• Journal of Microbiology and Biotechnology
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• v.17 no.2
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• pp.253-261
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• 2007

Molecular and cultivation techniques were used to characterize the bacterial communities of biobead reactor biofilms in a sewage treatment plant to which an Aerated Up-Flow Biobead process was applied. With this biobead process, the monthly average values of various chemical parameters in the effluent were generally kept under the regulation limits of the effluent quality of the sewage treatment plant during the operation period. Most probable number (MPN) analysis revealed that the population of denitrifying bacteria was abundant in the biobead #1 reactor, denitrifying and nitrifying bacteria coexisted in the biobead #2 reactor, and nitrifying bacteria prevailed over denitrifying bacteria in the biobead #3 reactor. The results of the MPN test suggested that the biobead #2 reactor was a transition zone leading to acclimated nitrifying biofilms in the biobead #3 reactor. Phylogenetic analysis of 16S rDNA sequences cloned from biofilms showed that the biobead #1 reactor, which received a high organic loading rate, had much diverse microorganisms, whereas the biobead #2 and #3 reactors were dominated by the members of Proteobacteria. DGGE analysis with the ammonia monooxygenase (amoA) gene supported the observation from the MPN test that the biofilms of September were fully developed and specialized for nitrification in the biobead reactor #3. All of the DNA sequences of the amoA DGGE bands were very similar to the sequence of the amoA gene of Nitrosomonas species, the presence of which is typical in the biological aerated filters. The results of this study showed that organic and inorganic nutrients were efficiently removed by both denitrifying microbial populations in the anaerobic tank and heterotrophic and nitrifying bacterial biofilms well-formed in the three functional biobead reactors in the Aerated Up-Flow Biobead process.

• Journal of Korean society of Dental Hygiene
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• v.4 no.1
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• pp.31-48
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• 2004

Dental caries taking place with milk teeth affects eruption of permanent teeth adversely, and thus, it is very important to prevent dental caries from taking place with a child in maintaining his/her physical, mental and emotional health. In this study as conducted to obtain basic data to be required for development of a program for letting preschool children form a habitual life for oral health and right dietary life, a total 172 children aged 5 years and 6 years were selected from children who lived in Hwasung-si, Kyunggi-do and attended preschools (childrens houses) located there with the consent of their guardians. Then, the weight length index (WLI) and blood components of each child were analyzed, and each relation between the weight length index (WLI) and dental caries of milk teeth and between blood components and dental caries of milk teeth was comparatively examined, and thereby, the following results were obtained. When the dmf rate of each group according to the obesity was examined, it was found to be 87.50% in the under-weight group, 71.20% in the normal weight group and 83.87% in the overweight group. And when the dmft rate of each group was examined, it was found to be 48.43% in the under-weight group, 37.10% in the normal weight group and 47.17% in the overweight group. Also, when the dmft index of each group was examined, it was found to be 3.9 in the under-weight group, 3.0 in the normal weight group and 3.8 in the overweight group. That is to say, the under-weight group and the overweight group having an abnormal weight were found to be higher in all of the dmf rate, the dmft rate and the dmft index than the normal weight group. It could be, therefore, known that normal weight should be maintained in order to prevent dental caries of milk teeth. And, it is thought that a right dietary life habit ensuring intake of balanced nutrients should be formed for maintenance of a normal weight. As a result of examining the relation between nutrient components in blood and dental caries of milk teeth, in the case of children with no dental caries, inorganic nutrient components of blood had a tendency to be a little higher, but no statistical significance was observed therein. Meanwhile, it was found that there was a relation between blood type and the dmft index.

