Clean Water Act Research Articles

Relationships between land use, predicted pollution loadings, and ecotoxicological assays in constructed wetlands

Environmental degradation related to uncontrolled development resulted in the passage of the United States Clean Water Act (CWA) in 1972, with the stated purpose “to restore and maintain the integrity of the nation’s waters”. Implementation of the CWA leads to increased research to develop multimetric indicators to better measure and understand the complex patterns of ecological responses to stress occurring across levels of biological, spatial, and temporal organization. One area of research is the use of integrated indices of chemical risk, ecotoxicological risk, and ecological risk to assess the impact of human activity across disturbance gradients of urbanization. Selecting relevant metrics for constructing a multimetric index requires identifying bioindicator organisms with capacities to detect signals from anthropogenic disturbances. This study explored the potential efficacy of a suite of higher plant ecotoxicological assays for use as bioindicators in ecological risk assessment along a gradient of urbanization in a wetland ecosystem. The study was conducted in the Pike River watershed (Racine, Wisconsin, USA) in six wetlands selected across a gradient of dominant land-use types (agricultural, commercial, residential, undeveloped, and industrial). MicroBioTest PhytotoxkitTM ecotoxicological assays, based on growth inhibition of three plants (Sinapis, Sorghum, and Lepidium) were used to assess sediment toxicity. The relationships between Phytotoxkit™ responses and predicted pollutant loadings calculated from surrounding land use provided clear signals of stress from watershed pollutants draining into the wetland sites. The potential for these ecotoxicological indicators to serve as biological response signatures is strong, and further research and calibration in field and microcosms studies will assist in calibrating responses for use in integrated monitoring efforts.

Impact of upstream plant level pollution on downstream water quality: evidence from the clean water act

This is the first study to find empirical evidence that pollutant inputs from major point sources worsen downstream water quality, net of upstream pollution levels, and controlling for location-specific factors. We utilize panel data on monthly biochemical oxygen demand (BOD) concentration for a sample of 87 municipal and industrial plants located in the states of Maryland, Pennsylvania, and Virginia, for the period 1990-2003. Monthly dissolved oxygen (DO) from 67 locations is the measure of water quality. We find that an increase in aggregate BOD (for multiple plants) results in downstream net of upstream DO to decline by 0.001 mg/l. Despite the small magnitude (due to natural attenuation), the results are robust to distance traveled by pollutant and seasonal considerations of high temperature or low stream flow. We infer that point sources have a significant negative impact on ambient water quality net of non-point sources of pollution at upstream locations.

U.S. Supreme Court Issues a Major Ruling on NPDES Permits

On April 23, 2020, the United States Supreme Court issued a significant decision regarding when National Pollution Discharge Elimination System (NPDES) permits are needed for “point source” discharges under the Clean Water Act. The Clean Water Act forbids “any addition” of any pollutant from “any point source” to “navigable waters” without an appropriate permit from the United States Environmental Protection Agency (EPA). The Supreme Court’s decision stemmed from a citizens’ lawsuit filed by several environmental groups against the County of Maui, Hawaii. Maui operates a wastewater reclamation facility that collects sewage from the surrounding area, partially treats it, and pumps the treated water through four wells hundreds of feet underground. This effluent, which amounts to about four million gallons a day, then travels approximately one-half mile through groundwater to the Pacific Ocean. The environmental groups claimed that Maui has been discharging a pollutant to “navigable waters,” namely, the Pacific Ocean, without an NPDES permit required by the Clean Water Act.

Environmental Federalism in Indian Country: Sovereignty, Primacy, and Environmental Protection

Extensive research on “environmental federalism” investigates the effects of shared state‐federal implementation on policy outcomes under the landmark American environmental laws of the 1970s. But these laws originally made no mention of American Indian tribal lands, and subsequent research on environmental federalism has given them little attention. Since 1987, tribes have been eligible to assume implementation primacy under federal environmental law, similar to states. We analyze Clean Water Act (CWA) enforcement under American Indian tribal primacy compared with tribal facilities regulated directly by the U.S. government. To date, 62 tribal governments have been approved for implementation primacy under the CWA. The number and diversity of tribes operating regulated facilities provides uncommon leverage on key questions about environmental federalism. Do tribes that secure primacy enforce environmental rules more rigorously? Or does primacy allow tribes to shirk regulations in a race‐to‐the‐bottom? Analysis of CWA enforcement across 474 tribal wastewater facilities finds that, on average, enforcement increases significantly under tribal primacy. Our findings offer insights about environmental federalism, with important implications for environmental justice.

