Interaction between water soluble and volatile compounds of Cistus ladanifer L.

Summary. Phytotoxic activity of single and combined application of water soluble and volatile compounds of Cistus ladanifer on germination and early root growth of subterranean clover was investigated. Total germination, lag and speed of germination were both inhibited and stimulated, with the activity of volatiles on total germination depending upon the presence of water solubles. Antagonism between water solubles and volatiles was always found, resulting in a reduction of inhibition or a shift from inhibition to stimulation. It is suggested that the simultaneous presence of water solubles and volatiles might result in changes of the chemical nature of metabolites released by C. ladanifer. Early root growth was always inhibited but only by water solubles, and no interaction was found. The ecological implications of these results are discussed in terms of the exhaustion of competitors seedbanks by a two-step process in which germination is less inhibited or even stimulated by water solubles and volatiles, followed by a stronger and volatiles-independent inhibition of early root growth. Received 13 June 2001; accepted 13 Dezember 2001.     

Concentration Evolution of Gas Species within a Collapsing Bubble in a Liquid Medium

In this study numerical methods are used to investigate the relationship between chemical concentration of gas species within a cavitating bubble, equilibrium radius of the gas bubble and pressure variations in the ambient liquid. For this purpose, governing equations are developed to describe the dynamic equilibrium of a bubble in a flowing fluid and mass transfer between gas and liquid phases, where it was assumed that gases undergo isothermal compression, obey the ideal gas law, Henry law. It is further assumed that the concentration of each phase within the bubble is uniform. The resulting nonlinear equations are solved using implicit Trapezoidal method with Newton iteration. Four gas species are modeled under various initial and ambient pressure variation conditions. These conditions maybe considered to represent typical cavitation events. The numerical results obtained are presented in terms of dimensionless numbers. These results indicate that chemical damage maybe an important component of cavitation surface damage, since high concentration profiles may develop within a collapsing bubble. Proposed formulation and numerical solutions are simple and cost effective to implement. The results presented in this study maybe used to benchmark experimental investigations or other more complex solutions, which are outside the scope of this study.     

Pattern recognition of the movement tracks of medaka (Oryzias latipes) in response to sub-lethal treatments of an insecticide by using artificial neural networks

Specimens of medaka (Oryzias latipes) were observed continuously through an automatic image recognition system before and after treatments of an anti-cholinesterase insecticide, diazinon (0.1 mg/l), for 4 days in semi-natural conditions (2 days before treatment and 2 days after treatment). The "smooth" pattern was typically shown as a normal movement behavior, while the "shaking" pattern was frequently observed after treatments of diazinon. These smooth and shaking patterns were selected for training with an artificial neural network. Parameters characterizing the movement tracks, such as speed, degree of backward movements, stop duration, turning rate, meander, and maximum distance movements in the y-axis of 1-min duration, were given as input (six nodes) to a multi-layer perceptron with the back propagation algorithm. Binary information for the smooth and shaking patterns was separately given as the matching output (one node), while eight nodes were assigned to a single hidden layer. As new input data were given to the trained network, it was possible to recognize the smooth and shaking patterns of the new input data. Average recognition rates of the smooth pattern decreased significantly while those for the shaking pattern increased to a higher degree after treatments of diazinon. The trained network was able to reveal the difference in the shaking pattern in different light phases before treatments of diazinon. This study demonstrated that artificial neural networks could be useful for detecting the presence of toxic chemicals in the environment by serving as in-situ behavioral monitoring tools.     

Wet air oxidation of a reactive dye solution using CoAlPO(4)-5 and CeO(2) catalysts

Wet air oxidation of a prepared reactive dye solution was performed to assess the efficacy of CoAlPO(4)-5 and CeO(2) as catalysts in the reaction. Via adsorption and oxidation of dye, CoAlPO(4)-5 effectively decreased American Dye Manufacturers Institute and chemical oxygen demand (COD) values in the dye solution. At a reaction temperature of 135 degrees C and an applied pressure of 1.0 MPa, color and COD removal were as high as 95% and 90%, respectively, after 2 h. Active sites on the outer surface of CoAlPO(4)-5 are responsible for adsorption and decomposition of dye while active sites in the pores dominate further destruction and oxidation of intermediate products. Since the outer surface only represents a minor part of the total surface, the color removal does not increase appreciably with loading of CoAlPO(4)-5. The CeO(2) catalyst, calcined from cerium chloride under high thermal impact (type A CeO(2)) was very effective in removing color and COD from the solution. This catalyst demonstrated near 100% color removal at temperatures above 135 degrees C and the COD removal could be above 95% at 165 degrees C. With both CoAlPO(4)-5 and CeO(2) catalysts, COD rose and then fell back during the reaction, a feature typical of a consecutive reaction. In contrast to prepared CeO(2), a commercial CeO(2) did not exhibit any catalytic ability for the removal of color and COD. The durability of both CoAlPO(4)-5 and prepared CeO(2) is considered to be fair.     

