Seven‐year performance evaluation of a permeable reactive barrier

In June and July 2001, the Massachusetts Department of Environmental Protection (MassDEP) installed a permeable reactive barrier (PRB) to treat a groundwater plume of chlorinated solvents migrating from an electronics manufacturer in Needham, Massachusetts, toward the Town of Wellesley's Rosemary Valley wellfield. The primary contaminant of concern at the site is trichloroethene (TCE), which at the time had a maximum average concentration of approximately 300 micrograms per liter directly upgradient of the PRB. The PRB is composed of a mix of granular zero‐valent iron (ZVI) filings and sand with a pure‐iron thickness design along its length between 0.5 and 1.7 feet. The PRB was designed to intercept the entire overburden plume; a previous study had indicated that the contaminant flux in the bedrock was negligible. Groundwater samples have been collected from monitoring wells upgradient and downgradient of the PRB on a quarterly basis since installation of the PRB. Inorganic parameters, such as oxidation/reduction potential, dissolved oxygen, and pH, are also measured to determine stabilization during the sampling process. Review of the analytical data indicates that the PRB is significantly reducing TCE concentrations along its length. However, in two discrete locations, TCE concentrations show little decrease in the downgradient monitoring wells, particularly in the deep overburden. Data available for review include the organic and inorganic analytical data, slug test results from nearby bedrock and overburden wells, and upgradient and downgradient groundwater‐level information. These data aid in refining the conceptual site model for the PRB, evaluating its performance, and provide clues as to the reasons for the PRB's underperformance in certain locations. © 2008 Wiley Periodicals, Inc.     

Evaluation of cover crop and reduced cultivation for reducing nitrate leaching in Ireland

Nitrate (NO(3)) loss from arable systems to surface and groundwater has attracted considerable attention in recent years in Ireland. Little information exists under Irish conditions, which are wet and temperate, on the effects of winter cover crops and different tillage techniques on NO(3) leaching. This study investigated the efficacy of such practices in reducing NO(3) leaching from a spring barley (Hordeum vulgare L.) system in the Barrow River valley, southeast Ireland. The study compared the effect of two tillage systems (plow-based tillage and noninversion tillage) and two over-winter alternatives (no vegetative cover and a mustard cover crop) on soil solution NO(3) concentrations at 90 cm depth over two winter drainage seasons (2003/04 and 2004/05). Soil samples were taken and analyzed for inorganic N. During both years of the study, the use of a mustard cover crop significantly reduced NO(3) losses for the plowed and reduced cultivation treatments. Mean soil solution NO(3) concentrations were between 38 and 70% lower when a cover crop was used, and total N load lost over the winter was between 18 and 83% lower. Results from this study highlight the importance of drainage volume and winter temperatures on NO(3) concentrations in soil solution and overall N load lost. It is suggested that cover crops will be of particular value in reducing NO(3) loss in temperate regions with mild winters, where winter N mineralization is important and high winter temperatures favor a long growing season.     

Historical and contemporary cultural ecosystem service values in the rapidly urbanizing city state of Singapore

Cultural ecosystem services are a function of people and place, so may change as a location transitions from rural to urban. Singapore has undergone rapid urbanization after its independence in 1965, with a concomitant decline in natural habitat extent and accessibility. Using coastal mangrove forests as a case study habitat, changing cultural values were explored with a novel array of techniques, including qualitative archival analysis (photographs, oral histories), current sources (publically uploaded social media photographs), and surveys of (a) the general public and (b) visitors to publically accessible mangroves. Cultural value changed through time, with a significant transition from intrinsic, intrapersonal values (spiritual, cultural heritage) to instrumental, interpersonal values (recreation, education). Additionally, cultural value varied between different mangroves depending on their public accessibility, and the evolving degree of human interaction with the ecosystem as urban development occured. Cultural values change as development transitions, though mangroves still play an important cultural role in a heavily urbanized environment.     

<Emphasis Type="Italic">Hippophae rhamnoides</Emphasis> on a coastal dune system: a thorny issue?

