• 한국해양학회지
• /
• v.29 no.3
• /
• pp.239-247
• /
• 1994

Bedform morphology of the giant ripples have been studied on the continental shelf of the Yellow Sea, East China sea and Korea-Tsushima Strait on the basis of side-scan sonar image, sub-bottom profile, sedimentary facies, geomorphology evidence and hydrology. There are well developed giant ripples ranging from 100 to 500 m in wavelengths and from 2 to 10 m in wave height at nine sites in the study area, which are covered by medium to fine sand. Most of them have been formed under the present hydrologic regime where the tidal currents and local currents or turbulence flows are superimposed. In the study area, giant ripples are produced on two different environments. One is at the geomorphic narrow zone such as the Korea Strait where currents are accelerated by the topographic effects, while the other is the sandy flat plain where tidal currents and local currents are harmonized.

• Korean journal of applied entomology
• /
• v.34 no.1
• /
• pp.75-81
• /
• 1995

To reduce crop damage from root-knot nematode, Meloidogyne spp. chemical, cultural, physical control methods were compared in commercial greenhouse for 3 years from 1992 to 1994. Timing of sol exchange for economic losses due to the nematodes is important: every 3 years for coarse sand (Masatto) and every 4 years for red-yellow soil. Control effects on Meloidogyne spp. in cucumber were 78.2% in Dazomet DP, 72.1% Carbo G+Soil reverse+submergence, and 66.3% in Carbo G+submergence. Pesticide effects were temporally different after treatment: 77.7~80.6% in 20 days and 33.7~49.5% in 60 days. Cropping system in oriental melon gave an excellent control effect of 81.1% at oriental melon/rice culture. All methods controled root-knot nematodes at the time of the treatment but the number of the nematodes increased at the end of the season. However, soil exchange was effective for 3 years. The most economic control practice is rotation with rice for every three years.

• Journal of Korean Society of Water and Wastewater
• /
• v.34 no.4
• /
• pp.267-276
• /
• 2020

In this study, air scouring cleaning was selected and applied among 5 small blocks (S1~S5) in domestic S cities to analyze the cleaning effect of particles causing discoloration. In order to identify the cleaning effect, 10 locations were selected as water quality investigation point, such as the stagnant or water mains ends. Removal of solids, variation of particle components, weight and concentration were analyzed. And the level of the cleanness of the surface inside water mains using endoscope was investigated. As a result of analysis, the solids discharged after cleaning were mainly sand and gravel, pieces related to pipe materials, and corrosion products. As a result of analyzing the concentrated particles of the filter before and after cleaning, it was found that the change in discoloration on the filter was large. In addition, as a result of comparing the weight and the concentration of the particles, it was found that the particles causing discoloration were significantly removed after cleaning. From the results of the endoscopy, it was confirmed that most of the precipitated and accumulated dark yellow discoloration matters inside water mains were removed through cleaning. Therefore, it seems that the particles causing discoloration in water decreased after cleaning. Therefore, it is expected that, if properly cleaning was applied, matters that cause discoloration can be removed from the water mains, and customer's complaints can also be reduced through water quality improvement.

• The Korean Journal of Ecology
• /
• v.1 no.2
• /
• pp.44-48
• /
• 1977

The spawning behavior and developmental pattern of the Korean eleotrid fish (Odontobutis obscurus) was investigated in one of the tributary of Han River. The spawining of this species begins on April and continues up to August, whereas, the spawning. of same species were between the end of June and the middle of July in Kyushu, Japan. August The spawning places were the margin of river, its the bottom composed of sand and pebble (Table 5). The velocity of water in the spawning places was 0-40cm/sec, and the depth of waters was 10-40cm. The egg was spawned on underside of stone in the spawning places with one or two folds and ellipsoid in shape, 3.4mm in long diameter and 2.0mm in short diameter. The yolk is 1.2mm in diameter and yellow in color. For hatching of the egg, it takes one month in, $16^{circ}C~19^{\circ}C$ water, in Japan, whereas it takes only 14 days in $20^{circ}C~30^{\circ}C$ wate rin the study area. The growth rate of larva and juvenile fish were as follows: new hatched larva is 45mm in length; after 5 days it became 5.0 to 5.5mm in length and 1.2 to 1.5mm in height after 20 days. it became 11.0mm in length and 2.3mm in length. The mean size of the mature female is 110mm in total length and larger 10mm than that of the same fish found in Japan.

