Adequacy and uncertainty in models and scenarios developed to estimate pesticide wash-off and runoff in residential settings
A variety of pesticide products, including Insecticides, herbicides, and fungicides, are used by homeowners and licensed Pest Control Operatiors to eradicate or deter pests on lawns and ornamentals, vegetable gardens, homes, and other structures. Pesticide detections in urban streams have resulted in an increase in research over the past decade to understand the potential for pesticide washoff to occur from various pervious and impervious application sites. Regulatory agencies, chemical registrants, and other researchers have employed a variety of approaches to model pesticide runoff associated with residential uses. This presentation compares the underlying prinicipals in several models and scenarios that have been adopted or proposed for pesticide registration review and risk assessment by regulatory agencies in the U.S. and the E.U.; and evaluates their appropriateness for risk assessment for various categories of outdoor residential-use pesticide products. The models/scenarios include the Home and Garden scenario developed for the HardSPEC model by the Food and Environment Research Agency in the U.K., residential scenarios developed for PRZM5 by the U.S. Environmental Protection Agency, and adapting urban stormwater management models including the Stormwater Management Model (SWMM5) and the P8 Urban Catchment Model.
Marty Williams (Waterborne Environmental), Yuzhou Luo (CDPR), and Michael Winchell (Stone Environmental). Adequacy and uncertainty in models and scenarios developed to estimate pesticide wash-off and runoff in residential settings. Platform SETAC 2018. Sacramento, CA.
Setting a species-specific population model in the context of an aquatic food web model: A case example for the Topeka shiner
For species listed as threatened or endangered under the Endangered Species Act (ESA), higher-tier environmental risk assessments (ERAs) include assessing potential overlap of pesticide use patterns and the species’ geographical range. However, potential risks to populations also depend on temporal aspects of exposure and effects as well as interactions with ecosystem-mediated effects. We developed an individual-based population model (IBM) for the Topeka shiner (Notropis topeka), a fish species listed as endangered, and linked it with an aquatic food web model (comprehensive aquatic systems model, CASM). The CASM was parameterized and calibrated to represent the waterbody conditions and aquatic species community in a small headwater pool in Iowa, representative of a Topeka shiner’s key habitat within its geographical range. In the IBM, Topeka shiners feed on several groups in the aquatic food web according to published diet studies. Fish are simulated to grow according to a bioenergetics submodel that considers consumption, respiration and waste losses. We modelled the effects of alterations of the food web on the Topeka shiner populations by systematically reducing the available biomass of groups that the shiners consume. These alterations are generic simulations of the potential effects of pesticide exposures in agricultural landscapes around the shiner’s habitat. Potential pesticide effects on the food web depend on the compound, magnitude, timing and duration of exposure, and are simulated in the model by applying daily concentrations of a pesticide in the simulated waterbody which can be derived from field measurements or fate models. The linked models provide a platform for the assessment of potential direct and food-web mediated indirect effects of stressors such as pesticides on species populations.
Amelie Schmolke (Waterborne Environmental), Steven Bartell (Cardno), Colleen Roy (Waterborne Environmental), Nicholas Green (Waterborne Environmental), Daniel Perkins (Waterborne Environmental), Nika Galic (Syngenta), Richard Brain (Syngenta). Setting a species-specific population model in the context of an aquatic food web model: A case example for the Topeka shiner. Platform SETAC 2018. Sacramento, CA.
Taxa-focused approach to standardizing use of population models in ecological risk assessment
In spite of widespread acceptance of the utility of population modeling and advocacy of these approaches for more ecologically relevant perspective, they are not routinely incorporated in ecological risk assessments (ERA). A systematic framework for situation-specific model development is one of the major challenges to broadly adopting population models in ERA. As risk assessors confront the multitude of species and chemicals requiring evaluation, adaptable model templates and taxa-specific guidance on model parameterization would facilitate this process. We build on previous work that created a framework and decision guide for developing population models for ERA by focusing on anuran amphibians. Anurans have a unique life cycle with varying habitat requirements and physiological processes. These species belong to the amphibian class, which is facing global population declines, due in large part to anthropogenic stressors, including pesticide effects. A stage-based matrix model broadly represents the anuran life cycle. We synthesize information from databases and literature relevant to amphibian risks. At the individual, population, and ecological levels we identify traits that influence inherent sensitivity, population vulnerability, and environmental constraints. We also outline methods of modifying a basic population model to suit specific risk assessment needs with appropriate scale and parameterization to evaluate pesticide effects. A standardized population model approach for anuran ERA offers an example method of identifying potential risks and determining long-term impacts of chemical stressors to populations across taxonomic groups.
