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DOE OSTI2015

SORTIE DB - Source term integrated environmental management disposal facility database - 15249

The Environmental Management Disposal Facility (EMDF) in Oak Ridge, Tennessee, is a proposed U.S. Department of Energy low-level Comprehensive Environmental Response Compensation and Liability Act (CERCLA) waste disposal facility with an operational start in the early 2020's. As a DOE low-level waste disposal facility, it is subject to DOE Order 435.1, requiring a composite analysis and possibly a performance assessment. The Source Term Integrated EMDF Data Base - SORTIE DB - provides source term estimates used in these assessments. An Oak Ridge Office of Environmental Management (OREM) Federal and Contractor team developed this state-of-the-art descriptive analytics and visualization schema. DOE OREM senior management has recognized complementary beneficial uses of SORTIE DB in decisions for accelerating clean-up progress, dealing with conflicting sequencing and budget priorities, and enhancing stakeholder and regulatory interfaces. SORTIE DB is designated as an OREM planning tool. SORTIE DB contains estimated forecast waste volumes and masses for over 800 Decontamination and Decommissioning (D and D) and Remedial Action (RA) sequenced baseline packages over the next 25+ years. Available characterization data, radionuclide identification and concentrations, and data from safety basis and emergency management documents are incorporated into SORTIE DB. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2015

Needs for integrated risk assessment to support optimal environmental management decisions - 15455

Cleaning up legacy waste from 50 years of nuclear weapons production and energy research still remains a challenge for the U.S. Department of Energy (DOE). The DOE environmental management program is currently forecasted to run through at least late 2060's with an estimated liability of $204 billion. Risks to human health of workers and the public, the ecological system, and nuclear safety of cleanup activities continue to drive the cost of DOE's cleanup programs. Currently, these risks are generally assessed and managed independently of each other. Except for DOE self-regulated on-site disposal activities of low-level radioactive waste, risks to human health and the environment are generally under the purview of U.S. Environmental Protection Agency and State regulatory agencies, while nuclear safety risks are regulated by DOE with oversight from the U.S. Nuclear Regulatory Commission and the Defense Nuclear Facilities Safety Board where appropriate. When managing health and environmental risks, the individual regulatory authorities often use an area-by-area (or unit-by-unit), contaminant-by-contaminant (chemical-by-chemical or radionuclide-by-radionuclide) approach, focusing on a single medium (soil, water, or air), a single source (e.g., a burial ground or a processing facility), and a single receptor (e.g, a groundwater well or a creek). This level of segregation in risk evaluations by risk category, geographical location, and operational unit, as well as the corresponding separation of regulatory authorities poses a significant challenge to reaching an optimal decision in prioritizing and managing cleanup activities. This management challenge adds another layer of complexity to large-scale cleanup effort at complex sites such as the Hanford site in eastern Washington. Therefore, to support a scientifically sound, operationally robust decision making process, there is a need for an integrated, holistic approach to risk assessment that addresses the combined effects of all major contributing factors. Previous studies have pointed out the need for integrated risk assessments that address multi-contaminant, multimedia, multi-pathway exposures, for the purposes of evaluating risks to human health and the environment. We believe that a comprehensive risk assessment should also take into nuclear safety risks that are associated with handling of nuclear material either retrieved from burial sites or to be decommissioned from nuclear facilities. Recent efforts, such as the Consortium for Risk Evaluation with Stakeholder Participation (CRESP)-led Hanford site-wide independent risk review that will categorize all types of risks at the Hanford site and the DOE complex-wide risk review mandated by the Fiscal Year 2014 Consolidated Appropriations Act ('Omnibus bill'), are beginning to more comprehensively address this need. This paper provides a categorization of various types of risks present at typical DOE sites, reviews the current risk assessment and management practices, and discusses the needs for integrating nuclear safety into performance and risk assessments for optimal cleanup decisions. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Applications Using the Advanced Simulation Capability for Environmental Management Tool-set - 16335

