• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.93-101
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• 2022

RC Slab bridges in Korea account for more than 70% of the total bridges for more than 20 years of service. As the number of aging structures increases, the importance of safety diagnosis and maintenance of structures increases. For highway bridges, cracks are a main cause of deck deterioration, which is very closely related to the decrease in bridge durability and service life. In addition, the damage rate of expansion joints and bearings accounts for approximately 73% higher than that of major members. Therefore, this study defined damage scenarios combined with devices damages and deck deterioration. The stress distribution and maximum stress on the deck were then evaluated using design vehicle load and daily temperature gradient for single and combined damage scenarios. Furthermore, this study performed damage-spread analysis and predicted condition ratings according to a deck deterioration model generated from the inspection and diagnosis history data of cracks. The heterogeneous damages combined with the member damages of expansion joints and bearings increased the rate of crack area and damage spread, which accelerated the time to reach the condition rating of C. Therefore, damage to bridge members requires proper and prompt repair and replacement, and otherwise it can cause the damage to bridge deck and the spread of the damage.

• Journal of Environmental Impact Assessment
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• v.32 no.2
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• pp.72-82
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• 2023

The purpose of this study is to estimate the trend of ecosystem water quality regulating services in Odaesan National park of the last five years and the corresponding economic values. Recently the climate change makes increased the value of the water, it is more important to protect the source of the riverthan to purify the contaminated water. To evaluate the water quality regulating services, we calculated the difference between purification and pollution from national park and estimated the quantitative value of the water quality regulating services. As a results, the amount of the value of the water quality regulating services from 2017 to 2021 was increased from approximately BOD 128.21 kg/Day, T-P 12.11 kg/Day to BOD 161.38 kg/Day, T-P 13.24 kg/Day and the economic value also increased from 2,304 million won to 2,817 million won.

• Korean Journal of Ecology and Environment
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• v.41 no.3
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• pp.283-293
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• 2008

The objectives of the study were firstly to provide fundamental data for establishment of total maximum daily load (TMDL) management in Ulsan City, and secondly to make practical application of stream health assessment with tolerance range by each species when physiochemical and fish investigations were carried out together. A total of 44 sites in Taehwa River, Hoiya River, Dong Stream, and Cheongryang Stream were selected to monitor water qualities seasonally and fish investigation was performed in August 2006. Among the parameters of water quality, biological oxygen demand (BOD) and dissolved oxygen (DO) related to respiration, total nitrogen (T-N) and total phosphorus (T-P) related to nutrient and eutrophication, and total suspended solids (TSS) and $NH_4$-N were compared with vertical box plot by 8 dominant species. According to the fish investigation, 12 families 33 species were found including endangered species (Pungitius kaibarae) and introduced species (Lepomis macrochirus, Micropterus salmoides), and appearance rate of Korean endemic species was greater in Taehwa River (29.2%) than others. As the results of tolerance range by species, Zacco koreanus, Rhynchocypris oxycephalus, Iksookimia longicorpa, and Squalidus gracilis majimae had limited low range by water quality parameters indicating preference of good water quality. Whereas, Carassius auratus and Pseudorasbora parva were found downstream and urban-streams which were exposed from frequent inflow of pollutants. It concludes that the results help distinguishing sensitive, intermediate, and tolerant species when we evaluate stream health assessment with fish, and further making practical application for conservation and restoration of aquatic ecosystem.

• Journal of the Korean Society for Marine Environment & Energy
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• v.11 no.2
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• pp.78-85
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• 2008

We estimated the pollutant loads for the last 3 years based on the daily discharge at the Nakdong River dam(barrage) and spatiotemporal characteristics of seawater quality in the Nakdong river estuary to investigate the correlation between the pollutant load inflow rate and seawater quality. The main results from this research are summarized as follows. (1) The total discharge at the Nakdong River dam dam the last 11 years has been $224,576.8{\times}10^6m^3/day$. The discharge figures show that the maximum discharge occurs in August with $52,634.2{\times}10^6 m^3/day$ (23.4% of the year's volume), followed by July and Sep. in that order with 23.1 and 17%, respectively. (2) The pollutant load influx from the Nakdong River dam was composed of 307,591.3COD-kg/day, 128.746.1 TN-kg/day, and 107,625.8 TP-kg/day. (3) The surface temperature in the Nakdong River estuary was about $2.137^{\circ}C$ higher than that of the lower layer. The salinity of the lower layer was 2.209%o higher than that of the ocean surface. The salinity of the ocean surface decreased by up to 19.593%o due to the inflow of the discharge at the Nakdong River dam. (4) DO, COD, TN, and SS concentration levels tended to be higher at the ocean surface than in lower layers, whereas the reverse was true for TP. (5) The water mass at the ocean's surface and in the lower layers during the drought and flood seasons tended to be separated by the difference in densities due to the freshwater inflow.

• Journal of Wetlands Research
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• v.21 no.2
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• pp.163-172
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• 2019

The USLE P factor is a factor that varies depending on how croplands are managed and cultivated. Previous studies tend to overestimate the amount of soil loss because the factor was estimated from the slope of the watershed rather than the estimate of each cultivated land. In addition, the accuracy of estimating the soil loss is decreasing due to the fact that the factor is calculated without considering various conditions of cultivated land defined by Wishmeier and Smith. In order to overcome these problems, the Ministry of Environment (MOE) has proposed to establish the topsoil notification and calculate the P factor according to the cultivation methods (e.g., tillage system, support practice). However, it is required to apply the conditions proposed in the United States to domestic circumstances as it is causing uncertainties. Thus, this study selected the watersheds where soil loss was serious (Haean, Jaun, Banbyeoncheon), measured the actual slopes and slope lengths, and examined the crop, tillage systems, and support practice for each cultivated land. The P factors were recalculated considering the actual conditions of cultivated land and compared to the factors proposed by the previous studies (MOE). As the result of the study, the P factors calculated based on the previous studies were 0.8 ~ 1.0 in three watersheds. On the other hand, it is confirmed that there is a significant difference between the factors notified by MOE and estimated by reflecting the topography and cultivation methods in this study. Therefore, it is considered that the research for developing the cultivation conditions to calculate the P factor suitable for the domestic environment should be continuously carried out.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.503-513
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• 2018

In order to continuous watershed management and improve water quality at Yeong-san river system, we analyzed and evaluated data on the monitoring of small stream in city and county boundaries within the watershed. In-period monitoring is estimated to be more frequent in the second quarter than the first quarter, so it should be considered when evaluating the target water quality by setting the target water quality. A small stream in the Yeong-san river system has higher concentration in the downstream area than the upstream area. As a result of calculating the load of the measuring point, Y.b B3(Pungyeongjeongcheon) and Y.b E1(Sampocheon) were high. The result of correlation analysis by monitoring point in order to evaluate the correlation between BOD and T-P items, BOD was highly correlated with COD and TOC, and was affected by emission of pollutants related to organic matter. T-P was highly correlated with SS and COD, and was affected by rainfall. This study will provide basic data and direction for designing efficient and scientific method for water quality management by analyzing accumulated water quality data by conducting long-term monitoring.