Removal characteristics of CO2 using aqueous MEA/AMP solutions in theabsorption and regeneration process

The carbon dioxide (CO2) removal efficiency, reaction rate, and CO2 loading into aqueous blended monoethanolamine (MEA) + 2-amino-2-methyl-1-propanol (AMP) solutions to enhance absorption characteristics of MEA and AMP were carried out by the absorption/regeneration process. As a result, compared to aqueous MEA and AMP solutions, aqueous blended MEA+AMP solutions have a higher CO2 loading than MEA and a higher reaction rate than AMP. The CO2 loading of rich amine of aqueous 18 wt.% MEA+12 wt.% AMP solution was 0.62 mol CO2/mol amine, which is 51.2% more than 30 wt.% MEA (0.41 mol CO2/mol amine). Consequently, blending MEA and AMP could be an effective way to design cousidering economical efficiency and used to operate absorber for a long time.     

Dioxin and dioxin-like PCB profiles in the serum of industrial and municipal waste incinerator workers in Korea

To assess occupational exposure, we determined the concentrations of PCDD/Fs and PCBs in human serum samples from 26 incinerator workers (10 industrial waste and 16 municipal solid waste incinerator workers), 38 residents near the facilities and 7 inhabitants (as control subjects) living over 10 km away from any incinerator facilities in Korea. The mean TEQ_WHO levels of PCDD/Fs in the industrial and MSWI workers were 41.57 and 9.86 pg TEQ_WHO g^? 1 lipid, respectively. For the residents, the mean TEQ_WHO was 13.47 pg TEQ_WHO g^? 1 lipid (residents near IWI, MSWI, and control subjects: 17.64, 13.31, and 6.91 pg TEQ_WHO g^? 1 lipid). Higher levels of certain PCDD/F congeners, mainly PCDFs, were detected in the serum of industrial incinerator workers in comparison to the levels measured in the residents. Significant differences were observed for PCDFs, the major compounds were OCDF, 1,2,3,4,6,7,8-HpCDF, and the minor components 1,2,3,4,7,8-HxCDF, 1,2,3,6,7,8-HxCDF, and 2,3,4,6,7,8-HxCDF (p < 0.01). The PCDD/F congener patterns and concentrations measured in the 71 serum samples examined suggest that the industrial incinerator workers were exposed to PCDD/Fs in the workplace, possibly through inhalation and/or skin contact. In contrast, the levels and congener patterns of PCBs measured were similar in all subjects, indicating that workers from the incinerator facilities examined were not subjected to additional exposure to these compounds.     

Distributions of heavy metals in the sediments of South Korean harbors

Bottom sediments of harbors in the South Korea have been long suspected for metal contamination due to ship-based and urban-based activities for the past several decades. A number of areas have been suspected to impair ecosystem services to the local residents and drawn complaints from main stakeholders. Twelve contamination suspected harbors were subject to evaluate the level of contamination of Cr, Ni, Cu, Zn, As, Cd, Pb and Hg. The level of sediment contamination for each metal was evaluated comparing the relative enrichment of a given metal to pollution-insensitive aluminum. Regional background concentration of a given metal was also determined based on its down core measurement and sediment texture. Ecological risk posed by the presence of heavy metals was evaluated using the sediment quality guidelines (SQGs) developed by United States National Ocean and Atmosphere Administration (US NOAA) as benchmarks for evaluating sediment chemistry to aquatic organisms. Cu, Zn, Cd, Pb and Hg in the surface sediment were found to be higher than a factor of 1.5 than background sediments, and the overall metal contaminations of surface sediment can be regarded as medium–high- to high-priority sites in the sense of SQGs.     

Glucosinolates and other metabolites in the leaves of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> from natural populations and their effects on a generalist and a specialist herbivore

Because many secondary metabolites in plants act as defense against herbivores it has been postulated that these compounds have evolved under selective pressure by insect herbivores. One explanation for the within-species variation in metabolite patterns in a particular species is that different populations are under selection by different herbivores. We tested this hypothesis, using Arabidopsis thaliana plants that originated from dune and inland areas. We analyzed Arabidopsis thaliana leaves using NMR spectroscopy and multivariate data analysis. Major differences in chemical composition were found in water-methanol fractions and were due to higher concentrations of sinigrin and fumaric acid in dune plants. Inland plants showed lower levels of glucose. Quantitative analysis of glucosinolates was performed with HPLC. Individual plants and populations demonstrated differences in glucosinolate composition and concentration. In growth chamber experiments, the generalist herbivore, Spodoptera exigua grew significantly better on the inland plants, while the specialist herbivore Plutella xylostella performed equally well on plants of both origins. Aliphatic glucosinolate as well as total glucosinolate concentrations negatively correlated with larval mass of Spodoptera exigua. No significant correlations, however, were found between larval mass of Plutella xylostella and glucosinolates in the leaves. A specialist and a generalist herbivore were responding differently to plant secondary chemistry, as was also found in several other studies. This is an important indication that differences in glucosinolate concentrations among populations may result from differential selection by different guilds of herbivores.     

Repeated-dose toxicity attributed to aluminum nanoparticles following 28-day oral administration,particularly on gene expression in mouse brain

Nanotechnology is a rapidly growing industry that has elicited much concern due to the lack of available toxicity data. Aluminum oxide nanoparticles (AlNP) were listed as a high-priority group in the Organization for Economic Co-operation and Development (OECD) Steering Group for Test Guidelines. In this study, AlNP 35 ± 18.8 nm in size were administered daily at doses of 15, 30, or 60 mg k^?1 for 28 days. A significant decrease in white blood cells (WBC), neutrophils, lymphocytes, and monocytes was observed in the group treated with 60 mg kg^?1 of AlNP, accompanied by a significant increase in platelets. The concentration of aluminum (Al) rose significantly in the thymus, lung, and brain of the group treated with 60 mg kg^?1 of AlNP. However, no significant changes in histopathology were observed. The expression for feeding behavior, energy expenditure, and neurodegeneration-related genes were up-regulated more than twofold by 60 mg kg^?1 AlNP. Consequently, data suggest that exposure to AlNP may result in adverse health effects, including but not limited to growth inhibition, immunosuppression, and neurodegeneration.     

