Removal of water‐surface reflection effects with a temporal minimum filter for UAV‐based shallow‐water photogrammetry          下载免费PDF全文

I GD Yudha Partama  Ariyo Kanno  Motoyasu Ueda  Yoshihisa Akamatsu  Ryutei Inui  Masahiko Sekine  Koichi Yamamoto  Tsuyoshi Imai  Takaya Higuchi 《地球表面变化过程与地形》2018,43(12):2673-2682

The recent development of structure‐from‐motion (SfM) and multi‐view stereo (MVS) photogrammetry techniques has enabled semi‐automatic high‐resolution bathymetry using aerial images taken by consumer‐grade digital cameras mounted on unmanned aerial vehicles (UAVs). However, the applicability of these techniques is sometimes limited by sun and sky reflections at the water surface, which render the point‐cloud density and accuracy insufficient. In this research, we present a new imaging technique to suppress the effect of these water‐surface reflections. In this technique, we order a drone to take a short video instead of a still picture at each waypoint. We then apply a temporal minimum filter to the video. This filter extracts the smallest RGB values in all the video frames for each pixel, and composes an image with greatly reduced reflection effects. To assess the performance of this technique, we applied it at three small shallow‐water sites. Specifically, we evaluated the effect of the technique on the point cloud density and the accuracy and precision of the photogrammetry. The results showed that the proposed technique achieved a far denser point cloud than the case in which a randomly chosen frame was used for each waypoint, and also showed better overall accuracy and precision in estimating water‐bottom elevation. The effectiveness of this new technique should depend on the surface wave state and sky radiance distribution, and this dependence, as well as the applicability to large areas, should be investigated in future research. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Intrinsic biodegradation of toluene coupled to the microbial reduction of ferric iron: laboratory column experiments     

Zuoping Zheng  Per Aagaard  Gijs D. Breedveld 《Environmental Geology》2002,42(6):649-656

Intrinsic biodegradation of toluene coupled with the microbial reduction of ferric iron (Fe(III)) as the terminal electron acceptor was studied by using laboratory column experiments under continuous flow conditions. Columns were packed with contaminated aquifer sediment and N₂-purged groundwater taken from the western part of the Gardermoen aquifer. The columns were operated anaerobically at 8 °C (in-situ temperature). Chloride was initially used to characterize flow properties of the columns. Intrinsic biodegradation of toluene, including abiotic loss and biological loss, was estimated by comparing breakthrough curves of toluene for live columns and sterilized control columns based on mass balance in steady-state conditions. The column experiments were run at two different flow velocities. The estimated average intrinsic rate was -0.73 and -0.53 mM day^-1 for pore-water velocities of 1.75 and 2.68 cm h^-1, respectively, corresponding to -0.27 and -0.22 mM day^-1 in biological loss rate. The results indicate that intrinsic biodegradation of toluene could be used as an efficient remediation approach for contaminated groundwater at the Gardermoen fire-fighting training site.  相似文献   

Sorption and anaerobic biodegradation of soluble aromatic compounds during groundwater transport. 2. Computer modeling     

Zuoping Zheng  Per Aagaard  Gijs D. Breedveld 《Environmental Geology》2002,41(8):933-941

. The natural attenuation of a binary mixture of toluene and 1,2,4-trimethylbenzene, which was previously experimentally demonstrated in anaerobic column experiments, was simulated with the newly-developed PHREEQC model to reveal the biogeochemical processes involved. The processes considered in this model include advection, diffusion, sorption, redox reactions (e.g., oxidation of toluene and 1,2,4-trimethylbenzene coupled to the reduction of microbial ferric iron), precipitation of secondary minerals such as siderite and magnetite, and dissolution of hydrous ferric oxides, as well as other thermodynamic equilibrium reactions. The functions of advection and diffusion built into the PHREEQC were conventionally simulated. The sorption was kinetically simulated based on a bicontinuum model, whereas biodegradation was described using a multiple-term Monod model. The processes mentioned above were coupled with a geochemical equilibrium model. The consistency between the experimental and modeling results indicates that the processes defined and the controlling parameters chosen could describe the coupled interactions between transport and biogeochemical reactions for the studied system. The discrepancy between modeling and experimental observations, however, also revealed the limitation of the modeling approach. In general, the model approach, which incorporates simplified mathematical representations of the true physico-chemical dynamics of the sorption and biodegradation processes of toluene and 1,2,4-trimethylbenzene under anaerobic conditions is a very efficient and good predictive tool in management and remediation of contaminant groundwater aquifers.  相似文献   