Does the Primacy System Work? State versus Federal Implementation of the Clean Water Act

AbstractIn the United States, environmental federalism largely relies on a system for policy implementation that allows the federal government to delegate primary program authority (or primacy) to state agencies. Although it is an ingrained feature of several major federal environmental policies, such as the Clean Water Act (CWA), there is little evidence to indicate what impact delegating authorities has on programs. In order to examine this, the authors use a synthetic control technique to determine how actual CWA program outcomes in five states compare to expected outcomes if EPA retained primary authority. Findings indicate that while there were no significant differences in Texas and Oklahoma, state primacy led to improved program outcomes in Florida, but worse outcomes in Maine and South Dakota. Conclusions suggest that primacy has asymmetrical impacts that largely depend on state implementation systems, which carries important implications for environmental federalism.

Mapping legal authority for terrestrial conservation corridors along streams.

Wildlife corridors aim to promote species’ persistence by connecting habitat patches across fragmented landscapes. Their implementation is limited by patterns of land ownership and complicated by differences in the jurisdictional and regulatory authorities under which lands are managed. Terrestrial corridor conservation requires coordination across jurisdictions and sectors subject to site‐specific overlapping sources of legal authority. Mapping spatial patterns of legal authority concurrent with habitat condition can illustrate opportunities to build or leverage capacity for connectivity conservation. Streamside areas provide pragmatic opportunities to leverage existing policy mechanisms for riverine and terrestrial habitat connectivity across boundaries. Conservation planners and practitioners can make use of these opportunities by harmonizing actions for multiple conservation outcomes. We formulated an integrative, data‐driven method for mapping multiple sources of legal authority weighted by capacity for coordinating terrestrial habitat conservation along streams. We generated a map of capacity to coordinate streamside corridor protections across a wildlife habitat gap to demonstrate this approach. We combined values representing coordination capacity and naturalness to generate an integrated legal‐ecological resistance map for connectivity modeling. We then computed least‐cost corridors across the integrated map, masking the terrestrial landscape to focus on streamside areas. Streamside least‐cost corridors in the integrated, local‐scale model diverged (∼25 km) from national‐scale least‐cost corridors based on naturalness. Spatial categories comparing legal‐ and naturalness‐based resistance values by stream reach highlighted potential locations for building or leveraging existing capacity through spatial coordination of policy mechanisms or restoration actions. Agencies or nongovernmental organizations intending to restore or maintain habitat connectivity across fragmented landscapes can use this approach to inform spatial prioritization and build coordination capacity. Article impact statement: Combined mapping of legal authority and habitat condition reveals capacity to coordinate actions along streams for clean water and wildlife.

Where's the Science? Recent Changes to Clean Water Act Threaten Wetlands and Thousands of Miles of Our Nation's Rivers and Streams

The vision of the U.S. government when they passed the Clean Water Act (CWA) in 1972 was to restore and maintain the chemical, physical, and biological integrity of the nation's waters to support fishing and recreation. The U.S. Environmental Protection Agency and Army Corps of Engineers have recently made major and controversial changes to the CWA in a 2020 regulation referred to as the Navigable Waters Protection Rule. This article reviews the bipartisan history of the CWA and the historic trajectory of how “waters of the United States” are defined to provide legal jurisdiction. It then discusses the science that supported changes to the CWA made in 2015 and lack of science that supported recent changes. The 2015 Clean Water Rule was intended to be a science-based clarification of what “waters of the United States” mean to CWA regulation. That rule was based on synthesis and review of >1,200 peer-reviewed articles that served as the basis for a 408-page scientific Connectivity Report. For the recently released regulation, U.S. Environmental Protection Agency's (EPA's) Science Advisory Board wrote that EPA did not incorporate the best-available science into the rule making process and provided no “comparable body of peer-reviewed evidence” to support the proposed changes to the CWA. Furthermore, the EPA ignored science by even stating that “science cannot dictate where to draw the line between Federal and State waters.” EPA's mission is to protect human and environmental health, the Corps has a vision of “engineering solutions for our Nation's toughest challenges.” Ultimately, the EPA and the Corps have ignored their responsibilities, mission, and vision by ignoring well-established science in their mandates to protect our nation's water for current and future generations.