The Office of Soil and Groundwater of the U.S. Department of Energy (DOE) Office of Environmental Management (EM) developed the Advanced Simulation Capability for Environmental Management (ASCEM). The ASCEM tool-sets can be used for making informed choices in uncertain and complex environments, where cost-benefits of environmental impacts and human health need to be considered. The deployments and demonstrations show how ASCEM provides a unified framework that facilitates efficient modeling and analyses to address costs and benefits of engineering and remediation decisions: - Evaluation of engineered remediation and monitoring strategies at the Savannah River Site (SRS) F-Area in collaboration with the Office of Soil and Groundwater Remediation, Attenuation-Based Remedies in the Subsurface Applied Field Research Initiative; - Assessment of performance assessment issues and waste tank closure at SRS; - Evaluation of alternative conceptual models for the deep vadose zone at the Hanford Site, supporting waste tank closure. The ASCEM tool-sets enable computationally efficient representations of the complex subsurface systems, including fractured and faulted volcanic and carbonate aquifers, a very deep water table, and multiple contaminant sources. The applications demonstrate that deployment of the ASCEM tool-sets provides an opportunity to reduce conservatisms in modeling assessments and allows detailed investigation of alternative conceptual models. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

ZEM: Integrated Framework for Real-Time Data and Model Analyses for Robust Environmental Management Decision Making - 16438

Typically environmental management (EM) problems require analysis of large and complex data sets originating from concurrent data streams with different data collection frequencies and pedigree. These big data sets require on-the-fly analysis, assimilation and integration into a series of models with different complexity for various types of model-based analyses. This is needed to provide fast iterative model analyses based on the latest available data to guide decision-making. Furthermore, the data and model are associated with uncertainties. The uncertainties are probabilistic (e.g. measurement errors) and non-probabilistic (unknowns, e.g. alternative conceptual models characterizing site conditions). To address all of these issues, we have developed an integrated framework for real-time data and model analyses for environmental decision-making called ZEM. The framework allows for seamless and on-the-fly integration of data and modeling results for robust and scientifically-defensible decision-making applying advanced decision analyses tools such as Bayesian-Information-Gap Decision Theory (BIG-DT). The framework also includes advanced methods for optimization that are capable of dealing with a large number of unknown model parameters, and surrogate (reduced order) modeling capabilities based on support vector regression techniques. The framework is predominantly coded in Julia, a state-of-the-art high-performance programing language (http://julialang.org) and incorporates the MADS computational tools (Model Analysis and Decision Support; http://mads.lanl.gov). We demonstrate the application of ZEM for data and model analyses at the LANL Chromium site. The ZEM framework will be released as open-source code and can be applied to any environmental management site. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Radon Considerations at Environmental Remediation Sites - 19469

Radon and how it is regulated poses many challenges to the U.S. Army Corps of Engineers (USACE) in executing the Formerly Utilized Sites Remedial Action Program (FUSRAP). These challenges include:, terminology; radon measurement methods and limitations; state certification and testing requirements; limited and potentially conflicting federal guidance; background considerations; and limited experience regarding application of guidance; among others. These challenges and others are discussed in detail. The FUSRAP Maywood Superfund Site (FMSS) is presented as a case study demonstrating these challenges and considerations to mitigate or address the challenges. The USACE, U.S. Environmental Protection Agency (USEPA), and the New Jersey Department of Environmental Protection (NJDEP) (NJDEP) have spent several years working on and continue to work through the radon issues at FMSS. The FMSS experience, information, and solutions presented in this paper will be helpful to other environmental sites with radium and thorium contamination. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Response of Subsurface Nitrogen-Cycling Microbial Communities to Environmental Fluctuations (Final Technical Report)