The study mapped the spread of the invasive non-native shrub, Hippophae rhamnoides, on a coastal dune system in South Wales. H. rhamnoides colonies spread across the system, covering around 60.9 ha in 1996 compared to 2.4 ha in 1957. Clearance activities have since decreased the total to around 23 ha. The effects of this expansion on ground flora were assessed through comparison of species assemblages in colonised, never colonised and cleared areas. Dichotomisation presented a number of markedly different communities which correlated to their status of H. rhamnoides invasion. Colonised quadrats were overwhelmingly composed of H. rhamnoides and a few shade-tolerant species such as Galium aperine and Urtica dioica. Cleared quadrats did not support desirable dune grassland species present in never colonised sites, although those which had been cleared for the longest period may be regaining some characteristic species. Clearance work in future needs to concentrate on the complete removal of smaller H. rhamnoides patches whilst also preventing the establishment of Chamerion angustifolium and other ruderal species which in turn inhibit the development of typical dune grassland communities.     

Modelling the effects of ‘coastal’ acidification on copper speciation

We present here a copper speciation model that accounts for the long-term (‘coastal-acidification’) and short-term (daily and seasonal variation) variability in water pH and water temperature. The developed model is applied to a sub-tropical estuary (Moreton Bay, Australia) at a one hundred year time scale so that outputs are consistent with climate change projections. The model predicts that the mean cupric ion concentration (Cu²⁺) in the estuary will increase by 115% over the next 100 years as a result of the projected decrease in pH and increase in water temperature. Through calibration, the estimated concentration of copper-complexing dissolved organic matter (DOM) in the estuary is found to be 22.5 nM. An increase in the concentration of Cu²⁺, which is the most toxic and bioavailable form of copper, has implications for ecosystem health and may have a negative effect on the detoxifying capacity of DOM. Models that provide a framework for coupling biological, chemical and physical processes are important for providing a holistic perspective of coastal systems, especially for better understanding a system within the context of climatic and non-climatic drivers.     

Numerical Model Inter-comparison for Wind Flow and Turbulence Around Single-Block Buildings

Wind flow and turbulence within the urban canopy layer can influence the heating and ventilation of buildings, affecting the health and comfort of pedestrians, commuters and building occupants. In addition, the predictive capability of pollutant dispersion models is heavily dependent on wind flow models. For that reason, well-validated microscale models are needed for the simulation of wind fields within built-up urban microenvironments. To address this need, an inter-comparison study of several such models was carried out within the European research network ATREUS. This work was conducted as part of an evaluation study for microscale numerical models, so they could be further implemented to provide reliable wind fields for building energy simulation and pollutant dispersion codes. Four computational fluid dynamics (CFD) models (CHENSI, MIMO, VADIS and FLUENT) were applied to reduced-scale single-block buildings, for which quality-assured and fully documented experimental data were obtained. Simulated wind and turbulence fields around two surface-mounted cubes of different dimensions and wall roughness were compared against experimental data produced in the wind tunnels of the Meteorological Institute of Hamburg University under different inflow and boundary conditions. The models reproduced reasonably well the general flow patterns around the single-block buildings, although over-predictions of the turbulent kinetic energy were observed near stagnation points in the upwind impingement region. Certain discrepancies between the CFD models were also identified and interpreted. Finally, some general recommendations for CFD model evaluation and use in environmental applications are presented.     

“Nutrient Inputs to the Laurentian Great Lakes by Source and Watershed Estimated Using SPARROW Watershed Models” by Dale M. Robertson and David A. Saad2

Richards, R. Peter, Ibrahim Alameddine, J. David Allan, David B. Baker, Nathan S. Bosch, Remegio Confesor, Joseph V. DePinto, David M. Dolan, Jeffrey M. Reutter, and Donald Scavia, 2012. Discussion –“Nutrient Inputs to the Laurentian Great Lakes by Source and Watershed Estimated Using SPARROW Watershed Models” by Dale M. Robertson and David A. Saad. Journal of the American Water Resources Association (JAWRA) 1‐10. DOI: 10.1111/jawr.12006 Abstract: Results from the Upper Midwest Major River Basin (MRB3) SPARROW model and underlying Fluxmaster load estimates were compared with detailed data available in the Lake Erie and Ohio River watersheds. Fluxmaster and SPARROW estimates of tributary loads tend to be biased low for total phosphorus and high for total nitrogen. These and other limitations of the application led to an overestimation of the relative contribution of point sources vs. nonpoint sources of phosphorus to eutrophication conditions in Lake Erie, when compared with direct estimates for data‐rich Ohio tributaries. These limitations include the use of a decade‐old reference point (2002), lack of modeling of dissolved phosphorus, lack of inclusion of inputs from the Canadian Lake Erie watersheds and from Lake Huron, and the choice to summarize results for the entire United States Lake Erie watershed, as opposed to the key Western and Central Basin watersheds that drive Lake Erie’s eutrophication processes. Although the MRB3 SPARROW model helps to meet a critical need by modeling unmonitored watersheds and ranking rivers by their estimated relative contributions, we recommend caution in use of the MRB3 SPARRROW model for Lake Erie management, and argue that the management of agricultural nonpoint sources should continue to be the primary focus for the Western and Central Basins of Lake Erie.     