Isotopic and element ratios fingerprint salinization impact from beneficial use of oil and gas produced water in the Western U.S.

Salinization of global freshwater resources is a concerning health and economic issue of the 21st century and requires serious management and study to understand how, and by what mechanism, Total Dissolved Solids (TDS) is changing in major watersheds. Oil and gas (O&G) produced water is a complex and saline (10-300g/L TDS) wastewater often disposed to surface waters post-treatment. However, in western U.S. states, beneficial use of minimally treated O&G produced water discharged to ephemeral streams is permitted through the USEPA National Pollutant Discharge Elimination System (NPDES) for agriculture and wildlife propagation. In a remote Wyoming study region, beneficial use of O&G NPDES effluents annually contributes 13billionL of water to surface water resources. The primary O&G TDS constituents are sulfate and sodium followed by chloride and calcium. Significant TDS increases from 2013 to 2016 in a large perennial river (River C) impacted by O&G effluent disposal, slight TDS increases in a perennial river (River B) and chronically elevated TDS (upwards of 2500mg/L) in a smaller tributary (Tributary A) comprised mainly of O&G effluents led to an investigation of O&G impacts to surface waters in the region. Chloride-normalized metal ratios such as Br/Cl and δ2H and δ18O distinguished evaporation as the mechanism for increasing TDS derived from O&G on Tributary A, which is causing O&G effluents that meet NPDES regulations to not only exceed outfall regulations downstream where it is beneficially used for irrigation and drinking water but also exceed aquatic life and livestock recommended limits. 87Sr/86Sr and δ34SSO4 suggested minor impacts from O&G TDS loading on River C but also support an additional salinity source, such as streambed geological controls, the cause of significantly increasing TDS. While lithium isotopes provided insight into the O&G effluent origin (δ7Li ranged 9-10‰) and water-sediment interactions along O&G effluent streams, they did not function as distinct salinity tracers in the larger downstream rivers. This study suggests a multi-isotope (87Sr/86Sr and δ34SSO4) approach is often necessary for fingerprinting salinization sources and determining best management practices because multiple salinity sources and environmental mechanisms may need to be identified to protect water quality.

Mutagenicity assessment downstream of oil and gas produced water discharges intended for agricultural beneficial reuse.

Produced water is the largest waste stream associated with oil and gas operations. This complex fluid contains petroleum hydrocarbons, heavy metals, salts, naturally occurring radioactive materials and any remaining chemical additives. In the United States, west of the 98th meridian, the federal National Pollutant Discharge Elimination System (NPDES) exemption allows release of produced water for agricultural beneficial reuse. The goal of this study was to quantify mutagenicity of a produced water NPDES release and discharge stream. We used four mutation assays in budding yeast cells that provide rate estimates for copy number variation (CNV) duplications and deletions, as well as forward and reversion point mutations. Higher mutation rates were observed at the discharge and decreased with distance downstream, which correlated with the concentrations of known carcinogens detected in the stream (e.g., benzene, radium), described in a companion study. Mutation rate increases were most prominent for CNV duplications and were higher than mutations observed in mixtures of known toxic compounds. Additionally, the samples were evaluated for acute toxicity in Daphnia magna and developmental toxicity in zebrafish. Acute toxicity was minimal, and no developmental toxicity was observed. This study illustrates that chemical analysis alone (McLaughlin et al., 2020) is insufficient for characterizing the risk of produced water NPDES releases and that a thorough evaluation of chronic toxicity is necessary to fully assess produced water for beneficial reuse.

Water quality assessment downstream of oil and gas produced water discharges intended for beneficial reuse in arid regions

