Shen D.,Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology |
Shen D.,Nanjing University |
Shen D.,Changjiang River Scientific Research Institute |
Rui Y.,Jiangsu Provincial Key Laboratory of Geographic Information Science and Technology |
And 7 more authors.
Computers and Geosciences | Year: 2015
Flood inundation extent, depth, and duration are important factors affecting flood hazard evaluation. At present, flood inundation analysis is based mainly on a seeded region-growing algorithm, which is an inefficient process because it requires excessive recursive computations and it is incapable of processing massive datasets. To address this problem, we propose a block compressed tracing algorithm for mapping the flood inundation extent, which reads the DEM data in blocks before transferring them to raster compression storage. This allows a smaller computer memory to process a larger amount of data, which solves the problem of the regular seeded region-growing algorithm. In addition, the use of a raster boundary tracing technique allows the algorithm to avoid the time-consuming computations required by the seeded region-growing. Finally, we conduct a comparative evaluation in the Chin-sha River basin, results show that the proposed method solves the problem of flood inundation extent mapping based on massive DEM datasets with higher computational efficiency than the original method, which makes it suitable for practical applications. © 2015 Elsevier Ltd.
Zhang X.,Nanjing University of Information Science and Technology |
Chen D.,Queen's University |
Zhong T.,Nanjing University |
Cheng M.,Nanjing University of Information Science and Technology |
And 2 more authors.
Clean - Soil, Air, Water | Year: 2015
Lead (Pb) contamination in arable soils is one of the most serious ecological problems due to its high toxicity on human health. Thus, we need to understand the concentration level, contaminated area, and spatial distribution of Pb in arable soils on regional or national scale. This paper reviewed the studies on Pb concentrations throughout Chinese arable soils, based on relevant 537 studies from 2002 to 2014. The results showed that the average Pb concentration was 34.41mg/kg, higher than its background of 23.50mg/kg, indicating that Pb has been introduced into soil from exterior sources. Mining and smelting activities, irrigation by wastewater, and urban development greatly contributed to Pb accumulation in arable soils. North China had lower Pb concentrations than the south, and many hotspots existed on the Pb concentration map due to mining and smelting activities. On the provincial scale, arable soils in Yunnan, Guangxi, and Shaanxi Provinces were moderately polluted by Pb, Gansu and Shaanxi Provinces were slightly affected by Pb, while the other provinces showed relative safe levels. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Wang J.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research |
Wang J.,Jiangsu Center For Collaborative Innovation In Geographical Information Resource Dev And Applied |
Zhou Y.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research |
Zhou Y.,Sichuan Province in second Geographic Information Engineering Institute of Surveying and Mapping |
And 4 more authors.
Remote Sensing | Year: 2014
Cultivated land resources are an important basis of regional sustainability; thus, it is important to determine the distribution of the cultivated land in the Northeast Asia trans-boundary area of China, Russia and Mongolia, which has a continuous geographic and ecological environment and an uneven population distribution. Extracting information about the cultivated land and determining the spatial and temporal distribution of its features in this large trans-boundary area is a challenge. In this study, we derived information about the cultivated land of the North-South Transect in Northeast Asia by Linear Spectral Mixing Model, using time series data with MODerate resolution Imaging Spectroradiometer (MODIS) in 2000 and 2010. The validation showed more than 98% pixels with a root mean square error less than 0.05. The overall accuracy and spatial consistency coefficients were 81.63% and 0.78 in 2000 and 72.81% and 0.75 in 2010, respectively. The transect analyses indicate the presence of a greater amount of cultivated land in the south and less in the north. China owns most of the cultivated land in the transect area, followed by Mongolia and then Russia. A gradient analysis revealed a decrease of 34.16% of the cultivated land between 2000 and 2010. The amount of cultivated land decreased 22.37%, 58.93%, and 64.73% in China, Russia, and Mongolia, respectively. An analysis shows that the amount of cultivated land is primarily influenced by the various land development and protection policies in the different counties in this trans-boundary area. © 2014 by the authors.
Huang Y.,Hohai University |
Xu L.,Hohai University |
Han R.,Nanjing Normal University |
Han R.,Jiangsu Center For Collaborative Innovation In Geographical Information Resource Dev And Applied |
And 8 more authors.
Harmful Algae | Year: 2015
A cyanobacteria-induced black bloom in Taihu Lake, 2007, subjected nearly one million Wuxi City residents to a drinking water crisis. This black bloom attracted wide attention in China and the rest of the world. However, black bloom is a highly weather-dependent event, and its rapid movement in lakes makes it difficult to predict where it will occur. Therefore, jar-tests and simulated flow experiments were performed to investigate the flocculation, deposition, and resuspension of black-bloom-induced black matter. At a dosage of 0.2gL-1 chitosan+1gL-1 diatomite, 90% of the turbidity was removed within 1h in jar-tests and in low flow speed simulated experiments. However, the black matter/clay flocs did not fully sink, and stratification of turbidity apparently occurred in the lower part of the tank during the simulated flow experiments. The resuspension experiments under simulated flow speeds showed that at a wind speed of 1-6ms-1 in Taihu Lake produced currents that did not greatly affect floc resuspension, but a wind speed of 3-4ms-1 produced waves that could induce floc resuspension. Quartz sand was sprayed over the flocs to verify its effect on inhibiting resuspension. A shear stress of 0.37Nm-2 did not induce floc resuspension, which indicated that a wind speed of 6ms-1 would not induce floc resuspension in Taihu Lake. © 2015 Elsevier B.V..
