PFAS Experts Symposium: Statements on regulatory policy,chemistry and analytics,toxicology, transport/fate,and remediation for per‐ and polyfluoroalkyl substances (PFAS) contamination issues

Sixty leading members of the scientific, engineering, regulatory, and legal communities assembled for the PFAS Experts Symposium in Arlington, Virginia on May 20 and 21, 2019 to discuss issues related to per‐ and polyfluoroalkyl substances (PFAS) based on the quickly evolving developments of PFAS regulations, chemistry and analytics, transport and fate concepts, toxicology, and remediation technologies.  The Symposium created a venue for experts with various specialized skills to provide opinions and trade perspectives on existing and new approaches to PFAS assessment and remediation in light of lessons learned managing other contaminants encountered over the past four decades. The following summarizes several consensus points developed as an outcome of the Symposium:

• Regulatory and policy issues: The response by many states and the US Environmental Protection Agency (USEPA) to media exposure and public pressure related to PFAS contamination is to relatively quickly initiate programs to regulate PFAS sites. This includes the USEPA establishing relatively low lifetime health advisory levels for PFAS in drinking water and even more stringent guidance and standards in several states. In addition, if PFAS are designated as hazardous substances at the federal level, as proposed by several Congressional bills, there could be wide‐reaching effects including listing of new Superfund sites solely for PFAS, application of stringent state standards, additional characterization and remediation at existing sites, reopening of closed sites, and cost renegotiation among PRPs.
• Chemistry and analytics: PFAS analysis is confounded by the lack of regulatory‐approved methods for most PFAS in water and all PFAS in solid media and air, interference with current water‐based analytical methods if samples contain high levels of suspended solids, and sample collection and analytical interference due to the presence of PFAS in common consumer products, sampling equipment, and laboratory materials.
• Toxicology and risk: Uncertainties remain related to human health and ecological effects for most PFAS; however, regulatory standards and guidance are being established incorporating safety factors that result in part per trillion (ppt) cleanup objectives. Given the thousands of PFAS that may be present in the environment, a more appropriate paradigm may be to develop toxicity criteria for groups of PFAS rather than individual PFAS.
• Transport and fate: The recalcitrance of many perfluoroalkyl compounds and the capability of some fluorotelomers to transform into perfluoroalkyl compounds complicate conceptual site models at many PFAS sites, particularly those involving complex mixtures, such as firefighting foams. Research is warranted to better understand the physicochemical properties and corresponding transport and fate of most PFAS, of branched and linear isomers of the same compounds, and of the interactions of PFAS with other co‐contaminants such as nonaqueous phase liquids. Many PFAS exhibit complex transport mechanisms, particularly at the air/water interface, and it is uncertain whether traditional transport principles apply to the ppt levels important to PFAS projects. Existing analytical methods are sufficient when combined with the many advances in site characterization techniques to move rapidly forward at selected sites to develop and test process‐based conceptual site models.
• Existing remediation technologies and research: Current technologies largely focus on separation (sorption, ion exchange, or sequestration). Due to diversity in PFAS properties, effective treatment will likely require treatment trains. Monitored natural attenuation will not likely involve destructive reactions, but be driven by processes such as matrix diffusion, sorption, dispersion, and dilution.

The consensus message from the Symposium participants is that PFAS present far more complex challenges to the environmental community than prior contaminants. This is because, in contrast to chlorinated solvents, PFAS are severely complicated by their mobility, persistence, toxicological uncertainties, and technical obstacles to remediation—all under the backdrop of stringent regulatory and policy developments that vary by state and will be further driven by USEPA. Concern was expressed about the time, expense, and complexity required to remediate PFAS sites and whether the challenges of PFAS warrant alternative approaches to site cleanups, including the notion that adaptive management and technical impracticability waivers may be warranted at sites with expansive PFAS plumes. A paradigm shift towards receptor protection rather than broad scale groundwater/aquifer remediation may be appropriate.     

