• Journal of radiological science and technology
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• v.27 no.2
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• pp.29-33
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• 2004

Until early 1980s we have lived without thinking that radon ruins our health. But, scientists knew truth that radon radioactive danger is bedeviling on indoor that we live for a long time. Specially, interest about effect that get in danger and injury for Radon and human body is inactive in our country. Recently, with awareness for Radon contamination, We inform about importance and danger of Radon in some station of the Seoul subway, indoor air of school facilities and We had interest with measure and manages. Usually, Radon gas emitted in base of building enters into indoor through building floor split windage back among radon or indoor air of radon daughter nucleus contamination is increased. Therefore, indoor radon concentration rises as there are a lot of windages between number pipe of top and bottom and base that enter crack from estrangement of the done building floor, underground to indoor. Thus, Radon enters into indoor through architecture resources water as well as, kitchen natural gas for choice etc., but more than about 85% from earth's crust emit. Danger and injury of health by Radon and Radon daughter nucleus that is indicated for cause of lung cancer incerases content of uranium of soil rises specially from inside pit of High area and a mine, cave, hermetical space with house. Safe sub-officer of radon concentration can not know and danger always exists large or small during. So, Important thing reduces danger of lung cancer by lowering concentration of Radon within house and building. Therefore, is thought that need general house Radon concentration measurement, measured Radon concentration monthly using Sintillator radon monitor. Study finding appeared high all underground market 1 year than the ground, and the winter appeared high than the summer. Specially, month that pass over 4pCi in house that United States Environmental Protection Agency advises appeared in underground, and appeared and know Radon exposure gravity by 4 months during 12 months. Therefore, Thinking that establishment and regulation of norm and preparation of reduction countermeasure about Radon are pressing feels, and inform result that measure Radon concentration.

• Economic and Environmental Geology
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• v.38 no.4 s.173
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• pp.435-450
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• 2005

The purpose of the study is to analyze the hydrogeochemical characteristics by multivariate statistical method, to interpret the hydrogeochemical processes for the new variables calculated from principal components analysis (PCA), and to infer the groundwater flow and circulation mechanism by applying the geostatistical methods for each element and principal component. Chloride and nitrate are the most influencing components for groundwater quality, and the contents of $NO_3$ increased by the input of agricultural activities show the largest variation. The results of PCA, a multivariate statistical method, show that the first three principal components explain $73.9\%$ of the total variance. PC1 indicates the increase of dissolved ions, PC2 is related with the dissolution of carbonate minerals and nitrate contamination, and PC3 shows the effect of cation exchange process and silicate mineral dissolution. From the results of experimental semivariogram, the components of groundwater are divided into two groups: one group includes electrical conductivity (EC), Cl, Na, and $NO_3$, and the other includes $HCO_3,\;SiO_2,$ Ca, and Sr. The results for spatial distribution of groundwater components showed that EC, Cl, and Na increased with approaching the coastal line and nitrate has close relationship with the presence of agricultural land. These components are also correlated with the topographic features reflecting the groundwater recharge effect. The kriging analysis by using principal components shows that PC 1 has the different spatial distribution of Cl, Na, and EC, possibly due to the influence of pH, Ca, Sr, and $HCO_3$ for PC1. It was considered that the linear anomaly zone of PC2 in western area was caused by the dissolution of carbonate mineral. Consequently, the application of multivariate and geostatistical methods for groundwater in the study area is very useful for determining the quantitative analysis of water quality data and the characteristics of spatial distribution.

