Environmental Persistence and Toxicity of Weathered Wildland Fire Retardants to Rainbow Trout

doi:10.21203/rs.3.rs-5829115/v1

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Research Article

Environmental Persistence and Toxicity of Weathered Wildland Fire Retardants to Rainbow Trout

https://doi.org/10.21203/rs.3.rs-5829115/v1

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published 14 May, 2025

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Long-term fire retardants are employed to combat and control wildfires by altering the way fuels burn, and they continue to decrease fire intensity after water in the retardant solution has evaporated. After application, fire retardants may persist on dry stream beds or in riparian habitats before precipitation events flush the retardant into intermittent streams. We exposed juvenile (30-60 days post swim-up) rainbow trout (Oncorhynchus mykiss) to fire retardants weathered for 7-56 days on different substrates (duff, gravel, high organic content soil, and low organic content soil) under static conditions for 96 hrs to evaluate the potential toxicity of two current-use long-term fire retardant (LC95A-R and MVP-Fx) products. Trout mortality was greater in LC95A-R treatments compared to MVP-Fx due to higher concentrations of LC95A-R in the applied product than MVP-Fx at the same application rate. Underlying substrate affected fire retardant toxicity, with 31% higher average mortality for products applied to duff and gravel compared to soil. Differences in mortality across substrates and products after weathering may be attributed to differences in the mix-ratio of applied product and interactions of product chemistries with underlying substrate. These interactions resulted in elevated ionic concentrations of the overlying water in duff and gravel treatments. Trout mortality decreased 15% for products weathered 56 days compared to 7 days. Our results suggest that long-term fire retardants may persist in the environment and that underlying substrate may alter the toxicity of these products upon entrance into an intermittent stream.

As the likelihood of extreme weather and drought intensify with climate change, both the size and frequency of wildfires are expected to increase (Rind et al. 1990; Jones et al. 2020). In 2022, over 65 thousand wildfires burned more than 7.4 million acres in the United States, which is above the 10-year average (U.S. National Interagency Fire Center 2023). These wildfires occur across a variety of habitat types such as forests, grasslands, alpine regions, and encroach on urban areas. Each habitat type has a unique combination of vegetation and soil structure. As such, the tools used to combat and control wildfires need to be effective with different fuel types and substrates.

Long-term fire retardants are one tool used to combat and control wildfires. These retardants are used, in part, because they can be applied from the air when ground access is restricted (USFS 2011). Long-term fire retardants decrease the intensity and advancement of fire by creating a fuel break that alters the way fuels burn (USFS 2011; U.S. National Interagency Fire Center 2023). These fire retardants are most effective when applied at high concentrations and can continue to suppress fire even after water in the applied retardant has evaporated (Gould et al. 2000; Gimenez et al. 2004). In 2022, 43.9 million liters of fire-retardant solution was applied on U.S. Forest Service (USFS) lands to combat wildfire (USFS 2023). Given the volume applied annually, it is essential to understand the impacts retardants may have on the environment.

Intermittent streams constitute approximately 60% of the total length of rivers in the contiguous United States (Nadeau and Rains 2007). Periodically, these streams naturally cease to flow when evapotranspiration exceeds precipitation. Projected changes to temperature and precipitation patterns caused by climate change may have significant and variable effects to these seasonal streams across the United States (Larned et al. 2010; Dhungel et al. 2016). Intermittent streams are expected to increase in number and length as perennial rivers (i.e., those with continuous flow) shift to periodic flow regimes due to the potential increase in frequency and duration of drought conditions (Döll and Schmied 2012). Increased incidence of wildfires, coupled with more intermittent streams, increases the likelihood that long-term fire retardants may be applied to dry streambeds.

Long-term retardants that have not been volatized by wildfire likely persist on the landscape for extended periods during drought conditions. The USFS observed from 2015 to 2018 that approximately 25% of long-term retardant applied by airtankers does not interact with wildfire (USDA Forest Service 2020). The remaining retardant is exposed to sunlight, wind, humidity, microbes, and other factors that alter the concentration and chemical properties of the retardant while on the ground. Consequently, as retardants weather on dry streambeds, the resulting toxicity to aquatic biota may be affected once the stream is inundated. For example, the cation exchange capacity (CEC), or ability of soils to bind positively charged ions, can affect the bioavailability of ammonium (NH₄⁺) or other toxic components to organisms (Nommik and Vahtras 1982; Nieder et al. 2011). Organic matter and clay content are the primary factors that impact the CEC to bind and exchange ammonium (Kissel et al. 2008). Little and Calfee (2002) reported the toxicity of previously used fire retardants to aquatic organisms was significantly higher on soils with low organic content compared to soils with high organic content after 21 days of weathering, likely due to differences in CEC.

