• Applied Microscopy
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• v.38 no.4
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• pp.307-314
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• 2008

Hydrophytes such as Spirodela polyrhiza form dormant turions to withstand cold winters. The turion is an anatomically distinct structure from which a vegetative frond arises later during germination. The turions sink to the bottom of the pond when temperatures drop and remain there throughout the winter. In the spring, they float to the surface and germinate into a new frond from the turion primordium. Unlike fronds, turions are known to possess small aerenchyma, starch grains, and relatively dense cytoplasm. These features allow the turions to survive the cold winter season at the bottom of the pond. Spirodela polyrhiza has been investigated previously to a great extent, especially in its physiological, biochemical and ecological attributes. However, a little is known about the structural features of the frond and turion during turion development. Thus, the aim of the present study was to reveal the structural characteristics of the frond and turion with regard to tissue differentiation, aerenchyma development, starch distribution, and ultrastructure, with the use of electron microscopy. A moderate degree of mesophyll tissue differentiation was found in the frond, whereas the turion did not exhibit such differentiation. Within the frond tissue, approximately $37{\sim}45%$ of the cellular volume was occupied by a large aerenchyma, but only $9{\sim}15%$ was taken up by the aerenchyma in the turion. The turion cells, especially those of the turion primordium, were derived from frond cells, and contained cytoplasm. Their cytoplasm was densely packed with plastids, mitochondria, endoplasmic reticulum, Golgi bodies, and microtubules. Plasmodesmata were also well developed within these cells. The most striking feature observed was the distribution of starch grains within the plastids of turion cells. Before the turion sank to the bottom of the pond, a considerable amount of starch accumulated in the plastid stroma. The starch grains dissolved when temperatures rose in the spring, and this promptly provided the nutrients which the primordium needed for turion germination. The turion therefore, was an appropriate dormant structure for free-floating, reduced hydrophytes like Spirodela polyhriza due to its small aerenchyma and large starch grains that aided in the purpose of sinking below the surface of the water to survive cold winters. The new fronds that arose from such turions grew rapidly in the spring, beginning the new life cycle.

• Journal of the Korean Regional Science Association
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• v.37 no.4
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• pp.61-74
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• 2021

The objective of this study was to evaluate the community's capacity and hindrance factors affecting the community's activities by exploring the process of restoring the community's environmental pollution. This study examined the community activities related to the restoration of pollution that occurred at the former Janghang smelter in Seocheon-gun. The results of this study showed that leaders, cooperative resources, and the media were elements positively influencing the recovery of the community. The starting point that became the driving force for community activities was the presence of a leader who had a small stake in it. Moreover, it required cooperation such as the continuous interest of local active groups and residents to continue this effort. Above all, the media publicized the incident and amplified the activities of members. Meanwhile, there were various conflicts hindering the activities of local communities in the process of restoring the pollution such as the internal conflicts of community groups, conflicts between residents and active groups, and conflicts with the government. The behaviors that appeared in the process of restoring the pollution revealed a form of united governance. Moreover, they changed from an initial "supportive" character to "resistant" and "defensive" activities. Later, it was transformed into "subjective" and "creative" activities.

• Korean Journal of Environmental Agriculture
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• v.30 no.2
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• pp.144-152
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• 2011

BACKGROUND: Eutrophication occurs occasionally in flood control reservoirs around Juam lake in summer and early autumn. Lakeside macrophyte which is one of internal pollutants effects on water quality when it is submerged during water surface is rising after rainy season. METHODS AND RESULTS: To improve water the quality of water from water supply source and to establish the management plan of submerged plants in flood control reservoirs around Juam Lake, the removal and release velocities of nutrients by submerged plants in site 1 and 2 were investigated. Removal or release velocity constant (K) of COD by Carex dimorpholepis Steud in column was 0.07~0.18 $day^{-1}$ at 0~4 days after flooding, -0.23~-0.17 $day^{-1}$ at 5~19 days after flooding and -0.28~0.03 $day^{-1}$ at 20~33 days after flooding. Removal or release velocity constant (K) of T-N by Carex dimorpholepis Steud was 0.02 $day^{-1}$ at 0~4(8) days after flooding, -0.13~-0.10 $day^{-1}$ at 5(9)~33 days after flooding in column. Removal or release velocity constant (K) of T-P by Carex dimorpholepis Steud was 0.05~0.06 $day^{-1}$ at 0~4 days after flooding, -0.14~-0.09 $day^{-1}$ at 5~33 days after flooding. Release velocity constant (K) of nutrients by Miscanthus sacchariflorus Benth was lower than that by Carex dimorpholepis Steud. In site 1, the amount of nutrients release by Carex dimorpholepis Steud was 6,719 kg/month/area for COD, 2,397 kg/month/area for T-N and 466 kg/month/area for T-P. The amounts of nutrients release by Carex dimorpholepis Steud were higher than those by Miscanthus sacchariflorus Benth in both sites. CONCLUSION(s): The results of this study suggest that COD, T-N and T-P in water quality of Juam lake were strongly influenced by submerged plants in flood control reservoirs.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.4
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• pp.349-358
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• 2007