Enhanced photocatalytic degradation of lindane using metal–semiconductor Zn@ZnO and ZnO/Ag nanostructures

To achieve enhanced photocatalytic activity for the degradation of lindane, we prepared metal–semiconductor composite nanoparticles (NPs). Zn@ZnO core–shell (CS) nanocomposites, calcined ZnO, and Ag-doped ZnO (ZnO/Ag) nanostructures were prepared using pulsed laser ablation in liquid, calcination, and photodeposition methods, respectively, without using surfactants or catalysts. The as-prepared catalysts were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscopy, high-resolution transmission electron microscopy, ultraviolet–visible (UV–vis) spectroscopy, and photoluminescence spectroscopy. In addition, elemental analysis was performed by energy dispersive X-ray spectroscopy. The obtained XRD and morphology results indicated good dispersion of Zn and Ag NPs on the surface of the ZnO nanostructures. Investigation of the photocatalytic degradation of lindane under UV–vis irradiation showed that Zn@ZnO CS nanocomposites exhibit higher photocatalytic activity than the other prepared samples. The maximum degradation rate of lindane was 99.5% in 40 min using Zn@ZnO CS nanocomposites. The radical trapping experiments verified that the hydroxyl radical (·OH) was the main reactive species for the degradation of lindane.     

Plant uptake and downward migration of 85Sr and 137Cs after their deposition on to flooded rice fields: lysimeter experiments with and without the addition of KCl and lime

In order to study the plant uptake and downward migration of radiostrontium and radiocesium deposited on to a flooded rice field, 85Sr and 137Cs were applied to the standing water over an acidic sandy soil in planted lysimeters. The plant uptake was quantified with the areal transfer factor (TFa, m2 kg(-1)-dry plant). Following the spiking 14 days after transplanting, the TFa values for the hulled seeds were 3.9 x 10(-4) for 85Sr and 1.4 x 10(-4) for 137Cs, whereas those for the straws were 1.3 x 10(-2) and 3.2 x 10(-4), respectively. The 137Cs TFa from the spiking at the anthesis/milky-ripe stage was several times higher than that from the earlier spiking, whereas the difference was much less in the 85Sr TFa. Such an increase in the 137Cs TFa was attributed mainly to an enhanced plant-base uptake. The addition of KCl and lime after the spiking significantly reduced the TFa values of both radionuclides. The reducing effect was greater for the later spiking. An appreciable fraction of the applied activity leached out of the lysimeter for 85Sr, whereas a negligible fraction leached for 137Cs. The leaching was remarkably increased by the KCl and lime addition for both. A conspicuous localization of 137Cs with respect to the soil surface was observed. In a batch experiment, the 137Cs concentration in the standing water decreased more rapidly than that of 85Sr, both of which were fitted to the power functions of the elapsed time. To add KCl and lime slowed such decreases to lessen the distribution coefficients (Kd) of both 85Sr and 137Cs.     

Vertical distribution and characteristics of soil humic substances affecting radionuclide distribution

The humic substances extracted from different soil depths are separated into humic (HA) and fulvic (FA) acids, and characterized for their chemical composition, proton exchange capacity, spectroscopic characteristics and binding properties to the europium ion. The chemical and spectroscopic results show that FA compared to HA has a relatively high O/C ratio, high acidic functional group contents and low aromatic contents. The synchronous fluorescence spectroscopic results show that the stability constant (K) of the soil humic substances with Eu(III) ion tends to increase as the soil depth becomes deeper, and HA has a slightly stronger binding ability than FA. The measured total site concentrations (C(L)) reveal that Eu(III) ion is loaded onto HA by 62-77% of the total acid sites, but FA is only approximately 50% covered by Eu(III) ion. Information could be useful in understanding the migration of radionuclides in soil layer.     

Atmospheric versus lithogenic contribution to the composition of first- and second-order stream waters in Seoul and its vicinity

The spatial variations in the chemistry of first- and second-order stream waters (N = 65) were investigated in the easterly bound of Seoul in order to assess the effects of urban air pollution on surface water chemistry. The sulfate (SO4(2-)) was high (range 3.9-17.8 mg l(-1), mean 11.8 mg l(-1)) within 30 km away from the center of Seoul, compared to the levels (range 1.1-7.7 mg l(-1), mean 4.3 mg l(-1)) observed in remote areas (30-70 km away). Both graphical examination and statistical evaluation (variogram) of sulfate concentration data consistently showed the decrease of sulfate concentration with increasing distance. The results of mass balance modeling also indicate that the concentrations of SO4(2-), Cl- and Na+ may be affected mainly by dry/wet deposition. However, the spatial variations of major cations such as Ca2+ and Na+ are well explained by the reaction of rainwater with diverse rocks in the watercourse. The water type was found to change from Ca(-Na)-SO4) type to Ca(-a)-HCO3 type with the increasing distance. It is thus inferred that the pollutants like SO2 emitted from strong man-made source areas of Seoul are transported to the considerable distance (at least 30 km away) by westerlies and that such mechanism may lead to the changes of the anion composition in surface water. In the remote area (> 30 km away from Seoul), the stream water chemistry appears to be influenced more effectively by the weathering of rock-forming minerals.