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Golden Triangle, NC, United States

Prabhu V.,Illinois Institute of Technology | Kim T.,Illinois Institute of Technology | Khakpour Y.,Illinois Institute of Technology | Serre S.D.,Us Epa National Risk Management Research Laboratory | Clack H.L.,Illinois Institute of Technology
Fuel Processing Technology | Year: 2012

Abstract Removal of mercury from coal-derived flue gas by injecting powdered sorbents often involves a substantial portion removed within an electrostatic precipitator (ESP). The present investigation uses a lab-scale ESP to assess the potential for injected sorbents to collect preferentially on discharge electrode wires. Such preferential collection would increase the adsorption capacity of the accumulated dust cake on the discharge electrodes, increasing their potential contribution to the total mercury removal performance of the ESP. The lab-scale results involving various fly ashes and both carbon-based and non-carbon mercury sorbents confirm that powdered activated carbon is enriched in the discharge electrode dust cake relative to its concentration in suspension in the gas flow. Other results explore the effects of applied ESP polarity, voltage, and power, percent PAC added to the fly ash, and total particulate matter loading entering the ESP on the collection behavior. © 2011 Elsevier B.V. All rights reserved. Source

Li C.,Zhejiang University | Yang Y.J.,Us Epa National Risk Management Research Laboratory | Yu J.,Zhejiang University | Zhang T.-Q.,Zhejiang University | And 2 more authors.
Water Environment Research | Year: 2012

It is well known that model-building of chlorine decay in real water distribution systems is difficult because chlorine decay is influenced by many factors (e.g., bulk water demand, pipe-wall demand, piping material, flow velocity, and residence time). In this paper, experiments were run to investigate the kinetic model of chlorine decay and the formation model of trihalomethanes (THMs) in pilot-scale water distribution systems. Experimental results show that the rate constants of chlorine decay, including wall decay and bulk decay, increasing with temperature. Moreover, the kinetic model of chlorine decay and the formation model of THMs describe experiment data of pilot-scale water distribution systems. The effect of different piping material on chlorine decay and THMs formation were also investigated. The rate constants of chlorine decay are ranked in order: stainless steel pipe, ductile iron pipe, and last, polyethelene pipe because wall decay is the largest in stainless steel pipe than that in other piping material. Correspondingly, the rate of THMs formation follows the order of stainless steel pipe, ductile iron pipe, and last, polyethelene pipe because of less chlorine in bulk water reacting with the trihalomethane formation potential (THMFP). Source

Lunetta R.S.,Us Epa National Exposure Research Laboratory | Schaeffer B.A.,US Ecology | Stumpf R.P.,East-West Center | Keith D.,US Ecology | And 2 more authors.
Remote Sensing of Environment | Year: 2014

Inland waters across the United States (US) are at potential risk for increased outbreaks of toxic cyanobacteria blooms events resulting from elevated water temperatures and extreme hydrologic events attributable to climate change and increased nutrient loadings associated with intensive agricultural practices. Current monitoring efforts are limited in scope due to resource limitations, analytical complexity, and data integration efforts. The goals of this study were to validate an algorithm for satellite imagery that could potentially be used to monitor surface cyanobacteria events in near real-time to provide a compressive monitoring capability for freshwater lakes (>. 100. ha). The algorithm incorporated narrow spectral bands specific to the European Space Agency's (ESA's) MEdium Resolution Imaging Spectrometer (MERIS) instrument that were optimally oriented at phytoplankton pigment absorption features including phycocyanin at 620. nm. A validation of derived cyanobacteria cell counts was performed using available in situ data assembled from existing monitoring programs across eight states in the eastern US over a 39-month period (2009-2012). Results indicated that MERIS provided robust estimates for low (10,000-109,000 cells/mL) and very high (>. 1,000,000 cells/mL) cell enumeration ranges (approximately 90% and 83%, respectively). However, the results for two intermediate ranges (110,000-299,000 and 300,000-1,000,000 cells/mL) were substandard, at approximately 28% and 40%, respectively. The confusion associated with intermediate cyanobacteria cell count ranges was largely attributed to the lack of available taxonomic data and distinction of natural counting units for the in situ measurements that would have facilitated conversions between cell counts and cell volumes. The results of this study document the potential for using MERIS-derived cyanobacteria cell count estimates to monitor freshwater lakes (>. 100. ha) across the eastern US. © 2014. Source

