Frontiers of Earth Science

ISSN 2095-0195

ISSN 2095-0209(Online)

CN 11-5982/P

2018 Impact Factor: 1.205

Cover Story   2013, Volume 7 Issue 1
   Online First

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, Volume 7 Issue 1

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RESEARCH ARTICLE
Short-term emergency response planning and risk assessment via an integrated modeling system for nuclear power plants in complex terrain
Ni-Bin CHANG, Yu-Chi WENG
Front Earth Sci. 2013, 7 (1): 1-27.  
https://doi.org/10.1007/s11707-012-0342-y

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Short-term predictions of potential impacts from accidental release of various radionuclides at nuclear power plants are acutely needed, especially after the Fukushima accident in Japan. An integrated modeling system that provides expert services to assess the consequences of accidental or intentional releases of radioactive materials to the atmosphere has received wide attention. These scenarios can be initiated either by accident due to human, software, or mechanical failures, or from intentional acts such as sabotage and radiological dispersal devices. Stringent action might be required just minutes after the occurrence of accidental or intentional release. To fulfill the basic functions of emergency preparedness and response systems, previous studies seldom consider the suitability of air pollutant dispersion models or the connectivity between source term, dispersion, and exposure assessment models in a holistic context for decision support. Therefore, the Gaussian plume and puff models, which are only suitable for illustrating neutral air pollutants in flat terrain conditional to limited meteorological situations, are frequently used to predict the impact from accidental release of industrial sources. In situations with complex terrain or special meteorological conditions, the proposing emergency response actions might be questionable and even intractable to decision-makers responsible for maintaining public health and environmental quality. This study is a preliminary effort to integrate the source term, dispersion, and exposure assessment models into a Spatial Decision Support System (SDSS) to tackle the complex issues for short-term emergency response planning and risk assessment at nuclear power plants. Through a series model screening procedures, we found that the diagnostic (objective) wind field model with the aid of sufficient on-site meteorological monitoring data was the most applicable model to promptly address the trend of local wind field patterns. However, most of the hazardous materials being released into the environment from nuclear power plants are not neutral pollutants, so the particle and multi-segment puff models can be regarded as the most suitable models to incorporate into the output of the diagnostic wind field model in a modern emergency preparedness and response system. The proposed SDSS illustrates the state-of-the-art system design based on the situation of complex terrain in South Taiwan. This system design of SDSS with 3-dimensional animation capability using a tailored source term model in connection with ArcView? Geographical Information System map layers and remote sensing images is useful for meeting the design goal of nuclear power plants located in complex terrain.

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Deriving average delay of traffic flow around intersections from vehicle trajectory data
Minyue ZHAO, Xiang LI
Front Earth Sci. 2013, 7 (1): 28-33.  
https://doi.org/10.1007/s11707-012-0341-z

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Advances of positioning and wireless communication technologies make it possible to collect a large number of trajectory data of moving vehicles in a fast and convenient fashion. The data can be applied to various fields such as traffic study. In this paper, we attempt to derive average delay of traffic flow around intersections and verify the results with changes of time. The intersection zone is delineated first. Positioning points geographically located within this zone are selected, and then outliers are removed. Turn trips are extracted from selected trajectory data. Each trip, physically consisting of time-series positioning points, is identified with entry road segment and turning direction, i.e. target road segment. Turn trips are grouped into different categories according to their time attributes. Then, delay of each trip during a turn is calculated with its recorded speed. Delays of all trips in the same period of time are plotted to observe the change pattern of traffic conditions. Compared to conventional approaches, the proposed method can be applied to those intersections without fixed data collection devices such as loop detectors since a large number of trajectory data can always provide a more complete spatio-temporal picture of a road network. With respect to data availability, taxi trajectory data and an intersection in Shanghai are employed to test the proposed methodology. Results demonstrate its applicability.

