Effects of hypoxia on biofilms and subsequently larval settlement of benthic invertebrates     

S.G. Cheung  C.Y.S. Chan  B.H.K. Po  A.L. Li  J.Y.S. Leung  J.W. Qiu  P.O. Ang  V. Thiyagarajan  P.K.S. Shin  J.M.Y. Chiu 《Marine pollution bulletin》2014

Biofilms on submerged surfaces are important in determining larval settlement of most marine benthic invertebrates. We investigated if exposure of biofilms to hypoxia would alter the larval settlement pattern and result in a shift in benthic invertebrate community structure in the field. Biofilms were first exposed to hypoxia or normoxia in laboratory microcosms for 7 days, and then deployed in the field for another 7 days to allow for larval settlement and recruitment to occur. Using terminal-restriction fragment length polymorphism of the 16S rRNA gene, this study showed that hypoxia altered the biofilm bacterial community composition, and the difference between the hypoxic and normoxic treatments increased with the time of exposure period. This study also demonstrated significantly different benthic invertebrate community structures as a result of biofilm exposure to hypoxia and that the hypoxic and normoxic treatments were dominated by Hydroides sp. and Folliculina sp., respectively.  相似文献   

Improved fog detection from satellite in the presence of clouds     

Jung-Moon Yoo  Myeong-Jae Jeong  Young Min Hur  Dong-Bin Shin 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(1):29-40

This study analyzes radiative effect of the higher clouds over the fog layer and presents the improvement of fog detection over the Korean peninsula, utilizing satellite data of the Multi-functional Transport SATellite (MTSAT)-1R and the MODerate resolution Imaging Spectroradiometer (MODIS) and the Look-Up Table (LUT) based on Radiative Transfer Model (RTM) simulations. Fog detection utilizing the satellite data from visible (0.68 µm) and infrared (3.75 µm and 10.8 µm) channels has been evaluated in comparison with ground-based observations over 52 meteorological stations in the Korean Peninsula from March 2006 to February 2007. The threshold values for fog sensing have been derived from the difference (i.e., T_3.7–11) in brightness temperature between 3.75 µm (T_3.7) and 10.8 µm (T₁₁) during day and night, and also from the reflectivity at 0.68 µm (R_0.68) in the daytime. In the twilight, however, the difference between the temperature values at 10.8 µm and their maximum within previous 15 days (i.e., T_11max-11) are used instead, because the 3.75 µm channel is inaccurate for the fog detection at dawn/dusk. The sensitivity of the T_3.7–11 values with respect to the clouds is investigated based on the cloud variables such as its height, optical thickness, and amount. The values of T_3.7–11 are the most sensitive to cloud height, followed by cloud optical thickness and effective radius, while R0.68 is insensitive to cloud height. The sensitivity is examined with various conditions of cloud phases and day/night. Sixteen cases among eighteen fog occurrences, which have been unable to be sensed by using only the conventional threshold values, are successfully detected with the additional LUT corrections, indicating a significant improvement. The method of fog detection in this study can be useful to the Communication, Ocean, and Meteorological Satellite (COMS) Meteorological Data Processing System (CMDPS) by reducing the cloud effect on fog sensing.  相似文献   

Aerodynamic Scaling for Estimating the Mean Height of Dense Canopies   总被引：1，自引：1，他引：0  

Taro Nakai  Akihiro Sumida  Kazuho Matsumoto  Ken’ichi Daikoku  Shin’ichi Iida  Hotaek Park  Mie Miyahara  Yuji Kodama  Alexander V. Kononov  Trofim C. Maximov  Hironori Yabuki  Toshihiko Hara  Takeshi Ohta 《Boundary-Layer Meteorology》2008,128(3):423-443

We used an aerodynamic method to objectively determine a representative canopy height, using standard meteorological measurements. The canopy height may change if the tree height is used to represent the actual canopy, but little work to date has focused on creating a standard for determining the representative canopy height. Here we propose the ‘aerodynamic canopy height’ h _a as the most effective means of resolving the representative canopy height for all forests. We determined h _a by simple linear regression between zero-plane displacement d and roughness length z ₀, without the need for stand inventory data. The applicability of h _a was confirmed in five different forests, including a forest with a complex canopy structure. Comparison with stand inventory data showed that h _a was almost equivalent to the representative height of trees composing the crown surface if the forest had a simple structure, or to the representative height of taller trees composing the upper canopy in forests with a complex canopy structure. The linear relationship between d and z ₀ was explained by assuming that the logarithmic wind profile above the canopy and the exponential wind profile within the canopy were continuous and smooth at canopy height. This was supported by observations, which showed that h _a was essentially the same as the height defined by the inflection point of the vertical profile of wind speed. The applicability of h _a was also verified using data from several previous studies.  相似文献   

