 

Institute of Environmental Toxicology 

Lenwood Hall University of Maryland 

Agricultural Experiment Station 

Wye Research and Education Center 

Michael Anderson, University of California-Riverside 

Department of Environmental Sciences 

Jay Gan. University of California-Riverside 

Department of Environmental Sciences 

R. David Jones U.S. Environmental Protection Agency 

Office of Pesticide and Toxic Substances 
Aquatic Pesticide Monitoring Program 

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MONITORING PROGRAM 

The monitoring program SFEI was charged with implementing was intended to 

have wide spatial coverage, investigate behavior of all pesticides currently in use in 

California, determine potential impacts in the range of waterbody types receiving 

applications, and provide information on aquatic pesticides free of any additional 

confounding factors. It was agreed early in the program, that the length of time allowed 

and the funding provided were insufficient to accomplish the three goals. A tiered 

approach was developed to achieve a balance between program goals and what was 

practically achievable. In addition, ranking schemes and selection criteria were 

developed to guide site selection, pesticide priority, and monitoring methods. 

The tiered approach developed to help focus the implementation of the aquatic 

pesticide monitoring efforts is as follows: 

Tier 1. Information-based research. Conduct a literature review to identify likely 

pesticide/ environmental couplings where accumulation is likely or unlikely, 

determine annual usage from California Department of Pesticide Regulation 

database, and develop a permit holder database to identify best possible candidate 

monitoring sites 

Tier 2. Field monitoring. Conduct sampling to confirm presence or absence of 

pesticide in aquatic ecosystems, potential water and sediment toxicity, and 

impacts to nontarget invertebrate populations. 

Tier 3. Special studies. Where tier 1 & 2 results indicate, conduct special projects 

to address technical sampling issues or more fully characterize specific aquatic 

pesticide environmental impacts. 

Target Pesticides 

Potential target pesticides were ranked based on the following criteria: aquatic 

uses, amount used, common usage, toxicity/risk, public concern, reliable analytical 

methods, and regulatory significance (Table 3). Information on these aquatic pesticides 

was collected through a detailed literature review conducted by SFEI (Siemering et al 
Aquatic Pesticide Monitoring Program 

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2003), from the California Department of Pesticide Regulation Pesticide Use Report 

database, and from the professional opinions of a subset of steering committee members. 

The mosquito vector control compounds were by and large not addressed by the 

APMP due to the difficulty in finding suitable sampling locations, the lack of adequate 

analytical methods, and infrequent or “emergency” use of many compounds. The three 

primary mosquito control insecticides used are Bacillus Thuringiensis israelensis (BTi), 

methoprene and larvicidal oils. There are no standard analytical methods for BTi and no 

toxicity test methods for methoprene, due to its rapid degradation. Larvicidal oils vary in 

content and are also similar to other petroleum products frequently found in the 

environment. 
Aquatic Pesticide Monitoring Program 

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Table 3. Pesticide Ranking Table 

Chemical Selectivity Toxicology Phys Chem Perception Total 

Score 

Final 

Ranking 

1 – low risk 

5 – high risk

Indirect Ecosys

tem 

Terres

trial 

Human Half

-life 

Kow Mobilit

y

Sum of 

criteria 

scores 

Acrolein 5 4 5 2 (4) 1 1 5 5 32 1

Copper (total 

and ionic) 

2 4 4 - 5 1 – 2 1 21 2 2 – 3 5 26 2

2,4-D (salt) 1 (3) 2 - 3 1 – 2 1 2 3 2 3 – 4 20 3

Endothal 2 4 2 1 (1) 2 (3) (3) 2 19 4

Fluridone 3 2 1 1 1 3 2-3 3 1 – 2 19 4

Triclopyr 1 4 2 1 (1) 2 (3) (3) 3 – 4 19 4

Diquat 

dibromide 

3 4 2 - 3 1 1 1 1 1 3 18 5

Glyphosate 5 1 1 1 1 1 1 1 (4) 16 6 1

Bioavailable form 

() estimated values 

Site Selection 

The regulatory areas that were considered for sampling included irrigation supply 

systems, drinking water reservoirs, exotic weed control (canals and coastal), flood control 

and drainage, and storm water and recreational impoundments (golf courses and parks). 

A ranking system was developed with regard to system complexity. Monitoring was 

conducted in increasingly complex water bodies as sampling methods and staff 

experience and site knowledge were developed to adequately accommodate the specific 

system characteristics. The complexity of water systems were ranked as follows (in order 

of increasing complexity): irrigation district canals< storm water canals and small 

streams< lakes or reservoirs< Sacramento/ San Joaquin Delta< San Francisco Bay or 

other coastal estuaries. 

Within each water body category, the sampling sites selected for monitoring were 

based on the following criteria: 

1. Representative of typical applications of identified pesticide of interest, 

2. Limited, or well-characterized inputs, 

3. Existence of chemical analysis methods with detection limits sufficient for 

ambient environmental monitoring, 
Aquatic Pesticide Monitoring Program 

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4. Representative of a typical application by a pesticide user group (e.g., a municipal 

drinking water district, a irrigation district, a county public works department, and 

county agriculture office). 

In 2002, a database of aquatic pesticides NPDES permit holders was created. 

From this database, individual permit holders were identified whose water bodies would 

provide the greatest amount of spatial coverage and represent the greatest number of user 

groups and pesticides. These permit holders were then contacted to ascertain interest in 

participating with APMP and to gather further details on the systems receiving 

applications. Only one permit holder was not willing to participate. The final site 

selections were made after site visits and evaluations by APMP staff. While the greatest 

number of sites possible were sampled, the number is still small in comparison to the 

total number of sites receiving aquatic pesticide applications within California. 

SAMPLING STRATEGY 

Combining the assessment questions with the tiered approach and ranking criteria, 

the specific APMP monitoring objectives at each sampling site were determined to be: 

1. Determine fate and transport of applied chemicals. 

2. Evaluate the acute lethal effects of pesticides on aquatic organisms through 

toxicity testing. 

3. Evaluate the sublethal effects of pesticides on aquatic organisms. This entailed 

assessment of potential biochemical and/or physiological effects by toxicity 

testing. 

4. Evaluate the effects of pesticides on non-target aquatic biological communities. 

5. Determine the effect of repeated pesticide exposure on benthic 

macroinvertebrates. Community structure elements to be assessed include 

taxonomic, functional, and tolerance composition, along with abundance and 

diversity measures. 

6. Determine the effects of pesticide applications on the benthic macrophyte 

community and associated epiphytic macroinvertebrates. Effects could include 
Aquatic Pesticide Monitoring Program 

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pesticide drift and changes in water column chemistry from decomposition of 

aquatic vegetation. Community structure elements to be assessed for benthic 

macrophytes include taxonomic composition, frequency distribution, coverage, 

abundance, and diversity measures. Epiphytic macroinvertebrates were analyzed 

for the same community structure elements as the benthic invertebrates. 

7. Determine the effect of pesticide exposure on phytoplankton communities. 

Community structure elements to be assessed include taxonomic composition, 

abundance, and diversity measures. 

Annual Goals 

In 2002, the first year of the project, the sampling was mandated by the legal 

settlement to begin no later than July 1st

. To accomplish that goal, sampling was limited 

to preliminary studies of pesticide fate at selected sites for high priority pesticides. 

Measurements included chemistry water, tissue and sediment samples and sediment and 

water sampling. 

Year two incorporated a triad sampling approach recommended by the EPA 

(Barbour et al. 1999). This included synoptic sampling for chemistry, toxicity, and 

biological assessments data. Bioassessments focused on communities that are widely 

recognized as appropriate biological indicators of contaminant impacts: aquatic 

macroinvertebrates, macrophytes, and algal communities (US EPA 2003). Due to the 

diverse nature of the target pesticides and water-body types studied, the type of 

bioassessments conducted were specifically adapted for each pesticide sampling event. 

However, where possible all studies were similarly designed and the data obtained is 

directly comparable. The specific goals for the 2003 monitoring effort were: 1) to revisit 

appropriate sites studied in Phase 1, 2) perform chemical analysis and toxicity testing for 

all pesticides of interest, 3) expand the number of study sites, 4) implement 

bioassessment studies all locations, and 5) begin special studies to fill gaps in knowledge 

of target pesticide and selected adjuvant (surfactants) behavior. 

