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.
PresentationsCrop Protection, Water/Wastewater Assessments2018
Atrazine Ecological Monitoring Program: Study design and conduct
Room: Ballroom East – Theater 4
Date: Monday August 22, 2018
Start Time: 8:35AM
Presentation Code: AGRO 228
A high sampling frequency watershed monitoring program, Atrazine Ecological Monitoring Program (AEMP), which began in 2004, has collected over 28,000 water samples representing 284 site years from 75 watersheds across 13 states in the Midwest and the South. The AEMP consists of compliance-based, targeted monitoring in small watershed (< 40 mi2) headwater streams, and is designed to identify environmental conditions in corn and sorghum agricultural watersheds that are susceptible to high surface runoff potential. The AEMP sampling design captured atrazine runoff events following chemical applications to corn and sorghum agriculture when residue levels in the receiving stream are expected to be at their maximum. The breadth of atrazine concentration data from water samples accompanied by watershed characteristics, meteorological data and agronomic data provide a comprehensive understanding of atrazine transport mechanism. The AEMP monitoring data quantifies the upper 20th centile of potential aquatic exposure to atrazine in corn and sorghum growing areas in the United States. The presentation will provide an overview of the site selection process, study design, sample and data collection process, and a summary of important findings.
Jennifer Trask, Les Carver, Megan Cox, Kate Marincic (Waterborne Environmental), Sun Mao Chen (Syngenta Crop Protection). Atrazine Ecological Monitoring Program: Study design and conduct. ACS 2018. Presentation. Boston, MA.
PresentationsCrop Protection, Water/Wastewater Assessments2018
Interpreting water quality monitoring observations through modeling: PRZM/SWAT and SEAWAVE-Q
Room: Ballroom East – Theater 4
Date: Wednesday August 22, 2018
Start Time: 10:35AM
Presentation Code: AGRO 231
Water quality monitoring data, specifically pesticides, can represent best-available exposure profiles related to ecological risk assessment; however, there are challenges in synthesizing these data toward making strong 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 systems 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-Q 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 was assessed against observed, daily concentration measurements as well as hypothetical data collection frequency and timing (derived from sub-sampling the same data sets). Results suggest that a process-based modeling approach, such as PRZM/SWAT, may be more advantageous when calibration data are available.
Daniel Perkins, Andy Jacobson, Colleen Roy, Farah Abi-Akar (Waterborne Environmental), Wenlin Chen (Syngenta Crop Protection). Interpreting water quality monitoring observations through modeling: PRZM/SWAT and SEAWAVE-Q. ACS 2018. Presentation. Boston, MA.
Modelling Microplastics in Rivers in the US (339)
Pollution with nano- and microplastics (MPs; particles < 5 mm) is a topic of emerging concern and as such receives growing interest. Although measurement and monitoring data are indispensable, there also is a need for estimated concentrations to enable prospective assessments and to guide analysis of retrospective ecological analyses. Besseling et al (2017) provided the NanoDUFLOW model, a detailed MP aggregation-sedimentation model integrated in a hydrological and particle transport model. A much larger scale model potentially suitable to simulate MPs originating from WWTPs is the iSTREEM® model, which has been developed to estimate chemical concentration distributions for all rivers and streams of the USA receiving WWTP discharges. Here we merge these two riverine modeling worlds: NanoDUFLOW with iSTREEM for MPs, to simulate spreading of MPs from WWTP point sources in US waterways and to assess export to the Great Lakes for a range of particle sizes. This combines the mechanistic realism of NanoDUFLOW, accounting for formation and settling of heteroaggregates, with the US well-established iSTREEM implementation. We modeled floating as well as non-buoyant MP, for diverse sizes, from 100 nm to 10 mm, a range that incorporates the theoretical parabolic size-settling relationship reported by Besseling et al (2017). Depth dependent in-stream first order removal rate constants simulated with NanoDUFLOW were combined with standard iSTREEM output (which was used to simulate the emission, transport and water column concentrations of MP) in an Excel-based post-processing phase, without modifing the iSTREEM model directly. Simulations were spatially explicit with MP concentrations being modeled for the Sandusky River watershed in Ohio (~3500 km2). Emissions were based on per capita usage and population served for each of the 20 WWTPs within the watershed. Modelling results show the effects of population density, MP size and density on riverine concentrations and export to Lake Erie. Buoyant as well as the smallest non-buoyant MP fractions can be transported over long distances, reaching receiving waters such as the Great Lakes. In contrast, larger non-buoyant MPs settle more locally in the vicinity of the WWTPs. Simulating depth-dependent removal as demonstrated here could be incorporated into the core iSTREEM code in order to efficiently process all US waterways impacted by WWTPs, as well as examining ultimate marine discharge proportions by particle size.
