操作条件对膜生物反应器运行经济性的影响

以运行费用作为膜生物反应器(MBR)运行经济性的考核指标,建立了MBR运行费用的计算模型,重点考察了膜通量、曝气强度、抽停时间、混合液悬浮固体质量浓度等操作条件对MBR运行经济性的影响.结果表明,膜通量在临界值5 L/(m2·h)时运行费用处于最低值;曝气强度过高或过低都会使系统运行费用增加,而经济曝气强度(气水比)为30:1;当抽吸时间≤12 min、停抽时间≥3 min时,运行费用变化缓慢,但抽吸时间或停抽时间超过临界值后,运行费用迅速上升;混合液悬浮固体质量浓度高于5.0 g/L时,运行费用随混合液悬浮固体质量浓度增加迅速递增.工程运行表明,运行费用模型预测值与实际值具有较好的一致性.     

Upscaling heterogeneity in aquifer reactivity via the exposure-time concept: inverse model

A novel inverse technique is proposed to quantitatively characterize macroscopic variability in aquifer reactivity in a Lagrangian representation. Reactivity heterogeneity is expressed in terms of distributions of flux over cumulative time of exposure of the solution to reactive surface area, termed here 'cumulative reactivity'. In cases involving single aqueous species the combined effects of physical and reactivity heterogeneity on reactive solute transport can often be established and further investigated through joint distributions of flux over travel time and cumulative reactivity. The inverse technique requires the breakthrough curve of a passive tracer to determine the distribution of flux over travel time, and additional breakthrough curves of reactive tracers provide additional moments of the distribution of flux over cumulative reactivity given travel time. Thus breakthroughs of one passive and two reactive tracers can provide the mean and variance of the distribution of flux over cumulative reactivity. This Lagrangian characterization is achieved with knowledge of the types of reactive surfaces present, but not their spatial locations. The distributions can subsequently be applied via forward modeling using the same technique to predict breakthrough curves of other solutes undergoing first-order reactions in similar physically and chemically heterogeneous configurations.     

Toxicity of Heavy Metals on Scenedesmus quadricauda (Turp.) de Brébisson in Batch Cultures (7 pp)

Background Aquatic environments are often exposed to various pollutants like heavy metals that are released from industrial, agricultural and domestic wastes. Emissions of heavy metals can then enter all ecosystems and bring about severe problems in plants, especially algae depending on the concentrations of a given element. The objective of the investigation presented is to detect toxic effects due to some heavy metals in the biomass of green alga Scenedesmus quadricauda. Methods All experiments were conducted with axenic cultures of the green alga Scenedesmus quadricauda (Turp.) de Brebisson (Chlorococcales, Chlorophyta). The cultures were grown in Chu-no.10 medium, and optimum physical and chemical growth conditions were provided to get higher growth rates and lower doubling times of cells. Growth of the micro algal cultures was measured on a daily schedule by counting cultures and determination of chlorophyll-a. The sterile-filtered heavy metal concentration solutions (Cd, Pb and Cu) were prepared and added as stock solutions of their salts (CdCl2*2.5 H2O, Pb(NO3)2*H2O and CuSO4*5 H2O). Results and Discussion The growth decreased gradually with the alga exposed to Cd at 0.05, 0.1, and 0.5 mg/L in comparison with the control whereas 1 mg/L Cd2+ had a clearly destructive effect. The growth was decreased with Pb at 15, 20 and 25 mg/L gradually, while at 30 mg/L the effect was more pronounced. When Cu was used, the growth was increased gradually at 0.5, 1 and 1.5 mg/L and vice versa at 2 mg/L. Conclusion There were differences in toxic effects of the metals with different metal as well as their concentrations and the time of exposure.     

多空间尺度景观格局与地表水质响应关系研究

截至2020年底,北京市已建成466条生态清洁小流域,其中,密云水库上游(北京境内)179条小流域,将于2022年底全部达到生态清洁小流域标准.本研究对密云水库流域进行子流域划分并创建缓冲区,通过汛期水质监测,结合统计分析和景观格局指数计算,量化不同空间尺度景观格局和水质的响应关系.结果表明:①密云水库主要河流水质除总...     