2004 efforts focused on special studies to answer questions raised during the first 

two years. The primary focus of these studies was nontarget organism impacts and 

potential long term impacts. 
Aquatic Pesticide Monitoring Program 

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It was decided that APMP’s monitoring goals would be most efficiently achieved 

by closely coordinating with current aquatic pesticide users during their pesticide 

application cycle. By closely tying the sampling events to a pesticide application, ‘worstcase’ scenarios could be investigated. Given the limited time and budget of the APMP, 

looking at such worst-case scenarios was felt to be a prudent approach. During years two 

and three, the ‘worst-case’ regime was augmented with longer term macroinvertebrate 

and phytoplankton bioassessment studies. These bioassessment studies allowed for a 

more comprehensive investigation into potential environmental impacts (chronic and 

acute) of aquatic pesticide applications. 

This “worst-case scenario” design explored the fate of pesticides applied at 

normal field concentrations and yielded data on both acute and longer term pesticide 

impacts. The sampling frequency enabled detection of potential biological responses as 

macroinvertebrates, and to a lesser extent, phytoplankton and macrophytes responded to a 

perturbation. 

A diverse range of water-body types located throughout California were 

monitored. The frequency and level of sampling varied because of pesticide and sitespecific issues (e.g. presence of other potential contaminants, availability of reference 

sites). The pesticides monitored included acrolein, 2,4-D (dimethylamine), copper 

sulfate, chelated copper (copper ethanolamine), diquat dibromide, fluridone, glyphosate, 

methoprene, and triclopyr (triethlyamine). Due to the extremely volatile nature of 

acrolein sampling for acrolein focused on developing field sampling methods to account 

for this volatility. Endothal was initially identified as a pesticide of interest, however, due 

to its limited use in California, no monitoring was conducted. 

A temporally stratified study design was implemented to coincide with pesticide 

application events. Samples were collected before pesticide application and at various 

post application increments (Table 4). We conducted quantitative sampling to enable 

spatial and temporal statistical comparisons. Sampling locations throughout the state are 

shown graphically in Figure 1. A graphic representation of sampling at a single site is 

shown in Figure 2. Table 5 is a complete list of all locations sample. 
Aquatic Pesticide Monitoring Program 

Final Report

17 

Reference Locations 

At each location where monitoring took place, a reference site was identified. 

The ideal reference site would have been an identical water body immediately adjacent to 

the treated water body that had never received applications. The closest to this ideal that 

was found in the Marin Municipal Water District system. 

The sites selected as reference sites were as similar as possible to the treated sites 

as possible minus the application of pesticide. In flowing water bodies, this was often 

immediately upstream of a treatment area. In lentic systems, an untreated portion of the 

water body was selected. As with the treated sites, these reference sites often received 

input from sources possibly containing contaminants in addition to the aquatic pesticide 

applied. Every attempt was made to select sites with minimal uncharacterized inputs. 

These sites served as reasonable reference locations for the chemistry and toxicity 

studies. 

However, for the benthic invertebrate studies, these reference sites were far from 

ideal. Most of the systems in California to which aquatic pesticides are applied are manmade, heavily altered, or highly impacted. Sites which would have minimally disturbed 

benthos are often remote and dissimilar to water bodies received treatment. 
Aquatic Pesticide Monitoring Program 

Final Report

18 

Table 4. Sampling frequency, collection order, and locations. 

Sample collection frequency 

Pre-application 

Initial Post-application (within 1-24 hrs)1

2 weeks post 

4-6 weeks post2

Order of Sample Collection 

1. Physical Habitat Assessment 

2. Water Quality Parameters 

3. Macrophyte Survey 

4. Sediment Parameters 

5. Macroinvertebrate Assessments 

1 Macrophytes and macroinvertebrates not collected at this time. 

2 For long-term sampling of copper sulfate, fluridone, and glyphosate only. 

Table 5. APMP Sampling Sites

Sampling Sites 

Cooperating Permit Holder /Treated Sites /Control Site / Pesticide 

Marin Municipal Water District / Bon Tempe and Nicasio Reservoirs / Lake Lagunitas / copper sulfate1

Cal. Dept. of Food and Agriculture / Costa Ponds / untreated pond / liquid fluridone1

U.S. FWS and Dept. of Boating and Waterways / Lower Stone Lake / Upper Stone Lake / glyphosate1

Sand Bay Isle Homeowners Association / Sand Bay Isle Ponds / diquat dibromide and copper sulfate 

U.S. FWS and Dept. of Boating and Waterways / treated Stone Lake slough / untreated slough / 2,4-D 

Solano Irrigation District / Byrnes canal / untreated canal section / chelated copper 

Potter Valley Irrigation District / treated canal / untreated canal section / chelated copper 

Big Bear Municipal Water District / treated lake area / untreated lake area / pelleted fluridone 

Merced Irrigation District / Atwater Canal / untreated canal section / glyphosate 

Merced Irrigation District / Main Canal / untreated canal section / liquid fluridone 

Merced Irrigation District / LeGrande & Planada Canal / untreated canal section / acrolein 

Merced Irrigation District / Livingston Canal / untreated canal section / acrolein 

Ventura County Flood Control District / Doris Drain storm water canal / untreated section / glyphosate 

Cal. Dept. of Food and Agriculture / Bear Creek / untreated creek section / triclopyr 

Dept. of Boating and Waterways / Delta 7 Mile slough / untreated slough area / diquat dibromide 

Cal. Dept. of Food and Agriculture / Clear Lake / untreated lake portions / pelleted fluridone 

Cal. Dept. of Food and Agriculture / Anderson Pond / pretreatment / triclopyr 

Contra Costa Mosquito VCD / Swanton’s Marsh / untreated marsh area / methoprene 

1 Long-term study sites. 
Aquatic Pesticide Monitoring Program 

Final Report

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Figure 1. APMP Sampling Locations. 
Aquatic Pesticide Monitoring Program 

Final Report

20 

Figure 2. Typical Sampling Plan for an Individual Site 

Sample Collection Methods 

Standard protocols for chemistry and toxicity sampling and handling have been 

compiled in the Aquatic Pesticide Monitoring Program Quality Assurance Project Plan 

(QAPP) (Yee et al. 2004). This document was reviewed by the USEPA Region 9 Quality 

Assurance office. The bioassessment methods and results are detailed in Hayworth et al.

2004. These methods follow those developed by the California Department of Fish and 

Game and were adapted for the specific systems being monitored. 

Data Management 

All digital data and information generated from sampling are stored at SFEI in a 

California State Water Resource Control Board Surface Water Ambient Monitoring 

Program (SWAMP) format. All data and reports are publicly available at SFEI’s 

website. 
Aquatic Pesticide Monitoring Program 

Final Report

21 

Approach to Risk Assessment 

Chemical characterization, toxicity tests and benthic and epiphytic test results 

were reviewed for trends that may indicate impacts due to aquatic pesticide applications. 

When sufficient data was available, we used the sediment quality triad approach for 

evaluating pesticide-contaminated sediments proposed by Chapman et al. (1991) and 

used in Canfield et al. (1994). In some cases, there was insufficient data to perform 

sediment quality triad calculations. In these cases, risk quotients were calculated for a 

range of test species. Where discrepancies occurred, they are highlighted in the text. The 

ultimate goal of this data interpretation is to identify for regulators areas that may need 

regulatory attention or additional research. These results in and of themselves can not 

provide definitive information on a particular pesticide’s behavior in the environment. 