A. Koelmans (Wageningen University); C.M. Holmes (Waterborne Environmental). Modelling Microplastics in Rivers in the US. SETAC EU 2018. Presentation.
Prospective Aquatic Risk Assessment for Mixed Land Use Catchments: A Tool to Combine Multi-Source Chemical Emissions Over Time
SETAC Session Title: Improving the Environmental Assessment of Complex Composition Substances and Mixtures for Chemicals Management
Presentation Date: Thursday November 16, 2017
Presentation Time: 3:40 PM
Location: Session Room 101BI
In 2015, a SETAC Pellston® workshop was held to help inform decision making around aquatic mixture risk assessments of chemicals using exposure scenarios for agricultural, domestic, and urban scenarios. Prospective emissions of 37 chemicals were estimated and combined into daily mixture profiles over a 10-year period. The mixture risk assessment looked at daily individual substance risk quotients (RQs) and multiple substance ∑RQ (assuming concentration addition), along with implementation of the Maximum Cumulative Ratio (MCR) approach. Risk was examined at the bottom of a hypothetical catchment containing a changeable configuration of sub-catchments defined by three land use types (agricultural, city [domestic + urban], natural). An underlying spreadsheet-based model was developed to integrate daily loadings of individual chemicals from each sub-catchment, combined with a simplified hydrologic model, to produce a time series of mixture profiles at the catchment outlet. Catchment configuration is changed by varying the placement, type and number of sub-catchments in the system. Model results show a high spatio-temporal variability of individual chemical concentrations and their mixtures based on catchment configuration. Even constant emissions of household chemicals showed variability in concentration related to river flow driven by rain events. The outcome of the overall Pellston study demonstrated that a scenario-based approach can be used to determine whether mixtures of chemicals pose risks over and above any identified using existing approaches for single chemicals, how often and to what magnitude, and ultimately which mixtures (and dominant chemicals) cause greatest concern. In this talk focusing on the underlying catchment model, mixture risk results for different catchment configurations will be presented.
Christopher Holmes (Waterborne Environmental), Colin Brown (University of York), Dick De Zwart (Mermayde), Jerome Diamond (Tetra Tech), Scott Dyer (The Procter & Gamble Company), Stuart Marshall (Unilever), Leo Posthuma (RIVM; Radboud University). Prospective Aquatic Risk Assessment for Mixed Land Use Catchments: A Tool to Combine Multi-Source Chemical Emissions Over Time. Platform SETAC 2017. Minneapolis, MN.
Advances in the Refined National-Scale Drinking Water Assessment Framework: Case Study Chlorpyrifos
In the US pesticide regulatory scheme for human dietary exposure, estimates of the surface-derived drinking water contribution are assessed with simple scenario-based modeling techniques. Such estimates can be a useful and conservative approach in a tiered risk assessment to systematically eliminate potential concern; however, the limited conclusions that can be reached are often not adequate to address the true extent of potential exposures. The current work focuses on advances in national-scale drinking water concentration estimation techniques, using chlorpyrifos as a case study. The method incorporates spatially-distributed environmental and management information in a risk framework at the watershed (HUC12) scale. Concepts of standard scenarios to create conservative, regionally representative (at an extent wider than HUC12) estimates of exposure patterns were applied and then were distributed at the HUC12 watershed scale by matching them with HUC12-specific cropping patterns derived from five years of cropland data layer (CDL) data. As a conservative first approximation, it was assumed that a drinking water source co-occurs within every HUC12 where applications were made to labeled crops. In this way, HUC12-specific exposure estimates were derived for all chlorpyrifos-labeled crops. Then, county-level community water system (CWS) locations were included to eliminate risk concern from HUC12 watersheds that did not co-occur with a CWS. Results from this first approximation eliminated concern in 83% of HUC12 watersheds with labeled crop(s). The impact of refinements and assumptions on the remaining 17% of HUC12 watersheds was further explored. Potential refinements included higher-resolution rainfall, soils, runoff and erosion data inputs, more realistic environmental fate, application timing and application type information, and percent crop treated. Significant impact was observed from the inclusion of these refinements, with at least 92% of the remaining HUC12 watersheds yielding a conclusion of no concern. Characterization of potential risk in a spatially-distributed fashion increases risk characterization accuracy/certainty because of the inclusion of best-available data to inform estimates of exposure and co-occurrence. In conclusion, it was discovered that spatially-distributed environmental and management factors must be considered to increase certainty and characterize potential risk, rather than relying solely on a scenario-based approach.