Riparian floodplains are dynamic ecosystems linking terrestrial and riverine systems. These floodplains experience hydrological shifts such as changes in water table height, flooding, and drought and can be ‘hotspots’ of biogeochemical cycling due to shifting sediment moisture (and saturation) and subsurface exchanges of water, nutrients, and other compounds across different sediment layers. Subsurface microbial communities are the primary drivers of biogeochemical processes in floodplains, and thus their structure and function can directly influence both surface and groundwater quality. The microbial nitrogen (N) cycle is particularly important in floodplains as it affects nutrient availability and removal. Two functional guilds of chemoautotrophic (i.e. CO2-fixing) microorganisms are responsible for the first oxidative step of the N cycle, nitrification: ammonia-oxidizing archaea (AOA) and bacteria (AOB) catalyze the oxidation of ammonia to nitrite, while nitrite-oxidizing bacteria (NOB) oxidize nitrite to nitrate. Despite the critical role nitrification plays in N-cycling in both terrestrial and aquatic ecosystems, our understanding of the diversity, ecophysiology, and activity of nitrifying organisms in subsurface floodplain soils/sediments is extremely limited. To help address this critical knowledge gap, the overarching goal of this project was to determine how shifts in key environmental parameters and gradients impact microbial N-cycling communities/processes, with particular emphasis on nitrification, within hydrologically-variable floodplain sediments in the Wind River Basin near Riverton, Wyoming. The three specific objectives of this project were to: (1) to associate in situ environmental drivers of N cycling with distinct functional guilds; (2) determine the guild response to variation in key ecosystem drivers; and (3) develop a dynamic ecosystem model of the microbial N cycle with the Riverton subsurface using community genomic and biogeochemical data collected in the first two objectives. Over the course of this project, we employed both 16S rRNA gene amplicon sequencing and genome-resolved metagenomics to examine the phylogenetic diversity and metabolic potential of subsurface nitrifier communities within 68 samples collected across multiple sites, depths, and time points within the Riverton floodplain, allowing for both spatial and temporal investigations at different scales. This project benefitted tremendously from recent advances in high-throughput sequencing technologies coupled with dramatic improvements in the computational tools and algorithms available for analyzing such large, complex genomic datasets. By pairing these cutting-edge genomic approaches with depth-resolved sampling and detailed geochemical analyses of the Riverton floodplain, we have gained novel insights into the structure and function of subsurface nitrifier communities in relation to both hydrology and biogeochemistry. This project resulted in the most detailed and comprehensive characterization of N-cycling floodplain microbial communities to date and will hopefully inspire and pave the way for future studies using similar approaches in other floodplains. Indeed, such information is critical for understanding subsurface biogeochemical cycling and how elemental stores are altered from perturbations initiated by the water cycle within floodplains. Finally, because of the terrestrial-aquatic nature of the Riverton floodplain, results from this project are also of relevance to disciplines such as soil science, estuarine science, limnology & oceanography, biogeochemistry, geobiology, environmental engineering, as well as genomics and data science.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Sustainability principles in strategic environmental assessment: A framework for analysis and examples from Italian urban planning

This paper presents a framework for analysing the degree of consideration of sustainability principles in Strategic environmental assessment (SEA), and demonstrates its application to a sample of SEA of Italian urban plans. The framework is based on Gibson's (2006) sustainability principles, which are linked to a number of guidance criteria and eventually to review questions, resulting from an extensive literature review. A total of 71 questions are included in the framework, which gives particular emphasis to key concepts, such as intragenerational and intergenerational equity. The framework was applied to review the Environmental Report of the urban plans of 15 major Italian cities. The results of this review show that, even if sustainability is commonly considered as a pivotal concept, there is still work to be done in order to effectively integrate sustainability principles into SEA. In particular, most of the attention is given to mitigation and compensation measures, rather than to actual attempts to propose more sustainable planning decisions in the first place. Concerning the proposed framework of analysis, further research is required to clarify equity concerns and particularly to identify suitable indicators for operationalizing the concepts of intra/inter-generational equity in decision-making. -- Highlights: ► A framework was developed in order to evaluate planning against sustainability criteria. ► The framework was applied to analyse how sustainable principles are addressed in 15 Italian SEA reports. ► Over 85% of the reports addressed, to some extent, at least 40% of the framework questions. ► Criteria explicitly linked to intra and inter-generational equity are rarely addressed.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Conceptualizing strategic environmental assessment: Principles, approaches and research directions

