钙钛矿型La_(0.8)Ce_(0.2)Fe_(1-x)Co_xO_3催化剂的制备及其三效催化活性

采用自燃烧法制备了一组钙钛矿型复合氧化物La_(0.8)Ce_(0.2)Fe_(1-x)Co_xO_3(x=0.9,0.7,0.5,0.3,0.1),并考察了其对CO、C_3H_6和NO的三效催化活性。XRD和SEM表征结果显示,La_(0.8)Ce_(0.2)Fe_(1-x)Co_xO_3具有良好的钙钛矿型晶体结构,晶粒大小为纳米级并自组装成片状结构。催化剂的比表面积为14.73~22.43 m~2/g,含有微孔和介孔结构。催化活性评价结果表明:La_(0.8)Ce_(0.2)Fe_(0.1)Co_(0.9)O_3具有很好的三效催化活性,在理论空燃比的条件下,CO、C_3H_6和NO的起燃温度分别为195℃、264℃和290℃,完全转化温度分别为239℃、418℃和415℃,低温三效催化活性良好;Fe和Co的掺杂量同时影响着La_(0.8)Ce_(0.2)Fe_(1-x)Co_xO_3的催化效果。     

城市轨道交通车站应急疏散方案决策研究

城市轨道交通应急疏散方案决策是1个多准则决策问题,传统方法难以将决策者的偏好与风险倾向纳入考虑,因此引入累积前景理论与集对分析,得到1种结合累积前景理论与集对分析的决策方法。该方法考虑决策者面对风险时的态度,计算出方案的累积前景值;引入集对分析,通过时间权重与准则权重将前景值与集对势联系起来,计算出方案综合集对势,并利用其大小对备选方案进行排序;最后通过实例计算以及对权重的扰动分析,验证了方法有效性。     

山地草甸退化对土壤速效养分的影响

以江西省武功山草甸为研究对象,分析不同海拔高度(1 600~1 900m)和不同土层(0~20cm和20~40cm)的草甸土壤有机质、p H值和速效养分对草甸退化的响应。结果表明:(1)在武功山草甸区各个海拔,草甸退化均使土壤有机质和速效养分含量有所下降,并且对表层土的影响要大于深层土。(2)草甸退化使得碱解氮和速效磷间的相关性减弱,速效钾和碱解氮、有效磷之间的相关性加强,土壤p H值与碱解氮之间由不显著相关变为极显著负相关(R=-0.637,P0.01)。     

Distribution of the environmental and socioeconomic risk factors on COVID-19 death rate across continental USA: a spatial nonlinear analysis

Environmental Science and Pollution Research - The COVID-19 outbreak has become a global pandemic. The spatial variation in the environmental, health, socioeconomic, and demographic risk factors of...     

基于GIS与SketchUp的矿井三维可视化方法研究

为更加实时、直观地体现矿井信息及三维地学信息,本文运用ArcGIS软件与SketchUp Pro软件,分别建立矿井三维地层模型,地表景观模型与工程巷道模型,最终在.NET与ArcEngine编程环境中实现原型系统集成并进行二次开发。经实践证明,本技术方案所实现的矿井模型三维可视化效果形象直观、沉浸感强,成果切实可靠。这对煤矿开采设计水平的提高及其应急管理决策支持软件的研发有一定的借鉴意义。     

粉煤灰人工湿地基质对磷吸附性能的研究

本文研究了粉煤灰作为人工湿地基质对磷的吸附动力学行为及吸附性能,并与高炉渣基质的吸附性能进行了比较。结果表明:粉煤灰具有比高炉渣更快的吸附速率及更大的吸附量,在初始磷质量浓度为10mg/L时,修正的Elovich方程在描述粉煤灰吸附动力学实验结果上显示出优越性,而Freundlich方程能更准确地拟合两种基质的等温吸附过程,并且两种基质对pH与干扰离子影响的响应均表现出相似的变化规律。因此,可以考虑用粉煤灰代替高炉渣作为人工湿地除磷基质。     

Levels and bioaccumulation of organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs) in fishes from the Pearl River estuary and Daya Bay, South China