• Journal of agriculture & life science
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• v.46 no.3
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• pp.119-127
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• 2012

For the promotion of the evaporative cooling efficiency of hot air in greenhouse in summer, a fog sprayer consisted of a high volume spraying two-fluid nozzle with turbo fan and a blowing fan was set up at 2.2 m height from bottom of small glass greenhouse and tested to estimate the possibility of the greenhouse cooling. The mean droplet size and the volume sprayed by one of fog sprayer were $29{\mu}m$ and $160m{\ell}/min$. All the droplets sprayed and blown by the fog sprayer were evaporated within 2 m radius. The result from the cooling test that two sprayers set up in glass greenhouse of plane area $228m^2$ was represented lower cooling effect that the temperature and relative humidity of inside air of greenhouse were $28.8^{\circ}C$ and 87.5% when those of outside air of greenhouse were $30.2^{\circ}C$ and 81.2%. Through investigation of literatures and results of the cooling test, it was estimated that the water spraying rate of evaporative cooling of single span greenhouse with 50% light curtain and with air change rate of 1 volume/min was $10m{\ell}/min/m^2$ so that the inside air temperature may cool down $2{\sim}3^{\circ}C$ on the basis of $35^{\circ}C$ atmospheric temperature in summer of south korean area.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.6
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• pp.669-676
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• 2017

To understand the relationship between environmental factors and phytoplankton community structures and why early outbreaks of Cochlodinium polykrikoides occur in the inner bay of Korea, short-term investigations were conducted at 17 stations in the eastern part of the South Sea of Korea, with sessions every two weeks from July 7 to August 24, 2016. The water temperature increased from $22.3^{\circ}C$ in the first survey to $28.4^{\circ}C$ in the fourth survey, which was a rise of about $6.01^{\circ}C$. Salinity was relatively high at Stns. 8 13 in the inner bay. In the first survey, rainfall of about 150 mm was observed, so nutrients were supplied at a high level and a high concentrate of Chl. a was observed. Cryptophyta (Crpytomonas spp.) represented 58.3 % of the community, followed by Bacillariophyta at 33.8 %. In particular, at Stn. 5, Dinophyta Prorocentrum spp. accounted for a very high percentage, 32.2 %. In the second survey, low phytoplankton populations were observed, and Bacillariophyta (Chaetoceros spp.) accounted for 61.0 %. At Stn. 4, Skeletonema spp. showed high populations but did not appear at other stations even at a low density. In the third and fourth surveys, phytoplankton populations were very low. Bacillariophyta represented 78.0 % in the third study and 73.3 % in the fourth. Interestingly, although the appearance of C. polykrikoides was investigated at the beginning of the red tide in the coastal area, they were not observed inshore, implying that the likelihood of inflow by the germination of resting cysts was low for the inner bay during this study period. In addition, environmental characteristics such as salinity and nutrient presence were significantly different between sampling stations due to the existence of a semi-closed bay in the southern sea, resulting in dominant phytoplankton species and community composition differing in these short-term investigations.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.3
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• pp.193-204
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• 2000

In order to get some basic data on environmental friendly function by Korean organic farming, the chemical characteristics of soil were determined on 100 farm cultivating site in Paldang watershed area of Great Seoul. The EC and content of $NO_3-N$ and Av. $P_2O_5$ in topsoil(0~30cm) showed $2.30dS\;m^{-1}$, $82mg\;kg^{-1}$, $918mg\;kg^{-1}$ in the soil cultivated chinese cabbage. $2.29dS\;m^{-1}$, $86mg\;kg^{-1}$, $954mg\;kg^{-1}$ in the soil of lettuce, $1.83dS\;m^{-1}$, $66mg\;kg^{-1}$, $1114mg\;kg^{-1}$ in the soil of crown daisy. These salt accumulation(EC) and the high concentration of mineral content in topsoil such as nitrate and phosphate showed the soils of organic farming were contaminated by practice of organic farming for the maintenance strategy of soil fertility. The $NO_3-N$ and Av. $P_2O_5$ in the subsoil(30~60cm) showed $75mg\;kg^{-1}$ and $641mg\;kg^{-1}$, $72mg\;kg^{-1}$ and $466mg\;kg^{-1}$, $42mg\;kg^{-1}$ and $873mg\;kg^{-1}$ in soil cultivated chinese cabbage, lettuce and crown daisy respectively. It indicates eventually the high concentration of nitrate and phosphate in topsoil caused penetration to subsoil, and the high concentration of mineral contents in subsoil indicate the potential risk of leaching of ground water by Korean organic farming. The positive correlation at 1% between EC and $NO_3-N$, $K_2O$, T-C, $P_2O_5$ and T-N show the salt accumulation in the both soil depth of Korean organic farming were caused by minerals such as $NO_3-N$, $K_2O$, T-C, $P_2O_5$ and T-N by overuse of organic fertilizer.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.2
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• pp.118-130
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• 2007

