Laboratory analog and numerical study of groundwater flow and solute transport in a karst aquifer with conduit and matrix domains

New mathematical and laboratory methods have been developed for simulating groundwater flow and solute transport in karst aquifers having conduits imbedded in a porous medium, such as limestone. The Stokes equations are used to model the flow in the conduits and the Darcy equation is used for the flow in the matrix. The Beavers–Joseph interface boundary conditions are adopted to describe the flow exchange at the interface boundary between the two domains. A laboratory analog is used to simulate the conduit and matrix domains of a karst aquifer. The conduit domain is located at the bottom of the transparent plexiglas laboratory analog and glass beads occupy the remaining space to represent the matrix domain. Water flows into and out of the two domains separately and each has its own supply and outflow reservoirs. Water and solute are exchanged through an interface between the two domains. Pressure transducers located within the matrix and conduit domains of the analog provide data that is processed and stored in digital format. Dye tracing experiments are recorded using time-lapse imaging. The data and images produced are analyzed by a spatial analysis program. The experiments provide not only hydraulic head distribution but also capture solute front images and mass exchange measurements between the conduit and matrix domains. In the experiment, we measure and record pressures, and quantify flow rates and solute transport. The results present a plausible argument that laboratory analogs can characterize groundwater water flow, solute transport, and mass exchange between the conduit and matrix domains in a karst aquifer. The analog validates the predictions of a numerical model and demonstrates the need of laboratory analogs to provide verification of proposed theories and the calibration of mathematical models.     

Characterization of monitor recycling in Seattle, Washington

With the rapid growth of electronic waste (e-waste), policies that aim to effectively manage this waste stream have been introduced globally in recent years. Seattle, Washington, has been on the forefront of introducing policies to divert e-waste from the landfills and maximize recycling. With the introduction of the Take-it-Back-Network, a solid recycling infrastructure has existed in the Greater Seattle region since 2003. In 2009, the E-Cycle Washington program took into effect and now allows recyclers to offer free recycling of certain e-waste to households and small entities. Although policies to divert e-waste from the landfill to reuse and recycling is effective, there is also a need to analyze the current regional recycling infrastructure’s capacity to handle changing equipment and material quantities. This study aims to characterize the Seattle regional e-waste management capacity, with a focus on retired monitors as an example of a changing e-waste technology. We investigated waste computer monitor recycling in the Greater Seattle region, which includes the counties of King, Pierce, Snohomish, and Kitsap. Interviews were conducted on 20 collectors, 1 handler, and 2 processors to collect information on their business models, computer monitor management processes, and collection/processing quantities. Using this information, we summarize the material flows of end-of-life (EOL) cathode ray tube (CRT) and liquid crystal display (LCD) monitors in the region, both from the qualitative and quantitative perspective.     

Got a risk reduction strategy?

Process safety can be viewed as part of a triad that supports safety in a petrochemical facility. The other two parts are OSHA-type people safety (slips, falls, etc.) and industrial hygiene. The paper will look at process safety from a top down, plant centric view. Process safety can be distilled down to the basic concept of risk reduction. If we reduce risk, our facility will be safer. The obvious problem is that we have potential risks everywhere so how are we going to reduce all these risks to an acceptable level. Clearly we need a strategy or to use a less fancy word – a plan.Too many times it is easy to concentrate on certain aspects such as safety instrumented systems (SIS), layer of protection analysis (LOPA), behavioral safety, prevention, etc. and lose track of the whole picture of what risk reduction entails in a plant.This paper will look at risk reduction in a facility from a plant viewpoint and will cover the details and concepts of risk reduction across a wide spectrum of plant functionalities – safety climate and culture, process safety management, mechanical integrity and risk, layers of protection in risk reduction, loss of containment/hazard relationship, the risk reduction bow-tie diagram, developing a risk reduction strategy, risk reduction strategy elements, and sustainability.It will also discuss some key concepts in dealing with risk reduction in general.     

Nitrate reduction by green rusts modified with trace metals

A kinetic study of nitrate reduction by green rust (GR), a group of layered Fe(II)-Fe(III) hydroxide solids, was performed using a batch reactor system. The reduction rate of nitrate by GRs was affected by the anion content in the interlayer of GRs. GR containing F^- (GR-F) showed the fastest reduction rate while GR-SO₄ showed 9 times slower reaction rate than GR-F. The addition of 1 mM Pt or Cu to GR that contained 85 mM Fe(II) improved the reduction kinetics of nitrate by up to 200 times. Pt was an effective activating agent for all GRs. The sequential step reaction model that we proposed appropriately simulated the experimental data. The fastest nitrate reduction by GR-F with Pt was achieved at pH 9 among 7.5 to 11. At that condition, 1 mM nitrate transformed completely into ammonium within 23 min.     