• Journal of Korean Society for Atmospheric Environment
• /
• v.11 no.2
• /
• pp.179-184
• /
• 1995

This study was carried out to characterize sources of suspended particulate matter(SPM) in Mt. Soback area from January to Novembver in 1993. The collection and major water soluble ion analysis of SPM were conducted by using a High Volumn Air Sampler(HVAS; W&A Inc., PM-10) and ion chromatograph(DIONEX 4000i), respectively. The variations of SPM and major ion concentrations were found to be 9. sim. 156.mu.g/ $m^{3}$, $F^{-10}$ 0.00 .sim. 0.15.mu.g/ $m^{3}$, C $l^{-10}$ 0.06 .sim. 3.79.mu.g/ $m^{3}$, N $O_{3}$$^{-10}$ 0.90 .sim. 6.85.mu.g/ $m^{3}$, S $O_{4}$$^{2-}$ 1.99 .sim. 9.36.mu.g/ $m^{3}$ N $a^{+}$0.00 .sim. 0.27.mu.g/ $m^{3}$, N $H_{4}$ $^{+}$0.72 .sim. 5.77.mu.g/ $m^{3}$, $k^{+}$0.03 .sim. 0.88.mu.g/ $m^{3}$ and $Ca^{2+}$0.12 .sim. 2.76.mu.g/ $m^{3}$. Tree sources were identified by Principal Component Amalysis(PCA) using a SPSS/P $C^{+}$. The explanation ability of forst, second and third Principal Component were 60.8%, 13.6%, 8.2%, of total variance. The sources classfied by PCA were found to be secondary aerosol/fuel combustion, soil dust related cement production/yellow sand and aerosol related waste burning.related waste burning.g.

• Journal of environmental and Sanitary engineering
• /
• v.9 no.2
• /
• pp.8-23
• /
• 1994

During the period from Mar., 1991 to Feb., 1992 66 tSP samples were collected by Hi volume air sampler at 1 sampling site in Seoul and the amount of concentration of 21 components(SO$_{4}$$^{2-}$, NO$_{3}$$^{-}$, NH$_{4}$$^{+}$, Cl$^{-}$, Al, Ba, Ca, Cd, Cr, Cu, Fe, It Mg, Mn, Na, Ni, Pt Si, Ti, Zn, Zr ) were measured. And monthly and seasonal variation were surveyed and the principal component analysis( PCA ) were carried out with respect to these amount of pollutants, minimum of visibility and radiation on a horizontal surface. The total amount of soluble ion in water was high in order o(SO$_{4}$$^{2-}$> NO$_{3}$$^{-}$> N%'>Cl$^{-}$ and metal ion was high in order of Na> Ca>Si> Fe> Al> K> Mg> Zn> Pb> Cu>Ti> Mn > Ba> Cr> Zr> Ni> Cd. There was Seasonal variation in concentration for SO$_{4}$$^{2-}$, NH$_{4}$$^{+}$, Cl$^{-}$, Na, Al, Ca, Bt Mg, Fe and Si. It was assumed that the components of the highest concentration on April were depend on yellow sand and the frequency of wind velocity and direction. As the results of PCA, the amount of pollution components was able to characterized with two principal components(Z$_{1}$, Z$_{2}$ ). The first principal components Z$_{1}$ was considered to be a factor indicating the pollutants originated from natural generation and The second principal components Z$_{2}$ was considered to be a factor indicating the pollutants originated from human work. The monthly concentration of pollutants in ISP, minimum of visibility and radiation on a horizontal surface was possible to evaluate by the use of these two principal components Z$_{1}$ and Z$_{2}$ .

• Atmosphere
• /
• v.28 no.2
• /
• pp.175-185
• /
• 2018

Characteristics of precipitation response to enhanced aerosols have been investigated during the severe haze events observed in Korea for 2011 to 2016. All 6-years haze events are classified into long-range transported haze (LH: 31%), urban haze (UH: 28%), and yellow sand (YS: 18%) in order. Long-range transported one is mainly discussed in this study. Interestingly, both LH (68%) and YS (87%) appear to be more frequently accompanied with precipitation than UH (48%). We also found out the different timing of precipitation for LH and YS, respectively. The variations of precipitation frequency for the LH event tend to coincide with aerosol variations specifically in terms of temporal covariation, which is in contrast with YS. Increased aerosol loadings following precipitation for the YS event seems to be primarily controlled by large scale synoptic forcing. Meanwhile, aerosols for the LH event may be closely associated with precipitation longevity through changes in cloud microphysics such that enhanced aerosols can increase smaller cloud droplets and further extend light precipitation at weaker rate. Notably, precipitation persisted longer than operational weather forecast not considering detailed aerosol-cloud interactions, but the timescale was limited within a day. This result demonstrates active interactions between aerosols and meteorology such as probable modifications of cloud microphysics and precipitation, synoptic-induced dust transport, and precipitation-scavenging in Korea. Understanding of aerosol potential effect on precipitation will contribute to improving the performance of numerical weather model especially in terms of precipitation timing and location.

