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481.
Silvano Fares Jeong-Hoo Park Elena Ormeno Drew R. Gentner Megan McKay Francesco Loreto John Karlik Allen H. Goldstein 《Atmospheric environment (Oxford, England : 1994)》2010,44(28):3404-3412
The Citrus genus includes a large number of species and varieties widely cultivated in the Central Valley of California and in many other countries having similar Mediterranean climates. In the summer, orchards in California experience high levels of tropospheric ozone, formed by reactions of volatile organic compounds (VOC) with oxides of nitrogen (NOx). Citrus trees may improve air quality in the orchard environment by taking up ozone through stomatal and non-stomatal mechanisms, but they may ultimately be detrimental to regional air quality by emitting biogenic VOC (BVOC) that oxidize to form ozone and secondary organic aerosol downwind of the site of emission. BVOC also play a key role in removing ozone through gas-phase chemical reactions in the intercellular spaces of the leaves and in ambient air outside the plants. Ozone is known to oxidize leaf tissues after entering stomata, resulting in decreased carbon assimilation and crop yield. To characterize ozone deposition and BVOC emissions for lemon (Citrus limon), mandarin (Citrus reticulata), and orange (Citrus sinensis), we designed branch enclosures that allowed direct measurement of fluxes under different physiological conditions in a controlled greenhouse environment. Average ozone uptake was up to 11 nmol s?1 m?2 of leaf. At low concentrations of ozone (40 ppb), measured ozone deposition was higher than expected ozone deposition modeled on the basis of stomatal aperture and ozone concentration. Our results were in better agreement with modeled values when we included non-stomatal ozone loss by reaction with gas-phase BVOC emitted from the citrus plants. At high ozone concentrations (160 ppb), the measured ozone deposition was lower than modeled, and we speculate that this indicates ozone accumulation in the leaf mesophyll. 相似文献
482.
Seong Suk Park Kathleen Kozawa Scott Fruin Steve Mara Ying-Kuang Hsu Chris Jakober 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1046-1056
ABSTRACT Fuel-based emission factors for 143 light-duty gasoline vehicles (LDGVs) and 93 heavy-duty diesel trucks (HDDTs) were measured in Wilmington, CA using a zero-emission mobile measurement platform (MMP). The frequency distributions of emission factors of carbon monoxide (CO), nitrogen oxides (NOx), and particle mass with aerodynamic diameter below 2.5 μm (PM2.5) varied widely, whereas the average of the individual vehicle emission factors were comparable to those reported in previous tunnel and remote sensing studies as well as the predictions by Emission Factors (EMFAC) 2007 mobile source emission model for Los Angeles County. Variation in emissions due to different driving modes (idle, low- and high-speed acceleration, low- and high-speed cruise) was found to be relatively small in comparison to intervehicle variability and did not appear to interfere with the identification of high emitters, defined as the vehicles whose emissions were more than 5 times the fleet-average values. Using this definition, approximately 5% of the LDGVs and HDDTs measured were high emitters. Among the 143 LDGVs, the average emission factors of NOx, black carbon (BC), PM2.5, and ultrafine particle (UFP) would be reduced by 34%, 39%, 44%, and 31%, respectively, by removing the highest 5% of emitting vehicles, whereas CO emission factor would be reduced by 50%. The emission distributions of the 93 HDDTs measured were even more skewed: approximately half of the NOx and CO fleet-average emission factors and more than 60% of PM2.5, UFP, and BC fleet-average emission factors would be reduced by eliminating the highest-emitting 5% HDDTs. Furthermore, high emissions of BC, PM2.5, and NOx tended to cluster among the same vehicles.
IMPLICATIONS This study presents the characterization of on-road vehicle emissions in Wilmington, CA, by sampling individual vehicle plumes. Approximately 5% of the vehicles were high emitters, whose emissions were more than 5 times the fleet-average values. These high emitters were responsible for 30% and more than 50% of the average emission factors of LDGVs and HDDVs, respectively. It is likely that as the overall fleet becomes cleaner due to more stringent regulations, a small fraction of the fleet may contribute a growing and disproportionate share of the overall emissions. Therefore, long-term changes in on-road emissions need to be monitored. 相似文献
483.