Increasing emphasis has been placed in recent years on transitioning strategic environmental assessment (SEA) away from its environmental impact assessment (EIA) roots. Scholars have argued the need to conceptualize SEA as a process designed to facilitate strategic thinking, thus enabling transitions toward sustainability. The practice of SEA, however, remains deeply rooted in the EIA tradition and scholars and practitioners often appear divided on the nature and purpose of SEA. This paper revisits the strategic principles of SEA and conceptualizes SEA as a multi-faceted and multi-dimensional assessment process. It is suggested that SEA can be conceptualized as series of approaches operating along a spectrum from less to more strategic – from impact assessment-based to strategy-based – with each approach to SEA differentiated by the specific objectives of SEA application and the extent to which strategic principles are reflected in its design and implementation. Advancing the effectiveness of SEA requires a continued research agenda focused on improving the traditional SEA approach, as a tool to assess the impacts of policies, plans and programs (PPPs). Realizing the full potential of SEA, however, requires a new research agenda — one focused on the development and testing of a deliberative governance approach to SEA that can facilitate strategic innovations in PPP formulation and drive transitions in short-term policy and initiatives based on longer-term thinking. - Highlights: • SEA facilitates strategic thinking, enabling transitions toward sustainability. • SEA is conceptualized as a spectrum of approaches, from IA-based to strategy-based. • Each approach variably emphasizes strategic principles in its design and practice. • There is no one conceptualization of SEA that is best, SEA is fit for PPP purpose. • Research is needed to advance SEA to facilitate strategic PPP transformations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Immersive virtual reality and environmental noise assessment: An innovative audio–visual approach

Several international studies have shown that traffic noise has a negative impact on people's health and that people's annoyance does not depend only on noise energetic levels, but rather on multi-perceptual factors. The combination of virtual reality technology and audio rendering techniques allow us to experiment a new approach for environmental noise assessment that can help to investigate in advance the potential negative effects of noise associated with a specific project and that in turn can help designers to make educated decisions. In the present study, the audio–visual impact of a new motorway project on people has been assessed by means of immersive virtual reality technology. In particular, participants were exposed to 3D reconstructions of an actual landscape without the projected motorway (ante operam condition), and of the same landscape with the projected motorway (post operam condition). Furthermore, individuals' reactions to noise were assessed by means of objective cognitive measures (short term verbal memory and executive functions) and subjective evaluations (noise and visual annoyance). Overall, the results showed that the introduction of a projected motorway in the environment can have immediate detrimental effects of people's well-being depending on the distance from the noise source. In particular, noise due to the new infrastructure seems to exert a negative influence on short term verbal memory and to increase both visual and noise annoyance. The theoretical and practical implications of these findings are discussed. -- Highlights: ► Impact of traffic noise on people's well-being depends on multi-perceptual factors. ► A multisensory virtual reality technology is used to simulate a projected motorway. ► Effects on short-term memory and auditory and visual subjective annoyance were found. ► The closer the distance from the motorway the stronger was the effect. ► Multisensory virtual reality methodologies can be used to study environmental impact.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Spheres of public conversation: Experiences in strategic environmental assessment

This paper draws on earlier research, a national review of Scottish SEA practice and a survey of practitioners and stakeholders engaged in SEA and spatial planning in one Scottish city-region, to explore claims being made in the academic literature for Strategic Environmental Assessment (SEA) as a tool for deliberative plan-making. We consider whether there is evidence that Scottish SEA practice is helping create more inclusive plan-making processes in light of recent legislative changes, thereby fulfilling one of the expectations of Scottish Government. The macro analysis found that although there are opportunities for stakeholders to engage in the Scottish SEA process the level in practice is extremely low, a finding which mirrors experience in England and elsewhere. The more detailed micro analysis reveals a more nuanced picture within the spatial planning system, however, suggesting the existence of two distinct spheres of public conversations, one characterised by active dialogue about the environmental effects of alternative strategies amongst public sector stakeholders and the other involving non-governmental stakeholders and community groups in a much more limited way. The paper concludes with a discussion of possible explanations for this outcome, concerning asymmetric incentive structures and the application of power, and a consideration of the implications in relation to the competing discourses of SEA. -- Highlights: • We examine the extent to which Scottish SEA is helping promote inclusive plan-making. • Low levels of stakeholder engagement generally in Scottish SEA. • Stronger SEA dialogue amongst public agencies than with the wider community. • Importance of incentive structures and power capture in framing SEA public conversations.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Knowledge brokering on emissions modelling in Strategic Environmental Assessment of Estonian energy policy with special reference to the LEAP model