Spatial distribution and comparative evaluation of phosphorus release rate in benthic sediments of an estuary dam     

Yongsik Song  Yong-Hoon Jeong  Chang-Min Shin  Dong-Heui Kwak 《国际泥沙研究》2022,37(3):355-369

A series of experiments and simulations were performed to ascertain the rate at which phosphorus is released using a water quality model in Saemangeum Lake, an artificially constructed lake located in an estuary. The general inflow of seawater once a day contributed to the formation of a halocline in the lake water, which caused variation in the vertical concentration of dissolved oxygen. The halocline was mainly observed in the deep downstream regions of Saemangeum Lake that are close to the op...  相似文献   

Relationship between the expansion of drylands and the intensification of Hadley circulation during the late twentieth century     

Sang-Hye Shin  Il-Ung Chung  Hyung-Jin Kim 《Meteorology and Atmospheric Physics》2012,118(3-4):117-128

The changes in coverage by arid climate and intensity of the Hadley circulation during the second half of the twentieth century were examined using observations and the multi-model ensemble (MME) mean of Twentieth-Century Coupled Climate Model (20C3M) simulations. It was found that the area of dry climate, which comprises steppe and desert climates following the K?ppen climate classification, expanded to an appreciable extent in observation and, to a lesser degree, in MME simulation. The areal extent of steppe climate (the outer boundary of arid climate) tends to encroach on the surrounding climate groups, which, in turn, feeds desert climate (the inner part of arid climate) and causes it to grow. This result indicates the importance of accurate prediction for climate regimes that border steppe climate. Concomitant with the expansion of drylands, the observed intensity of the Hadley cell is persistently enhanced, particularly during boreal winter, suggesting the validity of a self-induction of deserts through a positive bio-geophysical feedback (also known as Charney’s cycle). In comparison, the simulated Hadley circulation in the MME mean remains invariant in time. The current climate models, therefore, disagree with the observation in the long-term linkage between desertification and Hadley cell. Finally, the implication of such discrepancy is discussed as a possible guidance to improve models.  相似文献   

Sediment–well interaction during depressurization     

Hosung Shin  J. Carlos Santamarina 《Acta Geotechnica》2017,12(4):883-895

Depressurization gives rise to complex sediment–well interactions that may cause the failure of wells. The situation is aggravated when high depressurization is imposed on sediments subjected to an initially low effective stress, such as in gas production from hydrate accumulations in marine sediments. Sediment–well interaction is examined using a nonlinear finite element simulator. The hydro-mechanically coupled model represents the sediment as a Cam-Clay material, uses a continuous function to capture compressibility from low to high effective stress, and recognizes the dependency of hydraulic conductivity on void ratio. Results highlight the critical effect of hydro-mechanical coupling as compared to constant permeability models: A compact sediment shell develops against the screen, the depressurization zone is significantly smaller than the volume anticipated assuming constant permeability, settlement decreases, and the axial load on the well decreases; in the case of hydrates, gas production will be a small fraction of the mass estimated using a constant permeability model. High compressive axial forces develop in the casing within the production horizon, and the peak force can exceed the yield capacity of the casing and cause its collapse. Also tensile axial forces may develop in the casing above the production horizon as the sediment compacts in the depressurized zone and pulls down from the well. Well engineering should consider: slip joints to accommodate extensional displacement above the production zone, soft telescopic/sliding screen design to minimize the buildup of compressive axial force within the production horizon, and enlarged gravel pack to extend the size of the depressurized zone.  相似文献   

Baseline and distribution of organic pollutants and heavy metals in tidal creek sediments after Hurricane Sandy in the Meadowlands of New Jersey     

Francisco Artigas  Ji Meng Loh  Jin Young Shin  Joe Grzyb  Ying Yao 《Environmental Earth Sciences》2017,76(7):293

The relatively low cost of lands along with a privileged location near an urban center attracted industry to the Meadowlands of New Jersey and the absence of regulations resulted in vast amounts of industrial waste emitted into the air and dumped to nearby estuaries and marshlands. Hurricane Sandy created an unprecedented sea surge that overtopped berms and tide gates and extensively flooded approximately 22.8 km² of a low lying basin that includes Berry’s Creek, a tributary to the Hackensack River and well known for its legacy of high levels of contamination. The sea surge connected Berry’s Creek with eastern creeks that flow into the Hackensack River for several tidal cycles. The objectives of this study were to establish a baseline for organic pollutants and heavy metals post Superstorm Sandy, determine whether contaminants from highly contaminated areas moved to the eastern creeks during the surge and measure contaminant gradients around tide gates. Cadmium, mercury and chromium were the most abundant contaminants in sediments, and pollutants responsible for the highest ecological risk were Hg and polychlorinated biphenyls (PCBs). Concentrations of PCBs were higher in the western creeks and contrary to metals did not show concentration gradients from either side of tide gates. Massive export of contaminants from western to eastern creeks due to the surge was not apparent. The abundance of heavy metals in the vicinity of tide gates shows that they play a role in their distribution across the estuary.  相似文献   