To simulate exposure to fire retardants in an intermittent stream environment following inundation with water, we applied two current-use long-term fire retardants, LC95A-R and MVP-Fx, to four substrate types (duff, gravel, high organic content soil, and low organic content soil). We assessed the toxicity of these fire retardants on juvenile rainbow trout (Oncorhynchus mykiss), a native, economically important fish species, after weathering on dry substrates for 7 to 56 days. The objectives of this study were to determine if the toxicity of fire-retardants to rainbow trout was impacted by 1) the product applied, 2) the underlying substrate, or 3) the duration of weathering prior to inundation with water. We hypothesized that the toxicity would decrease as weathering period increased and in treatments of substrates with higher CEC.

Test Fish

Erwin/Arlee strain rainbow trout were obtained from the U.S. Fish and Wildlife Service, Ennis National Fish Hatchery (Ennis, Montana) as eyed eggs. Eggs were hatched in culture and raised until 30–60 days post swim-up and acclimated to ASTM soft water (~ 40 mg/L as CaCO₃ using D1126-17 methods; ASTM International 2014) three days prior to the start of each assay at 12°C ± 1.5°C.

Test Products

Two long-term ammonium-based fire retardants (Phos-Chek LC95A-R and Phos-Chek MVP-Fx; Perimeter Solutions, Clayton, Missouri), which are both on the USFS Qualified Products List in 2024 in 2024, were tested (USDA Forest Service 2024). LC95A-R is a liquid concentrate formulation composed of ammonium polyphosphate, a gum thickening agent, and iron oxide as a coloring agent (Perimeter Solutions 2019). MVP-Fx is a powder concentrate formulation composed of a combination of monoammonium phosphate and diammonium phosphate, a gum thickening agent, and iron oxide as a coloring agent (Perimeter Solutions 2018). The concentrates are mixed with water according to manufacture specifications, resulting in solutions that are between 11 and 22% product prior to application on the landscape. The formulations of these fire retardants vary, and some information is proprietary; therefore, total ammonia nitrogen (TAN, un-ionized ammonia [NH₃] plus ammonium [NH₄⁺]) concentration and specific conductance were used to explore effects on biota between products.

Substrate Collection

Four substrates were selected for the study: duff, gravel, high organic content soil (HOC), and low organic content soil (LOC). The HOC was collected from a hardwood forest (University of Missouri Baskett Wildlife Research and Education Center, Ashland, Missouri) by removing any deciduous leaf litter and using shovels to collect the top 10 cm of soil. The LOC was a 1:1 ratio by volume mixture of the HOC and sand (HTH Pool Filter Sand; Innovative Water Care, Amboise, France). The tested soils were chosen because the percentage of organic matter content may affect the toxicity of these fire retardants, and wildfire impacts a variety of different soil types across the United States. The duff was a mixture of decomposing woody material (litter) collected near Missoula, Montana in a coniferous pine-fir forest. The gravel substrate was a mixture of river rock with an average diameter of 3.8 cm. The soils (HOC and LOC) were analyzed for total fertility (pH, neutralizable acidity, organic matter, available phosphorous, calcium, magnesium, and potassium), particle size (percent sand, silt, and clay), base saturation, and CEC at the University of Missouri’s Soil and Plant Testing Lab in Columbia, Missouri prior to the start of the assays (Table 1). Soil characteristics were measured and assessed using standard protocols outlined in Nathan et al. (2012). Duff samples were analyzed for pH and percentage of moisture by the same laboratory.

