• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.33-44
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• 2012

Transparent exopolymer particles (TEP) are formed by aggregation of polysaccharide products excreted by phytoplankton and have sticky character like gel. They play important role in the production of marine snow in water column. To study the distribution pattern of TEP concentration and its role in carbon cycle in the surface ocean, we measured pH, Total alkalinity (TA), and chlorophyll-a in addition to physical characteristics of seawater within the surface water column. TEP concentrations ranged from nearly undetectable values to $338{\mu}g\;Xeq\;l^{-1}$. They were considerably lower than previously reported values from costal sites, but showed similar values observed in other oceanic region during phytoplankton bloom periods. The spatial distribution of TEP concentrations were similar to those of chlorophyll-a, which indicate that the production of TEP were closely related to phytoplankton. Calculated total dissolved inorganic carbon ($TCO_2$) from the pH and TA was normalized to 35 psu of salinity ($NTCO_2$) and showed negative linear relationship with temperature. Biological drawdown of $NTCO_2$ ($NTCO_{2bio}$) was estimated from the difference between theoretical $NTCO_2$ values and observed $NTCO_2$. In the warm region located south of $40^{\circ}N$ along the $132.5^{\circ}N$ meridional lines, $NTCO_{2bio}$ showed negative value and TEP concentrations were high. This suggested that negative $NTCO_{2bio}$ may be attributed to the biological processes. At the stations located between 44 and $46^{\circ}N$, TEP concentrations showed high concentration at the chlorophyll-a maximum layer within the water column while they showed low concentration in the surface layer. Carbon content of TEP constituted about 40% of $NTCO_{2bio}$ at the chlorophylla maximum layer. In this study, we could not observe any positive and negative relationship between TEP concentration and $NTCO_2$ or pH. It is obvious that we should consider the importance of TEP in the biological carbon cycling processes within surface layer.

• The Journal of Engineering Geology
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• v.28 no.1
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• pp.101-115
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• 2018

This study was carried out to evaluate the effects of various filter conditions on unconfined aquifer (alluvial aquifer). We made model test device which has filter layer, pumping well and observation well which consist of sand layer and gravel layer to test. Step drawdown test and long term pumping tests were carried out using the device. The permeability characteristics of each test group were confirmed and the optimal yield was calculated. As a result of comparing the optimal yield of double filter and single filter in sand, dual-filter SD-300 was valued at 216.8 % higher final optimal yield than single-filter SS-300. Comparing the dual filter SD-300 and the single filter SS-100 with a thin filter layer, dual-filter SD-300 was valued at 709.2% higher final optimal yield than single-filter SS-300. As a result of analysis of optimal yield change over time, It was confirmed that the ratio of optimal yield of single filter and dual filter increase over time. In order to evaluate the long-term change in water intake efficiency, we considered the point at which the initial optimal yield was reduced by 50%. The dual filter SD-300 is about 351.1% higher than SS-300, which is the same thickness filter, and about 579.0% higher than SS-100. From these results, Assuming that the point at which the initial quantity of water intake is reduced to 50% is the well life, double filters are expected to increase their lifespan by about 3.5 times over single filters of the same thickness and by about 5.8 times over typical single filter. These results can be used to design wells to river bank filtration or filtered seawater. In addition, it is possible to clarify the effect of the double filter through the comparison with the future field test results.