Analysis of spatio-temporal dynamic pattern and driving forces of urban land in China in 1990s using TM images and GIS

China has witnessed fast urban growth in the recent decade. This study analyzes spatio-temporal characteristics of urban expansion in China using satellite images and regionalization methods. Landsat TM images at three time periods, 1990/1991, 1995/1996, and 1999/2000, are interpreted to get 1:100000 vector land use datasets. The study calculates the urban land percentage and urban land expansion index of every 1 km(2) cell throughout China. The study divides China into 27 urban regions to conceive dynamic patterns of urban land changes. Urban development was achieving momentum in the western region, expanding more noticeably than in the previous five years, and seeing an increased growth percentage. Land use dynamic changes reflect the strong impacts of economic growth environments and macro-urban development policies. The paper helps to distinguish the influences of newly market-oriented forces from traditional administrative controls on China's urban expansion. (c) 2005 Elsevier Ltd. All rights reserved.

沈阳市城市扩展分析与模拟研究

城市扩展及其导致的土地利用/土地覆被变化作为全球环境变化的重要驱动因素，日益引起社会各界的普遍关注。新中国成立以来，沈阳市经历了快速的城市化过程，特别是进入21世纪以来，伴随着人口增长和经济发展，中心城区持续向外扩张，导致基本农田大量流失，区域景观和生态环境质量日益下降，给沈阳市的城市增长管理和可持续发展带来严峻挑战。 利用遥感(RS)、地理信息系统(GIS)和空间Logistic回归模型对1988-2004年间沈阳市的城市扩展与土地利用变化特征及其驱动力进行深入分析，并在此基础上利用基于细胞自动机(CA)的城市扩展模型－SLEUTH对历史时期(1988-2004年)的城市扩展格局进行模拟与重建，对未来(2005-2030年)不同发展条件下的城市扩展进行模拟与环境影响评估，以期为城市增长管理与区域可持续发展提供决策支持。本论文取得如下研究成果： (1) 1988-2004年间，沈阳市辖区城市面积持续增加，城市扩展强度逐渐增强；2000-2004年城市扩展规模和强度都达到最大；沈阳市城市化进程正在显著加速。城市扩展具有明显的空间分异特征：整个研究时段内，市区西南方向是城市扩展的主方向，中心城区周边(8~10km)及各级经济开发区是扩展的热点区域。 (2) 1988-2004年间，沈阳市辖区土地利用变化最主要的特征是耕地向城乡建设用地的大面积转换。持续的城市扩展导致区域景观日益破碎化和复杂化。城市和其它建设用地的景观影响日益增强，耕地的优势地位减弱，且破碎化程度增加，斑块形状日趋复杂。城市化空间梯度上的土地利用格局变化分析表明，随着城市化水平的提高，景观组成和空间配置发生了明显变化。处在城市化前沿区域的城郊地区，景观格局表现出景观多样性增加、破碎化程度加深和形状日趋复杂等特点。 (3) 1988-2004年间，沈阳市辖区城市扩展主要受到社会经济发展的推动作用和政策因素的激励与导向作用。空间Logistic回归分析显示，开发区建设与行政建制变化、道路与城镇分布、浑河和城市规划是城市空间扩展的主要影响因素。 (4) ROC曲线统计、Kappa统计与多分辨率误差估算以及景观指数从城市扩展总体预测能力、增长数量、空间位置和空间格局上给予SLEUTH模型一个全面、客观的评估。总体上来说，SLEUTH模型具有可信精度，较好地表达了沈阳市1988-2004年间城市扩展的总体趋势，对城市扩展面积的拟合精度很高。但是，与其它城市扩展模型相似，在像元尺度上对城市扩展空间位置的预测和对城市空间格局的表达还有待于提高；随着分辨率的降低，模型对城市发展中空间邻域关系的表达效果趋于提高。SLEUTH模型对城市扩展的总体模拟精度要高于空间Logistic回归模型，但是对城市扩展位置的模拟准确性低于后者。 (5) 通过分析发现，影响SLEUTH模拟准确性的主要因素包括模型结构、地方城市发展特征、模型应用的时空尺度和模型输入数据的获取与误差传递等。通过修改模型组分设置、开展模型敏感性与不确定性分析以及实行城市扩展一体化模拟可以提高SLEUTH模型的模拟效力，而具体实现方法需要深入研究。基于模型评估结果和效力提高的对策，对城市扩展演变的时空格局进行了较为准确的重建，为其相关研究提供了可靠的历史数据资料。 (6) 遵循沈阳市目前和未来的区域开发政策、最新修编的城市总体规划，以及社会对区域生态环境保护的要求，设计了五个城市发展预案，即目前趋势发展预案(CT)、区域开发政策与城市规划预案(PP)、生态可持续发展预案(ES)、紧凑式发展格局预案(CD)和特定增量发展预案(GA)。对不同预案条件下未来(2004-2030年)城市扩展面积和空间格局、城市扩展热点区域、城市景观格局变化及其景观生态效应，以及对其它类型土地资源的消耗四个方面进行了分析和比较，为沈阳市城市规划、生态建设以及可持续增长管理提供了许多有价值的决策信息。

