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1.
Larry G. Felix Randy L. Merritt Kent Duncan 《Journal of the Air & Waste Management Association (1995)》2013,63(9):1075-1085
At the Monticello station, operated by the Texas Utilities Generating Company, lignite coal obtained locally in Titus and Hopkins Counties fuels each of the three units. Units 1 and 2 are identical 575-MW Combustion Engineering (CE) boilers, each of which discharges its effluent to a 36- compartment shake/deflate cleaned baghouse paralleled with four electrostatic precipitators (ESP). Unit 3 is a larger boiler and is followed by an ESP and a scrubber. The Unit 1 and 2 baghouses were designed to clean 80 percent of the flue gas. Since startup, these baghouses have regularly experienced flange-to-flange pressure drops in excess of 10 in. H2O, with large opacity spikes caused by ash bleeding through the bags after compartment cleanings. Because of higher-than-expected pressure drop, the baghouses receive only about 45-50 percent of the flue gas. Analysis has shown the Monticello lignite ash significantly differs from most other coal ashes. Testing has shown that the Monticello ash is not filtered effectively by many "standard" bag materials. However, this testing indicates that there are fabrics that show promise of eliminating the ash bleedthrough with little pressure drop penalty. Testing has also shown that injection of low concentrations (10-15 ppm) of ammonia (NH3) into the flue gas significantly decreases ash bleedthrough, so that with NH3 injection "standard" bag materials may perform adequately. Currently, fullcompartment testing of four fabrics, with and without NH3 injection, is under way at the Unit 1 baghouse. The research conducted at the Monticello station is reviewed in this paper and the encouraging results from the full-compartment tests are presented. 相似文献
2.
Merritt Polk 《Sustainability Science》2014,9(4):439-451
Transdisciplinarity is often presented as a way to effectively use scientific research to contribute to societal problem solving for sustainability. The aim of this paper is to critically explore this statement. This is done in two ways. First, a literature survey of transdisciplinary research is used to identify the assumptions that underlie the positive relationship between transdisciplinarity and societal problem solving for sustainability. This mapping identifies the claim that in-depth participation of users and the integration of relevant knowledge from both practice and research in real-world problem contexts produce socially robust results that contribute to sustainability. Second, the ability to live up to this claim is presented and discussed in five case study projects from Mistra Urban Futures, a transdisciplinary center in Göteborg, Sweden. The conclusions show that transdisciplinary processes, which fulfill the above conditions, do produce different types of socially robust knowledge, but this does not necessarily result in the ability to influence change in a sustainable direction. This instead creates a paradox in that the participation of stakeholders and the integration of knowledge from diverse sources require spaces that are both embedded in and insulated from practice and science proper. Such spaces produce results that are not easily aligned with sector-based target groups and formal policy processes. Institutionalizing transdisciplinarity in a boundary organization therefore solves some problems regarding participation and balanced problem ownership. However, it also creates new, hybrid problems, regarding knowledge transfer and scalability, which bridge the boundaries and challenge the praxis of planning and policy making. 相似文献
3.
Imad A. Khalek Matthew G. Blanks Patrick M. Merritt Barbara Zielinska 《Journal of the Air & Waste Management Association (1995)》2013,63(8):987-1001
The U.S. Environmental Protection Agency (EPA) established strict regulations for highway diesel engine exhaust emissions of particulate matter (PM) and nitrogen oxides (NOx) to aid in meeting the National Ambient Air Quality Standards. The emission standards were phased in with stringent standards for 2007 model year (MY) heavy-duty engines (HDEs), and even more stringent NOX standards for 2010 and later model years. The Health Effects Institute, in cooperation with the Coordinating Research Council, funded by government and the private sector, designed and conducted a research program, the Advanced Collaborative Emission Study (ACES), with multiple objectives, including detailed characterization of the emissions from both 2007- and 2010-compliant engines. The results from emission testing of 2007-compliant engines have already been reported in a previous publication. This paper reports the emissions testing results for three heavy-duty 2010-compliant engines intended for on-highway use. These engines were equipped with an exhaust diesel oxidation catalyst (DOC), high-efficiency catalyzed diesel particle filter (DPF), urea-based selective catalytic reduction catalyst (SCR), and ammonia slip catalyst (AMOX), and were fueled with ultra-low-sulfur diesel fuel (~6.5 ppm sulfur). Average regulated and unregulated emissions of more than 780 chemical species were characterized in engine exhaust under transient engine operation using the Federal Test Procedure cycle and a 16-hr duty cycle representing a wide dynamic range of real-world engine operation. The 2010 engines’ regulated emissions of PM, NOX, nonmethane hydrocarbons, and carbon monoxide were all well below the EPA 2010 emission standards. Moreover, the unregulated emissions of polycyclic aromatic hydrocarbons (PAHs), nitroPAHs, hopanes and steranes, alcohols and organic acids, alkanes, carbonyls, dioxins and furans, inorganic ions, metals and elements, elemental carbon, and particle number were substantially (90 to >99%) lower than pre-2007-technology engine emissions, and also substantially (46 to >99%) lower than the 2007-technology engine emissions characterized in the previous study.Implications:?Heavy-duty on-highway diesel engines equipped with DOC/DPF/SCR/AMOX and fueled with ultra-low-sulfur diesel fuel produced lower emissions than the stringent 2010 emission standards established by the U.S. Environmental Protection Agency. They also resulted in significant reductions in a wide range of unregulated toxic emission compounds relative to older technology engines. The increased use of newer technology (2010+) diesel engines in the on-highway sector and the adaptation of such technology by other sectors such as nonroad, displacing older, higher emissions engines, will have a positive impact on ambient levels of PM, NOx, and volatile organic compounds, in addition to many other toxic compounds. 相似文献
4.
