PFOS or PreFOS? Are perfluorooctane sulfonate precursors (PreFOS) important determinants of human and environmental perfluorooctane sulfonate (PFOS) exposure?

The extent to which perfluorooctanesulfonate precursors (PreFOS) play a role in human or environmental exposure to perfluorooctanesulfonate (PFOS) is not well characterized. The diversity of manufactured PreFOS and its degradation products (e.g. C(8)F(17)SO(2)R and C(8)F(17)SO(2)NR'R', where R is H or F, and R' and R' are various) has made it difficult to track their fate. Temporal trends of PFOS in both humans and wildlife are discrepant, thus it is difficult to predict future exposure, and hypotheses about the role of PreFOS have been raised. Although abiotic degradation of commercially important PreFOS materials requires further research, current data suggest that the yield of PFOS is negligible or minor. On the other hand, in vivo biotransformation of PreFOS yields PFOS as the major metabolite, and >32% yields have been observed. In Canadians, exposure to PreFOS was equivalent or greater than direct PFOS exposure prior to 2002. In most ocean water, PFOS is dominant to PreFOS, but in the oceans east of Greenland there may be more PreFOS than PFOS, consistent with the fact that whales and humans in this region also show evidence of substantial PreFOS exposure. Quantitative assessments of PFOS body-burdens coming from PreFOS are complicated by the fact that PreFOS partitions to the cellular fraction of blood, thus biomonitoring in serum under predicts PreFOS relative to PFOS. Many unknowns exist that prevent accurate modelling, thus analytical methods that can distinguish directly manufactured PFOS, from PFOS that has been biotransformed from PreFOS, should be applied in future human and environmental monitoring. Two new source tracking principles are presented and applied to human serum.     

Exploring Environmental and Economic Trade-offs Associated with Aggregate Recycling from Decommissioned Forest Roads

Forest road decommissioning is a pro-active mechanism for preventing future habitat degradation and for increasing the likelihood of endangered salmonid survival in the western U.S. High implementation costs however preclude many desirable projects from being undertaken, especially on federally owned land. Previous research and real-world applications have demonstrated the cost savings potential of reusing aggregate recovered from forest roads during decommissioning. These cost savings can effectively subsidize decommissioning projects, suggesting an economic benefit associated with improving environmental benefit. We present a mixed integer, multiple objective formulation to identify the efficient trade-off surface between conflicting economic and environmental criteria, where environmental benefit is defined as the hazard weighted length of roads decommissioned. We compare nondominated frontiers identified with and without the opportunity to recycle aggregate. Our results suggest that aggregate recycling promotes a synergistic relationship between cost savings (subsidy) and environmental performance, where subsidies generally increase with increasing environmental performance. Effective subsidy values can reach 31% of total expenditure, at the maximum level of environmental benefit. Transportation managers are therefore able to recover and reuse a nonrenewable resource, while at the same time promoting economic and environmental efficiency.     

Application of a three-tier framework to assess ecological condition of Gulf of Mexico coastal wetlands

A multi-level coastal wetland assessment strategy was applied to wetlands in the northern Gulf of Mexico (GOM) to evaluate the feasibility of this approach for a broad national scale wetland condition assessment (US Environmental Protection Agency’s National Wetlands Condition Assessment). Landscape-scale assessment indicators (tier 1) were developed and applied at the sub-watershed (12-digit hydrologic unit code (HUC)) level within the GOM coastal wetland sample frame with scores calculated using land-use maps and geographic information system. Rapid assessment protocols (tier 2), using a combination of data analysis and field work, evaluated metrics associated with landscape context, hydrology, physical structure, and biological structure. Intensive site monitoring (tier 3) included measures of soil chemistry and composition, water column and pore-water chemistry, and dominant macrophyte community composition and tissue chemistry. Relationships within and among assessment levels were evaluated using multivariate analyses with few significant correlations found. More detailed measures of hydrology, soils, and macrophyte species composition from sites across a known condition gradient, in conjunction with validation of standardized rapid assessment method, may be necessary to fully characterize coastal wetlands across the region.     

