• Ecology and Resilient Infrastructure
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• v.6 no.1
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• pp.23-33
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• 2019

Naeseong Stream is a sand-bed river that flows through the northern area of Gyeongbuk province. It is characterized by dynamic sandy bedforms developed in response to the seasonal hydrological fluctuation and by its unique riverine landscape called "white river." However, changes including construction of Yeongju Dam from 2010 and the extensive vegetation establishment around 2015 occurred along the Naeseong Stream. This paper aims to analyze climate, hydrology, and water quality as factors and to examine the possibility of channel changes accordingly. The second least precipitation during the last 60 years happened in 2015, which led to the lowest peak discharge in 50 years. The sediment characteristics of Naeseong Stream were not significantly different along the upstream and downstream reaches, but it was confirmed that annual minimum water level of the stream decreased continuously regardless of the dam construction. This suggests that intermittent drought and change in water quality are likely to provide favorable conditions for riparian vegetation establishment and the resulting physical changes have affected riverbed degradation. Therefore, it is necessary to conduct diversified monitoring in connection with river vegetation change in order to analyze the causes of river changes.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.930-936
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• 2010

There is very important to investigate long-term trend of soil chemical properties and quality index for sustainable agriculture and production of agricultural safety products. Monitoring on soil chemical properties in paddy soils was conducted as one cycle with 4 years from 1999 to 2007. Paddy soil samples were taken from 4,007, 1,970, 2,070 sites in 1999, 2003 and 2007, respectively. With these data, soil quality index (SQI) was evaluated by method that Yoon et al suggested in 2004. Chemical properties of paddy soils were 5.8 for pH, 24 g $kg^{-1}$ for organic matter, 132 mg $kg^{-1}$ for available phosphate, 0.29 cmol_c\; kg-1 for exchangeable potassium, 4.7 $cmol_c\;kg^{-1}$ for exchangeable calcium, 1.3 $cmol_c\;kg^{-1}$ for exchangeable magnesium and 126 mg $kg^{-1}$ for available silicate in 2007. Long-term change was shown that pH has increased gradually whereas exchangeable potassium has decreased. However, reasonably large changes were found. Exchangeable calcium and available silicate level in 1999 was 4.0 $cmol_c\;kg^{-1}$, 86 mg $kg^{-1}$, but had risen to 4.7 $cmol_c\;kg^{-1}$, 126 mg $kg^{-1}$ in 2007, respectively. The change of paddy soils quality index was increased gradually and increasement of silicate quality index was higher than other quality indicators.

• Korean Journal of Environmental Biology
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• v.37 no.4
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• pp.600-606
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• 2019

The study site was the camping area in the Hwarang Amusement Park in Danwon-gu, Ansan-si. Study activities were conducted three times a week from July 20, 2018, to August 1, 2018. A control site, natural enemy site, and Bti(Bacillus thuringiensis israelensis) site were selected. The analyses included habitat environment and species composition analyses, community analysis, correlation analysis, and similarity analysis. The water quality analysis found no significant difference in water quality over the study period (p>0.05). A total of 4,818 individuals, 38 species, 22 families, and 11 orders were observed during the study period. The natural enemy site observed during the study period had a similar species composition as the control site. The Bti site differed from other sites by the low number of species and individuals present. According to the community analysis, the natural enemy site was a stable community and the Bti site was an unstable community during the study period. Diptera showed negative associations with temperature and water temperature and mosquito larvae showed significant correlations with temperature and water temperature. The similarity analysis showed that the control site and the natural enemy site were 61.11-73.68% and the Bti site showed 30.77-56.00% similarity.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1118-1123
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• 2011