Wang Y.,Nanjing Normal University |
Wang Y.,Jiangsu Center For Collaborative Innovation In Geographical Information Resource Dev And Applied |
Yang H.,Nanjing Normal University |
Yang H.,Jiangsu Center For Collaborative Innovation In Geographical Information Resource Dev And Applied |
And 4 more authors.
Science of the Total Environment | Year: 2015
Natural inputs and anthropogenic influences on lakes and their catchments are reflected in the sediment record. In the present study, the extractable organic compounds from sediments in the Chaihe catchment of the Dianchi watershed were analyzed to characterize source inputs. Results show that the sediments are dominated by odd numbered n-alkanes (n-C16-n-C33), maximizing at n-C17, n-C29 and n-C31. Aliphatic hydrocarbon may be composed of terrestrial plants and bacteria. The values of δ13C27, δ13C29 and δ13C31 of n-alkanes exhibit a range from -33.27‰ to -25.46‰, from -35.76‰ to -28.47‰ and from -33.67‰ to -27.42‰, respectively and three records strongly covary with depth, falling within the range of C3 plants in the study area. An isotopic model revealed C3 plant contribution to sedimentary organic matter (OM) ranging from 40.75% to 97.22%. The values of ACL27-33, CPI27-33, OEP, Paq, Pr/Ph, (C27+C29)/2C31, (C21+C23+C25)/3C17 and nC26 -/nC27 + are consistent with the C3 plant predominance. A constant CRS model gave the accumulation rates ranging from 2.69 to 8.46mma-1 spanning 1885-2010. It was concluded that OM transport in the Chaihe catchment was influenced strongly by human activities resulting in enhanced eutrophication. © 2014 Elsevier B.V.
Zhang C.,China University of Geosciences |
Zhang C.,Chinese University of Hong Kong |
Chen M.,Jiangsu Center For Collaborative Innovation In Geographical Information Resource Dev And Applied |
Chen M.,Nanjing Normal University |
And 4 more authors.
Applied Geography | Year: 2015
The spatial decision support system (SDSS) is widely used in environmental problem management. In this paper, focusing on the air quality problem in the Pearl River Delta, China, we present a virtual geographic environment (VGE) system to integrate multiscale meteorological and air quality models for policy making. It is a comprehensive modeling tool to aid decision makers and various stakeholders to participate in air quality management by providing geographic visualizations and friendly interfaces. With nested multiscale models, a synthetic understanding of cross-boundary air quality processes can be captured to understand both regional and local effects. With the help of Linux-Apache-MySQL-Perl (LAMP) architecture, users can manage and retrieve modeling data and model parameterizations to reach a consensus on the simulation results and share modeling knowledge. Aided by a high-resolved emission inventory, such a multiscale system enables practical applications for various scenarios. As a case study, the system was applied to simulate and analyze the SO2 concentration process and local contribution in the Hong Kong Special Administrative Region (HKSAR) based on hourly simulation results with spatial resolutions of 0.5 and 3 km from multiscale models. The results from the multiscale modeling and the limited local contribution suggest that Hong Kong and the surrounding region should closely cooperate to develop a better environment. © 2015 Elsevier Ltd.
Rui Y.,Nanjing University |
Shen D.,Nanjing University |
Shen D.,Changjiang River Scientific Research Institute |
Khalid S.,Nanjing University |
And 4 more authors.
Physics and Chemistry of the Earth | Year: 2015
The frequent occurrence of sudden water pollution accidents brings enormous risks to water environment safety. Therefore, there is great need for the modeling and development of early warning systems and rapid response procedures for current water pollution situation in China. This paper proposes an emergency response system based on the integration of Geographic Information System (GIS) technology and a hydraulic/water-quality model. Using the spatial analysis and three-dimensional visualization capabilities of GIS technology, we calculated pollutant diffusion measures, and visualized and analyzed the simulation results, in order to provide the services of early warning and emergency response for sudden water pollution accidents in the Xiangjia Dam area on the Yangtze River. The results show that the proposed system offers reliable technological support for emergency response to sudden water pollution events, and it shows good potential for wide applications in various aspects of water resources protection. © 2015 Elsevier Ltd.
Zhang S.-J.,Chinese Academy of Sciences |
Zhang S.-J.,Policy Research Center for Environment and economics |
Zhu A.-X.,Chinese Academy of Sciences |
Zhu A.-X.,Jiangsu Center For Collaborative Innovation In Geographical Information Resource Dev And Applied |
And 6 more authors.