Sediment Quality Triad Approach

The triad approach is an effects-based approach that integrates measures of 

chemistry, sediment toxicity, and benthic community structure, to evaluate sediment 

quality in aquatic and marine systems. Metrics used to evaluate chemistry were the 

concentration of applied pesticide, in sediment (if available) and pore-water. Mean 

growth and percent survival of Hyalella azteca (10-d exposure) were the preferred 

metrics to evaluate whole-sediment toxicity. However, if these data were unavailable, 

substituted animal or plant toxicity metrics were applied. The number of chironomid 

genera and species richness were used to evaluate benthic community structure. We 

chose to rank chemistry, toxicity, and benthos using procedures developed by Kreis 

(1988) and used by Canfield et al. (1994). Accordingly, values for each individual 

variable for all stations (included reference) were scaled proportionally between 0 and 

100 (e.g. 100 is the highest toxicity measured). The toxicity rank was determined by 

summing the ranks for both toxicity variables and re-ranking the results. 

The criterion for evaluating chemistry was a concentration of pesticide or metal 

that exceeded either the risk quotient for sediment or the toxicity endpoint for an aquatic 

species in porewater (see Table 6). The criterion for elevated toxicity was a significant 

decrease in either of the toxicity variables used, relative to the control. The criterion for 

impacted benthos was either a Chironomidae genera richness or species richness value 

that was significantly different from the mean of the respective reference stations. A 
Aquatic Pesticide Monitoring Program 

Final Report

22 

significant difference in benthos was tested using a two-sample t-test between each 

treated station and all reference stations. 

Table 6. Threshold Values Applied in Chemistry Evaluation after Siemering (2004). 

Metal or Pesticide Sediment 

Threshold 

Sediment 

Threshold 

References 

Pore-water 

Threshold 

Porewater 

Threshold 

Reference 

Copper Sulphate LC50 (Hyallela 

azteca) - 262 μg/g 

Suedel et al 1996 LC50 (H. azteca) –

0.035 mg/l 

Suedel et al 1996 

Chelated Copper LC50 (Hyallela 

azteca) - 262 μg/g 

Suedel et al 1996 LC50 (H. azteca) –

0.035 mg/l 

Suedel et al 1996 

Fluridone N/A EC50 (Stonewort) 

– 0.20 mg/l 

Burkhart and 

Stross 1990 

2,4-D N/A LC50 

(Chironomus 

plumosus) – 100 

mg/l 

Washington, Dept. 

of Ecology 2001 

Risk Quotient Calculation

Risk quotients were calculated according the method promulgated by the USEPA 

(USEPA, 1998). These risk quotients are part of the first step of a four part risk 

characterization process outlined in the ECOFRAM draft Aquatic Report (USEPA, 

1999). This report states, 

“The purpose of the tiered process is to provide a logical progression of tests and 

risk assessment approaches to address the potential risks of toxicants to aquatic 

systems. The common feature of all tiered regulatory processes is a progression 

beginning with conservative assumptions and moving toward more realistic 

estimates. Tiered processes tend to be cost effective in that they ensure that 

resources are expended on pesticide product/issues meriting attention. ... The 

tiers are differentiated primarily by the data available at that state in the risk 

assessment process and the relative cost of achieving risk refinement appropriate 

for that tier of analysis.” 

Risk quotients were calculated in order to identify where additional risk 

characterization work may be needed to fully explore potential impacts of aquatic 

pesticides. They only indicate where additional information may be needed and, in and 

of themselves, do not indicate impacts. 
Aquatic Pesticide Monitoring Program 

Final Report

23 

In order to integrate water exposure information with water toxicity information, 

risk quotients (RQs) are calculated by dividing water chemical concentrations by an acute 

or chronic ecotoxicity value: Toxicity

Exposure RQ = (USEPA, 1998). 

Exposure = an estimated environmental water concentration or actual water 

concentration field data. 

Toxicity = an accepted toxicity measurement (i.e. LC50, LD50, EC50, EC25, 

NOEC, LOEC, or MATC). 

The RQs calculated in this document used the highest pesticide concentration 

experimentally determined during our monitoring of the applications of a particular 

pesticide. The use of these peak values is appropriate for a Tier 1 risk characterization as 

such a characterization is meant to be protective, not predictive, and is therefore based on 

conservative (i.e. worst-case) assumptions about potential exposure and effects. If 

possible risk is identified in a Tier 1 analysis, then a Tier 2 analysis (addressing the 

probability and magnitude of effects on sensitive species using conservative exposure 

scenarios) is indicated. Tier 2 analysis was not performed as part of this project. 

The calculated RQs are then compared to a Level of Concern (LOC) determined 

by the USEPA Office of Pesticide Programs (OPP). The specific LOCs for aquatic 

animals and plants are shown in Table 7. LOCs are unit less values that allow for simple 

determination of possible exceedances of regulatory limits. An LOC exceedance is 

indicative only of the need for further investigation of an application scenario. 

Table 7. Aquatic Animal and Plant Levels of Concern 

Risk Presumption RQ LOC 

Acute Risk EC/LC50 or EC50 0.5 

Acute Restricted Use EC/LC50 or EC50 0.1 

Acute Endangered Species EC/LC50 or EC50 0.05 

Chronic Risk EC/ MATC or NOEC 1 

The USEPA interprets exceedances of LOCs as follows: 

Acute high risk: potential for acute risk is high; regulatory action may be 

warranted in addition to restricted use classification 

Acute restricted use: the potential for acute risk is high, but this may be mitigated 

through restricted use classification 
Aquatic Pesticide Monitoring Program 

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24 

Acute endangered species: the potential for acute risk to endangered species is 

high, but this may be mitigated through restricted use classification 

Chronic risk: the potential for chronic risk is high; regulatory action may be 

warranted 

Values for standard toxicity test species will be used, as will values for any listed 

species present. Where there are multiple toxicity values for the same test species, the 

lowest value will be selected. The toxicity measurements used are from peer-reviewed 

academic literature, FIFRA registration documents, or other government reports. 

Risk quotients are also calculated for sediment pesticide concentrations where 

toxicity values are available. However, the USEPA LOCs are not applicable to sediment 

pesticide concentrations and there are no comparable regulatory values for sediment. 

Results 

2,4-D 

U.S. Fish and Wildlife Service employees applied the herbicide Weedar 64 (2,4-D 

dimethylamine salt) mixed with R-11 surfactant (a nonylphenolethoxylate surfactant) to a 

main stem slough of South Stone Lake within the Stone Lake National Wildlife Refuge 

(SLNWR) on September 8, 2003. 2,4-D (DMA) and 2,4-D (BEE) are both registered for 

aquatic use, but have different toxicological properties making it important to 

differentiate between the compounds when reviewing data. Portions of South Stone Lake 

are repeatedly treated with 2,4-D and surfactant during the summer and early fall to 

control heavy infestations of water hyacinth (Eichornia crassipes). Different sections of 

this lake are treated with glyphosate for hyacinth control. The 2,4-D is applied to the 

emergent vegetation via an automated spray nozzle water pump system mounted on an 

airboat. The study area was approximately 0.15-acres, densely covered by hyacinth, with 

a sand/silt-consolidated substrate. The application rate at the site was 30 liquid ounces of 

herbicide per 50 gallons water. The nonylphenol surfactant was added to the pesticide 

tank mix. 

Tables 10 and 11 summarize the sediment quality triad measurements for the 2,4-

D application at SLNWR. This data indicates that there is no evidence of pesticide 
Aquatic Pesticide Monitoring Program 

Final Report

25 

induced degradation at either of the sampling locations. In addition, no LOCs were 

exceeded by the maximum 2,4-D concentration measured (Table 8). 

However, the R-11 surfactant concentration was four times the acute endangered 

species LOC for Delta smelt (Table 9). Seeing an LOC exceedance for R-11 (a 

nonylphenol containing surfactant) is not unexpected given that the R-11 LC50 for Delta 

smelt is an order of magnitude lower than the 2,4-D Delta smelt LC50. 

Table 8. Peak Concentration Risk Quotient Calculations for 2,4-D Application 

Experimental 

Concentration 

Range 

Toxicity 

Value 

Toxicity measurement, 

regulatory tolerance, 

action or guidance value 

Risk Quotient RQ exceeds LOC 

or other regulatory 

guideline? 

27.5 μg/l 315 μg/l Chinook salmon LC50 0.087 No 

7.2 mg/l D. magna LC50 0.0038 No 

100 mg/l P. promelas LC50 0.000275 No 

128 mg/l Delta smelt NOEC 0.000215 No 

Table 9. Peak Concentration Risk Quotient Calculations for Surfactant (R-11) during 2,4-D 

Application. 