一种基于真实身份的BBS系统实名保障技术   总被引：1，自引：0，他引：1  

张扬  陈萍  吕洁  陈茂科  杨道全 《中国海洋大学学报(自然科学版)》2008,(Z1)

用户身份的真实性一直是BBS系统管理的重要方面之一。采用SAML协议,将跨域单点登录中的认证技术引入到BBS系统中,从而实现了用户采用真实身份登录BBS系统,保证了BBS用户的实名。并以多个高校的BBS系统作为样例,建立起基于真实身份的示范BBS系统。  相似文献   

Sedimentation and chronology of heavy metal pollution in Oslo harbor, Norway   总被引：2，自引：0，他引：2  

Aivo Lepland  Thorbjørn J. Andersen  Hans Peter H. Arp  Gijs D. Breedveld  Anders Rindby 《Marine pollution bulletin》2010,60(9):1512-1522

Stratigraphic profiles of Cu, Cd and Hg in ten sediment cores from the Oslo harbor, Norway, combined with results of radiometric dating demonstrate that pollution by these metals peaked between 1940 and 1970. Dating results indicate that Hg discharges peaked between 1940 and 1950, Cd reached maximum ca. 1955-1960, and Cu has the highest concentration in sediment interval corresponding to ca. 1970. Geochemical profiles and maxima of Cu, Cd and Hg concentrations can be used as chronostratigraphic markers for sediment cores from the Oslo harbor. Acoustic backscatter and sediment core data indicate that propeller wash affects the seabed in the Oslo harbor. The propeller-induced turbulence causes erosion, and in places exposes and remobilizes contaminated sediments that accumulated in the harbor during previous decades. Such re-exposure of contaminated sediments could be detrimental to local ecosystems and offset remediation efforts, warranting further impact studies and potential mitigation strategies to prevent redistribution.  相似文献   

Cause and prevention of well bore clogging by particles     

C. G. E. M. van Beek  R. J. M. Breedveld  M. Juhász-Holterman  A. Oosterhof  P. J. Stuyfzand 《Hydrogeology Journal》2009,17(8):1877-1886

Well bore clogging is caused by accumulation of particles on the well bore. However, all abstracted groundwaters contain particles, but not all wells clog. Apparently, clogging is not caused by the mere presence of particles, but other factors are also involved. Results from on-line well-head readings demonstrate that the clogging rate is not constant: the specific capacity decreases during long abstraction periods and remains constant during intermittent abstraction. Results of particle counts reveal that the particle concentration in the abstracted groundwater shows a peak immediately after switching on the well. This concentration peak is caused by the removal of particles from the well bore that accumulated during the preceding abstraction period. As long as all accumulated particles are removed, no clogging will occur; if not, clogging will occur. Consequently, well bore clogging can be prevented by switching the pump on and off with sufficient frequency to remove the particles accumulated on the well bore during the preceding abstraction period. Moreover, this explanation leads to additional recommendations for well operation, well construction and well design to prevent well bore clogging.  相似文献   

Natural gradient experiment on transport of jet fuel derived hydrocarbons in an unconfined sandy aquifer     

Maciej R. Kłonowski  Gijs D. Breedveld  Per Aagaard 《Environmental Geology》2005,48(8):1040-1057

This paper deals with a field experiment, combining the push–pull and tracer tests, conducted under natural gradient conditions at the international Oslo airport. The studied aquifer, showing very complex hydrogeological settings, has been contaminated by a jet fuel spill. The tracer solutes—bromide, toluene, o-xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene and naphthalene, have been injected into the plume. Their migration and changes in concentration of the electron acceptors and metabolic by-products have been monitored. Fast removal of both the non-reactive tracer as well as the aromatic organics has been observed. The tracer pulse could only be detected 2 m downgradient from the injection points. At this point, toluene and o-xylene have been completely removed, however, trimethylbenzenes and naphthalene have been detected. Their depletion, based on calculations of available electron acceptors, can, to a large extent, be accounted for intrinsic biodegradation, with Fe(III) and sulphate reductions as the major controlling processes.  相似文献   

