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Significant changes have been observed in the hydrology of Central Rift Valley (CRV) lakes in Ethiopia, East Africa as a result of both natural processes and human activities during the past three decades. This study applied an integrated approach (remote sensing, hydrologic modelling, and statistical analysis) to understand the relative effects of natural processes and human activities over a sparsely gauged CRV basin. Lake storage estimates were calculated from a hydrologic model constructed without inputs from human impacts such as water abstraction and compared with satellite-based (observed) lake storage measurements to characterize the magnitude of human-induced impacts. A non-parametric Mann–Kendall test was used to detect the presence of climatic trends (e.g. a decreasing or increasing trends in precipitation), while the Standard Precipitation Index (SPI) analysis was used to assess the long-term, inter-annual climate variability within the basin. Results indicate human activities (e.g. abstraction) significantly contributed to the changes in the hydrology of the lakes, while no statistically significant climatic trend was seen in the basin, however inter-annual natural climate variability, extreme dryness, and prolonged drought has negatively affected the lakes. The relative contributions of natural and human-induced impacts on the lakes were quantified and evaluated by comparing hydrographs of the CRV lakes. Lake Abiyata has lost ~6.5 m in total lake height between 1985 and 2006, 70% (~4.5 m) of the loss has been attributed to human-induced causes, whereas the remaining 30% is related to natural climate variability. The relative impact analysis utilized in this study could potentially be used to better plan and create effective water-management practices in the basin and demonstrates the utility of this integrated methodology for similar studies assessing the relative natural and human-induced impacts on lakes in data sparse areas. Copyright © 2015 John Wiley & Sons, Ltd.

With impending regulation of mercury from coal-fired power plants, it is important to concentrate efforts on the most mature retrofit control technologies. Injection of powdered activated carbon (PAC) has been deemed the most mature technology, but has until recently only been demonstrated in bench- and pilot-scale experiments. This paper presents some of the results from a field evaluation program of sorbent injection upstream of existing particulate control devices (PCDs). An important component of the field demonstration program is to characterize the fly ash that results from injection of PAC upstream of a baghouse or electrostatic precipitator (ESP). Leaching analyses were performed on fly ash collected during two different field demonstrations; one fly ash was derived from bituminous coal and the other from a subbituminous coal. Several widely accepted leaching methods were used in order to assess the stability of the ash by-product in landfill situations; other ash characterization tests were also used in the study. Little or no detectable Hg was leached as a result of the various leaching protocols. The subbituminous ash conformed to the ASTM C-618 standard for Class C fly ash, but did not pass the Foam Index Test that is also required for sale of this ash for use in concrete formulation.

One of the challenges facing both regulators and the regulated community in dealing with air toxic emissions and their control, is the need to accurately measure and characterize these emissions. The current technology for measuring metallic components in emission streams requires manual sample extraction, recovery and preservation of the sample, and finally analysis of the sample using laboratory instrumentation. While these techniques are capable of analyzing trace concentrations of metals with adequate accuracy and precision, they all have numerous drawbacks due to their complexity and the fact that they do not provide real-time data. This paper describes two programs that ADA Technologies has undertaken to develop measurement technology for toxic metals in combustion flue gas. These research programs are directed at overcoming limitations of the current state-of-the-art measurement systems in order to meet the needs for accurate and reliable monitoring of toxic metal emissions from stationary sources. Both programs focus on the development of instrumentation for the detection and quantization of trace levels of air toxic metals in combustion gas environments. The instruments are being designed to function as continuous, real-time, on-line analyzers that can serve as parts of a feedback process to control air toxic metals emissions.

There is a lack of information on plant response to multifactor environmental variability including the interactive response to temperature and atmospheric humidity. These two factors are almost always confounded because saturated vapor pressure increases exponentially with temperature, and vapor pressure deficit (VPD) could have a large impact on plant growth. In this study using climate controlled mini-greenhouses, we examined the interacting influence of temperature and VPD on long-term growth of tall fescue (Festuca arundinacea Schreb), a cool season grass. From past studies it was expected that growth of tall fescue would decline with warmer temperatures over the range of 18.5-27 degrees C, but growth actually increased markedly with increasing temperature when VPD was held constant. In contrast, growth declined in experiments where tall fescue was exposed to increasing VPD and temperature was held constant at 21 degrees C. The inhibited growth appears to be in response to a maximum transpiration rate that can be supported by the tall fescue plants. The sensitivity to VPD indicates that if VPD remains stable in future climates as it has in the past, growth of tall fescue could well be stimulated rather than decreased by global warming in temperate climate zones.

As part of a larger investigation on freeze-thaw durability of masonry segmental retaining wall (SRW) units, specimens of various geometries were extensively evaluated for their resonant frequency prior to freeze-thaw exposure. These pretest trials were conducted to assess the applicability of the impact resonance method on these specimens, to identify factors affecting test result interpretation, and to obtain initial values for future comparison with values after freeze-thaw cycling. The importance of correctly identifying resonant frequencies corresponding to different modes of vibration of the specimen is highlighted, and methods to achieve this in the laboratory are discussed. The effects of specimen moisture content variations, temperature, and sampling parameters on resonant frequency are also presented.