Monitoring fish contaminant responses to abatement actions: factors that affect recovery

Variation in natural attenuation rates of polychlorinated biphenyls (PCBs) in fish from streams and reservoirs in East Tennessee observed over a 35-year period

Environmental contamination due to human activities is a major concern, particularly for persistent chemicals. Within catchments, persistent chemicals linked to negative health outcomes such as polychlorinated biphenyls (PCBs) have great potential to be transported, through adsorption or biological uptake, with downstream locations acting as sinks for accumulation. Here we present long-term trends in PCB bioaccumulation in fish found in lower-order tributaries on the Oak Ridge Reservation, an impacted US Department of Energy property in East Tennessee, USA, and a large reservoir system adjacent to it composed of parts of the Clinch and Tennessee Rivers. Given that the reservoir system has experienced no direct PCB mitigation activities, this record offers an opportunity to explore potential natural attenuation of PCBs within a large lotic ecosystem. Attenuation rates ranged from 0% to 8% yr^-1 in minnows and sunfish at stream sites and 5.4-11.3% yr^-1 in catfish at reservoir sites. These rates are comparable to findings from similar studies in other regions, suggesting a consistency in responses since the banning of PCB production in 1979. Further, results suggest that PCB sources from discharge outfalls are important locally but are not primarily responsible for sustaining PCB contamination in downstream reservoirs.

Integrated watershed process model for evaluating mercury sources, transport, and future remediation scenarios in an industrially contaminated site

We used the Soil Water Assessment Tool (SWAT) as a framework to develop an empirical Hg flux model for Upper East Fork Poplar Creek (UEFPC), a Hg-contaminated watershed in Oak Ridge, Tennessee. By integrating long-term Hg monitoring data with simulated flow and suspended solid loads in a site-specific empirical Hg transport model, we (1) quantified the spatial, temporal, and flow regime controls on daily Hg flux (adjusted R² = 0.82) and (2) made predictions about Hg flux under future climate, land use, and management scenarios. We found that 62.79% of the average daily Hg flux in the watershed is currently driven by base flow, whereas variability in Hg flux is driven by storm and extreme flow. We estimate an average annual Hg flux of 28.82 g day^-1 leaving the watershed under baseline precipitation, with an estimated 43.73% reduction in daily Hg flux under drought conditions and a 296% increase in daily Hg flux in extreme precipitation scenarios. We estimated that a new mercury treatment facility would result in a 24.7% reduction in Hg flux under baseline conditions and a 33.4% reduction under extreme precipitation scenarios. The study demonstrated the merit of this approach, which can be replicated for sites where information on flow, suspended solids, and Hg concentrations is available.

Publishing Environmental Assessment and Management Science: Crossing the Hurdles

Benefits accrue to scientists, resource managers, companies, and policymakers when environmental scientists publish in peer-reviewed journals. However, environmental scientists and practitioners face challenges, including the sometimes low value placed on journal articles, institutional vested interests in outcomes, and the changing priorities of employers and project sponsors. Confidentiality agreements can also lead scientists to assume publication is not an option. Case studies may be viewed by potential authors as too routine for peer-reviewed journals. On the basis of 30 years of experience, we suggest that publishing hurdles can be overcome and that environmental scientists have a range of options. The topics of manuscripts can include not only results from case studies and perspectives based on them but also byproducts of assessments, including definitions, plans, monitoring methods and models, and decision frameworks. Environmental scientists have unique opportunities to move science forward with their practical knowledge if they can move across the institutional, logistical, data-related, and content-related hurdles.

Seasonal and flow-driven dynamics of particulate and dissolved mercury and methylmercury in a stream impacted by an industrial mercury source

Sediments and floodplain soils in the East Fork Poplar Creek watershed (Oak Ridge, TN, USA) are contaminated with high levels of mercury (Hg) from an industrial source at the headwaters. Although baseflow conditions have been monitored, concentrations of Hg and methylmercury (MeHg) during high-flow storm events, when the stream is more hydrologically connected to the floodplain, have yet to be assessed. The present study evaluated baseflow and event-driven Hg and MeHg dynamics in East Fork Poplar Creek, 5 km upstream of the confluence with Poplar Creek, to determine the importance of hydrology to in-stream concentrations and downstream loads and to ascertain whether the dynamics are comparable to those of systems without an industrial Hg source. Particulate Hg and MeHg were positively correlated with discharge (r(2)  = 0.64 and 0.58, respectively) and total suspended sediment (r(2)  = 0.97 and 0.89, respectively), and dissolved Hg also increased with increasing flow (r(2)  = 0.18) and was associated with increases in dissolved organic carbon (r(2)  = 0.65), similar to the dynamics observed in uncontaminated systems. Dissolved MeHg decreased with increases in discharge (r(2)  = 0.23) and was not related to dissolved organic carbon concentrations (p = 0.56), dynamics comparable to relatively uncontaminated watersheds with a small percentage of wetlands (<10%). Although stormflows exert a dominant control on particulate Hg, particulate MeHg, and dissolved Hg concentrations and loads, baseflows were associated with the highest dissolved MeHg concentration (0.38 ng/L) and represented the majority of the annual dissolved MeHg load. Environ Toxicol Chem 2016;35:1386-1400. Published 2015 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US Government work, and as such, is in the public domain in the United States of America.