Fifty fish samples were collected from the Pearl River estuary (PRE) and Daya Bay, South China and were analyzed for DDTs, HCHs, chlordanes and polybrominated biphenyl ethers (PBDEs). Except the high concentrations of DDT observed in fishes, the concentrations of HCHs, chlordanes and PBDEs were low when compared to other regions. BDE-47 was the predominant PBDE congener and the BDE-209 concentrations were relatively low, despite its high concentration in surface sediments. The absence of significant increase of DDT, HCH, chlordane and PBDE concentrations towards higher delta15N values, as well as the lack of a significant correlation (p<0.1) between log concentrations (lipid normalized) and delta15N, may indicate a weak biomagnification of these chemicals in the food webs. Good agreement was observed between their concentrations and lipid contents of the organisms. Bioconcentration was suggested to be responsible for the accumulation of OCPs and PBDEs in the lower trophic organisms in the studied subtropical waters.     

生草栽培对三种岭南水果种植系统的生态经济影响评价

综合运用能值、经济与土壤生态学分析方法,以传统清耕模式为对照,定量研究了生草栽培对荔枝（LitchichinensisSonn）、龙眼（DimocarpuslonganLour）和番荔枝（AnnonasquamosaLinn）三种岭南水果种植系统的生态经济影响。整合系统物质流、能量流和货币流,综合分析其自然资源基础、经济发展状况及可持续发展程度,并将土壤有机质的消耗纳入不可更新自然资源能值投入分析,为岭南水果业生草栽培与否提供科学依据。结果表明,生草栽培可以将荔枝和龙眼种植系统的能值可持续性从传统清耕模式的0．16和0．46分别提升到0．17和0．47;而使番荔枝种植系统的能值可持续性从传统清耕模式的0．59降至0．45。同时,生草栽培可提高荔枝和番荔枝种植系统的经济效益,而降低龙眼种植系统的经济效益。所有案例结果均表明,生草栽培可降低果园土壤有机质的消耗。     

Past desertification processes of Minqin Oasis in arid China

Irrigated farming has affected most natural oases in western China since the Han Dynasty employed advanced agricultural techniques in dryland areas. To date, little is documented about the process through which these oases were modified by human systems. In this study, a multi-disciplinary approach incorporating analysis of historical documents, archaeological field surveys, satellite imagery, and GIS data was used to understand desertification processes in the Minqin Basin in Gansu Province, China, over the historical period. Results suggest that initial reclamation efforts around the Minqin Oasis were launched in the Han Dynasty (220–121 BC) and culminated in the Wei and Jin Dynasty (220–420). During the following 800 years from the Southern and Northern Dynasties (420–581) to the Yuan Dynasty (1271–1368), farmland disappeared and became desert when the region was taken over by nomadic people. The second period of intense development occurred in the Ming Dynasty (1368–1644) and was followed by another more aggressive development in the Qing Dynasty (1644–1911), which resulted in the largest reclaimed area in history. Oases were constantly reclaimed and subsequently abandoned and desertified over the whole historical period. The causes were complex, but the major cause was related to dynastic transition that often resulted in changes in national policies.     

深圳市滨海湿地两个观光农业系统的能值整合研究

应用能值研究方法对深圳市海上田园旅游区的芦花湖和农家小院两个观光农业系统进行了生态经济分析.从系统和子系统两个层面,进行了能值产出、环境负载、可持续发展能力的评价与比较;与珠三角另一个观光农业系统(百万葵园)、两个基塘农业系统(菜-鱼、菜-猪-鱼)和一个巴西基塘系统(谷-猪-鱼)进行了横向比较.从货币收益的角度看,农家小院系统的费用使用效率、商品生产获利能力要优于芦花湖系统.但能值整合分析却显示出不一样的结果:两系统内旅游业子系统的能值交换率较高,而二者的农牧业子系统及农家小院系统的水产业子系统的能值交换率均较低,其生产效率仍有待提高.芦花湖系统的环境负载率为7.31,能值可持续发展指标为0.255,分别是农家小院的0.25倍和2.26倍,因而更具长远发展优势.与传统农业相比,观光农业的能值交换率和环境负载率整体偏高,表明其在经济效益创造上优于传统农业,但在自然资源利用和环境压力,以及可持续发展能力等方面与传统农业尚存在差距,在今后的发展中需借鉴传统农业的经验并加以改善,防止观光农业发展中绿色产业褐色化现象的发生.