大型渡槽结构动力学研究进展

大型渡槽是灌区生命线工程中的关键性建筑物,其在地震及风载作用下的安全性已是渡槽建设的瓶劲,也是国内外研究的热点。渡槽结构的抗震、减震和抗风技术的核心是渡槽结构动力学的问题,而渡槽结构动力学系属流固耦合(FSI)系统的动力学范畴。在已有研究的基础上,首先对渡槽结构FSI系统模型的研究进行了总结和评述;然后简述了渡槽结构动力特性和响应的求解技术以及抗震、隔震、减震与抗风技术的研究概况;最后总结了渡槽结构动力学的研究进展,提出了该学科进一步研究的内容和方法。     

Tsunami survivors' perspectives on vulnerability and vulnerability reduction: evidence from Koh Phi Phi Don and Khao Lak, Thailand

This paper presents the results of primary research with 40 survivors of the 2004 Indian Ocean tsunami in two communities: Khao Lak (n=20) and Koh Phi Phi Don (n=20), Thailand. It traces tsunami survivors' perceptions of vulnerability, determines whether residents felt that the tsunami affected different communities differently, identifies the populations and sub-community groups that survivors distinguished as being more vulnerable than others, highlights community-generated ideas about vulnerability reduction, and pinpoints a range of additional vulnerability reduction actions. Tsunami survivors most consistently identified the 'most vulnerable' community sub-populations as women, children, the elderly, foreigners, and the poor. In Khao Lak, however, respondents added 'Burmese migrants' to this list, whereas in Koh Phi Phi Don, they added 'Thai Muslims'. Results suggest that the two case study communities, both small, coastal, tourism-dominated communities no more than 100 kilometres apart, have differing vulnerable sub-groups and environmental vulnerabilities, requiring different post-disaster vulnerability reduction efforts.     

Diazinon Fate and Toxicity in the Tajan River (Iran) Ecosystem

Abstract This study surveyed the behavior of diazinon pesticide in the water column of the Tajan River and its potential effects on river biota. The Tajan River is located on the southern basin of the Caspian Sea in Iran and diazinon enters the river from rice fields almost every year between the months of June and October. The sampling plan of flowing water was plotted in a 3-week period on five sites along the river and also at the end of tributaries. Samples were collected seven times during a 6-month period; they were analyzed for diazinon residues and some physicochemical characteristics. Total diazinon concentration range was between 0.01 and 46.99?μg/L in sampling stations. The calibrated AQUATOX model was applied to simulate fate processes and ecotoxicity of diazinon in the Tajan River. The model demonstrated that the diazinon residues in the Tajan River reacted to three major degradation processes (microbial, hydrolysis, and photolysis) and sedimentation; however, the river discharge played the m...     

中国水泥行业通过CCUS技术的减排潜力评估

中国水泥行业面临巨大的碳达峰与碳中和压力.CO₂捕集利用与封存（CCUS）技术是能够实现化石资源低碳利用的碳减排技术.在中国水泥企业数据基础上,采用全流程CCUS系统模型（ITEAM-CCUS）评估CCUS的碳减排潜力对水泥企业碳中和非常重要.模型从源汇匹配距离、捕集率、CCUS技术和技术水平这4个方面设置了10种情景,完成了水泥行业的企业筛选、场地筛选、CCUS技术经济评估和源汇匹配,初步回答了水泥企业结合CCUS的封存场地、减排规模、成本范围和优先项目分布等关键问题.在250 km匹配距离、85%净捕集率、CO₂-EWR技术和当前技术水平情景,44%的水泥企业可以利用CO₂强化地下水开采（CO₂-EWR）技术开展碳减排,累计年碳减排量为6.25亿t,平准化成本为290~1838元·t^-1;具有全流程CO₂-EWR早期示范优势的地区为新疆、内蒙古、宁夏、河南和河北等.水泥企业开展全流程CCUS项目技术可行,可以实现大规模CO₂减排,低成本项目具有早期示范机会.研究结果可为水泥行业低碳发展和CCUS商业化部署提供定量参考.     

Promotional catalytic activity and reaction mechanism of Ag-modified Ce0.6Zr0.4O2 catalyst for catalytic oxidation of ammonia