Produced water (PW) is the largest waste stream associated with oil and gas extraction and contains organics, salts, metals and radioactive materials. In the United States, west of the 98th meridian, the National Pollutant Discharge Elimination System exemption allows for release of PW to surface waters for agricultural beneficial reuse if it is “of good enough quality”. Due to the complex and variable composition of PW, the downstream impacts of these releases are not fully understood. In this study, a detailed chemical analysis was conducted on a stream composed of PW released for agricultural beneficial reuse. Over 50 geogenic and anthropogenic organic chemicals not specified in the effluent limits were detected at the discharge including hydrocarbons, halogenated compounds, and surfactants. Most were removed within 15 km of the discharge due to volatilization, biodegradation, and sorption to sediment. Inorganics detected at the discharge were within regulatory effluent limits. While some inorganic species (i.e., strontium, barium and radium) decreased in concentration downstream due to co-precipitation, concentrations of many inorganic species including sodium, sulfate and boron increased due to water evaporation. Consequently, downstream water quality changes need to be considered to adequately evaluate the potential impact of discharged PW. Regulatory health thresholds for humans, livestock, and aquatic species for most chemical species present at the discharge are still lacking. As a result, toxicity tests are necessary to determine the potential health impacts to downstream users.

Knowledge Exchange and Social Capital for Freshwater Ecosystem Assessments

Abstract The 1972 Clean Water Act (CWA) provided crucial environmental protections, spurring research and corresponding development of a network of expertise that represents critical human capital in freshwater conservation. We used social network analysis to evaluate collaboration across organizational types and ecosystem focus by examining connections between authors of freshwater assessments published since the CWA. We found that the freshwater assessment network is highly fragmented, with no trend toward centralization. Persistent cohesion around organizational subgroups and minimal bridging ties suggest the network is better positioned for diversification and innovation than for learning and building a strong history of linked expertise. Despite an abundance of research activity from university-affiliated authors, federal agency authors provide a majority of the bonding and bridging capital, and diverse agencies constitute the core network. Together, our results suggest that government agencies currently play a central role in sustaining the network of expertise in freshwater assessment, protection, and conservation.

A Bridge to Nowhere? Our Energy Transition and the Natural Gas Pipeline Wars

This article chronicles how natural gas has replaced coal as today’s energy dilemma. The pipeline wars illustrate landowners’ concern with special treatment for industry seeking to condemn lands, while some states and the public object to the Federal Energy Regulatory Commission’s (FERC or Commission) approach to approving new pipeline projects, or the Commission’s assessment of GHG emissions associated with project development. Part II examines the pipeline wars in their historical context, portraying the rise of natural gas regulation, its increasing dominance as a fuel source, its associated environmental consequences, and the marked differences in how the Obama and Trump administrations have treated natural gas. Part III describes and analyzes three principal matters collectively displaying the challenges confronting the industry: (1) the Commission’s approach toward conditionally approving pipelines before states can ensure construction activities will comply with the Clean Water Act (CWA); (2) the Commission’s willingness to allow pipeline condemnation proceedings to occur before landowners have an opportunity to thoroughly air their concerns; and (3) FERC’s unwillingness to examine the indirect upstream and downstream effects from increased GHG emissions associated with approving a pipeline. This Part also discusses FERC’s 2018 Notice of Inquiry, soliciting input on the Commission’s pipeline policies. Next, Part IV addresses the principal, looming questions in the pipeline wars: whether and how the Commission ought to reexamine the need for new natural gas pipeline infrastructure. Major energy transitions present major challenges, and the resultant follies from these efforts abound. If we fail to avoid yet another folly, our new natural gas infrastructure could become either a shackle, impeding a zero-carbon energy future, or a bridge to nowhere.

Water Pollutants Discharge Permit Systems of the United States and China: A Comparison Using Referential Method

Using a referential method, a comparative study is carried out on the USA Clean Water Act (CWA) and the PRC Water Pollution Prevention and Control Law (WPPCL). Both laws employ a discharge permit system to achieve their respective environmental goals. The focus of the study is on the comparison of the CWA/National Pollutants Discharge Elimination System and the WPPCL/Water Pollution Discharge Permit system. It is first pointed out that the comparison of environmental laws is not a “better-law comparison”. Instead, an environmental law in one country may be used as reference to examine how an environmental law in another country can be developed and implemented within the respective legal framework. Comparison between the USA CWA/NPDES and the PRC WPPCL/WPDP is made from the perspectives of law objectives, implementation procedures and enforcement actions. Several recommendations are then made to better design and implement the permit system in China, with respect to ethical premise, concrete law, discharge standards and enforcement.

