• Journal of Korea Water Resources Association
• /
• v.52 no.11
• /
• pp.917-929
• /
• 2019

Denitrification in streams is of great importance because it is essential for amelioration of water quality and accurate estimation of $N_2O$ budgets. Denitrification is a major biological source or sink of $N_2O$, an important greenhouse gas, which is a multi-step respiratory process that converts nitrate ($NO_3{^-}$) to gaseous forms of nitrogen ($N_2$ or $N_2O$). In aquatic ecosystems, the complex interactions of water flooding condition, substrate supply, hydrodynamic and biogeochemical properties modulate the extent of multi-step reactions required for $N_2O$ flux. Although water flow in streambed and residence time affect reaction output, effects of a complex interaction of hydrodynamic, geomorphology and biogeochemical controls on the magnitude of denitrification in streams are still illusive. In this work, we built a two-dimensional water flow channel and measured $N_2O$ flux from channel sediment with different bed geomorphology by using static closed chambers. Two independent experiments were conducted with identical flume and geomorphology but sediment with differences in dissolved organic carbon (DOC). The experiment flume was a circulation channel through which the effluent flows back, and the size of it was $37m{\times}1.2m{\times}1m$. Five days before the experiment began, urea fertilizer (46% N) was added to sediment with the rate of $0.5kg\;N/m^2$. A sand dune (1 m length and 0.15 m height) was made at the middle of channel to simulate variations in microtopography. In high- DOC experiment, $N_2O$ flux increases in the direction of flow, while the highest flux ($14.6{\pm}8.40{\mu}g\;N_2O-N/m^2\;hr$) was measured in the slope on the back side of the sand dune. followed by decreases afterward. In contrast, low DOC sediment did not show the geomorphological variations. We found that even though topographic variation influenced $N_2O$ flux and chemical properties, this effect is highly constrained by carbon availability.

• Korean Journal of Microbiology
• /
• v.39 no.2
• /
• pp.95-101
• /
• 2003

The total bacterial numbers, Eubacterial community structures and environmental factors which affect bacterial community were estimated monthly using DAPI and fluorescent in situ hybridization monthly, from June to November 2000 to evaluate the correlation between the bacterial community and environmental factors in eutrophic agricultural Masan reservoir in Asan. Average water temperatures varied from 12.3 to $27.5^{\circ}C$, pH 7.5 to 9.0, DO 7. I~12.8 mg/L, COD 6.4~13.0 mg/L, chlorophyll a 30.5~99.0 mg/㎥, SS 7.S~25.7 mg/L, TN 1.748~3.543 mg/L., and TP 0.104~0.581 mg/L, respectively. Total bacterial numbers showed high ranges from 0.4 to 9.6$\times$ $10^{6}$ cells/ml, and these indicated the mesotrophic or eutrophic state. The ratio of Eubacteria to total bacteria was 67.6-88.0%, which was higher than that in other reservoir. The relationships of total bacteria and Eubacteria community were more significant with organic nitrogen (Org-N), and organic phosphorus (Org-P) than with water temperature. Proteobacteria groups showed strongly significant relationships with Org-P and Org-N and significant relationships with water temperature, conductivity, COD, and inorganic nitrogen. C-F group was the most significant with Org-N, and HGC group with water temperature. However, relationships of Chl-a, pH, DO and SS showed no significance with any bacterial community. These results were different from other studies, because of the specific characteristics of Masan reservoir such as old, shallow and eutrophic states. The seasonal variation of bacterial community in Masan reservoir does not seem to depend on phytoplankton dynamics but on storm event and organic materials from watershed and the sediment of reservoir.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.8 no.1
• /
• pp.90-96
• /
• 2000

The composition of leachates varies depending on the waste characteristics, landfill age and landfilling method. Generally, leachates contain high dissolved organic substance and ammonia nitrogen whereas phosphorus concentration was very low. Leachate A produced from young landfill is characterized by high BOD5/COD ratio (0.8) whereas leachate C produced from old landfill has lower BOD5/COD ratio (0.1). Maximum biochemical methane potential of leachate A, B (from medium landfill) and C were 271,106 and 4 ml CH4/g-COD, respectively. On the other hand, the maximum biodegradability of leachate A, B, and C were 75,30, and 1%, respectively. These results indicated that anaerobic treatment of leachate from young landfill was effective in removing organic pollutants. In case of leachate C, carbon might reside in the form of large molecular weight organic compounds such as lignins, humic acids and other polymerized compounds of soils, which are resistant to biodegradation. The lag-phase period increased with the increasing organic concentration in leachate. In case of leachate A of concentration greater than 25%, the lag-phase period increased sharply. This implied that the start-up period of anaerobic process using an unacclimated inoculum could be extended due to the higher concentration of leachate. This relatively long lag-phase is probably related to the fact that most of the inhibitory compounds have been diluted beyond their inhibitory concentrations of less than 50%. Furthermore, the ultimate methane yield and methane production rate decreased as leachate concentration increased. It was anticipated the potential inhibition was related with the steady-state inhibition as well as the initial shock load.

