Effect of external iron and arsenic species on chelant-enhanced iron bioavailability and arsenic uptake in rice (Oryza sativa L.)

This study was conducted to investigate the effect of external iron status and arsenic species on chelant-enhanced iron bioavailability and arsenic uptake. Rice seedlings (Oryza sativa L.) were used as model plant, and were grown in artificially contaminated sandy soils irrigated with Murashige and Skoog (MS) culture solution. Arsenate uptake in roots and shoots of rice seedlings were affected significantly (p > 0.05) while dimethylarsinic acid (DMAA) was not by the additional iron and chelating ligand treatments. Regardless of iron concentrations in the soil solution, HIDS increased arsenic uptake for roots more than EDTA and EDDS. Chelating ligands and arsenic species also influenced iron uptake in rice roots. Irrespective of arsenic species, HIDS was found to be more effective in the increase of iron bioavailability and uptake in rice roots compared to other chelants. There was a significant positive correlation (r = 0.78, p < 0.05) between arsenate and iron concentrations in the roots of rice seedlings grown with or without additional iron indicating that arsenate inhibit iron uptake. In contrast, there was no correlation between iron and DMAA uptake in roots. Poor correlation between iron and arsenic in shoots indicated that iron uptake in shoots was neither affected by additional iron nor by arsenic species. Compared to the control, chelating ligands increased iron uptake in shoots of rice seedlings significantly (p < 0.05). Regardless of additional iron and arsenic species, iron uptake in rice shoots did not differed among EDTA, EDDS, and HIDS treatments.     

Hydrolysis of <Emphasis Type="Italic">Sasa senanensis</Emphasis> culm with dilute sulfuric acid for production of a fermentable substrate

To prepare a substrate for microbial conversion of xylose into xylitol, the culm of Sasa senanensis was hydrolyzed with dilute sulfuric acid. When the reaction temperature was fixed at 121°C, an optimum yield of xylose was obtained by treatment with 2% sulfuric acid for 1 h. An increase in the sulfuric acid concentration or a prolonged reaction time resulted in a decrease in the xylose yield. A fermentable substrate with a relatively high xylose concentration (36.7 g l⁻¹) was obtained by hydrolysis with 2% sulfuric acid with a liquid-to-solid ratio of 5 g g⁻¹. During hydrolysis at elevated temperatures, certain undesired byproducts were also generated, such as degradation products of solubilized sugars and lignin, which are potential inhibitors of microbial metabolism. These compounds were, however, successfully removed from the hydrolysate by treatment with activated char.     

Combined biological and photocatalytic treatment for the mineralization of phenol in water

Phenol is degraded by biological treatment, however mineralization requires long time. To decrease the time and operational cost necessary for the mineralization of phenol, an optimum operation condition of the combined biological–photocatalytical treatment was investigated. The mineralization of phenol (50 mg l⁻¹) was conducted in a flow-type biomembrane tank combined with a batch-type TiO₂-suspended photocatalytic reactor. Phenol was degraded biologically to the concentration of 6.8 mg l⁻¹, an effective concentration for further photocatalytic treatment. After the biological treatment, the biotreated phenol was treated photocatalytically to complete the mineralization of phenol. The combined treatment shortened the mineralization time compared to the biological treatment and electric cost compared to the photocatalytic treatment only. The combined treatment may be suitable for a short-time mineralization of phenol in wastewater.     

Load of Heavy Metals in the Airborne Dust Particulates of an Urban City of Central India

The geographical and temporal distribution patterns of airborne dust particulates have been studied in different representative areas of Raipur City. Dust fall samples from different sites were collected and some selected toxic metals namely Cr, Mn, Fe, Ni, Cu, Zn, Sb and Pb in them were determined by AAS. Total annual flux of 11.7, 541.4, 2751.0, 14.2, 9.8, 90.9, 17.6, and 17.7 kg km(-2) y(-1) were measured for Cr, Mn, Fe, Ni, Cu, Zn, Sb, and Pb respectively. The occurrence of metal concentration were generally in the order industrial > heavy traffic > commercial > residential area in Raipur city. The results of analysis show the existence of toxic metal concentration in the order Fe > Mn > Zn > Pb approximately Sb > Ni > Cr > Cu in Raipur city. These large levels of metal pollutants have also been correlated with some meteorological parameters like temperature, relative humidity and wind velocity, and strong positive correlations have been observed.     

