• Journal of Practical Agriculture & Fisheries Research
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• v.19 no.1
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• pp.5-14
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• 2017

This study was conducted to investigate the effects of nutrient solution strength on growth and nutrient element concentrations in leaf lettuce (Lactuca sativa L. cv. 'Dduksum') by hydroponic culture under fluorescent lamp and LED. Leaf lettuce were grown in closed hydroponic cultivation systems supplied with 1/2, 1 and 2 strength of nutrient solution recommended by horticultural experiment station in Japan. The growth of 'Dduksum' was highest in the 2 strength of standard nutrient solution. The amount of nutrient element in the recycled nutrient solution was higher at 2, 1 and 1/2 strength of nutrient solution. The concentration of NO₃-N, Ca²⁺, Mg²⁺ in the recycled nutrient solutions increased in 1 and 2 strength of nutrient solution but that of NH₄-N decreased gradually in 1/2 and 1 strength of nutrient solution. The concentration of K, Ca, Mg in leaf lettuce was maintained in the normal range, whereas the concentration of phosphorous was 1.3 to 1.6%, which was higher than proper range. As the concentration of NH₄-N decreases gradually in all the treatments, it is necessary to raise the rate of NH₄-N or add it.

• Korean Journal of Environmental Biology
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• v.37 no.2
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• pp.129-135
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• 2019

Juvenile Paralichthys olivaceus (mean weight 685.3±36.7 g) were raised in different and closed recirculating bio-floc system (control, bio-ball, and shelter) for 7 months. The water environment such as water temperature, dissolved oxygen, salinity, pH, and alkalinity according to the difference of closed recirculating system remained stable during the rearing period. No significant changes were observed in dissolved inorganic nitrogen such as ammonia, nitrite, and nitrate were observed in different closed recirculation system. The final weights according to the difference of closed recirculating were 1,524 g (control), 1,674 g (bio-ball), and 1,630 g (shelter). The survival rate was higher than 98%, and the final FCRs (Feed coefficient ratio) were 1.2, 1.1, and 1.2. The results of this study indicated high growth and survival rate in all systems.

• Journal of Soil and Groundwater Environment
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• v.12 no.2
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• pp.9-19
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• 2007

This study investigated the interaction between groundwater and stream water systems, which is caused by the artificial weir on streambed, enforcing external stresses on the groundwater system. The study area is in Nami Natural Recreation Woods located in Chungcheongnam-do Geumsan-gun Nami-myeon Geoncheon-ri. In this study both of hydrophysical methods (hydraulic head) and hyrdochemical investigations (pH, EC, major ion analysis) were applied. In order to identify the relationship between each of study results, cross-correlation analysis is performed. From results of hydrophysical methods, water level fluctuation at BH-14, installed by the weir, shows the double-recession pattern much more frequently and much higher amplitudes than the fluctuation at each of other monitoring wells. Using the results by hydrochemical investigations, hydrochemical properties at BH-14 is similar to the hydrochemical characteristics in stream water. To analyze the interrelationships between the results from each of applied methods, cross-correlation analysis was applied. Results from the correlation analyses, water levels at BH-14 and stream weir showed the highest cross-correlation in hydrophysical aspects. On the other hand, the correlation between stream weir and bridge was the highest in hydrochemical aspects. The difference between the results from each of methods is due that the hydrophysical response at BH-14, such as water level, is induced by the pressure propagation-not with mass transfer, but the hydrochemical interaction, caused by mass transport, takes much more times. In conclusion impermeable artificial weir on streambed changes the interfacial condition between the stream and surrounding aquifers. The induced water flux into the groundwater system during flood period make water level at BH-14 increase instantly and groundwater quality higly similar to the quality of stream water. Referred similarities in both of water level and water quality at BH-14 become much higher when water level at weir grow higher.

