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101.
Winston T. Luke Paul Kelley Barry L. Lefer James Flynn Bernhard Rappenglück Michael Leuchner Jack E. Dibb Luke D. Ziemba Casey H. Anderson Martin Buhr 《Atmospheric environment (Oxford, England : 1994)》2010,44(33):4068-4080
Concentrations of CO, SO2, NO, NO2, and NOY were measured atop the University of Houston's Moody Tower supersite during the 2006 TexAQS-II Radical and Aerosol Measurement Project (TRAMP). The lowest concentrations of all primary and secondary species were observed in clean marine air in southerly flow. SO2 concentrations were usually low, but increased dramatically in sporadic midday plumes advected from sources in the Houston Ship Channel (HSC), located NE of the site. Concentrations of CO and NOx displayed large diurnal variations in keeping with their co-emission by mobile sources in the Houston Metropolitan Area (HMA). CO/NOx emission ratios of 5.81 ± 0.94 were observed in the morning rush hour. Nighttime concentrations of NOx (NOx = NO + NO2) and NOY (NOY = NO + NO2 + NO3 + HNO3 + HONO + 21N2O5 + HO2NO2 + PANs + RONO2 + p-NO3? + …) were highest in winds from the NNW-NE due to emission from mobile sources. Median ratios of NOx/NOY were approximately 0.9 overnight, reflecting the persistence and/or generation of NOZ (NOZ = NOY ? NOx) species in the nighttime Houston boundary layer, and approached unity in the morning rush hour. Daytime concentrations of NOx and NOY were highest in winds from the HSC. NOx/NOY ratios reached their minimum values (median ca 0.63) from 1300 to 1500 CST, near local solar noon, and air masses often retained enough NOx to sustain additional O3 formation farther downwind. HNO3 and PANs comprised the dominant NOZ species in the HMA, and on a median basis represented 17–20% and 12–15% of NOY, respectively, at midday. Concentrations of HNO3, PANs, and NOZ, and fractional contributions of these species to NOY, were at a maximum in NE flow, reflecting the source strength and reactivity of precursor emissions in the HSC. As a result, daytime O3 concentrations were highest in air masses with HSC influence. Overall, our findings confirm the impact of the HSC as a dominant source region within the HMA. A comparison of total NOY measurements with the sum of measured NOY species (NOYi = NOx + HNO3 + PANs + HONO + p-NO3?) yielded excellent overall agreement during both day ([NOY](ppb) = ([NOYi](ppb)11.03 ± 0.16) ? 0.42; r2 = 0.9933) and night ([NOY](ppb) = ([NOYi](ppb)11.01 ± 0.16) + 0.18; r2 = 0.9975). A similar comparison between NOY–NOx concentrations and the sum of NOZi (NOZi = HNO3 + PANs + HONO + p-NO3?) yielded good overall agreement during the day ([NOZ](ppb) = ([NOZi](ppb)11.01 ± 0.30) + 0.044 ppb; r2 = 0.8527) and at night ([NOZ](ppb) = ([NOZi](ppb)11.12 ± 0.69) + 0.16 ppb; r2 = 0.6899). Median ratios of NOZ/NOZi were near unity during daylight hours but increased to approximately 1.2 overnight, a difference of 0.15–0.50 ppb. Differences between NOZ and NOZi rarely exceeded combined measurement uncertainties, and variations in NOZ/NOZi ratios may have resulted solely from errors in conversion efficiencies of NOY species and changes in NOY composition. However, nighttime NOZ/NOZi ratios and the magnitude of NOZ ? NOZi differences were generally consistent with recent observations of ClNO2 in the nocturnal Houston boundary layer. 相似文献
102.
Winston Chow Leonard Levin Michael Miller Richard Myhre 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1391-1398
As the time approaches for the U.S. Environmental Protection Agency (EPA) to evaluate whether risks from electric utility trace substance emissions are of concern, attention is focused on research to clarify the many issues surrounding this topic. Accordingly, more than 230 representatives of industry, government, international research and academic institutions, equipment manufacturers, and engineering service firms attended the Second International Conference on Managing Hazardous Air Pollutants, which was held in Washington, D.C., on July 13–15,1993. Sponsored by the Electric Power Research Institute (EPRI) in cooperation with the EPA, U.S. Department of Energy (DOE), PowerGen, Coal Research Division of the International Energy Agency, and Canadian Electrical Association, the conference featured more than 50 presentations that both asked and answered questions about utility emission sources, the atmospheric fate of emitted substances, health and environmental studies, risk assessment, and control technologies. The diversity of the audience produced a stimulating exchange of findings, interpretations, and assessments of remaining uncertainties. This exchange provided valuable direction for ongoing research activities worldwide. 相似文献
103.
Roger C Prince Richard E BareRobert M Garrett Matthew J GrossmanCopper E Haith Lois G KeimKenneth Lee Graham J HoltomPatrick Lambert Gary A Sergy Edward H Owens Chantal C Guénette 《Spill Science & Technology Bulletin》2003,8(3):303-312
The application of slow-release and soluble fertilizers proved to be an effective and environmentally benign way of stimulating oil biodegradation on an Arctic shoreline. Fertilizer application to the surface of the beach delivered nutrients to the oiled sediment beneath the beach surface. There was no significant run-off of this fertilizer to either the nearshore water or to unfertilized plots, and there were no adverse toxicological effects of the fertilizer application. The fertilizer application was followed by an increase in oxygen consumption and carbon dioxide evolution from the beach, increased microbial biomass, and significantly greater biodegradation of oil on the plots that had received fertilizer. The rate of oil biodegradation was approximately doubled over the course of a year by fertilizer applications in the first two months after the spill.Simple test kits proved adequate to monitor the fertilizer-application process in the field in a time frame that would allow the application process to be fine-tuned during treatment on a real spill. Simple test kits and portable instrumentation were useful in demonstrating the initial success of the bioremediation strategy. 相似文献
104.
