阳光紫外辐射对绿藻石莼光化学效率的影响

探讨太阳紫外辐射(UVR)对大型海藻的影响,选择常见的海藻石莼(Ulva lactuca)为实验材料,研究了其光化学效率与UVR的关系.实验结果表明,石莼光化学效率在较强太阳辐射下急剧下降,在下午光强变弱时开始恢复,显示了一个明显的日变化模式:早上和下午保持较高的水平,中午降为最低.其光化学效率的日变动,与可见光和UVR均有关系,在中午高太阳辐射下,UV-B对藻体光化学效率的影响较大.长期实验结果显示,UVR对石莼光化学效率的影响,在实验的第二天表现为最大,随之逐渐减弱.本实验的研究结果可为研究阳光紫外线对大型海藻生长和生理的影响提供一定参考.     

20世纪云南地区地震记录完全性评价

通过对1901～2000年云南地区5级以上地震记录完全性分析,发现20世纪早期云南地震漏载仍然严重,30年代以后5级以上地震记录较为完全,其中滇西南为地震记录的主要漏载地区。根据b值估算得到20世纪云南地区漏载5级地震143次、6级地震6.6次,这是地震活动性研究需要考虑的重要因素。60年代后地震活动的起伏与地震监控能力无关。     

20 世纪美国城市体系的演变及其对中国的启示

在快速城市化过程中,在规模不等的城市中城市人口将如何分布？这是制订中国社会经济发展战略必须考虑的一个重大基础问题。美国是世界上最大的发达经济体,城市体系成熟,100 年前的城市化水平和中国现在相当。研究20 世纪美国城市体系的演化特征,对中国会有所启发。采用美国人口普查数据,运用位序-规模法则等方法,分析了美国城市系统的演变过程。结果显示：在20 世纪前70 年美国城市化处于加速发展的中期阶段,大城市的人口增长明显快于中小城市,城市体系向非均衡化方向发展;20 世纪后30 年,美国城市化进入了稳定发展的后期阶段。与美国不同的是,处于城市化加速发展中期阶段的中国(1985-2000 年),小城市人口增长较快,城市体系趋于均衡。研究认为：未来我国大城市的人口集聚有较大潜力。     

紫外光照下锐钛型Fe-TiO2粉末对甲基蓝的催化降解

采用水热法自制的锐钛型Fe-Ti O2粉末在紫外光(λ=254 nm)照射下,对有机污染物甲基蓝进行光催化降解,研究了甲基蓝溶液的初始浓度、溶液的p H、Ti O2掺杂量、Ti O2用量、反应时间等因素对甲基蓝降解率的影响。结果表明:在甲基蓝溶液初始浓度为50 mg/L(p H=6)、Ti O2掺铁量3%(摩尔分数)、Ti O2粉末用量为1.00 g/L、室温18℃下经紫外光照射反应105 min,甲基蓝的降解率达到97.3%。     

Spectrophotometric Determination of Gold (III) after Liquid–Liquid Extraction and Selective Pre‐concentration with a Novel Dibenzo‐18‐Crown‐6 Derivative

A selective and sensitive method for the extraction and spectrophotometric determination of gold with N,N′‐6,7,9,10,17,18,20,21‐octahydrodibenzo[b,k][1,4,7,10,13,16] hexaoxacyclo‐octadecine‐2,13–diylbis(2‐chloroacetamide) (ODBOCA) is described. The ODBOCA–Au(III) complex was extracted from a slightly acidic aqueous solution (pH 5) into a chloroform layer and then the absorbance of the extract was measured using a UV–Vis spectrophotometer with 1.0 cm quartz cells at 540 nm. An enrichment factor of 200 was achieved. In the chloroform medium at 540 nm, the molar absorptivity and Sandell’s sensitivity were 4.12 × 10³ l mol^?1 cm^?1 and 0.048 μg cm^?2, respectively. Beer’s law was obeyed in the range of 0.5–15 μg ml^?1 in the measured solution. The relative standard deviation for ten replicate samples at the 1.0 μg ml^?1 level was 3.0%. The limit of detection, based on 3s, was 0.5 μg l^?1 in the original sample. The effects of pH, ligand concentration and shaking time were studied. The ratio of the metal ion to ligand molecules in the complex was found to be 1:2 according to the Job Method. The effects of interference by a number of metal ions were investigated. The method was verified with certified reference materials and spiked tests, and quantitative recovery values were obtained. The method was fast, accurate, selective and precise, and was applied to the determination of gold in water and ore with good results.     

