• Journal of Bio-Environment Control
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• v.19 no.4
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• pp.251-256
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• 2010

Objective of this research was to investigate the influence of $NH_4^+$ and $NO_3^-$ ratios in liquid feeding on the growth of snapdragon 'Potomac Red' and changes in medium chemical properties. The seeds were sown into 200 plug trays and fertigated once a week with nutrient solution containing various ratios of $NH_4^+$ and $NO_3^-$ such as 0 : 100, 27 : 73, 50 : 50, 73 : 27, and 100 : 0. The total N concentrations were adjusted to 50, 100 and $150\;mg{\cdot}L^{-1}$ in plug stages of 2, 3, and 4, respectively. Determination of seedling growth and analysis of plant tissue and root medum were conducted at 56 days after sowing. The treatment of 27 : 73 ($NH_4^+:NO_3^-$) had the greatest plant height, fresh weight, and dry weight. The N and P contents in 27 : 73 ($NH_4^+:NO_3^-$) treatment based on the above ground plant tissues were 2.39 and 0.39%, respectively, which were the greatest among treatments. The elevation of $NH_4^+$ ratio in fertigation solution decreased tissue Ca and Mg contents, but that did not influence tissue K content. The variations in $NH_4^+:NO_3^-$ ratios impacted the soil solution pH and the difference among treatments had been severe since three weeks after sowing. Elevation of $NH_4^+$ ratios in fertigation solution increased electrical conductivity and concentrations of K, Ca, and Mg in soil solution of root medum. The $NH_4^+$ and $NO_3^-$ concentrations in the soil solution were high in weeks 2, 3, and 4, then decreased gradually as the biomass of seedlings increased. Medium P concentration decreased gradually as seedlings grew, but statistical differences were not observed among treatments.

• Korean Journal of Environmental Biology
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• v.26 no.3
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• pp.252-263
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• 2008

The purpose of this study was to determine trophic state, based on nutrients (TN, TP), transparency (SD), and chlorophyll-${\alpha}$ (Chl) and identify their empirical relations of TN-Chl, TP-Chl and Chl-SD depending on the dataset used along with dynamics of conductivity and suspended solids. Analysis of trophic states showed that more than half of 36 reservoirs were judged as eutrophic-hypertrophic conditions depending on the trophic variables. Seasonal values of TP varied by nearly 500% and showed greater in August than any other months. In contrast, TN varied within less than 90% and all monthly mean values of TN were never fall less than 1.2 mg L$^{-1}$ indicating low seasonal variations and high ambient concentrations (eutrophic-hypertrophic state). Analysis of empirical relations in the trophic variables showed that transparency had greater functional relations with Chl (R$^2$=0.31, p<0.001) than TP (R$^2$=0.15, p<0.001) and TN (R$^2$=0.20, p<0.001). Ratios of TN : TP in the ambient water indicated that most reservoirs showed a potential phosphorous limitation on the algal growth. Thus, algal biomass, based on Chl values, was more regulated by phosphorous than nitrogen. Analysis of linear regression model, based on log-transformed annual mean values, showed that only 30% in the variation of Chl was explained by TP (R$^2$=0.295, p=0.001, n=36) and 15% by TN (R$^2$=0.151, p=0.019, n=36). However, linear regression model, based on individual system, showed that Chl-TP model had strong positive relations (R$^2$=0.62, p=0.002, n=12), whereas the model had no any relations (p=0.892, n=12). Overall, our data suggested that averaging effect in the empirical model developments may influence the significance in the statistical analysis.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.1
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• pp.27-38
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• 2011