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How many probe vehicles are enough for identifying traffic congestion?—a study from a streaming data perspective
Handong WANG, Yang YUE, Qingquan LI
Front Earth Sci. 2013, 7 (1): 34-42.  
https://doi.org/10.1007/s11707-012-0343-x

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Many studies have been carried out using vehicle trajectory to analyze traffic conditions, for instance, identifying traffic congestion. However, there is a lack of a systematic study on the appropriate number of probe vehicles and their sampling interval in order to identify traffic congestion accurately. Moreover, most of related studies ignore the streaming feature of trajectory data. This paper first represents a novel method of identifying traffic congestion considering the stream feature of vehicle trajectories. Instead of processing the whole data stream, a series of snapshots are extracted. Congested road segments can be identified by analyzing the clusters’ evolution among a series of adjacent snapshots. We then calculated a series of parameters and their corresponding congestion identification accuracy. The results have implications for related probe vehicle deployment and traffic analysis; for example, when 5% of probe vehicles are available, 85% identification accuracy can be reached if the sampling time interval is 10 s.

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Toward automatic estimation of urban green volume using airborne LiDAR data and high resolution Remote Sensing images
Yan HUANG, Bailang YU, Jianhua ZHOU, Chunlin HU, Wenqi TAN, Zhiming HU, Jianping WU
Front Earth Sci. 2013, 7 (1): 43-54.  
https://doi.org/10.1007/s11707-012-0339-6

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Urban green volume is an important indicator for analyzing urban vegetation structure, ecological evaluation, and green-economic estimation. This paper proposes an object-based method for automated estimation of urban green volume combining three-dimensional (3D) information from airborne Light Detection and Ranging (LiDAR) data and vegetation information from high resolution remotely sensed images through a case study of the Lujiazui region, Shanghai, China. High resolution airborne near-infrared photographs are used for identifying the urban vegetation distribution. Airborne LiDAR data offer the possibility to extract individual trees and to measure the attributes of trees, such as tree height and crown diameter. In this study, individual trees and grassland are identified as the independent objects of urban vegetation, and the urban green volume is computed as the sum of two broad portions: individual trees volume and grassland volume. The method consists of following steps: generating and filtering the normalized digital surface model (nDSM), extracting the nDSM of urban vegetation based on the Normalized Difference Vegetation Index (NDVI), locating the local maxima points, segmenting the vegetation objects of individual tree crowns and grassland, and calculating the urban green volume of each vegetation object. The results show the quantity and distribution characteristics of urban green volume in the Lujiazui region, and provide valuable parameters for urban green planning and management. It is also concluded from this paper that the integrated application of LiDAR data and image data presents an effective way to estimate urban green volume.

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Unconformity structures controlling stratigraphic reservoirs in the north-west margin of Junggar basin, North-west China
Kongyou WU, Douglas PATON, Ming ZHA
Front Earth Sci. 2013, 7 (1): 55-64.  
https://doi.org/10.1007/s11707-012-0344-9

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Tectonic movements formed several unconformities in the north-west margin of the Junggar basin. Based on data of outcrop, core, and samples, the unconformity is a structural body whose formation associates with weathering, leaching, and onlap. At the same time, the structural body may be divided into three layers, including upper layer, mid layer, and lower layer. The upper layer with good primary porosity serves as the hydrocarbon migration system, and also accumulates the hydrocarbon. The mid layer with compactness and ductility can play a role as cap rock, the strength of which increases with depth. The lower layer with good secondary porosity due to weathering and leaching can form the stratigraphic truncation traps. A typical stratigraphic reservoir lying in the unconformity between the Jurassic and Triassic in the north-west margin of the Junggar basin was meticulously analyzed in order to reveal the key controlling factors. The results showed that the hydrocarbon distribution in the stratigraphic onlap reservoirs was controlled by the onlap line, the hydrocarbon distribution in the stratigraphic truncation reservoirs was confined by the truncation line, and the mid layer acted as the key sealing rock. So a conclusion was drawn that “two lines (onlap line and truncation line) and a body(unconformity structural body)” control the formation and distribution of stratigraphic reservoirs.

