Join Waterborne at this year's ACS Fall 2025, held in Washington, D.C. August 17th-21st. Our scientists will be presenting in the following panels:

Monday August 18, 2025

Session - Refined Risk Assessment and Implementation of Pesticide Mitigation Practices for Species Protection:

8:00 AM - 11:35 AM EDT, Room: Hall E - Room 14 (Walter E. Washington Convention Center)

Amy Ritter, Waterborne Environmental, is one of the organizers/presiders of the session

Presentations in this session with Waterborne as authors/co-authors:

8:05 AM - 8:30 AM EDT - Evaluating EPA’s Tier-3 scenarios for refining pesticide exposure and mitigation needs under ESA

Presenter: Lula Ghebremichael

Co-Authors: Michael Winchell, Nathan Snyder, Frank Donaldson, Gerco Hoogeweg

Overview: This study evaluates EPA’s Pesticide in Water Calculator (PWC) Tier-3 scenarios as a potential science-based approach for refining pesticide exposure estimates and mitigation needs for ESA compliance. By examining test-case pesticides with varying properties and crop uses, a team from the Crop Life America (CLA’s) Exposure Working Group assess how Tier-3 refinements account for key factors such as soil, slope, and weather conditions that influence predicted environmental exposure concentrations (EECs) in terrestrial and aquatic habitats. The analysis also explores the broader applicability of Tier-3 refinements across multiple compounds and their alignment with the current regulatory framework. Findings from this study will be shared at the conference.

11:05 AM - 11:30 AM EDT - Development of a mitigation support tool to assist growers with ESA compliance

Presenter: Andy Jacobson

Co-Authors: Zechariah Stone, Nick Guth, Mark White, Richard Brain

Overview: When the United States (U.S.) Environmental Protection Agency (EPA or the Agency) determines through risk assessments that a pesticide is likely to adversely affect listed species or their designated critical habitats, the Agency may require registrants to implement erosion/runoff mitigation measures (e.g., conservation tillage, grassed waterways, etc.) on their registration and product labeling to ensure compliance with the Endangered Species Act (ESA). The EPA has adopted a mitigation point system as part of their Herbicide and Insecticide Strategies to convey the level of mitigation required for a pesticide to address identified ecological risks. As a result, growers will need to plan their pesticide applications in advance to determine whether they are subject to mitigation. Unfortunately, growers are currently required to follow a convoluted framework to determine which runoff/erosion mitigation measures to consider and employ before using a pesticide for their operation each year. To complete this process, growers will need to know soil and landscape information about their farm/field(s), including soil type and slope, and must choose which mitigation measures to employ from a list of over 40 options.

To provide technical assistance to growers and their support networks, a user-friendly web application was developed to help growers navigate the EPA’s pesticide mitigation point system. This web application utilizes a grower’s location and field-specific information to identify the mitigation points required based on pesticide labels and the EPA’s mitigation website. To determine mitigation, point requirements and make suitable mitigation recommendations to growers, the developed web application includes spatial data and user input on existing, already implemented mitigation practices which will allow for mitigation point credits. If the web application determines that additional mitigation points are required for a field/farm, then it will provide a ranked list of mitigation practices to meet the remaining need. This mitigation support tool will be presented, and a case study will demonstrate its application.

Tuesday, August 19

Water Monitoring Study Design and Interpretation for Agrochemical Exposure Assessment:

8:50 AM - 12:00 PM EDT, Room: Hall E - Room 13 (Walter E. Washington Convention Center)

Amy Ritter, Waterborne Environmental, is one of the organizers/presiders of the session

Presentations in this session with Waterborne as authors/co-authors:

8:55 AM - 9:20 AM EDT- Real-time nitrate monitoring in tile-drained fields in Central Illinois

Presenter: Russell Krueger

Overview: Shawn Meyer, Paul Glaum, Jennifer Trask, Laura Gentry, Dan Schaefer, Lowell Gentry

Abstract: Midwestern states continue to engage various agricultural practices to advance nutrient water management initiatives to support state nutrient reduction strategies for the Mississippi River basin. While numerous studies have demonstrated that specifically targeted nitrogen fertilizer application rates and cover crop use successfully address water quality concerns, many farmers remain unconvinced of the benefits. Fewer than 30% of Illinois corn fields have nitrogen applied within the Maximum Return to Nitrogen (MRTN) range based on recent state surveys and extension documents. Likewise, the inclusion of cover crops in farming practices has been slow to develop despite continued research supporting the environmental benefits such as reduced nitrogen loss and improved soil health. Therefore, continued research to support these and other best management practices is imperative to increase farmer buy-in to support Illinois' continued contributions towards meeting their nutrient loss reduction strategy goals as well as the broader goals of the EPA's Gulf Hypoxia Task Force.