• Journal of Ginseng Research
• /
• v.13 no.1
• /
• pp.105-113
• /
• 1989

This study was conducted to determine the cause of the occurence of marginal leaf chlorosis in ginseng plants (Panax ginseng C.A. Meyer), and to determine its emersion in fields (practically) and in pots (experimentally). The following results were obtained. In the Present investigation, ginseng plants raised in acidic soil containing a high a moue t of Mn showed marginal leaf chlorosis. Henre it Ivas suggested that the shoot growth and root weights became grad gractually lower. The leaves having marginal leaf chlorosis contained low amounts of N, P,. Ca, Mg, and Na and the Fe/Mn ratios were low. There was a corresponding increase in Mn uptake. It was founrl that in soils where marginal leaf chlorisis occured the pH urar brlolv 4.2 to 4.9 and the Ca, Mg and Na content was decreased thus effectively increasing the available manganese in the soil. The Mn/Fe ratios in the yellow leaf margins of ginseng Plants affected by the Mn toxicity was over 2.0 compared to the general Mn/Fe ratio of 0.50 for healthily leaves, stems and roots. Typically when ginseng plants grow fields having soil with a pH below about 5.0, there tenor to be an uptake of excess Mn. When ginseng plants are grown in a nutrient sand culture solution It with an increased Mn concentration, they accumulate large amounts of Mn in the roots and in the shoots. In both casts marginal leaf chlorosis appeared in the emersions. In the Present investigation, ginseng plants raised in acidic soil and containing a high amount of Mn showed marginal leaf chlorosis.

• Ocean and Polar Research
• /
• v.27 no.4
• /
• pp.433-441
• /
• 2005

To investigate the characteristics of tidal currents and water circulation in the coastal waters off the Taean Peninsula, tidal currents and sea levels were measured at the study area from 1998 to 2004. In the central waterway to the south of Changan Sand Ridge, mean speed of tidal currents and residual currents were 74.0cm/s, 17.8cm/s respectively; the dominant residual currents flowed northeastward, and the amplitudes of semi-diurnal components $(M_2,\;S_2)$ were larger than diurnal components $(O_1,\;K_1)$. The flood and ebb tidal currents were northeastward and southwestward, respectively, and each period was about 6 hours for them, which was consistent with the period of sea levels at the study area. In the coastal region near Hakampo, Taean, mean velocities of tidal currents and residual currents were 46.1cm/s, 30.8cm/s respectively, and the dominant residual currents flowed southwestward. The amplitudes of shallow water constituents $(M_4,\;MS_4)$ were relatively laige, which were weaker to the northeastern coastal region off Mineodo. The northeastward flow continued for about $2{\sim}3$ hours, while the southwestward flow continued for about $9{\sim}10$ hours near Hakampo during the tidal period. Tidal currents flowed northeastward in the central area of the waterway during the period from the Low Water Level (LWL) to the High Water Level (HWL). While the currents in the coastal region flowed northeastward for the first 3 hours after the LWL, southwestward counter-currents flowed between 3 and 6 hours after the LWL. During the period from the HWL to the LWL, the dominant currents flowed southwestward in the study area except to the northeastern coastal region off Mineodo. Along the shorelines, the counter-currents flowed northward between 4 and 6 hours after the HWL. It seems that the counter-currents near the coastal region are caused by the topography and the geography of the shorelines at the study area.

• Journal of Environmental Science International
• /
• v.11 no.2
• /
• pp.111-120
• /
• 2002

Asian dust(or yellow sand) occurs mainly in spring and occasionally in winter in east Asia, when the weather conditions are under an upper trough/cut-off low and surface high/low pressure system during blocking episode days associated with the stationary patterns of the upper level jet stream. The transport mechanism for Asian dust during the blocking episode days in spring 2001 was analyzed using the TOMS aerosol index and meteorological mesoscale model 5(MM5). Based on the E vector, an extension of an Eliassen-Palm flux, the blocking episode days were found to be associated with the development of an upper cut-off low and surface cyclones. Concurrently, the occurrence of dust storms was also determined by strong cold advection at the rear of a jet streak, which exhibited a maximum wind speed within the upper jet stream. As such, the transport mechanism for Asian dust from China was due to advection of the isentropic potential vorticity(IPV) and isentropic surfaces associated with tropopause folding. The transport heights for Asian dust during the blocking episode days were found to be associated with the distribution of the isentropes below the IPV At the same time, lee waves propagated by topography affected the downward motion and blocking of Asian dust in China. The Asian dust transported from the dust source regions was deposited by fallout and rain-out with a reinforcing frontogenesis within a surface cyclone, as determined from satellite images using TOMS and GMS5. Accordingly, these results emphasize the importance of forecasting jet streaks, the IPV, and isentropes with geopotential heights in east Asia.