Enhanced toluene removal using granular activated carbon and a yeast strain candida tropicalis in bubble-column bioreactors

The yeast strain Candida tropicalis was used for the biodegradation of gaseous toluene. Toluene was effectively treated by a liquid culture of C. tropicalis in abubble-column bioreactor, and the tolueneremoval efficiency increased with decreasing gas flow rate. However, toluene mass transfer from the gas-to-liquid phase was a major limitation for the uptake of toluene by C. tropicalis. The tolueneremoval efficiency was enhanced when granularactivatedcarbon (GAC) was added as a fluidized material. The GAC fluidized bioreactor demonstrated tolueneremoval efficiencies ranging from 50 to 82% when the inlet toluene loading was varied between 13.1 and 26.9 g/m3/h. The yield value of C. tropicalis ranged from 0.11 to 0.21 g-biomass/g-toluene, which was substantially lower than yield values for bacteria reported in the literature. The maximum elimination capacity determined in the GAC fluidized bioreactor was 172 g/m3/h at atoluene loading of 291 g/m3/h. Transient loading experiments revealed that approximately 50% of the toluene introduced was initially adsorbed onto the GAC during an increased loading period, and then slowly desorbed and became available to the yeast culture. Hence, the fluidized GAC mediated in improving the gas-to-liquid mass transfer of toluene, resulting in a high tolueneremoval capacity. Consequently, the GAC bubble-column bioreactor using the culture of C. tropicalis can be successfully applied for the removal of gaseous toluene

Vertical variation of optical properties of mixed Asian dust/pollution plumes according to pathway of air mass transport over East Asia

© Author(s) 2015. This is an Open Access article made available under the terms of the Creative Commons Attribution License 3.0 https://creativecommons.org/licenses/by/3.0/We use five years (2009-2013) of multiwavelength Raman lidar measurements at Gwangju, South Korea (35.10° N, 126.53° E) for the identification of changes of optical properties of East Asian dust depending on its transport path over China. Profiles of backscatter and extinction coefficients, lidar ratios, and backscatter-related Ångström exponents (wavelength pair 355/532 nm) were measured at Gwangju. Linear particle depolarization ratios were used to identify East Asian dust layers. We used backward trajectory modeling to identify the pathway and the vertical position of dust-laden air masses over China during long-range transport. Most cases of Asian dust events can be described by the emission of dust in desert areas and subsequent transport over highly polluted regions of China. The Asian dust plumes could be categorized into two classes according to the height above ground at which these plumes were transported: (case I) the dust layers passed over China at high altitude levels (> 3 km) until arrival over Gwangju, and (case II) the Asian dust layers were transported near the surface and within the lower troposphere (< 3 km) over industrialized areas before they arrived over Gwangju. We find that the optical characteristics of these mixed Asian dust layers over Gwangju differ depending on their vertical position above ground over China and the change of height above ground during transport. The mean linear particle depolarization ratio was 0.21 ± 0.06 (at 532 nm), the mean lidar ratios were 52 ± 7 sr at 355 nm and 53 ± 8 sr at 532 nm, and the mean Ångström exponent was 0.74 ± 0.31 for case I. In contrast, plumes transported at lower altitudes (case II) showed low depolarization ratios (0.13 ± 0.04 at 532 nm), and higher lidar ratio (63 ± 9 sr at 355 nm and 62 ± 8 sr at 532 nm) and Ångström exponents (0.98 ± 0.51). These numbers show that the optical characteristics of mixed Asian plumes are more similar to optical characteristics of urban pollution. We find a decrease of the linear depolarization ratio of the mixed dust/pollution plume depending on transport time if the pollution layer traveled over China at low heights, i.e., below approximately 3 km above ground. In contrast, we do not find such a trend if the dust plumes traveled at heights above 3 km over China. We need a longer time series of lidar measurements in order to determine in a quantitative way the change of optical properties of dust with transport time.Peer reviewedFinal Published versio

Technical note: Absorption aerosol optical depth components from AERONET observations of mixed dust plumes

© Author(s) 2019.Absorption aerosol optical depth (AAOD) as obtained from sun–sky photometer measurements provides a measure of the light-absorbing properties of the columnar aerosol loading. However, it is not an unambiguous aerosol-type-specific parameter, particularly if several types of absorbing aerosols, for instance black carbon (BC) and mineral dust, are present in a mixed aerosol plume. The contribution of mineral dust to total aerosol light absorption is particularly important at UV wavelengths. In this study we refine a lidar-based technique applied to the separation of dust and non-dust aerosol types for the use with Aerosol Robotic Network (AERONET) direct sun and inversion products. We extend the methodology to retrieve AAOD related to non-dust aerosol (AAODnd) and BC (AAODBC). We test the method at selected AERONET sites that are frequently affected by aerosol plumes that contain a mixture of Saharan or Asian mineral dust and biomass-burning smoke or anthropogenic pollution, respectively. We find that aerosol optical depth (AOD) related to mineral dust as obtained with our methodology is frequently smaller than coarse-mode AOD. This suggests that the latter is not an ideal proxy for estimating the contribution of mineral dust to mixed dust plumes. We present the results of the AAODBC retrieval for the selected AERONET sites and compare them to coincident values provided in the Copernicus Atmosphere Monitoring System aerosol reanalysis.We find that modelled and AERONET AAODBC are most consistent for Asian sites or at Saharan sites with strong local anthropogenic sources.Peer reviewe

Sigma Model BPS Lumps on Torus

We study doubly periodic Bogomol'nyi-Prasad-Sommerfield (BPS) lumps in supersymmetric CP^{N-1} non-linear sigma models on a torus T^2. Following the philosophy of the Harrington-Shepard construction of calorons in Yang-Mills theory, we obtain the n-lump solutions on compact spaces by suitably arranging the n-lumps on R^2 at equal intervals. We examine the modular invariance of the solutions and find that there are no modular invariant solutions for n=1,2 in this construction.Comment: 15 pages, 3 figures, published versio

Observation of Conduction Band Satellite of Ni Metal by 3p-3d Resonant Inverse Photoemission Study

Resonant inverse photoemission spectra of Ni metal have been obtained across the Ni 3$p$ absorption edge. The intensity of Ni 3$d$ band just above Fermi edge shows asymmetric Fano-like resonance. Satellite structures are found at about 2.5 and 4.2 eV above Fermi edge, which show resonant enhancement at the absorption edge. The satellite structures are due to a many-body configuration interaction and confirms the existence of 3$d^8$ configuration in the ground state of Ni metal.Comment: 4 pages, 3 figures, submitted to Physical Review Letter