Yong-Woon Lee Changkook Ryu Woong-Jin Lee Young-Kwon Park 《Journal of Material Cycles and Waste Management》2011,13(3):165-172
Wood pellet is a densified fuel with homogeneous physical properties suitable for use at various scales in domestic and industrial
furnaces. A wood pellet stove is a small-scale furnace for domestic heat production that can replace conventional oil or gas
boilers. Since the fuel properties of wood pellet are very different from those of oil or gas, the design of a wood pellet
stove requires profound understanding of solid fuel combustion as well as of gas flow mixing and reactions. Due to limitations
on the height of an installed furnace (~1 m), poor design of the furnace, air supply, fume extraction, or the heat exchanger
may lead to excessive CO emissions or low energy efficiency. This study evaluated the design of an existing wood pellet stove
with 30,000 kcal/h capacity, using experimental and computational techniques in order to optimize the furnace design. The
results show that it is critical to minimize unused furnace volume and to enhance gaseous mixing for reduced CO emissions
while maintaining sufficiently high temperatures for fast oxidation. 相似文献
484.
Jeong Huy Ko Yeon-Ho Kwak Kyung-Seun Yoo Jong-Ki Jeon Sung Hoon Park Young-Kwon Park 《Journal of Material Cycles and Waste Management》2011,13(3):173-179
Experiments were performed in order to investigate the possibility for the development of catalysts for low-temperature selective
catalytic reduction (SCR) using municipal waste char and RDF byproduct. Physical and chemical activations, using water, and
HCl and KOH, were employed to increase the catalytic activities. The characteristics of the activated catalysts were investigated
using N2 adsorption–desorption and FT-IR. The catalysts activated chemically using basic treatment showed higher NO
x
removal efficiencies than those activated physically or chemically using acidic treatment. The de-NO
x
performance of the activated catalysts was dependent on the chemical properties, such as oxygen functional groups as well
as physical properties, such as specific surface area and pore volume. In order to investigate the effect of MnO
x
, which has been reported to be efficient for the removal of NO
x
in low-temperature SCR processes, the chemically activated catalyst was impregnated with manganese. The Mn-impregnated catalyst
had the highest NO
x
conversion at all of the temperatures tested in this study. 相似文献
485.
The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity
based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the
prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters
in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort,
and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning
cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths <50 m and was concentrated particularly
in inshore waters (<20 m) in spring. In autumn, the spawning output was mainly from the autumn-spawning cohort, which comprised
but a small number of individuals. In winter, the major spawning group again consisted of the large females from the spring-spawning
cohort, and spawning increased in the oceanic waters (>50 m). These results suggest that mature female M. endeavouri and M. ensis move offshore (>40 m) by May and July, respectively, and return to shallow waters (<35 m) in July and November, respectively.
The monthly reproduction patterns of both species in the “effective spawning” area showed that the major spawning season for
M. endeavouri is August to October and that for M. ensis is September to December.
Received: 19 February 1999 / Accepted: 18 June 2000 相似文献
486.
Haque Md. Morshedul Niloy Nahin Mostofa Nayna Omme K. Fatema Konica J. Quraishi Shamshad B. Park Ji-Hyung Kim Kyoung-Woong Tareq Shafi M. 《Environmental science and pollution research international》2020,27(34):42582-42599
Environmental Science and Pollution Research - The Ganges River is one of the biggest transboundary streams in the Indian sub-continent. The significant part of this waterway channel drains one of... 相似文献
487.
Jinyoung Park 《环境政策》2018,27(4):686-711
South Korea and Japan have been unwaveringly committed to a nuclear-focused energy supply system despite the contested nature of that technology and the Fukushima accident in 2011. The socio-political consequences of four nuclear-related facilities (Ulju, Gyeongju, Futaba, and Rokkasho) are explored through the lens of social peripheralisation. This framework suggests that nuclear facilities will migrate to communities that are geographically remote, economically marginal, politically powerless, culturally defensive, and environmentally degraded. Nuclear infrastructures in the four cases are imposed on peripheral regions, impairing not only the structure of local economies and political power, but also creating a discriminative structure in terms of social and environmental inequality. Peripheralisation suggests a deeper dynamic by which pro-nuclear attitudes become ‘locked in’ socially and culturally so that communities come to depend on the very processes that made them peripheral. Community dynamics, subnational struggles, and contests over local power relations may determine the future of nuclear power. 相似文献
488.
