汉江中游河谷平原植被指数时空变化及其与沙化土地动态的关联关系

针对沙化土地广泛分布的汉江中游河谷平原区,采用MODIS EVI数据分析2003~2011年区域植被状态时空变化,并据此探讨沙化土地的动态特征。利用时序植被指数统计分析,探讨研究区植被的总体变化规律;分析不同缓冲区植被指数的空间分布格局,反映了区域环境状况的空间差异以及由此而可能产生的土地利用格局的变化;并基于不同距离缓冲区的EVI时空差异对比分析,探讨沙化土地动态与植被变化的关联关系。研究表明,近9 a来汉江中游河谷平原区EVI呈明显上升趋势;随着离河流距离的逐渐增加,每千米范围内各年的年均EVI值均表现出先增大后减小的空间特征,并在距河3 km区域处EVI值达到最大;而EVI的时空差异,则体现了沙化土地的空间分布与动态特征     

Opportunities and challenges for development of urbanization in Western China

Urban and rural dual structure in Western China is obvious.The economic development of the central cities is relatively quick while that of the rural areas is lagging behind.The speeding up of urbanization contributes to the intensively uncoordinated development of urban and rural areas.Besides,the eco-fragile environment,shortage of available water resources,adverse geographic location,and relatively backward social economy restrict the development of urbanization in Western China.However,Western China also has the advantages of backwardness.This paper analyzes the present situation and development trend of urbanization in Western China.The results show that Western China has basically formed a development pattern with"industry promotes agriculture and urban leads to village".Therefore,combined with the present situation of Western China,this paper describes and analyzes the opportunities and challenges that may appear in the process of urbanization in Western China,puts forward the development pattern in which urban and rural areas can gain mutual support and co-development,and provides related recommendations.     

辽宁省自然灾害及基本特点

辽宁是一个自然灾害较多的省,地质灾害、气象灾害、海洋灾害、农业灾害和林业灾害部比较频繁。本文在总结上述灾害的基础上,指出了辽宁自然灾害的特点,即自然灾害的分布严格受自然地理和地质构造条件的控制;人类生产活动恶化了原有的自然环境,从而加速了灾害的发生和发展;灾害类型多,成灾面积广;灾害的频度逐年增加。     

滇池周边浅层地下水硝酸盐来源及转化过程识别

明确硝酸盐的主要来源及转化过程对地下水氮污染防治和水资源开发利用具有重要意义.为了探明滇池周边浅层地下水中硝酸盐污染现状及来源,于2020年雨季（10月）和2021年旱季（4月）在滇池周边共采集73个浅层地下水样,运用水化学和氮氧同位素（δ¹⁵N-NO₃^-、δ¹⁸O-NO₃^-）识别浅层地下水中硝酸盐的空间分布、来源及转化过程,并结合同位素混合模型（SIAR）定量评价不同来源氮对浅层地下水硝酸盐的贡献.结果表明,旱季浅层地下水中有40.5%的采样点ρ（NO₃^--N）超过地下水质量标准（GB/T 14848）Ⅲ类水质规定的20 mg·L^-1,雨季超过47.2%的采样点ρ（NO₃^--N）超过20 mg·L^-1.氮氧同位素和SIAR模型分析结果证明了土壤有机氮、化肥氮、粪肥和污水氮是浅层地下水硝酸盐的主要来源,以上氮源对旱季浅层地下水中硝酸盐的贡献率分别为13.9%、11.8%和66.5%,对雨季的贡献率分别为33.7%、31.1%和25.9%,而大气氮沉降贡献率仅为8.5%,对该区浅层地下水中硝酸盐来源贡献较小.硝化作用是旱季浅层地下水中硝态氮转化的主导过程,雨季以反硝化作用为主,且反硝化作用雨季比旱季明显.     

Type 0092丝状菌污泥微膨胀在短程硝化中的实现

利用Type 0092丝状菌不易引发污泥恶性膨胀的特点,本实验采用实际生活污水,以SBR反应器接种短程硝化污泥,考察了短程硝化状态下启动Type 0092丝状菌污泥微膨胀的特性,研究了系统启动与维持期间的污泥沉降性能、亚硝酸盐积累率(NAR)、污染物去除特性以及污泥菌群结构变化情况.结果表明控制DO为0. 3～0. 8 mg·L~(-1),F/M(以COD/MLSS计)=0. 24 kg·(kg·d)~(-1),按照交替缺氧/好氧模式运行(单周期3次,缺氧∶好氧=20 min∶60 min),能够启动Type 0092丝状菌污泥微膨胀与短程硝化耦合,系统SVI值维持在180 m L·g~(-1)左右,NAR一直维持在99%左右,COD和TN去除率能够分别提高约13%和5%,相较于传统全程硝化非微膨胀状态曝气量能节省约62. 5%.当交替缺氧/好氧模式变为单周期交替6次,缺氧∶好氧=10 min∶30 min,亚硝酸盐氧化菌(NOB)的活性会恢复,使短程硝化被破坏;低溶解氧、交替缺氧/好氧、低负荷是实现Type 0092丝状菌污泥微膨胀的关键因素,当负荷(以COD/MLSS计)大于0. 25 kg·(kg·d)~(-1)时,仅靠低溶解氧和间歇曝气无法维持污泥微膨胀状态.     