Rebirth,Devastation and Sickness: Analyzing the Role of Metaphor in Media Discourses of Nuclear Power

Nuclear power plays an important but controversial role in policies to ensure domestic energy security, fuel poverty reduction and the mitigation of climate change. Our article construes the problem of nuclear power in terms of social discourse, language and public choice; specifically examining the role that metaphors play in the policy domain. We empirically analyze metaphors as framing devices in nuclear energy policy debates in the UK between April 2009 and March 2013, thereby capturing the impact of the Fukushima nuclear disaster in 2011. We employ documentary analysis of major UK national broadsheet and tabloid newspapers, using electronic bibliographic tools to extract the metaphors. We then map these metaphors using a Type Hierarchy Analysis, which examines how elements of the target domain (energy technologies and policies) originate from a different source domain. Type hierarchies identify and categorize metaphors, defining the affectual and emotional responses associated with them, providing us with grounded insight into their role in shaping discourse and as a consequence influence public engagement with energy policy. Our analysis highlights three emergent domains of discourse metaphors and discusses the implications of their deployment. Metaphors were found to be classified into three different categories: Rebirth (Renaissance), Devastation (Apocalypse, Inferno, Genie and Bomb) and Sickness (Addiction and Smoking).     

Simulation of Daily Flow Pathways,Tile‐Drain Nitrate Concentrations,and Soil‐Nitrogen Dynamics Using SWAT

Tile drainage significantly alters flow and nutrient pathways and reliable simulation at this scale is needed for effective planning of nutrient reduction strategies. The Soil and Water Assessment Tool (SWAT) has been widely utilized for prediction of flow and nutrient loads, but few applications have evaluated the model's ability to simulate pathway‐specific flow components or nitrate‐nitrogen (NO₃‐N) concentrations in tile‐drained watersheds at the daily time step. The objectives of this study were to develop and calibrate SWAT models for small, tile‐drained watersheds, evaluate model performance for simulation of flow components and NO₃‐N concentration at daily intervals, and evaluate simulated soil‐nitrogen dynamics. Model evaluation revealed that it is possible to meet accepted performance criteria for simulation of monthly total flow, subsurface flow (SSF), and NO₃‐N loads while obtaining daily surface runoff (SURQ), SSF, and NO₃‐N concentrations that are not satisfactory. This limits model utility for simulating best management practices (BMPs) and compliance with water quality standards. Although SWAT simulates the soil N‐cycle and most predicted fluxes were within ranges reported in agronomic studies, improvements to algorithms for soil‐N processes are needed. Variability in N fluxes is extreme and better parameterization and constraint, through use of more detailed agronomic data, would also improve NO₃‐N simulation in SWAT. Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.     

Statistical treatment for the wet bias in tree-ring chronologies: a case study from the Interior West,USA

Dendroclimatic research has long assumed a linear relationship between tree-ring increment and climate variables. However, ring width frequently underestimates extremely wet years, a phenomenon we refer to as ‘wet bias’. In this paper, we present statistical evidence for wet bias that is obscured by the assumption of linearity. To improve tree-ring-climate modeling, we take into account wet bias by introducing two modified linear regression models: a linear spline regression (LSR) and a likelihood-based wet bias adjusted linear regression (WBALR), in comparison with a quadratic regression (QR) model. Using gridded precipitation data and tree-ring indices of multiple species from various sites in Utah, both LSR and WBALR show a significant improvement over the linear regression model and out-perform QR in terms of in-sample \({R}^{2}\) and out-of-sample MSE. This further shows that the wet bias emerges from nonlinearity of tree-ring chronologies in reconstructing precipitation. The pattern and extent of wet bias varies by species, by site, and by precipitation regime, making it difficult to generalize the mechanisms behind its cause. However, it is likely that dis-coupling between precipitation amounts (e.g., percent received as rain/snow or percent infiltrating the soil) and its availability to trees (e.g., root zone dynamics), is the primary mechanism driving wet bias.     