A Multiple Lines of Evidence Framework to Evaluate Intrinsic Biodegradation of 1,4‐Dioxane

Development of a multiple lines of evidence (MLOE) framework to evaluate the intrinsic biodegradation potential of 1,4‐dioxane is vital to implementing management strategies at groundwater sites impacted by 1,4‐dioxane. A comprehensive MLOE approach was formed to provide significant evidence of natural degradation of 1,4‐dioxane comingled with tetrahydrofuran (THF) within a large, diffuse plume. State‐of‐the art molecular biological analyses and compound‐specific isotope analysis (CSIA) were employed to support more traditional approaches for data analysis (concentration trend analyses, spatial distribution, temporal changes, geochemical biodegradation attenuation indicators, plume mass estimates, and fate and transport modeling). The molecular analyses demonstrated that microorganisms capable of both metabolic and cometabolic degradation of 1,4‐dioxane were present throughout the groundwater plume, whereas the CSIA data provided supporting evidence of biodegradation. 1,4‐Dioxane biomarkers were present and abundant throughout the 1,4‐dioxane plume, and our biomarkers tracked the plume with reasonable accuracy. Evidence also suggests that THF‐driven cometabolic biodegradation as well as catabolic 1,4‐dioxane biodegradation were active at this site. These data supplemented the traditional lines of evidence approaches, which demonstrated that 1,4‐dioxane attenuation was occurring across the groundwater plume and that nondestructive physical processes alone did not account for the observed 1,4‐dioxane attenuation. This MLOE framework combining new and traditional analyses demonstrates that this site has a significant capacity for intrinsic biodegradation of 1,4‐dioxane. ©2016 Wiley Periodicals, Inc.     

Applying the triple bottom line: Telework and the environment

The “triple bottom line” approach emphasizes not only economic goals, but social and environmental objectives as well. The “telework” option—in which employees work from home or a satellite office rather than from a central location—would appear to advance all three of these aims. But a close look at the specifics of teleworking makes clear that more data are needed to determine its ultimate impact. Moreover, despite its apparent advantages, teleworking is gaining acceptance less quickly than might be expected. For these reasons, telework offers a fascinating case study in the difficulties of applying the triple bottom line concept.© 1999 John Wiley & Sons, Inc.     

Temporal Changes in Allele Frequencies and a Population's History of Severe Bottlenecks

Monitoring temporal changes in genetic variation has been suggested as a means of determining if a population has experienced a demographic bottleneck. Simulations have shown that the variance in allele frequencies over time ( F ) can provide reasonable estimates of effective population size ( N_e ). This relationship between F and N_e suggests that changes in allele frequencies may provide a way to determine the severity of recent demographic bottlenecks experienced by a population. We examined allozyme variation in experimental populations of the eastern mosquitofish ( Gambusia holbrooki ) to evaluate the relationship between the severity of demographic bottlenecks and temporal variation in allele frequencies. Estimates of F from both the fish populations and computer simulations were compared to expected rates of drift. We found that different methods for estimating F had little effect on the analysis. The variance in estimates of F was large among both experimental and simulated populations experiencing similar demographic bottlenecks. Temporal changes in allele frequencies suggested that the experimental populations had experienced bottlenecks, but there was no relationship between observed and expected values of F . Furthermore, genetic drift was likely to be underestimated in populations experiencing the most severe bottlenecks. The weak relationship between F and bottleneck severity is probably due to both sampling error associated with the number of polymorphic loci examined and the loss of alleles during the bottlenecks. For populations that may have experienced severe bottlenecks, caution should be used in making evolutionary interpretations or management recommendations based on temporal changes in allele frequencies.