Interpretation of the source-specific substantive control measures of the Minamata Convention on Mercury

Being persistent, toxic, and bio-accumulative, Mercury (Hg) seriously affects the environment and human health. Due to Hg's attribute of long-range environmental transport across national borders, especially through atmospheric transport, no country can fully protect its environment and human health with its own efforts, without global cooperation. The Minamata Convention on Mercury, which was formally adopted and opened for signature in October 2013, is the only global environmental regime on the control of Hg pollution. Its main substantive control measures are source-specific: its phasing-out, phasing-down, and other main substantive requirements all direct to specific categories of pollution sources through the regulation of specific sectors of the economy and social life. This Convention does not take a national quota approach to quantify the Parties' nationwide total allowable consumption or discharge of Hg or Hg compounds, nor does it quantify their nationwide total reduction requirements. This paper attempts to find the underlying reasons for this source-specific approach and offers two interpretations. One possible interpretation is that Hg might be a non-threshold pollutant, i.e., a pollutant without a risk-free value of concentration. The existence of a reference dose (RfD), reference concentration (RfC), provisional tolerable weekly intake (PTWI), minimal risk level (MRL) or other similar reference values of Hg does not necessarily mean that Hg cannot be regarded as non-threshold because such reference values have scientific uncertainties and may also involve policy considerations. Another interpretation is that Hg lacks a feasibly determinable total allowable quantity. There is evidence that negotiators might have treated Hg as non-threshold, or at least accepted that Hg lacks a feasibly determinable total allowable quantity: (1) The negotiators were informed about the serious situations of the current emissions, releases, and legacy deposition; (2) the UNEP Secretariat took the position that Hg is non-threshold and should be eliminated to the maximum; (3) European countries, the USA and other western countries were in a better position to regard Hg as non-threshold and push forward a global reduction of Hg emissions and releases to the minimum; (4) the negotiators took the Stockholm Convention on Persistent Organic Pollutants (POPs) as a model; and (5) a fairly large number of non-governmental organizations (NGOs) were organized under umbrella NGO networks such as the Zero Mercury Working Group (ZMWG) and the International POPs Elimination Network (IPEN) and made a significant contribution to the negotiation process. The interpretations for the Minamata Convention might similarly be used to interpret the source-specific approach of the Stockholm Convention on POPs and the national quota approach of global environmental regimes on stratospheric ozone and climate mitigation. These two interpretations focus on the features of the pollutants and for this reason may be useful for future negotiators of other international environmental treaties to select appropriate models. They also suggest that the source-specific approach may be adopted in the future for pollutants with similar features of being possibly non-threshold and without a feasibly determinable total allowable quantity.

Sources of mercury in a contaminated stream--implications for the timescale of recovery

Mercury contamination in East Fork Poplar Creek in Tennessee arises from dissolved mercury exiting a headwater industrial complex and residual mercury in the streambed and soil throughout the watershed downstream. The headwater inputs generate chronic base flow concentrations of total mercury of about 1,000 ng/L, but most of the annual export of mercury from the system appears to originate farther downstream. Effective targeting of remedial efforts requires determining how long downstream sources might continue to contaminate the system following elimination of the headwater mercury inputs. The authors calculations suggest that (1) contaminated soils and sediments account for >80% of the annual mercury export from the entire watershed, with most export occurring during wet weather events; (2) bank erosion and resuspension of streambed particulates are the major mercury sources maintaining high annual mercury export rates; and (3) the inventory of particle-associated mercury in the streambed was not large enough to sustain the estimated export rates for more than a few years. The authors findings imply that to prevent waterborne mercury contamination in this system from continuing for decades, remedial actions will have to control the headwater mercury source that sustains day-to-day base flow mercury concentrations and the riparian stream-bank sources that generate most of the mercury export from the system.

