Aerosol concentrations observed at Mt. Haruna,Japan, in relation to long-range transport of Asian mineral dust aerosols

As a part of the effort to understand the structure of long-range transported aerosol plumes and local pollution, aerosol observations monitored the mass concentrations and number-size distributions during the period August 2006 to July 2009 near the top of Mt. Haruna (1365 m), an isolated mountain in the Kanto Plain in Japan. The mass concentrations observed at Mt. Haruna and plain sites showed a seasonal variation with a maximum in spring and summer, respectively. The spring peaks in aerosols at Mt. Haruna were probably caused by long-range transport of mineral dust and anthropogenic particles from the Asian continent. The summer peaks at the plain sites was attributed to local pollution from the Tokyo metropolitan area. Three examples of 2007 Asian dust events were investigated to show that aerosols may be dispersed in a complicated three-dimensional structure and that delayed arrivals of the dust plumes at plain sites compared to Mt. Haruna were not a rare case. Because of the boundary layer being stable at night, the dust layer was advected eastward without the vertical mixing before sunrise. This study suggests that after thermal convection activated by sunlight during daytime Asian dust transported in the free troposphere may be brought down into the atmospheric boundary layer, increasing the dust concentration there.     

Experiments and numerical simulation on methane flame quenching by water mist

The study of extinguishment using water mist has been motivated due to the phase-out of the use of halens and the search for alternative means that preserve all of the benefits of a clean total flooding agent without adverse environmental impact. With the numerical simulation, we analyzed a gas–liquid two-phase problem including water (liquid), air and methane (gas) using Eulerian equations for the liquid phase and the full Navier–Stokes equations for the gas phase. Gaseous mass, momentum and energy equations are integrated simultaneously by a Harten–Yee explicit non-MUSCL modified-flux type TVD scheme for the convective terms and a central difference scheme for the viscous terms. Liquid phase conservation equations are solved with an application of a flux-vector-splitting scheme. In the experiments in an open room (500×500×500 mm) we observed an interaction of the diffusion flame with the water mists. The results show remarkable flame quenching and a good agreement between the numerical and experimental results.     

Estimation method to identify scalar point source in turbulent flow based on Taylor’s diffusion theory

We introduce a new approach to diffusion-source estimation for quick identification of the unknown source, based on Taylor’s diffusion theory for turbulent transport of passive scalar from a fixed point source. In order to evaluate the method, we used planar laser-induced fluorescence to measure the concentration field of fluorescent dye in water flowing in a channel. We considered two kinds of datasets: basis data and observed data. The former is used to determine the basis functions characterizing the streamwise dependence of variances for three statistics: the mean concentration, root-mean-square (RMS) of fluctuations in the concentration, and RMS of the temporal gradient of the fluctuating concentration. Consistent with Taylor’s theory, we found that the lateral distribution of each statistic was basically Gaussian, and their standard deviations increased as a function of the square root of the distance from the emitted point. Based on these facts, a basis function can be formulated and expected to be valid for estimation of unknown sources. Source estimation was performed with the observed data, which corresponded to limited available information about the concentration from an unknown point source. We confirmed a good prediction accuracy of the proposed method with an averaged bias as small as the turbulent integral scale. Better precision was achieved by employing several statistics simultaneously. In this case, the standard deviation of the estimated source position was assessed at 14 % of the mean distance between the source and measurement points, after 100 source-estimate trials with different datasets. The methodology tested in this paper is expected to be applicable more general and complex environmental diffusion issues involving anisotropic turbulent dispersion, and space–time variable mainstream systems; but its versatility in such systems is currently under investigation.     

Recent trends of plutonium fallout observed in Japan: plutonium as a proxy for desertification

Plutonium in monthly deposition samples collected in Tsukuba (the Meteorological Research Institute), Japan from 1990 to end of 2001 is reported, together with monthly plutonium deposition in Nagasaki and Yonaguni in 2000. The annual deposition of (239,240)Pu during the period from 1990 to 2001 shows no systematic interannual variation. However, monthly (239,240)Pu depositions show a typical seasonal variation with a maximum in spring season (March to April), which corresponds to seasonal cycle of soil dusts originating from the East Asian arid area. Plutonium isotopic ratios in the deposition samples suggest that significant amounts of the recent (239,240)Pu deposition observed in Japan are attributed to the resuspension of plutonium-bearing surface soil particles; resuspended plutonium originates from the East Asian arid areas. The recent increased tendency of (239,240)Pu content in residues in deposition samples may reflect desertification in the East Asian continent.     

Characterization of the e ective cellulose degrading strain CTL-6

An e cient cellulose degrading bacteria exists in the thermophilic wheat straw-degrading community, WDC2. However, this strain cannot be isolated and cultured using conventional separation techniques under strict anaerobic conditions. We successfully isolated a strain of e ective cellulose degrading bacteria CTL-6 using a wash, heat shock, and solid-liquid alternating process. Analysis of its properties revealed that, although the community containing the strain CTL-6 grew under aerobic conditions, the purified strain CTL-6 only grew under anaerobic culture conditions. The strain CTL-6 had a striking capability of degrading cellulose (80.9% weight loss after 9 days of culture). The highest e ciency value of the endocellulase (CMCase activity) was 0.404 mol/(min mL), cellulose degradation e ciency by CTL-6 was remarkably high at 50–65°C with the highest degradation e ciency observed at 60°C. The 16S rRNA gene sequence analysis indicated that the closest relative to strain CTL-6 belonged to the genus Clostridium thermocellum. Strain CTL-6 was capable of utilizing cellulose, cellobiose, and glucose. Strain CTL-6 also grew with Sorbitol as the sole carbon source, whereas C. thermocellum is unable to do so.     

Peak wind speed modulation by large-scale motions in neutrally stratified atmospheric surface layer

Environmental Fluid Mechanics - This study applies the models describing the effect of a neutrally stratified high-Reynolds-number boundary layer on peak wind estimation. A neutrally stratified...