Experimental 

Concentration 

Range 

Toxicity 

Value 

Toxicity measurement, 

regulatory tolerance, 

action or guidance value 

Risk Quotient RQ exceeds LOC 

or other regulatory 

guideline? 

22.6 μg/l 5700 μg/l C. dubia LC50 0.004 No 

420 μg/l C. dubia NOEC 0.05 No 

1100 μg/l P. promelas LC50 0.02 No 

340 μg/l P. promelas NOEC 0.06 No 

700 μg/l Delta smelt LC50 0.03 No 

100 μg/l Delta smelt NOEC 0.2 Yes (Acute 

Endangered) 

3900 μg/l Sacramento splittail LC50 0.006 No 

1900 μg/l Sacramento splittail NOEC 0.01 No 

APMP research has indicated that 2,4-D alone and in combination with a 

nonylphenol surfactant may cause endocrine disruption in juvenile O. mykiss at labelapproved application rates. Work is continuing to determine if 2,4-D itself is an 

endocrine disruptor or if dichlorophenol (a primary 2,4-D breakdown product) is the 

source of the vitellogenin induction. 
Aquatic Pesticide Monitoring Program

Final Report

26

Table 10. Sediment Quality Trend Calculations for 2, 4-D (DMA)

Site Station

2,4-D

porewater rank

Amphipod

Mean

Length rank

Amphipod %

Survival rank

Toxicity

Rank

Numbe

Chironom

Gene

Stone Lake SL2-01 0.49 96 0.39 0 96.25 0 0 6.00 Stone Lake SL2-02 0.00 0 0.25 100 96.25 0 54 2.00 

Pre-App 0.51 100 0.27 85 88.75 100 100 10.00 

Data are an average of individual replicates at pre-app (reference) vs. 2wk (each treated station)

Chemistry, toxicity, and benthos are scaled proportionally between 0 (e.g. low toxicity) and 100 (e.g. high toxicity)

Toxicity and Benthos (species richness only) are reverse ranked to reflect assumed relationship to metal application

The toxicity rank is the combined ranking of both mean length and percent survival ranks for Hyalella azteca

Table 11. Summary of 2, 4-D (DMA) Sediment Quality Trend Data

Chemistry Toxicity Benthos Stone Lake (2,4-D) 2003 Possible Conclusion

+ + + Evidence of pesticide-induced degrad

- - - SL201, SL202 No evidence of pesticide induced degr

+ - - Pesticides are not bioavailable

- + -

Chemicals other than pesticide or conditions exist w

degradation

- - + Benthic response not due to pestic

+ + - Pesticide may be stressing the sys

- + + Chemicals other than pesticide or conditions are c

+ - + Pesticide is not bioavailable or benthic response is 

A plus(+) for chemistry indicates a metal concentration that exceeded either the porewater LC50 reported for Chironomus plumosus

A plus(+) for toxicity indicates a significant decrease relative to control in either amphipod growth or percent survival

A plus(+) for benthos indicates either a chironomid genera richness or total species richness value that was significantly different from 
Aquatic Pesticide Monitoring Program 

Final Report

27 

Copper Sulfate 

Copper sulfate was monitored in all three years of the project at four reservoirs in 

Marin Municipal Water District (MMWD). Copper sulfate is applied to the Marin 

reservoirs for floating and benthic algae control. 

Two reservoirs received copper treatments (Nicasio and Bon Tempe Reservoirs) 

and two untreated reservoirs were used at reference locations (Soulajule Reservoir and 

Lake Lagunitas). Soulajule Reservoir was only sampled during year one. Nicasio and 

Soulajule reservoirs are located in the West Marin watershed. Lake Lagunitas and Bon 

Tempe reservoir are located in the Mount Tamalpais watershed. Nicasio Reservoir was 

treated for floating algae with copper sulfate applied by dissolution of granular copper 

sulfate through burlap bags towed with a boat. Bon Tempe Reservoir was treated with 

granulated copper sulfate for benthic algae control. Granulated copper was applied with 

a hopper mounted to the side of a boat. Soulajule Reservoir has never been treated with 

copper and Lake Lagunitas has not been treated since the 1920s. 

Tables 13 and 14 summarize the sediment quality triad measurements for the 

copper sulphate applications in the MMWD. This analysis indicates that multiple 

stations in Bon Tempe reservoir show evidence of copper induced degradation. The 

impacted locations vary between years of data collected mostly likely due to the variation 

of sediments within the samples areas. In Nicasio reservoir, while no sites exhibited 

degradation of all three lines of data, three sites did show the potential for ecosystem 

impacts. 

Experimental concentrations and risk quotients are summarized in Tables 12.

Table 12. Water Risk Quotient Calculations for Copper Sulfate Applications (Reservoir System) 

Toxicity 

Value 

Toxicity 

measurement or 

guidance value 

Risk Quotients 

(Risk quotients in bold and underlined 

indicate an LOC exceedance) 

Peak 

Concentration 

t+24 hour 

conc. 

t+1 week 

conc. 

0.0653 mg/l 0.0381 mg/l 0.0076 mg/l 

0.068 mg/l C. dubia EC50 0.96 0.56 0.11

0.03 mg/l Daphnid NOEC 2.18 1.27 0.25 

0.8 mg/l Rainbow Trout 

48hr LC50 

0.08 0.048 0.0095 

2300 mg/l Duckweed EC50 .00003 1.6E-5 3.3E-6 
Aquatic Pesticide Monitoring Program 

Final Report

28 

Water toxicity testing in Bon Tempe found acute water toxicity to O. mykiss and 

acute and chronic toxicity to C. dubia shortly after copper application. Water toxicity 

was found at all time intervals after application. Inhibition of C. dubia reproduction was 

the primary toxicity detected, but the magnitude of toxicity did not always reflect the 

measured copper concentrations in the water. The most significant reproductive and 

mortality effects took place immediately after application. Significant trout mortality 

occurred in one sample collected immediately after application. The 24 hour and one 

week post application samples also inhibited reproduction of C. dubia although 

concentrations did not exceed the copper LOEC for inhibition. 
Aquatic Pesticide Monitoring Program

Final Report

29

Table 13. Sediment Quality Trend Calculations for Copper Sulphate

Site Station

Copper

Sed rank

Copper

porewater rank

Amphipod

Mean

Length rank

Amphipod %

Survival rank

Toxicity

Rank

Numb

Chirono

Gen

Bon Tempe B-01 2390.00 89 0.05 100 0.08 73 68.00 100 100 4.0Bon Tempe B-02 733.67 26 0.04 79 0.13 27 99.00 0 1 2.0

Bon Tempe B-03 2693.33 100 0.05 98 0.07 89 82.50 53 79 2.8

Bon Tempe B-04 687.00 24 0.01 25 0.06 100 85.00 45 81 4.3

Bon Tempe B-05 935.67 34 0.02 33 0.10 58 91.00 26 39 3.4Bon Tempe B-06 474.00 16 0.01 10 0.14 10 94.00 16 0 4.8

Lagunitas L-01 46.43 0 0.00 0 0.13 27 90.00 29 21 8.3

Lagunitas L-02 56.13 0 0.00 2 0.11 45 92.00 23 28 4.8

Lagunitas L-03 46.50 0 0.00 0 0.15 0 82.00 55 20 7.5

Bon Tempe B-01 682.00 55 0.00 0 0.17 97 95.33 6 52 6.3

Bon Tempe B-02 1200.00 100 0.03 55 0.17 100 81.60 100 100 7.3Bon Tempe B-03 437.00 34 0.01 3 0.21 79 94.50 12 45 8.6Bon Tempe B-04 449.67 35 0.00 0 0.17 96 85.00 77 86 6.6Bon Tempe B-05 338.50 26 0.02 53 0.19 88 87.00 63 76 7.3Bon Tempe B-06 388.50 30 0.00 0 0.22 75 95.50 5 40 8.0

Lagunitas L-01 40.60 0 0.04 100 0.37 0 96.25 0 0 9.0

Nicasio N-05 99.65 100 0.00 34 0.18 81 74.00 100 100 6.0

Nicasio N-06 38.75 15 0.00 19 0.22 10 93.50 19 0 6.5

Nicasio N-07 28.05 0 0.01 100 0.23 0 81.50 69 26 8.5

Nicasio N-14 56.60 40 0.00 21 0.16 100 90.00 33 69 8.0

Nicasio Ref N-11 59.2 44 0.00 0 0.21 29 98.00 0 0 7.0

Nicasio Ref N-13 52.90 35 0.00 10 0.19 55 90.00 33 39 6.0

Data are an average of individual replicates at each application time.