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Application of remote sensing and GIS analysis for identifying groundwater potential zone in parts of Kodaikanal Taluk, South India
Murugesan BAGYARAJ, Thirunavukkarasu RAMKUMAR, Senapathi VENKATRAMANAN, Balasubramanian GURUGNANAM
Front Earth Sci. 2013, 7 (1): 65-75.  
https://doi.org/10.1007/s11707-012-0347-6

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Groundwater potential zones were demarcated with the help of remote sensing and Geographic Information System (GIS) techniques. The study area is composed rocks of Archaean age and charnockite dominated over others. The parameters considered for identifying the groundwater potential zone of geology slope, drainage density, geomorphic units and lineament density were generated using the resource sat (IRS P6 LISS IV MX) data and survey of India (SOI) toposheets of scale 1:50000 and integrated them with an inverse distance weighted (IDW) model based on GIS data to identify the groundwater potential of the study area. Suitable weightage factors were assigned for each category of these parameters. For the various geomorphic units, weightage factors were assigned based on their capability to store ground-water. This procedure was repeated for all the other layers and resultant layers were reclassified. The reclassified layers were then combined to demarcate zones as very good, good, moderate, low, and poor. This groundwater potentiality information could be used for effective identification of suitable locations for extraction of potable water for rural populations.

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The diversity of soil culturable fungi in the three alpine shrub grasslands of Eastern Qilian Mountains
Junzhong ZHANG, Baiying MAN, Benzhong FU, Li LIU, Changzhi HAN
Front Earth Sci. 2013, 7 (1): 76-84.  
https://doi.org/10.1007/s11707-012-0345-8

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To understand the diversity of culturable fungi in soil at alpine sites, Rhododendron fruticosa shrubland, Salix cupularis fruticosa shrubland, and Dasiphoru fruticosa shrubland of the Eastern Qilian Mountains were selected to investigate. Three methods, including traditional culturing, rDNA internal transcribed spacer (ITS) sequence analysis, and economical efficiency analysis, were carried out to estimate the diversity of soil culturable fungi of these three alpine shrublands. A total of 35 strains of culturable fungi were cultured by dilution plate technique and were analyzed by rDNA ITS sequence. The diversity indices such as species abundance (S), Shannon–Wiener index (H), Simpson dominance index (D), and Pielou evenness index (J) of Rhododendron fruticosa shrubland, Salix cupularis fruticosa shrubland, and Dasiphoru fruticosa shrubland were ranged between 16 and 17, 2.66–2.71, 0.92, 0.95–0.97 respectively. The results showed that the diversity of soil fungi were abundant in these three types of alpine shrub grasslands, while further study should be done to explore their potential value.

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Mechanism of the effect caused by highway construction on plant biomass in Longitudinal Range-Gorge Region
Jie LIU, Honglei XU, Chunping CHANG
Front Earth Sci. 2013, 7 (1): 85-91.  
https://doi.org/10.1007/s11707-012-0298-y

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Taking Dabao (from Dali City to Baoshan City, Yunnan Province, China) and Sixiao (from Simao City to Xiaomengyang Town, Yunnan Province, China) highways in Longitudinal Range-Gorge Region as examples. Biomass, coverage and photosynthesis rate of different plant types on sampling points (at the distances from road of 5, 20, 40, 80, 120 and 200 m) and their control points were estimated on ground. The relations among biomass, coverage, photosynthesis rate were analyzed with an aim to explore the mechanism of the effect caused by highway construction on plant biomass. The results show, i) the impacts of highway construction on plant biomass are both positive and negative. Arbor is mainly negatively impacted, while shrub and herbage are mainly positively impacted. The effect of highway construction decrease with the increase of distance from the road; ii) highway construction exert obvious influence on plant biomass through altering the physiologic processes (reflected by the plant number) and photosynthesis, iii) highway construction will result in the decrease of arbor number, photosynthesis rate and biomass, and increase of plant number, photosynthesis rate and biomass of shrub and herbage.

