• Journal of Korean Society of Environmental Engineers
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• v.22 no.11
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• pp.2025-2036
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• 2000

A physicochemical process called ultra rapid coagulation(URC) was applied as a pilot scale to recover eutrophicated lake water at Inkyung Lake located on-campus in Inha university. The URC was uniquely designed to completely remove the presence of phosphorus up to 95%, which in turn leading to lessen the level of eutrophication of lake. For a pilot test of period, the lake was restored showing Carlson's Trophic State Index(TSI) of mesotrophic state which accounts for the reduction of total phosphorus and chlorophyll-a down to approximately 55 from 70 and 73, respectively. A residual presence of aluminum and additional coagulants in the effluent was tested for their potential effects on Photobacterium phosphoreum. The effect concentration ($EC_{50}$-15 min) observed in the effluent revealed that the bioactivity of Photobacterium phosphoreum was not influenced by the residual presence of coagulants. After the pilot test of period, the lake was consequently restored as a mesotrophic state in obtaining the second grade of lake water quality. The URC may be further applied for restoration of greater scale of lake in eutrophication.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.533-537
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• 2017

우리나라는 2012년에 4대강 사업을 통하여 수자원확보를 통한 가뭄대응전략으로 16개의 대형보가 건설되었고 영산강에는 승촌보와 죽산보 2개의 보가 건설되었다. 보의 건설로 흐름은 급격히 감소하여 정체구역의 수역이 확장되면서 여름에서 초가을까지 녹조현상은 매년 지속적으로 발생하고 있으며, 최근 국민들은 안전한 농산물의 안정적인 생산에 요구가 점증함에 따라 농업용수질 오염문제가 범국가적 문제로 대두되고 있고, 그 중요도 및 심각성이 점차 커져가고 있다(한강유역환경청, 2007). 많은 량의 물을 농업용수로 사용하고 있는 영산강의 녹조현상 및 수질개선이 절실하다. 따라서 본 연구에서는 영산강의 승촌보와 죽산보의 건설과 수질오염총량관리제의 시행에 따른 부영양화특성의 변화를 파악하기 위하여 환경부, 국립환경과학원(2006)에서 개발한 한국형 부영양화지수(TSIko) 평가법을 이용하여 영산강유역의 12개 주요지점에 대하여 수집한 자료를 봄(3월~5월), 여름(6월~8월), 가을(9월~11월), 겨울(12월~2월)로 분리하고, 다시 4대강 사업의 영향을 검토하기 위하여 2013년을 전후하여 분리하였으며, 계절별 수질인자 COD, T-P, Chl-a 값을 이용하여 계절별 $TSI_{Ko}$를 산정하여 영양상태를 4개의 등급으로 구분하여 부영양화특성을 파악하였다.

• Korean Journal of Ecology and Environment
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• v.56 no.1
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• pp.83-93
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• 2023

This study compares the abundance and community structure of zooplankton organisms from pelagic regions, and considers particularly the trophic levels vs. zooplankton abundances and biomass. Zooplankton samples were collected three times from May to November 2022, at 30 temperate lakes and reservoirs, which belong to four different river basins. The total zooplankton abundance, biomass and species index were showed considerable spatial variation. The spatial pattern of rotifer abundance was similar to that of total zooplankton abundance, while there were not showed similar patterns of zooplankton biomass (㎍ L^-1) in lentic ecosystems. The rotifer strongly dominated the zooplankton assemblage in smaller lentic system than that of larger. A total of 130 species of zooplankton were identified (83 rotifers, 34 cladocerans and 13 copepods). The total average of zooplankton abundance and biomass were 213.7±342.3 Ind. L^-1 (n=129) and 1382.8±1850.4 ㎍ L^-1, respectively. Total and average of zooplankton abundance were usually dominated by the rotifers (>56.9%), while those of zooplankton biomass were dominated by the cladocerans and copepods (>73.6%) in lentic ecosystems. Considering the Trophic State Index (TSI), the factors of zooplankton abundance and biomass were included in between meso- and eutrophic states(27 lakes, 90% of all). The mean abundance and biomass of zooplankton in eutrophic systems were higher than that of meso- and hypertrophic systems. From this result, we suggest that management strategy for the lentic ecosystem water environment has to be focused more on small-sized lakes and reservoirs, in terms of zooplankton assemblages.

