The effect of sodium chloride on the dissolution of calcium silicate hydrate gels

The use of cement based materials will be widespread in the long-term management of radioactive materials in the United Kingdom. One of the applications could be the Nirex reference vault backfill (NRVB) as an engineered barrier within a deep geological repository. NRVB confers alkaline conditions, which would provide a robust chemical barrier through the control of the solubility of some key radionuclides, enhanced sorption and minimised corrosion of steel containers. An understanding of the dissolution of C-S-H gels in cement under the appropriate conditions (e.g., saline groundwaters) is necessary to demonstrate the expected evolution of the chemistry over time and to provide sufficient cement to buffer the porewater conditions for the required time. A programme of experimental work has been undertaken to investigate C-S-H gel dissolution behaviour in sodium chloride solutions and the effect of calcium/silicon ratio (C/S), temperature and cation type on this behaviour. Reductions in calcium concentration and pH values were observed with samples equilibrated at 45 degrees C compared to those prepared at 25 degrees C. The effect of salt cation type on salt-concentration dependence of the dissolution of C-S-H gels was investigated by the addition of lithium or potassium chloride in place of sodium chloride for gels with a C/S of 1.0 and 1.8. With a C/S of 1.0, similar increases in dissolved calcium concentration with increasing ionic strength were recorded for the different salts. However, at a C/S of 1.8, anomalously high calcium concentrations were observed in the presence of lithium.     

Persistence of diflubenzuron and bay sir 8514 in natural and sterile sandy loam and organic soils

Abstract

Disappearance rates of 10 ppm technical diflubenzuron (N(((4‐chloro‐phenyl)amino)carbonyl)‐2,6‐diflurobenzamide, Dimilin^®) and BAY SIR 8514 (2‐chloro‐N(((4‐trifluoromethoxyphenyl)amino)carbonyl)benzamide) applied on quartz sand to natural sandy loam and muck soils were significantly greater than for the corresponding sterilized soils, e.g. 47–51% vs. 68–87% BAY SIR 8514 and 2–12% vs. 80–87% diflubenzuron remaining at 12 wk, indicating that soil microorganisms play a major role in their degradation. Kinetic analysis of the data based on a first order dependence on the insecticide concentration showed that the rate constants for these disappearance reactions decreased with time.     

AN ECONOMIC ASSESSMENT OF GROUND WATER RECHARGE IN THE TUCSON BASIN1

ABSTRACT: Bringing water from Colorado River via the Central Arizona Project was perceived as the sole solution for Tucson Basin's water problem. Soon after Central Arizona Project's water arrived in Tucson in 1992, its quality provoked a quarrel over its use for potable purposes. A significant outcome of that quarrel was the enactment of the 1995 Proposition 200. The Proposition 200 precludes the use of Central Arizona Project's water for potable purposes, unless it is treated. Yet, it encourages using it for non‐potable purposes and for replenishing the Tucson aquifer through recharge. This paper examines the economic issues involved in utilizing Central Arizona Project's water for recharge. Four planning scenarios were designed to measure and compare the costs and benefits with and without Central Arizona Project's water recharge. Cost‐benefit analysis was utilized to measure recharge costs and benefits and to derive a rough estimate of cost savings from preventing land subsidence. The results indicate that the institutional requirements can be met with Central Arizona Project's water recharge. The economic benefits from reducing pumping cost and saving groundwater are not economically significant. Yet, when combining the use of Central Arizona Project's water for recharge and non‐potable purposes, it demonstrates positive net economic benefits.     

Framing an independent,integrated and evidence-based evaluation of the state of Australia's biophysical and human environments

A new approach was developed for Australia's 2011 national State of the Environment (SoE) report to integrate the assessment of biophysical and human elements of the environment. A Common Assessment and Reporting Framework (CARF) guided design and implementation, responding to jurisdictional complexity, outstanding natural diversity and ecosystem values, high levels of cultural and heritage diversity, and a paucity of national-scale data. The CARF provided a transparent response to the need for an independent, robust and evidence-based national SoE report. We conclude that this framework will be effective for subsequent national SoE assessments and other integrated national-scale assessments in data-poor regions.     