Factors dominating stratification cycle and seasonal water quality variation in a Korean estuarine reservoir 总被引:4,自引:0,他引:4
Lee YG Kang JH Ki SJ Cha SM Cho KH Lee YS Park Y Lee SW Kim JH 《Journal of environmental monitoring : JEM》2010,12(5):1072-1081
A comprehensive monitoring program was conducted during 2005-2007 to investigate seasonal variations of hydrologic stability and water quality in the Yeongsan Reservoir (YSR), located at the downstream end of the Yeongsan River, Korea. A principal component analysis (PCA) was performed to identify factors dominating the seasonal water quality variation from a large suite of measured data--11 physico-chemical parameters from 48 sampling sites. The results showed that three principal components explained approximately 62% of spatio-seasonal water quality variation, which are related to stratifications, pollutant loadings and resultant eutrophication, and the advective mixing process during the episodic rainfall-runoff events. A comparison was then made between YSR and an upstream freshwater reservoir (Damyang Reservoir, DYR) in the same river basin during an autumn season. It was found that the saline stratification and pollutant input from the upstream contributed to greater concentrations of nutrients and organic matter in YSR compared to DYR. In YSR, saline stratification in combination with thermal stratification was a dominant cause of the longer period (for two consecutive seasons) of hypoxic conditions at the reservoir bottom. The results presented here will help better understand the season- and geography-dependent characteristics of reservoir water quality in Asian Monsoon climate regions such as Korea. 相似文献
489.
Ki-Hyun Kim Janice P. Susaya Chan Goo Park Jung-Hoon Uhm Jin Hur 《Environmental monitoring and assessment》2013,185(8):6353-6378
In this research, the quality of drinking well waters from 14 districts around Seoul metropolitan city, Korea was assessed by measuring a number of parameters with established guideline (e.g., arsenic, fluoride, nitrate nitrogen, benzene, 1,2-dichloroethene, dichloromethane, copper, and lead) and without such criteria (e.g., hardness, chloride ion, sulfate ion, ammonia nitrogen, aluminum, iron, manganese, and zinc). Physical parameters such as evaporation residue (or total dissolved solids) and turbidity were also measured. The importance of each parameter in well waters was examined in terms of the magnitude and exceedance frequency of guideline values established by international (and national) health agencies. The results of this study indicate that among the eight parameters with well-established guidelines (e.g., WHO), arsenic and lead (guideline value of 0.01 mg?L?1 for both) recorded the highest exceedance frequency of 18 and 16 well samples ranging in 0.06–136 and 2–9 mg?L?1, respectively. As such, a number of water quality parameters measured from many well waters in this urban area were in critical levels which require immediate attention for treatment and continuous monitoring. 相似文献
490.
Rittenour WR Park JH Cox-Ganser JM Beezhold DH Green BJ 《Journal of environmental monitoring : JEM》2012,14(3):766-774
Traditional methods of assessing fungal exposure have been confounded by a number of limiting variables. The recent utilization of molecular methods such as internal transcribed spacer (ITS) sequencing of ribosomal RNA genes has provided improved insight into the diversity of fungal bioaerosols in indoor, outdoor and occupational environments. However, ITS analyses may also be confounded by a number of methodological limitations. In this study, we have optimized this technology for use in occupational or environmental studies. Three commonly used DNA extraction methodologies (UltraClean Soil kit, High Pure PCR Template kit, and EluQuik/DNeasy kit) were compared in terms of sensitivity and susceptibility to PCR inhibitors in dust for three common fungal bioaerosols, Aspergillus versicolor, Rhizopus microsporus and Wallemia sebi. Environmental dust samples were then studied using each extraction methodology and results were compared to viable culture data. The extraction methods differed in terms of their ability to efficiently extract DNA from particular species of fungi (e.g. Aspergillus versicolor). In addition, the ability to remove PCR inhibitors from dust samples was most effective using the soil DNA extraction kit. The species composition varied greatly between ITS clone libraries generated with the different DNA extraction kits. However, compared to viable culture data, ITS clone libraries included additional fungal species that are incapable of growth on solid culture medium. Collectively, our data indicated that DNA extraction methodologies used in ITS sequencing studies of occupational or environmental dust samples can greatly influence the fungal species that are detected. 相似文献