• Horticultural Science & Technology
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• v.34 no.6
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• pp.871-877
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• 2016

Recycling nutrient solutions in closed hydroponic production systems is usually accompanied by an imbalance of nutrient solutions when concentration is controlled according to electrical conductivity (EC) levels. This study investigated whether it was possible to automatically control the concentrations of five essential elements nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) using only N, K and Ca ion sensors. N, P, K, Ca, and Mg uptake was measured in the nutrient solution, and relationships between absorbed ions were analyzed through twice-repeated experiments in lettuce. Results confirmed that the pattern of $PO_4$ ion uptake was similar that of N, and the pattern of Mg ion uptake was similar that of Ca. $PO_4$ ion uptake was most highly correlated with N, and Mg was most highly correlated with Ca. Regression coefficients of N and $PO_4$ were significantly different at 1.04 and 0.55, respectively, but were similar between Ca and Mg at 0.35 and 0.40, respectively. Additional experiments were conducted to measure nutrient uptake in pak choi and rose plants, both to confirm the results from the first experiment in lettuce, and to assess possible application to other crops. Coefficients of determination both for N and $PO_4$, and Ca and Mg were considerably high ($R^2=0.86$) in cultured pak choi, and similar results were observed in cultured rose ($R^2=0.87$ and 0.73, respectively). Regression coefficients for cultured pak choi were 0.56 and 0.24, respectively, and for rose were 0.51 and 0.16, respectively. Although the results obtained for N and $PO_4$ were not consistent between the lettuce experiments, N and $PO_4$ have similar regression coefficients for all crops. No common coefficient was found between Ca and Mg.

• Korean Journal of Ecology and Environment
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• v.38 no.1 s.110
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• pp.1-10
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• 2005

Macroinvertebrates from a first order stream at Mt Jumbong, Kangwon-do, was examined for their abundance and biomass. Sampling was done by using a pipe sampler (${\phi}$ 20 cm) for 11occasions (n = 5) at 4${\sim}$6 weeks intervals during November 1997 through October 1998. Water temperature and electronic conductivity of the study stream ranged $0\;{\sim}\;14^{\circ}C$ and 15${\sim}$25 ${\mu}s$/cm, respectively. During the study, 53 insect taxa and 3 non-insect taxa were collected. Annual mean number of individuals (${\pm}$1 SD) was 77741${\pm}$69232${\cdot}$m$^{-2}$ ${\cdot}$yr$^{-1}$, being high in winter (${\pm}$1 SD) (December: 171178${\pm}$130468 $m^{-2}$) and low in summer (${\pm}$ 1 SD) (June: 29872${\pm}$13078 $m^{-2}$). Non-predatory subfamilies of Chironomidae and Nemoura sp. occupied 53.3% and 21.8% of annual abundance. Annual mean biomass was 10g${\cdot}$m$^{-2}$${\cdot}$yr$^{-1}$ in ash free dry weight (AFDW), being high in late winter (February: 16 gAFDW $m^{-2}$.) and low in summer (June: 3 gAFDW $m^{-2}$). Gammarus sp. represented 39.8% of the total biomass and was followed by non-predatory subfamilies of Chironomidae (15.2%) and Hydatohylax sp. (8.5%, Limnephilidae: Trichoptera). Since the non-predatory subfamilies of chironomidae were composed of many species, Nemoura sp. was the most abundant taxon. However, Cammarus sp. was surely the most important taxon to the functional aspects of this first order stream ecosystems.

• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.68-76
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• 2008