• Journal of Aquaculture
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• v.18 no.2
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• pp.122-129
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• 2005

Ammonia is the major limiting factor in intensive aquaculture production systems. Therefore, quantification of ammonia excretion is important for the water quality management in aquaculture systems. Ammonia excretion is known to be affected by many factors such as body weight and dietary protein level (DPL). In this study, experiments were carried out to investigate the effects of body weight and DPLs on the rates of ammonia excretion of Nile tilapia Oreochromis niloticus. Three sizes of fishes (mean initial weight; 4.8 g,42.7 g and 176.8 g) were fed each of two dietary protein levels (30.5% and 35.5%). Daily feeding levels for the three fish sizes of 4.8 g, 42.7 g and 176.8 g were 6%, 3%, and 1.5% body weight per day, respectively. Each group of fish was stocked in a 17.1-L aquarium and all treatments were triplicated. Following feeding, the weight-specific ammonia excretion rate of O. niloticus increased, peaked at 4 to 8 h, and returned to pre-feeding levels within 24 h. Total ammonia nitrogen (TAN) excretion.ate per unit weight decreased with the increase of fish weight for each diet (P<0.05). The TAN excretion rate increased with increasing dietary protein content for each fish size (P<0.05). TAN excretion rates (Y) for each diet with different fish weights were described by the following equations: low DPL diet (30.5%): $Y\;(mg\;kg^{-1}\;d^{-1})=955.69-147.12\;lnX\;(r^2=0.95)$, high DPL diet (35.5%): $Y\;(mg\;kg^{-1}\;d^{-1})=1362.41-209.79\;lnX\;(r^2=0.99)$. Where: X=body weight (g wet wt.). The TAN excretion rates ranged 28.5%-37.1% of the total nitrogen ingested for the low DPL diet (30.5%) and 37.4-38.5% for the high DPL diet (35.5%). Total nitrogen losses of fish fed the high DPL diet $(35.5%;\;0.26\sim0.91g\;kg^{-1}\;d^{-1})$ were higher than those fed the low DPL diet $(30.5%;\;0.22\sim0.68g\;kg^{-1}\;d^{-1})$. The losses decreased per kg of fish as fish size increased. Results will provide valuable information fer water quality management and culture of Nile tilapia in recirculating aquaculture systems.

• Journal of Marine Bioscience and Biotechnology
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• v.1 no.2
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• pp.91-97
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• 2006

For efficient removal of nitrogenous compounds produced in recirculating aquaculture system, the N removal characteristics of immobilized mixed microorganisms were investigated at various mixing ratios of photosynthetic bacteria (PSB) immobilized in PVA beads or CTA cubes and ammonium utilizing bacteria (AUB) immobilized in PVA beads. On the optimal medium of AUB, the maxium gas production rate was obtained at the mixing ratio of 10:40 (PSB:AUB), and the gas production rate increased as the portion of AUB beads in the mixed beads increased. When the mixing ratios of PSB:AUB beads were 50:0, 40:10, 25:25 and 10:40, the final pHs were measured to be 6.29, 6.01, 5.69 and 5.13, respectively. On the optimal medium of PSB, however, the volume and the rate of gas production decreased remarkably as the portion of AUB beads in the mixed beads increased. The final pH was measured to be approximately 6.5, regardless of the mixing ratio. In the reactions by the mixed culture of PSB cubes and AUB beads, all results showed the same tendency of those by the mixed culture of PSB and AUB beads, but the volume and the rate of gas production decreased remarkably, even with 0.2ml of gas production in control. From all the results, the use of mixed PSB and AUB beads at the ratio of 10:40 seems to be efficient to remove nitrogenous compounds in wastewater from recirculating aquaculture system.

• Journal of Aquaculture
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• v.8 no.3
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• pp.149-157
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• 1995

In order to obtain the basic knowledges concerned to the semen preservation of aquacultural fishes, studies on the physical and chemical properties of semen, and sperm motility with the different osmotic pressures making by adding $Na^+,\;K^+,\; Mg^{++},\;and\;Ca^{++}$ to artificial seawater (ASW) were conducted in black seabream, Acanthopagrus schlegeli. Average semen volume per fish in one strip was 1.97ml and sperm concentration was $2.33\pm1.30\times10^{10}$ sperm/ml. Spermatocrit and pH of semen were $90.6\pm5.0\;and\;8.3\pm0.1$, respectively, Osmotic pressures of rearing seawater, seminal fluid and plasma were $939\pm24,382\pm70\;and\;342\pm77$ mOsm/l, and $Na^+,\;K^+$ and $Cl^-$ concentrations of seminal fluid were $169.5\pm4.5,\;4.9\pm2.2,\;156.0\pm2.0\;mM/l$, respectively. When semen were diluted by using $Na^+,\;K^+,\;Mg^{++}\;and\;Ca^{++}$ free ASW, only $Na^+$ free ASW had no sperm motility. As raising osmotic pressure graduary by addition of 1M NaCl to the $Na^+$ free ASW, spermatozoa showed the high motilities in 457-1128 mOsm/l, but the low motilities in 1398-1736 mOsm/l. In the case of same treatments with 1M of KCl, $MgC1_2\;and\;CaC1_2$ to the $K^+,\;Mg^{++}\;and\;Ca^{++}$ free ASW, spermatozoa revealed the high motilities in $904\~1434,\;818\~1175\;and\;956\~1343$ mOsm/l, respectively.