Jill Awkerman (USEPA), Sandy Raimondo (USEPA), Amelie Schmolke (Waterborne Environmental), Katherine Kapo (Waterborne Environmental), Nika Galic (Syngenta), and Valery Forbes (University of Minnesota). Taxa-focused approach to standardizing use of population models in ecological risk assessment. Platform SETAC 2018. Sacramento, CA.
Watershed modeling: Comparison of process-based model PRZM/SWAT with regression-based model SEAWAVE-QEX
Water quality monitoring data, specifically for pesticides, can represent best-available exposure profiles relevant to ecological risk assessment; however, there are challenges in synthesizing these data toward making conclusions about the nature of the potential range of risk. Some of these challenges include: data collection frequency, monitoring period duration, interpreting exposure profiles from one location to another, and monitoring system scale. To address these challenges, statistical approaches may be applied to characterize empirical trends. Additionally, process-based numerical modeling approaches can offer a different perspective on synthesis and interpretation of monitoring data. A comparison of a statistical and process-based numerical model was conducted to evaluate strengths and weaknesses of representing, synthesizing, and conclusions from monitoring data. This comparison was developed from pesticide measurements of six intensively-monitored HUC12 headwater watersheds in the Midwest. SEAWAVE-QEX is a regression model that incorporates a linear trend term, covariates accounting for seasonality, and a transformation of flow to represent a long-term pesticide trend at a specific monitoring location. PRZM/SWAT (Pesticide Root Zone Model/Soil Water Assessment Tool) is a spatially-distributed hydrologic and chemical transport numerical model that combines upland chemical and hydrologic processes from PRZM and stream flow and chemical transport processes from SWAT. The predictive quality and limitations of these two models (SEAWAVE-QEX and PRZM/SWAT) was assessed against observed, daily concentration measurements as well as hypothetical data collection frequency and timing (derived from sub-sampling the same data sets).
Wenlin Chen (Syngenta), Daniel Perkins (Waterborne Environmental), Andrew Jacobson (Waterborne Environmental), Colleen Roy (Waterborne Environmental), and Farah Abi-Akar (Waterborne Environmental). Watershed modeling: Comparison of process-based model PRZM/SWAT with regression-based model SEAWAVE-QEX. Platform SETAC 2018. Sacramento, CA.
Spatial and temporal variations of national cropping patterns for higher-tier pesticide exposure assessment
Pesticides are used on numerous agricultural crops across the United States to control pests and improve food yield and quality. This presentation focuses on the spatial and temporal aspects of a national scale assessment conducted by the Pyrethroid Working Group (PWG) to characterize the potential for pyrethroids to enter flowing surface waters based on a spatially explicit analysis of crop proximity to surface waters using multi-year data on diverse agricultural production patterns. Standard exposure calculations in the USEPA EFED regulatory risk assessment framework assume that 100% of the area around the water body (the Tier II pond) is cropped and treated, and therefore subject to drift and runoff entry. Over two million catchments within the National Hydrography Dataset (NHDPlus) were characterized using geospatial data to develop national or regional metrics related to potential surface water exposure related to crop proximity for more than 10 crop types. Crop locations were based on five years of data from USDA NASS Cropland Data Layer. Results highlight the variability of cropping density at the catchment scale across different geographies and scales, as well as situations in which density of potentially highly exposing crop (e.g., within 200m of surface water) may not match ‘entire catchment’ cropping density patterns. Variations in cropping density (as a proxy for potential exposure) across multiple years will be discussed in relation to how this variability may influence exposure estimates. When examining all catchments containing a specific crop, the 90th percentile crop density values (based on the 200m proximity zone) ranged from 1.3% (for vegetables in FL) to 44.4% (for tree nuts in CA). The resulting datasets provide a useful set of metrics across multiple crops which can be applied to pesticide exposure assessments that may need spatially-explicit refinements related to crop-water interactions. Because the crop proximity results are linked to the NHD+ framework, including these specific attributes into other NHD+-based analyses is extremely efficient.
Christopher Holmes, Joshua Amos (Waterborne Environmental), Paul Hendley (Phasera, Ltd.), Russell Jones (Bayer CropScience), Scott Jackson (Valent). Spatial and temporal variations of national cropping patterns for higher-tier pesticide exposure assessment. Poster SETAC 2018. Sacramento, CA.