Novick K.,Indiana University Bloomington | Brantley S.,U.S. Department of Agriculture | Brantley S.,University of Minnesota | Miniat C.F.,U.S. Department of Agriculture | And 2 more authors.
Agricultural and Forest Meteorology | Year: 2014

Multiple data streams from a new flux tower located in complex and heterogeneous terrain at the Coweeta Hydrologic Laboratory (North Carolina, USA) were integrated to identify periods of advective flow regimes. Drainage flows were expected a priori, due to the location of the measurement site at the base of a long, gently-sloping valley. Drainage flow was confirmed by examining vertical profile measurements of wind direction and by estimating vertical advection fluxes. The vertical advection flux of CO2 was most significant in early morning (000-0600h) during the growing season, when it averaged ~5μmolm-2s-1. Horizontal advection flux of CO2 was not directly measured in this study; however, an expected exponential relationship between nocturnal ecosystem respiration (RE) and air temperature was recovered when horizontal advection of CO2 was assumed to be negatively correlated to vertical advection, or when data were limited to periods when measured vertical advection fluxes were small. Taken together, these data imply the presence of a negative horizontal advection CO2 flux during nocturnal periods characterized by positive vertical advection of CO2. Daytime periods were characterized by consistent anabatic (up-valley) flows in mid- to late-morning (0500-1200h) and consistent katabatic (down-valley) flows in the afternoon. A combination of above-canopy flux profile measurements, energy balance closure estimates, and flux footprint estimates suggest that during periods of up-valley wind flow, the flux footprint frequently exceeds the ecosystem dimensions, and horizontal advection fluxes related to landscape heterogeneity were a significant component of the total ecosystem flux of CO2. We used sap flux from individual trees beneath the tower to explore diurnal patterns in stomatal conductance in order to evaluate gapfilling approaches for the unreliable morning data. The relationship between stomatal conductance and vapor pressure deficit was similar in morning and afternoon periods, and we conclude that gapfilling morning data with models driven by afternoon data is a reasonable approach at this site. In general, results were consistent with other studies showing that the advection and wind flow regimes in complex terrain are highly site specific; nonetheless, the site characterization strategy developed here, when used together with independent estimates of components of the ecosystem carbon flux, could be generally applied in other sites to better understand the contribution of advection to the total ecosystem flux. © 2013 Elsevier B.V. Source

Novick K.A.,U.S. Department of Agriculture | Novick K.A.,Indiana University | Walker J.,Us Epa National Risk Management Research Laboratory | Chan W.S.,Oregon State University | And 3 more authors.
Agricultural and Forest Meteorology | Year: 2013

A new class of enclosed path gas analyzers suitable for eddy covariance applications combines the advantages of traditional closed-path systems (small density corrections, good performance in poor weather) and open-path systems (good spectral response, low power requirements), and permits estimates of instantaneous gas mixing ratio. Here, the extent to which these advantages are realized in field deployment is assessed, with a focus on the suitability of such an analyzer (the EC155, manufactured by Campbell Scientific) for long-term flux measurements in a new flux monitoring site in the southern Appalachians (NC, USA). The scalar-vertical velocity co-spectra for CO2 fluxes measured with the EC155 were similar to those measured with a co-located open-path system. When humidity was high, attenuation of the EC155 water vapor fluxes for non-dimensional frequencies greater than ~2 was noted, though results from an ogive analysis suggest that eddies operating on these time scales contributed <2% of the total turbulent flux in this tall forest ecosystem. Inertial sub-range decay of the vertical velocity-scalar co-spectra generally conformed to a -7/3 power law during near-neutral atmospheric stability conditions, supporting the use of an analytical spectral correction approach to the raw measured fluxes. The EC155 fluxes computed directly from instantaneous mixing ratio agreed with will those calculated from mass-density concentration measurements, provided density terms for temperature, water vapor, and pressure were applied. Biases were observed when the EC155 flux records were compared to those measured with the open-path system. These differences were related to wind angle of attack and to an estimate of apparent fluxes related to instrument self-heating, and the biases were minimized after the application of a friction velocity filter. Finally, the EC155 considerably outperformed open-path analyzers during adverse weather conditions favorable to fog development, which occur frequently in the study site. © 2013. Source

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