Dan Perkins*, Nathan Snyder, Josh Amos, Kendall Jones (Waterborne), Patrick Havens (Dow AgroSciences), Nick Poletika (Risk Analysis Solutions). “Advances in the Refined National-Scale Drinking Water Assessment Framework: Case Study Chlorpyrifos.” Poster. SETAC NA. 2016.
Environmental exposure assessment of sucralose in receiving waters at differing spatial scales
- Session title: Advances in exposure modelling: bridging the gap between research and application
- Presentation type: Poster
- Presentation room: Exhibition Hall opens at 8:10AM
- Presenting Author: Chris Holmes
Down-the-drain exposure models provide a valuable screening-level tool for estimating environmental exposure to product ingredients which are treated and discharged at municipal wastewater treatment plants. We present an environmental exposure assessment for sucralose, an artificial sweetener which ultimately ends up in the environment via down the drain emissions. Exposure modeling was performed using the iSTREEM® model, a publically-available web-based model supported by the American Cleaning Institute (www.istreem.org) which estimates spatially-explicit concentrations of chemicals in effluent and receiving waters across the U.S. at mean and low flow conditions. Wastewater treatment facility influent loadings of sucralose were estimated using per-capita usage derived from market sales volume combined with individual facility population served and daily flow estimates within the iSTREEM® model. The screening-level assessment used an assumption of zero removal during treatment and no in-stream decay, resulting in a representation of “worst-case” environmental exposure estimates. Three case studies of modeling at different spatial extents are presented: national scale of the continental U.S., regional scale of the Lake Erie drainage basin, and local scale of the Grand River Watershed in Canada. US-wide predicted environmental concentrations (PECs) estimated by the model at mean annual flow conditions were comparable to sucralose concentrations typically expected to be observed in the field, with a 90th percentile PEC in surface waters of approximately 1.9 µg/L. Watershedscale modeling of the Grand River was compared to published data from 23 sites measured in 2007-2009. This local assessment was enhanced with temporally-specific adjustments to flow. Once time-specific gaging data were added, the model predicted a comparable exposure pattern to those measured across the 23 sites. Maps of the estimated geographic distribution of US-wide and Grand River watershed river concentrations are presented using geo-referenced concentration data generated by the iSTREEM® model. These screening-level environmental exposure assessments provide an estimated distribution of PECs in a spatial and potentially temporal context. These can be used to inform risk management and/or subsequent higher-tier assessment.
Katherine Kapo, Raghu Vamshi, Megan Sebasky, Duane Huggett, Chris Holmes (Waterborne Environmental). “Environmental exposure assessment of sucralose in receiving waters at differing spatial scales”. Poster. SETAC EU 2016.
Papers & ReportsWater/Wastewater Assessments2015
Stream Vulnerability to Widespread and Emergent Stressors: A Focus on Unconventional Oil and Gas
Multiple stressors threaten stream physical and biological quality, including elevated nutrients and other contaminants, riparian and in-stream habitat degradation and altered natural flow regime. Unconventional oil and gas (UOG) development is one emerging stressor that spans the U.S. UOG development could alter stream sedimentation, riparian extent and composition, in-stream flow, and water quality. We developed indices to describe the watershed sensitivity and exposure to natural and anthropogenic disturbances and computed a vulnerability index from these two scores across stream catchments in six productive shale plays. We predicted that catchment vulnerability scores would vary across plays due to climatic, geologic and anthropogenic differences. Across-shale averages supported this prediction revealing differences in catchment sensitivity, exposure, and vulnerability scores that resulted from different natural and anthropogenic environmental conditions. For example, semi-arid Western shale play catchments (Mowry, Hilliard, and Bakken) tended to be more sensitive to stressors due to low annual average precipitation and extensive grassland. Catchments in the Barnett and Marcellus-Utica were naturally sensitive from more erosive soils and steeper catchment slopes, but these catchments also experienced areas with greater UOG densities and urbanization. Our analysis suggested Fayetteville and Barnett catchments were vulnerable due to existing anthropogenic exposure. However, all shale plays had catchments that spanned a wide vulnerability gradient. Our results identify vulnerable catchments that can help prioritize stream protection and monitoring efforts. Resource managers can also use these findings to guide local development activities to help reduce possible environmental effects.
