Effects of Mixing Granular Iron with Sand on the Kinetics of Trichloroethylene Reduction

A substantial cost of granular iron permeable reactive barriers is that of the granular iron itself. Cutting the iron with sand can reduce costs, but several performance issues arise. In particular, reaction rates are expected to decline as the percentage of iron in the blend is diminished. This might occur simply as a function of iron content, or mass transfer effects may play a role in a much less predictable fashion. Column experiments were conducted to investigate the performance consequences of mixing Connelly granular iron with sand using the reduction kinetics of trichloroethylene (TCE) to quantify the changes. Five mixing ratios (i.e., 100%, 85%, 75%, 50%, and 25% of iron by weight) were studied. The experimental data showed that there is a noticeable decrease in the reaction rate when the content of sand is 25% by weight (iron mass to pore volume ratio, Fe/V_p = 3548 g/L) or greater. An analysis of the reaction kinetics, using the Langmuir-Hinshelwood rate equation, indicated that mass transfer became an apparent cause of rate loss when the iron content fell below 50% by weight (Fe/V_p = 2223 g/L). Paradoxically, there were tentative indications that TCE removal rates were higher in a 15% sand + 85% iron mixture (Fe/V_p = 4416 g/L) than they were in 100% iron (Fe/V_p = 4577 g/L). This subtle improvement in performance might be due to an increase of iron surface available for contact with TCE, due to grain packing in the sand-iron mixture.     

近45年雅鲁藏布江流域极端气候事件趋势分析

利用雅鲁藏布江流域10个气象台站1961-2005年逐日最高气温、最低气温和日降水量资料,分析了该流域气温和降水等气候极端事件的变化趋势.研究表明:近45年以来,雅鲁藏布江流域夜间和白天极端低温日数分别以1.94和0.97天/10年的趋势在显著减少,夜间极端低温日数减少在冬季最明显,白天极端低温日数在秋季减少最明显:夜间极端高温日数和白天极端高温日数分别以3.03和1.26天/10年的速度显著增加,夜间极端高温日数增加在夏季最明显,白天极端高温日数增加在冬季最明显;日较差以0.11℃/10a的速度在显著减少,主要发生在冬季:最大的1天降水总量和逐年连续无降水天数有减少趋势,最大的5天降水总量、中雨天数、逐年平均降水强度和逐年连续降水天数有增加趋势,90年代以来增加趋势明显,与该地区经向风与水汽通量增加有关.     

第二届亚洲区域气候监测、预测和评估论坛在北京召开

1 会议概况 2006年4月6-8日第二届亚洲区域气候监测、预测和评估论坛(The Second Session of the Forum on Regional Climate Monitoring,Assessment and Prediction for Asia)在北京召开。论坛由中国气象局和世界气象组织(WMO)共同主办,中国科技部、国家自然科学基金委、中国外国专     

广域差分GPS系统完备性监测

广域差分 GPS系统完备性监测技术是广域差分的关键和核心。本文全面介绍了完备性监测技术的定义 ,完备性监测系统的构成 ,以及各个部分的监测方法 ,包括监测站和用户站的监测技术 ,最后给出了完备性监测的一般步骤。     

大气环流的年代际变化 II.GCM数值模拟研究

类似大气环流模式比较计划（AMIP）的数值模拟,将实际观测的海表水温（SST）资料引入模式进行40多年的数值积分,得到长时间的大气环流模拟结果。分析数值模拟结果发现,无论是大气中的主要涛动和遥相关型,还是重要大气环流系统都极为清楚地存在着年代际变化特征,包括10～20年准周期振荡和可能的30年以上的准周期振荡;而且上述主要环流系统的形势及其年代际变化大都与实际观测资料所给出的结果相一致。顺便分析中国东部气候的模拟结果,年代际变化特征（包括60年代的气候突变）也很清楚,并同大气环流变化配合十分合理。结果也表明,同研究季节和年际变化一样,大气环流模式（AGCM）数值模拟也是研究大气环流和气候年代际变化的有效方法。     