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The spatio-temporal responses of the carbon cycle to climate and land use/land cover changes between 1981–2000 in China
Zhiqiang GAO, Xiaoming CAO, Wei GAO
Front Earth Sci. 2013, 7 (1): 92-102.  
https://doi.org/10.1007/s11707-012-0335-x

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This paper represents the first national effort of its kind to systematically investigate the impact of changes in climate and land use and land cover (LULC) on the carbon cycle with high-resolution dynamic LULC data at the decadal scale (1990s and 2000s). Based on simulations using well calibrated and validated Carbon Exchanges in the Vegetation-Soil-Atmosphere (CEVSA) model, temporal and spatial variations in carbon storage and fluxes in China may be generated empower us to relate these variations to climate variability and LULC with respect to net primary productivity (NPP), heterotrophic respiration (HR), net ecosystem productivity (NEP), storage and soil carbon (SOC), and vegetation carbon (VEGC) individually or collectively. Overall, the increases in NPP were greater than HR in most cases due to the effect of global warming with more precipitation in China from 1981 to 2000. With this trend, the NEP remained positive during that period, resulting in a net increase of total amount of carbon being stored by about 0.296 PgC within a 20-year time frame. Because the climate effect was much greater than that of changes of LULC, the total carbon storage in China actually increased by about 0.17 PgC within the 20-year time period. Such findings will contribute to the generation of carbon emissions control policies under global climate change impacts.

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An artificial neural network approach to estimate evapotranspiration from remote sensing and AmeriFlux data
Zhuoqi CHEN, Runhe SHI, Shupeng Zhang
Front Earth Sci. 2013, 7 (1): 103-111.  
https://doi.org/10.1007/s11707-012-0346-7

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A simple and accurate method to estimate evapotranspiration (ET) is essential for dynamic monitoring of the Earth system at a large scale. In this paper, we developed an artificial neural network (ANN) model forced by remote sensing and AmeriFlux data to estimate ET. First, the ANN was trained with ET measurements made at 13 AmeriFlux sites and land surface products derived from satellite remotely sensed data (normalized difference vegetation index, land surface temperature and surface net radiation) for the period 2002–2006. ET estimated with the ANN was then validated by ET observed at five AmeriFlux sites during the same period. The validation sites covered five different vegetation types and were not involved in the ANN training. The coefficient of determination (R2) value for comparison between estimated and measured ET was 0.77, the root-mean-square error was 0.62 mm/d, and the mean residual was -0.28. The simple model developed in this paper captured the seasonal and interannual variation features of ET on the whole. However, the accuracy of estimated ET depended on the vegetation types, among which estimated ET showed the best result for deciduous broadleaf forest compared to the other four vegetation types.

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Changes of net primary productivity in China during recent 11 years detected using an ecological model driven by MODIS data
Yibo LIU, Weimin JU, Honglin HE, Shaoqiang WANG, Rui SUN, Yuandong ZHANG
Front Earth Sci. 2013, 7 (1): 112-127.  
https://doi.org/10.1007/s11707-012-0348-5

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Net primary productivity (NPP) is an important component of the terrestrial carbon cycle. Accurately mapping the spatial-temporal variations of NPP in China is crucial for global carbon cycling study. In this study the process-based Boreal Ecosystem Productivity Simulator (BEPS) was employed to study the changes of NPP in China’s ecosystems for the period from 2000 to 2010. The BEPS model was first validated using gross primary productivity (GPP) measured at typical flux sites and forest NPP measured at different regions. Then it was driven with leaf area index (LAI) inversed from the Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance and land cover products and meteorological data interpolated from observations at 753 national basic meteorological stations to simulate NPP at daily time steps and a spatial resolution of 500 m from January 1, 2000 to December 31, 2010. Validations show that BEPS is able to capture the seasonal variations of tower-based GPP and the spatial variability of forest NPP in different regions of China. Estimated national total of annual NPP varied from 2.63 to 2.84 Pg C·yr-1, averaging 2.74 Pg C·yr-1 during the study period. Simulated terrestrial NPP shows spatial patterns decreasing from the east to the west and from the south to the north, in association with land cover types and climate. South-west China makes the largest contribution to the national total of NPP while NPP in the North-west account for only 3.97% of the national total. During the recent 11 years, the temporal changes of NPP were heterogamous. NPP increased in 63.8% of China’s landmass, mainly in areas north of the Yangtze River and decreased in most areas of southern China, owing to the low temperature freezing in early 2008 and the severe drought in late 2009.

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11 articles