Ce_1-xZr_xO₂ composite oxides (molar, x = 0-1.0, interval of 0.2) were prepared by a cetyltrimethylammonium bromide-assisted precipitation method. The enhancement of silver-species modification and catalytic mechanism of adsorption-transformation-desorption process were investigated over the Ag-impregnated catalysts for low-temperature selective catalytic oxidation of ammonia (NH₃-SCO). The optimal 5 wt.% Ag/Ce_0.6Zr_0.4O₂ catalyst presented good NH₃-SCO performance with >90% NH₃ conversion at temperature (T) ≥ 250°C and 89% N₂ selectivity. Despite the irregular block shape and underdeveloped specific surface area (∼60 m²/g), the naked and Ag-modified Ce_0.6Zr_0.4O₂ solid solution still obtained highly dispersed distribution of surface elements analyzed by scanning electron microscope-energy dispersive spectrometer (SEM-EDS) (mapping), N₂ adsorption-desorption test and X-ray diffraction (XRD). H₂ temperature programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS) results indicated that Ag-modification enhanced the mobility and activation of oxygen-species leading to a promotion on CeO₂ reducibility and synergistic Ag⁰/Ag⁺ and Ce⁴⁺/Ce³⁺ redox cycles. Besides, Ag⁺/Ag₂O clusters could facilitate the formation of surface oxygen vacancies that was beneficial to the adsorption and activation of ammonia. NH₃-temperature programmed desorption (NH₃-TPD) showed more adsorption-desorption capacity to ammonia were provided by physical, weak- and medium-strong acid sites. Diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments revealed the activation of ammonia might be the control step of NH₃-SCO procedure, during which NH₃ dehydrogenation derived from NH_x-species and also internal selective catalytic reduction (i-SCR) reactions were proposed.     

A review of gas-phase chemical mechanisms commonly used in atmospheric chemistry modelling

The atmospheric chemical mechanism is an essential component of airshed models used for investigating the chemical behaviors and impacts of species. Since the first tropospheric chemical mechanism was proposed in the 1960s, various mechanisms including Master Chemical Mechanism (MCM), Carbon Bond Mechanism (CBM), Statewide Air Pollution Research Center (SAPRC) and Regional Atmospheric Chemistry Mechanism (RACM) have been developed for different research purposes. This work summarizes the development and applications of these mechanisms, introduces their compositions and lumping methods, and compares the ways the mechanisms treat radicals with box model simulations. CBM can reproduce urban pollution events with relatively low cost compared to SAPRC and RACM, whereas the chemical behaviors of radicals and the photochemical production of ozone are described in detail in RACM. The photolysis rates of some oxygenated compounds are low in SAPRC07, which may result in underestimation of radical levels. As an explicit chemical mechanism, MCM describes the chemical processes of primary pollutants and their oxidation products in detail. MCM can be used to investigate certain chemical processes; however, due to its large size, it is rarely used in regional model simulations. A box model case study showed that the chemical behavior of OH and HO₂ radicals and the production of ozone were well described by all mechanisms. CBM and SAPRC underestimated the radical levels for different chemical treatments, leading to low ozone production values in both cases. MCM and RACM are widely used in box model studies, while CBM and SAPRC are often selected in regional simulations.     

南京北郊PM2.5中有机组分的吸光性质及来源

对南京北郊2018年9月~2019年9月PM_2.5中有机组分的吸光性质进行了研究,并利用PM_2.5化学组成及主成分分析法分析该地区吸光性有机碳（棕碳,brown carbon,BrC）的主要来源.结果表明,水溶性有机碳（water-soluble organic carbon,WSOC）和甲醇可提取有机碳（methanol extractable organic carbon,MEOC）在365 nm处光吸收系数（Abs_365,w和Abs_365,m）的平均值分别为（3.22±2.18）Mm^-1和（7.69±4.93）Mm^-1.Abs_365,w和Abs_365,m分别与WSOC（r=0.72,P<0.01）和MEOC（r=0.62,P=0.04）的质量浓度显著相关,均表现为冬高夏低,夜高昼低的时间变化特征.这可归结于冬季和夜间的气象特征（例如边界层高度降低和大气稳定度升高）、冬季一次源排放的增加以及夏季和白天更强的"光漂白作用".Abs_365,m/Abs_365,w的年均值（2.60±0.92）远高于MEOC/WSOC（质量浓度比值,1.37±0.30）,表明MEOC中非水溶性组分的吸光作用更强,在BrC的吸光作用中占主导地位.WSOC、MEOC、Abs_365,m和K⁺均未表现出强相关性（r<0.60）,因此生物质燃烧不是该地区BrC的主要一次来源.WSOC和MEOC质量吸收效率（MAE_365,w和MAE_365,m）及其比值（MAE_365,m/MAE_365,w）的季节变化和Abs₃₆₅相同.MEOC中非水溶性组分的MAE₃₆₅［（4.10±5.15）m²·g^-1］分别是MAE_365,w和MAE_365,m的6.0和2.9倍,支持BrC的吸光作用受非水溶性有机组分主导这一推断.和WSOC的埃氏吸收指数（Å_WSOC）相比,MEOC的埃氏吸收指数（Å_MEOC）随时间变化更显著,这可能与非水溶性吸光组分排放的季节变化有关.主成分分析结果显示,本研究PM_2.5中有机组分的吸光作用主要来源于二次形成过程和人为活动相关的一次排放,而不是生物质燃烧.     

