Removal of tributyltin (TBT) by live and dead microalgal cells   总被引：3，自引：0，他引：3  

Tam NF  Chong AM  Wong YS 《Marine pollution bulletin》2002,45(1-12):362-371

The removal of tributyltin (TBT) from artificial wastewater by dead and live cells of four microalgal species, Chlorella miniata, C. sorokiniana, Scenedesmus dimorphus and S. platydiscus was investigated. Dead cells were generally more efficient in removing TBT during three days exposure. More than 90% and 85% TBT were removed by dead cells of Scenedesmus and Chlorella, respectively. Although the removal percentages of live microalgae were smaller, TBT was continuously absorbed and degraded, and TBT removal percentages similar to respective dead cells were achieved at the end of 14 days treatment. Degradation products, DBT and MBT, were recorded mainly inside the cells, and intracellular MBT concentrations were significantly higher than DBT. In terms of TBT removal, Scenedesmus cells were more effective than Chlorella, probably due to larger cell sizes and biomass. However, TBT specific uptake and degradation by Chlorella was higher than in Scenedesmus. The highest specific TBT uptake values, as well as the highest degradation, were recorded in C. miniata, a Hong Kong isolate.  相似文献   

HEAVY PRECIPITATION IN HONG KONG, 1951-2000^*          下载免费PDF全文

YAN Yuk Yee 《Acta Meteorologica Sinica》2003,17(1):93-104

Daily precipitation amounts greater than 50 mm from 1951 to 2000 in Hong Kong were analyzed to determine their seasonal and annual frequencies.A total of 627 extreme rainfall days happened and 334 (53.27%) days occurred in summer.Non significant increasing trends for annual precipitation and number of heavy rain days were detected.Daily surface weather maps were used to identify the synoptic weather types producing the heavy rainfall.It was discovered that tropical cyclone and low pressure induced most of the heavy precipitation.Seven out of twelve years with counts of heavy rain days over fifteen coincided with E1 Nino events.  相似文献   

Rare Earth Element Geochemistry of the Zigzag - Klondyke Sedimentary Rock Formations: Clues to the Evolution of the Baguio Mineral District (Luzon), Philippines     

Tomas A. Tam  III    Graciano P. Yumul  Jr    Estephanie Gera L. Ramos  Carla B. Dimalanta  Mei-Fu Zhou  Shigeyuki Suzuki 《Resource Geology》2005,55(3):217-224

Abstract. Petrographic analysis of the Oligocene-Miocene Zigzag Formation and Miocene Klondyke Formation of the Baguio Mineral District reveals a transitional arc source for the former and an undissected arc source for the latter. Whole rock geochemistry of these sedimentary rock formations show affiliation of the Zigzag Formation to active continental margin whereas the Klondyke Formation appears to have been derived from an oceanic island arc source. A different aspect of the geology of the district is further gleaned from the whole rock rare earth element geochemistry of these rocks. Samples from the Zigzag Formation are characterized by higher REE concentrations compared to the Klondyke Formation samples. The REE data indicate that the sedimentary rocks of the Klondyke Formation had geochemically-less fractionated igneous lithologies as their progenitor whereas the older Zigzag Formation was derived from a more differentiated source. This new set of information contributes to the understanding of the evolution of this district from a marginal basin to an island arc setting.  相似文献   

An Analysis of Thermal Stress of Climate in Hong Kong     

Yuk Yee Yan 《Singapore journal of tropical geography》1997,18(2):210-217

The universal scale of apparent temperature (AT) and clo, a unit measuring the amount of clothing insulation required to maintain comfort, were used to examine the weather stress in Hong Kong. Hourly AT and clo values were computed using hourly air temperature, wind speed, vapour pressure and cloud cover data from 1980 to 1994. Results of both AT and clo reflected highly corresponding changes of thermal stress. It is found that the most stressful time in winter and summer occurred in the early morning and afternoon, and cool weather and tropical ensembles were required to surmount the extreme weather stress respectively. A greater percent of time with severe heat stress than those with extreme cold stress was discovered. These results also indicated that clo is a more informative weather stress index than AT since it provides both the thermal stress and clothing requirements to sustain comfort.  相似文献   

IMPACT OF CLIMATE ON SUMMER RESIDENTIAL ELECTRICITY CONSUMPTION IN HONG KONG     

Yuk Yee Yan Department of Geography Hong Kong Baptist University Kowloon Tong  Hong Kong 《地理学报(英文版)》1997,(4)

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Spatial and temporal variations of heavy metal contamination in sediments of a mangrove swamp in Hong Kong   总被引：1，自引：0，他引：1  

N. F. Y. Tam  Y. S. Wong 《Marine pollution bulletin》1995,31(4-12)

Spatial and temporal variations of heavy metal contamination in sediments of a small mangrove stand in Hong Kong were examined by laying two transects perpendicular across the shore. Surface sediment samples were taken along the two transects running landward to seaward at intervals of 5 or 10 m during December 1989, and March, July and September 1990. Total concentrations of Cu, Zn, Mn and Pb did not show any specific trend along each transect, although the maximum concentration of heavy metals tended to occur at the landward edge. There was a high level of variability among locations within each transect; for instance, the Cu concentrations fluctuated from 1 to 42 μg g⁻¹. Certain sites contained exceptionally high levels of total metals. Total concentrations of Cu, Zn, Mn and Pb as high as 42, 150, 640 and 650 μg g⁻¹, respectively, were recorded, implying contaminated sediment. A comparison of the two transects indicated that the sediments of Transect B seemed to contain higher total Zn but lower Cu and Mn concentrations than those of Transect A. Most of the heavy metals accumulated in the sediments were not extractable with ammonium acetate and no Cu or Pb was detected in these extracts. The concentrations of extractable Zn and Mn were low, less than 10% of the total metal concentration in the sediment, and appeared to decrease from the landward to seaward samples. For both total and extractable metals, there were significant seasonal fluctuations for both transects, but no specific trends could be identified. These spatial and temporal variations suggest that the scale and representativeness of sampling require careful planning, and a single sample might not give a satisfactory evaluation of the levels of heavy metal contamination in mangrove ecosystems.  相似文献   