北京环城游憩带旅游地类型与空间结构特征

本文针对我国城市居民以城市周边为目的地近距离旅游日益增长的现象 ,以北京市行政区域内除东城、西城、崇文、宣武四个城区以外 14个区县中的 2 35处旅游地作为研究样本 ,按照地复合分类法根据旅游地的资源属性和旅游活动的性质将旅游地分为 9种类型 ,根据北京市情况可归并为 4类 ;运用空间结构、计量地理学理论以及地理信息系统、电话调查等技术手段 ,将四类 2 35处旅游地的大量数据分别进行了城市中心距离、回转半径法、空间分布曲线、空间离散指数等旅游计量地理研究 ,从而得出北京环城游憩带旅游地的空间结构特征     

低阶地球引力场长期变化的确定

利用约11年的Lageos人卫激光测距（SLR）资料,反演了地球引力场系数J2和J3变化的时间序列,分析得到每年的2＝(-2.6±0.4)×10-11,3＝(-1.2±0.4)×10-11及18.6年固体潮Love数k2=0.3154±0.0070,相位滞后ε=3.1°±2.0°.由此可以对地幔滞弹和地球各圈层的动力学变化及相互作用提供高精度的天文观测约束。为了提供高精度的J2和J3变化的时间序列,可能的误差源必须考虑,如自转速率变化引起的极潮,引力场系数Jn的低阶和高阶项之间的弱的耦合等。     

GRANITOIDS AND TETONIC EVOLUTION OF THE WEST KUNLUN OROGENIC BELT

GRANITOIDS AND TETONIC EVOLUTION OF THE WEST KUNLUN OROGENIC BELT     

动物蛋白酶1058水解ti鱼可溶性蛋白质

研究了动物蛋白酶 1 0 58水解鱼是鱼蛋白时 ,酶量、温度、作用时间对鱼是鱼蛋白质水解率和苦味的影响。结果表明 :酶浓度的提高 ,水解时间的延长 ,均使鱼是鱼蛋白水解率明显提高。最适水解温度为 50℃ ,当温度高于 50℃时 ,水解率逐渐下降 ,蛋白酶开始失活。苦味值随水解率提高而增加。用正交试验的方法 ,经综合分析和试验得出 ,该蛋白酶水解鱼是鱼的最佳条件是酶量与底物之比为 1 .5∶ 1 0 0 0 ;温度为 50℃ ;水解时间为 4h。     

Optimal lake-marsh pattern determination in lake-marsh systems based on the eco-hydrological processes management

The major hydrological factors in lake-marsh systems are water level (depth), water surface area, and water volume. The key index for determining the lake-marsh pattern is water level, which leads to the variation of lake-marsh patterns under natural hydrological alternations. In addition, the vegetation structure also affects the lake-marsh pattern. With socioeconomic development and climate change, the ‘land use’ and ‘water use’ competitions appear more seriously between a lake-marsh system and its surrounding socioeconomic system, also inside the lake-marsh system. The possible optimal lake-marsh pattern could solve the contradictions mentioned above. As few studies focus on this issue, this study proposed an optimal lake-marsh pattern determination method with eco-hydrological management on relieving the land use and water use competitions. The optimal lake-marsh pattern determination method considers the protection objects (water depth demands), water supply (precipitation, surface water, and groundwater), and water demand (especially evapotranspiration) in the system at annual and monthly scales. Calculation and analysis were performed for the optimal pattern of the Wolonghu Wetlands as an example. The results mainly showed that the lake-marsh pattern of the Wolonghu Wetlands cannot be achieved on meeting both the maximum ecological services values and minimum water shortage amount under present natural condition. With artificial regulation measures, the possible optimal annual lake-marsh patterns can be obtained based on both ecological and hydrological objectives, with the area ratio of lake and marsh in the range of 0.650:0.350 and 0.726:0.274, the corresponding water level of lake body was of 86.85 to 87.0 m. This study could provide references for the Wolonghu Wetlands management, also for similar lake-marsh systems and other ecological systems.