The distributions of phytoplankton assemblages and environmental factors in Jinhae Bay and their relationships were investigated to estimate the potential limiting nutrient for phytoplankton growth and community structure. In situ algal bioassay experiments were also conducted to assess the species-specific characteristics in phytoplankton responses under different nutrient conditions (control, N(+) and P(+) treatment). During the study periods, bacillariophyceae and cryptophyceae occupied more than 90% of total phytoplankton assemblages. Phytoplankton standing crops in the inner part of Masan Bay were higher than that of Jinhae Bay. The DIN:DIP ratio, pH and transparency showed the significant positive correlation with phytoplankton biomass. According to cluster and multidimensiolnal scaling (MDS) analysis based on phytoplankton community data from each station, the bay was divided into three groups. The first group included stations from the south-western part of Jinhae bay where cryptophyta species were dominated. The second group was distinguished from inner stations in Masan Bay. These stations showed low transpancy and high DIN:DIP ratio. The other cluster included the stations from the eastern part and central part of Jinhae Bay, which was characterized by the high DSi:DIP ratio and dominant of diatom species. Phosphorous (P) was limited in Masan Bay due to significantly increases in the phytoplankton abundances. Based on stoichiometric limitation and algal bio-assay in Jinhae Bay, nitrogen (N) was a major limiting factor for phytoplankton production. However, silicate (Si) was not considered as limiting factor, since Si/DIN and Si/P ratio and absolute concentration of nutrient did not create any potential stoichiometric limitation in the bay. This implies that high Si availability in winter season contributes favorably to the maintenances of diatom species.

• Korean Journal of Soil Science and Fertilizer
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• v.41 no.1
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• pp.65-73
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• 2008

Because main barley straw management is changing these days from off-fields to burning that may relate to air quality concerning the global warming, this study was conducted to investigate the effects of barley-straw management practices on greenhouse gas emissions during rice cultivation in rice-barley double cropping system. The treatments were barley straw burning, off-field usage of barley straw and incorporation of barley straw in paddy fields. Laboratory experiment showed that burning of barley straw at the rate of $4.5Mg\;ha^{-1}$ emitted GHGs in the amounts of 4,607, 19.5, and $0.9kg\;ha^{-1}$ of $CO_2$, $CH_4$, and $N_2O$, respectively. During the rice cultivation of the rice-barley double cropping system, the highest GHG emission by evaluated close-static chamber method was observed from the soil incorporation of barley straw with 387 and $1.0kg\;ha^{-1}$ of $CH_4$ and $N_2O$, respectively. The GHGs emissions from the barley straw burning and off-field usage treatments were 233 and $160kg\;ha^{-1}$ for $CH_4$ and 0.80 and $0.79kg\;ha^{-1}$ for $N_2O$, respectively. The barley straw burning treatment showed the greatest GHGs emission among barley straw management practices in rice-barley double cropping system when considering GHGs emissions both during burning and from paddy fields during the cropping seasons. As a result, the GHGs emissions recorded in the barley straw incorporation to soil and off-field usage treatments were 22.4 and 66.8%, respectively, less than sum of GHGs emissions from the burning of barley straw and from paddy fields during rice cultivation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.60 no.4
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• pp.510-517
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• 2015

Miscanthus has been considered as the most promising bioenergy crop for lignocellulosic biomass production. In Korea, M. sacchariflorus and M. sinensis can be found easily in all regions. It is a great advantage to utilize as important species with respect to genetic and cross-breeding programs materials for creation of novel hybrids. For successful breeding programs, it is important to precisely understand the variability of flowering traits among Miscanthus species as breeding parents materials. In this study, flowering traits were observed daily in 960 germplasms of two Miscanthus species (M. sacchariflorus and M. sinensis) for growing seasons over 2 years. The flowering process was divided into three stages. ST (sprouting time) was recorded when first leaf of the plant emerged on soil. FS1 (flowering stage 1) and FS2 (flowering stage 2) were recorded when flag leaf was firstly observed, and 1 cm of panicle was showing on at least one stem, respectively. For 2013 and 2014, the latest germplasms exerted flag leaf, i.e. September 30 (DOY of FS1 164.1) and September 4 (DOY of FS1 141.0) occurred M. sacchariflorus cv. Geodae 1 and M. sacchariflorus cv. Uram collected from Southern Korea (Jeollanam-do), while Miscanthus germplasms collected from northern Korea (Gyeonggi-do) which emerged the earliest flag leaf in July and August, significantly decreased DOY. For DOY from ST to FS2, M. sacchriflorus germplasms ranged from 140 to 190 days, and 110 to 170 days for 2013 and 2014. The highest frequency showed to 160 days for 2013, and 150 days for 2014. In M. sinensis germplasms, the highest frequency showed to 180 days for 2013, and 170 days for 2014. In the results of correlation between the day of years from ST to FS2 for 2013 and 2014, M. sacchriflorus and M. sinensis showed high coefficient of correlation (0.70 and 0.89). It can be supposed that flowering characteristics of Miscanthus are largely affected by the unique phenotypic characteristic of native habitat than environmental factors of the current planted site. This study for flowering traits of Miscanthus may provides an important information in order to expedite the introduction as breeding materials for creation of new hybrid.