Khalek IA Bougher TL Merritt PM Zielinska B 《Journal of the Air & Waste Management Association (1995)》2011,61(4):427-442
As part of the Advanced Collaborative Emissions Study (ACES), regulated and unregulated exhaust emissions from four different 2007 model year U.S. Environmental Protection Agency (EPA)-compliant heavy-duty highway diesel engines were measured on an engine dynamometer. The engines were equipped with exhaust high-efficiency catalyzed diesel particle filters (C-DPFs) that are actively regenerated or cleaned using the engine control module. Regulated emissions of carbon monoxide, nonmethane hydrocarbons, and particulate matter (PM) were on average 97, 89, and 86% lower than the 2007 EPA standard, respectively, and oxides of nitrogen (NOx) were on average 9% lower. Unregulated exhaust emissions of nitrogen dioxide (NO2) emissions were on, average 1.3 and 2.8 times higher than the NO, emissions reported in previous work using 1998- and 2004-technology engines, respectively. However, compared with other work performed on 1994- to 2004-technology engines, average emission reductions in the range of 71-99% were observed for a very comprehensive list of unregulated engine exhaust pollutants and air toxic contaminants that included metals and other elements, elemental carbon (EC), inorganic ions, and gas- and particle-phase volatile and semi-volatile organic carbon (OC) compounds. The low PM mass emitted from the 2007 technology ACES engines was composed mainly of sulfate (53%) and OC (30%), with a small fraction of EC (13%) and metals and other elements (4%). The fraction of EC is expected to remain small, regardless of engine operation, because of the presence of the high-efficiency C-DPF in the exhaust. This is different from typical PM composition of pre-2007 engines with EC in the range of 10-90%, depending on engine operation. Most of the particles emitted from the 2007 engines were mainly volatile nuclei mode in the sub-30-nm size range. An increase in volatile nanoparticles was observed during C-DPF active regeneration, during which the observed particle number was similar to that observed in emissions of pre-2007 engines. However, on average, when combining engine operation with and without active regeneration events, particle number emissions with the 2007 engines were 90% lower than the particle number emitted from a 2004-technology engine tested in an earlier program. 相似文献
5.
Field and laboratory experiments were conducted to examine the effects of road salt (NaCI) on stream macroinvertebrates. Field studies investigated leaf litter processing rates and functional feeding group composition at locations upstream and downstream from point source salt inputs in two Michigan, USA streams. Laboratory studies determined the effects of increasing NaCl concentrations on aquatic invertebrate drift, behavior, and survival. Field studies revealed that leaves were processed faster at upstream reference sites than at locations downstream from road salt point source inputs. However, it was sediment loading that resulted in partial or complete burial of leaf packs, that affected invertebrate activity and confounded normal leaf pack colonization. There were no significant differences that could be attributed to road salt between upstream and downstream locations in the diversity and composition of invertebrate functional feeding groups. Laboratory drift and acute exposure studies demonstrated that drift of Gammarus (Amphipoda) may be affected by NaCl at concentrations greater than 5000 mg/l for a 24-h period. This amphipod and two species of limnephilid caddisflies exhibited a dose response to salt treatments with 96-h LC50 values of 7700 and 3526 mg NaCl/l, respectively. Most other invertebrate species and individuals were unaffected by NaCl concentrations up to 10,000 mg/l for 24 and 96 h, respectively. 相似文献
6.