Chemistry, toxicity, and benthos are scaled proportionally between 0 (e.g. low toxicity) and 100 (e.g. high toxicity).

Toxicity and Species richness are reverse ranked to reflect assumed relationship to toxicity.

The toxicity rank is the combined ranking of both mean length and percent survival ranks for Hyalella azteca.
Aquatic Pesticide Monitoring Program

Final Report

30

Table 14. Summary of Copper Sulphate Sediment Quality Trend Data

Chemistry Toxicity Benthos 2003 Stations 2004 Stations Possible Concl

+ + + B01, B02, B04 B01, B02, B03, B04, B05 Evidence of copper-induc

- - - N07, N06, N14 No evidence of copper indu

+ - - B06 Copper is not bioa

- + - N05

Chemicals other than copper or conditio

degradatio

- - + Benthic response not d

+ + - B05 Metals may be stressin

- + + Chemicals other than copper or condit

+ - + B03 B06 Copper is not bioavailable or benthic res

A plus(+) for chemistry indicates a concentration of Cu that exceeded either the Sediment Quality Guideline ERL for Cu or porewater r1996.

A plus(+) for toxicity indicates a significant decrease relative to control in either amphipod growth or percent survival.

A plus(+) for benthos indicates either a chironomid genera richness or total species richness value that was significantly different from stations.

Aquatic Pesticide Monitoring Program 

Final Report

32 

Chelated Copper 

Chelated copper was monitored within the canal systems of Solano Irrigation 

District (SID) and Potter Valley Irrigation District (PVID). The chelated copper is 

applied to the ID canals for macrophyte and filamentous algae control. PVID applied 

Cutrine Plus® which is a copper ethanolamine mixture. SID applied Clearigate® which 

is a copper ethanolamine mixture in an emulsified formulation. Both products contain 

unique unspecified ‘inert ingredients’ that may cause them to have different 

environmental fates and toxicological properties. In the two irrigation district system 

canals monitored, the copper treatments consisted of chelated copper pumped into the 

canals as the water passed through a weir to aid in mixing. Each treatment lasted for a 2-

3 hours. 

Tables 16 and 17 summarize the sediment quality triad measurements for the 

chelated copper applications in Byrnes Canal. These measurements indicate that copper 

induced degradation is occurring at one site and may be stressing the system at the other 

site. 

Water toxicity testing in conjunction with these applications showed intermittent 

toxicity pre and post application. The peak water concentrations detected during the 

three applications exceed the LOCs. Experimental concentrations and risk quotients are 

summarized in Table 15.

Table 15. Water Risk Quotient Calculations for Chelated Copper Applications (Irrigation Canal 

Systems) 

Toxicity 

Value 

Toxicity 

measurement or 

guidance value 

Risk Quotients 

(Risk quotients in bold and underlined 

indicate an LOC exceedance) 

Peak 

Concentration 

t+4 hour 

conc. 

t+11 hour 

conc 

1.43 mg/l 0.0988 mg/l 0.0988 mg/l 

9.9 mg/l Water flea

Alonella LC50 

0.144 0.01 0.002 

0.0023mg/l Fathead Minnow 

larvae 48hr LC50 

621 43 7.39
Aquatic Pesticide Monitoring Program

Final Report

33

Table 16. Sediment Quality Trend Calculations for Chelated Copper

Site Station

Copper

Sed rank

Copper

porewater rank

Amphipod

Mean Length rank

Amphipod

% Survival rank

Toxicity

Rank

Number of

Chironomida

Genera 

Byrnes

Canal BC-01 609.00 100 0.01 0 0.17 68 58.00 32 50 18.00 

Byrnes

Canal BC-02 211.00 0 0.01 1 0.16 100 35.00 100 100 8.00 

Pre-App 565.50 89 0.13 100 0.20 0 69.00 0 0 11.00 

Data are an average of individual replicates at pre-app (reference all stations) vs. 2wk (per treated station)

Chemistry, toxicity, and benthos are scaled proportionally between 0 (e.g. low toxicity) and 100 (e.g. high toxici

Toxicity and Benthos (species richness only) are reverse ranked to reflect assumed relationship to metal applicati

The toxicity rank is the combined ranking of both mean length and percent survival ranks for Hyalella azteca

Table 17. Summary of Chelated Copper Sediment Quality Trend Data

Chemistry Toxicity Benthos Byrnes Canal 2003 Possible Conclusion

+ + + BC01 Evidence of copper-induced degradatio

- - - No evidence of copper induced degradat

+ - - Copper is not bioavailable

- + - BC02 Chemicals other than copper or conditions exist with potentia

- - + Benthic response not due to copper

+ + - Metals may be stressing the system

- + + Chemicals other than copper or conditions are causi

+ - + Copper is not bioavailable or benthic response is not d

A plus(+) for chemistry indicates a metal concentration that exceeded either the Sediment Quality Guideline ERL 

reported for Hyalella azteca

A plus(+) for toxicity indicates a significant decrease relative to control in either amphipod growth or percent sur

A plus(+) for benthos indicates either a chironomid genera richness or total species richness value that was signif

the reference stations
Aquatic Pesticide Monitoring Program 

Final Report

34 

Diquat Dibromide 

Diquat dibromide was sampled at two locations during the APMP. One location 

was at a homeowners association property where diquat was applied to treat sago 

pondweed by a local licensed pesticide applicator. The second location was in 7-Mile 

Slough in the Sacramento/ San Joaquin Delta where diquat was applied by Department of 

Boating and Waterways staff for control of Egeria densa.

Water chemical characterization and toxicity testing were conducted during both 

sampling events. Limited sediment monitoring was conducted because diquat adsorbs 

irreversibly to sediment and once bound is no longer considered bioavailable. 

At the Sand Bay site, diquat was found at 300 and 400 ppb immediately after 

application. This concentration was double that of the highest concentration found at 7-

Mile Slough (195 ppb). Peak water diquat dibromide concentration risk quotients 

exceeded LOCs at both applications. Interestingly, LOC exceedances were observed 

preapplication at the Delta site. This is indicative of diquat runoff from upstream urban 

and terrestrial applications. Experimental concentrations and risk quotients are 

summarized for diquat in Table 18. 
Aquatic Pesticide Monitoring Program 

Final Report

35 

Table 18. Water Risk Quotient Calculations for Diquat Dibromide Applications 

Toxicity 

Value 

Toxicity 

measurement or 

guidance value 

Risk Quotients 

(Risk quotients in bold and underlined indicate an LOC 

exceedance) 

preapplication conc. t+1 hour conc. t+24 hours conc. 

7-Mile: 13.8 μg/l 

Sand Bay: 0.79 μg/l 

7-Mile: 180 μg/l 

Sand Bay: 400 μg/l 

7-Mile: 4.5 μg/l 

19 μg/l S. capricornutum.