A multispecies test of source–sink indicators to prioritize habitat for declining populations

For species at risk of decline or extinction in source–sink systems, sources are an obvious target for habitat protection actions. However, the way in which source habitats are identified and prioritized can reduce the effectiveness of conservation actions. Although sources and sinks are conceptually defined using both demographic and movement criteria, simplifications are often required in systems with limited data. To assess the conservation outcomes of alternative source metrics and resulting prioritizations, we simulated population dynamics and extinction risk for 3 endangered species. Using empirically based habitat population models, we linked habitat maps with measured site‐ or habitat‐specific demographic conditions, movement abilities, and behaviors. We calculated source–sink metrics over a range of periods of data collection and prioritized consistently high‐output sources for conservation. We then tested whether prioritized patches identified the habitats that most affected persistence by removing them and measuring the population response. Conservation decisions based on different source–sink metrics and durations of data collection affected species persistence. Shorter time series obscured the ability of metrics to identify influential habitats, particularly in temporally variable and slowly declining populations. Data‐rich source–sink metrics that included both demography and movement information did not always identify the habitats with the greatest influence on extinction risk. In some declining populations, patch abundance better predicted influential habitats for short‐term regional persistence. Because source–sink metrics (i.e., births minus deaths; births and immigrations minus deaths and emigration) describe net population conditions and cancel out gross population counts, they may not adequately identify influential habitats in declining populations. For many nonequilibrium populations, new metrics that maintain the counts of individual births, deaths, and movement may provide additional insight into habitats that most influence persistence.     

Circuit-theory applications to connectivity science and conservation

Conservation practitioners have long recognized ecological connectivity as a global priority for preserving biodiversity and ecosystem function. In the early years of conservation science, ecologists extended principles of island biogeography to assess connectivity based on source patch proximity and other metrics derived from binary maps of habitat. From 2006 to 2008, the late Brad McRae introduced circuit theory as an alternative approach to model gene flow and the dispersal or movement routes of organisms. He posited concepts and metrics from electrical circuit theory as a robust way to quantify movement across multiple possible paths in a landscape, not just a single least-cost path or corridor. Circuit theory offers many theoretical, conceptual, and practical linkages to conservation science. We reviewed 459 recent studies citing circuit theory or the open-source software Circuitscape. We focused on applications of circuit theory to the science and practice of connectivity conservation, including topics in landscape and population genetics, movement and dispersal paths of organisms, anthropogenic barriers to connectivity, fire behavior, water flow, and ecosystem services. Circuit theory is likely to have an effect on conservation science and practitioners through improved insights into landscape dynamics, animal movement, and habitat-use studies and through the development of new software tools for data analysis and visualization. The influence of circuit theory on conservation comes from the theoretical basis and elegance of the approach and the powerful collaborations and active user community that have emerged. Circuit theory provides a springboard for ecological understanding and will remain an important conservation tool for researchers and practitioners around the globe.     

COLUMBIA RIVER FLOW AND DROUGHT SINCE 17501

ABSTRACT: A network of 32 drought sensitive tree‐ring chronologies is used to reconstruct mean water year flow on the Columbia River at The Dalles, Oregon, since 1750. The reconstruction explains 30 percent of the variability in mean water year (October to September) flow, with a large portion of unexplained variance caused by underestimates of the most severe low flow events. Residual statistics from the tree‐ring reconstruction, as well as an identically specified instrumental reconstruction, exhibit positive trends over time. This finding suggests that the relationship between drought and streamflow has changed over time, supporting results from hydrologic models, which suggest that changes in land cover over the 20th Century have had measurable impacts on runoff production. Low pass filtering the flow record suggests that persistent low flows during the 1840s were probably the most severe of the past 250 years, but that flows during the 1930s were nearly as extreme. The period from 1950 to 1987 is anomalous in the context of this record for having no notable multiyear drought events. A comparison of the flow reconstruction to paleorecords of the Pacific Decadal Oscillation (PDO) and El Nino/Southern Oscillation (ENSO) support a strong 20th Century link between large scale circulation and streamflow, but suggests that this link is very weak prior to 1900.     

AN APPLICATION OF MATHEMATICAL PROGRAMMING IN PLANNING SURFACE WATER STORAGE1

Designing a surface reservoir involves the concept of reservoir yield. This concept embodies three basic information items: hydrologic regime, active storage volume, and reservoir release policy. In the actual case presented below, the magnitude of the active storage was prescribed by a legal procedure, so that the planning issue became that of determining the reservoir yield given the hydrological information. A stochastic dynamic programming model was formulated to derive a schedule of seasonal optimal reservoir releases and their respective probabilities of occurrence. This schedule is the reservoir yield. The yearly cycle was divided into three seasons representing the actual climatic conditions, and conditional probabilities linking streamflows in consecutive seasons were estimated. An operating policy was postulated, based on the same set of legal decisions that prescribed the active storage volume, and target reservoir releases were assumed. Similarly, target storages at the end of each season were set up. The optimizing/ minimizing criterion in the dynamic programming formulation was the sum of squares of deviations of actual releases and final storage volumes from their respective targets.     

