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Papers & ReportsWater/Wastewater Assessments2016

Eco-epidemiology of aquatic ecosystems: Separating chemicals from multiple stressors

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A non-toxic environment and a good ecological status are policy goals guiding research and management of chemicals and surface water systems in Europe and elsewhere. Research and policies on chemicals and water are however still disparate and unable to evaluate the relative ecological impacts of chemical mixtures and other stressors. This paper defines and explores the use of eco-epidemiological analysis of surveillance monitoring data sets via a proxy to quantify mixture impacts on ecosystems. Case studies show examples of different, progressive steps that are possible.

Case study data were obtained for various regions in Europe and the United States. Data types relate to potential stressors at various scales, concerning landscape, land-use, in-stream physico-chemical and pollutant data, and data on fish and invertebrates. The proxy-values for mixture impacts were quantified as predicted (multi-substance) Potentially Affected Fractions of species (msPAF), using Species Sensitivity Distribution (SSD) models in conjunction with bioavailability and mixture models.

The case studies summarize the monitoring data sets and the subsequent diagnostic bioassessments. Variation in mixture toxic pressures amongst sites appeared to covary with abundance changes in large (50-86%) percentages of taxa for the various study regions. This shows that an increased mixture toxic pressure (msPAF) relates to increased ecological impacts. Subsequent multi-stressor evaluations resulted in statistically significant, site-specific diagnosis of the magnitudes of ecological impacts and the relative contributions of different stress factors to those impacts. This included both mixtures and individual chemicals. These results allow for ranking stressors, sites and impacted species groups. That is relevant information for water management.

The case studies are discussed in relation to policy and management strategies that support reaching a non-toxic environment and good ecological status. Reaching these goals requires not only focused sectoral policies, such as on chemical- or water management, but also an overarching and solution-focused view.

Posthuma, L., Dyer, S.D., de Zwart, D., Kapo, K.E., Holmes, C.M., Burton Jr., G.A. (2016), Eco-epidemiology of aquatic ecosystems: Separating chemicals from multiple stressors. Science of The Total Environment, Volume 573, 1303-1319.
doi.org/10.1016/j.scitotenv.2016.06.242

Papers & ReportsHome and Personal Care Products, Human Pharmaceuticals, Water/Wastewater Assessments2015

A framework for screening sites at risk from contaminants of emerging concern

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Trace levels of a variety of currently unregulated organic chemicals have been detected in treated wastewater effluents and surface waters that receive treated effluents. Many of these chemicals of emerging concern (CECs) originate from pharmaceuticals and personal care products that are used widely and that frequently are transported “down the drain” to a wastewater treatment plant (WWTP). Actual effects of CECs on aquatic life have been difficult to document, although biological effects consistent with effects of some CECs have been noted. There is a critical need to find appropriate ways to screen wastewater sites that have the greatest potential of CEC risk to biota. Building on the work of several researchers, the authors present a screening framework, as well as examples based on the framework, designed to identify high‐risk versus lower‐risk sites that are influenced by WWTP effluent. It is hoped that this framework can help researchers, utilities, and the larger water resource community focus efforts toward improving CEC risk determinations and management of these risks.

Diamond, J., Munkittrick, K., Kapo, K.E., Flippin, J. (2015), A framework for screening sites at risk from contaminants of emerging concern. Environ Toxicol Chem. 34: 2671-2681. doi:10.1002/etc.3177

Papers & ReportsCrop Protection2018

Assessing and mitigating simulated population‐level effects of 3 herbicides to a threatened plant: Application of a species‐specific population model of Boltonia decurrens.

