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Brady D. Lee William A. Apel Amber R. Miller 《Journal of the Air & Waste Management Association (1995)》2013,63(9):1068-1074
ABSTRACT Research was performed to demonstrate the removal of carbon tetrachloride (CT) using compost biofilters operated under methanogenic conditions. Biofilters were operated at an empty-bed residence time of 2.8 minutes using nitrogen as the atmosphere. Hydrogen and carbon dioxide were supplied as an electron donor and carbon source, respectively, during acclimation of the bed medium microbes. Once methanogenesis was demonstrated, CT flow to the biofilter was established. Biofilters were operated over a CT concentration range from 20 to 700 ppbv for 6 months. Bed medium microbes were able to remove up to 75% of the inlet CT. At excessively high CT concentrations (>500 ppmv), methane production and hydrogen utilization by the bed medium microbes appeared to be inhibited. CT removal by the biofilter decreased when the hydrogen supply was removed from the biofilter inlet, indicating that hydrogen acted as the electron donor for reductive dechlorination. The removal efficiency and relatively low empty bed residence times demonstrated by these laboratory-scale biofilters indicate that anaerobic biofiltration of CT may be a feasible full-scale process. 相似文献
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Amber Spackman Jones Jeffery S. Horsburgh Nancy O. Mesner Ronald J. Ryel David K. Stevens 《Journal of the American Water Resources Association》2012,48(6):1258-1275
Abstract: The determination of sediment and nutrient loads is typically based on the collection and analysis of grab samples. The frequency and regularity of traditional sampling may not provide representation of constituent loading, particularly in systems with flashy hydrology. At two sites in the Little Bear River, Utah, continuous, high‐frequency turbidity was used with surrogate relationships to generate estimates of total phosphorus and total suspended solids concentrations, which were paired with discharge to estimate annual loads. The high frequency records were randomly subsampled to represent hourly, daily, weekly, and monthly sampling frequencies and to examine the effects of timing, and resulting annual load estimates were compared to the reference loads. Higher frequency sampling resulted in load estimates that better approximated the reference loads. The degree of bias was greater at the more hydrologically responsive site in the upper watershed, which required a higher sampling frequency than the lower watershed site to achieve the same level of accuracy in estimating the reference load. The hour of day and day of week of sampling impacted load estimation, depending on site and hydrologic conditions. The effects of sampling frequency on the determination of compliance with a water quality criterion were also examined. These techniques can be helpful in determining necessary sampling frequency to meet the objectives of a water quality monitoring program. 相似文献
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Potential Economic Benefits of Adapting Agricultural Production Systems to Future Climate Change 总被引:2,自引:0,他引:2
Tony Prato Qiu Zeyuan Gregory Pederson Dan Fagre Lindsey E. Bengtson Jimmy R. Williams 《Environmental management》2010,45(3):577-589
Potential economic impacts of future climate change on crop enterprise net returns and annual net farm income (NFI) are evaluated
for small and large representative farms in Flathead Valley in Northwest Montana. Crop enterprise net returns and NFI in an
historical climate period (1960–2005) and future climate period (2006–2050) are compared when agricultural production systems
(APSs) are adapted to future climate change. Climate conditions in the future climate period are based on the A1B, B1, and
A2 CO2 emission scenarios from the Intergovernmental Panel on Climate Change Fourth Assessment Report. Steps in the evaluation include:
(1) specifying crop enterprises and APSs (i.e., combinations of crop enterprises) in consultation with locals producers; (2)
simulating crop yields for two soils, crop prices, crop enterprises costs, and NFIs for APSs; (3) determining the dominant
APS in the historical and future climate periods in terms of NFI; and (4) determining whether NFI for the dominant APS in
the historical climate period is superior to NFI for the dominant APS in the future climate period. Crop yields are simulated
using the Environmental/Policy Integrated Climate (EPIC) model and dominance comparisons for NFI are based on the stochastic
efficiency with respect to a function (SERF) criterion. Probability distributions that best fit the EPIC-simulated crop yields
are used to simulate 100 values for crop yields for the two soils in the historical and future climate periods. Best-fitting
probability distributions for historical inflation-adjusted crop prices and specified triangular probability distributions
for crop enterprise costs are used to simulate 100 values for crop prices and crop enterprise costs. Averaged over all crop
enterprises, farm sizes, and soil types, simulated net return per ha averaged over all crop enterprises decreased 24% and
simulated mean NFI for APSs decreased 57% between the historical and future climate periods. Although adapting APSs to future
climate change is advantageous (i.e., NFI with adaptation is superior to NFI without adaptation based on SERF), in six of
the nine cases in which adaptation is advantageous, NFI with adaptation in the future climate period is inferior to NFI in
the historical climate period. Therefore, adaptation of APSs to future climate change in Flathead Valley is insufficient to
offset the adverse impacts on NFI of such change. 相似文献
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S. Kent Hoekman Amber Broch Curtis Robbins Richard Purcell 《International Journal of Greenhouse Gas Control》2010,4(1):44-50
A laboratory-scale reactor system was built and operated to demonstrate the feasibility of catalytically reacting carbon dioxide (CO2) with renewably-generated hydrogen (H2) to produce methane (CH4) according to the Sabatier reaction: CO2 + 4H2 → CH4 + 2H2O. A cylindrical reaction vessel packed with a commercial methanation catalyst (Haldor Topsøe PK-7R) was used. Renewable H2 produced by electrolysis of water (from solar- and wind-generated electricity) was fed into the reactor along with a custom blend of 2% CO2 in N2, meant to represent a synthetic exhaust mixture. Reaction conditions of temperature, flow rates, and gas mixing ratios were varied to determine optimum performance. The extent of reaction was monitored by real-time measurement of CO2 and CH4. Maximum conversion of CO2 occurred at 300–350 °C. Approximately 60% conversion of CO2 was realized at a space velocity of about 10,000 h?1 with a molar ratio of H2/CO2 of 4/1. Somewhat higher total CO2 conversion was possible by increasing the H2/CO2 ratio, but the most efficient use of available H2 occurs at a lower H2/CO2 ratio. 相似文献
36.
Seth Payton Greg Lindsey Jeff Wilson John R. Ottensmann Joyce Man 《Journal of Environmental Planning and Management》2008,51(6):717-736
This paper measures the benefits of the urban forest by examining its effect on housing prices. A Geographic Information System is used to develop a measure of the urban forest, the Normalised Difference Vegetation Index, from satellite imagery and to construct other variables from a variety of sources. Spatial hedonic housing price models for the Indianapolis/Marion County area are estimated. The models indicate that greener vegetation around a property has a positive, significant effect on housing price, holding everything else constant. This effect is dominated by measures at the neighborhood level. These findings indicate that property owners value the urban forest, at least in part, by the premium they pay to live in neighborhoods with greener, denser vegetation. These findings also indicate that public action to maintain and enhance the urban forest may be warranted. Planners and urban foresters can use these findings to inform public and policy debates over urban forestry programs and proposals. 相似文献
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