This study examined the inhibition effects of a freshwater bivalve (Unio douglasiae) and a submerged plant (Potamogeton crispus) on the cyanobacterial bloom (Oscillatoria sp.). The experiment were conducted in aquarium $(50cm{\times}65cm{\times}120cm)$ with lake sediments in the bottom of the aquarium in 10 cm thick. Before the experiments, artificial cyanobacterial bloom was induced with the addition of lake sediment and CB medium. Total 12 transparent acrylic cylinders (${\Phi}19cm$, height 40 cm) were placed in the aquarium, and within which bivalves and plants were placed in various conditions such as the control (C), plant addition (P:5 stems), mussel addition (U:2 individuals), and both mussel and plant addition (PU: the same quantity as used in each treatment). The experiment was conducted in triplicate during 7 days. pH, dissolved oxygen (DO), electric conductivity (EC), salinity, cyanobacterial cell density, chlorophyll-${\alpha}$ concentration, and mussel filtering rate were monitored daily. At the end of the experiment, total phosphorus (TP), total nitrogen (TN), and plant height and weight were measured. Overall, a large degree of cyanobacterial growth inhibition appeared in both P and U treatments, and the effect was highest in the U treatment, followed by P and PU. The combined treatment of both U and P did not show any synergic effects compared to the effect in separated treatment. In all enclosures of the treatments chlorophyll-${alpha}$ (Chl-${alpha}$) concentration decreased until 36 hours after the additions of the plants and mussels. In contrast, Chl-${alpha}$ concentrations increased in PU enclosures after 36 hours. The same trend was shown in the cell density of Oscillatoria. pH and DO gradually decreased until 120 and 144 hours, respectively, in the P and PU enclosures. TP concentration increased in the mussel enclosures (U and PU), while TN concentration largely decreased in the plant enclosures (P and PU). Our results suggest that applied bivalve (Unio) and submerged plant (Potamogeton) seemed to have a potential effect on the growth inhibition of cyanobacteria, but their combined application may have an antagonistic effect to diminish the degree of the inhibition.

• Korean Journal of Ecology and Environment
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• v.45 no.2
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• pp.218-231
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• 2012

The objectives of this study were to evaluate the physico-chemical water quality, trophic and tolerance guilds in the control ($C_o$) and impacted streams of the abandoned mine, along with the ecological health, using a multimetric health model and physical habitat conditions of Qualitative Habitat Evaluation Index (QHEI), during the period of three years, 2005~2007. Also, eco-toxicity ($EE_t$) enclosure tests were conducted to examine the toxic effects on the outflows from the mine wastewater, using the sentinel species of Rhynchocypris oxycephalus, and we compared the biological responses of the control ($C_o$) and treatment (T) to the effluents through a Necropybased Health Assessment Index ($N_b$-HAI). Tissue impact analysis of the spleen, kidney, gill, liver, eyes, and fins were conducted in the controlled enclosure experiments (10 individuals). According to the comparisons of the control ($C_o$) vs. the treatment (T) in physicochemical water quality, outflows from the abandoned mine resulted in low pH of 3.2, strong acid wastewater, high ionic concentrations, based on an electrical conductivity, and high total dissolved solid (TDS). Physical habitat assessments, based on Qualitative Habitat Evaluation Index (QHEI) did not show any statistical differences (p>0.05) in the sampling sites, whereas, the $M_m$-EH model values in a multimetric ecological health ($M_m$-EH) model of the Index of Biological Integrity (IBI), using fish assemblages, were 16~20 (fair condition) in the control and all zero (0, poor condition) in the impacted sites of mine wastewater. In addition, in enclosure eco-toxicity ($EE_t$) tests, the model values of $N_b$-HAI ranged between 0 and 3 in the controls during the three years, indicating an excellent~good condition (Ex~G), and were >100 (range: 100~137) in the impacted sites, which indicates a poor condition (P). Under the circumstances, organ tissues, such as the liver, kidney, and gills were largely impaired, so that efficient water quality managements are required in the outflow area of the abandoned mine watershed.

• Korean Journal of Ecology and Environment
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• v.41 no.2
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• pp.237-246
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• 2008