Table 1

Characteristics of underlying duff and soil substrates (HOC = high organic content soil, LOC = low organic content soil) used for testing the environmental persistence of two current use long-term fire retardants (LC95A-R and MVP-Fx). Shown are average values with standard deviation in parentheses (n = 3 samples per substrate type). NM indicates not measured. Gravel was not tested for nutrients in this study.
Substrate Characteristics	Substrate
Substrate Characteristics	Duff	HOC	LOC
pH	5.3 (0.1)	5.9 (0.1)	6.2 (0.1)
Neutralizable Acidity (mEq/100 g) ^a	NM	2.3 (0.3)	0.5 (0.0)
Organic Matter (%)	NM	6.8 (0.5)	1.5 (0.1)
Bray-1 P (mg/kg) ^b	NM	14.8 (1.0)	11.3 (0.6)
Ca (mEq/100 g) ^a	NM	9.2 (0.4)	4.4 (0.2)
Mg (mEq/100 g) ^a	NM	2.3 (0.1)	1.0 (0.1)
K (mEq/100 g) ^a	NM	0.4 (0.0)	0.2 (0.0)
Moisture (%)	22.8 (1.4)	NM	NM
Sand (%)	NM	25.0 (0.0)	74.2 (1.4)
Silt (%)	NM	62.5 (0.0)	19.2 (2.9)
Clay (%)	NM	12.5 (0.0)	6.7 (1.4)
Textural Classification	NM	Silty loam	Sandy loam
CEC (mEq/100 g) ^a,c	NM	28.1 (0.8)	6.3 (1.1)

^a mEq/100 g = milliequivalents per 100 grams

^b Available phosphate

^c Cation exchange capacity (ammonium acetate distillation method)

Experimental Design

To simulate environmental weathering of long-term retardants, we applied either LC95A-R, MVP-Fx, or control water (ASTM soft water) to substrate treatments and weathered them outside for 7 to 56 days. We used 4 replicates per treatment [4 replicates x 3 test waters (2 products and control) x 4 substrates x 4 weathering periods (7, 14, 28, and 56 days)] resulting in 192 total containers (i.e., experimental units). Each container (5-gallon [18.9-liter] polyethylene bucket) received 1 L of substrate, which amounted to a depth of approximately 3 cm. Product or control water was then applied to the surface of the substrate using a backpack sprayer to produce an even application of approximately 210 mL (200.1 mL [± 4.33 mL]) to achieve an application rate of 8 gallons/100 square feet (3.3 L/m²), which is the highest application rate the USFS uses (USFS 2011). Containers were covered nightly and during inclement weather to prevent debris from entering and further dilution of product by rain.

Upon the completion of a weathering period (7, 14, 28, and 56 days), sets of containers (48 buckets per weathering period) were transferred inside the U.S. Geological Survey, Columbia Environmental Research Center (CERC, Columbia, Missouri) where a 96-hr toxicity assay was conducted. Each container received 10 L of ASTM soft water resulting in nominal concentration of 5360 mg/L LC95A-R and 2300 mg/L of MVP-Fx. Containers were aerated and held in a water bath to maintain a temperature of 12°C ± 1°C during the assay. After substrate settled for 1 hr, 10 juvenile rainbow trout (30–60 days post swim-up) were added. For some treatments (i.e., duff), substrate was still suspended in the water column, hindering daily visual observations. If visible, fish that were dead, immobile with no visible opercular movement, were removed daily. All surviving fish at the conclusion of the 96-hr assay were enumerated and euthanized with an excess dose of buffered tricaine methanesulfonate (MS-222).

Water Chemistry Measurements

We monitored water chemistry at the start of each assay, as fish were exposed to the highest chemical concentration during this period. Temperature, dissolved oxygen, specific conductance, pH, alkalinity, total hardness, and TAN were measured following established protocols (APHA 2023). Temperature and dissolved oxygen were measured using a YSI Pro20 dissolved oxygen meter (Xlyem Inc., Washington, D.C.). Specific conductance was measured using a portable Orion Star A325 multiparameter meter (Thermo Fisher Scientific, Waltham, Massachusetts). An HQD HQ440d benchtop meter (HACH Company; Loveland, Colorado) equipped with IntelliCAL electrodes was used to measure pH (PHC301), alkalinity (PHC301), and TAN (ISENH3181). Total hardness was measured using the EDTA (Ethylenediaminetetraacetic acid) titration method. Composite samples of all replicates per treatment were collected for pH, alkalinity, and total hardness. Temperature, dissolved oxygen, and specific conductance measurements were collected from one randomly chosen replicate. The TAN measurements were collected from a composite of replicate samples from the first weathering period treatment and each replicate per weathering period treatment thereafter. A duplicated sample was also collected for one random treatment each sampling event. Given that the relationship between TAN and un-ionized ammonia (NH₃) is controlled by temperature and pH, proportions of un-ionized ammonia from the TAN concentrations were calculated using the following equation (Emerson et al. 1975; Guan et al. 2010):