An Intensive Cultural Resources Investigation for the Redbud Pump Station Transmission Water Line Project Collin County, Texas

The City of McKinney (City) is proposing to construct and maintain 2.2 kilometers (km; 1.4 miles [mi]) of 42- inch (in) water transmission line for the Redbud Pump Station Transmission Water Line Project (Project) located within the City of McKinney, in west-central Collin County, Texas (Appendix A, Figure 1). On behalf of the City, BGE, Inc. (BGE) conducted an intensive pedestrian survey augmented by shovel testing of the Project. Because the proposed project is being contracted by the City of McKinney, a political subdivision of the state of Texas, the project sponsor is required under the Texas Antiquities Code and the Texas Natural Resources Code Chapter 26 ‘Rules of Practice and Procedure for the Antiquities Code of Texas’ to obtain a Texas Antiquities Permit to perform cultural resources investigations to assess whether cultural resources are present that may rise to the level of significance of State Antiquities Landmark (SAL) status. The Texas Historical Commission (THC) has assigned Antiquities Permit number 8763 to the Project. Furthermore, project construction designs minimize impacts to Waters of the United States (WOTUS) crossed by the project, not meeting the minimum threshhold established under Section 404 of the Clean Water Act (CWA) for the requirement of a Pre-Construction Notification (PCN) to the United States Army Corps of Engineers (USACE).

Atomizing the Clean Water Act: Ignoring the Whole Statute and Asking the Wrong Questions

When attempting to resolve difficult issues of statutory construction involving complex statutes, courts sometimes focus on individual words and phrases without evaluating how they fit within the text and structure of the whole statute. We call this “atomization” of the statutory text. Judges have fallen into this trap in construing the Clean Water Act (CWA) and other lengthy, complex federal environmental statutes. That tendency contributes to ongoing confusion about the scope and coverage of the CWA. During the 2019-2020 Term, the U.S. Supreme Court will resolve a circuit split in the most recent line of cases exhibiting this tendency. Courts have struggled to ascertain the scope of CWA permitting jurisdiction when pollutants reach water bodies through an intermediary conduit such as groundwater. Some courts have “atomized” that analysis, leading to further analytical confusion. Evaluating this issue in light of the functions CWA permits serve in the whole statutory scheme leads to more logical results. The “conduit” cases thus serve as a good example of the perils of atomization, and how it can be avoided through a whole text analysis. That method, in turn, can allow courts to avoid altogether separate debates about the relevance of legislative history and other non-textual indicia of congressional purpose in statutory construction.

Application of the Clean Water Act to Groundwater Is Anathema to the Water Industry: An Unfolding Tale

Key TakeawaysAmendments to the Clean Water Act (CWA) and the definition of “waters of the United States” have evolved over time.US courts have differed on whether the CWA regulates groundwater discharges.Water projects could become too costly, too burdensome, and subject to delays if the Supreme Court decides that the CWA regulates groundwater.

Engaging Colonial Entanglements: “Treatment as a State” Policy for Indigenous Water Co-Governance

In the United States, treatment as a state (TAS) provisions enable eligible Native American tribes to assume the same responsibilities as state governments in setting and implementing water quality standards (WQSs). Following the introduction of TAS through 1987 amendments to the US Clean Water Act (CWA), forty-four US tribes have enacted TAS tribal standards, which may be more stringent than those of neighboring states; can incorporate cultural and/or ceremonial uses; and can be used to influence pollution levels coming from upstream, off-reservation users. To evaluate TAS as a model for Indigenous water co-governance, we examine how Native American tribes are advancing tribal sovereignty and environmental sustainability through TAS, and we engage with conflicting views on whether and how Indigenous self-determination can be advanced through existing bureaucratic and colonial governance systems. We specifically analyze environmental pollutant listings in tribal water quality standards for the forty-four TAS tribes. Findings suggest that TAS tribes are creating more culturally relevant WQSs, which are typically as comprehensive as, and often more stringent than, analogous state regulations. Tribal standards are diverse, and TAS tribes can set standards independently from neighboring states and one another. Further analysis reveals the complexities of TAS policy, whereby colonial entanglements both enable and constrain enhanced Indigenous self-determination.

