Development of an empirical equation for the transverse dispersion coefficient in natural streams

In this study, a new empirical equation for the transverse dispersion coefficient has been developed based on the hydraulic and geometric parameters in natural streams using a regression technique. First, a total of 32 data sets in 16 streams were collected. Among those sets, 16 sets were used for deriving the new equation, and the other 16 sets were used for verifying the equation. Then, through dimensional analysis, it was found that the normalized transverse dispersion coefficient is associated with several parameters such as sinuosity, aspect ratio, and a friction term. The robust least square method was applied to estimate regression coefficients. The newly proposed equation was proven to be superior in explaining the dispersion characteristics of natural streams more precisely compared to the existing equations.     

Outcome of prenatally diagnosed trisomy 6 mosaicism

We report the prenatal diagnosis of trisomy 6 mosaicism via amniocentesis, in which trisomy 6 cells were identified in three of five culture vessels with 33% (5/15) of colonies showing trisomic cells. The pregnancy was electively terminated and examination revealed minor abnormalities (shortening of the femurs, micrognathia, posterior malrotation of the ears, and bilateral camptomelia of the second digit of the hands and fifth digits of the feet). Cytogenetic analysis of the placenta showed trisomy 6 in 100% of 20 cells studied. Karyotype was 46,XX in 100 cells examined from fetal skin. There are relatively few prenatally diagnosed cases of mosaic trisomy 6 at amniocentesis. Confined placental mosaicism (CPM) has been postulated in other cases where follow-up cytogenetic studies were not available. The present case differs from those previously reported, as it appears to represent CPM of chromosome 6 with phenotypic effects to the fetus. Copyright © 2002 John Wiley & Sons, Ltd.     

SPATIALLY DISTRIBUTED MODELING OF STREAM FLOW DURING STORM EVENTS1

ABSTRACT: The purpose of this paper is to present a new approach for the spatially distributed modeling of water flow during storm events. Distributed modeling of flow during storm events is an important basis for any environmental modeling, including turbidity or sediment transport. During the initial phase of a rainstorm, surface runoff is the main contributor of flow. To provide the spatial components for distributed hydrological modeling a Geographic Information System (GIS) was used to map and visualize contributing areas around a stream channel. Stream segments were defined using the hydrologic response unit (HRU) concept. Lateral flows were derived from GIS output for each segment of the stream and at each time interval of the rain storm and were routed using the kinematic routing equation. This approach is new in hydrological modeling and can be used to enhance many existing simulations. The model is also unique in the fine time scale (i.e., intervals are on the order of minutes). Model results showed good correlation with measured discharge values; however, further studies of contributing area behavior, its relationship with soil types and slope categories, and the influence of watershed size are needed to improve model performance. This model will be used in the future as the basis to model turbidity in streams.     

Combined steam-dry reforming of toluene in syngas over CaNiRu/Al2O3 catalysts

Cracking, steam reforming, dry reforming, and combined steam and dry reforming of toluene in model syngas were performed using catalysts to simulate tar removal produced during biomass gasification. The catalysts were prepared by adding Ru, Ca, and Mn to Ni-based catalysts, and their properties were measured using BET, pulse CO chemisorption, XRD and TG. In steam and dry reforming of toluene, a high toluene conversion was observed with increasing Ca content in the catalyst and catalysts containing Ca showed a higher activity than those containing Mn. In combined steam-dry reforming with syngas, 1%CaNiRu/Al₂O₃ indicated a conversion of 93.9% at 800°C.     