Climate change analysis on historical watershed‐scale precipitation by means of long‐term dynamical downscaling

A methodology based on long‐term dynamical downscaling to analyse climate change effects on watershed‐scale precipitation during a historical period is proposed in this study. The reliability and applicability of the methodology were investigated based on the long‐term dynamical downscaling results. For an application of the proposed methodology, two study watersheds in Northern California were selected: the Upper Feather River watershed and the Yuba River watershed. Then, precipitation was reconstructed at 3‐km spatial resolution and hourly intervals over the study watersheds for 141 water years from 1 October 1871 to 30 September 2012 by dynamically downscaling a long‐term atmospheric reanalysis dataset, 20th century global reanalysis version 2 by means of a regional climate model. The reconstructed precipitation was compared against observed precipitation, in order to assess the applicability of the proposed methodology for the reconstruction of watershed‐scale precipitation and to validate this methodology. The validation shows that the reconstructed precipitation is in good agreement with observation data. Moreover, the differences between the reconstructed precipitation and the corresponding observations do not significantly change through the historical period. After the validation, climate change analysis was conducted based on the reconstructed precipitation. Through this analysis, it was found that basin‐average precipitation has increased significantly over both of the study watersheds during the historical period. An upward trend in monthly basin‐average precipitation is not significant in wet months except February while it is significant in dry months of the year. Furthermore, peak values of basin‐average precipitation are also on an upward trend over the study watersheds. The upward trend in peak basin‐average precipitation is more significant during a shorter duration. Copyright © 2016 John Wiley & Sons, Ltd.     

Two types of dynamic cool coronal structures observed with STEREO and Hirtode

Solar coronal loops show significant plasma motions during their formation and eruption stages. Dynamic cool coronal structures, on the other hand, are often observed to propagate along coronal loops. We report on the discovery of two types of dynamic cool coronal structures, and characterize their fundamental properties. Using the EUV 304 A images from the Extreme UltraViolet Imager （EUVI） telescope on the Solar TErrestrial RElation Observatory （STEREO） and the Ca Ⅱ filtergrams from the Solar Optical Telescope （SOT） instrument on Hinode, we study the evolution of an EUV arch and the kinematics of cool coronal structures. The EUV 304A observations show that a missile-like plasmoid moves along an arch-shaped trajectory, with an average velocity of 31 km s^- 1. About three hours later, a plasma arch forms along the trajectory, subsequently the top part of the arch fades away and disappears; meanwhile the plasma belonging to the two legs of the arch flows downward to the arch＇s feet. During the arch formation and disappearance, SOT Ca Ⅱ images explore dynamic cool coronal structures beneath the arch. By tracking these structures, we classify them into two types. Type I is thread- like in shape and flows downward with a greater average velocity of 72 km s-l; finally it combines with a loop fibril at a chromospheric altitude. Type Ⅱ is shape-transformable and sometimes rolling as it flows downward with a smaller velocity of 37 km s-1, then disappears insularly in the chromosphere. It is suggested that the two types of structures are possibly controlled by different magnetic configurations.     

Microphysical, chemical and optical aerosol properties in the Baltic Sea region

The microphysical structure, chemical composition and prehistory of aerosol are related to the aerosol optical properties and radiative effect in the UV spectral range. The aim of this work is the statistical mapping of typical aerosol scenarios and adjustment of regional aerosol parameters. The investigation is based on the in situ measurements in Preila (55.55° N, 21.00° E), Lithuania, and the AERONET data from the Gustav Dalen Tower (58 N, 17 E), Sweden.Clustering of multiple characteristics enabled to distinguish three aerosol types for clear-sky periods: 1) clean maritime–continental aerosol; 2) moderately polluted maritime–continental aerosol; 3) polluted continental aerosol. Differences between these types are due to significant differences in aerosol number and volume concentration, effective radius of volume distribution, content of SO₄⁻ ions and Black Carbon, as well as different vertical profiles of atmospheric relative humidity. The UV extinction, aerosol optical depth (AOD) and the Ångstrom coefficient α increased with the increasing pollution. The value α = 1.96 was observed in the polluted continental aerosol that has passed over central and eastern Europe and southern Russia. Reduction of the clear-sky UV index against the aerosol-free atmosphere was of 4.5%, 27% and 41% for the aerosol types 1, 2 and 3, respectively.