• Clean Technology
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• v.25 no.3
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• pp.198-205
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• 2019

The adsorption equilibrium, kinetic, and thermodynamic parameters of brilliant green adsorbed by coconut based granular activated carbon were determined from various initial concentrations ($300{\sim}500mg\;L^{-1}$), contact time (1 ~ 12 h), and adsorption temperature (303 ~ 323 K) through batch experiments. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Harkins-Jura, and Elovich isotherm models. The estimated Langmuir dimensionless separation factor ($R_L=0.018{\sim}0.040$) and Freundlich constant ($n^{-1}=0.176{\sim}0.206$) show that adsorption of brilliant green by activated carbon is an effective treatment process. Adsorption heat constants ($B=12.43{\sim}17.15J\;mol^{-1}$) estimated by the Temkin equation corresponded to physical adsorption. The isothermal parameter ($A_{HJ}$) by the Harkins-Jura equation showed that the heterogeneous pore distribution increased with increasing temperature. The maximum adsorption capacity by the Elovich equation was found to be much smaller than the experimental value. The adsorption process was best described by the pseudo second order model, and intraparticle diffusion was a rate limiting step in the adsorption process. The intraparticle diffusion rate constant increased because the dye activity increased with increases in the initial concentration. Also, as the initial concentration increased, the influence of the boundary layer also increased. Negative Gibbs free energy ($-10.3{\sim}-11.4kJ\;mol^{-1}$), positive enthalpy change ($18.63kJ\;mol^{-1}$), and activation energy ($26.28kJ\;mol^{-1}$) indicate respectively that the adsorption process is spontaneous, endothermic, and physical adsorption.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.5
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• pp.327-334
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• 2014

This study aims to estimate settling velocity ($W_s$) for cohesive sediments from water bodies (Incheon Coast, Kulpo Stream and Han River) mainly connected to the Kyeongin Ara-waterway through the laboratory settling experiments. Results of settling tests for these sediments show that $W_s$ values for sediments are quite different each other: $W_s$ values of Kulpo Stream sediments (0.01 < $W_s$ < 3.07 mm/s) are quite similar with those of Han River sediments (0.01 < $W_s$ < 2.97 mm/s) over the whole range of suspension concentration C (0.1 < C < 90 g/ L), while they are quite different with those for Incheon Coast sediments (0.01 < $W_s$ <0.92 mm/s). Qualitative analyses on test results for physico- chemical properties of sediments and waters with respect to settling velocities show that these differences in settling velocities are mainly due to the salinity difference in the water.

• The Korean Journal of Ecology
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• v.25 no.5
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• pp.305-313
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• 2002

The physico-chemical characteristics of water and sediment, and structures of vegetation of the vascular hydrophytes were investigated in the West Nakdong River. Water quality was eutrophic according to the mean values and the ranges of water properties such as pH, DO, BOD, chlorophyll a, total nitrogen and phosphate, and other nutrients. A few cases were hypereutrophic for chlorophyll a level in summer. Soil reaction was weak acid. Composition of sediment was mainly sand except in SI(Sinan chideung) of which was mainly clay, and SU(Suan chideung) of which was mainly silt. Flora of vascular hydrophyte had 26 species and 1 variety comprising 16 families. Trapa japonica was dominant species in the sites of DU(Dunchido), GA(Garak chideung) and SU. Nymphoides peltata and Hydrocharis dubia dominated in DA and SI, respectively. Species diversity and evenness were relatively high in SI and SU but dominance was high in DA. After June, water lettuce(Pistia stratiotes) and water hyacinth(Eichhornia crassipes) were flowed from tributary to the river. Standing crop of macrohydrophytes was high in DA from April to August, but it showed maximum standing crop (445g·dw/㎡) in DU after disturbance by explosive growth of exotic plants in October. In comparison with those in 1985, total productivities in DU and GA decreased to 33.5%, and the reduction ratio of dominant species, Trapa japonica was 56.7%. Najas marina, N. minor, Myriophyllum spicatum and Nymphoides indica have disappeared ever since the Nakdong barrage was constructed in the Nakdong river. They were divided into three groups (GA-SU-DU, DA, SI) by cluster analysis. Introduction of the exotic species in this river caused decreasing of endemic plants including endangered species Euryale ferox and rare species Hydocharis dubia, and food plants for waterfowl such as Trapa japonica, Vallisneria asiatica and Potamogeton crispus.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.2
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• pp.67-83
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• 2012

