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Carex meadows are critical habitat for wintering geese in the floodplains of the middle and lower reaches of Yangtze River, China. These meadows follow a growth cycle closely tied to the seasonal hydrological fluctuation: as water levels recede in the fall, exposed mudflats provide habitat for Carex spp. growth. The seasonal growth of Carex overlaps the arrival of wintering geese and provides an important food source for the migrants. Recent alterations to the Yangtze’s hydrology, however, have disrupted the synchronous relationship between water levels, Carex growth and wintering geese at Dongting Lake. In October 2012, we carried out an outdoor mesocosm experiment to investigate potential impacts of delayed water recession on the germination and growth of Carex heterolepis, the dominant Carex species at Dongting Lake, to understand how changes in hydrology might impact wintering goose habitat. Results showed that the delayed flood recession exerted significant impact on the first growth cycle of Carex growth. Prolonged inundation significantly lowered the intrinsic growth rate (P = 0.03) and maximum growth rates (P = 0.02). It also took significantly longer time to reach the peak growth rate (P = 0.04 and 0.05 for number of shoot and biomass, respectively). As a result, biomass accumulation was reduced by 45, 62 and 90 % for 10-day, 20-day and 30-day inundation treatments, respectively. These results indicate a severe risk of food shortage for wintering geese when water recession delayed. This potential risk should be taken into consideration when operating any hydrological control structures that alter the flood regimes in Dongting Lake. 相似文献
413.
ABSTRACTThis paper establishes a diagnostic model for assessing the rationality of size structure of urban agglomerations (UAs) in China. The model is designed to determine from a three-dimensional index including size distribution index (SDI), size compactness index (SCI), and size efficiency index (SEI). The spatio-temporal pattern of size structure involving the studied 19 UAs and its implications are explored. The results indicate that size structure of China’s UAs advanced from a low rationality development stage to a moderate rationality development stage in 1995–2015. Among them, the SDI and SEI were reasonably high, and the SCI was relatively low. Spatially, the high rationality UAs were distributed across eastern China, while the low rationality UAs were located in western China. UAs with positive size structure possessed typically a dual- or multicenter urban structure, while UAs with negative size structure usually presented as a single-center structure. The evolutionary trajectories of rationality of size structure of UAs can be summarized as four different stages. Our findings suggest that, in addition to consolidating the status of national-level UAs, the development of regional-level UAs should be promoted. Also, the fostering focus and direction should be oriented toward an UA with dual- or multicenter spatial structure. 相似文献
414.
Pian Feng Xiaohong Guan Yuankui Sun Wonyong Choi Hejie Qin Jianmin Wang Junlian Qiao Lina Li 《环境科学学报(英文版)》2015,27(5):175-183
Weak magnetic field(WMF) was employed to improve the removal of Cr(VI) by zero-valent iron(ZVI) for the first time. The removal rate of Cr(VI) was elevated by a factor of 1.12–5.89 due to the application of a WMF, and the WMF-induced improvement was more remarkable at higher Cr(VI) concentration and higher p H. Fe2+was not detected until Cr(VI) was exhausted, and there was a positive correlation between the WMF-induced promotion factor of Cr(VI) removal rate and that of Fe2+release rate in the absence of Cr(VI) at pH 4.0–5.5. These phenomena imply that ZVI corrosion with Fe2+release was the limiting step in the process of Cr(VI) removal. The superimposed WMF had negligible influence on the apparent activation energy of Cr(VI) removal by ZVI, indicating that WMF accelerated Cr(VI)removal by ZVI but did not change the mechanism. The passive layer formed with WMF was much more porous than without WMF, thereby facilitating mass transport. Therefore,WMF could accelerate ZVI corrosion and alleviate the detrimental effects of the passive layer, resulting in more rapid removal of Cr(VI) by ZVI. Exploiting the magnetic memory of ZVI, a two-stage process consisting of a small reactor with WMF for ZVI magnetization and a large reactor for removing contaminants by magnetized ZVI can be employed as a new method of ZVI-mediated remediation. 相似文献
415.
放射性同位素示踪法测吸水剖面工艺在油田已应用很久了。吉林油田应用低毒性同位素(113) ̄In测吸水剖面工艺,较好地解决了安全与环境污染问题。叙述了(113) ̄In的产生原理,在吉林油田的试验应用以及使用(113) ̄In测吸水剖面对环境的影响等。对从事油田测井的工程技术人员有一定的借鉴、指导作用。 相似文献
416.
Functional Properties of Extruded Starch Acetate Blends 总被引:1,自引:0,他引:1
Starch acetate, with degree of substitution of 2, was blended with 0, 7.5 and 15% polylactic acid (PLA), Eastar Bio Copolyester 14766 (EBC) or Mater-Bi ZF03U (MBI) and 10%, 13%, or 16% (d.b.) ethanol and twin-screw extruded at 160°C barrel temperature. Physical characteristics of the extrudates, such as radial expansion ratio, unit and bulk densities, and of the mechanical properties, including unit spring index and bulk spring index, were measured. Type of polymer, polymer content, and ethanol content significantly affected the physical characteristics and mechanical properties. The sample extruded with 7.5% PLA and 13% ethanol had the highest expansion ratio and bulk spring index. The sample with 15% MBI and 16% ethanol had the lowest unit density, while the sample with 7.5% PLA and 16% ethanol had lowest bulk denisty. The highest unit spring index was expressed in the sample containing 7.5% PLA and 10% ethanol. 相似文献
417.
418.
膜分离工艺在食品工业清洁生产中的应用 总被引:7,自引:0,他引:7
结合典型例子介绍了膜分离工艺在食品工业清洁生产中的应用,论述了膜技术在食品工业中应用的现状和发展情况。 相似文献
419.
溢油应急系统中的潮流快速预报 总被引:2,自引:2,他引:2
本文针对海上溢油动态预报可视系统中潮流场的预报提供了一种简便、快捷的预报方法。首先按潮流数值模拟计算出连续15个周日各网格结点处整点时刻潮流的东、北分量、进而求出各结点的潮流调和常数。在溢油预报时,可用此调和常数迅速算出实时潮流场而不必进行数值计算,提高预报实效。经辽东湾海区试用表明,该方法可靠,快捷,特别适用于微机预报系统。 相似文献
420.