In order to understand biogeochemical cycles of organic carbon in the permeable intertidal sandy sediments of the Nakdong estuary, we estimated the organic carbon production and consumption rates both in situ and in the laboratory. The Chl-a content of the sediment and the nutrient concentrations in below surface pore water in the sandy sediment were lower than in the muddy sediment. The sediment oxygen consumption rates were relatively high, especially when compared with rates reported from other coastal muddy sediments with higher organic carbon contents. This implied that both the organic carbon degradation and material transport in the sandy sediment were enhanced by advection-related process. The simple mass balance estimation of organic carbon fluxes showed that the major sources of carbon in the sediment would originate from benthic microalgae and detrital organic carbon derived from salt marsh. The daily natural biocatalzed filtration, extrapolated from filtration rates and the total area of the Nakdong estuary, was one order higher than the maximum capability of sewage plants in Busan metropolitan city. This implies that the sandy sediment contributes greatly to biogeochemical purification in the area, and is important for the re-distribution of materials in the coastal environment.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.10
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• pp.1013-1020
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• 2008

To evaluate the pollutant removal efficiency and clarify the cause of low removal efficiency of the wetland, temporal and spacial distributions of water quality were investigated at 16 sites in the Sihwa constructed wetland. The removal efficiency showed a tendency to decrease since the construction of the wetland, except for TN. In addition, the efficiency was largely varied with season, especially BOD and TP. No removal efficiency of BOD was observed in April and July when algal bloom was occurred in lower part open water of the wetland. On the other hand, TP showed no removal efficiency from April to August showing -291% of removal efficiency in August. From the horizontal distribution in closed water regions, SS concentration for the central area was significantly higher than for left and right areas(p = 0.013, center > left > right areas). From the results of this study, we infer that anaerobic condition due to the excessive accumulation of organic matters and lack of uniformity of water flow distribution are major factors of the low removal efficiency of the wetland.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.13 no.1
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• pp.82-92
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• 2010

Removal rates of NO3-N and TN in a free water surface wetland system during emergent plant growing season and non-growing were investigated. The system was established on floodplain in the down reach of the Gwangju Stream in 2008. Its dimensions were 46 meters in length and 5 meters in width. Typha angustifloria L. growing in pots about two years were planted on the half area of the system and Zizania latifolia Turcz on the other half. Water of the stream was funneled into it by gravity flow and its effluent was discharged back into it. Volumes and water quality of inflow and outflow were analyzed from October 2008 to September 2009. Inflow into the system averaged approximately 715 $m^3$/day and hydraulic residence time was about 1.5 hr. Average influent and effluent $NO_3$-N concentration was 3.37 and 2.74 mg/L, respectively and $NO_3$-N retention amounted to 18.7%. Influent and effluent TN concentration averaged 4.67 and 3.69 mg/L, respectively and TN abatement reached to 20.9%. $NO_3$-N removal rate (%) during plant growing season ($22.67{\pm}3.70$, mean ${\pm}$ standard error) was significantly high (p<0.001) when compared with that during plant non-growing one ($15.02{\pm}3.23$). TN abatement rate (%) during plant growing season ($27.42{\pm}5.98$) was also significantly high (p<0.001) when compared with that during plant non-growing one ($13.66{\pm}3.08$).