Electrochemical quartz crystal microbalance study for vanadium hexacyanoferrates: monitoring of film growth and ion effects during redox reactions

An electrochemical quartz crystal microbalance was employed to monitor directly the growth of vanadium hexacyanoferrate (VHF) films on platinum substrates during electrodeposition and interfacial coagulation in the solution containing sulfuric acid electrolyte, vanadium(IV) and hexacyanoferrate(III). Mass changes of the gold/crystal working electrode were correlated with cyclic voltammetry data. Effects of cations (NH4+, Li+, Na+ and K+), anions (SO42- and NO3-) and solvent during redox reactions of the films were studied. The results show that cations were incorporated into the film during reduction and expelled from the film during oxidation. Solvent also participates in VHF electrochemistry, and its role cannot be neglected. Anions play no role in VHF electrochemistry. (C) 1997 Elsevier Science S.A.

Response of macrozoobenthos communities to ecological engineering remediation in a hypertrophic urban lake

The relationship of macrozoobenthos communities with some environmental variables, and their response to the ongoing restoration measures were studied in a small hypertrophic urban lake near the Yangzte River, China. Twenty taxa including 9 oligochaetes, 7 insects, 2 mollusks and two other animals were found during March 2005 to May 2006. The reappearance of some indigenous macrozoobenthos species showed that the ecological engineering remediation carried out was helpful for the recovery of the macrozoobenthos communities. Through canonical correspondence analysis (CCA), it was detected that temperature (T), conductivity (COND), Secchi depth/deep (SD/Deep), TN, total suspended solids (SS) and chemical oxygen demand (CODcr) were significant environmental factors that influenced the pattern of macrozoobenthos. Limnodrilus hoffmeisteri, Tanypus sp. and Alocinma longicornis could be used as potential bio-indicators in monitoring the development of ecological restoration.

Effects of ytterbium ion on the growth, metabolism and membrane fluidity of Tetrahymena thermophila

Power-time curves and metabolic properties of Tetrahymena thermophila BF5 exposed to different Yb3+ stop levels were studied by ampoule method of isothermal calorimetry at 28 degrees C. Metabolic rate (r) decreased significantly while peak time (PT) increased with the increase of Yb3+ stop. These results were mainly due to the inhibition of cell growth, which corresponded to the decrease of cell number obtained by cell counting. Compared with cell counting, calorimetry was sensible, easy to use and convenient for monitoring the toxic effects of Yb3+ stop on cells and freshwater ecosystem. It was also found that cell membrane fluidity decreased significantly under the effects of Yb3+ stop, which indicated that Yb3+ could be membrane active molecules with its effect on cell membranes as fundamental aspect of its toxicity.