Release of organic nitrogen compounds from Kerogen via catalytic hydropyrolysis     

B Bennett  GD Love 《Geochemical transactions》2000,1(1):61-7

High hydrogen pressure pyrolysis (hydropyrolysis) was performed on samples of solvent extracted Kimmeridge Clay Formation source rock with a maturity equivalent to ca. 0.35% vitrinite reflectance. We describe the types and distributions of organic nitrogen compounds in the pyrolysis products (hydropyrolysates) using GC-MS. Compounds identified included alkyl-substituted indoles, carbazoles, benzocarbazoles, quinolines and benzoquinolines. The distributions of the isomers of methylcarbazoles, C₂-alkylcarbazoles and benzocarbazoles in the hydropyrolysates were compared to a typical North Sea oil. The hydropyrolysates compared to the North Sea oil, showed increased contributions from alkylcarbazole isomers where the nitrogen group is "exposed" (no alkyl substituents adjacent to the nitrogen functionality) and appreciable levels of benzo[b]carbazole relative to benzo[a]- and benzo[c]carbazoles. Hydropyrolysis is found to be an ideal technique for liberating appreciable quantities of heterocyclic organic nitrogen compounds from geomacromolecules. The products released from the immature Kimmeridge Clay are thought to represent a potential source of nitrogen compounds in the bound phase (kerogen) able to contribute to the free bitumen phase during catagenesis.  相似文献   

The contribution of urban runoff to organic contaminant levels in harbour sediments near two Norwegian cities   总被引：1，自引：0，他引：1  

Cornelissen G  Pettersen A  Nesse E  Eek E  Helland A  Breedveld GD 《Marine pollution bulletin》2008,56(3):565-573

The main aim of the present study was to compare the quality of particle emissions (urban runoff and settling particles in rivers and harbours) to the quality of top-layer bed sediments, for two Norwegian harbours (Oslo and Drammen). A sub-aim was to investigate whether non-industrial urban runoff contributed to the organotin load of sediments, apart from leaching from ship hulls. Time-integrated samples of stormwater runoff were obtained in an innovative manner, by sampling man-holes in the stormwater system. Settling particles were sampled with sediment traps. The study focused on PAHs, PCBs and organotin compounds. Contaminant levels were generally a factor of 2-10 (PAHs) and 3-30 (TBT) lower in emitted riverine and runoff particles than in top-layer bed sediments, except for PCBs in Oslo harbour (only 20-30% lower). Significant levels of tributyltin (TBT; median 140mug/kg) were shown in runoff particles, showing that TBT can also be emitted via urban sources, since the sampled man-holes were not in areas where dry-docking activities take place. Possible land-based TBT sources include long-lasting house paint and use of TBT as PVC stabilizer and timber preservative. Since there are ongoing emissions into the two studied harbour areas, it is concluded that the addition of an actively sorbing capping material such as activated carbon might be the best remediation alternative.  相似文献   

Sorption and anaerobic biodegradation of soluble aromatic compounds during groundwater transport. 1. Laboratory column experiments     

Zuoping Zheng  Per Aagaard  Gijs D. Breedveld 《Environmental Geology》2002,41(8):922-932

. This paper deals with sorption and anaerobic biodegradation of the soluble aromatic fraction of jet fuel and how it is influenced by pore-water velocity during transport in a groundwater aquifer. The study was carried out as controlled laboratory column experiments. A binary mixture of toluene and 1,2,4-trimethylbenzene with a concentration ratio of 2:1 was used through the entire investigations. The column experiments were conducted with contaminated sediments and groundwater, taken from wells at a field research site. The columns were operated anaerobically under continuous-flow conditions at 10 °C in a temperature-controlled refrigerator. Two percent sodium azide was added to the injection solution of two of the columns to prevent biodegradation of the studied organic mixture. Chloride was used as a conservative tracer to characterize the hydrodynamic parameters such as dispersivity and porosity of the columns. The results showed that both compounds in the mixture were attenuated because of sorption and biodegradation processes in the columns. 1,2,4-trimethylbenzene was attenuated more significantly than toluene. Biodegradation of toluene was coupled mainly with the microbial reduction of ferric iron, whereas 1,2,4-trimethylbenzene, in contrast, was mostly sorbed. Their sorption and biodegradation were studied with different pore-water velocities, and a mass balance approach was applied to calculate biodegradation rates. The biodegradation rates of toluene were –0.16, –0.21, and –0.26 (unit: mM day^–1) for pore-water velocities of 96, 82.4, and 54.9 (unit: cm day^–1), respectively. This indicates that a decrease in the pore-water velocity significantly enhanced the biodegradation of toluene, consistent with other reports in the literature. For 1,2,4-trimethylbenzene the biodegradation rates were –0.05, –0.13 (unit: mM day^–1) for pore-water velocities of 96 and 82.4 (unit: cm day^–1), respectively. The biodegradation rate of 1,2,4-trimethylbenzene did not increase at the lowest pore water velocity as expected. This might be a result of substrate competition.  相似文献