• Korean Journal of Environmental Biology
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• v.32 no.3
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• pp.168-175
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• 2014

In order to understand the phytoplankton community structure based on their cell size duringlow water temperature periods, we studied 10 stations in the East Sea, Korea on March, 2012. The minimum standing crops of total phytoplankton were $3.4{\times}10^6cells\;L^{-1}$ at the station 5. The maximum values were $7.6{\times}10^6cells\;L^{-1}$ at the station 8, which is two times the amount of the minimum. The carbon mass at the station 4 ($6.3{\times}10^8pg\;L^{-1}$) was more than forty times higher compared with station 5 ($0.08{\times}10^8pg\;L^{-1}$). From these results, we found a significant difference between standing crops and carbon mass which might have caused due to their differences in community structure and cell size. Therefore, we considered the types of plankton biomass to estimate the primary product in the specific location and/or time. The phytoplankton communities were classified in 3 types: microplankton (> $20{\mu}m$), nanoplankton (< $20{\mu}m$) and picoplankton (< $2{\mu}m$). In the case of picoplankton, various morphological types were observed during the study period. These various picoplankton species were further classified as S (spherical), SF (spherical&flagella), O (oval), OF (oval&flagella) or R (rod) type, and we analyzed their community structure based on these categories. The picoplankton was found to be the most dominant type at 8 stations and S type as the most popular. The picoplankton seems to be the significant organism in the marine ecology during low water temperature periods in the coastal waters of East Sea. Therefore, picoplankton \;-with scientific surveys can be considered as the database for their identification. In conclusion, we suggest that cell size of the phytoplankton would be the best criteria to accurately analyze their community structure and to reveal groups having more ecological influence.

• Economic and Environmental Geology
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• v.47 no.1
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• pp.39-48
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• 2014

In coastal region, estuaries have complex environments where dissolved and particulate matters are mixed with marine water and substances. Suspended sediment (SS) dynamics in coastal water, in particular, plays a major role in erosion/deposition processes, biomass primary production and the transport of nutrients, micropollutants, heavy metals, etc. Temporal variation in suspended sediment concentration (SSC) can be used to explain erosion/sedimentation patterns within coastal zones. Remotely sensed data can be an efficient tool for mapping SS in coastal waters. In this study, we analyzed the variation in SSC in coastal water using the Geostationary Ocean Color Imager (GOCI) and Landsat Enhanced Thematic Mapper Plus (ETM+) in Gyeonggi-bay. Daily variations in GOCI-derived SSC showed low values during ebb time. Current velocity and water level at 9 and 10 am is 37.6, 28.65 $cm{\cdot}s^{-1}$ and -1.23, -0.61 m respectively. Water level has increased to 1.18 m at flood time. In other words, strong current velocity and increased water level affected high SSC value before flood time but SSC decreased after flood time. Also, we compared seasonal SSC with the river discharge from the Han River and the Imjin River. In summer season, river discharge showed high amount, when SSC had high value near the inland. At this time SSC in open sea had low value. In contrast, river discharge amount from inland showed low value in winter season and, consequently, SSC in the open sea had high value because of northwest monsoon.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.96-101
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• 2009

In this study, the effects of three different biological activated carbon (BAC) materials (each coal, coconut and wood based activated carbons), empty bed contact time (EBCT) and water temperature on the removal of sulfonamide 5 species in BAC filters were investigated. Experiments were conducted at three water temperatures (5, 15 and $25^{\circ}C$) and four EBCTs (5, 10, 15 and 20 min). The results indicated that coal based BAC retained more attached bacterial biomass on the surface of the activated carbon than the other BACs, increasing EBCT or increasing water temperature increased the sulfonamide 5 species removal in BAC columns. In the coal-based BAC columns, sulfachloropyridazine (SCP), sulfamethazine (SMT) and sulfathiazole (STZ) removal efficiencies were 30~80% and sulfadimethoxine (SDM), sulfamethoxazole (SMX) removal efficiencies were 18~70% for 5~20 min EBCT at $25^{\circ}C$. The kinetic analysis suggested a first-order reaction model for sulfonamide 5 species removal at various water temperatures (5~$25^{\circ}C$). The pseudo-first-order reaction rate constants and half-lives were also calculated for sulfonamide 5 species removal at 5~$25^{\circ}C$. The reaction rate and half-lives of sulfonamide 5 species ranging from 0.0094~0.0718 $min^{-1}$ and 9.7 to 73.7 min various water temperaturs and EBCTs in this study could be used to assist water utilities in designing and operating BAC filters for sulfonamide antibiotic compounds removal.