Biological Status Assessment of Coral Reefs in Southern Puerto Rico: Supporting Coral Reef Protection Under the U.S. Clean Water Act

States and other jurisdictions may protect coral reefs using biological water quality standards outlined by the United States Clean Water Act (CWA). Such protection will require long-term, regional monitoring of the resource using biological indicators and a probability-based sampling design. A 60-station survey targeting nearshore linear coral reef was conducted across southern Puerto Rico in December 2011 to document the status of reef inhabitants using a probabilistic, regional sampling design. The quantity, type and condition of stony corals, fish, gorgonians, and sponges were documented from each station, providing a robust representation of linear reef status and composition across the region. Fish represented 106 unique taxa and stony corals 32 unique taxa. Benthic organisms (stony corals, sponges, and gorgonians) averaged nearly 12 colonies per square meter, more than half of which were gorgonians. Assessment results can be used as a baseline to compare with future regional surveys to quantify change in reef condition over time (trend). Both temporal and spatial changes can be expected after large-scale disturbances like hurricanes Maria and Irma in 2017. The indicators and probabilistic sampling design support the long-term regional monitoring envisioned by the Environmental Protection Agency to implement CWA protections in Puerto Rico and elsewhere.

Assessment of the contribution of utility vault water to surface water pollution

Utility vaults and underground structures house essential telecommunications, gas, and electrical infrastructure (e.g., transformers, copper wiring) that could contaminate water which accumulates in them. Water is removed from utility vaults during routine infrastructure maintenance. That water is typically released to the storm drain system, raising concerns that polluted water could reach receiving waters. However, no one has measured pollutants in utility vault water. The State Water Resources Control Board (SWRCB) has mandated such measurements as a condition of renewing the National Pollutant Discharge Elimination System Utility Vault Permit. We analyzed 126 priority pollutants in 20 utility vault water samples collected throughout California by Pacific Gas and Electric Company (PG&E). We also estimated the volume of utility vault water discharged and calculated loads. Twenty-one priority pollutants were detected. Metals were commonly found. Only copper (Cu) and zinc (Zn) exceeded water quality criteria. Their maximum concentrations were 791 and 386 μg/L, respectively. Median Cu and Zn concentrations of 9.66 and 81.6 μg/L were representative of urban stormwater, suggesting runoff is a source of metals in utility vault water. For San Francisco Bay, Cu and Zn loads from PG&E's utility vault water (0.06 and 0.5 kg/year) were inconsequential compared to previously reported total loads (74,000 and 320,000 kg/year) from stormwater, wastewater treatment plants, etc. For California, utility vault water loads were 5 and 40 kg/year of Cu and Zn. We are the first to report pollutant concentrations in utility vault water. Utility vaults are not a major source of pollutants to receiving waters.

The proposed change to the definition of “waters of the United States” flouts sound science

The U.S. Environmental Protection Agency (EPA) and Army Corps of Engineers (hereafter, “the agencies”) have issued a proposed rule (1) that would remove Clean Water Act (CWA) protections from more than half of wetlands and one-fifth of streams in the United States (2). This move sharply contrasts with reports indicating that US waters remain threatened by storms, droughts, contaminants, algal blooms, and other stressors. Even the EPA’s National Water Quality Inventory detected poor conditions in 46% of stream and river miles and 32% of wetlands (3). In short, the proposed rule does not reflect the best-available science and, if enacted, will damage our nation’s water resources. A proposed rule under consideration by the US federal government does not reflect the best-available science and, if enacted, will damage the nation’s water resources. Image credit: Shutterstock/Martha Marks. Despite the CWA’s mandate “to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters” (4), controversy persists over jurisdiction. For decades, the protected “waters of the United States” (WOTUS) included traditionally navigable waters (TNWs), such as large rivers, lakes, and territorial seas, as well as waters meaningfully connected to or affecting the integrity of TNWs. Operationalizing this connection has become a flashpoint for the science and politics of water protection. Connectivity among waterbodies was the cornerstone of the Obama administration’s Clean Water Rule (CWR), which reflected a state-of-the-science synthesis of more than 1,200 scientific publications [known as the “Connectivity Report” (5)], input from 49 experts, and a rigorous review by a 25-member panel of the EPA’s Scientific Advisory Board (SAB) (6). Since then, scientific evidence supporting the 2015 CWR, and hence contradicting the new proposal, has only accumulated, especially as related intermittent (i.e., flow seasonally) and ephemeral (i.e., flow periodically, after precipitation events) streams, riparian and floodplain zones, and non-floodplain wetlands … [↵][1]1To whom correspondence may be addressed. Email: sullivan.191{at}osu.edu. [1]: #xref-corresp-1-1