Decreasing aqueous mercury concentrations to meet the water quality criterion in fish: examining the water-fish relationship in two point-source contaminated streams

East Fork Poplar Creek (EF) and White Oak Creek (WC) are two mercury-contaminated streams located on the United States (U.S.) Department of Energy Oak Ridge Reservation in East Tennessee. East Fork Poplar Creek is the larger and more contaminated of the two, with average aqueous mercury (Hg) concentrations exceeding those in reference streams by several hundred-fold. Remedial actions over the past 20 years have decreased aqueous Hg concentrations in EF by 85% (from >1600 ng/L to <400 ng/L). Fish fillet concentrations, however, have not responded to this decrease in aqueous Hg and remain above the U.S. Environmental Protection Agency National Recommended Water Quality Criteria (NRWQC) of 0.3 mg/kg. The lack of correlation between aqueous and fish tissue Hg concentrations in this creek has led to questions regarding the usefulness of target aqueous Hg concentrations and strategies for future remediation efforts. White Oak Creek has a similar contamination history but aqueous Hg concentrations in WC are an order of magnitude lower than in EF. Despite the lower aqueous Hg concentrations (<100 ng/L), fish fillet concentrations in WC have also been above the NRWQC, making the aqueous Hg remediation goal of 200 ng/L in EF seem unlikely to result in an effective decrease in fillet Hg concentrations. Recent monitoring efforts in WC, however, suggest an aqueous total Hg threshold above which Hg bioaccumulation in fish may not respond. This new information could be useful in guiding remedial actions in EF and in other point-source contaminated streams.

Selenium:mercury molar ratios in freshwater fish from Tennessee: individual, species, and geographical variations have implications for management

Vertebrates, including humans, can experience adverse effects from mercury consumed in fish. Humans often prefer large predatory fish that bioaccumulate high mercury levels. Recent attention has focused on the role of selenium countering mercury toxicity, but there is little research on the selenium:mercury molar ratios in freshwater fish. We examine selenium:mercury molar ratios in freshwater fish from Tennessee at Poplar Creek which receives ongoing inputs of mercury from the Department of Energy's Oak Ridge Y-12 facility. Our objective was to determine variation of the ratios within species that might affect the protectiveness of selenium against mercury toxicity. Within species, the ratio was correlated significantly and positively with fish length only for two species. There was great individual variation in the selenium:mercury molar ratio within each species, except striped bass. The lack of a clear relationship between the selenium:mercury molar ratio and fish length, and the intraspecific variation, suggests that it would be difficult to use the molar ratio in predicting either the risk from mercury toxicity or in devising consumption advisories.

Importance of data management in a long-term biological monitoring program

The long-term Biological Monitoring and Abatement Program (BMAP) has always needed to collect and retain high-quality data on which to base its assessments of ecological status of streams and their recovery after remediation. Its formal quality assurance, data processing, and data management components all contribute to meeting this need. The Quality Assurance Program comprehensively addresses requirements from various institutions, funders, and regulators, and includes a data management component. Centralized data management began a few years into the program when an existing relational database was adapted and extended to handle biological data. The database's main data tables and several key reference tables are described. One of the most important related activities supporting long-term analyses was the establishing of standards for sampling site names, taxonomic identification, flagging, and other components. The implemented relational database supports the transmittal of data to the Oak Ridge Environmental Information System (OREIS) as the permanent repository. We also discuss some limitations to our implementation. Some types of program data were not easily accommodated in the central systems, and many possible data-sharing and integration options are not easily accessible to investigators. From our experience we offer data management advice to other biologically oriented long-term environmental sampling and analysis programs.

Long-term water-quality changes in East Fork Poplar Creek, Tennessee: background, trends, and potential biological consequences

We review long-term changes that have occurred in factors affecting water quality in East Fork Poplar Creek (EFPC; in East Tennessee) over a nearly 25-year monitoring period. Historically, the stream has received wastewaters and pollutants from a major United States Department of Energy (DOE) facility on the headwaters of the stream. Early in the monitoring program, EFPC was perturbed chemically, especially within its headwaters; evidence of this perturbation extended downstream for many kilometers. The magnitude of this perturbation, and the concentrations of many biologically significant water-quality factors, has lessened substantially through time. The changes in water-quality factors resulted from a large number of operational changes and remedial actions implemented at the DOE facility. Chief among these were consolidation and elimination of many effluents, elimination of an unlined settling/flow equalization basin, reduction in amount of blow-down from cooling tower operations, dechlorination of effluents, and implementation of flow augmentation. Although many water-quality characteristics in upper EFPC have become more similar to those of reference streams, conditions remain far from pristine. Nutrient enrichment may be one of the more challenging problems remaining before further biological improvements occur.

