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71.
P. D. Safai S. Kewat G. Pandithurai P. S. Praveen K. Ali S. Tiwari P. S. P. Rao K. B. Budhawant S. K. Saha P. C. S. Devara 《Journal of Atmospheric Chemistry》2008,61(2):101-118
Simultaneous measurements on physical, chemical and optical properties of aerosols over a tropical semi-arid location, Agra
in north India, were undertaken during December 2004. The average concentration of total suspended particulates (TSP) increased
by about 1.4 times during intense foggy/hazy days. Concentrations of SO4
2−, NO3
−, NH4
+ and Black Carbon (BC) aerosols increased by 4, 2, 3.5 and 1.7 times, respectively during that period. Aerosols were acidic
during intense foggy/hazy days but the fog water showed alkaline nature, mainly due to the neutralizing capacity of NH4 aerosols. Trajectory analyses showed that air masses were predominantly from NW direction, which might be responsible for
transport of BC from distant and surrounding local sources. Diurnal variation of BC on all days showed a morning and an evening
peak that were related to domestic cooking and vehicular emissions, apart from boundary layer changes. OPAC (Optical properties
of aerosols and clouds) model was used to compute the optical properties of aerosols. Both OPAC-derived and observed aerosol
optical depth (AOD) values showed spectral variation with high loadings in the short wavelengths (<1 μm). AOD value at 0.5 μm
wavelength was significantly high during intense foggy/hazy days (1.22) than during clear sky or less foggy/hazy days (0.63).
OPAC-derived Single scattering albedo (SSA) was 0.84 during the observational period, indicating significant contribution
of absorbing aerosols. However, the BC mass fraction to TSP increased by only 1% during intense foggy/hazy days and thereby
did not show any impact on SSA during that period. A large increase was observed in the shortwave (SW) atmospheric (ATM) forcing
during intense foggy/hazy days (+75.8 W/m2) than that during clear sky or less foggy/hazy days (+38 W/m2), mainly due to increase in absorbing aerosols. Whereas SW forcing at surface (SUF) increased from −40 W/m2 during clear sky or less foggy/hazy days to −76 W/m2 during intense foggy/hazy days, mainly due to the scattering aerosols like SO4
2-. 相似文献
72.
Man-Ting Cheng Wei-Chun Chou Chia-Pin Chio Shih-Chieh Hsu Yi-Ru Su Pei-Hsuan Kuo Ben-Jei Tsuang Shuen-Hsin Lin Charles C.-K. Chou 《Journal of Atmospheric Chemistry》2008,61(2):155-173
A study has been carried out on water soluble ions, trace elements, as well as PM2.5 and PM2.5–10 elemental and organic carbon samples collected daily from Central Taiwan over a one year period in 2005. A source apportionment
study was performed, employing a Gaussian trajectory transfer coefficient model (GTx) to the results from 141 sets of PM2.5 and PM2.5–10 samples. Two different types of PM10 episodes, local pollution (LOP) and Asian dust storm (ADS) were observed in this study. The results revealed that relative
high concentrations of secondary aerosols (NO3−, SO42− and NH4+) and the elements Cu, Zn, Cd, Pb and As were observed in PM2.5 during LOP periods. However, sea salt species (Na+ and Cl−) and crustal elements (e.g., Al, Fe, Mg, K, Ca and Ti) of PM2.5–10 showed a sharp increase during ADS periods. Anthropogenic source metals, Cu, Zn, Cd, Pb and As, as well as coarse nitrate
also increased with ADS episodes. Moreover, reconstruction of aerosol compositions revealed that soil of PM2.5–10 elevated approximately 12–14% in ADS periods than LOP and Clear periods. A significantly high ratio of non-sea salt sulfate
to elemental carbon (NSS-SO42−/EC) of PM2.5–10 during ADS periods was associated with higher concentrations of non-sea-salt sulfates from the industrial regions of China.
Source apportionment analysis showed that 39% of PM10, 25% of PM2.5, 50% of PM2.5–10, 42% of sulfate and 30% of nitrate were attributable to the long range transport during ADS periods, respectively. 相似文献
73.
Geotechnical and geological properties of limestone samples from the Mokattam Quarry in Cairo, Egypt, were determined in order to provide prior information for the selection of suitable methods for the conservation of stone monuments around Cairo. A commercial chemical consolidant (Wacker OH 100) was applied to fill the pore spaces and to strengthen the weathered rock. Filling of pore spaces was confirmed by the decrease of both porosity and permeability of rock samples after the application of the consolidant. Analysis by mercury porosimeter showed most effective consolidation results for pore spaces from 0.75 to 1.0 µm in diameter, which were those mainly observed in the samples. Ultrasonic velocity did not show any significant evidence but an increase in strength, observed as an increase in the point load index after the consolidation process was completed, confirmed that the filling and consolidation process worked effectively. Point load testing can thus be used in preference when the number of samples available for laboratory testing is limited. From the color analysis, it was shown that there was no noticeable color change after the application of consolidant Wacker OH 100. The combinations of laboratory tests adopted in this study can be applicable to the planning of conservation of other stone monuments. 相似文献
74.
