• Economic and Environmental Geology
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• v.44 no.6
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• pp.475-483
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• 2011

Quantitative estimate of manganese nodules based on the operation of a free fall grab (FFG) needs to be corrected because of its less retrieval ability. Previously, the correction parameter of the nodule abundance collected by FFG was calculated based on the image analysis of the photos of bottom sediment in the northern sector of the nodule exploration area of Korea in the NE equatorial Pacific. However, nodules in the southern sector are commonly covered by sediment, which may prevent the use of the correction parameter estimated by photographic techniques. In this study, we attempted dual nodule sampling at the same location by different equipments (i.e. box corer (BC) and FFG) to examine the previous correction parameter of nodule abundance for FFG operation. During the exploration cruises in 2007 to 2009, Mn-nodules were collected from 40 stations both by BC and FFG in the southern sector. The correlation analysis between BC and FFG operations revealed that the BC collected nodules 1.43 times larger than FFG. Our result suggests that the correction parameter of 1.43 can be applied for collection of FFG data to estimate Mn-nodule distribution in the southern sector. The obtained parameter is similar to the previous parameter (1.42~1.45) calculated by the image analysis method, indicating an usefulness of new correction parameter suggested by this study.

• Economic and Environmental Geology
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• v.45 no.5
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• pp.477-486
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• 2012

High-resolution bathymetry and physico-chemical properties of manganese nodules were explored to identify the relationship between morphological features and nodule occurrences in the KR1, one of the Korean contract nodule fields located in the NE Pacific. The high-resolution seabed mapping showed that the southwestern sector of the KR1 (KR1-1) was relatively deeper than the northeastern sector (KR1-2) which is occupied by small-scale seamounts. In terms of nodule occurrence, manganese nodules in the KR1-1 were comparatively larger (2-4 cm) with rough surface (t-type) and discoidal shapes (D-type), while those in the KR1-2 were generally small (<2 cm) with smooth surface (s-type) and irregular shapes (I-type). In addition, the nodules in the KR1-1 had higher contents of Cu, Mn and Ni. Such connections of water depths to nodule appearances and metal contents are commonly observed in the Pacific nodule fields. On the other hand, the nodules in the KR1-2 tend to be controled by morphological features. The seamounts in the KR1-2 might continuously provide rock fragments as new nuclei of manganese nodules. As a result, the nodules could not grow over than 2 cm and showed the shapes of a newbie (i.e., smooth surface and irregular shapes). As a result, our observations indicate that occurrence features of manganese nodules could be subjected to water depths and seabed morphology simultaneously.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.168-177
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• 2008

Trafficablility of a miner and potential environmental impacts due to mining activities should be considered in the selection of a commercial manganese nodule mining site. These two factors can be evaluated comparatively with physical properties and shear strength of sea-bed sediments. For the qualitative comparison of potential minig sites in terms of these two factors, physical properties such as water contents, void ratios, porosities, and grain densities, and shear strengths of surface sediments were determined for the three potential manganese nodule mining sites(KR1, KR2, and KR5) in the Korean manganese nodule contract area, northeast Pacific. For the study, sediment samples were collected from 107 stations from 2004 to 2006. The physical properties of surface sediments showed more significant differences between northern(KR1, KR2) and southern(KR5) blocks than between northern blocks(KR1 vs. KR2). Water content, void ratio, and porosity of sediments from KR5 were relatively higher than those from KR1 and KR2. Grain density of sediments from KR5 was relatively lower than those from KR1 and KR2. Shear strengths of the top 10cm sediments were higher in KR1 and KR2, whereas those of the deeper part were highest in KR5 block. Generally, sediments of high water contents are less suspendible than those of the low water contents by benthic disturbances, thus less disturbance is expected in the sediments of high water content by mining activities. In terms of trafficability, the shear strength of sediment below 10 cm deep is more important than shallower part because miner will disturb at least top 10 cm interval of the surface sediments. Base on these results, we conclude that KR5 area will be the best site for commercial mining among three investigated sites in this study.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.13 no.3
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• pp.200-209
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• 2008

Particle fluxes were measured with a time-series sediment trap from July 2003 to June 2005 at the St. KOMO(KOMO; Korea Deep-Sea Environmental Study Long-Term Monitoring Station, $10^{\circ}30'N,\;131^{\circ}20'W$) in the northeastern Pacific. Total mass fluxes at a depth of 4,960 m showed distinct seasonal variations with high values in the winter(December-February) and spring(March-May) and low values in the summer(June-August) and fall(September-November). Biogenic origin fluxes also displayed distinct seasonal variations similar to total mass fluxes. Particularly, calcium carbonate fluxes in winter and spring were more than two times greater than those in summer and fall. The prominent seasonal variations of total mass and biogenic fluxes were closely related with the seasonal changes of primary production in the surface waters; in winter and spring, primary production increased due to the enhanced supply of nutrients below the surface mixed layer by strong wind and less stratification, whereas it decreased as a result of the less supply of nutrient by reduced wind speed and strong stratification in summer and fall. The seasonal variations of total mass and biogenic fluxes in this study were higher than the differences of total mass and biogenic fluxes caused by the environmental changes such as El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ events in the previous studies. In order to understand the effects of El $Ni\tilde{n}o$ and La $Ni\tilde{n}a$ on the particle flux, therefore, the seasonal variation of particle flux in the northeastern equatorial Pacific needs to be well defined.