An ongoing research study has observed the effect of treatments on nitrate-nitrogen (N) concentrations in tile outlet water utilizing an innovative design for real-time water quality monitoring on two fields across thirty-seven discrete tile drains. This design uses an automated pass-through approach to measure nitrate-N in real-time as water flows through each individual tile system. This expansive tile drain network gives way to a replicated design which provides the ability to use statistics in a robust way to observe trends throughout the study. The treatments being examined are 1) nitrogen treatments at three different rates: the University of Illinois-recommended MRTN rate plus forty lbs above and below the MRTN, and 2) the presence or absence of cover crops. This presentation will highlight details of this unique design and review results obtained thus far.

10:40 AM - 11:05 AM EDT- Next generation of spatially distributed pesticide leaching models

Presenter: Cornelis Hoogeweg

Co-Authors: Aaldrik Tiktak, Amy Ritter, Anton Poot, Bernhard Jene, Dimitrios Skodras, Emilie Farama, Gerard Heuvelink, Gregor Spickermann, Gregory Hughes, Judith Klein, Louise Wipfler, Maarten Braakhekke, Michael Klein, Michael Stemmer, ​ Michelle Morris, Pavan Cornelissen, Robin Sur, Stephan Marahrens, Stephan Reichenberger, Nicoleta Suciu ​

Overview: Spatially distributed pesticide leaching models play an important role in pesticide registration in some European countries. At the European scale, however, their use is limited by the lack of an agreed methodology. EFSA’s Panel on Plant Protection Products and their Residues noted in its Statement on Groundwater Monitoring Studies that this is one of the main factors limiting the regulatory acceptance of groundwater monitoring studies. A SETAC working group has developed a harmonised framework for spatially distributed leaching models for use at the continental and regional scale in Europe. This framework can support groundwater exposure assessment at Tier 3b of the FOCUS tiered approach, identification of vulnerable sites within an area of interest for groundwater monitoring and support context setting of groundwater monitoring studies at Tier 4. The framework contains a standardized database to support both the spatially distributed leaching modelling (SDLM) versions of PEARL and PELMO leaching models. The underlying data will use state-of-the-art pan-European datasets, which are based on machine learning algorithms and remote senses data amended by field observations. The datasets are representative for arable soils. The framework will deliver maps of the leaching concentration at 1-m depth, which are considered a conservative estimate of the concentration in groundwater. This presentation will highlight results of the models and focusses on the approximation of a 90th-percentile (80th spatial combined with 80th temporal percentile) leaching concentration for FOCUS climatic zones. We will demonstrate the characteristics of vulnerable regions selected by the models and compare the effect of using different modelling approaches. We will discuss the consequences for the FOCUS tiered approach if this model framework would be accepted for regulatory use.

11:05 AM - 11:30 AM EDT - Machine learning approach to integrate aquatic modeling and monitoring data for exposure assessment

Presenter: Wenlin Chen

Co-Authors: Yaoxing Wu, Zechariah Stone, Amy Ritter

Overview: The substantial spatial and temporal variability of hydro/environmental conditions coupled with various agronomic practices and pesticide use patterns has led to significant challenges when determining the exposure distributions of the agrochemicals in the U.S. surface water. Since it is not feasible to directly sample for pesticide concentrations at every location and time, the EPA primarily relies on scenario-based theoretical models such as Pesticide in Water Calculator (PWC) for lower-tier assessment. Additionally, existing water monitoring data for pesticides were considered to support the higher-tier exposure refinement, which is largely independent of the lower-tier results. Supervised and/or unsupervised machine learning techniques provide a great opportunity to develop advanced computational capabilities to systematically integrate modeling and monitoring, making exposure assessment an integral process of combining all data to better inform pesticide safety evaluation and related decision-making.