Amniotic fluid cholinesterases tested on polyacrylamide gel and rapidly adhering cell analysis were compared in their efficiency at diagnosing fetal neural tube defects in three cases where the alphafetoprotein results were equivocal. While rapidly adhering cells were also equivocal, the cholinesterases consistently gave a clear indication of fetal abnormality. 相似文献
7.
8.
Habitat Assessment of Non-Wadeable Rivers in Michigan 总被引:1,自引:0,他引:1
Habitat evaluation of wadeable streams based on accepted protocols provides a rapid and widely used adjunct to biological
assessment. However, little effort has been devoted to habitat evaluation in non-wadeable rivers, where it is likely that
protocols will differ and field logistics will be more challenging. We developed and tested a non-wadeable habitat index (NWHI)
for rivers of Michigan, where non-wadeable rivers were defined as those of order ≥5, drainage area ≥1600 km2, mainstem lengths ≥100 km, and mean annual discharge ≥15 m3/s. This identified 22 candidate rivers that ranged in length from 103 to 825 km and in drainage area from 1620 to 16,860
km2. We measured 171 individual habitat variables over 2-km reaches at 35 locations on 14 rivers during 2000–2002, where mean
wetted width was found to range from 32 to 185 m and mean thalweg depth from 0.8 to 8.3 m. We used correlation and principal
components analysis to reduce the number of variables, and examined the spatial pattern of retained variables to exclude any
that appeared to reflect spatial location rather than reach condition, resulting in 12 variables to be considered in the habitat
index. The proposed NWHI included seven variables: riparian width, large woody debris, aquatic vegetation, bottom deposition,
bank stability, thalweg substrate, and off-channel habitat. These variables were included because of their statistical association
with independently derived measures of human disturbance in the riparian zone and the catchment, and because they are considered
important in other habitat protocols or to the ecology of large rivers. Five variables were excluded because they were primarily
related to river size rather than anthropogenic disturbance. This index correlated strongly with indices of disturbance based
on the riparian (adjusted R2 = 0.62) and the catchment (adjusted R2 = 0.50), and distinguished the 35 river reaches into the categories of poor (2), fair (19), good (13), and excellent (1).
Habitat variables retained in the NWHI differ from several used in wadeable streams, and place greater emphasis on known characteristic
features of larger rivers. 相似文献
9.
We used methods from EPA's Environmental Monitoring and Assessment Program (EMAP) to assess the regional status of streams within the Coast Range ecoregion of Washington State. Study objectives were: to determine the ecological condition of wadable, 1st-order through 3rd-order streams; to provide information for the development of water quality biological criteria; and to determine the applicability of EMAP-derived methods in Washington. Stream condition was assessed using EMAP indicators for habitat (chemical and physical) and biology (invertebrate and vertebrate assemblages). EMAP's probability survey was used to select 75 1st through 3rd-order stream sites from the USGS 1:100,000 series hydrographic layer. Of these, 45 sites were sampled. Multivariate techniques were used to identify community types and related physical and chemical habitat. Overall, about 25% of the sites were rated least-impacted. Most impacts were associated with non-point source pollution, mainly forestry practices. The R-EMAP method was a successful tool for assessment of regional status and ecological integrity; however, in order to use it for biological criteria development in Washington State, the method would require some modification to complement the current state protocols. 相似文献
10.
Wendy S. Merritt Brendan Patch V. Ratna Reddy Geoffrey J. Syme 《Environment, Development and Sustainability》2016,18(2):315-346
Over the last four decades, the Indian government has been investing heavily in watershed development (WSD) programmes that are intended to improve the livelihoods of rural agrarian communities and maintain or improve natural resource condition. Given the massive investment in WSD in India, and the recent shift from micro-scale programmes (<500 ha) to meso-scale (~5000 ha) clusters, robust methodological frameworks are needed to measure and analyse impacts of interventions across landscapes as well as between and within communities. In this paper, the sustainable livelihoods framework is implemented using Bayesian networks (BNs) to develop models of drought resilience and household livelihoods. Analysis of the natural capital component model provides little evidence that watershed development has influenced household resilience to drought and indicators of natural capital, beyond an increased area of irrigation due to greater access to groundwater. BNs have proved a valuable tool for implementing the sustainable livelihoods framework in a retrospective evaluation of implemented WSD programmes. Many of the challenges of evaluating watershed interventions using BNs are the same as for other analytical approaches. These are reliance on retrospective studies, identification and measurement of relevant indicators and isolating intervention impacts from contemporaneous events. The establishment of core biophysical and socio-economic indicators measured through longitudinal household surveys and monitoring programmes will be critical to the success of BNs as an evaluation tool for meso-scale WSD. 相似文献