Strategic Environmental Assessment (SEA) serves as a platform for bringing together researchers, policy developers and other stakeholders to evaluate and communicate significant environmental and socio-economic effects of policies, plans and programmes. Quantitative computer models can facilitate knowledge exchange between various parties that strive to use scientific findings to guide policy-making decisions. The process of facilitating knowledge generation and exchange, i.e. knowledge brokerage, has been increasingly explored, but there is not much evidence in the literature on how knowledge brokerage activities are used in full cycles of SEAs which employ quantitative models. We report on the SEA process of the national energy plan with reflections on where and how the Long-range Energy Alternatives Planning (LEAP) model was used for knowledge brokerage on emissions modelling between researchers and policy developers. Our main suggestion is that applying a quantitative model not only in ex ante, but also ex post scenario modelling and associated impact assessment can facilitate systematic and inspiring knowledge exchange process on a policy problem and capacity building of participating actors. - Highlights: • We examine the knowledge brokering on emissions modelling between researchers and policy developers in a full cycle of SEA. • Knowledge exchange process can evolve at any modelling stage within SEA. • Ex post scenario modelling enables systematic knowledge exchange and learning on a policy problem.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Large-scale renewable energy project barriers: Environmental impact assessment streamlining efforts in Japan and the EU

Environmental Impact Assessment (EIA) procedures have been identified as a major barrier to renewable energy (RE) development with regards to large-scale projects (LS-RE). However EIA laws have also been neglected by many decision-makers who have been underestimating its impact on RE development and the stifling potential they possess. As a consequence, apart from acknowledging the shortcomings of the systems currently in place, few governments momentarily have concrete plans to reform their EIA laws. By looking at recent EIA streamlining efforts in two industrialized regions that underwent major transformations in their energy sectors, this paper attempts to assess how such reform efforts can act as a means to support the balancing of environmental protection and climate change mitigation with socio-economic challenges. Thereby this paper fills this intellectual void by identifying the strengths and weaknesses of the Japanese EIA law by contrasting it with the recently revised EIA Directive of the European Union (EU). This enables the identification of the regulatory provisions that impact RE development the most and the determination of how structured EIA law reforms would affect domestic RE project development. The main focus lies on the evaluation of regulatory streamlining efforts in the Japanese and EU contexts through the application of a mixed-methods approach, consisting of in-depth literary and legal reviews, followed by a comparative analysis and a series of semi-structured interviews. Highlighting several legal inconsistencies in combination with the views of EIA professionals, academics and law- and policymakers, allowed for a more comprehensive assessment of what streamlining elements of the reformed EU EIA Directive and the proposed Japanese EIA framework modifications could either promote or stifle further RE deployment. - Highlights: •Performs an in-depth review of EIA reforms in OECD territories •First paper to compare Japan and the European Union frameworks •Finds early-stage indicators for overall reform efficiency.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Analysis of strategic environmental assessment in Taiwan energy policy and potential for integration with life cycle assessment

Highlights: • An innovative strategic environmental assessment process integrated with life cycle assessment. • A number of shortcomings of the current SEA process were identified. • Proposals were made by which use of LCA could greatly improve SEA. Strategic environmental assessment (SEA) has been implemented in many policies in the European Union since 2001. In Taiwan, SEA has been implemented for 28 cases since 2001, which includes various types of policies. National energy policy is the most challenging type. There are three most important steps in SEA process: alternative planning, scoping, and impact assessment. However, the current limitation of method application affects the effectiveness of SEA. In this case, life cycle assessment (LCA) is integrated with SEA for clarifying the role of LCA in whole SEA process. The method of combining LCA and SEA has been developed and is applied in a case of Taiwan's energy policy. Benefits from LCA in alternative planning, scoping, and impact assessment steps are explored. Finally, suggestions for enhancing LCA's application, for scoping operation, and for the improvement of SEA are proposed.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

A proposal for assessing study quality: Biomonitoring, Environmental Epidemiology, and Short-lived Chemicals (BEES-C) instrument