• Korean Journal of Environmental Agriculture
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• v.7 no.1
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• pp.21-25
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• 1988

A pot experiment was conducted to find out the effect of arsenic(As) added to soil on the number of roots, root diameter, root length and root tissue of the rice plant. The results obtained were as follows: Higher As levels in soil remarkably reduced not only the number of roots, root length and root diameter, but also the diameter of the central cylinder, the route of the water and inor ganic nutrients of the roots. When arsenic was treated in soil, abnormal cells in the cortex of rice root were developed and considerably increased with higher As levels in the soil. These were only observed in the middle and upper parts of root segments except root tips and they looked like rice roots without epidermis in shape. Therefore, the occurrence of the abnormal cells in the root was attributed to high arsenic accumulation in the root. Its mechanism is not clear. However, it is assumed that the abnormal cells had occurred to compensate for lower amount of water and inorganic nutrient absorption by the injured rice root or self-defense against the penetration of arsenic within the rice root.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.210-224
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• 2003

Sulfate reduction is a microbiological process which occurs ubiquitously in anaerobic marine environment. Sulfate reducing bacteria play a significant role in anaerobic decomposition of organic matter and regeneration of inorganic nutrients which supports the primary production in the water column (i.e., benthic-pelagic coupling) and, in special case, could be responsible for the harmful algal bloom in the coastal marine environment. Summary of the sulfate reduction rates reported in various marine sedimentary environments revealed that supply of organic substrates and presence of various electron acceptors (i.e., $O_2$, NO$_{3}$$^{[-10]}$ , Fe(III) and Mn(IV), etc.) for other aerobic and anaerobic respiration directly affect the sulfate reduction rate and relative significance of sulfate reduction in organic matter mineralization. Significance of temperature, macrophytes and bioturbation is discussed as factors controlling supply of organic substrates and distribution of electron acceptors. Finally, we suggest studies on the anaerobic microbiological processes associated with biogeochemical element cycles in the coastal environments of Korea where massive operation of organic enriched fish cage farm, frequent occurrence of toxic algal bloom and hypoxia and conservation of tidal flat are of major environmental issues.

• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.161-171
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• 2003

The present study evaluated water quality variation, limiting nutrient, and sediment of a shallow eutrophic lake (Lake Ilgam) in the metropolitan area from 2000 to 2002. According to annual mean chl.a ($77.2{\pm}36.6\;{\mu}g/l) and TP ($66.6{\pm}20.5\;{\mu}g/l) concentration and trophic state index (>60), Lake llgam was in very eutrophic status. Both inorganic nitrogen ($NH_3-N$ and $NH_3-N$) and phosphorus (SRP) concentrations in the water column increased during winter and spring, but decreased during summer followed by the phytoplankton development. Evidence for phosphorus and nitrogen as being the potential limiting nutrients for phytoplankton growth was supported by the ratio of DIN/DIP (by mass) (${\sim}$835.8), TSI derivations analysis, and algal growth potential bioassay. Based on the results of TSI derivations, strong nutrient limitation by both N and P occurred from September to November when P content in sediment (114.6 mg P/kg) was relatively low compared with the summer. Sediment contained a large amount of nitrogen (TKN: 4,452${\pm}$283.0mg N/kg dry sediment). Phosphorus content in sediment (TP: 313${\pm}$155 mg P/kg) was relatively low with temporal change. P release rate (0.29${\pm}$0.02 mg $m^{-2}$ $day^{-1}$) was high under the aerobic condition at pH 9. These results indicate that the sediment could play an important role as a source of a limiting nutrient, and temporal change of P content in the sediment is closely related with water quality, especially algal biomass change in Lake llgam.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.3
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• pp.145-152
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• 2000

The total acreage of 4,894ha of upland soils in Yeongyang area, the main crop cultivated were red-pepper. They were distributed mainly on local valleys and alluvial fans(54.9%), about 61.2% had 7~15% slopes, and about 73.2% had fine loamy family in soil texture. the soils were classified into Ochrepts(73.7%). Udalfs(16.9%), Fluvents(6.2%) and Psamments(3.2%) etc. The upland soils with 100~250m in altitude and "moderately well drained" had higher contents in inorganic nutrients. The red-pepper Produced in the high altitude(>400m) were lower in quality and yields, while the content of sugar and yields of pepper produced in fine loamy textured soils were higher than other soil textures. The yields of red-pepper produced in the "moderately well drained" soils which had better water supply capacity were higher than "well drained" soils.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.74-80
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• 2019