Uptake and distribution of 90Sr and stable Sr in rice plants

The stable Sr content in the aboveground parts of rice plants at various growth stages, and the distributions of 90Sr and stable Sr in rice plant components, such as polished rice, rice bran, hull, straw and root, at harvest time, were determined. The total Sr content in the aboveground rice plants was dependent on the growth stage and followed the sigmoidal shape of the growth curve. The concentration of 90Sr among the different components of rice plants varied within two orders of magnitude, whereas the 90Sr/Sr concentration ratio had a constant value. Therefore, the translocation rate of 90Sr in rice plants had similar values to that of stable Sr. However, the 90Sr/Sr concentration ratio for the rice plants was different for each study site. Only 0.6% of the total Sr was found in polished rice, while more than 99% was found in the non-edible components, of which 87% was present in the straw. These findings suggest that 90Sr in the non-edible parts could have been transferred to humans through the soil-plant system and/or feed-livestock pathway. The soil-to-plant transfer factor of 90Sr in polished rice was 0.0021 +/- 0.00007, which was two orders of magnitude lower than that in the straw. The percentage of 90Sr removed from the upper soil layer to the aboveground biomass of rice plants at harvest time was calculated as 0.094%. It is possible that approximately 0.1% of the total 90Sr content in the surface soil layer is removed from the soil-plant system by human activities every year.     

Pedestrian head impact conditions depending on the vehicle front shape and its construction--full model simulation

For the evaluation of pedestrian protection, the European Enhanced Vehicle-Safety Committee Working Group 17 report is now commonly used. In the evaluation of head injuries, the report takes into account only the hood area of the vehicle. But recent pedestrian accident data has shown the injury source for head injury changing to the windshield and A-pillar from the hood. The head contact points are considered to fall on a parallel to the front shape of the vehicle along the lateral direction, but the rigidity of the outer side construction is different from the center area. The purpose of this study is to consider the reason for the change in injury source for recent vehicle models. The head contact points and contact conditions, speed and angle, are thought to be influenced not only by the vehicle's geometry, but also its construction (rigidity). In this study, vehicle-pedestrian impact simulations were calculated with a finite element model for several hitting positions, including the outer side areas. Full dummy sled tests were conducted to confirm the simulation results. These results show that, for impacts at the outer sides of the vehicle, the head contact points are more rearward than at the vehicle center. In addition, the speed and angle of the head contact were found to be influenced by the pedestrian height.     

Polychlorinated dibenzo-p-dioxins and dibenzofurans in commercial diphenyl ether herbicides,and in freshwater fish collected from the application area

This paper describes the analyses of polychlorinated dibenzodioxins, dibenzofurans, and related compounds in diphenyl ether herbicides, CNP, NIP, and X-52. The levels of tetra-, penta-CDDs, and tetra-CDFs were about 150, 30, and 15 ppm, respectively in CNP formulations. NIP and X-52 contained lower chlorine alalogs. Isomer distribution of PCDDs in CNP agreed with an estimate from the reaction of chlorophenols. Freshwater fish samples heavily contaminated with CNP in the application season also contained 0.2 ppb of 1,3,6,8-tetra-CDD.     

Nest defense and early production of the major workers in the dimorphic ant Colobopsis nipponicus (Wheeler) (Hymenoptera : Formicidae)

Summary Production of the major subcaste and its contribution to nest survival in the dimorphic ant Colobopsis nipponicus was examined in the field. In this species, the first major workers were reared in the second brood, very early in the colony life cycle. A field experiment demonstrated that artificial colonies without major workers could not survive, whereas colonies with at least one major worker per nest entrance could. Because major workers of C. nipponicus defend the nest entrance by head plugging, the lack of nest defenders in the experimental colonies seemed to be a major cause of nest failure. The defensive value of major workers was much higher than that of minor workers. Many artificial colonies without major workers were displaced by competitors for nest sites, especially by those of other conspecific colonies. In addition, more than 90% of field colonies nested with other conspecific colonies on the same tree. The early production of major workers in C. nipponicus seemed to be very important for the survival of incipient colonies.     

Elementary reaction path on polychlorinated biphenyls formation from polychlorinated benzenes in heterogeneous phase using ab initio molecular orbital calculation

We have investigated the elementary reaction path on the 3,3',4,4',5,5'-hexachlorinated biphenyl (HxCB) formation from two 1,2,3,5-tetrachlorobenzenes (TCBz) and the catalytic role of copper on this formation using ab initio molecular orbital calculation. The elementary reaction path on the 3,3',4,4',5,5'-HxCB formation from two 1,2,3,5-TCBzs has been shown to occur as follows: Step 1--the dissociation of Cl atom substituted at 5-position in 1,2,3,5-TCBz, Step 2--the association between Cl atom substituted at 5-position in another 1,2,3,5-TCBz and the Cl radical formed in Step 1, Step 3-the elimination of Cl2 molecule from the intermediate species formed in Step 2, and Step 4--the 3,3',4,4',5,5'-HxCB formation from the direct condensation of two 1,2,3-trichlorophenyl radicals formed in Step 1 and Step 3. The geometric factor, which decides the reactivity of this formation, is the C-Cl bond strength of 1,2,3,5-TCBz. The catalytic roles of copper are to stabilize the total energy in the adsorption of 1,2,3,5-TCBz onto the copper surface and to weaken the C-Cl bond strength due to the charge transfer from the 1,2,3,5-TCBz to the copper surface. Moreover, we have achieved the prediction of the minimum energy path on the formation of non- and mono-ortho polychlorinated biphenyls congeners for which TEFs have been determined.