• Korean Journal of Environmental Agriculture
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• v.41 no.3
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• pp.177-184
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• 2022

BACKGROUND: Recently, the inflow of nonpoint pollutants into rivers caused by rapid urban and industrialization promotes the proliferation of algae, which causes eutrophication of rivers. This study was conducted to evaluate the seasonal variation of water quality characteristics and cryptomonads growth in the Oncheon River. METHODS AND RESULTS: The water quality and distribution characteristics of cryptomonads in the Oncheon River were investigated monthly for 12 months from January 2021. The cell number of cryptomonads was intensively developed in January-April, and it decreased sharply in the summer with heavy rainfall. In particular, cryptomonads moved to the downstream side of the river depending on the time, and as a result, significant differences were shown for each investigation point. The Korean trophic state index (Tsi_KO) in Oncheon River was classified as eutrophy all year round, indicating that cryptomonads can grow year-round. Distribution characteristics of cryptomonads in Oncheon River showed high correlations with DO (r=0.678), BOD (r=0.826) and chlorophyll-a (r=0.613) in water. CONCLUSION(S): In order to reduce cryptomonads in the Oncheon River, it is judged that a complex countermeasure considering the residence time, insolation and precipitation along with water quality factors is required.

• Journal of Korean Society on Water Environment
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• v.33 no.3
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• pp.341-347
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• 2017

From 2014 to 2016 water quality survey results according to the location and depth of Youngrang Lake are as follows: Distribution of dissolved oxygen in the water depth was investigated by the middle section and the downstream 1st, 3rd, 5th, when investigating bottem 1m interval anoxic layer. In organic matter and nutrient concentration distribution COD upstream 2.8 mg/L, middle section 4.2 mg/L downstream 4.1 mg/L, more than two times higher in bottem layer and TP concentrations showed a similar trend with COD, upstream of 0.047 mg/L, middle section was 0.051 mg/L, downstream of 0.059 mg/L. There was a difference in salinity every survey period the average salinity is lowest with 28.5‰ when the second survey. And the highest with 32.1‰ in the fourth investigation. Korean trophic state index($TSI_{KO}$) were showed eutrophic conditions in the middle section and downstream else showed mesotrophic state in the entire period. In order to evaluate the cause of water pollution Youngrang lake, regression analysis of the relationship between salinity and DO, COD, TN, TP, Chl-a results, $R^2$ is from 0.63 to 0.95 Youngrang lake water quality was found to have a close relationship with salinity due to inflow of seawater. As a result, in order to improve the quality of Youngrang lake efficient incorporation of the amount of water through the seawater influent as it is considered the key.

• Korean Journal of Ecology and Environment
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• v.50 no.1
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• pp.169-185
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• 2017

Physicochemical properties of water quality were analyzed to understand the long-term variations in Lake Youngrang from 1998 to 2015. Nonparametric statistical methods were applied to deduct correlation among water quality parameters and water quality trend. In total observations(N=64), the Secchi depth (SD) transparency showed significant positive correlation with salinity (r=0.458) and highly significant negative correlation with chlorophyll-a (r= -0.649) for p<0.0001 in two-tailed test of Spearman's rank correlation. Significant negative correlations of SD were observed with chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN). These correlation patterns were very similar in rainy (N=25) and non-rainy (N=39) periods too. Chlorophyll-a (Chl-a) had significant correlation with COD. Sen's slope test was performed along with Mann-Kendall trend test (significance ${\alpha}=0.05$, two-tailed) to find water quality trend. Positive trends were observed for SD and salinity with Sen's slopes 0.012 and 0.385, respectively (p<0.0001). Negative significant trends were observed for total nitrogen (TN) and Chl-a with Sen's slopes -0.02 (p<0.0001) and -0.346 (p=0.0010), respectively. Temperature, COD and phosphorus components had no trends. Carlson's trophic state index (TSI) for SD, TP and Chl-a were obtained in the ranges of 46~80, 37~82 and 39~82, respectively. Trophic index values suggest that Lake Youngrang was mesoeutrophic to eutrophic and there could be possibility of anoxia during the summer and dominance of blue-green algae. Excess nutrient inputs from external and internal sources were the causes of eutrophication in this lake. The findings of this study would be helpful to recognize water quality variables to manage the water body.

• Korean Journal of Ecology and Environment
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• v.34 no.3 s.95
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• pp.206-214
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• 2001

Water quality and Pollution state of Lake Chungcho were evaluated during three years from 1998 to 2000. We surveyed physicochemical parameters, and TSI (trophic state index) was calculated using TP, Chl. a, and SD (secchi disc transparency) data of growing season average. Water samples were collected bimonthly except freezing season. During the study period, total annual precipitation in 1998, 1999 and 2000 year was 1,797,1,722 and 1,345 mm, respectively. Salinity and conductivity were high($29.3{\pm}5.5\;ppt$, and $45,105{\pm}7,585\;{\mu}S/cm$) then other lagoons in the Eastern Coast of Korea. Chemocline was formed by salinity at $0.5{\sim}1.5\;m$ water depth. As a result of this, DO concentration of hypolimnion was below $3.0\;mgO_2/L$. Especially, when intense chemocline was formed, temperature of hypolimnion was higher than epilimnion. Secchi disc transparency, chlorophyll a, and COD were $1.8{\pm}0.3\;m$, $15.7{\pm}20.7\;mg/m^3$, and $3.1{\pm}0.8\;mgO_2/L$, respectively. Most of TN/TP ratios below 20, but concentration of TN and TP was high. Values of TSI ranged between 59 and 77, indicating a eutrophic condition in this system.

• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.161-171
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• 2003

The present study evaluated water quality variation, limiting nutrient, and sediment of a shallow eutrophic lake (Lake Ilgam) in the metropolitan area from 2000 to 2002. According to annual mean chl.a ($77.2{\pm}36.6\;{\mu}g/l) and TP ($66.6{\pm}20.5\;{\mu}g/l) concentration and trophic state index (>60), Lake llgam was in very eutrophic status. Both inorganic nitrogen ($NH_3-N$ and $NH_3-N$) and phosphorus (SRP) concentrations in the water column increased during winter and spring, but decreased during summer followed by the phytoplankton development. Evidence for phosphorus and nitrogen as being the potential limiting nutrients for phytoplankton growth was supported by the ratio of DIN/DIP (by mass) (${\sim}$835.8), TSI derivations analysis, and algal growth potential bioassay. Based on the results of TSI derivations, strong nutrient limitation by both N and P occurred from September to November when P content in sediment (114.6 mg P/kg) was relatively low compared with the summer. Sediment contained a large amount of nitrogen (TKN: 4,452${\pm}$283.0mg N/kg dry sediment). Phosphorus content in sediment (TP: 313${\pm}$155 mg P/kg) was relatively low with temporal change. P release rate (0.29${\pm}$0.02 mg $m^{-2}$ $day^{-1}$) was high under the aerobic condition at pH 9. These results indicate that the sediment could play an important role as a source of a limiting nutrient, and temporal change of P content in the sediment is closely related with water quality, especially algal biomass change in Lake llgam.

• Journal of Environmental Health Sciences
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• v.44 no.4
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• pp.315-322
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• 2018

Objectives: A lake is a place used by many people, and compared to rivers it is easy for them to become polluted. The water quality in lakes and reservoirs has been worsening recently. The purpose of this study is to evaluate the water pollution characteristics of major lakes in northern Gyeonggi-do Province. Methods: Six lakes were selected as major lakes and were evaluated in terms of water pollution characteristics and eutrophication (as defined by results for $COD_{Mn}$, TOC, SS, Chl-a, T-N and T-P) over one year (from December 2016 through November 2017) in northern Gyeonggi-do Province. Results: The annual average $COD_{Mn}$ was found to be 3.1 mg/L in Onam, 3.6 mg/L in Sanjeong, 4.7 mg/L in Gisan, 4.8 mg/L in Ilsan, and 6.1 mg/L in Jangja. The results of the Korean trophic state index ($TSI_{KO}$ ) value indicated a eutrophic state ($TSI_{KO}$ 59.0) in Jangja lake. The other lakes were classified as being in a mesotrophic state ($TSI_{KO}$ of 38.1 in Sanjeong, 40.2 in Ilsan, 41.9 in Onam, 46.1 in Gisan, and 47.8 in Gomo). Conclusions: Ilsan Lake's water quality is being well maintained. Sanjeong, Onam, and Gisan are appropriate for use as agricultural water. Jangja lake requires efforts for water quality improvement and to prevent the inflow of non-point pollutant sources.

• Korean Journal of Ecology and Environment
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• v.47 no.3
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• pp.146-159
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• 2014

In this study, we evaluated the temporal changes of water quality in the 90 reservoirs in Korea and the relationships between water quality and their environmental factors in the reservoirs for effective management of reservoirs. The majority of study reservoirs were categorized as the eutrophic state based on Carlson's trophic index. Among 90 reservoirs, more than 55.0% were nutrient-rich based on $TSI_{TP}$ in each month, where more than 50.0% were nutrient-rich based on $TSI_{Chl-a}$ from June to November. Seasonal Mann-Kendall test was used to analyze temporal variation of water quality in the selected 60 reservoirs using monthly data from 2004 to 2008. The results showed that 27 (45.0%) reservoirs showed the improvement of water quality based on TP and Chl-a concentrations, while 14 (23.3%) and 11 (18.3%) reservoirs displayed the degradation of water quality based on TP and Chl-a concentrations, respectively. Meanwhile, a self-organizing map classified the study reservoirs into five groups based on differences of hydrogeomorphology (altitude, catchment area, bank height, lake age, etc.). Physicochemical factors and land use/cover types showed clear differences among groups. Finally, hydrogeomorphology of reservoirs were related to water quality, indicating that the hydrogeomorphological characters strongly affect water quality of reservoirs.