• Korean Journal of Environmental Biology
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• v.38 no.1
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• pp.114-126
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• 2020

Bloom-forming toxic cyanobacteria Microcystis spp. are common in the summer season in temperate freshwater ecosystems. Often, it leads to the degradation of water quality and affects the quality of drinking water. In a previous study, NQ (naphthoquinone) compounds were shown to be effective, selective, and ecologically safe algicides for Microcystis spp. blooms. To analyze the superiority of developed NQ derivatives, we conducted a microcosm experiment using clay, which is frequently used in South Korea. Similar to previous studies, the NQ 40 and NQ 2-0 compounds showed high algicidal activities of 99.9% and 99.6%, respectively, on Microcystis spp. at low concentrations (≥1 μM) and enhanced phytoplankton species diversity. However, when treated with clay, a temporary algicidal effect was seen at the beginning of the experiment that gradually increased at the end. In addition, treatment with the NQ compounds did not affect either the abiotic or biological factors, and similar trends were observed with the control. These results showed that the NQ 2-0 compound was more effective, with no ecosystem disturbance, and more economical than the currently used clay. These results suggest that NQ 2-0 compound could be a selective, economically and ecologically safe algicide to mitigate harmful cyanobacterial blooms in the field.

• Ecology and Resilient Infrastructure
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• v.3 no.2
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• pp.117-125
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• 2016

Current cities encounter various types of water problems due to rapid urbanization and climate change. The increasing significance of urban water problems calls for the establishment of resilient alternatives to prevent and minimize social loss that results from these phenomena. As a background research for establishing resilient infrastructures for the mitigation of urban water problems, we evaluated the robustness of structural alternatives for urban flood as a representative case. Combining the robustness index (RI) and the cost index (CI), we suggested the robustness-cost index (RCI) as an indicator of the robustness of structural alternatives, and applied the index to assess the existing infrastructures and structural alternatives (i.e., sewer network expansion, additional storage tank construction, and green roof construction) at a site prone to floods located around Gangnam-station, Seoul, Korea. At a rainfall intensity frequency range of 2 to 20 years, the usage of a storage tank and a green roof showed relatively high RCI value, with a variation of an alternative showing greater RCI between the two depending on the size of design rainfall. For a rainfall intensity frequency of 30 years, installing a storage tank with some green roofing was the most resilient alternative based on the RCI value. We proposed strategies for establishing resilient infrastructures for the mitigation of urban floods by evaluating the robustness of existing infrastructures and selecting optimal structural alternatives with the consideration of scales of design disaster.

• Ecology and Resilient Infrastructure
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• v.3 no.4
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• pp.272-278
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• 2016

Porous pavements are recommended as a Low-Impact Development (LID) method which is a strategy to develop a water cycle as close to a natural state as possible, and to solve the urban impervious surface problems. Porous pavements can yield a solution if it provides a more permeable surface with extra space to contain extra water from building roofs. But there are few applications in Korea because of a lack of recognition and experience. Highway engineers are mainly concerned about the infiltration of water into pavement structures. They worry about the weakening of the asphalt mixture and subgrade, and freezing during the winter season due to the infiltration of water. Meanwhile, hydrological experts doubt the effects of the amount of water to control during the flooding season, and environmental experts prefer a non-point pollution treatment system established beside highway. In this study, from reviewing the history and the body of literature about porous pavements, conclusions regarding the most advanced technologies were made. First, traditional thickness designs can be used for porous pavement, no extra distresses was found by weakening and freezing during the winter season. Second, hydrological design can be made by controlling the thickness of the pavement and the outlet of water. Third, the treatment efficiency of non-point pollution of porous pavements is not worse than any other method. Importantly, it's a more eco-friendly solution because of its lower requirement for de-icing agents.