The steep-sloped agricultural land was severely damaged by rainfall events during July and August every year. The objective of this study was to investigate an effects of intensive rainfall to the soil properties of the steep-sloped agricultural land. Survey sites including the Sacheon myeon area were located in Gangneung, those were severely damaged from a forest fire in April 2000. Surveys were taken at these sites after two years of forest fire and severe rainfall events in August 2002, which included an event that poured with 870 mm of rainfall in a day. After this storm, soil erosion, burying, and flooding were observed. Severe soil loss was found at lower soil-depths, greater slopes, longer slope lengths, and concave landscapes. Soil loss and land slides were often found at areas with having a coarser textures, higher bulk densities, lower water holding capacity, and lower rates of soil aggregation. Crop growth stagnation was found at the site of crop restoration because of low soil fertility and poor drainage caused by the abrupt textural changes. In conclusion, it is necessary to manage the steep-slope agricultural land based on environmental impact assessment data of macro morphological and physical characteristics by intensive rainfall.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.594-604
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• 2021

To evaluate the causes of beach erosion in Sinji-Myeongsasimni Beach, external forces, such as tides, tidal currents, and waves, were observed seasonally from March 2019 to March 2020, and the surface sediments were analyzed for this period. In addition, the shoreline positions and beach elevations were regularly surveyed with a VRS GPS and fixed-wing drone. From these field data, the speed of the tidal currents was noted to be insufficient, but the waves were observed to af ect the deformation of the beach. As the beach is open to the southern direction, waves of heights over 1 m were received in the S-SE direction during the spring, summer, and fall seasons. Large waves with heights over 2 m were observed during typhoons in summer and fall. Because of the absence of typhoons for the previous two years from July 2018, the beach area over datum level (DL) as of July 2018 was greater by 30,138m² compared with that of March 2019, and the beach area as of March 2020 decreased by 61,210m² compared with that of March 2019 because of four typhoon attacks after July 2018. The beach volume as of March 2019 decreased by 5.4% compared with that of July 2018 owing to two typhoons, and the beach volume as of September 2019 decreased by 7.3% because of two typhoons during the observation year. However, the volume recovered slightly by about 3% during fall and winter, when there were no high waves. According to the sediment transport vectors by GSTA, the sediments were weakly influxed from small streams located at the center of the beach; the movement vectors were not noticeable at the west beach site, but the westward sediment transport under the water and seaward vectors from the foreshore beach were prominently observed at the east beach site. These patterns of westward sediment vectors could be explained by the angle between the annual mean incident wave direction and beach opening direction. This angle was inclined 24° counterclockwise with the west-east direction. Therefore, the westward wave-induced currents developed strongly during the large-wave seasons. Hence, the sand content is high in the west-side beach but the east-side beach has been eroded seriously, where the pebbles are exposed and sand dune has decreased because of the lack of sand sources except for the soiled dunes. Therefore, it is proposed that efforts for creating new sediment sources, such as beach nourishment and reducing wave heights via submerged breakwaters, be undertaken for the eastside of the beach.

• Clean Technology
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• v.25 no.2
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• pp.129-139
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• 2019