EC50 (growth) 

RQ7-Mile=0.73 

RQSand Bay=0.04 

RQ7-Mile=9 

RQSand Bay=21

RQ7-Mile=0.24 

44 μg/l Algae NOEC 

(biomass growth) 

RQ7-Mile=0.31 

RQSand Bay=0.02 

RQ7-Mile=4 

RQSand Bay=9

RQ7-Mile=0.1 

32 μg/l D. magna LC50 RQ7-Mile=0.43

RQSand Bay=0.025 

RQ7-Mile=5.6

RQSand Bay=13

RQ7-Mile=0.14

36 μg/l Daphnid NOEC RQ7-Mile=0.38 

RQSand Bay=0.02 

RQ7-Mile=5 

RQSand Bay=11

RQ7-Mile=0.125 

120 μg/l Minnow NOEC RQ7-Mile=0.115 

RQSand Bay=6E-3 

RQ7-Mile=1.5 

RQSand Bay=3.3

RQ7-Mile=0.038 

7600 μg/l P. promelas LC50 RQ7-Mile=0.0018 

RQSand Bay=1E-4 

RQ7-Mile=0.02 

RQSand Bay=0.05 

RQ7-Mile=6E-4 

11 μg/l Duckweed LOEC RQ7-Mile=1.25

RQSand Bay=0.72 

RQ7-Mile=16 

RQSand Bay=36

RQ7-Mile=0.4 

18 μg/l Duckweed EC50 RQ7-Mile=0.76

RQSand Bay=0.044 

RQ7-Mile=10

RQSand Bay=22

RQ7-Mile=0.25 
Aquatic Pesticide Monitoring Program 

Final Report

36 

Fluridone 

Fluridone (in the form of Sonar®)was monitored at multiple locations during the 

three years of the APMP. In 2002, a liquid fluridone application was monitored in 

Merced Irrigation District’s Main Canal and pelleted applications in Clear Lake. In 2003, 

pelleted fluridone applications to Big Bear Lake, in the San Bernardino mountains, and 

liquid fluridone applications to Costa Ponds, a fishing resort near Porterville California, 

were monitored. In 2004, more extensive sediment analysis of Clear Lake was conducted 

to investigate long term nontarget plant toxicity. Only at the Big Bear Lake and Costa 

Pond applications were sufficient data collected to performed sediment quality triad 

analysis. A Typha ssp seed germination and plant growth toxicity test was used for 

samples collected from Big Bear Lake, Clear Lake, and Costa Ponds. In addition seed 

germination rate, both the mean root and shoot growth are recorded as sublethal 

endpoints. 

Tables 20 and 21 summarize the sediment quality triad measurements for the 

fluridone applications to Big Bear Lake and Costa Ponds. These measurements indicate 

that fluridone induced degradation is occurring at three Costa Ponds sites and one Big 

Bear Lake Site. At other sites, some lines of evidence indicate ecosystems impacts. 

In 2004, multiple Clear Lake sediment and porewater samples were collected to 

investigate the potential long term toxicity to nontarget plant organisms. Clear Lake 

shore segments have been treated for different intervals over the preceding decade. 

Samples were collected from sites that had not been treated for a varying number of 

years. However, site conditions make it likely that fluridone containing sediment is 

constantly transported through the lake making toxicity test results inconclusive. 

Tissue samples (Sacramento suckers, crayfish, and rainbow trout) were collected 

during the Merced Irrigation District eight week application of liquid fluridone in their 

Main Canal. The data indicate that fluridone did accumulate in tissue during the 

applications and persisted two weeks following application. At four weeks after the 

cessation of treatment, tissue concentrations had returned to preapplication levels. No 

LOC exceedances were observed with the MID applications (Table 19)
Aquatic Pesticide Monitoring Program 

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37 

Table 19. Peak Risk Quotient Calculations for Fluridone Application at MID Main Canal 

Toxicity 

Value 

Toxicity 

measurement or 

guidance value 

Risk Quotients 

(Risk quotients in bold and underlined indicate an LOC 

exceedance) 

Preapplication 

concentration 

Mid Application Post Application 

Non Detect 37 μg/l 102 μg/l 

2.1 mg/l D. magna LC50 0 0.018 0.048 

200 μg/l D. magna NOEC 0 0.185 0.51 

6.2 mg/l P. promelas LC50 0 0.006 0.016 

1.88 mg/l P. promelas NOEC 0 0.02 0.054 

1.28 mg/l Delta smelt NOEC 0 0.029 0.08 
Aquatic Pesticide Monitoring Program

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38

Table 20 Sediment Quality Trend Calculations for Fluridone

Site Station

Fluridone

Pore Water rank

Typha Mean

Root Length rank

Typha %

Germination rank

Toxicity

Rank

Number of

Chironomidae

Genera ran

Costa Ponds CP-02 0.92 80 10.40 37 96.65 67 27 3.00 1Costa Ponds CP-03 1.16 100 9.20 100 98.90 0 21 2.67 Costa Ponds CP-04 0.84 73 11.10 0 95.55 100 21 2.33 Costa Ponds CP-05 1.03 89 10.15 50 95.55 100 100 2.00 Costa Ponds Ref CP-01 0.00 0 9.45 87 98.90 0 0 2.33 Big Bear BBP-01 0.18 9 8.40 100 100.00 0 100 7.00 Big Bear BBP-02 0.28 17 8.70 90 100.00 0 88 4.00 

Big Bear BBP-03 0.08 0 9.70 55 100.00 0 46 5.00 Big Bear BBE-01 0.99 78 10.80 17 100.00 0 0 4.00 Big Bear BBE-02 1.24 100 11.30 0 97.80 100 100 3.00 Big Bear Ref BBC-01 0.17 8 9.30 69 100.00 0 63 9.00 1

Data are an average of individual replicates at each application time

Chemistry, toxicity, and benthos are scaled proportionally between 0 (e.g. low toxicity) and 100 (e.g. high toxicity)

Toxicity and Benthos (species richness) are reverse ranked to reflect assumed relationship to toxicity

The toxicity rank is the combined ranking of both mean root length and percent germination for Typha latifolia

Table 21 Summary of Fluridone Sediment Quality Trend Data

Chemistry Toxicity Benthos Stations Possible Conclusion

+ + +

BBP02, CP02,

CP03, CP05 Evidence of pesticide-induced degradation

- - - No evidence of pesticide induced degradation

+ - - BBE01, BBE02 Pesticides are not bioavailable

- + - BBP01, BBP03 Chemicals other than pesticide or conditions exist with potential to 

- - + Benthic response not due to pesticide

+ + - Pesticide may be stressing the system

- + + Chemicals other than pesticide or conditions are causing d

+ - + CP04 Pesticide is not bioavailable or benthic response is not due 

A plus(+) for chemistry indicates a metal concentration that exceeded the porewater EC50 reported for Stonewort

A plus(+) for toxicity indicates a significant decrease relative to control in either plant growth or percent germination

A plus(+) for benthos indicates either a chironomid genera richness or total species richness value that was significantly different from 

Aquatic Pesticide Monitoring Program 

Final Report

40 

Glyphosate 

Glyphosate was monitored at four locations during the APMP. There were three 

canal sites; 1) Doris Drain, an agriculture return flow canal, near Ventura, 2) Merced 

Irrigation District’s Atwater Canal, and 3) an Orange County Public Works Department 

stormwater canal. Glyphosate applications were also monitored at Stone Lake National 

Wildlife Refugee. All applications were made with a tank mix of glyphosate and 

nonionic nonylphenolethoxylate surfactant. Triad monitoring was conducted only at 

SLNWR. 

Since glyphosate is considered to be biologically unavailable once it is sediment 

bound, only limited sediment quality data was gathered and sediment quality triad 

calculations were not performed. At all sampling sites, no acute or acute-restricted LOC 

exceedances occurred. All the sites where glyphosate was applied were lotic systems 

where chronic exposures could not have occurred. 

The Doris Drain application showed the highest glyphosate water concentrations 

(up to 1800 ppb immediately after treatment). No LOC exceedances for nontarget 

organisms were observed. However several exceedances were observed for the R-11 

surfactant applied in conjunction with the glyphosate (Table 22).

Table 22. Risk Quotient Calculations for Surfactant (R-11) during Glyphosate Application at Doris 

Drain. 

Toxicity 

Value 

Toxicity measurement or 

guidance value 

Risk Quotients 

(Risk quotients in bold and underlined 

indicate an LOC exceedance) 

preapplication 

conc. 

t+0 hour 

conc. 

t+3 hour 

conc. 

