The Case for Direct Measures of Soil-to-Groundwater Contaminant Mass Discharge at AFFF-Impacted Sites.

Many entities around the world are initiating massive field campaigns to characterize the environmental distribution of per- and polyfluoroalkyl substances (PFAS), particularly at aqueous film-forming foam (AFFF) impacted sites where historic point-source discharges occurred at the ground surface. Concurrently, many regulatory agencies are publishing criteria used in practice to define the "nature and extent" of PFAS-impacted environmental media. Specific to the soil-to-groundwater transport pathway protective of the groundwater ingestion end point, these soil criteria (or screening values) are to date exclusively based on the traditional approach used for hydrophobic organics with a number of simplifying assumptions. Research has clearly contradicted these assumptions, yet alternative methodologies have yet to emerge from the literature. This Perspective provides a rationale for why alternative approaches are critically necessary and proposes the application of lysimetry as a practical solution to accurately assess PFAS transport within unsaturated vadose zone soils. Ultimately, there is an urgent need to justify soil remediation on the basis of groundwater protection and to prioritize remedial efforts in order to optimize limited fiscal resources.

Rapid Removal of Poly- and Perfluorinated Compounds from Investigation-Derived Waste (IDW) in a Pilot-Scale Plasma Reactor.

A pilot-scale plasma reactor installed into an 8 × 20 ft2 mobile trailer was used to rapidly and effectively degrade poly- and perfluoroalkyl substances (PFAS) from liquid investigation-derived waste (IDW; development and purge water from monitoring wells) obtained from 13 different site investigations at Air Force installations. In the raw water, numerous PFAS were detected in a wide concentration range (∼10-105 ng/L; total oxidizable precursors (TOP) ∼102-105 ng/L, total fluorine by combustion ion chromatography ∼102 to 5 × 106 ng F/L). The concentration of total PFAS (12 perfluorocarboxylic acids (PFCAs) and perfluoroalkyl sulfonates (PFSAs)) in the 13 samples ranged between 2.7 and 1440 µg/L and the concentration of perfluorooctane sulfonate (PFOS) plus perfluorooctanoic acid (PFOA) ranged between 365 and 73700 ng/L. Plasma-based water treatment resulted in rapid perfluoroalkyl acids (PFAAs) removal from 4 L individual IDW samples with faster rates for longer-chain PFCAs (C ≥ 8) and PFSAs (C ≥ 6) than for PFCAs and PFSAs of shorter chain length. In 9 of the 13 IDW samples, both PFOS and PFOA were removed to below United States Environmental Protection Agency's (USEPA's) health advisory concentration level (HAL) concentrations in <1 min, whereas longer treatment times (up to 50 min) were required for the remaining four IDW samples due to either extremely high solution electrical conductivity, which decreased the plasma-liquid contact area (one IDW sample) or high concentrations of PFAAs and their precursors; the latter was found to be converted to PFAAs during the treatment. Overall, 36-99% of the TOP concentration present in the IDWs was removed during the treatment. There was no effect of non-PFAS co-contaminants on the degradation efficiency. Overall, the results indicate that plasma-based water treatment is a viable technology for the treatment of PFAS-contaminated IDW.

Optimizing outcomes in ADHD treatment: from clinical targets to novel delivery systems.

Our knowledge and understanding of the underlying neurobiology and symptomatic expression of ADHD has advanced dramatically over the past decade. Associated with these advances has been a similar explosion of new treatment options to individualize treatment for our patients. This article will: ∙ review strategies to measure ADHD symptoms and functional difficulties while seeking to achieve full symptomatic remission throughout the day ∙ summarize recent findings regarding the management and prioritization of ADHD and comorbid conditions and ∙ discuss the various pharmacologic treatment options with a focus on recently developed molecules and novel delivery systems.

A review of innovative approaches for onsite management of PFAS-impacted investigation derived waste.

The historic use of aqueous film-forming foam (AFFF) has led to widespread detection of per- and polyfluoroalkyl substance (PFAS) in groundwater, soils, sediments, drinking water, wastewater, and receiving aquatic systems throughout the United States (U.S.). Prior to any remediation activities, in order to identify the PFAS-impacted source zones and select the optimum management approach, extensive site investigations need to be conducted. These site investigations have resulted in the generation of considerable amount of investigation-derived waste (IDW) which predominantly consists of well purging water and drill fluid, equipment washing residue, soil, drill cuttings, and residues from the destruction of asphalt and concrete surfaces. IDW is often impacted by varying levels of PFAS which poses a substantial challenge concerning disposal to prevent potential mobilization of PFAS, logistical complexities, and increasing requirement for storage as a result of accumulation of the associated wastes. The distinct features of IDW involve the intermittent generation of waste, substantial volume of waste produced, and the critical demand for onsite management. This article critically focuses on innovative technologies and approaches employed for onsite treatment and management of PFAS-impacted IDW. The overall objective of this study centers on developing and deploying end-of-life treatment technology systems capable of facilitating unrestricted disposal, discharge, and/or IDW reuse on-site, thereby reducing spatial footprints and mobilization time.