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Extrapolating from organism‐level endpoints, as generated from standard pesticide toxicity tests, to populations is an important step in threatened and endangered species risk assessments. We apply a population model for a threatened herbaceous plant species, Boltonia decurrens, to estimate the potential population‐level impacts of 3 herbicides. We combine conservative exposure scenarios with dose–response relationships for growth and survival of standard test species and apply those in the species‐specific model. Exposure profiles applied in the B. decurrens model were estimated using exposure modeling approaches. Spray buffer zones were simulated by using corresponding exposure profiles, and their effectiveness at mitigating simulated effects on the plant populations was assessed with the model. From simulated exposure effects scenarios that affect plant populations, the present results suggest that B. decurrens populations may be more sensitive to exposures from herbicide spray drift affecting vegetative stages than from runoff affecting early seedling survival and growth. Spray application buffer zones were shown to be effective at reducing effects on simulated populations. Our case study demonstrates how species‐specific population models can be applied in pesticide risk assessment to bring organism‐level endpoints, exposure assumptions, and species characteristics together in an ecologically relevant context. Environ Toxicol Chem 2018;9999:1–11. © 2018 SETAC

Schmolke, A. , Brain, R. , Thorbek, P. , Perkins, D. and Forbes, V. (2018), Assessing and mitigating simulated population‐level effects of 3 herbicides to a threatened plant: Application of a species‐specific population model of Boltonia decurrens. Environ Toxicol Chem.

Papers & ReportsCrop Protection2017

Population modeling for pesticide risk assessment of threatened species—A case study of a terrestrial plant, Boltonia decurrens

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Although population models are recognized as necessary tools in the ecological risk assessment of pesticides, particularly for species listed under the Endangered Species Act, their application in this context is currently limited to very few cases. The authors developed a detailed, individual‐based population model for a threatened plant species, the decurrent false aster (Boltonia decurrens), for application in pesticide risk assessment. Floods and competition with other plant species are known factors that drive the species’ population dynamics and were included in the model approach. The authors use the model to compare the population‐level effects of 5 toxicity surrogates applied to B. decurrens under varying environmental conditions. The model results suggest that the environmental conditions under which herbicide applications occur may have a higher impact on populations than organism‐level sensitivities to an herbicide within a realistic range. Indirect effects may be as important as the direct effects of herbicide applications by shifting competition strength if competing species have different sensitivities to the herbicide. The model approach provides a case study for population‐level risk assessments of listed species. Population‐level effects of herbicides can be assessed in a realistic and species‐specific context, and uncertainties can be addressed explicitly. The authors discuss how their approach can inform the future development and application of modeling for population‐level risk assessments of listed species, and ecological risk assessment in general. Environ Toxicol Chem 2017;36:480–491.

Schmolke, A. , Brain, R. , Thorbek, P. , Perkins, D. and Forbes, V. (2017), Population modeling for pesticide risk assessment of threatened species—A case study of a terrestrial plant, Boltonia decurrens. Environ Toxicol Chem, 36: 480-491.

 

Papers & ReportsCrop Protection2017

Developing population models: A systematic approach for pesticide risk assessment using herbaceous plants as an example

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Population models are used as tools in species management and conservation and are increasingly recognized as important tools in pesticide risk assessments. A wide variety of population model applications and resources on modeling techniques, evaluation and documentation can be found in the literature. In this paper, we add to these resources by introducing a systematic, transparent approach to developing population models. The decision guide that we propose is intended to help model developers systematically address data availability for their purpose and the steps that need to be taken in any model development. The resulting conceptual model includes the necessary complexity to address the model purpose on the basis of current understanding and available data.

We provide specific guidance for the development of population models for herbaceous plant species in pesticide risk assessment and demonstrate the approach with an example of a conceptual model developed following the decision guide for herbicide risk assessment of Mead’s milkweed (Asclepias meadii), a species listed as threatened under the US Endangered Species Act. The decision guide specific to herbaceous plants demonstrates the details, but the general approach can be adapted for other species groups and management objectives.

Population models provide a tool to link population-level dynamics, species and habitat characteristics as well as information about stressors in a single approach. Developing such models in a systematic, transparent way will increase their applicability and credibility, reduce development efforts, and result in models that are readily available for use in species management and risk assessments.