Hot,Salty Water: A Confluence of Issues in Managing Stormwater Runoff for Urban Streams

Research increasingly highlights cause and effect relationships between urbanization and stream conditions are complex and highly variable across physical and biological regions. Research also demonstrates stormwater runoff is a key causal agent in altering stream conditions in urban settings. More specifically, thermal pollution and high salt levels are two consequences of urbanization and subsequent runoff. This study describes a demonstration model populated with data from a high gradient headwaters stream. The model was designed to explain surface water‐groundwater dynamics related to salinity and thermal pollution. Modeled scenarios show long‐term additive impacts from salt application and suggest reducing flow rates, as stormwater management practices are typically designed to do, have the potential to greatly reduce salt concentrations and simultaneously reduce thermal pollution. This demonstration model offers planners and managers reason to be confident that stormwater management efforts can have positive impacts.     

An exploration of place as a process: The case of Jackson Hole, WY

A variety of theoretical positions and frameworks have been advanced to account for how places become “places”—in other words, how places become meaningful. Most existing frameworks share the idea that a place is a complex concept, given life by people attaching meaning to a physical setting in a variety of ways. This paper explores how places evolve as ever-shifting points of meaning that mark changes in people's lives in response to a variety of influences. Data collected from in-depth personal interviews in and around Jackson, Wyoming, are used to explore the conceptualization of place as a process, rather than a static entity. Three key themes or dimensions that were frequently described by interviewees are examined: (1) life stage/course, (2) searching for a feeling, and (3) commitment to a place. Not only did some respondents describe what made places important to them (the components, such as social ties, or favorite activities), they also described how these attributes worked together to create and maintain place meanings over the course of their lives. During the interviews, it was noted that these dimensions and processes were expressed explicitly as well as implicitly.     

Paradigms for parasite conservation

Parasitic species, which depend directly on host species for their survival, represent a major regulatory force in ecosystems and a significant component of Earth's biodiversity. Yet the negative impacts of parasites observed at the host level have motivated a conservation paradigm of eradication, moving us farther from attainment of taxonomically unbiased conservation goals. Despite a growing body of literature highlighting the importance of parasite‐inclusive conservation, most parasite species remain understudied, underfunded, and underappreciated. We argue the protection of parasitic biodiversity requires a paradigm shift in the perception and valuation of their role as consumer species, similar to that of apex predators in the mid‐20th century. Beyond recognizing parasites as vital trophic regulators, existing tools available to conservation practitioners should explicitly account for the unique threats facing dependent species. We built upon concepts from epidemiology and economics (e.g., host‐density threshold and cost‐benefit analysis) to devise novel metrics of margin of error and minimum investment for parasite conservation. We define margin of error as the risk of accidental host extinction from misestimating equilibrium population sizes and predicted oscillations, while minimum investment represents the cost associated with conserving the additional hosts required to maintain viable parasite populations. This framework will aid in the identification of readily conserved parasites that present minimal health risks. To establish parasite conservation, we propose an extension of population viability analysis for host–parasite assemblages to assess extinction risk. In the direst cases, ex situ breeding programs for parasites should be evaluated to maximize success without undermining host protection. Though parasitic species pose a considerable conservation challenge, adaptations to conservation tools will help protect parasite biodiversity in the face of an uncertain environmental future.     

Impacts of hydroelectric development on riparian vegetation in the Sierra Nevada region,California, USA

Fourteen streams in the Sierra Nevada in the USA were sampled to determine whether diversions of streamflow for hydroelectric development had caused significant changes in riparian vegetation. Several streams showed significant differences in vegetation cover, community composition, or community structure between pairs of diverted and undiverted reaches. On some streams, environmental conditions rather than streamflow diversions may have been responsible for vegetation differences. Streams in the Sierra Nevada respond individualistically to diversions. Prediction of vegetation responses must take into consideration environmental characteristics of specific stream reaches.     

ECONOMIC RESOURCE MULTIPLIERS FOR REGIONAL IMPACT ANALYSIS1

ABSTRACT: Tradeoffs between regional economic development and resource use is a question often confronting local decisionmakers. A resource-interindustry model can be used to depict the interrelationships between regional economic sectors as to household income and/or employment and resource use. A resource-interindustry model was developed for Humboldt and Lander Counties in Nevada which shows the tradeoffs between regional household income (wages, salaries, profits, and rents) and/or employment and water usage. Water income and water employment multipliers can be ranked, enabling decisionmakers to realize sectors which require greatest regional water usage to regional household income and/or employment.