Field-Scale Demonstration of PFAS Leachability Following In Situ Soil Stabilization.

A field-scale validation is summarized comparing the efficacy of commercially available stabilization amendments with the objective of mitigating per- and polyfluoroalkyl substance (PFAS) leaching from aqueous film-forming foam (AFFF)-impacted source zones. The scope of this work included bench-scale testing to evaluate multiple amendments and application concentrations to mitigate PFAS leachability and the execution of field-scale soil mixing in an AFFF-impacted fire-training area with nearly 2.5 years of post-soil mixing monitoring to validate reductions in PFAS leachability. At the bench scale, several amendments were evaluated and the selection of two amendments for field-scale evaluation was informed: FLUORO-SORB Adsorbent (FS) and RemBind (RB). Five ∼28 m3 test pits (approximately 3 m wide by 3 m long by 3 m deep) were mixed at a site using conventional construction equipment. One control test pit (Test Pit 1) included Portland cement (PC) only (5% dry weight basis). The other four test pits (Test Pits 2 through 5) compared 5 and 10% ratios (dry weight basis) of FS and RB (also with PC). Five separate monitoring events included two to three sample cores collected from each test pit for United States Environmental Protection Agency (USEPA) Method 1315 leaching assessment. After 1 year, a mass balance for each test pit was attempted comparing the total PFAS soil mass before, during, and after leach testing. Bench-scale and field-scale data were in good agreement and demonstrated >99% decrease in total PFAS leachability (mass basis; >98% mole basis) as confirmed by the total oxidizable precursor assay, strongly supporting the chemical stabilization of PFAS.

Assessment of PFAS in collocated soil and porewater samples at an AFFF-impacted source zone: Field-scale validation of suction lysimeters.

Per- and polyfluoroalkyl substances (PFAS) measurable in soil porewater authoritatively represent the mobile mass fraction critical to accurate assessment of leaching from source zones. This study evaluated PFAS occurrence in lysimeter-collected porewater samples for two depth intervals at a decades-old aqueous film-forming foam (AFFF)-impacted field site quarterly for a year. Notably, site-wide Log10 (∑PFAS) concentrations did not significantly differ among sampling events despite highly variable sample yields due to a heterogeneous and dynamic soil moisture regime. However, Log10 (∑PFAS) concentrations were significantly higher in the shallow interval concordant with higher mean soil concentrations and higher total organic carbon (TOC) reflecting net retention, which is supported by soil-to-groundwater annual mass discharge estimates less than 0.2% of the total source mass for any given PFAS. Interestingly, PFAS-specific Log10 (soil-to-porewater ratios) significantly increased with soil concentration in both depth intervals contrary to concentration dependence resulting from the saturation of sorption sites potentially implicating self-assembly as an additional operative retention mechanism. Overall, these data validate the use of suction lysimeters for short-term site characterization deployments and emphasize the importance of in situ porewater samples for interrogating PFAS transport within source zones.

Per- and Polyfluoroalkyl Substances (PFAS) in Surface Water Near US Air Force Bases: Prioritizing Individual Chemicals and Mixtures for Toxicity Testing and Risk Assessment.

Per- and polyfluoroalkyl substances (PFAS) are a large class of persistent chemicals used for decades in industrial and commercial applications. A key challenge with regard to estimating potential risk to ecological (and human) receptors associated with PFAS exposure lies in the fact that there are many different PFAS compounds and several to many can co-occur in any given environmental sample. We applied a data science approach to characterize and prioritize PFAS and PFAS mixtures from a large dataset of PFAS measurements in surface waters associated with US Air Force Installations with a history of the use of aqueous film-forming foams (AFFFs). Several iterations of stakeholder feedback culminated in a few main points that advanced our understanding of a complex dataset and the larger ecotoxicological problem. First, perfluorooctane sulfonate (PFOS) was often a dominant PFAS in a given surface water sample, frequently followed by perfluorohexane sulfonate (PFHxS). Second, a 4-chemical mixture generally accounted for >80% of the sum of all routinely reported PFAS in a sample, and the most representative 4-chemical mixture was composed of PFOS, PFHxS, perfluorohexanoic acid (PFHxA), and perfluorooctanoic acid (PFOA). We suggest that these results demonstrate the utility of formalized data science analysis and assessment frameworks to address complex ecotoxicological problems. Specifically, our example dataset results can be used to provide perspective on toxicity testing, ecological risk assessments, and field studies of PFAS in and around AFFF-impacted sites. Environ Toxicol Chem 2021;40:871-882. © 2020 SETAC.

