Chemical dynamics of N-containing ionic species in a boreal forest snowcover during the spring melt period

A study of the changes in the ionic loads of NO, NH, SO and H⁺ in a boreal forest snowpack at Lake Laflamme, Québec was carried out using hydrological and chemical data from field lysimeters. The results showed that depletion of the N-containing species occurs periodically in the snowpack during meltwater discharge. Rain-on-snow events led to in-pack losses of NO and NH at a rate of 130 μeq m^?2 day^?1 and 101·3 μeq m^?2day^?1 respectively. On dry days, however, dry deposition and deposition of organic debris from the canopy resulted in increases of 183·3 μeq m^?2day^?1 for NO and 4·5 μeq m^?2day^?1 for NH in the pack. In contrast, SO₄^2? showed continual in-pack increases due to deposition of 5·0 μeq m^?2day^?1 for wet days and 92·6 μeq m^?2day^?1 for dry days. The depletion of NO and NH is due to microbiological uptake of these nutrients during periods when the free water content of the pack is high. Controlled melts in a laboratory snowmelt simulator containing snow and organic matter from the forest canopy at Lake Laflamme showed losses of NO and NH similar to those observed in the field. As the microbiological uptake proceeds at a rate comparable to that of ionic load increases in the pack by dry deposition, models of the chemical dynamics of snowmelt should take the former into account in any system where organic content of the snowpack is appreciable.     

Ab initio prediction of 29Si-NMR chemical shifts

The ability of several ab initio models to predict experimental ²⁹Si-NMR chemical shift is examined. The shielding values of trimethylsilyl chloride (A), t-butyldimethylsilyl chloride (B) and allytrimethylsilane (C) are calculated by GIAO, CSGT and IGAIM methods, using HF/6–31G^*, B3LYP/6-31G^*, HF/6–311+G^**, B3LYP/6–311+G^** and MPW1PW91/6–311+G^** models respectively. The ²⁹Si chemical shifts calculated by GIAO method using HF/6–311+G^** model are highly in agreement with those obtained experimentally. All of the models above reproduce the trends of chemical shifts in all cases studied, suggesting that the models are of practical value.     

热解—动力学光度法测定岩石和化探样品中痕量溴

以五氧化二钒为熔剂,用热解分离富集痕量溴,吸收于0.036mol/l 氢氧化钾中,在1.34mol/l 硫酸和硝酸混合溶液中,溴离子催化高锰酸钾对碘的氧化,用苯萃取未反应碘,然后用硫氢酸汞—硫酸高铁铵比色法测定溴。本方法灵敏度高,远择性好,操作简便、快速,方法检出限为0.35ppm 溴,标准偏差为11.63％。     

庐山羊角岭红色泥砾泥石流成因质疑——与施雅风、邓养鑫商榷

作者根据庐山羊角岭红色泥砾的岩性特征,从地形和堆积物的宏观和微观特征进行分析研究,得出庐山有第四纪冰川。     

Assessing surface water quality of the Yangtze Estuary with genotoxicity data

The present study investigated the genotoxicity of the surface water samples from the Yangtze Estuary with the Ames test in three seasons. Several important chemical parameters, such as COD inorganic nitrogen, active phosphate and heavy metals, were also analyzed at the same time. According the results, surface water samples from the south branch and a few of samples at the seaward end of the Yangtze Estuary show positive genotoxicity in some seasons. Chemical analysis revealed that the Yangtze Estuary was seriously polluted by inorganic nitrogen and by active phosphate. However, chemical parameters could not demonstrate the spatial variation of water quality of the estuary, and they could not assess adverse effects of chemicals in mixtures as well. Therefore, it is recommended that genotoxicity data, mutation rate of the Salmonella typhimurium strain TA98 at the dose of 1 l per plate, be taken as a new parameter assessing surface water quality of the Yangtze Estuary. Our studies also suggested that genetic toxicology assays, such as the Ames test, could be applied as a routine measure to monitoring marine environment in China. The paper proposes a development of the National Seawater Quality Standard of China.     

脱硝技术与天然气应用情景下京津冀地区空气质量模拟评估

针对京津冀地区主要大气污染物NOx（氮氧化物）和PM2.5（大气中粒径小于或等于2.5μm的颗粒物）,应用柴油车尾气净化技术及中小锅炉烟气脱硝技术,并根据2015年和2030年我国能源规划,设计3种技术应用情景,采用WRF-CAMx耦合模式,对京津冀地区大气中NOx和PM2.5进行了应用情景模拟。结果表明,单独应用柴油车尾气净化技术后（方案1）,北京、天津地区大气中的NOx浓度降低幅度达20%,河北地区降低5%;PM2.5的浓度降低幅度约10%;应用柴油车尾气净化技术和2015年能源规划情景（方案2）,京津冀地区大气中NOx和PM2.5浓度的降低幅度均超过20%;应用柴油车尾气净化技术和2030年能源规划情景（方案3）,该地区NOx浓度降低幅度与之相当,PM2.5浓度降低幅度超过30%。可见脱硝技术和清洁能源利用的有效性依赖于其应用比例。二次气粒转化的化学过程形成的硝酸盐、硫酸盐和铵盐对该地区空气中PM2.5浓度的贡献很大,冬、春、秋季硝酸盐最大贡献高达60%,夏、秋季硫酸盐最大贡献超过70%,铵盐四季最大贡献约25%。这说明PM2.5的主要前体物NOx、SO2、NH3、VOCs (Volatile Organic Compounds)、CO等均大幅度削减才能有效降低该地区空气中PM2.5浓度。     

Aerosol characteristics during winter fog at Agra,North India

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-.     

Compositions and source apportionments of atmospheric aerosol during Asian dust storm and local pollution in central Taiwan

A study has been carried out on water soluble ions, trace elements, as well as PM_2.5 and PM_2.5–10 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 PM_2.5 and PM_2.5–10 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 PM_2.5 during LOP periods. However, sea salt species (Na⁺ and Cl⁻) and crustal elements (e.g., Al, Fe, Mg, K, Ca and Ti) of PM_2.5–10 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 PM_2.5–10 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 PM_2.5–10 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 PM_2.5, 50% of PM_2.5–10, 42% of sulfate and 30% of nitrate were attributable to the long range transport during ADS periods, respectively.     

Geotechnical and geological properties of Mokattam limestones: Implications for conservation strategies for ancient Egyptian stone monuments

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.