A generalized life-history model for assessing indirect effects of pesticides on fish populations
Assessing population-level effects of stressors, such as pesticides, across species is challenging because effects are influenced not only by individual-level toxicity but also by species’ life history characteristics, ecology, and the duration, magnitude, and frequency of stressor exposure. Additionally, potential indirect population-level effects of stressor exposure (for example, effects resulting from changes in food availability) add further complexity to the assessment. To address these challenges, we developed a generalized population model for small fishes for assessing potential indirect effects of pesticide exposure on population dynamics. We applied the model to 17 species of darter (Percidae: Etheostomatinae) for which life history and diet data were readily available. The selected darter species (including two species listed under the Endangered Species Act) cover a range of life history strategies and diet compositions within the subfamily. We simulated several scenarios of pesticide exposure to assess how potential impacts of a pesticide on various prey species (invertebrates) included in the diets of selected darter species might affect darter population dynamics over extended time periods. We also investigated correlations between life history characteristics and population responses to the exposure scenarios. This analysis provides a framework for predicting food web mediated effects of pesticides on darter species for which little life history information is available. By combining life history variability in fish with estimates of potential indirect effects of pesticides on their prey, our model can provide a valuable tool for incorporating ecological complexity into the assessment process to quantify population-relevant risks to listed and non-target species of small fish.
Nicholas Green, Amelie Schmolke, Brian Kearns, Colleen Roy, Katherine Kapo, Matthew Kern (Waterborne Environmental), Alan Samel (FMC), Valery Forbes (University of Minnesota). A generalized life-history model for assessing indirect effects of pesticides on fish populations. Poster SETAC 2018. Sacramento, CA.
Model the effectiveness of vegetated filter strips in reducing contaminants in feedlot runoff
The National Pollutant Discharge Elimination System (NPDES) regulations require concentrated animal feeding operations (CAFO) with greater than 1000 head beef cattle to contain feedlot runoff in settling basins designed to hold runoff from a 25-year 24-hour rainfall. CAFO with less than 1000 head may discharge feedlot runoff to nearby waters under NDPES permits if there are certain best management practices (BMPs) in place like settling basins or vegetated filter strips. Runoff from feedlots may contain nutrients or veterinary pharmaceutical residues excreted in animal waste, which under some circumstances could be potentially harmful to aquatic organisms if released directly to nearby surface waters. The objective of this presentation is to model the effectiveness of vegetated filter strips (VFS) in reducing contaminants in feedlot runoff using the WINPRZM and VFSMOD models. Effectiveness of VFS in reducing nutrient concentrations in feedlot runoff will be presented as a case study. WINPRZM was enhanced to simulate runoff from an earthen or concrete uncovered beef feedlot. The model predicts the daily edge-of-field mass of nutrients and other constituents in runoff generated on a feedlot due to precipitation. The feedlot algorithm can model daily manure accumulation, various chemical administration patterns, and the periodic scraping of feedlots. The model uses the SCS curve number method to estimate runoff, a non-uniform mixing model to extract constituents from manure, and the manure erosion equation from the APEX model. The daily edge-of-field mass loadings estimated by WINPRZM are then input to the VFSMOD model which estimates the reduction of loadings based on the size of VFS and the resulting concentrations in runoff discharging from the VFS.
Ishadeep Khanijo, Marty Williams, Amy Ritter, Mark Cheplick (Waterborne Environmental), and Dawn Merritt (Zoetis). Model the effectiveness of vegetated filter strips in reducing contaminants in feedlot runoff. Platform SETAC 2018. Sacramento, CA.
Development of a spatially resolved global mean annual flow dataset for use in environmental risk assessment: A case study for China
Environmental exposure models for chemicals used widely across large geographic areas and disposed of down the drain are important tools for informing ecological risk assessments. One important element of these models is understanding the dilution of wastewater treatment plant (WWTP) effluent into the receiving stream (dilution factors) which allows for the estimation of in-stream environmental concentrations based on either estimated flow of receiving waters. In the U.S., the iSTREEM model (American Cleaning Institute) estimates dilution of WWTP effluent into receiving streams through the incorporation of a spatial hydrologic network with associated flow data (National Hydrography Dataset Plus) into the exposure model to spatially associate (and route) local WWTP emissions with corresponding local flows. A similar approach for generating localized dilution factors can be employed on the global scale to integrate the chemical emissions component of the model with a hydrologically-connected global river network with associated flow values. The HydroSHEDS and HydroBASINS datasets (Lehner et al. 2008 and 2013) provide a global hydrology dataset that can be used as a spatial hydrologic framework, including a network of streams and rivers and watershed and catchment boundaries. However, flow estimates corresponding to the global river network are a critical attribute that must still be incorporated for exposure modeling. Using China as a case study, a mean annual flow dataset to correspond with the HydroSHEDS and HydroBASINS global data was developed using the well-established Curve Number (CN) approach developed by Natural Resources Conservation Service (NRCS, USDA). The CN approach integrates environmental and landscape features including best available and high-resolution precipitation, soils, and land use characteristics to estimate surface runoff over the land area. The high-resolution runoff grid was spatially combined with hydrology datasets to derive flow estimates across a river network. Global datasets were utilized for model parameters so that the approach could be extrapolated to the global scale, while also providing the flexibility to incorporate best-available data. This presentation will provide a detailed overview of the runoff methodology, validation against measured flow data, and the resulting river flow dataset for China.