Identifying and Managing Aqueous Film-Forming Foam-Derived Per- and Polyfluoroalkyl Substances in the Environment.

The use of aqueous film-forming foam (AFFF) has resulted in the widespread occurrence of per- and polyfluoroalkyl substances (PFAS) in groundwater, drinking water, soils, sediments, and receiving waters throughout the United States and other countries. We present the research and development efforts to date by the Strategic Environmental Research and Development Program (SERDP) and the Environmental Security Technology Certification Program (ESTCP) to measure PFAS in the environment, characterize AFFF-associated sources of PFAS, understand PFAS fate and behavior in the environment, assess the risk to ecological receptors, develop in situ and ex situ treatment technologies for groundwater, treat soils and investigation-derived wastes, and examine the ecotoxicity of PFAS-free fire suppression formulations. Environ Toxicol Chem 2021;40:24-36. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Environmental Sources, Chemistry, Fate, and Transport of Per- and Polyfluoroalkyl Substances: State of the Science, Key Knowledge Gaps, and Recommendations Presented at the August 2019 SETAC Focus Topic Meeting.

A Society of Environmental Toxicology and Chemistry (SETAC) Focused Topic Meeting (FTM) on the environmental management of per- and polyfluoroalkyl substances (PFAS) convened during August 2019 in Durham, North Carolina (USA). Experts from around the globe were brought together to critically evaluate new and emerging information on PFAS including chemistry, fate, transport, exposure, and toxicity. After plenary presentations, breakout groups were established and tasked to identify and adjudicate via panel discussions overarching conclusions and relevant data gaps. The present review is one in a series and summarizes outcomes of presentations and breakout discussions related to (1) primary sources and pathways in the environment, (2) sorption and transport in porous media, (3) precursor transformation, (4) practical approaches to the assessment of source zones, (5) standard and novel analytical methods with implications for environmental forensics and site management, and (6) classification and grouping from multiple perspectives. Outcomes illustrate that PFAS classification will continue to be a challenge, and additional pressing needs include increased availability of analytical standards and methods for assessment of PFAS and fate and transport, including precursor transformation. Although the state of the science is sufficient to support a degree of site-specific and flexible risk management, effective source prioritization tools, predictive fate and transport models, and improved and standardized analytical methods are needed to guide broader policies and best management practices. Environ Toxicol Chem 2021;40:3234-3260. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Application of ridge regression to quantify marginal effects of collinear soil properties on phytoaccumulation of arsenic, cadmium, lead, and zinc.

Soil properties that mitigate hazardous effects of environmental contaminants through soil chemical sequestration should be considered when evaluating ecological risk from terrestrial contamination. The objective of this research was to identify predominant soil chemical/physical properties that modify phytoaccumulation of As, Cd, Pb, and Zn to the non-hyperaccumulating higher plants: Alfalfa (Medicago sativa L.), perennial ryegrass (Lolium perenne L.), and Japanese millet (Echinochloa crusgalli L.). Transmission coefficients were estimated from a dose-response experiment with the use of aboveground tissue contaminant concentrations and correlated with selected soil property measurements to develop statistical prediction models for soil-specific adjustments to ecological risk assessments. Significant correlations between soil properties and transmission coefficients were observed for all four contaminants. Intercorrelation was also observed among soil properties, including cation exchange capacity (CEC) and soil pH (p = 0.035), CEC and total clay (p = 0.030), organic carbon (OC) and total clay content (p = 0.085), reactive iron oxides (FeOX) and OC (p = 0.078), and reactive Mn oxide (MnOX) and total clay content (p < 0.001). Ridge regression, a technique that suppresses the effects of multicollinearity and enables prediction, was used to assess the marginal contributions of soil properties found to mitigate phytoaccumulation. Prediction models were developed for all four contaminants. Significant variables were FeOX for As or pH, OC, CEC, clay content, or a combination of factors for cationic metal models. Ridge regression provides a powerful alternative to conventional multiple regression techniques for ecotoxicological studies when intercorrelated predictors are experimentally unavoidable, as with soil properties.