喀斯特地区小尺度农业土壤砷的空间分布及污染评价

贵州岩溶地貌分布广泛,部分地区的土壤砷(As)污染问题比较突出.为了解高As背景地区农业土壤As含量分布特征,选取贵州省兴义市西南部具有代表性的As污染区(典型喀斯特区、亚喀斯特区)为研究对象,并以非喀斯特区作为对照组,采用地统计分析与GIS相结合的方法研究农业土壤As的空间变异和污染状况,并采用Moran's I系数分析在小尺度下土壤As的空间自相关性及其方向性特征.结果表明,不同地貌区土壤中As含量从高到低依次为:典型喀斯特区亚喀斯特区非喀斯特区,其中典型喀斯特区农业土壤As的算术均值与几何均值分别为47. 9 mg·kg~(-1)和43. 3 mg·kg~(-1),亚喀斯特区其值分别为36. 8 mg·kg~(-1)和30. 1 mg·kg~(-1),两个区域农业土壤As含量明显高于贵州土壤As背景值,As的超标率分别为98. 5%和96. 7%,表现出明显的As累积,而非喀斯特区As超标率仅为6. 7%;独立样本T检验结果表明,在3个不同地貌类型中,农业土壤与自然土壤As含量均无显著性差异(P 0. 05).农业土壤As的Moran's I系数为0. 45,Z值为11. 61,在本采样尺度下具有显著的正空间自相关(P 0. 05),存在空间聚集,尤其是东北-西南方向空间自相关性较好,以结构性变异为主.农业土壤样本As总体上处于轻微污染至轻度污染之间,分别占27. 10%、29. 02%,部分地区处于中度污染级别,而处于无污染状态的样本占41. 94%.     

农用地土壤抗生素组成特征与积累规律

选取我国北部典型农副产品生产基地,利用HPLC-MS/MS测定土样中四环素类（tetracycline antibiotics,TCs）、大环内脂类（macrolide antibiotics,MLs）以及磺胺类（sulfonamide antibiotics,SAs）共10种抗生素的残留含量,研究不同种类抗生素的组成及空间分布,并对其分布特征与距养殖场、公路、河流间距离的关系,以及不同种植模式、不同土壤性质对抗生素组成与积累规律的影响进行初步探讨.结果表明,研究区土壤抗生素含量值处于较低水平,但检出率较高,总量的检出率高达100%.研究区土壤抗生素的主要成分为TCs,约占总量的94%,不同抗生素的变异系数较大.区内土壤抗生素的空间分布及积累规律受人类活动强度的影响,其中抗生素含量与距养殖场距离呈显著负相关（P<0.05）;距河流50 m内的样点3类抗生素的检出率均达100%;不同种植模式下抗生素含量的积累规律为：果园 > 菜地 > 菜果混种地,且桃园及露天菜地中抗生素的来源、含量与核桃园、大棚菜地及菜果混种地块有明显区别.研究选用土壤pH、有机质（SOM）,阳离子交换量（CEC）、总氮（TN）、有效磷（AP）、速效钾（AK）表征土壤性质,通过冗余分析显示,土壤pH、SOM、CEC、AP、AK这5种土壤特性对抗生素含量的影响较大,其中AK的影响强度最大,TN的影响则相对较弱.研究认为区内土壤抗生素的组成与积累程度受人类活动及土壤性质的共同作用.     

金盆水库沉积物磷的来源及分布特征

为探究分层型水源水库沉积物中磷的来源与分布特征,以西安金盆水库为对象,针对2017年3～11月金盆水库水体、沉降颗粒及沉积物柱状样品总磷(TP)含量及形态分布特征进行研究.结果表明,金盆水库主库区表层沉积物总磷含量及形态分布受水体颗粒磷(PP)沉降作用明显,相关系数r~2=0. 877 5;同时表层沉积物总磷含量还受到沉积物内部生物地球化学的共同作用. 6～8月金盆水库水体藻类剧烈繁殖演替,繁殖过程中大量失去活性、死亡的藻类不断向底部水体沉积,形成以藻类等颗粒磷为主导的内源污染,沉降颗粒总磷含量达(753. 51±17. 11) mg·kg~(-1),表层沉积物总磷含量随之增加,以铁铝结合态非活性磷(NaOH-nrP)为主; 9～11月进入汛期,径流水体携带大量泥沙等负荷较大的污染物汇入水库,使得水体颗粒磷浓度相应增大,然而由于单位质量泥沙中总磷含量占比较小,导致径流过程中表层沉积物总磷含量逐渐降低,泥沙径流过程中颗粒磷以无机态的钙磷(Ca-P)和残渣态磷(rest-P)为主,二者约占沉积物总磷(TP) 55. 8%～66. 2%,受颗粒沉降影响相对较大.活性磷(SRP)、铁锰螯合态磷(BD-P)和铁铝结合态活性磷(NaOH-srP)这3种形态磷较活跃,在环境条件的变化(主要是氧化还原条件)下发生一系列迁移转化,受沉积物内部生物地球生物化学过程作用明显.