Prognosis of TiO2 abundance in lunar soil using a non-linear analysis of Clementine and LSCC data 总被引:1,自引:0,他引:1
Viktor V. Korokhin Vadym G. Kaydash Dmitry G. Stankevich 《Planetary and Space Science》2008,56(8):1063-1078
We suggest a technique to determine the chemical and mineral composition of the lunar surface using artificial neural networks (ANNs). We demonstrate this powerful non-linear approach for prognosis of TiO2 abundance using Clementine UV-VIS mosaics and Lunar Soil Characterization Consortium data. The ANN technique allows one to study correlations between spectral characteristics of lunar soils and composition parameters without any restrictions on the character of these correlations. The advantage of this method in comparison with the traditional linear regression method and the Lucey et al. approaches is shown. The results obtained could be useful for the strategy of analyzing lunar data that will be acquired in incoming lunar missions especially in case of the Chandrayaan-1 and Lunar Reconnaissance Orbiter missions. 相似文献
75.
76.
【目的】通过化学诱导方法从一株海洋真菌Hypocrea lixii中获得多样化的活性小分子化合物。【方法】对菌株在盐酸普鲁卡因的化学诱导作用下进行固体发酵,代谢产物采用硅胶减压柱层析、Sephadex LH-20以及pHPLC等手段分离纯化,对化合物运用NMR、MS等波谱学技术并比对文献进行结构鉴定,采用Ellman比色法及DPPH自由基清除法对化合物进行初步抗乙酰胆碱酯酶(AChE)和抗氧化活性测试。【结果】从海洋真菌Hypocrea lixii在盐酸普鲁卡因诱导下的发酵提取物中分离得到4个异黄酮类化合物,包括6'-O-crotonylgenistin(1)、Genistein(2)、Daidzein(3)和Genistin(4),以及对氨基苯甲酸甲酯(5)、对羟基苯丙酸(6)和胞嘧啶(7),其中化合物1和6为该种中首次报道,化合物5为生物转化来源首次报道,化合物2~4可能源自培养基。在100μmol/L剂量浓度下,化合物1~4对AChE的抑制以及DPPH自由基的清除活性均较弱,化合物5和6显示了相对强的AChE抑制活性,抑制率分别为40%和38%。【结论】盐酸普鲁卡因对该菌次级代谢产生了显著的影响,为深入研究该菌株化学诱导次级代谢产物提供基础。 相似文献
77.
化肥是提高作物产量的物质基础, 在过去的几十年中, 它在世界农业建设中起过巨大作用。近百年的肥料试验表明, 化学肥料具有和有机质一样的持续增产效果, 在提高作物产量、品质的同时, 还可培肥土壤。随着化肥工业的发展, 化肥的负作用会逐渐减小。 相似文献
78.
79.
Shin Giek Goh Stéphane Bayen David Burger Barry C. Kelly Ping Han Vladan Babovic Karina Yew-Hoong Gin 《Marine pollution bulletin》2017,114(1):627-634
Water quality in Singapore's coastal area was evaluated with microbial indicators, pathogenic vibrios, chemical tracers and physico-chemical parameters. Sampling sites were grouped into two clusters (coastal sites at (i) northern and (ii) southern part of Singapore). The coastal sites located at northern part of Singapore along the Johor Straits exhibited greater pollution. Principal component analysis revealed that sampling sites at Johor Straits have greater loading on carbamazepine, while turbidity poses greater influence on sampling sites at Singapore Straits. Detection of pathogenic vibrios was also more prominent at Johor Straits than the Singapore Straits. This study examined the spatial variations in Singapore's coastal water quality and provided the baseline information for health risk assessment and future pollution management. 相似文献
80.
U. Irmer 《洁净——土壤、空气、水》2000,28(1):7-14
The New EC Framework Water Directive: Assessment of the Chemical and Ecological Status of Surface Waters The main objective of the draft EC Framework Water Directive is the good quality of all surface waters. The directive provides for an assessment of the chemical status of surface waters (EU‐wide valid environmental quality standards for approximately 30 priority substances) and a five‐stage ecological classification of waters, comprising the stages high, good, moderate, poor, and bad. The starting point for the assessment are the reference conditions, which are defined as corresponding to high water quality and characterising a water status with no significant anthropogenic impact. The reference sites in the various water body types are to be selected using hydromorphological and physico‐chemical parameters and subsequently characterised by means of biological parameters. For surface waters, three groups of characteristics are provided for, namely: 1. with priority the biology – in the case of surface waters – with the four elements phytoplankton, macrophytes/phytobenthos, benthic invertebrate fauna, and fish fauna; 2. supporting the hydromorphology, e.g. flowing waters with the three elements hydrological regime, river continuity, and morphological conditions and 3. supporting the physico‐chemical conditions with the three elements general conditions, specific synthetic pollutants, and specific non synthetic pollutants (other than the priority substances of the chemical status). 相似文献