Dissolution of zinc oxide nanoparticles in exposure media of algae,daphnia, and fish embryos for nanotoxicological testing

Zinc oxide nanoparticles (ZnO NPs) are being widely investigated in a bioassay due to potential negative effects to biological receptor. The dissolution of metal nanoparticles such as ZnO NPs is crucial to interpret nanotoxicity results because ZnO NPs can release toxic-free ions in exposure media. In the present study, dissolution of ZnO NPs was evaluated in three selected synthetic media for aquatic toxicological testing: Elendt M4 daphnia medium, OECD algal medium, and fish embryo rearing solution. Both media are currently recommended for OECD testing for daphnia and algae. Time-dependent dissolution of ZnO NPs has been investigated in terms of sonication time to be used for the preparation of aqueous NPs suspension, and dissolution time corresponding to exposure period in toxicity testing. Since sonication is widely applied for NPs dispersion in the most of nanotoxicological testing, the emphasis of this study was on the dissolution of NPs as a function of sonication time. We also investigated the concentration-dependent dissolution of ZnO NPs. Our results demonstrated that dissolution of ZnO NPs was significantly affected by sonication and dissolution time, as well as NPs concentration. This study showed that parameters affecting dissolution of ZnO NPs should be considered in nanotoxicological testing.     

An improved method of removal for high concentrations of NO by electro-scrubbing process

In the Ag(II)/Ag(I) redox mediator integrated scrubber system, NO reacts with the Ag(II) ions produced by the electrochemical oxidation of Ag(I) in an electrochemical cell present in the scrubbing solution (aqueous HNO₃ acid) to form NO₂. This NO₂ is then absorbed into the scrubbing solution and degraded to nitrate. Numerous experimental runs were carried out to evaluate the feasibility of the integrated system to treat industrial waste gases containing high NO_x levels. The results showed that the levels of NO and NO_x removal increased with increasing Ag(II) loading and contact time. Under optimized conditions, 93.5% and 73.3% of the NO and NO_x, respectively, were removed by a single stage gas scrubber with 1.62 g L^?1 Ag(II) operating at 25 °C and atmospheric pressure.     

A New Flood Index for Use in Evaluation of Local Flood Severity: A Case Study of Small Ungauged Catchments in Korea1

Ahn, Jae Hyun and Hyun Il Choi, 2013. A New Flood Index for Use in Evaluation of Local Flood Severity: A Case Study of Small Ungauged Catchments in Korea. Journal of the American Water Resources Association (JAWRA) 49(1): 1‐14. DOI: 10.1111/jawr.12025 Abstract: The aim of this article is to develop a new index measuring the severity of floods in small ungauged catchments for initial local flood information by the regression analysis between the new flooding index and rainfall patterns. Although a rapid local flood caused by heavy storm in a short period of time is now one of common natural disasters worldwide, such a sudden and violent hydrologic event is difficult to forecast. As local flooding rises rapidly with little or no advance warning, the key to local flood forecasting is to quickly identify when and where local flooding above a threshold is likely to occur. The new flooding index to characterize local floods is measured by the three normalized relative severity factors for the flood magnitude ratio, the rising curve gradient, and the flooding duration time, quantifying characteristics of flood runoff hydrographs. The new flooding index implemented for the two selected small ungauged catchments in the Korean Peninsula shows a very high correlation with logarithm of the 2‐h maximum rainfall depth. This study proposes 30 mm of rainfall in a 2‐h period as a basin‐specific guidance of precaution for the incipient local flooding in the two study catchments. It is expected that the best‐fit regression equation between the new flooding index and a certain rainfall rate can provide preliminary observations, the flood threshold, and severity information, for use in a local flood alert system in small ungauged catchments. Editor's note: This paper is part of a featured series on Korean Hydrology. The series addresses the need for a new paradigm of river and watershed management for Korea due to climate and land use changes.     

Combination of ion exchange system and biological reactors for simultaneous removal of ammonia and organics

A novel process for a simultaneous removal of ammonia and organics was developed on the basis of ion exchange and biological reactions. From batch experiments, it was found out that NH₄⁺ could be removed effectively by combining cation exchange and biological nitrification showing 0.98 mg N/m²?s of a maximum flux. On the other hand, the removal of NO₃⁻ was 3.5 times faster than NH₄⁺ and the maximum flux was calculated to be 3.4 mg N/m²?s. The systems for NH₄⁺ and NO₃⁻ removal were combined for establishing the IEBR process. When the process was operated in a continuous mode, approximately 95.8% of NH₄⁺ was removed showing an average flux of 0.22 mg N/m²·s. The removal efficiency of total nitrogen was calculated as 94.5% whereas that of organics was 99.5%. It was concluded that the IEBR process would be effectively used for a simultaneous removal of NH₄⁺ and organics.     

Distribution and hydrodynamic model of the Keumdong oil spill in Kwangyang Bay, Korea

Oil concentrations in the seawater, seabed sediments, and shoreline sediments were measured from the samples collected 165 days after the Keumdong oil spill accident, which had occurred in Kwangyang Bay of the South Sea, Korea in September 1993. Distribution patterns of the concentrations in the seabed and shoreline sediments have allowed us to hindcast the transport and fate of the spilled oil. Overall, the patterns agree better with the southward (seaward) surface water circulation than with the northward (landward) bottom water circulation over the region. Rapid, initial dispersal of the spilled oil to the south and its subsequent grounding onto the intertidal seabed sediments, as well as onto the shorelines, appear to have made ineffective the subsurface oil transport by the bottom current.