Amelie Schmolke, Katherine E. Kapo, Pamela Rueda-Cediel, Pernille Thorbek, Richard Brain, Valery Forbes. 2017. Developing population models: A systematic approach for pesticide risk assessment using herbaceous plants as an example, Science of The Total Environment, Volumes 599–600, 1929-1938, https://doi.org/10.1016/j.scitotenv.2017.05.116

Papers & ReportsCrop Protection2016

Population Modeling for Pesticide Risk Assessment of Threatened Species – A Case Study of a Terrestrial Plant, Boltonia decurrens

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Although population models are recognized as necessary tools in the ecological risk assessment of pesticides, particularly for species listed under the Endangered Species Act, their application in this context is currently limited to very few cases. The authors developed a detailed individual-based population model for a threatened plant species, the decurrent false aster (Boltonia decurrens), for application in pesticide risk assessment. Floods and competition with other plant species are known factors that drive the species’ population dynamics and were included in the model approach. The authors use the model to compare the population-level effects of five toxicity surrogates applied to B. decurrens under varying environmental conditions. The model results suggest that the environmental conditions under which herbicide applications occur may have a higher impact on populations than organism-level sensitivities to an herbicide within a realistic range. Indirect effects may be as important as the direct effects of herbicide applications by shifting competition strength if competing species have different sensitivities to the herbicide. The model approach provides a case study for population-level risk assessments of listed species. Population-level effects of herbicides can be assessed in a realistic and species-specific context, and uncertainties can be addressed explicitly. The authors discuss how our approach can inform the future development and application of modeling for population-level risk assessments of listed species, and ecological risk assessment in general. This article is protected by copyright.

Schmolke, A., Brain, R., Thorbek, P., Perkins, D. and Forbes, V. (2016), Population modeling for pesticide risk assessment of threatened species – A case study of a terrestrial plant, Boltonia decurrens. Environ Toxicol Chem. Accepted Author

Papers & ReportsAgriculture and Food, Crop Protection2016

Investigating Past Range Dynamics for a Weed of Cultivation, Silene vulgaris

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Since the last glacial maximum (LGM), many plant and animal taxa have expanded their ranges by migration from glacial refugia. Weeds of cultivation may have followed this trend or spread globally following the expansion of agriculture or ruderal habitats associated with human-mediated disturbance. We tested whether the range expansion of the weed Silene vulgaris across Europe fit the classical model of postglacial expansion from southern refugia, or followed known routes of the expansion of human agricultural practices. We used species distribution modeling to predict spatial patterns of postglacial expansion and contrasted these with the patterns of human agricultural expansion. A population genetic analysis using microsatellite loci was then used to test which scenario was better supported by spatial patterns of genetic diversity and structure. Genetic diversity was highest in southern Europe and declined with increasing latitude. Locations of ancestral demes from genetic cluster analysis were consistent with areas of predicted refugia. Species distribution models showed the most suitable habitat in the LGM on the southern coasts of Europe. These results support the typical postglacial northward colonization from southern refugia while refuting the east-to-west agricultural spread as the main mode of expansion for S. vulgaris. We know that S. vulgaris has recently colonized many regions (including North America and other continents) through human-mediated dispersal, but there is no evidence for a direct link between the Neolithic expansion of agriculture and current patterns of genetic diversity of S. vulgaris in Europe. Therefore, the history of range expansion of S. vulgaris likely began with postglacial expansion after the LGM, followed by more recent global dispersal by humans.

Sebasky, M. E., Keller, S. R. and Taylor, D. R. (2016), Investigating past range dynamics for a weed of cultivation, Silene vulgaris. Ecol Evol. doi:10.1002/ece3.2250

Papers & ReportsCrop Protection2015

Effects of formulation on transport of pyrethroids in residential settings

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Washoff of 17 pyrethroid products resulting from a 1-h, 25.4-mm rainfall occurring 24 h after application was measured in indoor studies with concrete slabs. These products included different pyrethroid active ingredients and a range of formulation types. Based on this replicated study, 5 product pairs with contrasting washoff behaviors were chosen for an outdoor study using 6 full-scale house fronts in central California. Products in 4 of these pairs were applied once to different rectangular areas on the driveway (1 product in each pair to 3 house lots and the other to the remaining 3 house lots). The products in the fifth pair were applied 3 times at 2-mo intervals to vertical stucco walls above the driveway. All house lots received natural and simulated rainfall over 7 mo. Indoor studies showed differences up to 170-fold between paired products, whereas the maximum difference between paired products in the field was only 5-fold. In the pair applied to the wall, 1 product had 91 times the washoff of the other in the indoor study, whereas in the field the same product had 15% lower washoff. These results show that, although the formulation may influence washoff under actual use conditions, its influence is complex and not always as predicted by indoor experiments. Because the formulation also affects insect control, washoff research needs to be conducted together with efficacy testing. Environ Toxicol Chem 2016;35:340–347. © 2015 The Authors. Published by Wiley Periodicals, Inc. on behalf of SETAC.