<RL μg/l 120 μg/l 19.6 μg/l 

5700 μg/l C. dubia LC50 0 0.021 0.003 

420 μg/l C. dubia NOEC 0 0.29 0.047 

1100 μg/l P. promelas LC50 0 0.11 0.018 

340 μg/l P. promelas NOEC 0 0.35 0.058 

700 μg/l Delta smelt LC50 0 0.17 0.028 

100 μg/l Delta smelt NOEC 0 1.2 0.196 

3900 μg/l Sacramento splittail LC50 0 0.031 0.005 

1900 μg/l Sacramento splittail NOEC 0 0.063 0.01 
Aquatic Pesticide Monitoring Program 

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41 

Methoprene 

Methoprene was monitored in conjunction with an application made to a tidally 

influenced wetland (Swanton’s Marsh) near the town of Martinez. The wetland is 

situated between the Tesoro Corporation refinery and the Concord Naval Weapons 

station. The wetland is fed from inland streams that also flow through methoprene 

treated marshes upstream. Normally Swanton’s marsh is treated with a mixture of 

methoprene and Bacillus thuringiensis israelensis, but for the benefit of this research the 

Contra Costa Mosquito Vector control district modified their application routine and only 

methoprene was applied. 

This is the only site where an insecticide was monitored during the APMP. 

Therefore, the methods used at this site differ significantly from those at the herbicide 

monitoring locations. At this site, water, porewater, and sediment chemical 

characterization, laboratory sediment toxicity testing, and in-situ sediment toxicity testing 

were performed. The laboratory toxicity test used larval insect Chironomus tentans in 

10-day survival and growth tests. The C. tentans are more sensitive to methoprene than 

H. azteca.

In addition, in-situ H. azteca toxicity tests were performed. The literature review 

and conversations with mosquito vector control scientists indicated that methoprene had a 

short window of bioavailability after application. To attempt to conduct a test within the 

methoprene breakdown time frame, it was felt to be worthwhile to attempt in-situ

exposures. The test method was modified from the EPA standard H. azteca test 

methodology by UC Davis Marine Pollution Studies Laboratory scientists. 

Methoprene was not detected in any water samples collected from the site. 

Methoprene is known to degrade quickly in water and sunlight. The day sampling 

occurred no clouds were present and the temperature was over 100F. 
Aquatic Pesticide Monitoring Program 

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42 

Methoprene was detected in all sediment (including preapplication and reference 

site) porewater samples. The concentrations ranged from 11.6-22.6 ppb. Methoprene was 

found in the sediments at concentrations ranging from 178-2080 ppb. At the reference 

site, the methoprene concentration was 178 ppb preapplication and 1800 ppb 4 days after 

application. The reference site is highly influenced by tidal flow and receives sediment 

from upstream locations. These upstream locations are treated with methoprene, but are 

not immediately adjacent to the reference site. Peak water methoprene concentration risk 

quotients did not exceeded LOCs. Experimental concentrations and risk quotients are 

summarized in Table 23.

Swanton’s marsh is treated with methoprene approximately twice a month. The 

fact that methoprene was found pre-application indicates that it is persistent in the soil for 

at least several weeks. USEPA methoprene reregistration documents state that 

methoprene is persistent in the soil for up to 10 days, is tightly bound to soil, and is 

degraded primarily by microbes (USEPA 1982). 

Table 23. Peak Concentration Risk Quotient Calculations for Methoprene Application 

Experimental 

Concentration 

Range 

Toxicity Value Toxicity measurement, 

regulatory tolerance, 

action or guidance value 

Risk Quotient RQ exceeds LOC 

or other regulatory 

guideline? 

Porewater 

22.6 μg/l 2 μg/l M. bahia LOEC 11.3 Yes 

1250 μg/l H. azteca LC50 0.018 No 

The C. tentans toxicity test results were inconclusive. Significant mortality was 

seen at the two treated sites pre-application and post application. Significant growth 

reduction was seen in the samples collected at all three sites pre and post application. 

Many of the sediments from this site were highly anoxic. It is likely that the anaerobic 

nature of the sediments were the cause of the significant growth reductions and mortality 

seen. Dissolved oxygen concentrations at the three sites averaged 3.6 mg/l. Total 

ammonia concentrations ranged from 11.6-4.0 mg/l (average 8.54 mg/l). Total sulfide 

ranged from 0.21-<0.01 (average 0.1 mg/l). 

The in-situ H. azteca tests were also inconclusive. H. azteca were healthy at 96 

hours, but the majority of test organisms were dead after 10 days. The test animals could 

have died due to environmental conditions (anoxia) or lack of food in the 10-day 

exposures. 
Aquatic Pesticide Monitoring Program 

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43 

The inconclusiveness of the two types of toxicity tests at this site highlight the 

difficulty of conducting monitoring at such a site. Methoprene is applied to control larval 

mosquitoes. The preferred habitat for the mosquito larvae is very shallow still waters. 

Such a water environment often leads to anaerobic water and sediment. 

Triclopyr 

California Department of Food and Agriculture (CDFA) personnel applied 

Renovate® triclopyr triethylamine salt at Bear Creek in 2003. A one percent triclopyr 

and 0.5 percent Target Prospreader Activator (TPA), a surfactant, by volume solution 

was applied to an approximately 0.34-acre creek section for the control of dense native 

water primrose (Ludwigia sp.). The herbicide tank mix was applied with a backpack 

hand-pump sprayer to the surface of the floating vegetation mats. As triclopyr had only 

recently received its aquatic use label, the number of applications made during the APMP 

were very limited. 

Although triclopyr is likely to partition to sediment, sediment was not collected at 

this site because the creek bed was predominantly cobbles covered by a fine layer of silt. 

The cobbles made it impossible to collect enough sediment for analysis with a sediment 

sampler. The layer of silt present was too thin to gather enough sediment for analysis by 

any other means. This lack of sediment data made it impossible to conduct sediment 

quality triad analysis of the application. 

Water chemistry results indicated that there were no triclopyr risk quotient LOC 

exceedances. Water toxicity tests were inconclusive due to sampling error. 

Nonylphenolethoxylate surfactant was found in the creek water both pre and post 

application (Table 24). Upstream sources could not be identified. The post application 

samples showed continuous increases in concentration with the maximum value at 24 

hours after application (2390 ppb). This peak could be due to additional upstream inputs, 

or a dispersion pattern different from that of triclopyr. The surfactant risk quotients show 

LOC exceedances pre and post application for a variety of aquatic animal species. 

Table 24. Risk Quotient Calculations for Surfactant during Triclopyr Application. 

Toxicity 

Value 

Toxicity measurement or 

guidance value 

Risk Quotients 

(Risk quotients in bold and underlined indicate 

an LOC exceedance) 

preapplication t+0 hour t+2 hours t+24 
Aquatic Pesticide Monitoring Program 

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44 

conc. conc. conc. hours 

conc. 

570 μg/l Non Detect 185 μg/l 2390 

μg/l 

5700 μg/l C. dubia LC50 0.1 0 0.032 0.42

420 μg/l C. dubia NOEC 1.36 0 0.44 5.7

1100 μg/l P. promelas LC50 0.52 0 0.17 2.17

340 μg/l P. promelas NOEC 1.68 0 0.54 7.03

700 μg/l Delta smelt LC50a 0.81 0 0.26 3.41

100 μg/l Delta smelt NOEC a 5.7 0 1.85 23.9

3900 μg/l Sacramento splittail LC50 a 0.15 0 0.047 0.61

1900 μg/l Sacramento splittail NOEC a 0.30 0 0.097 1.26 a.

Delta smelt and Sacramento splittail toxicity data for R-11. TPA and R-11 have very similar chemical 

and toxicity characteristics. 

CONCLUSIONS 

Use of the limited data gathered during the three pesticide application seasons that 

the APMP has existed should be limited to screening purposes only to identify where 

further risk characterization or research may be needed. APMP generated chemical 

characterization, toxicity, and bioassessment data. The chemical characterization and 

toxicity data generated can be used for screening purposes. In complex field situations, 

bioassessments require multiple years of data before even preliminary conclusions can be 

drawn from them. 