“Spherulite-like” jadeite growth in shock-melt veins of the Novosibirsk H5/6 chondrite     

I.S. Bazhan  Shin Ozawa  M. Miyahara  E. Ohtani  K.D. Litasov 《Russian Geology and Geophysics》2017,58(1):12-19

The Novosibirsk H5/6 ordinary chondrite has signs of shock metamorphism, such as dark shock-melt veins (SMVs) crossing the chondrite host rock. The plagioclase composition grains (Ab₇₈An₁₄Or₇) with jadeite were found in the host-rock fragments inside the SMVs. Jadeite has an unusual radial-concentric spherulite-like microtexture. The spherulite-like jadeite formed from the molten plagioclase grain under high-pressure and high-temperature conditions during an impact event. The crystallization was accompanied by sodium-potassium differentiation between coexisting jadeite and residual melt. The PT-conditions of jadeite formation were estimated to be 3-14 GPa and 1400-2150 °C. Jadeite crystallization, Na-K differentiation, and the pressure-temperature estimates of jadeite formation in the Novosibirsk chondrite are very close to those in the Chelyabinsk LL5 chondrite. The spherulite-like microtexture and jadeite-glass coexistence, most likely, point to a high cooling rate of the SMVs at the pressure release stage of the metamorphic process.  相似文献   

Estimating ground-level particulate matter concentrations using satellite-based data: a review     

Minso Shin  Yoojin Kang  Seohui Park  Cheolhee Yoo  Lindi J. Quackenbush 《地理信息系统科学与遥感》2020,57(2):174-189

ABSTRACT

Particulate matter (PM) is a widely used indicator of air quality. Satellite-derived aerosol products such as aerosol optical depth (AOD) have been a useful source of data for ground-level PM monitoring. However, satellite-based approaches for PM monitoring have limitations such as impacts of cloud cover. Recently, many studies have documented advances in modeling for monitoring PM over the globe. This review examines recent papers on ground-level PM monitoring for the past 10 years focusing on modeling techniques, sensor types, and areas. Satellite-based retrievals of AOD and commonly used approaches for estimating PM concentrations are also briefly reviewed. Research trends and challenges are discussed based on the review of 130 papers. The limitations and challenges include spatiotemporal scale issues, missing values in satellite-based variables, sparse distribution of ground stations for calibration and validation, unbalanced distribution of PM concentrations, and difficulty in the operational use of satellite-based PM estimation models. The literature review suggests there is room for further investigating: 1) the spatial extension of PM monitoring to global scale; 2) the synergistic use of satellite-derived products and numerical model output to improve PM estimation accuracy, gap-filling, and operational monitoring; 3) the use of more advanced modeling techniques including data assimilations; 4) the improvement of emission data quality; and 5) short-term (hours to days) PM forecasts through combining satellite data and numerical forecast model results.  相似文献   

Geographical distribution and accumulation features of organochlorine residues in bivalves from coastal areas of South Korea   总被引：26，自引：0，他引：26  

Kim SK  Oh JR  Shim WJ  Lee DH  Yim UH  Hong SH  Shin YB  Lee DS 《Marine pollution bulletin》2002,45(1-12):268-279

As a part of Mussel Watch Program in Korea, the contamination levels and accumulation features of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were assessed for 82 bivalve samples collected from 66 sites along the entire coast of Korea. The dry weight based ∑PCBs and ∑OCPs ranged from 4.4 ng g⁻¹ to 422.0 ng g⁻¹ (geometric MEAN=36.9 ng g⁻¹) and from 9.95 ng g⁻¹ to 131.37 (34.88) ng g⁻¹, respectively. PCB was predominant in Korean coast, followed by DDTs, HCHs, and Chlordanes. From the observed log normal distribution of PCB and each OCP, low- and high-levels were defined as geometric mean ±1 S.D., respectively. The levels at the sites near urban and/or industrial areas often exceeded the high-levels and the spatial distributions of ∑DDTs and ∑CHLs were correlated with that of ∑PCBs, indicating terrestrial input pathways. Even distribution of ∑HCHs suggested a possibility of atmospheric input pathway of HCHs. The observed isomer ratios of DDTs, HCHs, and CHLs indicated that aging has occurred.  相似文献