Harry R. Compton George R. Prince Scott C. Fredericks Christopher D. Gussman 《补救:环境净化治理成本、技术与工艺杂志》2003,13(3):21-37
The United States Environmental Protection Agency/Environmental Response Team (EPA/ERT) has been supporting and implementing the use of phytoremediation to remediate dissolved phase organic compounds at Superfund sites since March 1996. Since then, ERT has applied phytoremediation field plots, both pilot and full scale, to a variety of field conditions. These active sites vary considerably as to depth to groundwater, groundwater transmissivity, contaminant concentrations, contaminant hydrophobicity, climate, planting design, plant selection, planting technique, and type of monitoring. Here we compare the literature and discuss lessons learned at five Superfund sites. Current maintenance and monitoring techniques at these sites are also discussed with recommendations for the maintenance and monitoring of similar sites in the future. © 2003 Wiley Periodicals, Inc. 相似文献
105.
106.
Caulerpa paspaloides (Bory) Greville were collected during the winter and summer (1978 to 1979) from the Florida Keys, USA. Thalli collected during the winter photosynthesized more efficiently at low light intensities (Ic<1, Ik=38 Exm-2xs-1) than did thalli collected in the summer (Ic=13, Ik=111 Exm-2xs-1). Summer thalli exhibited higher Pmax values (2.20 mgO2xg-1 dry wtxh-1) than winter thalli (1.70 mg O2xg-1 dry wtxh-1). Rates of rhizome elongation and frond initiation were strongly inhibited by winter temperatures. The maximum lethal temperature for summer thalli was 37° to 38°C as measured by both growth and photosynthesis. No evidence of nitrogen or phosphorus limitation was found. Relatively minor reductions in salinity (3S) resulted in significant increases in rhizome apex motality. Results indicate that low winter temperatures are responsible for reduced winter growth rates previously reported for the Key Largo population. Increased photosynthetic efficiency at low light intensities and preferential maintenance of rhizome elongation over frond initiation appear to allow this tropical macroalga to optimize growth and survival during the winter. 相似文献
107.
Raymond Prince 《Journal of Environmental Economics and Management》1985,12(2):179-180
The sign of the adjustment to the riskless discount rate for environmental risk depends on whether the price of avoiding the consequences of the externality is seen as reducing expected net benefits or increasing expected costs. The conclusion is that the risk adjustment is positive when the externality is defined as reducing expected net benefits. 相似文献
108.
Shelley E. R. Hoover Mark L. Winston Benjamin P. Oldroyd 《Behavioral ecology and sociobiology》2005,59(2):278-284
In most social insect colonies, workers do not attempt to lay eggs in the presence of a queen. However, in the honey bee (Apis mellifera), a rare phenotype occurs in which workers activate their ovaries and lay large numbers of male eggs despite the presence of a fecund queen. We examined the proximate mechanisms by which this ‘anarchistic’ behaviour is expressed. We tested the effects of brood and queen pheromones on retinue attraction and worker ovary activation using caged worker bees. We found no difference between the anarchistic and wild type queen pheromones in the retinue response elicited in either wild type or anarchistic workers. Further, we found that anarchistic queens produce a pheromone blend that is as effective at inhibiting ovary activation as the wild type queen pheromone. However, anarchistic workers are less inhibited by queen pheromones than their wild type counterparts, in a dose-dependent manner. These results show that the anarchistic phenomenon is not due to changes in the production of queen pheromones, but rather is due in part to a shift in the worker response to these queen-produced signals. In addition, we demonstrate the dose-dependent nature of the effect of queen pheromones on honey bee worker ovary activation. 相似文献
109.
110.
Effects of four decades of fire manipulation on woody vegetation structure in Savanna 总被引:2,自引:0,他引:2
Higgins SI Bond WJ February EC Bronn A Euston-Brown DI Enslin B Govender N Rademan L O'Regan S Potgieter AL Scheiter S Sowry R Trollope L Trollope WS 《Ecology》2007,88(5):1119-1125
The amount of carbon stored in savannas represents a significant uncertainty in global carbon budgets, primarily because fire causes actual biomass to differ from potential biomass. We analyzed the structural response of woody plants to long-term experimental burning in savannas. The experiment uses a randomized block design to examine fire exclusion and the season and frequency of burn in 192 7-ha experimental plots located in four different savanna ecosystems. Although previous studies would lead us to expect tree density to respond to the fire regime, our results, obtained from four different savanna ecosystems, suggest that the density of woody individuals was unresponsive to fire. The relative dominance of small trees was, however, highly responsive to fire regime. The observed shift in the structure of tree populations has potentially large impacts on the carbon balance. However, the response of tree biomass to fire of the different savannas studied were different, making it difficult to generalize about the extent to which fire can be used to manipulate carbon sequestration in savannas. This study provides evidence that savannas are demographically resilient to fire, but structurally responsive. 相似文献