Specific conclusion concerning individual pesticides: 

2,4-D

Only one application of 2,4-D (in the 2,4-D dimethylamine salt formulation) with 

added surfactant was monitored. At this single application, no toxicity was observed nor 

did risk quotients indicate the need for further information. Vitellogenin induction 

laboratory experiments indicate that 2,4-D may cause endocrine disruption at legal 

application rates. 

The vitellogenin induction studies indicates the need for further study of the 

aquatic 2,4-D formulations and their primary breakdown products. This level of research 

should not be expected from entities conducting compliance monitoring. 

Acrolein
Aquatic Pesticide Monitoring Program 

Final Report

45 

Because of acrolein’s rapid volatilization, work focused on development of a field 

sampling method that would allow for accurate determination of the pesticide in water. 

Current standard environmental sampling methods are inadequate for sampling of 

acrolein treated water and result in unbelievable analytical results. 

Refinement of the sampling methodology began in 2003. Results indicate that the 

method developed works well at low acrolein water concentrations. This refined method 

makes it possible to determine acrolein residue values. 

Due to acrolein’s rapid volatilization, it is currently not possible to conduct 

standard water toxicity tests on it. Because of its’ extremely low Lowest Observable 

Effect Concentration (LOEC) values, the detectable presence of acrolein indicates that 

very high mortality to EPA water and sediment toxicity test species can be assumed. 

The development of diagnostic response tests (i.e. phytomonitoring, sentinel 

bivalves and fish, etc.) were explored and additional work is warranted. These tests have 

the potential to provide a low cost, low tech method of detecting acrolein outside of 

designated treatment areas. 

Copper Sulfate

Copper sulfate applications were monitored in three reservoirs. In one reservoir 

treatment area treated with dissolved copper sulfate, toxicity to juvenile trout and 

Ceriodaphnia immediately after and, in some cases, up to a week following application. 

Peak concentration risk quotients showed acute and chronic U.S. EPA Office Pesticide 

Programs Levels-of-Concern (LOC) exceedances. At 24 hours post application the risk 

quotients showed acute and chronic LOC exceedances. At one week post application the 

risk quotients showed acute LOC exceedances. 

In the reservoir treated with granular copper sulfate applications, significant 

mortality was observed in Ceriodaphnia and juvenile trout water toxicity tests 

immediately after application within the treatment area. Mortality and growth inhibition 

was also observed in a number of the sediment samples. Sediment copper concentrations 

at many sites exceeded a published Hyallela LC50 value. However, the toxicity observed 

in the sediments indicates that the majority of the copper is not bioavailable. 
Aquatic Pesticide Monitoring Program 

Final Report

46 

These findings indicate the need for further risk characterization associated with 

copper sulfate applications. 

Chelated Copper

Chelated copper pesticides were monitored during applications in two irrigation 

canal systems. One system used a product of mixed copper ethanolamines and the other 

the same product of mixed copper ethanolamines in an emulsified formulation. Chelated 

copper formulations are likely to have distinct behavior from copper sulfate and each 

other in aquatic environments based on the chelating agent and other adjuvants. It should 

be noted that copper carbonate is the active ingredient in other chelated copper products 

and no monitoring of copper carbonate based pesticides was conducted. 

In both systems where monitoring occurred, the water samples were almost 

uniformly toxic preapplication and post application. Therefore, no definitive conclusions 

can be drawn about the toxicity of mixed copper ethanolamines. The sediment quality 

triad calculations indicate the possibility of copper impacts to the system. 

Further risk characterization associated with chelated copper applications is 

warranted. 

Glyphosate

Glyphosate was monitored at several locations. No toxicity was found to be 

associated with glyphosate applications. Glyphosate is very often applied with a 

surfactant which may have much higher toxicity than the active ingredient. 

Based on risk quotient calculations and toxicity data, no further risk 

characterization associated with glyphosate applications alone is warranted. Risk 

characterizations are warranted when a surfactant used in conjunction with the 

glyphosate. 

Diquat Dibromide

Diquat dibromide was sampled at two locations, one small pond and a delta 

slough. Diquat risk quotients almost uniformly exceeded Levels of Concern at all 

sampling periods in the Delta slough (including preapplication) and at one hour after 

application in the pond. Diquat may be applied with a surfactant which may have much 
Aquatic Pesticide Monitoring Program 

Final Report

47 

higher toxicity than the active ingredient. Diquat sediment concentrations were not 

considered as diquat is irreversibly adsorbed to sediments and thereafter not bioavailable. 

Toxicity test and risk quotient results indicate the need for further risk 

characterization. 

Fluridone

Fluridone (applied in pellet or liquid form) was not found to be definitively toxic 

to or have LOC exceedances for the USEPA three species water or sediment amphipod 

organisms. The peak concentration risk quotient for Stonewort did exceed an Acute 

LOC. Fluridone was found to cause sublethal toxicity (decreased shoot and root length) 

to Typha. This would indicate a potential for impacts on nontarget plants. 

Further risk characterization of fluridone impacts on nontarget plants is 

warranted. There is also cause for concern over development of genetic resistance to 

fluridone which is emerging in plant populations in Florida. 

Methoprene:

Monitoring for methoprene is challenging because it is commonly applied to 

environments that do not lend themselves to traditional water and sediment sampling and 

testing methods (i.e. extremely shallow water and highly anoxic sediments). In situ and 

laboratory toxicity tests were completed, but the results were inconclusive. From the one 

site monitored for methoprene, water and porewater risk quotients indicate no need for 

further risk characterization. Methoprene was persistent in marsh sediments, up to the 

ppm level, for several weeks. Little methoprene sediment toxicity data could be located. 

Future work is warranted to further characterize the risk of methoprene in 

sediments. Additional studies may also be warranted due to the common simultaneous 

application of methoprene and Bti. 

Triclopyr

Triclopyr was monitored at one application only. Triclopyr peak concentration 

risk quotients show no LOC exceedances. Triclopyr is often applied with a surfactant 

which may have much higher toxicity than the active ingredient. 
Aquatic Pesticide Monitoring Program 

Final Report

48 

Limited further triclopyr risk characterization is warranted. Risk characterizations 

are warranted when a surfactant is used with triclopyr. 

Nonionic surfactants

The most commonly used surfactants at APMP monitoring sites were Target 

Prospreader Activator and R-11. Both are nonylphenolethoxylate based surfactants. 

Peak concentration risk quotients indicate exceedances of LOCs for a wide range of 

animal species including Delta Smelt and Sacramento Splittail. Vitellogenin induction 

experiments in Rainbow trout indicate that these nonylphenol surfactants can be an 

endocrine disruptor at application rates. There are a wide range of surfactants available, 

each one having a different toxicological profile. Due to their classification as an 

adjuvant, very little data is required for registration. Risk characterizations are warranted 

on all surfactants. 

MANAGEMENT AND ASSESSMENT QUESTIONS REVISITED 

The Management and Assessment questions developed at the beginning of the project 

were referred to throughout the planning and implementation of the APMP. Below is the 

analysis of how well the APMP addressed each Management question. 

1. Which aquatic pesticides used in California have the highest “risk” of impacts to 

people and the environment? The literature review and field monitoring activities 

have answered this question. 

2. What are the concentrations of the target aquatic pesticides in the environment 

(water, sediment, and biota) adjacent to their application point? The field 

monitoring activities have begun to answer this question for the aquatic pesticides 

of interest.

3. Are the measured concentrations above existing effects thresholds? This question 

has been answered for the sites studied by comparison of collected field data with 

published effects thresholds.

4. Which locations have the highest “risk” of beneficial use impairment? This 

question was not specifically addressed as it was a sufficient challenge to find 
Aquatic Pesticide Monitoring Program 

Final Report

49 

sites suitable for monitoring that met the other selection criteria. Bioassessment 

data indicates that all locations samples may be considered degraded.

5. What is the degree of biological impacts to non-target biota from application and 

exposure to aquatic pesticides? The bioassessment and special toxicity tests 

performed addressed this question. 

6. What Best Management Practices are currently being used to mitigate potential 

impacts from aquatic pesticide application? Pesticide application BMPs were not 

evaluated as part of this project. Non-chemical pest control alternatives have been 

studied extensively.
Aquatic Pesticide Monitoring Program 

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50 

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