Raghu Vamshi, Katherine Kapo, Amy Ritter, Brian Kearns (Waterborne Environmental), and Kathleen McDonough (Procter & Gamble). Development of a spatially resolved global mean annual flow dataset for use in environmental risk assessment: A case study for China. Poster SETAC 2018. Sacramento, CA.
Development of a global environmental exposure modeling framework for risk assessment of chemicals disposed down the drain: A case study for China
Environmental exposure assessment of chemicals that are disposed down the drain (such as consumer product ingredients) at the global scale within a consistent and accessible framework has remained a challenge over the years, despite advancements in exposure modeling and global and local data resources. Historically, assessment efforts have been tailored and applied to specific geographies and used simplistic approaches rather than to build a spatially resolved global assessment infrastructure. Challenges such as inconsistent, scarce, or rapidly-evolving data resources, particularly for developing countries where assessment needs are high, have further complicated the evolution of spatially resolved global exposure assessment tools. However, through strategic integration of existing global data resources and established modeling tools, a standardized framework and methodology for GIS-based exposure modeling can be developed for the global scale. In this study, we present a spatially resolved global environmental exposure model approach designed to incorporate best-available data and modeling tools, using China as a case study. The global hydrology network from HydroSHEDS and HydroBASINS (Lehner et al. 2008 and 2013), global river flow and population estimates, and best-available country-specific water use and wastewater treatment information were integrated with the GIS-ROUT exposure model (Wang et al. 2005) and iSTREEM® model framework (American Cleaning Institute) to provide a means of estimating the distribution of concentrations of a chemical disposed down the drain across a river network based on chemical production volume and consumer usage estimates. Both wastewater treatment plant effluent and direct discharge are accounted for by the model through estimation of catchment-specific emissions. The spatial nature of the model provides a robust means for estimating variability in environmental exposures. Details of the various model components and generated output for China are overviewed, as well as considerations and discussion regarding on-going extrapolation to the global scale. The framework developed as part of this model is highly adaptable to countries with an abundance of data (e.g., North America, Western Europe, etc.) or those scarce with data (e.g., developing countries) available to parametrize the model.
Kathleen McDonough (Procter & Gamble), Katherine Kapo (Waterborne Environmental), and Raghu Vamshi (Waterborne Environmental). Development of a global environmental exposure modeling framework for risk assessment of chemicals disposed down the drain: A case study for China. Poster SETAC 2018. Sacramento, CA.
A new tool for the toolbox: Predicting multi-pathway emission and fate of contaminants entering freshwater systems in Europe
Exposure models help to prospectively assess the potential for ecological exposures from releases of substances into the environment. Availability of newer data, increasing computing power and improved methods provide continuing opportunity to improve our ability to predict environmental exposures through models and add to our “toolbox”. We present a new model designed to encompass multi-pathway environmental emissions coupled with environmental fate components, contained in a modular and transparent framework which is scalable and portable to multiple geographies. This spatially-explicit model (presented here for Europe) is based on publicly available datasets, combined with a hydrologic framework containing geographically variable emissions linked to a river network simulating environmental transport via surface water. The hydrologic framework is based on a set of basins and rivers (WWF HydroSHEDs) linked to emission characteristics for each sub-basin (more than 37,000 in the EU-30). Emissions characteristics are derived from point-source wastewater data (EEA Waterbase) as well as diffuse source inputs, accounting for the potential of urban storm water runoff or other overland flow constituents. Concentrations of contaminants are routed through the river network based on local river attributes combined with assumptions about chemical fate in the aquatic environment. Multi-year, high-resolution data on river flow (FLO1K) are leveraged for an expanded set of possible modeling scenarios. Transparency is critical for model understanding and acceptance. Model documentation follows standard documentation protocol proposed by the European Committee for Standardization (CEN) as described in the 2016 CEN workshop: “Promoting the acceptance and use of chemical exposure models through transparent documentation”. Several scenarios will be presented covering different use/emission situations and substance fate characteristics, including the relative importance of different emission pathways (e.g., down-the-drain, urban storm water, land-based diffuse runoff) and environmental media. While the presented material is an example of environmental emission and fate of different substances, it represents a working framework implemented for Europe with viable application to other geographies.
Christopher Holmes, Joshua Amos, Amy Ritter, and Marty Williams (Waterborne Environmental). A new tool for the toolbox: Predicting multi-pathway emission and fate of contaminants entering freshwater systems in Europe. Poster SETAC 2018. Sacramento, CA.