我国耕地资源数量安全的时空差异分析

耕地资源数量安全是耕地资源安全非常重要的组成部分，它受到资源禀赋、经济发展水平、管理和政策等因素的影响。本文在分析耕地资源数量安全影响因素的基础上，构建其评价指标体系，并对我国耕地资源数量安全的时空差异规律进行了分析，结果表明。自改革开放以来，我国耕地资源数量安全状况呈先增后减的变化趋势；从安全水平的区域分布来看，北部和西部省份的安全水平普遍高于东部和南部省份，同时发现，区域安全水平与经济发展水平呈负相关关系。     

Multi-scales Analysis of Driving Forces on Land Use/Cover Change in China： Taking Farmland Returning to Forest or Grassland as a Case

Increasing populations are causing an increase in food demands, and the area of cultivated land expands every year. Inappropriate land transition from ecology to production results in the constant decline of the ecological security level and influences the regional sustainable development. Adjusting unreasonable land use mode and reconstructing natural land cover are important ways to maintain and improve the ecological environment. Also reclaiming farmland as areas for forests and grasslands （FRFG） is another way. Successful implementation of FRFG in China is the result of comprehensive effect of the multi-scales driving forces. This paper analyses the driving forces of FRFG in China on a national （country） -regional （province） - local （county） - household （farmer） level scale, and the results are： driving forces at the national scale include ecological and food security and the western development of China; at the regional scale, ecological and economic benefits become the main factors to influence the dimension of FRFG under the same policy. The driving forces can be divided into 6 types： industrial structure adjustment, water source protection, flood prevention, the Three-Gorge Project protection, reduction of the amount of sediment flowing into the Yellow River and wind erosion desertification prevention. The driving forces at the local scale can be divided into 12 types with developing leading industries, increasing farmers＇ income and improving agricultural production conditions as the main types; at the household scale, the national policy meeting farmers＇ demands and the optimization of individual interests are all driving forces.     

区域二氧化硫控制优化模型研究

传统的区域二氧化硫控制优化都是基于损害函数法和环境标准化法的。本文在分析比较了传统二氧化硫污染控制战略优化中的损害函数法和环境标准化法各自的优点与局限的基础上。建立了基于时间序列决策的整数规划优化模型。这一理论模型更好地描述了控制战略实施的过程。把时间作为模型优化的一个因子。这种基于时间序列的过程充分考虑了货币的时间价值。并能分析这些时间价值对二氧化硫污染控制战略的动态过程影响。本文的模型是更加符合现实的情况。它对于区域二氧化硫控制的中长期决策优化显得更为有效和准确。     

激光质谱法对机动车尾气中污染物的测量

本文详细介绍了一种全新的污染物测试方法———激光质谱法的原理和特点。我们应用这一方法对机动车尾气进行了初步探测 ,得到了 2 6 6nm激光作用下汽车尾气的激光电离质谱图 ,并对摩托车发动机运行状态与苯系列污染物排放量之间的关系进行了初步的在线测量     

人口统计的时空分析

本文以国际和国内人口统计的空间分析实验和动态分析为案例 ,阐述人口统计的科学分析方法及其在国民经济建设、城市化建设与国家安全等诸多方面的重要意义 ;指出“格网”数据库作为一种中间载体 ,有利于卫星遥感象元与人口数据的空间数据融合 ,有利于认识人口动态变迁的规律     

不同空间尺度的江苏省区域经济差异研究

运用基尼系数、空间自相关等方法分析改革开放以来县域和地级市空间尺度下的江苏省区域经济差异变化及其空间机制。研究表明:改革开放以来江苏省县域和地级市尺度的区域经济差异在2008年前均呈扩大趋势,以后差距缩小,且县域尺度大于地级市尺度。在县域和地级市尺度上江苏省区域经济差异均存在明显的空间正相关关系,且不断增强,在县域尺度空间集聚更强。在地级市水平上,苏北的低水平集聚是其产生区域差异的主要原因,而在县域尺度上则苏南的高水平集聚是江苏区域差异主要原因。针对江苏省区域经济差异重点关注县域尺度的区域差异,在地级市尺度上侧重提升落后地区发展水平,而在县域空间尺度上以促进高水平地区的空间扩散为主。