• Journal of Animal Environmental Science
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• v.18 no.2
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• pp.99-110
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• 2012

The purpose of the study is to collect basis data for to establish standard administrative processes of liquid fertilizer treatment. From this survey we could make out the key point of each step through a case of effective liquid manure treatment system in pig house. It is divided into six step; 1. piggery slurry management step, 2. Solid-liquid separation step, 3. liquid fertilizer treatment (aeration) step, 4. liquid fertilizer treatment (microorganism, recirculation and internal return) step, 5. liquid fertilizer treatment (completion) step, 6. land application step. From now on, standardization process of liquid manure treatment technologies need to be develop based on the six steps process.

• Geophysics and Geophysical Exploration
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• v.7 no.3
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• pp.164-173
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• 2004

To delineate geothermal water movement at the Pohang geothermal development site, Self-Potential (SP) survey and monitoring were carried out during pumping tests. Before drilling, background SP data have been gathered to figure out overall potential distribution of the site. The pumping test was performed in two separate periods: 24 hours in December 2003 and 72 hours in March 2004. SP monitoring started several days before the pumping tests with a 128-channel automatic recording system. The background SP survey showed a clear positive anomaly at the northern part of the boreholes, which may be interpreted as an up-flow Bone of the deep geothermal water due to electrokinetic potential generated by hydrothermal circulation. The first and second SP monitoring during the pumping tests performed to figure out the fluid flow in the geothermal reservoir but it was not easy to see clear variations of SP due to pumping and pumping stop. Since the area is covered by some 360 m-thick tertiary sediments with very low electrical resistivity (less than 10 ohm-m), the electrokinetic potential due to deep groundwater flow resulted in being seriously attenuated on the surface. However, when we compared the variation of SP with that of groundwater level and temperature of pumping water, we could identify some areas responsible to the pumping. Dominant SP changes are observed in the south-west part of the boreholes during both the preliminary and long-term pumping periods, where 3-D magnetotelluric survey showed low-resistivity anomaly at the depth of $600m\~1,000m$. Overall analysis suggests that there exist hydraulic connection through the southwestern part to the pumping well.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.114-115
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• 2003