DEM-based morphometry of large-scale sand dune patterns in the Grand Erg Oriental (Northern Sahara Desert,Africa)     

Tamás Telbisz  Orsolya Keszler 《Arabian Journal of Geosciences》2018,11(14):382

Formerly, sand dune patterns were investigated mostly by aerial and satellite images, but more recently, geomorphometric analysis based on digital elevation models (DEMs) has become an important approach. In this paper, sand dune patterns of the Grand Erg Oriental (Sahara) are studied using the De Ferranti (2014) DEM, which is a blending of SRTM (Shuttle Radar Topography Mission), ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) and other elevation datasets. In the Grand Erg Oriental, there are four large-scale dune pattern types with gradual transitions between them and with several subtypes, namely P1, consisting of large, branching linear dunes; P2, a complex pattern including small-size and widely spaced star and dome dunes; P3, a network type created mostly from crescentic dunes; and finally, P4, consisting of large and closely spaced star dunes. The largest dunes with 90–100-m mean height can be found in the southern parts of the Grand Erg Oriental, where P1 and P4 patterns dominate, and these areas are also characterised by the most intensive sand accumulation with 25–30-m equivalent sand thickness. In the present study, we use regression analysis to investigate the functional relationships between sand dune characteristics. Further on, we have elaborated a DEM-based method to delineate dunes and calculate sand volumes and dune orientations. Comparing wind rose data and sand dune axis rose diagrams, it is concluded that in some parts of the Grand Erg Oriental, the present dune types and patterns are in agreement with the actual wind regime, but in other cases, the present dune patterns are at least partially the results of former wind regimes.  相似文献   

Canopy Structure Attributes Extraction from LiDAR Data Based on Tree Morphology and Crown Height Proportion     

Qingyan Meng  Xu Chen  Jiahui Zhang  Yunxiao Sun  Jiaguo Li  Tamás Jancsó  Zhenhui Sun 《Journal of the Indian Society of Remote Sensing》2018,46(9):1433-1444

Urban green space is important for the well-being of urban residents. Seeking for three spatial dimension stereopsis is a very important issue in investigating urban green space. A potential applicability in the domain of urban tree space measurement and modelling has been explored based on LiDAR data in our study. This paper aims to present a framework—through a more automatic way—to extract canopy structure attributes. In this study, treetops were filtered by local maxima filtering algorithm from canopy height model. An improved spoke wheel algorithm was used to delineate the crown boundaries. And, an estimation issue of crown volume was simplified into three measurable parameters by estimating the crown structures. For accuracy assessment, data of 363 sampled trees located in the subset of Székesfehérvár city were selected randomly. The overall detection rate of treetop had proven to be 95.87% and crown boundaries were recognized effectively with a delineation quality of 88.59%, which were acceptable. About 80.26% of investigated crown volume estimates were obtained with shape distortion ranging from 3.1 to 7.8% according to the error analysis. The results indicated that the method can be used to extract canopy structure in urban areas.  相似文献   

The simulation of a storm surge and wave due to Typhoon Sarah using an integrally coupled tide-surge-wave model of the Yellow and East China Seas     

Jin-Hee Yuk  Kyeong Ok Kim  Byung Ho Choi 《Ocean Science Journal》2015,50(4):683-699

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The Footprint Database and Web Services of the Herschel Space Observatory     

László Dobos  Erika Varga-Verebélyi  Eva Verdugo  David Teyssier  Katrina Exter  Ivan Valtchanov  Tamás Budavári  Csaba Kiss 《Experimental Astronomy》2016,42(2):139-164

Data from the Herschel Space Observatory is freely available to the public but no uniformly processed catalogue of the observations has been published so far. To date, the Herschel Science Archive does not contain the exact sky coverage (footprint) of individual observations and supports search for measurements based on bounding circles only. Drawing on previous experience in implementing footprint databases, we built the Herschel Footprint Database and Web Services for the Herschel Space Observatory to provide efficient search capabilities for typical astronomical queries. The database was designed with the following main goals in mind: (a) provide a unified data model for meta-data of all instruments and observational modes, (b) quickly find observations covering a selected object and its neighbourhood, (c) quickly find every observation in a larger area of the sky, (d) allow for finding solar system objects crossing observation fields. As a first step, we developed a unified data model of observations of all three Herschel instruments for all pointing and instrument modes. Then, using telescope pointing information and observational meta-data, we compiled a database of footprints. As opposed to methods using pixellation of the sphere, we represent sky coverage in an exact geometric form allowing for precise area calculations. For easier handling of Herschel observation footprints with rather complex shapes, two algorithms were implemented to reduce the outline. Furthermore, a new visualisation tool to plot footprints with various spherical projections was developed. Indexing of the footprints using Hierarchical Triangular Mesh makes it possible to quickly find observations based on sky coverage, time and meta-data. The database is accessible via a web site http://herschel.vo.elte.hu and also as a set of REST web service functions, which makes it readily usable from programming environments such as Python or IDL. The web service allows downloading footprint data in various formats including Virtual Observatory standards.  相似文献