Filtration rates and fecal production of freshwater bivalve, Unio douglasiae on two kinds of hibernal diatom communities were measured simultaneously in a laboratory. One community is the Han River (HAN), which dominated by Asterionella Formosa. Stephanodiscus hantzschii (ca. 98% of total phytoplankton). The other community is the Ilgam Lake (IL), which dominated by Synedra ulna, Scenedesmus sp. Microcystis aeruginosa (ca. 82%). The HAN water has higher concentrations of nutrient (TN and TP) and chlorophyll $\alpha$ (Chl-$\alpha$), lower turbidity and conductivity than the IL water. Water sampling for the feeding experiment was conducted in the same day (Jan 15, 2008) and similar time (AM 10:00 for HAN, AM 11:00 for IL). Mussels with the similar size ($0.0{\pm}0.5\;cm$) were collected from the Gunsan and Okgu district (Jeonbuk), and starved in a laboratory for 2 days before the experiment. The experiment comprised CON (no addition of mussel), LOW (addition of mussel at 0.3 indiv. $L^{-1}$), MID (1.0 indiv. $L^{-1}$) and HIGH (2.0 indiv. $L^{-1}$), respectively. With the increment of mussel density and time, the concentration of Chl-$\alpha$ in two diatom communities were clearly decreased; Chl-$\alpha$ of HAN gradually decreased after 1 hour of mussel treatment, while that of IL decreased as soon as mussel introduction. In 7 hours of treatment, the former was removed finally up to about 90% of control, while the later was remained as about 50%. Under the presence of mussel, total phytoplankton density was shifted as the similar patterns to that of Chl-$\alpha$ (r=0.705, P<0.0001), however, there showed the drastic differences following a species. Based on the concentration of Chl-$\alpha$, filtration rate of U. douglasiae averaged 0.266 $L\;g^{-1}\;h^{-1}$ (0.115 to 0.442) on HAN and $0.577\;L\;g^{-1}\;h^{-1}$ (0.146 to 1.428) on IL water, respectively. There were no differences in feces production among the mussel density in the HAH water (ANOVA, P>0.5), while in IL water, including lots of seston, the HIGH mussel produced the higher fecal materials, over one hundred times of LOW. These results suggest that freshwater bivalve Unio douglasiae have the alternative potential, as a filter-feeder of seston in turbid lake, and a biological controller of diatom bloom in cold stream.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.3
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• pp.308-318
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• 2013

Korean soybean varieties, 'Seonyu' and 'Hwangkeum' were planted in 2012, and three temperature gradient, Tc($19.8^{\circ}C$, ambient temperatured), $Tc+1.7^{\circ}C$, and $Tc+2.5^{\circ}C$, were artificially created by controlling the green house system during seed filling period. Mature seeds that developed under these conditions were analyzed for variances in physicochemical properties. The 100-seed weight and seed-coat ratio of soybean were decreased, but small seed rate was increased by high temperature during seed filling period. Protein content was increased, but oil content was decreased significantly with increasing the seed filling temperature. The decrement of carbon to nitrogen ratio (C/N), and the increment of monosaccharide, fructose and sucrose, in seeds explained that carbohydrate assimilation during seed filling was restricted by high temperature. Rapid increments of seed volume and weight were observed in the seeds of high seed filling temperature, but as soaking time increased the highest values were observed in the seeds of ambient seed filling temperature. The 100-seed weight and seed-coat ratio of soybean were closely related not only to the increment of soaking volume and weight, but also the increments of total dissolved solids (TDS) and electro conductivity (EC). Whereas protein content and C/N ratio showed less relationship with the soaking properties, but they had a positive correlation with TDS and EC. From the results, it was considered that high values of TDS and EC in the seeds of high temperature were mainly due to the incomplete conversion of assimilates into storage compounds. However, sugar content showed less influence on the soaking properties and the values of TDS and EC.

• Journal of Biomedical Engineering Research
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• v.25 no.5
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• pp.403-414
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• 2004

In the accompanying paper, we proposed a real. time volumetric imaging method using a cross array based on receive dynamic focusing and synthetic aperture focusing along lateral and elevational directions, respetively. But synthetic aperture methods using spherical waves are subject to beam spreading with increasing depth due to the wave diffraction phenomenon. Moreover, since the proposed method uses only one element for each transmission, it has a limited transmit power. To overcome these limitations, we propose a new real. time volumetric imaging method using cross arrays based on synthetic aperture technique with linear wave fronts. In the proposed method, linear wave fronts having different angles on the horizontal plane is transmitted successively from all transmit array elements. On receive, by employing the conventional dynamic focusing and synthetic aperture methods along lateral and elevational directions, respectively, ultrasound waves can be focused effectively at all imaging points. Mathematical analysis and computer simulation results show that the proposed method can provide uniform elevational resolution over a large depth of field. Especially, since the new method can construct a volume image with a limited number of transmit receive events using a full transmit aperture, it is suitable for real-time 3D imaging with high transmit power and volume rate.