We conducted a study using random forest and deep neural network models to enhance the comprehension of whether the field scale farm pond PWC predictions in conjunction with monitoring data can improve the estimation of water exposure, given specific watershed conditions. PWC scenarios, specific to each watershed with monitoring data, were developed for 17 pesticides across the U.S. landscape. By analyzing correlations between monitoring data, PWC predictions, and watershed characteristics, we identified key drivers of exposure. The model results indicate that monitored annual average concentrations serve as a valuable background reference for predicting extreme exposures, and PWC predictions provide supplementary information. The integrative approach using machine learning provides a robust reality check for scenario-based mechanistic models and strengthens watershed vulnerability assessments, enabling more accurate identification of areas sensitive to pesticide uses.

Tuesday Afternoon, August 19, 2025 – Oral session

Surrogates and Extrapolation Among Species in Arthropodan Pollinator Exposure and Effects Assessment:

4:40 PM - 5:05 PM EDT - Room: Hall E – Room 13 (Walter E. Washington Convention Center)

Assessing surrogacy options for listed Lepidoptera: A trait-based approach

Presenter: Eric Peterson

Co-Authors: Paul Glaum, Maura Roberts, Maxime Vaugeois

Overview: The Endangered Species Act (ESA) mandates Ecological Risk Assessments (ERAs) for listed species in chemical compound registrations. However, conducting laboratory experiments on every threatened and endangered species to obtain ecotoxicological data is not realistic nor feasible. For threatened and endangered pollinator and non-target arthropod species, the honey bee (Apis mellifera) is the only surrogate species used in risk assessments. With the large discrepancy in life history traits and vast diversity of terrestrial arthropods, it raises the question if more appropriate surrogates could be used to supplement honey bee data. One potential taxa of refinement are Lepidoptera, which represent nearly half (42%) of all terrestrial arthropod species listed as threatened and endangered under the Endangered Species Act (ESA). Refinement of risk to Lepidoptera may allow for improved mitigation requirements for pesticide uses and help with future regulation guidelines. Thus, our research focuses on developing methodologies to identify potential surrogates for listed Lepidopteran species using comprehensive trait datasets. To fulfill that goal, we have compiled and integrated multiple global, continental, and national datasets encompassing physiological, life-history, geographic, and ecological information for thousands of Lepidopteran species into a centralized database. In collaboration with experts from government, industry, and academia, we identified the most relevant trait variables. These variables serve as inputs for unsupervised learning algorithms, enabling species clustering based on trait similarities. Our findings demonstrate that comprehensive trait data can facilitate the identification and development of suitable surrogacy options for listed Lepidoptera.

Tuesday, August 19, 2025 - POSTER

Environmental Fate, Transport, and Modeling of Agriculturally Related Chemicals:

12:00 PM - 2:00 PM EDT - Room: Hall C (Walter E. Washington Convention Center)

Parameterization of PWC with site specific data from field studies

Presenter: Colleen Roy

Co-Authors: Sarah Crawford, Amy Ritter, Dean Desmarteau, Wenlin Chen

Overview: The EPA has developed a number of standard farm pond scenarios to represent vulnerable farm fields across the United States to model pesticide transport and fate using the Pesticide in Water Calculator (PWC). These scenarios are generic in nature and conservative for the sake of regulatory risk assessment. As these scenarios do not represent real fields it is a challenge to validate how accurately they reflect specific local and vulnerable conditions. Starting in 2017, a field study was conducted at a site in Missouri with runoff vulnerability similar to those represented by the standard pond scenario (e.g., soil hydrogroup C, field to pond ratio, etc.). Data collected from the field study were used to parameterize PWC with the measured soil hydrological properties and pond-specific characteristics. The site-specific PWC was run to compare its results with both the measured field soil and pond concentrations, as well as the representative PWC standard scenario for the Hydrologic Unit Code (HUC) where the site is located. The comparison allows for an evaluation of PWC’s ability to predict real field data when parameterized specifically to the local conditions. This research discusses the deviation in predicted pond estimated environmental concentrations (EECs) between the site-specific PWC and the standard scenarios, providing insights into the model's accuracy and potential areas for improvement in representing local environmental conditions.