The changes of available silicate (Avail. $SiO_2$) contents in paddy soils (sandy loam) were assessed from data of the 41 years fertilization plots in which the continuous rice cropping experiment started in 1954 at the National Academy of Agricultural Science. The treatments were no fertilization (O), inorganic fertilization (NPK), inorganic fertilizer plus rice straw compost (NPK+C), inorganic fertilizer plus silicate fertilizer as a soil amendment (NPK+S), inorganic fertilizer plus rice straw compost and silicate fertilizer (NPK+CS) and inorganic fertilizer plus rice straw compost, silicate fertilizer and lime (NPK+CSL). Available silicate contents in NPK+S, NPK+CS and NPK in surface soil reached at the highest content ($255{\sim}330mg\;kg^{-1}$) after 41 years and then levelled off. Available silicate contents in subsurface soil (25~30 cm) were higher in NPK+C and NPK+S treatments than those in other treatments. Continuous application of silicate fertilizer affected significantly on the levels of available silicate in surface and subsurface soils. Silicate uptake of top rice was more increased by 98% in NPK+CS and NPK+CSL over NPK. Grain yield also increased by 37~47% in NPK+CS and NPK+CSL as compared to NPK. The combined applications of inorganic fertilizers with silicate as a soil amendment are recommended as the best fertilization practice for fertilizer use efficiency, enhancement of soil fertility status in the continuous rice cropping system in Korea.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.3
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• pp.289-295
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• 2010

Monitoring of the heavy metals at paddy rice agriculture is very important for environmental agriculture. A study was carried out of heavy metal concentrations in 260 paddy soil samples every four years from 1999 to 2007 in Gyeongnam Province. Heavy metals such as Cd, Cr, Cu, Ni, Pb, Zn, and As in paddy soils were analyzed. Average concentrations of heavy metal were Cd 0.426 (ranged 0.003-1.379) mg $kg^{-1}$ for Cd, 1.189 (0.003-3.264) mg $kg^{-1}$, for Cr, 9.68 (0.05-22.38) mg $kg^{-1}$ for Cu, 2.64 (0.01-7.36) mg $kg^{-1}$ for Ni, 23.7 (0.7-54.1) mg $kg^{-1}$ for Pb, 20.8 (0.7-131.2) mg $kg^{-1}$ for Zn, and 1.054 (0.001-2.110) mg $kg^{-1}$ for As, respectively. Long-term changes of heavy metals were showed that Cd, Ni, and Zn were significantly increased whereas Cr, Cu, and As were significantly decreased. Principle component analysis (PCA) of heavy metals in paddy soils was obtained with eigenvalues > 1 summing 34.3% of variance for PC1, 17.5% of variance for PC2, and 51.8% of the total variance in soil heavy metals.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.22 no.4
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• pp.187-198
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• 2017

Dissolved and particulate organic carbon concentrations and fluxes were measured and estimated for the Yeongsan River during 2006~2015. The dissolved organic carbon (DOC) concentrations ranged from 2.49 to $4.39mg{\cdot}C/L$ with a variance of 30.1% (${\sigma}_x/\bar{x}$), and showed a simple correlation to algal bloom and precipitation. The particulate organic carbon (POC) concentrations had gradually decreased from 6.68 to $0.19mg{\cdot}C/L$ for 10 years, and changed definitely with weir construction in 2011. Based on the relationships between POC and suspended particulate matters and between POC and chlorophyll-a, we found out that the distinct variation of the origin and composition of POC was caused by stagnation and screening effect of the dammed river. The total organic carbon (TOC) concentrations dropped to 52.3% (from 8.26 to $3.94mg{\cdot}C/L$) as the POC concentrations diminished to more than 94.8% after weir construction, in which the DOC forms up to 90.9%. The fluxes of TOC, based on the relationship between the annual TOC concentration and the discharge of Yeongsan dike sluice, were $2.56{\sim}19.41{\times}10^9g{\cdot}C/yr$, and showed a great deal of variability in 2011. Since then the TOC flux dropped to $5.40{\times}10^9$ (2011~2015) from $14.54{\times}10^9g{\cdot}C/yr$ (2006~2010). These results suggest that the weirs trapped annually $1.83{\times}10^9g{\cdot}C$ on a river bed, but released in great levels of dissolved organic form at their exits.