Long-term biological monitoring of an impaired stream: synthesis and environmental management implications

The long-term ecological recovery of an impaired stream in response to an industrial facility's pollution abatement actions and the implications of the biological monitoring effort to environmental management is the subject of this special issue of Environmental Management. This final article focuses on the synthesis of the biological monitoring program's components and methods, the efficacy of various biological monitoring techniques to environmental management, and the lessons learned from the program that might be applicable to the design and application of other programs. The focus of the 25-year program has been on East Fork Poplar Creek, an ecologically impaired stream in Oak Ridge, Tennessee with varied and complex stressors from a Department of Energy facility in its headwaters. Major components of the long-term program included testing and monitoring of invertebrate and fish toxicity, bioindicators of fish health, fish contaminant accumulation, and instream communities (including periphyton, benthic macroinvertebrate, and fish). Key parallel components of the program include water chemistry sampling and data management. Multiple lines of evidence suggested positive ecological responses during three major pollution abatement periods. Based on this case study and the related literature, effective environmental management of impaired streams starts with program design that is consistent across space and time, but also adaptable to changing conditions. The biological monitoring approaches used for the program provided a strong basis for assessments of recovery from remedial actions, and the likely causes of impairment. This case study provides a unique application of multidisciplinary and quantitative techniques to address multiple and complex regulatory and programmatic goals, environmental stressors, and remedial actions.

Long-term benthic macroinvertebrate community monitoring to assess pollution abatement effectiveness

The benthic macroinvertebrate community of East Fork Poplar Creek (EFPC) in East Tennessee was monitored for 18 years to evaluate the effectiveness of a water pollution control program implemented at a major United States (U.S.) Department of Energy facility. Several actions were implemented to reduce and control releases of pollutants into the headwaters of the stream. Four of the most significant actions were implemented during different time periods, which allowed assessment of each action. Macroinvertebrate samples were collected annually in April from three locations in EFPC (EFK24, EFK23, and EFK14) and two nearby reference streams from 1986 through 2003. Significant improvements occurred in the macroinvertebrate community at the headwater sites (EFK24 and EFK23) after implementation of each action, while changes detected 9 km further downstream (EFK14) could not be clearly attributed to any of the actions. Because the stream was impacted at its origin, invertebrate recolonization was primarily limited to aerial immigration, thus, recovery has been slow. As recovery progressed, abundances of small pollution-tolerant taxa (e.g., Orthocladiinae chironomids) decreased and longer lived taxa colonized (e.g., hydropsychid caddisflies, riffle beetles, Baetis). While assessments lasting three to four years may be long enough to detect a response to new pollution controls at highly impacted locations, more time may be needed to understand the full effects. Studies on the effectiveness of pollution controls can be improved if impacted and reference sites are selected to maximize spatial and temporal trending, and if a multidisciplinary approach is used to broadly assess environmental responses (e.g., water quality trends, invertebrate and fish community assessments, toxicity testing, etc.).

Role of a comprehensive toxicity assessment and monitoring program in the management and ecological recovery of a wastewater receiving stream

National Pollution Discharge Elimination Permit (NPDES)-driven effluent toxicity tests using Ceriodaphnia dubia and fathead minnows were conducted for more than 20 years to assess and monitor the effects of wastewaters at the United States (U.S.) Department of Energy Y-12 National Security Complex (Y-12 Complex) in Oak Ridge, Tennessee. Toxicity testing was also conducted on water samples from East Fork Poplar Creek (EFPC), the wastewater receiving stream, as part of a comprehensive biological monitoring and assessment program. In this paper, we evaluate the roles of this long-term toxicity assessment and monitoring program in the management and ecological recovery of EFPC. Effluent toxicity testing, associated toxicant evaluation studies, and ambient toxicity monitoring were instrumental in identifying toxicant sources at the Y-12 Complex, guiding modifications to wastewater treatment procedures, and assessing the success of various pollution-abatement actions. The elimination of untreated wastewater discharges, the dechlorination of remaining wastewater streams, and the implementation of flow management at the stream headwaters were the primary actions associated with significant reductions in the toxicity of stream water in the upper reaches of EFPC from the late 1980s through mid 1990s. Through time, as regulatory requirements changed and water quality improved, emphasis shifted from comprehensive toxicity assessments to more focused toxicity monitoring efforts. Ambient toxicity testing with C. dubia and fathead minnows was supplemented with less-standardized but more sensitive alternative laboratory toxicity tests and in situ bioassays. The Y-12 Complex biological monitoring experience demonstrates the value of toxicity studies to the management of a wastewater receiving stream.