$$\:{NH}_{3}=\frac{{NH}_{3}+{NH}_{4}^{+}}{1+{10}^{\left(pKa-pH\right)}}\:,$$

where pK_a is a calculated (pK_a = 0.09018 + 2729.92/T; T = temperature in Kelvin) ammonia-TAN equilibrium constant value. When comparing our measured TAN concentrations in the overlying water to the acute water quality criteria set by the U.S. Environmental Protection Agency (U.S. EPA), we normalized those concentrations to a pH of 7 using the following equation (US EPA 2013):

$$\:A{V}_{t,7}=\frac{A{V}_{t}}{(\frac{0.0114}{1+{10}^{7.204-pH}}+\frac{1.6181}{1+{10}^{pH-7.204}})},$$

where $\:{AV}_{t}$ is the TAN concentration. All instruments were calibrated prior to sample measurement and certified standards were measured at the beginning and end of each sampling event to verify the accuracy of those measurements. If standards measured outside of certified ranges, the instrument was recalibrated.

Statistical Analysis

Total mortality of rainbow trout at the end of each assay was summarized. We tested for differences in mortality between products and among weathering periods and substrate types using generalized linear models (GLM) with a binomial distribution and a logit link. Mortality data were logit transformed to meet model assumptions of GLMs using the “glm” function in the “lme4” package (Bates et al. 2015). All fixed-effect variables were evaluated using Analysis of Deviance table (Type III tests) with the “Anova” function in the “car” package (Fox and Weisberg 2019). For all significant relationships, Tukey’s multiple comparison test was performed to identify differences among treatments. Analyses were conducted in the R statistical programming language (v 4.3.3; R Core Team 2022). Trout mortality and water chemistry data are available in Puglis et al. (2023).

Mortality

The effects of product (F_2,144 = 10.1, p < 0.001), substrate type (F_3,144 = 10.5, p < 0.001), and weathering period (F_3,144 = 6.76, p < 0.001) were significant factors in the model (R² = 0.85). There was a significant interaction among product and substrate type and weathering period (F_18,144 = 2.15, p = 0.007), between product and substrate type (F_6,144 = 4.13, p < 0.001; Fig. 1), between substrate type and weathering period (F_9,144 = 3.26, p = 0.001), and between product and weathering period (F_6,144 = 2.81, p = 0.013). Mortality was highest in LC95A-R across all treatments compared to MVP-Fx or control, with near complete mortality on duff and gravel substrates. In general, mortality in MVP-Fx treatments was similar to controls, except in the gravel treatment, where mortality was greater in MVP-Fx. On average, duff and gravel substrates had 31% more mortality compared to the HOC and LOC soils. Also, there was a general trend of decreasing mortality as weathering period increased for each product, suggesting the toxicity of product decreased over time (Fig. 2). Average mortality ranged from 0–40% across control treatments, with the highest mortality observed in duff substrate after 7 days of weathering.

Water Chemistry

Water temperature (10.3–13.4°C) and dissolved oxygen (7.5–9.9 mg/L) were similar across all treatments. Alkalinity was higher in the products than in the control group, while pH was lower in the products (Table S1). We only assessed total hardness for control group water samples (38–87 mg/L) as the products interfered with the water hardness method we used to measure hardness. Specific conductance was higher in the products (LC95A-R = 464–2125 µS/cm, MVP-Fx = 398–1859 µS/cm) compared to the control group (166–197 µS/cm). There were differences in specific conductance across substrates, with 696–2125 µS/cm in duff and gravel treatments and 398–654 µS/cm in the soils between both products. The TAN concentrations were 38.6–398 mg of N/L in LC95A-R and 30.3–524 mg of N/L in MVP-Fx across all treatments. The average TAN concentration in the control group was 0.43 ± 0.29 mg of N/L. There was a decrease of 20–47% in TAN concentrations from day 7 to both 14 and 28 days of weathering and an increase of 56% after 56 days of weathering. The TAN concentrations were highest in duff and gravel substrates (0.08–586 mg of N/L) across all treatments compared with the soils (0.20–95.4 mg of N/L). The products corroded the probe membrane, which caused 50% of the ammonia standards to fall outside of the acceptable range.