Application of ridge regression to quantify marginal effects of collinear soil properties on phytotoxicity of arsenic, cadmium, lead, and zinc.

Soil properties that the mitigate hazardous effects of environmental contaminants through soil chemical sequestration should be considered when evaluating ecological risk from terrestrial contamination. The objective of the present research was to identify predominant soil chemical and physical properties that modify the phytotoxicity of As, Cd, Pb, and Zn to the nonhyperaccumulating higher plant perennial ryegrass (Lolium perenne L.). Phytotoxicity parameters were estimated from a dose-response experiment using the aboveground dry matter growth endpoint and were correlated with an assortment of relevant soil property measurements, with the ultimate goal of developing statistical prediction models for soil-specific adjustments to ecological risk assessments. Significant correlations between soil properties and phytotoxicity estimates were observed for all four contaminants; however, intercorrelation was observed among soil properties, necessitating an alternative to the conventional multiple regression commonly used by ecotoxicologists. Ridge regression, a regression-based technique that suppresses the effects of multicollinearity and enables prediction, was used to assess the marginal contributions of all properties found to mitigate phytotoxicity. Ridge regression models are presented along with two common conventional regression methods and are collectively discussed within the context of the mitigating effects of soil properties on metal/metalloid phytotoxicity. Ridge regression appears to be a powerful alternative to conventional multiple regression for ecotoxicological studies when intercorrelation among predictors is experimentally unavoidable, such as with soil properties.

Ecological risk assessment of perfluooroctane sulfonate to aquatic fauna from a bayou adjacent to former fire training areas at a US Air Force installation.

Per- and polyfluoroalkyl substances (PFASs) continue to receive significant attention, with particular concern for PFASs such as perfluorooctane sulfonate (PFOS), which was a constituent of aqueous film-forming foam used widely as a fire suppressant for aircraft since the 1970s. We were interested in the potential for risk to ecological receptors inhabiting Cooper Bayou, which is adjacent to 2 former fire-training areas at Barksdale Air Force Base (LA, USA). Previous research showed higher PFOS concentrations in surface water and biota from Cooper Bayou compared to reference sites. To estimate risk, we compared surface water concentrations from multiple sites within Cooper Bayou with several PFOS chronic toxicity benchmarks for freshwater aquatic organisms (∼0.4-5.1 µg PFOS/L) and showed probability of exceedances from 0.04 to 0.5, suggesting a potential for adverse effects in the most contaminated habitats. A tissue-residue assessment similarly showed some exceedance of benchmarks but with a lower probability (maximum = 0.17). Both fire-training areas have been inactive for more than a decade, so exposures (and, thus, risks) are expected to decline. Several uncertainties limit confidence in our risk estimates including highly dynamic surface water concentrations and limited chronic toxicity data for relevant species. Also, we have little data concerning organisms higher in the food chain which may receive higher lifetime exposures given the potential for PFOS to bioaccumulate and the longevity of many of these organisms. Overall, the present study suggests that PFOS can occur at concentrations that may cause adverse effects to ecological receptors, although additional, focused research is needed to reduce uncertainties. Environ Toxicol Chem 2018;37:2198-2209. © 2018 SETAC.

Arsenic Speciation of Contaminated Soils / Solid Wastes and Relative Oral Bioavailability in Swine and Mice.

Arsenic (As) is one of the most widespread, toxic elements in the environment and human activities have resulted in a large number of contaminated areas. However abundant, the potential of As toxicity from exposure to contaminated soils is limited to the fraction that will dissolve in the gastrointestinal system and be absorbed into systemic circulation or bioavailable species. In part, the release of As from contaminated soil to gastrointestinal fluid depends on the form of solid phase As also termed "As speciation." In this study, 27 As-contaminated soils and solid wastes were analyzed using X-ray absorption spectroscopy (XAS) and results were compared to in vivo bioavailability values determined using the adult mouse and juvenile swine bioassays. Arsenic bioavailability was lowest for soils that contained large amounts of arsenopyrite and highest for materials that contained large amounts of ferric arsenates. Soil and solid waste type and properties rather than the contamination source had the greatest influence on As speciation. Principal component analysis determined that As(V) adsorbed and ferric arsenates were the dominant species that control As speciation in the selected materials. Multiple linear regression (MLR) was used to determine the ability of As speciation to predict bioavailability. Arsenic speciation was predictive of 27% and 16% of RBA As determined using the juvenile swine and adult mouse models, respectively. Arsenic speciation can provide a conservative estimate of RBA As using MLR for the juvenile swine and adult mouse bioassays at 55% and 53%, respectively.