Introduction to the biological monitoring and abatement program

This paper provides an introduction to a long-term biological monitoring program and the Environmental Management special issue titled Long-term Biological Monitoring of an Impaired Stream: Implications for Environmental Management. The Biological Monitoring and Abatement Program, or BMAP, was implemented to assess biological impairment downstream of U.S. Department of Energy (DOE) facilities in Oak Ridge, Tennessee, beginning in 1985. Several of the unique aspects of the program include its long-term consistent sampling, a focus on evaluating the effectiveness of specific facility abatement and remedial actions, and the use of quantitative sampling protocols using a multidisciplinary approach. This paper describes the need and importance of long-term watershed-based biological monitoring strategies, in particular for addressing long-term stewardship goals at DOE sites, and provides a summary of the BMAP's objectives, spatial and temporal extent, and overall focus. The primary components of the biological monitoring program for East Fork Poplar Creek in Oak Ridge, Tennessee are introduced, as are the additional 9 papers in this Environmental Management special issue.

Twenty-five years of ecological recovery of East Fork Poplar Creek: review of environmental problems and remedial actions

In May 1985, a National Pollutant Discharge Elimination System permit was issued for the Department of Energy's Y-12 National Security Complex (Y-12 Complex) in Oak Ridge, Tennessee, USA, allowing discharge of effluents to East Fork Poplar Creek (EFPC). The effluents ranged from large volumes of chlorinated once-through cooling water and cooling tower blow-down to smaller discharges of treated and untreated process wastewaters, which contained a mixture of heavy metals, organics, and nutrients, especially nitrates. As a condition of the permit, a Biological Monitoring and Abatement Program (BMAP) was developed to meet two major objectives: demonstrate that the established effluent limitations were protecting the classified uses of EFPC, and document the ecological effects resulting from implementing a Water Pollution Control Program at the Y-12 Complex. The second objective is the primary focus of the other papers in this special series. This paper provides a history of pollution and the remedial actions that were implemented; describes the geographic setting of the study area; and characterizes the physicochemical attributes of the sampling sites, including changes in stream flow and temperature that occurred during implementation of the BMAP. Most of the actions taken under the Water Pollution Control Program were completed between 1986 and 1998, with as many as four years elapsing between some of the most significant actions. The Water Pollution Control Program included constructing nine new wastewater treatment facilities and implementation of several other pollution-reducing measures, such as a best management practices plan; area-source pollution control management; and various spill-prevention projects. Many of the major actions had readily discernable effects on the chemical and physical conditions of EFPC. As controls on effluents entering the stream were implemented, pollutant concentrations generally declined and, at least initially, the volume of water discharged from the Y-12 Complex declined. This reduction in discharge was of ecological concern and led to implementation of a flow management program for EFPC. Implementing flow management, in turn, led to substantial changes in chemical and physical conditions of the stream: stream discharge nearly doubled and stream temperatures decreased, becoming more similar to those in reference streams. While water quality clearly improved, meeting water quality standards alone does not guarantee protection of a waterbody's biological integrity. Results from studies on the ecological changes stemming from pollution-reduction actions, such as those presented in this series, also are needed to understand how best to restore or protect biological integrity and enhance ecological recovery in stream ecosystems. With a better knowledge of the ecological consequences of their decisions, environmental managers can better evaluate alternative actions and more accurately predict their effects.

Recovery of fish communities in a warm water stream following pollution abatement

The long-term recovery process for fish communities in a warm water stream in East Tennessee was studied using quantitative measurements over 20 years. The stream receives effluents from a U. S. Department of Energy (DOE) facility, but since 1985 these effluents have been greatly reduced, eliminated, or diluted as part of a substantial long-term pollution abatement program. The resulting changes in water quantity and quality led to a recovery of the fish communities, evidenced by significant changes in species richness, abundance (density and biomass), and community composition (e.g., number of fish species sensitive to stress). The fish community changes occurred over a spatial gradient (downstream from the headwater release zone nearest the DOE facility) and temporally, at multiple sampling locations in the stream. Changes in measured parameters were associated with specific remedial actions and the intervening steps within the recovery process are discussed with regard to changes in treatment processes.