• Ecology and Resilient Infrastructure
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• v.3 no.4
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• pp.279-284
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• 2016

Mine tailings generated during mining activity often contain high concentrations of heavy metals, with pyrite-containing mine tailings in particular being a major cause of environmental problems in mining areas. Chemical cell technology, or fuel cell technology, can be applied to leach heavy metals in pyrite-containing mine tailings. As pyrite dissolves through spontaneous oxidation (i.e. galvanic oxidation) in the anode compartment of the cell, $Fe^{3+}$, sulfuric acid are generated. A decrease in pH due to the generation of sulfuric acid allows heavy metals to be leached from pyrite-containing mine tailings. In this study, pyrite was dissolved for 4 weeks at $23^{\circ}C$ in an acidic solution (pH 2) and in a galvanic reactor, which induces galvanic oxidation, and total Fe leached from pyrite and pH were compared in order to investigate if galvanic oxidation can facilitate pyrite oxidation. The change in the pyrite surface was analyzed using a scanning electron microscope (SEM). Comparing the total Fe leached from the pyrite, there were 2.9 times more dissolution of pyrite in the galvanic reactor than in the acidic solution, and thus pH was lower in the galvanic reactor than in the acidic solution. Through SEM analysis of the pyrite that reacted in the galvanic reactor, linear-shaped cracks were observed on the surface of the pyrite. The study results show that pyrite dissolution was facilitated through the galvanic oxidation in the galvanic reactor, and also implied that the galvanic oxidation can be one remediation option for pyrite-containing mine tailings.

• Ecology and Resilient Infrastructure
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• v.5 no.1
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• pp.25-34
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• 2018

This study presents prediction and historical analysis of the long-term bed elevation change in the Mankyung-gang River. The study area is a 25 km long reach including middle and lower courses of the Mankyung-gang River. HEC-RAS program was used for numerical predictions, and values of roughness coefficients were calibrated. Then, predictions were made in the two periods, seven years from 1986 to 1993 and twelve years from 1993 to 2005. Simulation results were compared with two sets of measured data for bed elevations. Four sediment transport formulas, namely MPM's, Toffaleti's, MPM-Toffaleti's, and Yang's formula, were tested. Simulation results showed that none of the four sediment transport formulas predicted the bed elevation change in the period of 1986 - 1993. This is related to the fact that dredging work was performed in the upstream reach in the period of 1986 - 1993, and sediment was deposited in this part severely later. However, it was found that MPM-Toffaleti's formula predicted properly the bed elevation change for the period of 1993 - 2005.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.2
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• pp.94-102
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• 1998

Temporal changes, density, calcimass, mode of occurrence, size-frequency histogram and survivorship curves were studied for the molluscan death assemblages on a macrotidal flat, Inchon, Korea. The living and death assemblages were compared on the basis of the taxonomic compositions and their numerical abundances. A total of 28 species (16 taxa in gastropods and 12 in bivalves) were identified. Most of the dead shells were the species inhabiting that intertidal mud flat. Species diversity was higher in gastropods than in bivalves. Seasonal variation of the calcimass was influenced by the mactrid bivalve, Mactra veneriformis. Shell-boring naticid gastropods preferred selecting the umbo areas of various valves. Size-frequency distribution and size-specific survivorship curves were analyzed for the dominant species. Survivorship curve of the tellinid bivalve, Morella rutila was convex-up in shape, which is congruent with the expected equilibrium condition but indicates higher mortality in winter. Whereas the survivorship curves of Mactra veneriformis and Reticunassa festiva were semi convex-up with dual modes, suggesting a disequilibrium due to the changes in recruitment and seasonal mortality. This study suggests that the dead shell assemblages may be useful in getting population information like live molluscan assemblages, if solved for several problems related to taphonomic processes.

• Research in Plant Disease
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• v.17 no.1
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• pp.90-94
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• 2011

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is a very serious disease in rice growing regions of the world. There are no effective ways of protecting rice from the disease. In this study, the bacteriophage (phage) mixtures infecting Xoo were investigated as biological control agent on BLB. The effects of pH, heat and ultraviolet on the stability of phages were investigated to check and increase the possibility of practical use in the field. Phages were rather stable between pH 5 and pH 10. The infectivity dropped sharply when the phages were incubated at $50^{\circ}C$ and more than 90% of the phages were inactivated after two minutes of ultraviolet treatment. The phages were stable for 7 days at the rice plant leaves, and the phages survived 10 times more than other treatments when mixed with skim milk. Although the skim milk increased the stability of the phages, the control efficacy was not effective. However, the phage mixtures reduced the occurrence of BLB when they were treated with Tecloftalam WP or Acibenzolar-S-methyl simultaneously. The results indicated that the Xoo phages could be used as an alternative control method to increase the control efficacy and reduce the use of agrochemicals.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.217-224
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• 2005