Monitoring bioaccumulation and toxic effects of hexachlorobenzene using the polyurethane foam unit method in the microbial communities of the Fuhe River, Wuhan

Hexachlorobenzene (HCB) is a chlorinated aromatic hydrocarbon that was widely used for seed dressing in prevention of fungal growth on crops, and also as a component of fireworks, ammunition, and synthetic rubbers. Because of its resistance to degradation and mobility, HCB is widely distributed throughout the environment and is accumulated through food chains in different ecosystems. In this study, a preliminary investigation was carried out on the bioaccumulation and the toxic effects of HCB in the microbial (protozoan in particular) communities in the Fuhe River, Wuhan, a water body receiving industrial wastewaters containing HCB and other pollutants, using the standardized polyurethane foam units (PFU) method. Field samples were taken from eight stations established along the Fuhe River in January and August 2006. The concentration ratios of HCB in microbial communities and in water were 9.66-18.64, and the microbial communities accumulated 13.29-56.88 mu g/L of HCB in January and 0.82-10.25 mu g/L HCB in August. Correlation analysis showed a negative correlation between the HCB contents in the microbial assemblage, and the number of species and the diversity index of the protozoan communities. This study demonstrated the applicability of the PFU method in monitoring the effects of HCB on the level of microbial communities.

Land-cover changes in an urban lake watershed in a mega-city, Central China

Urbanization can exert a profound influence on land covers and landscape characteristics. In this study, we characterize the impact of urbanization on land cover and lacustrine landscape and their consequences in a large urban lake watershed, Donghu Lake watershed (the largest urban lake in China), Central China, by using Landsat TM satellite images of three periods of 1987, 1993 and 1999 and ground-based information. We grouped the land covers into six categories: water body, vegetable land, forested land, shrub-grass land, open area and urban land, and calculated patch-related landscape indices to analyze the effects of urbanization on landscape features. We overlaid the land cover maps of the three periods to track the land cover change processes. The results indicated that urban land continuously expanded from 9.1% of the total watershed area in 1987, to 19.4% in 1993, and to 29.6% in 1999. The vegetable land increased from 7.0% in 1987, 11.9% in 1993, to 13.9% in 1999 to sustain the demands of vegetable for increased urban population. Concurrently, continuous reduction of other land cover types occurred between 1987 and 1999: water body decreased from 30.4% to 23.8%, and forested land from 33.6% to 24.3%. We found that the expansion of urban land has at least in part caused a decrease in relatively wild habitats, such as urban forest and lake water area. These alterations had resulted in significant negative environmental consequences, including decline of lakes, deterioration of water and air quality, and loss of biodiversity.

Application of polyurethane foam units and calorimetry to microbial monitoring in Lake Donghu

Combined with the national standard biomonitoring method (polyurethane foam units method), calorimetry was applied to study the metabolic activities of PFU microbial communities in fresh water to determine the effects of anthropotgenic stresses on the activity of the microbial community. Comparisons were made at four sampling stations with different eutrophic status in Lake Donghu. Water quality variables, species number of protozoa, abundances of microorganisms, biomass, heterotrophy indexes and diversity indexes are reported. The heat rate-time curves of the native and concentrated PFU microbial communities were determined at 28 degrees C. Growth rate, measured maximum power output and total heat were calculated from the heat rate-time curves. The values of metabolic variables are higher at the more eutrophic stations, which suggests that organic pollution increases the activity of PFU microbial communities. The metabolic variables are in good agreement with chemical and biotic variables. And calorimetry will be useful for biomonitoring of the PFU microbial community. (C) 2005 Elsevier B.V. All rights reserved.