In order to evaluate die geochemical characteristics of sediment in a semi-enclosed bay used as shellfish and fish farming area, the concentrations of metallic(V, Cr, Mn, Fe, Co. Ni, Cu, Zn, Ag, Cd, Hg, Ph, As) and non-metallic(P, Se) elements and uranium were measured in the surface sediment samples collected from 19 stations of Gamak Bay in April 2010. Metal contamination status in the sediments were also evaluated using the sediment quality guidelines(SQGs) proposed by the National Oceanic and Atmospheric Administration(NOAA) and the enrichment factor(EF). The concentrations of elements in sediment were mainly controlled by quartz-dilution effect(V, Cr, Fe, Co and Ni), the dilution effect of organic matter(Cd and U), and metal redistribution by the decomposition of organic matter(Mn, Ag, As, and Se). The concentrations of metals, except As and Ni, in sediments from all sampling stations were lower than ERL values of NOAA. Conclusively, the surface sediment of Gamak Bay was slightly polluted with Ni, Ag, Cd, and Cd but was not polluted with other elements on the basis of EF results. Our results suggest that the surface sediment in Gamak Bay is not polluted by metallic elements.

• Journal of Marine Life Science
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• v.5 no.2
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• pp.99-106
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• 2020

To investigate effect of variation in physiochemical conditions due to river discharge on phytoplankton, field surveys were conducted in the Seomjin and Yeongsan River estuaries from April to November 2016. The concentrations of DIN and DSi in Seomjin River estuary were gradually low as distance from upstream. On the other hands, the concentrations of DIN and DSi in Yeongsan River estuary were critically high at upstream, due to which is characterized as semi-enclosed eutrophic area. A total of 12 phytoplankton pigments were analyzed, and the distribution of each taxa was investigated using indicator for each phytoplankton taxa. Fucoxanthin, an indicator pigment of diatoms, showed an average of 0.61±1.00 ㎍ l^-1 and 0.76±1.22 ㎍ l^-1 in the Seomjin and Yeongsan River estuaries, respectively. Concentration of fucoxanthin was more than twice that of other pigments except chlorophyll a., indicating that diatoms were dominant taxa. Peridinin, an indicator pigment of dinoflagellate, showed some similar tendency to the microscopic observation, but mismatch results were also present, indicating a technical limitation of pigment analysis. Chlorophyll b, alloxanthin, and zeaxanthin, which are indicator pigments of green algae, cryptomonads, and cyanobacteria, were detected in both estuaries even though those taxa were not detected in microscopic observation. This indicates that the two estuaries were affected by freshwater species. Here, we can suggest that phytoplankton composition in estuary was directly influenced by the inflow from upstream. In particular, the phytoplankton population dynamics in Yeongsan River estuary was greatly associated with a large-scale artificial dyke, especially in summer rainy season. On the other hands, the seasonal and horizontal distribution of phytoplankton in Seomjin River estuary has changed along the salinity gradients and inflow-related changes.