In this study, pyrolyzed oyster shells at a low temperature ($350^{\circ}C$) were applied for a mesocosm experiment to confirm resulting changes in the properties of sediment. After creating a covering of oyster shells, an increase in ORP and decrease in ammonia in the overlying water was observed in an experimental case. The decrease of TOC in this experiment was due to the dilution of organic matter due to the addition of inorganic matter (pyrolyzed oyster shells). The decrease in the concentration of AVS was observed due to the adsorption of AVS by the surface of the oyster shells. From the results obtained in this experiment, it has been concluded that pyrolyzed oyster shells at a low temperature can be used for remediation of polluted sediment.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.340-354
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• 2021

The aim of this study was to investigate the spatial and temporal distribution of phytoplankton biomass and community composition in Jinhae Bay on the southern coast of Korea. Phytoplankton pigment analysis was conducted using ultra performance liquid chromatography (UPLC) were conducted from April to December 2019 at seven stations. Temperature, salinity, and dissolved oxygen (DO) and inorganic nutrients (dissolved nitrogen, dissolved phosphorus, and orthosilicic acid) were measured to investigate the environmental factors associated with the structure of phytoplankton community. Phytoplankton biomass (Chl-a) was the highest in July (mean 15.4±4.3 ㎍/L) and the lowest in December (mean 3.5±0.6 ㎍/L). Fucoxanthin was the most abundant carotenoid and showed a similar variation pattern to Chl-a, peridinin, and Chl-b. Phytoplankton community composition analysis showed that diatoms were a predominant group with an average abundance of 70 % whereas chlorophytes, cryptophytes, and dinoflagellates often appeared with lower averages. Further, the dominance of diatoms was closely correlated with water temperature and N:P ratio, which might be influenced by high temperatures in the summer and nutrient loading from the land. Additionally, freshwater and nutrient input by rainfall was estimated to be the most important environmental factor. Hence, the spatial and temporal variations in the composition of phytoplankton pigments and phytoplankton community were correlated with physicochemical and environmental parameters.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.4
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• pp.308-319
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• 2008

Temporal variations in plankton assemblages and environmental factors in Asan Bay and their relationships were examined with the data collected from February till early June, 2005. Seawater temperatures showed typical pattern of temporal change observed in temperate waters. Salinity variation was minor. Phytoplankton biomass showed two peaks, one in February only in the inner part of the bay and the other in May in the whole bay. Phytoplankton succession was clearly shown with the increase of seawater temperatures. Diatom (Bacillariophyceae) dominated in February, diatom and cryptomonads (Cryptophyceae) prevailed in May, and dinoflagellates (Dinophyceae) was most abundant in June. Spring bloom in Asan Bay occurred about one month earlier than those observed in temperate seas. Among the inorganic nutrients (N, P and Si), only silicate concentration showed a significant negative correlation with phytoplankton biomass, indicating the sink of this nutrient in the bay to be the uptake by phytoplankton. Nitrate concentration seemed to be a limiting factor in this bay during the study period. Mesozooplankton abundances showed a significant positive correlation with seawater temperatures and a significant negative correlation with phytoplankton biomass. Increase of mesozooplankton abundance followed phytoplankton increase with the time lag of about two months. This increase of zooplankton seemed to be the result of increased seawater temperatures and food.

• Korean Journal of Environmental Biology
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• v.41 no.4
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• pp.706-711
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• 2023

At Pyropia farms, organic acid treatments have enhanced productivity and quality by removing pest algae (such as Ulva spp. and diatoms) and reducing the occurrence of diseases. Ulva spp. attaches to the Pyropia nets competing for inorganic nutrients & space and diminishing productivity. Additionally, the presence of attached contaminants (such as diatoms and middy particles) on the Pyropia nets negatively affects the quality of Pyropia. This study investigated the effects of removing Ulva linza and washing the Pyropia yezoensis nets using an activating treatment agent (organic acid and highly saline solution) with an air bubble device. The results of measuring the dead cell ratios after treatment under different conditions showed that the dead cell ratio of U. linza did not significantly increase when the air bubble device combined the activating treatment agent with the activating treatment agent alone. When washing the P. yezoensis nets, the air bubble device was about 19-37% more effective than the activating treatment agent alone. The findings of this study suggest that the air bubble device enhances the efficacy of the activating treatment agent, resulting in the effective cleaning of the Pyropia nets.