Enhanced effect of HAH on citric acid-chelated Fe(II)-catalyzed percarbonate for trichloroethene degradation

This work demonstrates the impact of hydroxylamine hydrochloride (HAH) addition on enhancing the degradation of trichloroethene (TCE) by the citric acid (CA)-chelated Fe(II)-catalyzed percarbonate (SPC) system. The results of a series of batch-reactor experiments show that TCE removal with HAH addition was increased from approximately 57 to 79% for a CA concentration of 0.1 mM and from 89 to 99.6% for a 0.5 mM concentration. Free-radical probe tests elucidated the existence of hydroxyl radical (HO^•) and superoxide anion radical (O₂ ^•-) in both CA/Fe(II)/SPC and HAH/CA/Fe(II)/SPC systems. However, higher removal rates of radical probe compounds were observed in the HAH/CA/Fe(II)/SPC system, indicating that HAH addition enhanced the generation of both free radicals. In addition, increased contribution of O₂ ^•- in the HAH/CA/Fe(II)/SPC system compared to the CA/Fe(II)/SPC system was verified by free-radical scavengers tests. Complete TCE dechlorination was confirmed based on the total mass balance of the released Cl⁻ species. Lower concentrations of formic acid were produced in the later stages of the reaction for the HAH/CA/Fe(II)/SPC system, suggesting that HAH addition favors complete TCE mineralization. Studies of the impact of selected groundwater matrix constituents indicate that TCE removal in the HAH/CA/Fe(II)/SPC system is slightly affected by initial solution pH, with higher removal rates under acidic and near neutral conditions. Although HCO₃ ⁻ was observed to have an adverse impact on TCE removal for the HAH/CA/Fe(II)/SPC system, the addition of HAH reduced its inhibitory effect compared to the CA/Fe(II)/SPC system. Finally, TCE removal in actual groundwater was much significant with the addition of HAH to the CA/Fe(II)/SPC system. The study results indicate that HAH amendment has potential to enhance effective remediation of TCE-contaminated groundwater.

     

Remediation of a Former Dry Cleaner Using Nanoscale Zero Valent Iron

Nanoscale zero valent iron (nZVI) was evaluated in a laboratory treatability study and subsequently injected as an interim measure to treat source area groundwater impacts beneath a former dry cleaner located in Chapel Hill, North Carolina (the site). Dry cleaning operations resulted in releases of tetrachloroethene (PCE) that impacted site soil at concentrations up to 2,700 mg/kg and shallow groundwater at concentrations up to 41 mg/L. To achieve a design loading rate of 0.001 kg of iron per kilogram of aquifer material, approximately 725 kg of NanoFe? (PARS Environmental) was injected over a two‐week period into a saprolite and partially weather rock aquifer. Strong reducing conditions were established with oxidation–reduction potential (ORP) values below –728 mV. pH levels remained greater than 8 standard units for a period of 12 months. Injections resulted in near elimination of PCE within one month. cis‐1,2‐Dichloroethene accumulated at high concentrations (greater than 65 mg/L) for 12 months. MAROS software (Version 2.2; AFCEE, 2006 ) was used to calculate mass reduction of PCE and total ethenes at 96 percent and 58 percent, respectively, compared to baseline conditions. Detections of acetylene confirmed the presence of the beta‐elimination pathway. Detections of ethene confirmed complete dechlorination of PCE. Based on hydrogen gas generation, iron reactivity lasted 15 months. © 2013 Wiley Periodicals, Inc.     

Integrating Natural Resource Damage Assessment and Environmental Cleanup Activities at CERCLA and RCRA Sites

Although the release or threatened release of hazardous substances into the environment often creates liability for both cleanup costs and natural resource damages liability, the process of planning and conducting cleanup and the process of assessing natural resource damages are most often conducted separately. However, the substantial similarities between the two processes often present opportunities to integrate significant steps in each. Such integration has the potential to reduce both the cost of measuring and, often, resolving the full range of environmental claims at a given cleanup site and the time it takes to do so. It can also lead to faster restoration of injured natural resources and the services they provide to the public and the environment. One key reason for the lack of integration is the fact that cleanup managers generally know little if anything about the natural resource damage assessment process, while the public officials authorized to assess damages to natural resources know little about the cleanup process. This article identifies the similarities between the cleanup and natural resource damage assessment processes and provides guidance on when and how to integrate the two. © 2013 Wiley Periodicals, Inc.