Bamboo is an evergreen perennial plant, and it is known as one of the most productive and fastest-growing plants in the world. It grows quickly in moderate climates with only moderate water and fertilizer. Traditionally in Asia, bamboo is used for building materials, as a food source, and as versatile raw materials. Bamboo as a biomass feedstock can be transformed to prepare activated carbon using the thermal treatment of pyrolysis. The effect of process variables such as carbonization temperature, activation temperature, activation time, the amount of steam, and the mixing ratio of phosphoric acid and bamboo were systematically investigated to optimize the preparation conditions. Steam activation was proceeded after carbonization with a vapor flow rate of $0.8{\sim}1.8mL-H_2O\;g-char^{-1}\;h^{-1}$ and activation time of 1 ~ 3 h at $700{\sim}900^{\circ}C$. Carbon yield and surface area reached 2.04 ~ 20.59 wt% and $499.17{\sim}1074.04m^2\;g^{-1}$, respectively, with a steam flow rate of $1.4mL-H_2O\;g-char^{-1}\;h^{-1}$ for 2 h. Also, the carbon yield and surface area were 24.67 wt% and $1389.59m^2\;g^{-1}$, respectively, when the bamboo and phosphoric acid were mixed in a 1:1 weight ratio ($700^{\circ}C$, 2 h, $1.4mL-H_2O\;g-char^{-1}\;h^{-1}$). The adsorption of methylene blue into the bamboo activated carbon was studied based on pseudo first order and second order kinetics models. The adsorption kinetics were found to follow the pseudo second order model, which is governed by chemisorption.

• Korean Journal of Environmental Biology
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• v.36 no.3
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• pp.400-411
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• 2018

This study was a survey of the Wonju stream in Wonju city from May 2015 to September 2016. A total of three sites were selected from the upstream area Gwanseol-dong to the downstream area Hojeo-myeon. Physicochemical analysis, aquatic insect changes, cluster analysis, functional group analysis, rarefaction curve, and statistical analysis were compared between 2004 and 2016. A total of 19 species (38.78%) in 2004 and 22 species (36.67%) in 2016 were analyzed, with the largest number belonging to ephemeroptera. The individual ratio ranged from 27,759.2 (ind. $m^{-2}$, 84.30%) in 2004 to 4,573.2 (ind. $m^{-2}$, 41.64%) in 2016, with the highest number involving diptera. As a result of the community analysis, significant differences were detected in the indices of dominance, diversity, evenness, and richness in 2004 and 2016 (p<0.05). Burrowers of the habitat orientation groups showed the greatest variation with an average of -68.00% (${\pm}2.15$) and the collector-gatherers of the functional feeding groups showed the highest variation of -40.12% (${\pm}1.77$). The rarefaction curve analysis suggested that the species was the poorest in the midstream regions in 2004 and 2016. Physical factors and water quality showed a significant correlation with diversity index, evenness index, and the number of individuals. MDS analysis of the similarity of upstream and downstream regions was high in 2004, and low in 2016. The differences were attributed to physicochemical changes such as increase in flow velocity due to improvement of small dams and changes in bottom structure.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.647-658
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• 2018

The aim of this study is to investigate the seasonal changes of phytoplankton communities based on the environmental changes in a dense oyster farming area (Hansan-Geoje Island) from June to December 2016. The water temperature varied from $14^{\circ}C$ to $28.8^{\circ}C$ and its salinity ranged from 29.4 to 34.2 psu. Nitrate+nitrite was kept at c.a. $3.0{\mu}M$ on the surface layer from June to July, below the concentration limit in August and early September, and then gradually increased from late September. Ammonia was high on July 20 and August 10, and its seasonal characteristics were not clear. Phosphate ranged from 0.01 to $0.7{\mu}M$ on the surface layer, and its seasonal changes were similar to those of nitrate+nitrite. Mean silicate concentrations were $10.7{\mu}M$ on the surface and $15.7{\mu}M$ in the bottom layer, and it was not acted as a limiting factor for the growth of phytoplankton. Among the phytoplankton community, Bacillariophyceae, Dinophyceae and Cryptophyceae was 61.2%, 22.5%, and 13.6%, respectively. In late June, dinoflagellate Prorocentrum donghaiense was dominant in the outer waters(St. T1), later on, Cryptomonas spp. and Chaetoceros spp. were dominant, respectively. From late September to October, diatoms Pseudo-nitzschia spp. and Chaetoceros spp. were stimulated under non-stratified condition after the typhoon. In December, A. sanguinea was found to be $1.7{\times}10^5cells\;L^{-1}$. Seasonally, relative high phytoplankton biomass may be favorable to maintain high production of filter feeder oyster in the dense oyster farming areas of Hansan and Geoje Island.