• Korean Journal of Remote Sensing
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• v.37 no.6_1
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• pp.1739-1756
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• 2021

Atmospheric nitrogen dioxide (NO₂) is mainly caused by anthropogenic emissions. It contributes to the formation of secondary pollutants and ozone through chemical reactions, and adversely affects human health. Although ground stations to monitor NO₂ concentrations in real time are operated in Korea, they have a limitation that it is difficult to analyze the spatial distribution of NO₂ concentrations, especially over the areas with no stations. Therefore, this study conducted a comparative experiment of spatial interpolation of NO₂ concentrations based on two linear-regression methods(i.e., multi linear regression (MLR), and regression kriging (RK)), and two machine learning approaches (i.e., random forest (RF), and support vector regression (SVR)) for the year of 2020. Four approaches were compared using leave-one-out-cross validation (LOOCV). The daily LOOCV results showed that MLR, RK, and SVR produced the average daily index of agreement (IOA) of 0.57, which was higher than that of RF (0.50). The average daily normalized root mean square error of RK was 0.9483%, which was slightly lower than those of the other models. MLR, RK and SVR showed similar seasonal distribution patterns, and the dynamic range of the resultant NO₂ concentrations from these three models was similar while that from RF was relatively small. The multivariate linear regression approaches are expected to be a promising method for spatial interpolation of ground-level NO₂ concentrations and other parameters in urban areas.

• Korean Journal of Environment and Ecology
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• v.35 no.6
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• pp.669-678
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• 2021

This study surveyed three land cover types in Chungju City in Chungcheongbuk Province to check the distribution of cultured bacteria in bio-aerosols according to land cover type. It was possible to compare and analyze the distribution of bacteria according to microclimatic changes at each measurement point by examining meteorological factors and bio-aerosols according to land cover. The microclimate temperature in each measurement point was 8.7℃ for the urban forest, 10.8℃ for the waterside green area, and 10.2℃ for the urban area, indicating the urban forest had the lowest temperature among the measurement points. The relative humanity was 61.8% fin the urban forest, 59.3% in the waterside green area, and 55.7% in the urban area, indicating that the urban forest was the most humid among the measurement points. The identified bacteria were found to be 43 genera and 99 species. In terms of species diversity of cultured bacteria, 22 genera were found in the waterside green area, 21 genera in the urban forest, and 17 genera in the urban area, 37 species were found in the waterside green area, 31 species in the urban area, and 31 species in the urban forest. Bacillus toyonensis and Pseudarthrobacter oxydan were the species present in all three types of measurement sites, and Herbiconiux flava was confirmed to inhabit green areas such as urban forests and waterside green areas. The analysis result of the bacterial concentration according to the microclimatic environment in each measurement point was 333 CFU/m³ in the urban forest, 287 CFU/m³, in the waterside green area, and 173 CFU/m³ in the downtown area. The relative humidity and wind speed were analyzed to show a similar trend as the concentration. This study is expected to provide basic data for healthy urban management and green area creation by identifying the distribution of cultured bacteria in bio-aerosols according to land cover type and comparing and analyzing the traits of bio-aerosol in each measurement point.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.178-189
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• 2008

The distribution of inorganic nutrients and their remineralization ratio in the divergence zone ($7^{\circ}{\sim}10.5^{\circ}N$) of the northeastern Pacific were investigated from July 2003 to July 2007. A divergence zone along the boundary of the North Equatorial Counter Current (NECC) and North Equatorial Current (NEC) at $10^{\circ}N$ was observed in July 2007 when the La Nina event and divergence-related upwelling was strong. The mean depth of oligotrophic surface mixed layer in the divergence zone was 46, 61, and 30 m in July 2003, August 2005, and July 2007, respectively. Below the surface mixed layer, a nutricline was clearly observed. The depth integrated value of nitrate including nitrite (DIVn) in the upper layer($0{\sim}100$ m depth) ranged from 5.51 to 21.71 $gN/m^2$(mean 12.82 $gN/m^2$) in July 2003, from 5.62 to 8.46 $gN/m^2$ (mean 7.15 $gN/m^2$) in August 2005, and from 8.98 to 27.80 $gN/m^2$(mean 21.12 $gN/m^2$) in July 2007. The maximum DIVn was observed at the divergence zone. The distributions of phosphate(DIVp) and silicate(DIVsi) were similar to that of DIVn and the DIVn/DIVsi ratio was $0.87{\pm}0.11$ in the upper layer. The limiting nutrient for phytoplankton growth in the study area was identified as nitrogen(N/P ratio=14.6). The nitrate (including nitrite) concentrations were lower in the region mainly affected by NEC than in the region affected by NECC. The study area of low silicate concentrations was also considered to be Si-limiting environment. The remineralization ratios of nutrients were $P/N/-O_2=1/14.6{\pm}1.1/100.4{\pm}8.8(23.44{\leq}Sigma-{\theta}{\leq}26.38)$ in the study area. These ratios suggested remineralization process in the surface layer of divergence zone.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.4
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• pp.340-347
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• 2001