The quality of exposure assessment is a major determinant of the overall quality of any environmental epidemiology study. The use of biomonitoring as a tool for assessing exposure to ubiquitous chemicals with short physiologic half-lives began relatively recently. These chemicals present several challenges, including their presence in analytical laboratories and sampling equipment, difficulty in establishing temporal order in cross-sectional studies, short- and longterm variability in exposures and biomarker concentrations, and a paucity of information on the number of measurements required for proper exposure classification. To date, the scientific community has not developed a set of systematic guidelines for designing, implementing and interpreting studies of short-lived chemicals that use biomonitoring as the exposure metric or for evaluating the quality of this type of research for WOE assessments or for peer review of grants or publications. We describe key issues that affect epidemiology studies using biomonitoring data on short-lived chemicals and propose a systematic instrument – the Biomonitoring, Environmental Epidemiology, and Short-lived Chemicals (BEES-C) instrument – for evaluating the quality of research proposals and studies that incorporate biomonitoring data on short-lived chemicals. Quality criteria for three areas considered fundamental to the evaluation of epidemiology studies that include biological measurements of short-lived chemicals are described: 1) biomarker selection and measurement, 2) study design and execution, and 3) general epidemiological study design considerations. We recognize that the development of an evaluative tool such as BEES-C is neither simple nor non-controversial. We hope and anticipate that the instrument will initiate further discussion/debate on this topic.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2015

Environmental Data Flow Six Sigma Process Improvement Savings Overview

An overview of the Environmental Data Flow Six Sigma improvement project covers LANL’s environmental data processing following receipt from the analytical laboratories. The Six Sigma project identified thirty-three process improvements, many of which focused on cutting costs or reducing the time it took to deliver data to clients.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

LANL Environmental ALARA Program Status Report for CY 2016

Los Alamos National Laboratory (LANL) ensures that radiation exposures to members of the public and the environment from LANL operations, past and present, are below regulatory thresholds and are as low as reasonably achievable (ALARA) through compliance with DOE Order 458.1 Radiation Protection for the Public and the Environment, and LANL Policy 412 Environmental Radiation Protection (LANL2016a). In 2007, a finding (RL.2-F-1) and observation (RL.2-0-1) in the NNSA/ LASO report, September 2007, Release of Property (Land) Containing Residual Radioactive Material Self-Assessment Report, indicated that LANL had no policy or documented process in place for the release of property containing residual radioactive material. In response, LANL developed PD410, Los Alamos National Laboratory Environmental ALARA Program. The most recent version of this document became effective in 2014 (LANL 2014a). The document provides program authorities, responsibilities, descriptions, processes, and thresholds for conducting qualitative and quantitative ALARA analyses for prospective and actual radiation exposures to the public and t o the environment resulting from DOE activities conducted on the LANL site.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Implementing Environmental Requirements

The purpose of this document is to describe the processes for identifying, communicating, and implementing environmental requirements at the Los Alamos National Laboratory (LANL) for Triad National Security, LLC (Triad). References to LANL or the Laboratory refer to the Department of Energy, National Nuclear Security Administration (DOE/NNSA) managed portion of LANL. References to the Prime Contract refer to the contract between DOE/NNSA and Triad and does not apply to the portion of Technical Area 54 now managed and operated by DOE Environmental Management (EM-LA).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Environmental drivers of methane fluxes from an urban temperate wetland park

Abstract Methane (CH 4 ) emissions were measured at the Wilma H. Schiermeier Olentangy River Wetland Research Park (ORWRP) over three summers and two winters using an eddy covariance system. We used an empirical model to determine the main environmental drivers of methane emissions. Methane emissions covary strongly with water vapor fluxes, CO 2 fluxes, and soil temperature. We adjust our models to account for the heterogeneous environment of the wetland by including the flux footprint distribution among different microsites as a predictive variable in the methane model. We used a forward linear stepwise model in combination with an Akaike information criteria‐based model selection process and neural network modeling to determine which environmental variables are most effective in modeling methane emissions in our site. Different models and environmental variables best represented methane fluxes in the winter and summer and also during the day or night within each season. We parameterized an optimal empirical model for methane emissions from the ORWRP that is used for gap filling of site‐level methane fluxes over 2 years. Some of the most effective variables for modeling methane were carbon, water vapor, and heat fluxes, all of which typically have the same data gaps as the time series of methane flux. In order to determine if these variables were useful for modeling methane despite the additional gap‐filling error, we determined through an error propagation experiment that eddy covariance gap‐filling models for methane may be best developed by including other gap‐filled fluxes as predictors, despite the high level of shared gaps and subsequent gap‐fill error propagation.

Morin, T. H.↗