Solubilization of mixed polycyclic aromatic hydrocarbons through a rhamnolipid biosurfactant

The solubilization of phenanthrene (PHE) and pyrene (PYR) by rhamnolipid biosurfactant was systematically investigated. The solubilities of both polycyclic aromatic hydrocarbons (PAHs) were increased linearly with the biosurfactant concentration at above critical micelle concentration. A competitive effect was observed between PHE and PYR. The solubility of PHE in a mixed system was lower than that in a single PAH system, whereas the solubility of PYR in a mixed system was enhanced. This is because the hydrophobicity of PYR is higher than that of PHE, so PYR is favored in the competitive solubilization. The combined effect of biosurfactant and dissolved organic matter (DOM) on PAH solubilization was also examined. Two kinds of DOM (derived from soil and from compost) were used. There was an obvious enhancement of solubility for PHE and PYR in systems with concurrence of DOM and biosurfacrant compared with systems with only DOM or biosurfactant; however, the enhancement in the mixed system was less than their additive. This could be explained as the formation of a DOM-biosurfactant complex. In addition, the solubility enhancement of PAHs in a compost-DOM system was higher than that in a soil-DOM system. This could be explained as functional group differences of two DOM types.     

可靠性增长摸底试验方法研究分析

介绍了可靠性增长摸底试验方法的适用范围,对其试验对象进行了探讨,并对如何确定最佳试验时间的两种方法进行了研究.分析指出试验应力的选取也是影响可靠性增长摸底试验效果的关键因素,并用具体试验方案举例说明其有效性,证明了开展可靠性增长摸底试验这项工作可达到快速有效、节约经费的作用.     

大型超市安全管理的定量评价研究

为了有效地评估大型超市的安全管理情况,提高其安全管理水平,根据大型超市的主要危险因素、事故特点等,从安全管理组织和制度、员工的安全管理、设备设施的安全管理、商品安全管理、环境安全管理和事故应急管理六个方面建立了大型超市安全管理定量评估指标体系。该指标体系共分为两级指标,采用层次分析法确定一级指标权重,采用德尔菲专家咨询法确定二级指标权重,建立了大型超市安全管理定量评估模型。为方便对大型超市的安全管理情况进行准确、快速地评估,利用于EXCEL软件建立了大型超市安全管理定量评估系统。     

资源环境承载力研究的缘起与发展

随着我国学习实践科学发展观的不断深入,理论和实践界越来越重视在资源环境承载力的允许范围内推进经济的可持续发展.回顾资源环境承载力相关研究的缘起与理论演变,从理论层面上对资源环境承载力相关问题进行系统梳理,理清脉络,这是正确制定和实施可持续发展战略的理论前提.     

Stress-induced recombination and the mechanism of evolvability

The concept of evolvability is controversial. To some, it is simply a measure of the standing genetic variation in a population and can be captured by the narrow-sense heritability (h²). To others, evolvability refers to the capacity to generate heritable phenotypic variation. Many scientists, including Darwin, have argued that environmental variation can generate heritable phenotypic variation. However, their theories have been difficult to test. Recent theory on the evolution of sex and recombination provides a much simpler framework for evaluating evolvability. It shows that modifiers of recombination can increase in prevalence whenever low fitness individuals produce proportionately more recombinant offspring. Because recombination can generate heritable variation, stress-induced recombination might be a plausible mechanism of evolvability if populations exhibit a negative relationship between fitness and recombination. Here we use the fruit fly, Drosophila melanogaster, to test for this relationship. We exposed females to mating stress, heat shock or cold shock and measured the temporary changes that occurred in reproductive output and the rate of chromosomal recombination. We found that each stress treatment increased the rate of recombination and that heat shock, but not mating stress or cold shock, generated a negative relationship between reproductive output and recombination rate. The negative relationship was absent in the low-stress controls, which suggests that fitness and recombination may only be associated under stressful conditions. Taken together, these findings suggest that stress-induced recombination might be a mechanism of evolvability.