The impact of cognitive challenges in major depression: the role of the primary care physician.

Nearly 1 in 5 Americans will struggle with major depression in their lives; some will have recurring bouts. Recent psychiatric research has given new attention to the prevalence of cognitive deficits in major depression and the impact such deficits have on remission and overall life functioning. When depression is partially treated i.e., leaving residual symptoms, patients have higher rates of relapse and lower functional outcomes. Impaired cognitive functioning is a frequent residual symptom, persisting in about 45% of patients even when emotional symptoms have improved, and results in a disproportionate share of the functional impairment, particularly in the workplace. Patients with depression have disrupted circuitry in brain regions responsible for cognition and it is therefore important to screen depressed patients for cognitive as well as emotional symptoms. Cognitive dysfunction should be evaluated in every mood disordered patient with validated self-report scales such as the Patient Health Questionnaire-9 or the Beck Depression Inventory and objective measures of cognitive function are also very very useful. Two easily administered tests are the Trails B Test and the Digit Symbol Substitution Test. Each take less than two minutes and measure working memory, executive function, and processing speed and can track cognitive improvement in depressed patients. Treatment of cognitive dysfunction in major depression is complicated by the 'serotonin conundrum': SSRI's frequently do not treat to full remission, and can cause cognitive blunting-actually adding to cognitive problems. Based on recent data including results from a recently completed meta-analysis by McIntyre and colleagues, an evidence-based algorithm for treating cognitive symptoms in depression is presented. A hierarchy of antidepressants and augmentation strategies based on the best available evidence is discussed. In conclusion, cognitive symptoms in major depressive disorder have been recognized as a target of therapeutic improvement by the FDA and have become a focus of clinical importance.

Co-occurrence of 1,4-dioxane with trichloroethylene in chlorinated solvent groundwater plumes at US Air Force installations: Fact or fiction.

Increasing regulatory attention to 1,4-dioxane has prompted the United States Air Force (USAF) to evaluate potential environmental liabilities, primarily associated with legacy contamination, at an enterprise scale. Although accurately quantifying environmental liability is operationally difficult given limited historic environmental monitoring data, 1,4-dioxane is a known constituent (i.e., stabilizer) of chlorinated solvents, in particular 1,1,1-trichloroethane (TCA). Evidence regarding the co-occurrence of 1,4-dioxane and trichloroethylene (TCE), however, has been heavily debated. In fact, the prevailing opinion is that 1,4-dioxane was not a constituent of past TCE formulations and, therefore, these 2 contaminants would not likely co-occur in the same groundwater plume. Because historic handling, storage, and disposal practices of chlorinated solvents have resulted in widespread groundwater contamination at USAF installations, significant potential exists for unidentified 1,4-dioxane contamination. Therefore, the objective of this investigation is to determine the extent to which 1,4-dioxane co-occurs with TCE compared to TCA, and if these chemicals are co-contaminants, whether or not there is significant correlation using available monitoring data. To accomplish these objectives, the USAF Environmental Restoration Program Information Management System (ERPIMS) was queried for all relevant records for groundwater monitoring wells (GMWs) with 1,4-dioxane, TCA, and TCE, on which both categorical and quantitative analyses were carried out. Overall, ERPIMS contained 5788 GMWs from 49 installations with records for 1,4-dioxane, TCE, and TCA analytes. 1,4-Dioxane was observed in 17.4% of the GMWs with detections for TCE and/or TCA, which accounted for 93.7% of all 1,4-dioxane detections, verifying that 1,4-dioxane is seldom found independent of chlorinated solvent contamination. Surprisingly, 64.4% of all 1,4-dioxane detections were associated with TCE independently. Given the extensive data set, these results conclusively demonstrate for the first time that 1,4-dioxane is a relatively common groundwater co-contaminant with TCE. Trend analysis demonstrated a positive log-linear relationship where median 1,4-dioxane levels increased between approximately 6% and approximately 20% of the increase in TCE levels. In conclusion, this data mining exercise suggests that 1,4-dioxane has a probability of co-occurrence of approximately 17% with either TCE and/or TCA. Given the challenges imposed by remediation of 1,4-dioxane and the pending promulgation of a federal regulatory standard, environmental project managers should use the information presented in this article for prioritization of future characterization efforts to respond to the emerging issue. Importantly, site investigations should consider 1,4-dioxane a potential co-contaminant of TCE in groundwater plumes.