In this study, the toxicity of long-term wildland fire retardants to rainbow trout was altered by other environmental variables such as the underlying substrate the product was applied to and the length of time product weathered on dry substrate before inundation with water. In previous work, we found that some environmental variables, such as water temperature, alter the toxicity and subsequent impacts of fire retardant to fish (Puglis et al. 2022). We also confirmed differences in toxicity between products as described in Puglis et al. (2022). Lastly, the significant interaction observed between product and substrate highlights the need to consider underlying substrate when evaluating the toxic effects of weathered fire retardant in intermittent streams.

Influence of Product

Toxicity differed between products, as LC95A-R was always more toxic than MVP-Fx, regardless of substrate (Fig. 1). This is consistent with previous studies in larval fish, which attributed the difference in toxicity to higher un-ionized ammonia concentrations in LC95A-R than MVP-Fx at the same application rate of retardant (Puglis et al. 2022; Puglis and Iacchetta 2023). In aqueous solution, TAN is present as a ratio of un-ionized ammonia and ammonium (NH₃:NH₄⁺). Temperature and pH affect this ratio such that increases in temperature and pH increase the concentration of un-ionized ammonia (Emerson et al. 1975); therefore, different environments can have varying ratios of un-ionized ammonia to ammonium. Un-ionized ammonia is relatively more toxic to fish than ammonium due to its neutral charge, which allows for greater uptake through membranes, including the gill epithelium (Evans et al. 1989). Exposure to elevated concentrations of un-ionized ammonia can cause convulsions, comas, and eventually lead to death in fish (Randall and Tsui 2002). Buhl and Hamilton (2000) reported a 24-hr LC₅₀ of un-ionized ammonia as 0.125 mg of N/L for 40 days post swim-up rainbow trout larvae. Un-ionized ammonia concentrations in this study were below this threshold (except for one replicate of LC95A-R weathered on duff substrate after 7 days; NH₃ = 0.139 mg of N/L) and were lower than our previously reported values for similar concentrations of fire-retardant in water-only exposures (Puglis et al. 2023). This suggests the ammonium, or some other unmeasured component of the products, contributed to the mortality observed across substrates in the current study. The acute water quality criteria for TAN, a concentration set by the U.S. EPA (US EPA 2013) to protect aquatic life, is 24.1 mg TAN/L at pH 7 and temperatures below 14°C (US EPA 2013). All TAN observed in product treatments within this study (n = 160) were above the criterion, except for five replicates in the soil treatments of MVP-Fx and one replicate of LC95A-R in LOC at 14 days of weathering and all control treatments (Fig. 3).

Influence of Substrate on Product Toxicity

For both fire-retardants tested, we observed higher mortality in duff and gravel treatments compared to soil treatments for a given product (Fig. 1). Visual inspection of the data indicates that while the un-ionized ammonia concentrations appeared comparable across all substrates (Fig. 4a), specific conductance varied, with duff treatments showing relatively high values followed by gravel, HOC, and LOC (Fig. 4b). Specific conductance is an indirect measure of dissolved ions in a solution, including ammonium. Thus, the specific conductance of the overlying water in our treatments was influenced by substrate and is not independent of the TAN concentrations, but also includes other ions, which may contribute to toxicity. Our data suggest that, within a product, the composition of residual ions in the overlying water of duff and gravel are more toxic than in the overlying water of both soil treatments.

One mechanism that influences ion availability is CEC, a measure of a soil’s ability to adsorb and retain cations controlled by the negatively charged sites within a soil (Nommik and Vahtras 1982; Sumner and Miller 1996). Ammonium is a positively charged ion and thus able to bind to negatively charged sites in soils, making it mostly unavailable for cation exchange reactions (Nieder et al. 2011). Clay and organic matter content of soil are the primary constituents that influence the CEC to fix added ammonium (Nommik and Vahtras 1982; Kissel et al. 2008). Generally, higher clay and/or organic matter content equates to greater CEC (Wright and Foss 1972; Martel et al. 1978). While not measured, the CEC was likely lowest in the gravel treatments and may have resulted in the product remaining suspended throughout the water column, increasing potential exposure to the trout. This may account for the high mortality observed in gravel treatments compared to soil treatments. We would have predicted that the TAN concentration and mortality would be lower in the HOC soil than the LOC soil treatments, given the CEC of the HOC soil was more than four times that of the LOC soil. Yet, we observed similar mortality and measured similar TAN concentrations between the soil treatments within a product. This suggests the concentration of TAN from the product saturated the negatively charged sites in both soils and exceeded the ability of the CEC to measurably affect the TAN concentration in the overlying water.