• Journal of Bio-Environment Control
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• v.11 no.4
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• pp.151-156
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• 2002

Root zone cooling, such as soil or nutrient solution cooling, is less expensive than air cooling in the whole greenhouse and is effective in promoting root activity, improving water absorption rate, decreasing plant temperature, and reducing high temperature stress. The heat transfer of a soil cooling system in a plastic greenhouse was analyzed to estimate cooling loads. The thermal conductivity of soil, calculated by measured heat fluxes in the soil, showed the positive correlation with the soil water content. It ranged from 0.83 to 0.96 W.m$^{[-10]}$ .$^{\circ}C$$^{[-10]}$ at 19 to 36％ of soil water contents. As the indoor solar radiation increased, the temperature difference between soil surface and indoor air linearly increased. At 300 to 800 W.m$^{-2}$ of indoor solar radiations, the soil surface temperature rose from 3.5 to 7.$0^{\circ}C$ in bare ground and 1.0 to 2.5$^{\circ}C$ under the canopy. Cooling loads in the root zone soil were estimated with solar radiation, soil water content, and temperature difference between air and soil. At 300 to 600 W.m$^{-2}$ of indoor solar radiations and 20 to 40％ of soil water contents,46 to 59 W.m$^{-2}$ of soil cooling loads are required to maintain the temperature difference of 1$0^{\circ}C$ between indoor air and root zone soil.

• Korean Journal of Ecology and Environment
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• v.44 no.2
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• pp.239-251
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• 2011

To compare the different water environments in the Jigsaw stream (st. 1, 2) and Jujin stream (st. 3, 4) crossing over the Byeonsan-Bando and Seonunsan parklands, the physico-chemical factors and the species compositions of epilithic diatoms were analyzed from March 2009 to February 2010. The mean values of conductivity (681.1 ${\mu}S\;cm^{-1}$), suspended solids (27.83 mg $L^{-1}$), biological oxygen demand (3.15 mg $L^{-1}$), total nitrogen (3.24 mg $L^{-1}$), total phosphorus (0.24 mg $L^{-1}$) and chlorophyll-${\alpha}$ (12.99 mg $m^{-3}$ ) in Jujin stream were significantly higher than each element in Jigsaw stream. Eighty taxa were classified into 73 species and seven varieties belonging to 24 genera, eight families, three suborders and two orders in Jigsaw stream. Eighty eight taxa were classified into 81 species and seven varieties belonging to 22 genera, seven families, three suborders and two orders in Jujin stream. Biological water quality assessments revealed that Jigsaw stream was ${\beta}$~${\alpha}$-oligosaprobic and Jujin stream was ${\beta}$-mesosaprobic. Dominant and diversity indices were indicated from 0.25~0.81 and from 1.73~4.14 in Jigsaw stream, respectively, and from 0.29~0.64 and from 2.72~4.02 in Jujin stream, respectively. Jujin stream was more eutrophic than those of Jigsaw stream. The different water environments between the two streams could be due to the different ecosystems of the neighboring basins of each stream crossing over in the mountain. Further studies should investigate the water environments of two streams by continuous and regular monitoring to analyze the different ecosystem mechanisms.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.307-318
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• 2010

This study was to analyze the ecological conditions, based on physical habitat, chemical, and biological conditions before (2006, 2007) and after ecological restoration (2009) in five sites of Changwon Stream (CS) and six sites of Nam Stream (NS), respectively, and then to compare ecological health between the two period. The analysis of ecological health was based on the multimetric models of Index of Biological Integrity (IBI) and Qualitative Habitat Evaluation Index (QHEI) along with water chemistry in the streams. For the study, the models of IBI and QHEI were modified as 8 and 11 metric attributes, respectively. For the evaluations, the survey was conducted in the period of 2006~2007 before the restoration and in 2009 after the restoration by the city. Chemical conditions, based on conductivity, in both streams showed a typical longitudinal declines along the axis of the upstream-to-downstream. There were no significant differences (p>0.05) in water quality between the two periods. Values of IBI in the CS and NS averaged 21.6 and 19.7, respectively, indicating a C grade in the criteria of Ministry of Environment, Korea, and there was no significant differences in the IBI between the two periods. Values of QHEI after the restoration averaged 29.2 and 63.2 in the CS and NS, respectively and the values decreased markedly especially, in the NS (35.3) after the restoration. The habitat disturbance was mainly attributed to destructions (i.e., the narrower width of riparian vegetation and higher substrate exposure by the air) of artificial materials by massive flood in 2009. Overall, our results suggest that the restoration was not effective in the two streams between the two periods, even if the budget was used a lot and that such ecological restoration, not considered the natural disaster, may not effect for the stream restoration.