Entrekin SA, Maloney KO, Kapo KE, Walters AW, Evans-White MA, Klemow KM (2015) Stream Vulnerability to Widespread and Emergent Stressors: A Focus on Unconventional Oil and Gas. PLoS ONE 10(9): e0137416. doi:10.1371/journal.pone.0137416
Sucralose in Wastewater Effluent and Receiving Waters in the U.S.: An Environmental Exposure Assessment
POSTER ID: MP032
PRESENTATION DATE: Monday, November 2, 2015
LOCATION: Exhibit Hall
Down-the-drain exposure models provide a valuable screening-level tool for estimating environmental exposure to product ingredients which are treated and discharged at municipal wastewater treatment plants. We present an environmental exposure assessment for sucralose, an artificial sweetener used in a variety of consumer products. Exposure modeling was performed using the iSTREEM® model, a free and publically-available web-based model supported by the American Cleaning Institute (www.istreem.org) which estimated concentrations of sucralose in effluent and receiving waters across the U.S. at mean annual and low flow conditions. Wastewater treatment facility influent loadings of sucralose were estimated using per-capita usage derived from market sales volume combined with individual facility population served and daily flow estimates within the iSTREEM® model. The screening-level assessment used conservative assumptions for the exposure modeling including an assumption of zero removal during treatment and no in-stream decay, resulting in a representation of “worst-case” environmental exposure estimates. Environmental concentrations estimated by the model at mean annual flow conditions were comparable to sucralose concentrations typically expected to be observed in the field, with a 90th percentile predicted environmental concentration (“PEC”) in surface waters of approximately 1.9 µg/L. Maps of the estimated geographic distribution of river concentrations of sucralose are presented using geo-referenced concentration data generated by the iSTREEM® model. In addition to screening-level assessment using national estimates, a refined approach to the modeling was explored by incorporating spatial variation of chemical loading based on demographic factors associated with sucralose usage (e.g., prevalence of diabetes, obesity, etc.). Screening-level environmental exposure assessments such as the current modeling exercise provide an estimated distribution of environmental concentrations of a chemical of interest in a geographic context, which can be used to inform risk management and/or subsequent higher-tier assessment.
Katherine Kapo, Megan Sebasky, Raghu Vamshi, Duane Huggett, Christopher Holmes, Waterborne Environmental. “Sucralose in Wastewater Effluent and Receiving Waters in the U.S.: An Environmental Exposure Assessment”. SETAC Salt Lake City November 2015.
The Effects of Land Use Changes and Climate Variability on Reservoir Sedimentation for the Little Washita River Experimentation Watershed
The lack of vegetation combined with periods of intense rainfall causes increased erosion and flooding. The research study goal was to determine the effects of land use, climate variability, and soil type on sedimentation of reservoirs that were constructed to prevent and manage soil erosion and flooding. The study area was the Little Washita Reservoir Experimentation Watershed (LWREW). The main land use categories in the LWREW (610 km2) include 65% grassland/shrubland, 16% cropland (winter wheat and summer crops;), 13% forest, and 6% roads/urban (Fig. 1a and 1b). There is a total of 45 reservoirs (Fig. 1a), out of which samples were collected from twelve (Fig. 1b). The presentation for this ongoing study focuses only on two reservoirs (21 and 26; Fig. 3). Figure 1c presents the STATSGO soil mapping units for the LWREW. Reservoir 21 falls under units OK124 and OK088 while reservoir 26 falls under unit OK105. Soil mapping units OK124 and OK088 are predominantly silt/sand, while OK105 is predominantly silt/clay.
H.M. Skibstead, D.N. Moriasi, J.L. Steiner, P.J. Starks, J.A. Guzman, and J.A. Verser. The Effects of Land Use Changes and Climate Variability on Reservoir Sedimentation for the Little Washita River Experimentation Watershed. SWCS International Annual Meeting, Greensboro, NC. July 26-29, 2015.