양식 생물에게 있어 용존산소는 호흡에 필수적이며, 양식 시설 내에서 적절한 용존 산소량을 유지하는 것은 생산량을 좌우하는 가장 중요한 요인이며, 어종, 수온, 광주기, 나이와 크기, 어류의 행동과 먹이 공급 및 환경 조건에 따라 달라진다. 이 중 같은 종 내에서 선발육종된 개체와 일반 양식 종 그리고 이들 계통간 잡종에 대한 대사 효율 즉, 용존산소 소비율의 차이에 관한 연구는 거의 없다. 따라서 본 실험에서는 한국해양연구원에서 선발육종 해 온 참돔과 일본 양식산 참돔 및 이들의 교배 자손들을 대상으로 수온과 광주기 변화에 따른 용존산소 소비율을 조사하였다. 실험어는 일본 양식산인 TPN 교배구 자손과 한국해양연구원 선발육종산인 KORDI F4 교배구 자손, JPN♀×KORDI F4♂ 그리고 KORDI F4♀×JPN♂ 교배구 자손을 대상으로 실시하였다. 체중이 각각 52.0±0.6 g(JPN 교배구; 그룹 1), 52.3±0.7 g(JPN♀×KORDI F4♂; 그룹 2), 51.7±0.4 g(KORDI F4♀ × KORDI F4♂; 그룹 3) 그리고 52.1±0.7 g(KORDI F4♀ × JPN♂; 그룹 4)인 참돔 치어를 각각 5마리씩 3반복 수용하여 실험에 이용하였다. 실험기간 동안 사육수의 pH는 8.1±0.1, 염분도는 34.0±0.5‰로 유지하였으며, 실험 장치는 김(1999)이 고안한 순환 시스템을 이용하였다. 수온은 각각 15℃, 20℃ 및 25℃로 변화시켰으며 각 수온 조건에서 광주기를 24L:0D, 12L:12D 그리고 0L:24D로 변화시켜 매 조건마다 용존 산소 소비량을 측정하였다. JPN 교배구인 그룹 1의 경우, 수온 15℃일 때 산소 소비량은 170.35∼266.29 mg O₂/kg fish/hr의 범위를 보였으며 수온 20℃와 25℃일 때 각각 236.76∼307.37 mg O₂/kg fish/hr와 346.96∼459.30 mg O₂/kg fish/hr 범위를 보여 수온 상승에 따라 산소 소비량 역시 증가하는 것으로 나타났다. 그룹 2의 경우, 수온 15℃일 때 산소 소비량은 162.01∼279.51 mg O₂/kg fish/hr의 범위를 보였으며 수온 20℃와 25℃일 때 각각 303.48∼342.72 mg O₂/kg fish/hr와 447.18∼528.45 mg O₂/kg fish/hr 범위를 보여 그룹 1과 마찬가지로 수온 상승에 따라 산소 소비량 역시 증가하는 것으로 나타났다. 그룹 3의 경우, 수온 15℃일 때 산소 소비량은 170.11∼220.98 mg O₂/kg fish/hr의 범위를 보였으며 수온 20℃와 25℃일 때 각각 262.62∼282.27 mg O₂/kg fish/hr와 302.24∼415.73 mg O₂/kg fish/hr 범위를 보여 그룹 1, 2와 유사한 경향을 보였다. 그룹 4의 경우, 수온 15℃일 때 산소 소비량은 156.03∼214.49 mg O₂/kg fish/hr의 범위를 보였으며 수온 20℃와 25℃일 때 각각 238.40∼274.28 mg O₂/kg fish/hr와 379.93∼430.97 mg O₂/kg fish/hr 범위를 보여 수온 상승에 따라 산소 소비량 역시 증가하는 것으로 나타나, 그룹 1, 2와 유사한 경향을 보였다. 모든 실험구에서 수온 상승과 함께 산소 소비량이 증가하는 것으로 나타났으며 가장 높은 산소 소비량은 그룹 2에서 관찰되었다. 실험 결과 JPN 계통의 암컷을 사용하여 생산된 그룹 1과 2의 산소 소비량이 KORDI F4 계통의 암컷을 사용한 그룹 3, 4보다 대체적으로 높은 것으로 나타났다. 연속적인 명기 조건인 24L:0D에서 수온 15℃의 경우 그룹 1, 2, 3 그리고 4의 시간당 산소 소비량은 각각 266.29 mg O₂/kg fish/hr,279.51 mg O₂/kg fish/hr, 220.98 mg O₂/kg fish/hr 그리고 214.49 mg O₂/kg fish/hr으로 나타났고, 명기와 암기가 동일한 조건인 12L:12D에서는 각각 192.20 mg O₂/kg fish/hr, 258.03 mg O₂/kg fish/hr, 192.76 mg O₂/kg fish/hr 그리고 170.40 mg O₂/kg fish/hr로 나타났다. 또한 연속적인 암기 조건인 OL:24D 조건에서는 각각 170.35 mg O₂/kg fish/hr, 162.01 mg O₂/kg fish/hr, 170.11 mg O₂/kg fish/hr 그리고 156.03 mg O₂,/kg fish/hr로 나타났다. 그리고 수온 20℃와 25℃에서도 그룹간의 변화는 이와 비슷한 경향을 보였다. 연속 명기 조건인 24L:0D에서의 산소 소비량이 명기와 암기가 동일한 조건인 12L:12D와 연속 암기 조건인 0L:24D에서의 산소 소비량 보다 대체적으로 높은 것으로 나타났으며, 그룹 2의 연속 명기 조건에서 528.45 mg O₂/kg fish/hr으로 가장 높게 나타났다. 그룹 4에서는 대사량이 점점 더 높아지는 수온 상승과 함께 연속 명기 조건과 더불어 12L:12D 조건에서의 산소 소비량이 크게 증가하는 것으로 나타났다.