Geoderma | Year: 2016
Legacy samples are a valuable data source for digital soil mapping. However, these sample sets are often small in size and ad hoc in spatial distribution. Constrained by the limited representativeness of such a sample set, the obtained soil maps are often incomplete in spatial coverage with "gaps" at the locations which cannot be well represented by these samples. The maps may also contain areas of high prediction uncertainty. In order to extend the predicted area and reduce prediction uncertainty, additional samples are needed. This paper presents a sampling design based on prediction uncertainty to select samples which will effectively complement the sparse and ad hoc samples, and maximize the spatial coverage of prediction and minimize prediction uncertainty. A case study in China shows that this sampling scheme was effective in achieving these goals. Compared with stratified random sampling scheme, when the number of additional samples is the same, the produced map using uncertainty directed samples has larger predicted area, and the accuracy of the produced map is higher than that of the maps using stratified random samples. The finding of this study suggests that prediction uncertainty is a useful indicator to aid field sample selection and to complement the legacy data. Furthermore, the mapping accuracy produced using this method can be quantitatively related to the number of additional samples needed which opens a new horizon for digital soil mapping. © 2015.
Zhu A.X.,Nanjing Normal University |
Zhu A.X.,Jiangsu Center For Collaborative Innovation In Geographical Information Resource Dev And Applied |
Zhu A.X.,CAS Institute of Geographical Sciences and Natural Resources Research |
Zhu A.X.,University of Wisconsin - Madison |
And 7 more authors.
European Journal of Soil Science | Year: 2015
Existing predictive soil mapping (PSM) methods often require soil sample data to be sufficient to represent soil-environment relationships throughout the study area. However, in many parts of the world with only a limited quantity of soil sample data to represent the study area, this is still an issue for PSM application. This paper presents a method, named 'individual predictive soil mapping' (iPSM), which can make use of limited soil sample data for PSM. With the assumption that similar environmental conditions have similar soils, iPSM uses the soil-environment relationship at each individual soil sample location to predict soil properties at unvisited locations and estimate prediction uncertainty. Specifically, the environmental similarities of an unvisited location to a set of soil sample locations are used in a weighted average method to integrate the soil-environment relationships at sample locations for prediction and uncertainty estimation. As a case study, iPSM was applied to map soil organic matter (SOM) content (%) in the topsoil layer using two sets of soil samples. Compared with multiple linear regression (MLR), iPSM produced a more accurate SOM map (root mean squared error (RMSE) 1.43, mean absolute error (MAE) 1.16) than MLR (RMSE 8.54, MAE 7.34) the ability of the sample set to represent the study area is limited and achieved a comparable accuracy (RMSE 1.10, MAE 0.69) with MLR (RMSE 1.01, MAE 0.73) when the sample set could represent the study area better. In addition, the prediction uncertainty estimated by iPSM was positively related to prediction residuals in both scenarios. This study demonstrates that iPSM is an effective alternative when existing soil samples are limited in their ability to represent the study area and the prediction uncertainty in iPSM can be used as an indicator of its prediction accuracy. © 2015 British Society of Soil Science.
Xiao J.,Nanjing Normal University |
Xiao J.,CAS Nanjing Institute of Geography and Limnology |
Xiao J.,Jiangsu Center For Collaborative Innovation In Geographical Information Resource Dev And Applied |
Xiao X.,CAS Nanjing Institute of Geography and Limnology |
And 3 more authors.
Review of Palaeobotany and Palynology | Year: 2015
A continuous 775-cm-long sediment core (Core B) was collected from the Dajiuhu Basin in the western Shennongjia Forest Region of Central China. The core between 775 and 144. cm in depth spanning the period from 83.4 to 9.6. ka (calibrated age, throughout this study) was studied for pollen analysis. The high-resolution pollen record revealed the histories of the vegetation succession and climate changes from 83.4 to 9.6. ka in the mountainous regions at an altitude of approximately 1,700. m. a.s.l. in Central China. The results show that five evident climate changes disclosed by the pollen record in Core B correspond to MIS (Marine Isotope Stage) 5a, MIS 4, MIS 3, the LGM (Last Glacial Maximum) of MIS 2, and the period from the deglacial of MIS 2 to the early Holocene, respectively. The temperature changes in the Dajiuhu Basin are consistent with the solar insolation in the Northern Hemisphere, the climate records in the Greenland and Guliya ice cores, the stalagmite, and the loess. However, the precipitation changes during the late Quaternary in the study area were roughly reversed with the temperature changes in the Northern Hemisphere. Therefore, the climatic patterns from 83.4 to 9.6. ka in the Dajiuhu Basin are cold and humid conditions and warm and dry conditions, which may be caused by the middle latitude position, the humid monsoon climate, and the steep mountainous geomorphology of the study area. © 2015 Elsevier B.V.