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.     

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.     

Accumulation and Chemical Fractionation of Heavy Metals in Andisols after a Different, 6-year Fertilization Management (8 pp)

Goal, Scope and Background Andisols are widespread in Japan and have some special properties such as high anion exchange capacity, low bulk density, and high organic matter content, which might influence the accumulation or chemical fractionation of heavy metals. However, few such data exist in Japanese andisols. The primary objective of this study was to investigate the distribution and chemical fractions of Cu, Zn, Ni, and Cr in the soil profiles and subsequently to assess their potential environmental hazard. Materials and Methods Soil samples were taken from a field experiment conducted on Japanese andisols, which had received either swine compost or chemical fertilizers for 6 years. Concentrations of Cu, Zn, Ni, and Cr were determined for all of the obtained extract solutions by ICP-AES. Results and Discussion Considerably higher total concentrations of Cu and Zn were observed in the top 20 cm layer of the compost-amended soil, relative to the unfertilized soil, while chemical fertilizers had little effect. Application of the swine compost increased the concentrations of Cu and Zn, but not Ni and Cr, in all fractions in the top 20 cm layer. The greatest increase in the organically bound fraction (OM) Cu and dilute acid-exchangeable fraction (DAEXCH) Zn was observed. This suggests that Cu and Zn are potentially bioavailable and mobile in the andisol profiles after 6-year consecutive applications of the swine compost. On the other hand, distribution of Cu, Zn, Ni and Cr among various soil fractions was generally unaffected by chemical fertilizers. Conclusions We observed that 6-year consecutive applications of the swine compost led to an increase in total metals of Cu and Zn, as well as their all-chemical fractions, in the top 20 cm soil layers. Potential hazard of heavy metals, especially of Cu and Zn, as a result of the use of swine compost on andisols, must be taken into account. Recommendations and Outlook The long-term effect of the accumulation of heavy metals, particularly Cu and Zn, in various plant tissues and soils, as well as their potential risk to surface water via runoff and groundwater via leaching, needs to be carefully considered. Further investigations in the long-term experiments are therefore necessary. - Abbreviations. EXCH, exchangeable fraction of metals; DAEXCH, dilute acid-exchangeable fraction of metals; FeMnOX, iron and manganese-oxide-bound fraction; OM, organically-bound fraction; RESD, residual fraction. COMPOST, SRNF, RANF, and CONTROL stand for compost (from swine wastes), slow-release nitrogen fertilizer (coated urea), readily available nitrogen fertilizer (including NH4-N, P, and K fertilizers), and no fertilizer application, respectively.     

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...