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.6
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• pp.153-163
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• 2009

This study was carried out to offer ecological restoration plan of local streams by analyzing the vegetation and flora around four local streams (Pungchoncheon, Namchangcheon, Ganggicheon, Woncheoncheon) in Namwon. Flora and vegetation investigation was done at April 2007 to August 2007, and June 2009. The 194 of vascular plants were identified which contain 53 families, 143 genera, 194 species. The Family frequencies arranged by the order of Family Compositae (14.4%), Family Gramineae (13.4%) Family Leguminosae (6.7%) and Family Polygonaceae (5.2%). The naturalized plants were listed as 33 species, and their naturalization ratio and urban index were found to be 17.0%, and 12.2%, respectively. In this study a total of 21 relev$\acute{e}$s collected and analyzed. 6 plant communities are differentiated : Riverine softwood forests (Phragmites japonica-Salix gracilistyla community), Perennial herb vegetations on lotic water zone (Phragmites japonica community, Phalaris arundinacea community), Perennial herb vegetations on lentic water zone (Persicaria thunbergii-Typha orientalis community, Phragmites communis community), Annual or biennial vegetations on waterside (Persicaria thunbergii community). Species showing the higer value in the plant communities were Persicaria thunbergii, Phragmites japonica, Artemisia princeps, Humulus scandens, Bidens frondosa, Oenanthe javanica, Agropyron tsukusinense var. transiens, Stellaria aquatica, and Lactuca indica var. laciniata.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.6
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• pp.71-85
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• 2011

In Okdong coal mine abandoned area, every year large amount of mine wastes have been swept away due to heavy rains in summer. Because pH of coal-mine waste is in the early 4, plant naturally does not grow there due to unfavorable condition for growing plant. This study had an experiment to grow plant for 6 months using Mycorrhizae which can be adapted well in acid soil. As a result of Experiment, In the infected experiment pot, 90% of the plants survived but in case of uninfected experiment pot, only 25% were alive. From Growth Experiment, it appeared that average stem length increase (cm/month), average fresh weight increase ($g^{fw}/month$), average dry weight increase ($g^{dw}/month$) were increased by 60%, 21%, 31% respectively. Especially, Mycorrhizae plays an important role in providing nutrients and water when seeding are established. Mycorrhizae prevents death caused by lack of nutrients and water and helps growth and development of plant when seeding are established in the early stage. This study proved that Mycorrhizae is comparatively effective in plant growth and prevention of erosion in coal-mine abandoned area.

• Korean Journal of Environmental Agriculture
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• v.16 no.3
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• pp.207-211
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• 1997

Laboratory experiments were conducted to the potential ability of bioremediation with bentazon such as determining the absorption, translocation, and metabolism of $^{14}C-Bentazon$ in minari after foliar applications. The absorption and translocation of $^{14}C-bentazon$ were compared when applied to foliar of minari. In foliar applications, 21% was observed in treated leaves, 66% remained in water extracts of leaf surfaces, and 13% was found in the epicuticular wax layer after 2d. Translocation of the herbicide from treated leaves to roots was very low(79 to 9%). Analysis of methanol-soluble extracts of $^{14}C$ indicated that more than 60% of the foliarapplied herbicide was metabolized in all plant sections after 2d. However, 77% or more of the bentazon was degraded in roots and shoots 2d after root absorption. The major metabolite in these experiments was an unknown compound that was less polar than bentazon and 6- and 8-hydroxy bentazon.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.4
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• pp.283-288
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• 2013

To evaluate the ability of the submerged plant, Ceratophyllum demersum's (C. demersum) to remove nutrients and to inhibit growth of cyanobacteria, a total of 6 mesocosms were conducted in a batch reactor for 9 days. From the 84 hr of the experiment, C. demersum was stabilized and showed daily cycle trends according to changes in pH and DO levels. The concentration of nutrients, $NH_3{^+}$, $NO_3{^-}$ and $PO_4{^3}$ continuously decreased until 9 days of the experiment, with the rapid decrease in nutrient concentration for the first 24 hours. High correlation coefficient ($r^2{\geq}0.96$, p<0.001) between the amount of C. demersum's biomass per unit area and the nutrients removal level were derived, and greater C. demersum's biomass per unit area showed higher removal efficiency of nutrients. However, there were differences in the C. demersum's activity level between batch reactors with higher and similar density of the C. demersum, but nonetheless water purification effect appears to have a significant influence due to attached algae and microorganisms. The growth rate of harmful cyanobacteria, Microcystis aeruginosa (M. aeruginosa) with C. demersum's density of 2,500 g $fw/m^2$ (100% of cover degree) was 0.31 /day, compared to the growth rate of 0.47 /day for the control group (0% of cover degree). In terms of number of cells, the control group had 1.7 times higher number of cells than the experimental group, proving that C. demersum has the ability to inhibit the growth of harmful cyanobacteria.