This study was aimed to analyze the long-term fluctuation of water quality and phytoplankton dynamics of Paldang reservoir in Korea and to assess the relationship between algal bloom patterns and hydrological, limnological data. Diatoms in Paldang reservoir occurred continuously through the year. Blue- green algae occurred during the summer season (from June to Sept.), and the highest count was observed in July. Occurrence pattern of green algae was similar to that of blue-green algae. The rest of algae contained a lot of Cryptomonas spp. whose concentration was high from May to Aug. Dominant algal genera (>>7,000 cells $mL^{-1}$) in Paldang reservoir were Aulacoseira, Cyclotella, Microcystis, and Cryptomonas spp. Microcystis and Anabaena occurred during the summer season. Many different green algal genera were found in Paldang reservoir but their abundances were very low. There were some significant correlations (r>0.3, p<0.05) between algal taxa and water quality; diatoms and water temperature, TP:blue-green algae and water temperature, pH, DO saturation, COD, TP; green algae and water temperature, pH, DO saturation, COD, SS, TP. Furthermore, algal genera and water quality was significantly correlated (r>0.3, p<0.05) ; Aulacoseira and TN, TP; Anabaena and water temperature, DO saturation, COD, TP : Microcystisand water temperature, pH, DO saturation, TP; Coelastrum and COD, SS; Scenedesmus and water temperature, COD, TN, TP; Cryptomonas and DO saturation, TN. In Paldang reservoir, the water temperature had relatively big effect on blue-green algal bloom that was also dependant upon its hydrologic condition.

• Korean Journal of Ecology and Environment
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• v.48 no.4
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• pp.263-271
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• 2015

To evaluate the relationship between dynamics of cyanobacteria and odorous compounds, a monthly monitoring of water quality and phytoplankton were conducted at the three serial lakes (Lake Ui-am, Lake Cheong-pyeong and Lake Pal-dang) in the North Han River for 11 times from May 2014 to March 2015. In the three serial lakes, phytoplankton communities showed that seasonal changes in Bacillariophyceae-Cyanophyceae-Bacillariophyceae. Anabaena and Pseudanabaena were dominant species in August and September 2014. At the same time the odors (Geosmin, 2-MIB) were also detected with high concentration. Relationship between environmental factors and cyanobacterial abundance showed a significant correlation with Anabaena circinalis and geosmin (r=0.983, p<0.01). In the case of Pseudanabaena limnetica showed a significant correlation of total nitrogen (r=0.685, p<0.01) and NO3-N (r=0.723, p<0.01). In addition, similarly Pseudanabaena limnetica and 2-MIB (r=0.717, p<0.01) was high. The odorous compounds appeared in the North Han River water were considered to be a direct relationship with cyanobacteria.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.404-406
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• 2009

This study note wished to introduce special-purpose ship for algae removal that is developed by core technology of our country. The ship is consisted of main frame and adjuvant that can attach and detach as cross (+) shape of a character. The characteristics of ship are super light weight and low draft. That is consisted of four devices as suction, collection, filtration and recovering units. Among these, filtration used screen filter (mesh size 30 ${\mu}m$). Also, can separate and remove water and algae by compression air participle notion. Percentage of moisture content of concentrated algal particle was 85%. Water parted with algae finally is exhausted to water area. Removal efficiency that compare by chlorophyll-$\alpha$ concentration was about 57% (inflow: 83.2 ${\mu}g\;L^{-1}$, outflow: 35.8 $[\mu}g\;L^{-1}$) without physical and chemical pretreatment. Forward, need to achieve effect test in various conditions (algal biomass, flow etc.) for efficiency and technological elevation of exclusion device. We wished to contribute in presuppression system construction of massive algal development that manage blue-green algae occurrence area effectively, and prevents spread as lower part of reservoir.