Kinetics of the reactions of soot surface-bound polycyclic aromatic hydrocarbons with the OH radicals

The kinetics of the heterogeneous reaction of OH radicals with 15 polycyclic aromatic hydrocarbons (PAHs) present in laboratory generated simulated kerosene combustion soot was studied at T = 290 K in a low pressure discharge-flow reactor combined with an electron-impact mass spectrometer. The kinetics of soot-bound PAH consumption in reaction with OH were monitored using off-line HPLC measurements of their concentrations in soot samples as a function of time of exposure to OH. Concentration of OH radicals in the gas phase was measured by mass spectrometry. The first-order rate constants measured for the individual PAH at T = 290 K ranged from 0.02 to 0.04 s^?1 and were found to be independent of the OH concentration ([OH] = (0.34–2.5) × 10¹² molecule cm^?3) and of the molecular structure of the PAH. In addition, the uptake coefficient of OH on soot surface and the diffusion coefficient of OH in He were measured to be 0.19 ± 0.03 (calculated with geometric surface area) and (615 ± 80) Torr cm² s^?1, respectively. Comparison of the results on the PAH + OH reaction to those from previous studies carried out on different carbonaceous substrates, indicates probable dependence of the heterogeneous reactivity of PAH toward OH on the substrate nature. Rapid reaction with OH can be an important potential pathway of the atmospheric degradation of non-volatile PAH present mainly in the particulate phase in the atmosphere.     

Life-cycle model of terrestrial carbon exchange

We present here a terrestrial carbon cycle model based on a scheme of the phytomass change, which is continuous in time. The experimental information about net primary production, living and dead phytomass, and soil organic matter for various ecosystems is used for calibration of the model. The suggested model enables to characterize terrestrial ecosystems as carbon sources or carbon sinks and to evaluate intensity of these sources and sinks. The model is applied for the European territory of Russia as a case study. Intensity of the total exchange carbon flux for this territory is evaluated. The obtained results allow to conclude that the given territory is the sink of carbon.     

Estimating bulk optical properties of aerosols over the western North Pacific by using MODIS and CERES measurements

Over the western North Pacific, a large amount of land aerosols from Asian-Pacific countries is transported by the prevailing westerlies. This transport makes the radiative characteristics of these aerosols diverse, particularly when one compares those characteristics over the coastal sea with those over the open sea. In this paper we discuss a method that uses satellite data to obtain the single-scattering albedo (ω) and asymmetry factor (g) of atmospheric aerosols for two large-scale subdivisions—the coastal sea (within 250 km from the coast) and the open sea (the remaining area)—over the western North Pacific (110°E–180°, 20°N–50°N). Our estimation method uses satellite measurements, obtained over a six-year period (2000–2005), of aerosol optical depth (AOD) and shortwave fluxes at both the surface and the top of the atmosphere (TOA); the measurements are obtained using the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth's Radiant Energy System (CERES). For the two subdivisions, the estimated annual means of (ω,g) at 630 nm are significantly different: (0.94, 0.65) over the coastal sea and (0.97, 0.70) over the open sea. From a quantitative viewpoint, this result indicates that in comparison with aerosols over the open sea, those over the coastal sea show greater absorption and lesser forward scattering of solar radiation. The estimated optical properties are responsible for the aerosol surface cooling observed by MODIS and CERES, which is approximately 138 and 108 W m⁻² per AOD over the coastal sea and open sea, respectively.     

Influence of ship emissions on ozone concentrations around coastal areas during summer season

The influence of ship emissions on ozone (O₃) concentrations in a coastal area (CA) including Busan port, Korea was examined based on a numerical modeling approach during a high O₃ episode. The analysis was performed by two sets of simulation scenarios: (1) with ship emissions (e.g., TOTAL case) and (2) without ship emissions (e.g., BASE case). A process analysis (PA) (the integrated processes rate (IPR) and integrated reaction rate (IRR) analyses) was used to evaluate the relative contributions of individual physical and chemical processes in O₃ production in and around the CA (e.g., sites of Dong Sam (DS) and Dae Yeon (DY)). The model study suggested the possibility that pollutant gases emitted from the ships traversing Busan port can exert a direct impact on the O₃ concentration levels in the CA. Largest impacts of ship emissions on the O₃ concentrations were predicted at the coast (up to 15 ppb) and at inland locations (about 5 ppb) due to both the photochemical production of pollutant gases emitted from the ships and meteorological conditions. From the PA, the photochemical production of O₃ (P(O₃)) due to ship emissions in the CA was found to increase by a mean of 1.5 ppb h^?1 (especially by ≥10 ppb h^?1 at the DS site) during the day.