• Journal of Aquaculture
• /
• v.11 no.3
• /
• pp.391-400
• /
• 1998

This study was performed to investigate the effects of environmental parameters on the growth of Pacific oyster, Crassostrea gigas at old suspended culturing grounds of Korsung Bay and newly deveoped bottom, culturing grounds of Haenam region located in southern coast of Korea. The Kosung Bay was semiclosed and water exchange occurred through the small mouth and the current speed was very slow as the value of below 0.5kn. Haenam was opened and littoral zone. Current speed of the surroundings of this Bay about to 5.0knand transparency was low with the mean depth of 1.2m by the resuspension of the sediments. Water temperature and salinity regimes were suitable for oysters at those sites, however the mean value of those parameters and seasonal fluctuations was high at Kosung. The mean concentration of dissolved oxygen in survey area was above $5.0mg/\ell$. In Kosung, however, it was decreasing in June and showed the minimum with the concentration of $4.0mg/\ell$ in August at the bottom layer and recovered in September. Eutrophication parameters such as COD were 1.44 mg/l at this location. This mean value was higher than that of the Haenam Bay's $0.96mg/\ell$. The men value of chlorophyll-$\alpha$ at Haenam was two times higher than the other sites. Growth of shell height and meat weight of oysters at Kosung Bay were higher and the fatness was lower compared to thost of Haenam. As a result, absolute growth of oysters was high at Kosung and allometric growth, such as fatness, was good at Haenam. Low water temperature and frequent exposure of oysters to the air during ebb tide may retard the shell growth. On the other hand, relatively high food availability was profitable for the fatness at haenam site.

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

• Korean Journal of Ecology and Environment
• /
• v.44 no.1
• /
• pp.9-21
• /
• 2011

This study is conducted to know the change in water environment of Lake Hwajinpo from 2000 to 2008 with physico-chemical parameters; salinity, dissolved oxygen, total phosphorus and total nitrogen and others. And zooplanktons and phytoplanktons were studied from 2007 to 2008. From the water quality data of Lake Hwajinpo from 2000 to 200S; water temperature, salinity, transparency, chemical oxygen demand and dissolved oxygen ranges are $2.8{\sim}29.4^{\circ}C$, 0.23~33.2‰, $0.2{\sim}1.8\;m$, $0.2{\sim}20.2\;mg\;L^{-1}$ and $0.1{\sim}17.4\;mg\;L^{-1}$ and the average values are $18.0^{\circ}C$, 15.7‰, 0.7 m, $5.7\;mg\;L^{-1}$ and $8.0\;mg\;L^{-1}$, respectively. Total phosphorus (TP) and total nitrogen (TN) ranges are $0.024{\sim}0.869\;mg\;L^{-1}$ (average 0.091) and $0.240{\sim}5.310\;mg\;L^{-1}$ (average 1.235). Average TN/TP ratio is 16.4. The annual variations in COD, TP, TN and Chl.${\alpha}$ are compared. COD in 2000 is $4.83\;mg\;L^{-1}$ and 2008 is $1.80\;mg\;L^{-1}$ which is reduced by $0.34\;mg\;L^{-1}$ every year. TP in 2000 is $0.07\;mg\;L^{-1}$ and 2008 is $0.05\;mg\;L^{-1}$ reduced gradually. Yearly reduction in TN is $0.09\;mg\;L^{-1}$, in 2000 and 2008 the values are $1.54\;mg\;L^{-1}$ and $0.77\;mg\;L^{-1}$ respectivly. Chl.${\alpha}$ in 2000 is $46.30\;{\mu}g\;L^{-1}$ and $5.78\;{\mu}g\;L^{-1}$ in 2008; yearly reduction is $4.50\;{\mu}g\;L^{-1}$. The tropic state index (TSI) in south and north parts of Lake Hwajinpo in 2000 are 67 and 63 which are reduced to 63 and 59 in 2008 respectively. North and south part of Lake Hwajinpo have 67 species of phytoplankton under 47 families in 2007 and 2008. Dominant species in south part in 2007 are; Asterococcus superbus in May, Lyngbya sp. in September and Trachelomonas spp. in November and in 2008 Anabaena spiroides in August are abundant and varies with time. Zooplankton species in Lake Hwajinpo are 25 of 25 families. Dominant species in south part in May and August 2007 and May and November in 2008 Copepoda larvae and in September 2007 Protozoa spp. of Protozoan and Brachionus plicatilis and Brachionus urceolaris of Cladocera in August 2008. Dominant species in north part Asplanchna sp. of Cladecera in August and November 2007 and rest of the time are larvae of Copepoda. In this way, the water quality of Lake Hwajinpo is changing with slow rate in the long period specially nutrients concentration (TP, TN etc) is decreasing.