Application of Wavelet Coherence Method to Investigate Karst Spring Discharge Response to Climate Teleconnection Patterns

The impact of climate teleconnections on the regional hydrometeorology has been well studied, but very little effort has been made to relate climate teleconnections with groundwater flow variation. In this study, we used a wavelet coherence method to analyze monthly climate indices, precipitation, and spring discharge data, and investigated the relation between major teleconnection patterns (the Arctic Oscillation, North Atlantic Oscillation, Pacific Decadal Oscillation, El Niño‐Southern Oscillation, and Indian Ocean Dipole) and karst hydrological process in Niangziguan Springs Basin, China. The results indicate precipitation and spring discharges correlate well with climate indices at intra‐ and inter‐annual time scales. Further, the climate indices are mainly correlated with precipitation at shorter periodicities, but correlated with spring discharge at longer scales. The difference reflects the modulation of karst aquifers on precipitation‐spring discharge during the processes of precipitation infiltration into the ground, and subsequent transformation into spring discharge. When teleconnection signals are transmitted into spring discharge via precipitation infiltration and groundwater propagation, some high‐frequency climatic signals are likely to be filtered, attenuated, and delayed, thus only low‐frequency climatic signals are preserved in spring discharge.     

Some Factors that Affect the Deposition Rates of Sulfur Dioxide and Similar Gases on Vegetation

The deposition of sulfur dioxide on growing vegetation is affected by diverse environmental factors, many of which undergo large diurnal and spatial variations. The aerodynamic resistance to vertical transfer in the surface boundary layer can be formulated in terms of the friction velocity, height of observation, vertical heat flux, and surface roughness. Also important are the resistance in the air layer closest to the surface elements and, in dry vegetation, the average stomatal resistance of the plants. The latter variable is among the most difficult to estimate, but over many agricultural field crops like those in the midwestern U.S., a typical minimum value of average stomatal resistance to SO₂ transfer is about 0.7 s cm^-1, as is indicated by various experimental data. The deposition velocity can be estimated as the inverse of the sum of the resistances of the layers, necessarily down to where the concentrations are zero; in the surface boundary layer, any of the various resistances might be dominant. Above the surface layer, the micrometeorological relationships are known with less certainty, but reasonable approximations indicate that during unstable conditions the resistance to transfer is very small at heights of several tens of meters and during stable conditions the aerodynamic resistance is very large aloft.     

Ozone Predictions in Atlanta,Georgia: Analysis of the 1999 Ozone Season

ABSTRACT

Ozone prediction has become an important activity in many U.S. ozone nonattainment areas. In this study, we describe the ozone prediction program in the Atlanta metropolitan area and analyze the performance of this program during the 1999 ozone-forecasting season. From May to September, a team of 10 air quality regulators, meteorologists, and atmospheric scientists made a daily prediction of the next-day maximum 8-hr average ozone concentration. The daily forecast was made aided by two linear regression models, a 3-dimensional air quality model, and the no-skill ozone persistence model. The team's performance is compared with the numerical models using several numerical indicators. Our analysis indicated that (1) the team correctly predicted next-day peak ozone concentrations 84% of the time, (2) the two linear regression models had a better performance than a 3-dimensional air quality model, (3) persistence was a strong predictor of ozone concentrations with a performance of 78%, and (4) about half of the team's wrong predictions could be prevented with improved meteorological predictions.     

Improving mental health status and coping abilities for long‐term unemployed youth using cognitive‐behaviour therapy based training interventions

This paper reports on immediate and long‐term well‐being outcomes for a group of long‐term unemployed youth who attended specially devised training courses based on the cognitive‐behaviour therapy (CBT) model. The courses were aimed specifically at improving the mental health of participants, and providing them with coping skills to deal better with the negative consequences of prolonged unemployment. Results for participants were compared with a waiting‐list, control group. Outcomes investigated were well‐being (psychological distress, self‐esteem, positive and negative affect), and coping behaviours (social support, self care, recreation, and cognitive coping strategies). Behavioural plasticity effects were also examined by comparing outcomes for participants who had higher distress scores prior to the course with participants who reported lower scores at that time. Immediate benefits were identified for both mental health and coping behaviours, and many of these benefits persisted into the long term. Participants with higher levels of pre‐course psychological distress improved more than their low distressed counterparts, supporting the behavioural plasticity hypothesis. Copyright © 1999 John Wiley & Sons, Ltd.     

Amendment of hydroxyapatite in reduction of tetrachloroethylene by zero-valent zinc: its rate enhancing effect and removal of Zn(II)

The effects of hydroxyapatite (HAP) on dechlorination of tetrachloroethylene (PCE) by zero-valent zinc (ZVZ) were examined in batch systems. PCE was primarily transformed to trichloroethylene by ZVZ, with 1,2-trans-dichloroethylene representing a minor product. Dechlorination of PCE was accelerated by the presence of HAP, and the pseudo-first order rate constants increased with increasing amount of HAP. Zn(II), mostly generated from oxidative dissolution of ZVZ by PCE, was effectively removed from the solution by HAP. Ion substitution, coprecipitation, and adsorption are proposed as the possible mechanisms for Zn(II) removal. These reactions appeared to occur simultaneously and the contribution of each reaction to overall removal of Zn(II) was primarily dependent on HAP loading at constant ZVZ loading. The results indicate that the use of HAP in combination with conventional zero-valent metals is promising in that it can achieve both degradation of organic contaminants and stabilization of inorganic contaminants.