Household evacuation characteristics in American Samoa during the 2009 Samoa Islands tsunami

Tsunamis represent significant threats to human life and development in coastal communities. This quantitative study examines the influence of household characteristics on evacuation actions taken by 211 respondents in American Samoa who were at their homes during the 29 September 2009 M_w 8.1 Samoa Islands earthquake and tsunami disaster. Multiple logistic regression analysis of survey data was used to examine the association between evacuation and various household factors. Findings show that increases in distance to shoreline were associated with a slightly decreased likelihood of evacuation, whereas households reporting higher income had an increased probability of evacuation. The response in American Samoa was an effective one, with only 34 fatalities in a tsunami that reached shore in as little as 15 minutes. Consequently, future research should implement more qualitative study designs to identify event and cultural specific determinants of household evacuation behaviour to local tsunamis.     

Zen and the Art of the Selfie Stick: Blogging the John Muir Trail Thru-Hiking Experience

For cultures around the world, a journey, particularly one undertaken by foot through landscapes that are simultaneously natural and cultural, is both a metaphor for the discovery of the self and the divine and an embodied practice in the physical realm. Here we analyze twenty-six publicly available blogs of thru-hikers of the John Muir Trail in the Sierra Nevada mountains of California, U.S.A. Cognizant of the critiques of the intrusion of technology into wilderness areas, we examine how the communication medium of travel blogs becomes a vehicle for both self-reflection and for sharing spiritual experiences, and how the act of blogging merges virtual and corporeal communities formed among hikers. It is in the intersection of these social networks and mobile communication technologies that we find suggestions of changing relationships between a subculture of tech-savvy and highly connected hikers sometimes called “flashpackers” and the physical landscapes through which they travel.     

Is there a need to re-examine the approval of bismuth shotshell as a non-toxic alternative to lead based on the precautionary principle?

In 1997, the Canadian Wildlife Service (CWS) approved bismuth shotshell as an alternative to lead. We assessed whether there is a need to re-examine the toxicity of bismuth issue using the initial CWS toxicity guideline criteria. Review of the literature suggests that in the context of the precautionary principle, a re-examination of the approval of bismuth shotshell should be undertaken based on animal health issues, associated deficiencies in the analytical data used in the original assessment, and to a lesser extent, human health concerns.     

Impact of land-cover change in the Southern Amazonia climate: a case study for the region of Alta Floresta,Mato Grosso,Brazil

The transformation of forest into pastures in the Brazilian Amazon leads to significant consequences to climate at local scale. In the region of Alta Floresta (Mato Grosso, Brazil), deforestation has been intense with over half the forests being cut since 1970. This article first examines the evolution of precipitation observed in this region and shows a significant trend in the decrease in total precipitation especially at the end of the dry season and at the beginning of the rainy season. The study then compares the temperatures measured in cleared and forested sectors within a reserve in the area of Alta Floresta (Mato Grosso, Brazil) between 2006 and 2007. The cleared sector was always hotter and drier (from 5% to 10%) than the forested area. This difference was not only especially marked during the day when it reached on average 2°C but also seemed to increase during the night with the onset of the dry season (+0.5°C). The Urban Heat Island effect is also evident especially during the night and in the dry season.     

Landscape resistance to dispersal: simulating long-term effects of human disturbance on a small and isolated wolf population in southwestern Manitoba, Canada

Landscape fragmentation affects wildlife population viability, in part, through the effects it has on individual dispersal. In addition, some forms of human disturbance impinge on dispersal without physically fragmenting habitats. Here, we use the term "landscape resistance" to capture constraints to dispersal that cannot be linked directly to fragmentation. The extent to which landscape resistance can influence population persistence is not well understood. Agricultural development over the past 60?years has resulted in considerable habitat fragmentation in the Riding Mountain National Park (RMNP) region in southwestern Manitoba, Canada. We examined how park boundaries, roads outside park boundaries and negative human attitudes have altered dispersal success and population persistence. We examined whether stochastic disturbance, representing infectious disease epidemics, further reduced long-term population persistence for various scenarios. Finally, we assessed whether the simultaneous occurrence of the three features had additive effects. We simulated dispersal using HexSim, a spatially explicit individual-based population model, parameterised with data on wolves (Canis lupus) in the RMNP region. Simulations that separately accounted for negative human attitudes and roads outside the park boundaries exhibited lower mean population size than those that ignored these details. Increasing deflection from park boundaries did not appear to have significant impacts. Our results did not indicate the presence of additive effects, and scenarios incorporating all three features had similar results as that of roads. Stochastic disturbance further reduced mean population size. Our results do illustrate how less-visible human disturbances (i.e. those that do not clearly alter landscape characteristics) can significantly limit dispersal and population persistence.