Although not measured here, duff presumably had a higher CEC compared to the soil and gravel treatments. The CEC of duff collected from a coniferous-deciduous forest in Oregon was more than 50 mEq/100 g (Warner 1976), which is higher than our soil treatments (HOC = 28.1 mEq/100 g, LOC = 6.3 mEq/100 g; Table 1). Yet, the highest mortality was observed in duff treatments, and as previously stated, un-ionized ammonia concentrations did not vary substantially across substrates within a product. It is possible that the duff was not composed of enough decomposing material to elevate the substrate’s CEC, and thus there was a low binding affinity of ammonium. Additionally, trout may have experienced added stress from suspended duff material in the water column. The effect of suspended solids on Salmonids in controlled environments is associated with death, gill trauma, decreased osmoregulatory ability, and increased blood sugar levels (Redding et al. 1987; Muck 2010). Therefore, potentially lower than expected CEC and additional stress from substrate suspension in the duff treatment may explain the observed mortality.

Influence of Environmental Weathering

There was a trend of decreasing mortality as weathering period increased (Fig. 2). Mortality observed in rainbow trout exposed to product weathered for 56 days was 15% lower than the observed mortality in those exposed to product weathered for 7 days. Physical and microbial processes such as ammonia volatilization, ammonia nitrification (Aislabie and Deslippe 2013), or ammonium fixation could have influenced the bioavailability of TAN to fish. As a result, these products on the landscape may become less toxic over time but likely persist in the environment after 56 days.

Our results suggest that LC95A-R and MVP-Fx may persist in the environment after weathering for 56 days and that the underlying substrate may alter the toxicity of these products under static conditions. Although these data provide a better understanding of the environmental persistence of long-term fire retardants, aquatic organisms are likely to encounter effects from climate change, wildfires, and intrusion of fire retardant in an intermittent stream. The consequences of climate change could have direct and indirect impacts to organisms that utilize these highly productive, dynamic streams for spawning, refuge, and foraging (Mas-Martí et al. 2010; Vander Vorste et al. 2020). Ash inputs (Earl and Blinn 2003; Murphy et al. 2018), sedimentation (Rhoades et al. 2011), and increased temperatures (Dunham et al. 2007) can occur in these streams following wildfire. Additionally, organisms can experience additional stressors from exposure of long-term retardants, either through direct contact into the waterbody or via runoff from precipitation events after application. The combination of these effects may create a cumulative toxic effect to aquatic organisms. This study provides resource managers with key data characterizing potential toxicity to aquatic life in situations where fire retardant is applied to dry intermittent streambeds.

DISCLAIMER: Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Acknowledgement: This work was supported by the U.S. Forest Service (USFS) with additional funding through the U.S. Geological Survey (USGS) Contaminant Biology Program and USGS Toxic Substances Hydrology Program. We’d like to thank J. Orech, E. Scott, S. Tidwell, and T. Tidwell for assistance in data collection.

Funding: The work was supported using the funds provided by the USFS, U.S. Geological Survey (USGS) Contaminant Biology Program, and USGS Toxic Substances Hydrology Program.

Conflict of Interest: The authors declare that there is no financial or non-financial interest to disclose.

Author Contributions: All authors commented and edited revisions to the manuscript. Holly Puglis conceptualized and designed the study. Material preparation, experimentation, investigation, and data collection were performed by Christina Mackey and Holly Puglis. Data analysis was performed by Christina Mackey and Michael Iacchetta. The first draft of the manuscript was written by Christina Mackey. All authors read and approved the final manuscript.

Ethical Approval: The present study was reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) at the US Geological Survey – Columbia Environmental Research Center under IACUC19-007.

Data Availability Statement: The datasets generated during and/or analyzed during the current study are available in the ScienceBase repository, https://doi.org/10.5066/P9C94L2L.

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Environmental Persistence and Toxicity of Weathered Wildland Fire Retardants to Rainbow Trout

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Abstract

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Introduction

Materials and Methods

Test Fish

Test Products

Substrate Collection

Experimental Design

Water Chemistry Measurements

Statistical Analysis

Results

Mortality

Water Chemistry

Discussion

Influence of Product

Influence of Substrate on Product Toxicity

Influence of Environmental Weathering

Conclusions

Declarations

References

Supplementary Files

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