Jones, R. L., Trask, J. R., Hendley, P., Cox, M. J., Chepega, J. C., Harbourt, C. M. and Davidson, P. C. (2016), Effects of formulation on transport of pyrethroids in residential settings. Environ Toxicol Chem, 35: 340–347. doi:10.1002/etc.3188

Papers & ReportsCrop Protection2015

Hydrologic and Water Quality Modeling: Spatial and Temporal Considerations

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Hydrologic and water quality models are used to help manage water resources by investigating the effects of climate, land use, land management, and water management on water resources. Water-related issues are investigated over a range of scales, i.e., the extent and resolution of the spatial and temporal contexts, which can vary spatially from point to watershed and temporally from seconds to centuries. In addition, models’ formulations may place scale restrictions on their use. In 2012, ASABE published a collection of 22 articles on the calibration, validation, and use of 25 hydrologic and water quality models. Each article detailed the process to follow and the issues that could arise during calibration or application of a specific model. The objective of this article is to synthesize those articles with regard to common spatial and temporal scale principles that should guide selecting, parameterizing, and calibrating a hydrologic model. This article describes how the spatio-temporal extent and resolution of a model application should relate to the modeling objectives, the processes simulated, the parameterization and calibration process, data available for parameterization and calibration, and interpretation of results. Overall, the intended scale of the model should match the scale of the processes that need to be simulated given the modeling objectives, the scale of input and calibration data should be compatible with the scale of the model and with the objectives of the study, and the model should be calibrated at the scale at which the results will be analyzed and interpreted.

Baffaut, C.,  S.M. Dabney, M. Smolen, M.A. Youssef, J.V. Bonta, M.L. Chu, J.A. Guzman, V. Shedekar, M. K. Jha, and J.G. Arnold. Hydrologic and water quality modeling: spatial and temporal considerations. T. ASABE 58(6): 1661-1680

Papers & ReportsCrop Protection2015

Uncertainty Considerations in Calibration and Validation of Hydrologic and Water Quality Models

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Hydrologic and water quality (H/WQ) models are widely used to support site-specific environmental assessment, design, planning, and decision making. Calibration and validation (C/V) are fundamental processes used to demonstrate that an H/WQ model can produce suitable results in a particular application. However, the lack of comprehensive guidelines has led to the use of ad hoc, inconsistent, and incomplete C/V processes, which have made it difficult to interpret the myriad of published modeling studies, reduced the utility of many modeling applications, and slowed the advancement of H/WQ modeling. The objective of this article is to provide a generalized structure and process to assist modelers in developing a C/V strategy for H/WQ modeling applications. These best practice recommendations were developed based on an expansive review of the modeling literature, including a special collection of articles on H/WQ model calibration, validation, and use, as well as extensive discussion and debate among the authors. The model C/V recommendations include careful consideration, execution, and documentation of the following elements: (1) goals of model use, (2) data and parameters used in C/V, and (3) model C/V processes. Considerations in element 3 include the warm-up period, C/V strategy complexity, C/V process staging, spatiotemporal allocation of C/V comparison data, manual vs. automatic C/V, and additional diagnostics. Notable examples from the literature are provided for each strategy element. The comprehensive C/V strategy described herein will allow for better interpretation of future modeling studies, improved utility of modeling applications, and more systematic advancement of H/WQ models.

Guzman, J.A.,  A. Shirmohammadi, A. Sadeghi, X. Wang, M.L. Chu, M.K. Jha, P. Parajuli, D. Harmel, Y. Khare, and J. Hernandez. Uncertainty considerations in calibration and validation of hydrologic and water quality models. T. ASABE 58(6): 1745-1762