• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.19 no.1
• /
• pp.53-65
• /
• 2014

In order to estimate the effect of nutrients addition for phytoplankton growth and community compositons in spring and summer season, we investigated the abiotic and biotic factors of surface and bottom waters at 20 stations of inner and offshore areas in Gwangyang Bay, Korea. Nutrient additional experiments were also conducted to identify any additional nutrient effects on phytoplankton assemblage using the surface water for the assay. Bacillariophyceae occupied more than 90% of total phytoplankton assembleges. Of these, diatom Eucampia zodiacus and Skeletonema costatum-like species was mainly dominated in spring and summer, respectively. Here, we can offer the season why the two diatom population densities were maintained at high levels in both seasons. First, light transparency of spring season in the euphotic zone was greatly improved in the bay. This improvement is one of important factor as tigger of increase in E. zodiacus population. Second, low salinity and high nutrient sources supplied by Seomjin River discharge are a main cue for strong bottom-up effects on S. costatum-like species during the summer rainy season. Based on the algal bio-assays, although maximum growth rate of phytoplankton communities at inner bay (St.8) were similar to those of outer bay (St.20), half-saturation constant ($K_s$) for phosphate at outer bay was slightly lower than those of inner bay. This implied that adapted cells in low nutrient condition of outer bay may have enough grown even the low phosphate and they also have a competitive advantage against other algal species under low nutrient condition. In particular, efficiency of N (+) addition in summer season was higher compared to control and P added experiments. In the bay, silicon was not a major limiting factor for phytoplankton growth, whereas nitrogen (N) was considered as a limiting factor during spring and summer. Therefore, a sufficient silicate supply form water mixing Si recycled from diatom decomposition and river water is favorable form maintaining diatom ecosystems in Gwangyang Bay.

• The Korean Journal of Food And Nutrition
• /
• v.24 no.4
• /
• pp.551-558
• /
• 2011

This present study was performed to analyze the efficiency and volatility of a porous film containing $Chamaecyparis$ $obtusa$ extract as a method to effectively package food compounds. Phytoncide was contacted the state of gas and showed effective antimicrobial properties. Limonene can be distilled without decomposition as a relatively stable terpene and was one of the extract components. $Chamaecyparis$ $obtusa$ essential oil. The optimal solvent composition was a ratio 5:20:0.3 of T-500:ethanol:hardener to effectively manufacture film containing phytoncide essential oil and the minimum antibacterial concentration was 2%. The films were made under different conditions(A-50LF1, A-25SF2, B-50SF1, C-50LF1, C-25SF2 and D-50SF1) containing phytoncide and the amounts of limonene inside the 1-L reaction chamber depending on storage were measured by gas chromatography-mass selective detention. The results showed that the 25SF2(width, 25 mm; length, 20 cm) revealed more amount of limonene compared with 50LF1(width 50 mm, length 20 cm). We confirmed that the gas emission amount showed a better layer on the film side than on the internal film. An effect of film thickness on phytoncide emissions was observed in that the amounts was less than the expectation for a thicker film at the beginning time, but the emitting amounts increased with increasing storage periods. In the storage testing of various films at $35^{\circ}C$ and 70% humidity for 14 days, 25SF2 showed longer preservation compared with that of 50LF in the case of bread. $C.$ $obtusa$ essential oil is a useful fresh ingredients, hence, analysis of limonene emission kinetics from various film was helpful to develop films with an optimal antimicrobial effect, and will allow application of such films in food packaging systems.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.4
• /
• pp.368-375
• /
• 2006

Single and complex metal oxide catalysts supported onto a commercial DT51D $TiO_2$ have been investigated for gas-phase TCE oxidation in a continuous flow type fixed-bed reaction system to develop a better design approach to catalysts for this reaction. Among the $TiO_2$-supported single metal oxides used, i.e., $CrO_x,\;FeO_x,\;MnO_x,\;LaO_x,\;CoO_x,\;NiO_x,\;CeO_x\;and\;CuO_x$, with the respective metal contents of 5 wt.%, the $CrO_x/TiO_2$ catalyst was shown to be most active for the oxidative TCE decomposition, depending significantly on amounts of $CrO_x\;on\;TiO_2$. The use of high $CrO_x$ loadings greater than 10 wt.% caused lower activity in the catalytic TCE oxidation, which is probably due to production of $Cr_2O_3$ crystallites on the surface of $TiO_2$. $CrO_x/TiO_2$-supported $CrO_x$-based bimetallic oxide catalysts were of particular interest in removal efficiency for this TCE oxidation reaction at reaction temperatures above $200^{\circ}C$, compared to that obtained with $CrO_x$-free complex metal oxides and a 10 wt.% $CrO_x/TiO_2$ catalyst. Catalytic activity of 5 wt.% $CrO_x-5$ wt.% $LaO_x$ in the removal reaction was similar to or slightly higher than that acquired for the $CrO_x$-only catalyst. Similar observation was revealed for 5 wt.% $CrO_x$-based bimetallic oxides consisting of either 5 wt.% $MnO_x,\;CoO_x,\;NiO_x\;or\;FeO_x$. These results represent that such $CrO_x$-based bimetallic systems for the catalytic TCE oxidation on significantly minimize the usage of $CrO_x$ that is well known to be one of very toxic heavy metals, and offer a very useful technique to design new type catalysts for reducing chlorinated volatile organic substances.

• Applied Chemistry for Engineering
• /
• v.9 no.3
• /
• pp.330-335
• /
• 1998

The objectives of this study are summarized with two. The one is to remove of $COD_{Cr}$, color and turbidity with coagulation and ozonation in nonbiodegradable landfill leachate, the other is to compare of water qualities with pre-ozonation and post-ozonation. The results are summarized as follows ; 1) 90 minutes ozonation with $75mgO_3/min$($4.5gO_3/hr$) was conducted at pH 4,7, 10 to remove $COD_{Cr}$. Removal efficiencies were investigated with 48.2%, 52.6%, and 62.3% respectively. As increasing pH, $COD_{Cr}$ removal efficiencies were increased, it was considered that hydroxyl radical($OH{\cdot}$) which strongly oxdize and nonselectively react with organic compounds, was rapidly produced by ozone self-decomposition at high pH. 2) Alum, ferric chloride and ferrous sulfate were used for coagulation as inorganic coagulant. Ferric chloride was investigated with optimal coagulant, and it removed $COD_{Cr}$ about 12.0% at pH5 and dosage of $2,000m{\ell}/{\ell}$. Cation(C-101P), anion(A-601P) and nonion(SC-050) were tested to remove organic pollutants in landfill leachate. Cation(C-101P) was investigated with the most effective organic coagulant, and removal efficiency of $COD_{Cr}$ was 19.8% at pH5 and dosage of $100m{\ell}/{\ell}$. 3) Color and turbidity were removed up to 88.6%, 97.0% at pH10, when contacted 90 minutes with ozone, respectively. These removal efficiencies were much higher than those of $COD_{Cr}$ and $COD_{Mn}$. It was considered that ozone could oxdize the triggering materials of color and turbidity selectively and preferentially. 4) $COD_{Cr}$, color and turbidity were more effectively removed with pre-ozonation than post-ozonation about 8%, 3.5% and 1% respectively. These results were well corresponed with other's studies that pre-ozonation will increase the effect of coagulation.