• Korean Journal of Environment and Ecology
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• v.30 no.5
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• pp.874-887
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• 2016

We surveyed bimonthly from April to October 2015 to understand the fish fauna and community structure in Wangpicheon. The collected species during the survey period were 40 species belonging to 15 families. Dominant species by number were Zacco koreanus (31.3%) and Rhynchocypris oxycephalus (14.7%). In biomass, the dominant species were Z. koreanus (29.2%) and Coreoperca herzi (8.6%). Also, nine endemic species (22.5%) including Squalidus multimaculatus and two endangered species (Lethenteron reissneri, Cottus koreanus) were identified. It was identified one introduced species (Oncorhynchus mykiss) from foreign countries for aquaculture. Compared with previous data, nine species were newly identified including L. reissneri, S. gracilis majimae, Pseudobagrus fulvidraco, O. mykiss, Chelon haematocheilus, Siniperca scherzeri, Acanthogobius lactipes, Luciogobius guttatus and Channa argus. Seven species (Rhodeus ocellatus, S. gracilis majimae, Hemibarbus longirostris, Pseudogobio esocinus, Microphysogobio yaluensis, Hemiculter eigenmanni and Cobitis hankugensis) introduced from other native waters in Korea were estimated. According to the analysis of the habitat characteristics of major migratory species (Tribolodon hakonensis, O. keta and Plecoglossus altivelis), O. keta was observed at station 11 and T. hakonensis at station 7, 10 and 11. These fishes have been mainly identified in the downstream. However P. altivelis was widely distributed from station 3 to 11. In the comparison of average standard length of P. altivelis at each station during the same period, populations collected from station 3 and 5 which are mid-upper area of the stream were $125.8{\pm}34.2mm$. Their growth was good compared with those collected from station 8 and 11 (mid-lower area): $80.2{\pm}16.6mm$. This difference in length comes from the artificial structures including weir, thus it is necessary to create a fishway that enables P. altivelis to pass around barriers for free movement and resource management.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.11
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• pp.783-789
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• 2011

Recently, auto-thermal thermophilic aerobic digestion (ATAD) has a great attention for destruction of wasted sludge biomass in wastewater treatment plant. Reduction of sludge concentration has been successfully achieved with pilot scale ATAD and ceramic filtration process in field condition. However, high concentration of COD, total nitrogen (TN) and total phosphorus (TP) was observed in filtrate, which should be treated before recirculation of filtrate to biological wastewater treatment plant. This study was focused on removal of nitrogen and phosphorus contained in the filtrate of ATAD, using struvite crystallization method. The effect of operational and environmental parameters (such as, N, P and Mg ion concentration and molar ratio, pH, reaction time, agitation strength, seed dosage, and reaction temperature) on the treatment of TN and TP with struvite crystallization were evaluated. Magnesium (as $MgCl_26H_2O$) and phosphorus (as $K_2HPO_4$) ions were, if necessary, added to increase nitrogen removal efficiency by the crystal formation. Average concentration of $NH_4^+-N$ and $PO_4^{3-}-P$ of the filtrate were 1716.5 mg/L and 325.5 mg/L, respectively. Relationship between removal efficiencies of nitrogen and phosphorus and molar ratios of $Mg^{2+}$ and $PO_4^{3-}-P$ to $NH_4^+-N$ was examined. Crystal formation and nitrogen removal efficiencies were significantly increased as increasing molar ratios of magnesium and phosphorus to nitrogen. As molar ratio of $Mg^{2+}:PO_4^{3-}-P:NH_4^+-N$ were maintained to 2 : 1 : 1 and 2 : 2 : 1, removal efficiencies of nitrogen and phosphorus were 71.6% and 99.9%, and 93.8% and 98.6%, respectively. However, the effect of reaction time, mixing intensity, seed dose and temperature on the struvite crystallization reaction was not significant, comparing to those of molar ratios. Settled sludge volume after struvite crystallization was observed to be reduced with increase of seed dose and to be increased at high temperature.