Seasonal variation of the elemental and biochemical composition of the suspended particulate matter (SPM) was investigated in terms of quantity and quality of diets for suspension feeders from July 1999 to August 2000 in two coastal bay systems of Gosung and Kangjin Bays in Korea. No clear patterns in the seasonal variations of SPM concentration were found in these two bay systems. The results indicated that the seasonal variation of SPM could not be considered the variation of food available to suspension-feeders. The simultaneous peaks in chlorophyll a and biochemical components in summer indicated that the quantity of the particulate organic matter primarily depended on phytoplankton productivity. However, no correlation between chlorophyll a and biochemical components [particulate protein (PPr), carbohydrate (PCHO) and lipid] were found, indicating that other processes might also contribute to the particulate organic matter in the period when the phytoplankton biomass was low. High C: Chl a and C:N, and carbohydrate peaks during the autumn to spring period suggested that resuspension of surface sediments was a probable process to supply the particulate organic matter. The food material, represented by summing up the total quantity of three biochemical components, was highest in spring with minor peaks during the period from autumn to the next spring, The food index, calculated as the ratio of food material to total SPM, did not generally exceed $6\%$ with short peaks during the year. Therefore, nutritional quality of SPM in the bays are relatively poor than in other more productive coastal waters in the world. Our results confirm that the measurement of a single chemical variable cannot describe fully the nutritive value of the seston available to suspension-feeders as previously proposed, and the biochemical composition of SPM can provide effective information on its origin and nutritive Quality.

• Korean Journal of Ecology and Environment
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• v.39 no.1 s.115
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• pp.73-84
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• 2006

The objective of this study was to analyze long-term temporal trends of water chemistry and spatial heterogeneity for 10 sampling sites of the Yeongsan River watershed using water quality dataset during 1995 to 2004 (obtained from the Ministry of Environment, Korea). The water quality, based on multi-parameters of biological oxygen demand (BOD), chemical oxygen demand (COD), conductivity, dissolved oxygen (Do), total phosphorus (TP), total nitrogen (TN) and total suspended solids (TSS), largely varied depending on the sampling sites, seasons and years. Largest seasonal variabilities in most parameters occurred during the two months of July to August and these were closely associated with large spate of summmer monsoon rain. Conductivity, used as a key indicator for a ionic dilution during rainy season, and nutrients of TN and TP had an inverse function of precipitation (absolute r values> 0.32, P< 0.01, n= 119), whereas BOD and COD had no significant relations(P> 0.05, n= 119) with rainfall. Minimum values in conductivity, TN, and TP were observed during the summer monsoon, indicating an ionic and nutrient dilution of river water by the rainwater. In contrast, major inputs of total suspended solids (TSS) occurred during the period of summer monsoon. BOD values varied with seasons and the values was closely associated (r=0.592: P< 0.01) with COD, while variations of TN were had high correlations (r=0.529 : P< 0.01) with TP. Seasonal fluctuations of DO showed that maximum values were in the cold winter season and minimum values were in the summer seasons, indicating an inverse relation with water temperature. The spatial trend analyses of TP, TN, BOD, COD and TSS, except for conductivity, showed that the values were greater in the mid-river reach than in the headwater and down-river reaches. Conductivity was greater in the down-river sites than any other sites. Overall data of BOD, COD, and nutrients (TN, TP) showed that water quality was worst in the Site 4, compared to those of others sites. This was due to continuous effluents from the wastewater treatment plants within the urban area of Gwangju city. Based on the overall dataset, efficient water quality management is required in the urban area for better water quality.