Parasitic reaction and its effect on the growth rate of AlN by metalorganic chemical vapor deposition

The Al composition of metalorganic chemical vapor deposition (MOCVD)-grown AlGaN alloy layers is found to be greatly influenced by the parasitic reaction between ammonia (NH3) and trimethylaluminum (TMAI). The growth process of AlN is carefully investigated by monitoring the in situ optical reflection. The abnormal dependencies of growth rate on growth temperature, reactor pressure, and flux of NH3 are observed and can be well explained by the effect of parasitic reaction. The increase of growth rate with increasing flux of TMAI is found to depend on the growth temperature and reactor pressure due to the presence of parasitic effect. A relatively low growth temperature and a reduced reactor pressure are suggested for the effective decrease of parasitic reaction during the MOCVD growth of AlN and probably lead to a more effective incorporation of Al into the AlGaN layers. (c) 2005 Elsevier B.V. All rights reserved.

Experiment on Qinghai-Tibet railroad subgrade temperature monitoring based on FBG sensors

Qinghai-Tibet Railway is the longest and highest plateau railway in the world. A long term monitoring system of the stability of the subgrade in the permafrost regions should be put forward immediately to prevent damage to the railway. As it's very difficult to set up the long-distance automatic monitoring system which contains a lot of measure points along the 550 kilometers railway in the permafrost area, we present a subgrade temperature monitor system based on fiber Bragg grating (FBG). In this paper the principles of the FBG was presented, and the feasibility of the FBG sensors in the permafrost area of Qinghai-Tibet plateau was analysized. We embedded fifteen FBG temperature sensors and thermal resistance temperature sensors. A contrast experiment is made while the two kinds of sensors are arranged in the same position. The result of the experiment shows that the accuracy of the FBG temperature sensors is less than 0.1 degrees C. and the FBG sensors can do well in the measurement of pattern which the temperature varies with the depth of the permafrost soil. The result also shows the stability of the FBG sensors in the bad environmental condition of Qinghai-Tibet plateau, which proves the feasibility of the application of FBG sensors and our monitoring system on the Qinghai-Tibet railway.

Spatio-temporal patterns and driving forces of urban land expansion in china during the economic reform era

Along with its economic reform, China has experienced a rapid urbanization. This study mapped urban land expansion in China using high-resolution Landsat Thematic Mapper and Enhanced Thematic Mapper data of 1989/1990, 1995/1996 and 1999/2000 and analyzed its expansion modes and the driving forces underlying this process during 1990-2000. Our results show that China's urban land increased by 817 thousand hectares, of which 80.8% occurred during 1990-1995 and 19.2% during 1995-2000. It was also found that China's urban expansion had high spatial and temporal differences, such as four expansion modes, concentric, leapfrog, linear and multi-nuclei, and their combinations coexisted and expanded urban land area in the second 5 y was much less than that of the first 5 y. Case studies of the 13 mega cities showed that urban expansion had been largely driven by demographic change, economic growth, and changes in land use policies and regulations.

Monitoring microbial populations of sulfate-reducing bacteria using an impedimetric immunosensor based on agglutination assay

An impedimetric immunosensor was fabricated for rapid and non-labeled detection of sulfate-reducing bacteria, Desulforibrio caledoiensis (SRB) by immobilizing lectin-Concanavalin A using an agglutination assay. The immobilization of lectin was conducted using amine coupling on the surface of a gold (Au) electrode assembled with 11-Mercaptounclecanoic acid. Electrochemical impedance spectroscopy (EIS) was used to verify the stepwise assembly of the sensor system. The work conditions of the impedimetric immunosensor, such as pH of the buffer solutions and the incubation time of lectin, were optimized. Faradic impedance spectra for charge transfer for the redox probe Fe(CN)(6)(3-/4-) were measured to determine SRB concentrations. The diameter of the Nyquist diagram that is equal to the charge-transfer resistance (RI) increased with increasing SRB concentration. A linear relationship between R-ct and SRB concentration was obtained in SRB concentration range of 1.8 to 1.8 x 10(7) cfu/ml. The variation of the SRB population during the growth process was also monitored using the impedimetric immunosensor. This approach has great potential for simple, low-cost. and time-saving monitoring of microbial populations. (C) 2009 Elsevier B.V. All rights reserved.